A suspension bridge is one of the types of bridges in which the Deck(the load bearing portion) is hung below suspension cables on vertical suspenders.
The cables (or ropes or chains) are strung across the river through two tall towers.
Suspension bridges are aesthetic, light, and strong.
Suspension bridges can span distances from 2,000 to 7,000 feet—far longer than any other kind of bridge.
True to its name, a suspension bridge suspends the roadway from huge main cables, which extend from one end of the bridge to the other.
Suspension bridges built over waterways, can be built high, allowing the passage of tall ships unhindered by the bridge.
During construction, temporary central supports do not need to be built, and access to the construction is not required from beneath.
This means busy roadways and waterways do not need to be disrupted.
The added flexibility of suspension bridges allows them to flex under the power of winds and earthquakes
They tend to be the most expensive to build.
Suspension bridges can be unstable in extremely turbulent conditions, with extreme cases requiring temporary closure of the bridge.
When built in soft ground, suspension bridges require extensive and expensive foundation work to combat the effects of the heavy load on foundation towers.
Flexibility can be a disadvantage to suspension bridges, which can flex under heavy, concentrated loads. Suspension bridges are not generally used for regional rail crossings that carry maximum weight loads, causing added stress on the bridge.
The main Parts of a
Suspension Bridge are
Deck
Suspension cable
Suspender
Tower
Floor beams
Backstay
Anchorage Block ( Dead man )
Approach ramp
Suspension bridge has cables suspended between towers.
The towers enable the main cables to be draped over long distances.
The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground.
Most of the weight of the bridge is carried by the cables to the anchorages, which are imbedded in massive concrete blocks.
The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables.
Inside the anchorages, the cables are spread over a large area to evenly distribute the load and to prevent the cables from breaking free.
The vertically suspended cables are known as suspenders.
Vertical suspended cables carry the weight of the deck below, upon which traffic crosses.
The roadway is supported by vertical suspender cables or rods, called hangers.
The main suspension cable in the early nineteenth century was often made from chain or linked bars, but modern bridge cables are made from multiple strands of wire.
The reason is that as spans increased, engineers were unable to lift larger chains into position, whereas wire strand cables can be largely prepared in mid-air from a temporary walkway.
The cables are made of individual steel wires bound tightly together, which is very strong under tension, is an ideal material for cables. A single steel wire, only 0.1 inch thick, can support over half a ton without breaking.
Suspension bridges have caused disasters in the past because of these cables.
As said that in early stages suspension bridges were made using chain links of heavy steel for the main cable.
If only one chain link failed, the whole bridge would collapse, as what happened to the Silver Bridge in 1967, killing 46 people.
Because of these reasons, suspension bridges use bundles of cables in recent time as said earlier. If one or two of the cables fails, the bridge still stays intact.
Three kinds of forces operate on any bridge: the dead load, the live load, and the dynamic load.
Dead load refers to the weight of the bridge itself.
Live load refers to traffic that moves across the bridge.
Dynamic load refers to environmental factors such as sudden gusts of wind and earthquakes
The main forces in a suspension bridge of any type are tension in the cables and compression in the pillars.
The force of compression pushes down on the suspension bridge's deck, but because it is a suspended roadway, the cables transfer the compression to the towers, which dissipate the compression directly into the earth where they are firmly entrenched.
The supporting cables, running between the two anchorages, are the lucky recipients of the tension forces.
The anchorages are also under tension, but since they are held firmly to the earth, the tension they experience is dissipated.
Since almost all the force on the pillars is vertically downwards and they are also stabilized by the main cables, the pillars can be made quite slender.
The weight is transferred by the cables to the towers, which in turn transfer the weight to the ground.
The following opposing forces act on the deck & the suspension cable:
one downward force caused by the load of the roadway.
one force in one part of the cable, pulling up and to the left.
one force in the other part of the cable, pulling up and to the right.
In the modern world, the longest suspension bridge is Japan's Akashi Kaikyo Bridge, which spans 6,432 feet.
Today, wind tunnel testing of bridge designs is mandatory. Lake of this disaster may occur.
So with these specifications we can conclude that in some special conditions Suspension bridges are more reliable than any other.
Showing posts with label OUR PROJECTS. Show all posts
Showing posts with label OUR PROJECTS. Show all posts
Monday, 26 March 2012
Green House Buildings
Green building is the
practice of creating structures
which are environmentally
responsible and
resource-efficient throughout
a building's life.
Green building can also be termed as
Sustainable building or Green architecture.
or factory in the world is still a kind of
steamship, polluting, contaminating, and
depleting the surrounding environment,
and relying on scarce amounts of natural
light and fresh air. People are essentially
working in the dark, and they are often
breathing unhealthful air.
P
O
L
L
U
T
I
O
N
buildings, we can use Green buildings.
Imagine, a building as a kind of tree. It would
purify air, accrue solar income, produce more
energy than it consumes, create shade and
habitat, enrich soil, and change with the seasons.
A building consumes:
natural resources.
Ø 1/4 of all virgin wood
harvested (not including
furniture).
Green buildings are
designed to reduce the
overall impact of the built
environment on human
health and the natural
environment.
Common Objectives
Protecting occupant health and improving employee productivity.
Efficiently using energy, water, and other resources.
Reducing waste, pollution and environmental degradation.
Green buildings with LEED Certification
meet high environmental standards.
Although a building may be designed efficiently, the systems and equipment must be maintained and continually monitored to retain the high level of efficiency.
Reuse and recycling is important to get the most out of our resources and to maintain a sustainable relationship between economics and our environment.
Use green buildings
practice of creating structures
which are environmentally
responsible and
resource-efficient throughout
a building's life.
Green building can also be termed as
Sustainable building or Green architecture.
Today even the most advanced building
or factory in the world is still a kind of
steamship, polluting, contaminating, and
depleting the surrounding environment,
and relying on scarce amounts of natural
light and fresh air. People are essentially
working in the dark, and they are often
breathing unhealthful air.
P
O
L
L
U
T
I
O
N
Instead of using these congested & polluted
buildings, we can use Green buildings.
Imagine, a building as a kind of tree. It would
purify air, accrue solar income, produce more
energy than it consumes, create shade and
habitat, enrich soil, and change with the seasons.
A building consumes:
| Ø | 2/5 of world energy | |
| Ø | production. 1/6 of all water pumped | out |
natural resources.
Ø 1/4 of all virgin wood
harvested (not including
furniture).
Green buildings are
designed to reduce the
overall impact of the built
environment on human
health and the natural
environment.
Common Objectives
Protecting occupant health and improving employee productivity.
Efficiently using energy, water, and other resources.
Reducing waste, pollution and environmental degradation.
Green buildings with LEED Certification
meet high environmental standards.
Although a building may be designed efficiently, the systems and equipment must be maintained and continually monitored to retain the high level of efficiency.
Reuse and recycling is important to get the most out of our resources and to maintain a sustainable relationship between economics and our environment.
Use green buildings
NAM ROAD PROJECT
1. Expansion of highways from 2 lanes – 4 lanes
Highways: National Highways are the main highways running through the length and breadth of the Indian union, connecting ports , foreign highways and capitals of states and including roads of strategic and military value. They constitute the frame on the which entire road communication system of the Country is based.
Types of Highways:
1)National Highways: National Highways are the main highways running through the length and breadth of the Indian union
2)State High ways: State High ways are the other maintain trunk are arterial roads of a state, connecting up with national head quarters and important cities within the state.
3)District Roads: District Roads are the roads traversing each district of the serving area of production and markets and connecting this with each other are with national and state highways or railway or important navigational routes.
4)Village Roads: Village Roads are roads connecting villages of groups of villages with each other.
In India in most of the Metro politan cities and in other cities roads are two way lanes by which traffic problems are High.Number of vehicles are increasing day by day, two way lanes are not having space for all the vehicles.Govt. is trying to expand the the two way lanes to four way lanes.
In india vehicle has to travel in left side only.Roads are divided into columns as Twoway lanes and four way lanes.Road dividers divides the Lanes into parts as per the Road
Two way lanes are the roads in which road is divided into two columns . only one heavy vehicle can go in one column of the road. Third heavy vehicle cannot fit properly in the two way lanes.
Fig.No.1.1
Four way lanes are the roads in which road is divided into Four columns. Left side of divider having two columns in which two heavy vehicles can go in same direction same with right side of the divider.only two heavy vehicle can go in one column of the road.
To reduce the traffic and for the convenience, Govt. is expanding the roads and highways as two way lanes into four way lanes.
For the transportation of vehicles national Highways now expanding as four way lanes.
Extension of Two way lanes to Four way lanes.
The design and construction of the road in embankment and in cuttings shall be carried out in accordance with Section 300 of MORTH Specifications and the requirements, and standards and specifications given in this Section. This Section also covers specifications for subgrade and earthen shoulders.
Efforts should be made to remove the inherent deficiencies in plan and profile of the existing road. The final centre line of the road and the road levels shall be fixed duly considering all the relevant factors covering structural soundness, safety and functional requirements as per relevant IRC Codes and provisions of this Manual.
The existing road embankment shall be widened/ modified to the specified cross-sectional details.
Materials
Materials and Physical Requirements: All materials to be used in works shall be in conformity with the requirements laid
down for relevant item in IRC/MORTH Specifications unless otherwise specified
in this Section. If the Concessionaire proposes to use any material, which is not
covered in IRC/MORTH Specifications, it shall conform to relevant Indian
Standards, if there are any, or to the International Standards. Proprietary products
proposed to be used shall be proven by use in comparable international road and
bridge projects, and shall be supported with authenticated licensing arrangement
with the manufacturer.
The Concessionaire shall identify the proposed sources of materials and submit
the proposal prior to delivery. If it is found that proposed sources of supply do not
produce uniform and satisfactory products at any time during execution, the
Concessionaire shall procure acceptable materials conforming to the specifications
from other sources.
Structural Concrete: The Concrete for use in structures shall conform to the provisions in Clauses 302.6 to 302.9 of IRC:21 and Section 1700 of MORTH Specifications. Wherever High Performance Concrete (HPC) is proposed to be used, the same shall conform to the provisions of IRC:SP:70. Sampling and testing of concrete shall be as per Clause 302.10 of IRC:21.
Acceptance criteria for concrete shall conform to Clause 302.11 of IRC:21.
Cement
Any type of cement specified in IRC:21 may be used for the works subject to limitations,if any, specified therein.
Coarse Aggregates
Before commencement of the works, at least three samples, in accordance with the procedure laid down in IS:2430, shall be taken for each quarry source to ascertain the quality, suitability and fitness of the available material for use in the works. Fresh tests shall be conducted in case there is any change in the source or the type of rock being quarried. The proposal, along with a copy of test reports, shall be submitted
Sand/Fine Aggregates
(i) All fine aggregates shall conform to IS:383 and tests for conformity shall be carried out as per IS:2386 (Part I to VIII). The fineness modulus of fine aggregates shall be between 2.0 and 3.5.
(ii) Before the commencement of the works, at least three samples as per IS:2430 shall be taken for each quarry source to ascertain the quality, suitability and fitness of the available material for use in the works and the proposal along with a copy of test reports shall be submitted to the IE for review and comments, if any.
(iii) Fine aggregates having positive alkali-silica reaction shall not be used.
Water
(i) Water for use in the works for mixing and curing of concrete shall be in conformity with Clause 302.4 of IRC:21.
(ii) Water from each source shall be tested before the start of works and thereafter
every three months and after each monsoon till the completion of the works andthe proposal along with a copy of test reports shall be submitted to the IE for
review and comments, if any.
Chemical Admixtures
The following guidelines shall apply in selection and use of admixtures:
(i) Chemical admixtures shall comply with IS:9103 and meet the requirements
stipulated in clause 5.5 of IS:456.
(ii) Admixtures generating hydrogen or nitrogen or containing nitrates, sulphides, sulphates, or any other material liable to affect the reinforcement/embedments or concrete shall not be used.
(iii) Compatibility of admixture with the cement being used shall be tested before actual use in the works. The test shall be repeated in case of change of type or grade or source of cement.
Steel
Steel for Prestressing
In addition to the requirement mentioned in Clause 1009.2 of MORTH Specifications, the steel for prestressing shall satisfy following conditions:
Uncoated stress relieved low relaxation steel conforming to IS:14268.
(ii) Prestressing steel shall be subjected to acceptance tests in respect of modulus of elasticity, relaxation loss at 1000 hrs, minimum ultimate tensile strength, stressstrain curve etc. prior to actual use on works as per guidelines contained in BS:4447. The modulus of elasticity value, as per acceptance tests, shall conform to the design value, which shall be within a range not more than 5 per cent between the maximum and the minimum.
Bitumen
Bitumen shall be paving bitumen of viscosity grade complying with Indian Standard Specifications for “Paving bitumen” IS:73:2006 of grade appropriate for the traffic and climatic conditions of the Project Highway. The heavily trafficked roads in hot areas may find harder grade bitumen more appropriate while pavements in mountainous regions subject to sub-zero temperatures during winter months carrying relatively lower traffic loads and subject to the phenomenon of “Frost Heave” may find less viscous bitumen resistant to fatigue and cold cracking more appropriate.
The material to be used in sub grade shall satisfy the design California Bearing Ratio (CBR) at the specified density and moisture content.. Taking into account slope stability, bearing capacity, consolidation, settlement and safety considerations based on geotechnical and investigation data. Where the embankment is to be supported on a weak stratum, appropriate remedial/ground improvement measures shall be taken.
Side slopes shall not be steeper than 2H:1V unless soil is retained by suitable soil retaining structures. The side slopes shall be protected against erosion by providing a suitable vegetative cover, kerb channel, chute, stone/cement concrete block pitching or any other suitable protection measures depending on the height of the embankment and susceptibility of soil to erosion. Drainage arrangement shall be provided as per Section 6 of this Manual.
Soil investigations and tests in accordance with the requirements specified in IRC:
SP:19 and shall be reported in the Proforma given in Table 1 of IRC:SP:19. In
addition to this, all tests as per the requirements of MORTH Specifications shall
be reported.
To assess the likely compresive strength of concrete by using rebound hammer as per IS: 13311 (Part 2) - 1992.The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes. When the plunger of the
rebound hammer is pressed against the surface of the concrete, the spring-controlled mass rebounds and the extent of such a rebound depends upon the surface hardness of the concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound value is read from a graduated scale and is designated as the
rebound number or rebound index. The compressive strength can be read directly from the graph provided on the body of the hammer.
Along the alignment of the road, where unstable strata, soft material or poor subsoil conditions have been met with at the foundation level, the soil profile shall be drawn after determining through borings, the type of soil at different levels. The borings shall be at maximum interval of 100 m to a depth of 2 m or more below the existing ground as necessary. In the case of high embankments, the borings shall be taken down to a depth equal to twice the height of the embankment.
(f) Any particular construction problems of the area or other important features.
(g) Geotechnical properties of pond ash, covering parameters specified in Table 1 of IRC: SP: 58 and Optimum Moisture Content (OMC) – dry density relationship for heavy compaction. This information shall be furnished, in case pond ash is used in embankment construction.
Designing
GEOMETRIC DESIGN AND GENERAL FEATURES
General
(i) This section lays down the standards for geometric design and general features for four-lane divided carriageway.
(ii) (a) In built-up areas, 6-lane divided carriageway along with service roads shall be provided as part of 4-laning of the Project Highway. Such stretches where the requirement of 6-laning is dispensed with and only 4-laning with or
without service road and footpath is to be provided will be as indicated in
Schedule-B of the Concession Agreement.
(b) Where there is constraint of ROW width, the Authority may specify
construction of a bypass. The alignment of the bypasses shall be as specified
in Schedule-B and in conformity with the site earmarked in Schedule-A of
the Concession Agreement.
(iii) The geometric design of the Project Highway shall conform to the standards set out in this section as a minimum.
(iv) As far as possible, uniformity of design standards shall be maintained throughout the length of the Project Highway. In case of any change, it shall be effected in a gradual manner.
(v) Where the existing road geometrics are deficient with respect to minimum
requirements and its improvements to the prescribed standards is not feasible due to any constraint in acquisition of additional land, such stretches shall be as specified
in Schedule-B of the Concession Agreement.
(vi) Existing horizontal curves, which are found deficient in radius, layout, transition lengths or super-elevation shall be corrected to the standards specified in this section.
(vii) Any deficiencies in the vertical profile in respect of grades, layout of vertical curves and sight distance shall be corrected to meet the minimum requirements specified in this section.
Pavement Design
The design and construction of new pavement sections, and of strengthening measures(overlay) for the existing pavement shall be carried out in accordance with the criteria,standards and specifications given in this section. Where alternative specifications or materials are proposed to bring in innovation in design etc The design of new pavement sections or strengthening of existing pavements shall take into account all relevant factors for assuring reliable performance and shall also satisfy the specified minimum performance requirements.
The Concessionaire shall undertake the necessary soil, material and pavement
investigations and traffic volume and axle load studies in accordance with the good industry practice for preparing detailed designs.
The materials, mixes and construction practice shall meet the requirements prescribed in the MORTH/IRC Specifications.
Where problematic conditions such as expansive soils, swamps or marshes, flooding,poor drainage, frost susceptible areas etc. are found to exist, adequate measures shall be adopted to deal with such site conditions.
Design Traffic
The design traffic shall be estimated in terms of cumulative number of standard axles(8160 kg) to be carried by the pavement during the design period. Estimate of the initial daily average traffic flow shall be based on at least 7 days, 24 hrclassified traffic counts. IRC: 9 may be used as guidance for carrying out the traffic census. Any likely change in traffic due to proposed four laning of the facility and/or futuredevelopment plans, land use, shall be duly considered in estimating the design traffic.
Traffic growth rate shall be established for each category of commercial vehicles to be considered for design of pavement. For traffic projections, the procedure outlined in IRC: 108 may be followed. The Concessionaire shall adopt a realistic value of the rate of traffic growth, provided that annual rate of growth of commercial vehicles shall not be adopted less than 5 per cent. The design traffic in case of service road shall be five million standard axles. The crust composition shall be provided accordingly.
Paved Shoulders
(i) Paved shoulders shall be provided as specified in this Manual
(ii) If the thickness of the existing paved shoulder, if any, is less than the thickness of
the existing pavement, the paved shoulders shall be reconstructed to the pavement
thickness in the adjoining carriageway.
Construction, Workmanship and Quality of Works
All materials, construction operations, workmanship, surface finish and quality of
completed construction for all pavement works including sub-grade, sub-base, base course,bituminous surface courses for both new pavement and strengthening of existing pavements, shoulders, service roads, etc. shall conform to the specified requirements and comply with the provisions of Section 900 of the MORTH Specifications.
HIGHWAY DRAINAGE
General
The design and construction of surface and subsurface drains for highway drainage shall be carried out in accordance with the requirements of this Section.
For efficient drainage system for the entire Project Highway including structures and facilities, directions contained in Clause 309 of MORTH Specifications, IRC:SP:42 and IRC:SP:50 as relevant shall be followed.
In road sections in cuttings and at underpasses where it may not be possible to drain out the water using gravity flow, necessary arrangement for pumping shall be made.
Detailed survey for levels along the proposed longitudinal drains shall be carried out on both sides of the Project Highway. The bottom levels of these drains shall meet the culverts and bridges.
Road Signs
The three types of road signs viz., mandatory/regulatory signs, cautionary/warning signs and informatory signs shall be provided as given in IRC:67 and section 802 of MORTH Specifications. Proper signs shall be provided for left in and left out at service roads for safe guidance of traffic. Clustering and proliferation of road signs shall be avoided for enhancing their effectiveness.
The material and specifications for Road Signs shall be governed by the Specifications for Road and Bridge Works issued by the MORTH.
There shall be corresponding road markings with stop signs, give way signs, merging or diverging traffic signs, lane closed signs, road narrowing signs, slip roads/diversion signs, compulsory keep left/right signs, or any other signs as per IRC:67.
Wherever the Project Highway alignment is on a curve, there shall be advance cautionary signs for sharp curves (depending on whether it is on left or right) and chevron signs (rectangular in shape with traffic yellow background and black arrow) at the outer edge of the curve. The sign for the curve ahead particularly in mountainous and steep terrain shall always be accompanied with chevron signs at the outer edge of the curve and appropriate delineation.
Road Markings
All road markings shall conform to IRC:35. Road markings shall comprise of carriageway markings, markings on intersections, hazardous locations, parking areas, etc. Where service roads are provided, proper layout and road markings shall be ensured so that merging with traffic is safe. The markings shall be done by means of a self propelled machine which has a satisfactory cut-off value capable of applying broken line automatically.
Road construction
Road Side and Median Safety Barriers
There are two types of safety barriers viz., roadside safety barriers, and median safety
barriers.
Road Side Safety Barriers
(i) Warrants: The longitudinal roadside barriers are basically meant to shield two
types of roadside hazards i.e. embankments and roadside obstacles and also for
preventing the vehicles veering off the sharp curves. The warrants for a fill section
in terms of the height and slope needing protection with roadside barriers are
shown in Fig.9.1. The barrier is not warranted for embankment having a fill slope
of 3 H:1 V or flatter. The warrants for roadside objects are mainly dependent upon
the type of obstacle and the probability of their being hit. A barrier shall be installed
only if the result of vehicle striking the barrier is likely to be less severe than the
severity of accident resulting from the vehicle impacting the unshielded obstacle.
Some of the commonly encountered roadside obstacles are bridge piers, abutments
and railing ends, roadside rock mass, culverts, pipes and headwalls cut slopes,
retaining walls, lighting supports, traffic signs and signal supports, trees and utility
poles.
(ii) Types of Roadside Safety Barriers : There are three types of longitudinal roadside
safety barriers viz:
(a) Flexible type (like wire rope fencing)
(b) Semi-rigid type like
_ “W’’ beam type steel barrier
_ Thrie beam type steel barrier
Road Boundary Stones (RBS)
Road boundary stones shall be provided at the boundary on both sides of the Right of
Way. These shall be spaced at 200 m. The boundary stones shall be of cement concrete as
per Type Design given in IRC:25. The boundary stones shall be painted with cement
primer and enamel paint and marked ‘RBS’ by paint.
Kilometre and Hectometre Stones
(i) The kilometre stones shall be provided at each kilometre on both sides of the
Project Highway. The design and specification of kilometre stones shall conform
to IRC:8. The matter to be written on various kilometre stones and the pattern
thereof shall be as specified in IRC:8.
(ii) Hectometre (200 m) Stones shall be provided at every 200 m distance on both
sides of the Project Highway. The design and specification of 200 m stones shall
conform to IRC:26. The matter to be written on the 200 m stones shall be as
specified in IRC:26.
Pedestrian Railings /Guard Rails
Pedestrian Guardrails of iron/ steel sections shall be provided as per IRC:103. The iron/ steel guard rails shall be finished with epoxy primer and two coats of synthetic enamel paint after sand blasting (appropriate corrosion protection layer shall be provided in corrosive environment). In case iron/steel sections are not suitable in corrosive environment even after providing corrosion protection layer, concrete guard rails as per IRC:103 shall be provided in those sections.
TOLL PLAZAS
The Concessionaire shall provide the Toll Plazas at the locations specified in Schedule-C for collection of toll/fee as per the Concession Agreement. The fee collection system shall be speedy, efficient and user friendly. The design of the Toll Plazas should be such that they are aesthetically pleasing and efficient and the fee collection staff should be quick, courteous and adequately trained before deployment.
Location of Toll Plaza
The location of toll plaza shall be indicated in Schedule-C of the Concession Agreement.Their locations shall be decided keeping in view the following factors:
(i) Land availability
(ii) Stream of traffic on Toll Plaza
(iii) Visibility for the approaching traffic
(iv) Reasonably away from road intersections and/or rail crossings
(v) Free from risk of flooding and submergence, etc.
(vi) Preferably on flat land and away from congested urban locations.
Pedestrian Facilities
General
Pedestrians are vulnerable to being involved in accidents. Therefore, adequate
consideration shall be given to their safety through provision of facilities. The facilities
for pedestrians given in this Section shall be provided on the Project Highway.
Footpaths (Sidewalks)
(i) The sidewalks shall be provided in the built-up sections, on both sides, by barrier
type (non-mountable) kerbs of height 200 mm above the adjacent road surface.
(ii) The width of sidewalks depends upon the expected pedestrian flow and shall be
fixed subject to land availability, but shall not be less than 1.5 m.
Pedestrian Guard Rails
Pedestrian guardrails shall be provided as specified in Section 9 of this Manual.
Pedestrian Guard Rails
Pedestrian guardrails shall be provided as specified in Section 9 of this Manual.
Pedestrian Crossings
Pedestrian crossings shall be provided where they will be well used. Pedestrian crossings
shall be suitably integrated with the overall design of the intersection.
The following criteria shall be followed regarding selection of pedestrian crossings:
(i) At-Grade Pedestrian Crossing (Pedestrian Crosswalk): Pedestrian crosswalks shall
be provided at all important intersections and such other locations where substantial
conflict exists between vehicular and pedestrian movements.
Street Lighting
General
(i) The Concessionaire shall provide lighting at locations of the Project Highway
specified in Schedule-B, using appropriate system and source of electric power as
per the requirements of this Section.
(ii) The Concessionaire shall make suitable arrangements for procuring power supply
to ensure uninterrupted lighting during night and when visibility is low, including
provision of DG sets as standby arrangements.
| Sl.No | Content | Page no |
| 1 | INTRODUCTION | |
Introduction
Highways: National Highways are the main highways running through the length and breadth of the Indian union, connecting ports , foreign highways and capitals of states and including roads of strategic and military value. They constitute the frame on the which entire road communication system of the Country is based.
Types of Highways:
1)National Highways: National Highways are the main highways running through the length and breadth of the Indian union
2)State High ways: State High ways are the other maintain trunk are arterial roads of a state, connecting up with national head quarters and important cities within the state.
3)District Roads: District Roads are the roads traversing each district of the serving area of production and markets and connecting this with each other are with national and state highways or railway or important navigational routes.
4)Village Roads: Village Roads are roads connecting villages of groups of villages with each other.
In India in most of the Metro politan cities and in other cities roads are two way lanes by which traffic problems are High.Number of vehicles are increasing day by day, two way lanes are not having space for all the vehicles.Govt. is trying to expand the the two way lanes to four way lanes.
In india vehicle has to travel in left side only.Roads are divided into columns as Twoway lanes and four way lanes.Road dividers divides the Lanes into parts as per the Road
Two way lanes are the roads in which road is divided into two columns . only one heavy vehicle can go in one column of the road. Third heavy vehicle cannot fit properly in the two way lanes.
Fig.No.1.1
Four way lanes are the roads in which road is divided into Four columns. Left side of divider having two columns in which two heavy vehicles can go in same direction same with right side of the divider.only two heavy vehicle can go in one column of the road.
Fig.No.1.2
To reduce the traffic and for the convenience, Govt. is expanding the roads and highways as two way lanes into four way lanes.
For the transportation of vehicles national Highways now expanding as four way lanes.
Extension of Two way lanes to Four way lanes.
The design and construction of the road in embankment and in cuttings shall be carried out in accordance with Section 300 of MORTH Specifications and the requirements, and standards and specifications given in this Section. This Section also covers specifications for subgrade and earthen shoulders.
Efforts should be made to remove the inherent deficiencies in plan and profile of the existing road. The final centre line of the road and the road levels shall be fixed duly considering all the relevant factors covering structural soundness, safety and functional requirements as per relevant IRC Codes and provisions of this Manual.
The existing road embankment shall be widened/ modified to the specified cross-sectional details.
Materials
Materials and Physical Requirements: All materials to be used in works shall be in conformity with the requirements laid
down for relevant item in IRC/MORTH Specifications unless otherwise specified
in this Section. If the Concessionaire proposes to use any material, which is not
covered in IRC/MORTH Specifications, it shall conform to relevant Indian
Standards, if there are any, or to the International Standards. Proprietary products
proposed to be used shall be proven by use in comparable international road and
bridge projects, and shall be supported with authenticated licensing arrangement
with the manufacturer.
The Concessionaire shall identify the proposed sources of materials and submit
the proposal prior to delivery. If it is found that proposed sources of supply do not
produce uniform and satisfactory products at any time during execution, the
Concessionaire shall procure acceptable materials conforming to the specifications
from other sources.
Structural Concrete: The Concrete for use in structures shall conform to the provisions in Clauses 302.6 to 302.9 of IRC:21 and Section 1700 of MORTH Specifications. Wherever High Performance Concrete (HPC) is proposed to be used, the same shall conform to the provisions of IRC:SP:70. Sampling and testing of concrete shall be as per Clause 302.10 of IRC:21.
Acceptance criteria for concrete shall conform to Clause 302.11 of IRC:21.
Cement
Any type of cement specified in IRC:21 may be used for the works subject to limitations,if any, specified therein.
Coarse Aggregates
Before commencement of the works, at least three samples, in accordance with the procedure laid down in IS:2430, shall be taken for each quarry source to ascertain the quality, suitability and fitness of the available material for use in the works. Fresh tests shall be conducted in case there is any change in the source or the type of rock being quarried. The proposal, along with a copy of test reports, shall be submitted
Sand/Fine Aggregates
(i) All fine aggregates shall conform to IS:383 and tests for conformity shall be carried out as per IS:2386 (Part I to VIII). The fineness modulus of fine aggregates shall be between 2.0 and 3.5.
(ii) Before the commencement of the works, at least three samples as per IS:2430 shall be taken for each quarry source to ascertain the quality, suitability and fitness of the available material for use in the works and the proposal along with a copy of test reports shall be submitted to the IE for review and comments, if any.
(iii) Fine aggregates having positive alkali-silica reaction shall not be used.
Water
(i) Water for use in the works for mixing and curing of concrete shall be in conformity with Clause 302.4 of IRC:21.
(ii) Water from each source shall be tested before the start of works and thereafter
every three months and after each monsoon till the completion of the works andthe proposal along with a copy of test reports shall be submitted to the IE for
review and comments, if any.
Chemical Admixtures
The following guidelines shall apply in selection and use of admixtures:
(i) Chemical admixtures shall comply with IS:9103 and meet the requirements
stipulated in clause 5.5 of IS:456.
(ii) Admixtures generating hydrogen or nitrogen or containing nitrates, sulphides, sulphates, or any other material liable to affect the reinforcement/embedments or concrete shall not be used.
(iii) Compatibility of admixture with the cement being used shall be tested before actual use in the works. The test shall be repeated in case of change of type or grade or source of cement.
Steel
Steel for Prestressing
In addition to the requirement mentioned in Clause 1009.2 of MORTH Specifications, the steel for prestressing shall satisfy following conditions:
Uncoated stress relieved low relaxation steel conforming to IS:14268.
(ii) Prestressing steel shall be subjected to acceptance tests in respect of modulus of elasticity, relaxation loss at 1000 hrs, minimum ultimate tensile strength, stressstrain curve etc. prior to actual use on works as per guidelines contained in BS:4447. The modulus of elasticity value, as per acceptance tests, shall conform to the design value, which shall be within a range not more than 5 per cent between the maximum and the minimum.
Bitumen
Bitumen shall be paving bitumen of viscosity grade complying with Indian Standard Specifications for “Paving bitumen” IS:73:2006 of grade appropriate for the traffic and climatic conditions of the Project Highway. The heavily trafficked roads in hot areas may find harder grade bitumen more appropriate while pavements in mountainous regions subject to sub-zero temperatures during winter months carrying relatively lower traffic loads and subject to the phenomenon of “Frost Heave” may find less viscous bitumen resistant to fatigue and cold cracking more appropriate.
The material to be used in sub grade shall satisfy the design California Bearing Ratio (CBR) at the specified density and moisture content.. Taking into account slope stability, bearing capacity, consolidation, settlement and safety considerations based on geotechnical and investigation data. Where the embankment is to be supported on a weak stratum, appropriate remedial/ground improvement measures shall be taken.
Side slopes shall not be steeper than 2H:1V unless soil is retained by suitable soil retaining structures. The side slopes shall be protected against erosion by providing a suitable vegetative cover, kerb channel, chute, stone/cement concrete block pitching or any other suitable protection measures depending on the height of the embankment and susceptibility of soil to erosion. Drainage arrangement shall be provided as per Section 6 of this Manual.
Soil investigations and tests in accordance with the requirements specified in IRC:
SP:19 and shall be reported in the Proforma given in Table 1 of IRC:SP:19. In
addition to this, all tests as per the requirements of MORTH Specifications shall
be reported.
To assess the likely compresive strength of concrete by using rebound hammer as per IS: 13311 (Part 2) - 1992.The rebound of an elastic mass depends on the hardness of the surface against which its mass strikes. When the plunger of the
rebound hammer is pressed against the surface of the concrete, the spring-controlled mass rebounds and the extent of such a rebound depends upon the surface hardness of the concrete. The surface hardness and therefore the rebound is taken to be related to the compressive strength of the concrete. The rebound value is read from a graduated scale and is designated as the
rebound number or rebound index. The compressive strength can be read directly from the graph provided on the body of the hammer.
Along the alignment of the road, where unstable strata, soft material or poor subsoil conditions have been met with at the foundation level, the soil profile shall be drawn after determining through borings, the type of soil at different levels. The borings shall be at maximum interval of 100 m to a depth of 2 m or more below the existing ground as necessary. In the case of high embankments, the borings shall be taken down to a depth equal to twice the height of the embankment.
(f) Any particular construction problems of the area or other important features.
(g) Geotechnical properties of pond ash, covering parameters specified in Table 1 of IRC: SP: 58 and Optimum Moisture Content (OMC) – dry density relationship for heavy compaction. This information shall be furnished, in case pond ash is used in embankment construction.
Designing
GEOMETRIC DESIGN AND GENERAL FEATURES
General
(i) This section lays down the standards for geometric design and general features for four-lane divided carriageway.
(ii) (a) In built-up areas, 6-lane divided carriageway along with service roads shall be provided as part of 4-laning of the Project Highway. Such stretches where the requirement of 6-laning is dispensed with and only 4-laning with or
without service road and footpath is to be provided will be as indicated in
Schedule-B of the Concession Agreement.
(b) Where there is constraint of ROW width, the Authority may specify
construction of a bypass. The alignment of the bypasses shall be as specified
in Schedule-B and in conformity with the site earmarked in Schedule-A of
the Concession Agreement.
(iii) The geometric design of the Project Highway shall conform to the standards set out in this section as a minimum.
(iv) As far as possible, uniformity of design standards shall be maintained throughout the length of the Project Highway. In case of any change, it shall be effected in a gradual manner.
(v) Where the existing road geometrics are deficient with respect to minimum
requirements and its improvements to the prescribed standards is not feasible due to any constraint in acquisition of additional land, such stretches shall be as specified
in Schedule-B of the Concession Agreement.
(vi) Existing horizontal curves, which are found deficient in radius, layout, transition lengths or super-elevation shall be corrected to the standards specified in this section.
(vii) Any deficiencies in the vertical profile in respect of grades, layout of vertical curves and sight distance shall be corrected to meet the minimum requirements specified in this section.
Pavement Design
The design and construction of new pavement sections, and of strengthening measures(overlay) for the existing pavement shall be carried out in accordance with the criteria,standards and specifications given in this section. Where alternative specifications or materials are proposed to bring in innovation in design etc The design of new pavement sections or strengthening of existing pavements shall take into account all relevant factors for assuring reliable performance and shall also satisfy the specified minimum performance requirements.
The Concessionaire shall undertake the necessary soil, material and pavement
investigations and traffic volume and axle load studies in accordance with the good industry practice for preparing detailed designs.
The materials, mixes and construction practice shall meet the requirements prescribed in the MORTH/IRC Specifications.
Where problematic conditions such as expansive soils, swamps or marshes, flooding,poor drainage, frost susceptible areas etc. are found to exist, adequate measures shall be adopted to deal with such site conditions.
Design Traffic
The design traffic shall be estimated in terms of cumulative number of standard axles(8160 kg) to be carried by the pavement during the design period. Estimate of the initial daily average traffic flow shall be based on at least 7 days, 24 hrclassified traffic counts. IRC: 9 may be used as guidance for carrying out the traffic census. Any likely change in traffic due to proposed four laning of the facility and/or futuredevelopment plans, land use, shall be duly considered in estimating the design traffic.
Traffic growth rate shall be established for each category of commercial vehicles to be considered for design of pavement. For traffic projections, the procedure outlined in IRC: 108 may be followed. The Concessionaire shall adopt a realistic value of the rate of traffic growth, provided that annual rate of growth of commercial vehicles shall not be adopted less than 5 per cent. The design traffic in case of service road shall be five million standard axles. The crust composition shall be provided accordingly.
Paved Shoulders
(i) Paved shoulders shall be provided as specified in this Manual
(ii) If the thickness of the existing paved shoulder, if any, is less than the thickness of
the existing pavement, the paved shoulders shall be reconstructed to the pavement
thickness in the adjoining carriageway.
Construction, Workmanship and Quality of Works
All materials, construction operations, workmanship, surface finish and quality of
completed construction for all pavement works including sub-grade, sub-base, base course,bituminous surface courses for both new pavement and strengthening of existing pavements, shoulders, service roads, etc. shall conform to the specified requirements and comply with the provisions of Section 900 of the MORTH Specifications.
HIGHWAY DRAINAGE
General
The design and construction of surface and subsurface drains for highway drainage shall be carried out in accordance with the requirements of this Section.
For efficient drainage system for the entire Project Highway including structures and facilities, directions contained in Clause 309 of MORTH Specifications, IRC:SP:42 and IRC:SP:50 as relevant shall be followed.
In road sections in cuttings and at underpasses where it may not be possible to drain out the water using gravity flow, necessary arrangement for pumping shall be made.
Detailed survey for levels along the proposed longitudinal drains shall be carried out on both sides of the Project Highway. The bottom levels of these drains shall meet the culverts and bridges.
Road Signs
The three types of road signs viz., mandatory/regulatory signs, cautionary/warning signs and informatory signs shall be provided as given in IRC:67 and section 802 of MORTH Specifications. Proper signs shall be provided for left in and left out at service roads for safe guidance of traffic. Clustering and proliferation of road signs shall be avoided for enhancing their effectiveness.
The material and specifications for Road Signs shall be governed by the Specifications for Road and Bridge Works issued by the MORTH.
There shall be corresponding road markings with stop signs, give way signs, merging or diverging traffic signs, lane closed signs, road narrowing signs, slip roads/diversion signs, compulsory keep left/right signs, or any other signs as per IRC:67.
Wherever the Project Highway alignment is on a curve, there shall be advance cautionary signs for sharp curves (depending on whether it is on left or right) and chevron signs (rectangular in shape with traffic yellow background and black arrow) at the outer edge of the curve. The sign for the curve ahead particularly in mountainous and steep terrain shall always be accompanied with chevron signs at the outer edge of the curve and appropriate delineation.
Road Markings
All road markings shall conform to IRC:35. Road markings shall comprise of carriageway markings, markings on intersections, hazardous locations, parking areas, etc. Where service roads are provided, proper layout and road markings shall be ensured so that merging with traffic is safe. The markings shall be done by means of a self propelled machine which has a satisfactory cut-off value capable of applying broken line automatically.
Road construction
Road Side and Median Safety Barriers
There are two types of safety barriers viz., roadside safety barriers, and median safety
barriers.
Road Side Safety Barriers
(i) Warrants: The longitudinal roadside barriers are basically meant to shield two
types of roadside hazards i.e. embankments and roadside obstacles and also for
preventing the vehicles veering off the sharp curves. The warrants for a fill section
in terms of the height and slope needing protection with roadside barriers are
shown in Fig.9.1. The barrier is not warranted for embankment having a fill slope
of 3 H:1 V or flatter. The warrants for roadside objects are mainly dependent upon
the type of obstacle and the probability of their being hit. A barrier shall be installed
only if the result of vehicle striking the barrier is likely to be less severe than the
severity of accident resulting from the vehicle impacting the unshielded obstacle.
Some of the commonly encountered roadside obstacles are bridge piers, abutments
and railing ends, roadside rock mass, culverts, pipes and headwalls cut slopes,
retaining walls, lighting supports, traffic signs and signal supports, trees and utility
poles.
(ii) Types of Roadside Safety Barriers : There are three types of longitudinal roadside
safety barriers viz:
(a) Flexible type (like wire rope fencing)
(b) Semi-rigid type like
_ “W’’ beam type steel barrier
_ Thrie beam type steel barrier
Road Boundary Stones (RBS)
Road boundary stones shall be provided at the boundary on both sides of the Right of
Way. These shall be spaced at 200 m. The boundary stones shall be of cement concrete as
per Type Design given in IRC:25. The boundary stones shall be painted with cement
primer and enamel paint and marked ‘RBS’ by paint.
Kilometre and Hectometre Stones
(i) The kilometre stones shall be provided at each kilometre on both sides of the
Project Highway. The design and specification of kilometre stones shall conform
to IRC:8. The matter to be written on various kilometre stones and the pattern
thereof shall be as specified in IRC:8.
(ii) Hectometre (200 m) Stones shall be provided at every 200 m distance on both
sides of the Project Highway. The design and specification of 200 m stones shall
conform to IRC:26. The matter to be written on the 200 m stones shall be as
specified in IRC:26.
Pedestrian Railings /Guard Rails
Pedestrian Guardrails of iron/ steel sections shall be provided as per IRC:103. The iron/ steel guard rails shall be finished with epoxy primer and two coats of synthetic enamel paint after sand blasting (appropriate corrosion protection layer shall be provided in corrosive environment). In case iron/steel sections are not suitable in corrosive environment even after providing corrosion protection layer, concrete guard rails as per IRC:103 shall be provided in those sections.
TOLL PLAZAS
The Concessionaire shall provide the Toll Plazas at the locations specified in Schedule-C for collection of toll/fee as per the Concession Agreement. The fee collection system shall be speedy, efficient and user friendly. The design of the Toll Plazas should be such that they are aesthetically pleasing and efficient and the fee collection staff should be quick, courteous and adequately trained before deployment.
Location of Toll Plaza
The location of toll plaza shall be indicated in Schedule-C of the Concession Agreement.Their locations shall be decided keeping in view the following factors:
(i) Land availability
(ii) Stream of traffic on Toll Plaza
(iii) Visibility for the approaching traffic
(iv) Reasonably away from road intersections and/or rail crossings
(v) Free from risk of flooding and submergence, etc.
(vi) Preferably on flat land and away from congested urban locations.
Pedestrian Facilities
General
Pedestrians are vulnerable to being involved in accidents. Therefore, adequate
consideration shall be given to their safety through provision of facilities. The facilities
for pedestrians given in this Section shall be provided on the Project Highway.
Footpaths (Sidewalks)
(i) The sidewalks shall be provided in the built-up sections, on both sides, by barrier
type (non-mountable) kerbs of height 200 mm above the adjacent road surface.
(ii) The width of sidewalks depends upon the expected pedestrian flow and shall be
fixed subject to land availability, but shall not be less than 1.5 m.
Pedestrian Guard Rails
Pedestrian guardrails shall be provided as specified in Section 9 of this Manual.
Pedestrian Guard Rails
Pedestrian guardrails shall be provided as specified in Section 9 of this Manual.
Pedestrian Crossings
Pedestrian crossings shall be provided where they will be well used. Pedestrian crossings
shall be suitably integrated with the overall design of the intersection.
The following criteria shall be followed regarding selection of pedestrian crossings:
(i) At-Grade Pedestrian Crossing (Pedestrian Crosswalk): Pedestrian crosswalks shall
be provided at all important intersections and such other locations where substantial
conflict exists between vehicular and pedestrian movements.
Street Lighting
General
(i) The Concessionaire shall provide lighting at locations of the Project Highway
specified in Schedule-B, using appropriate system and source of electric power as
per the requirements of this Section.
(ii) The Concessionaire shall make suitable arrangements for procuring power supply
to ensure uninterrupted lighting during night and when visibility is low, including
provision of DG sets as standby arrangements.
Sunday, 25 March 2012
Bamboo Project
| 6. Demo constructions | |
| List of figures in section 6 | |
| Fig. 6.1.1 | A photograph of the school building with bamboo mat |
| boards | |
| Fig. 6.1.2 | Interior of the school building, shelves of plastered half split |
| bamboos below the window level | |
| Fig. 6.1.3.a | A photograph of the interior of the school building, gable |
| wall from inside | |
| Fig. 6.1.3.b | A photograph of the interior of the school building, landings |
| of the Twin arch supported A frame | |
| Fig. 6.1.4 | A sketch of the 7.3m Span A frame supported by the twin |
| bamboo arches vertically separated by ferro cement bands | |
| with three vertical bamboo ties and Centre 2 cross GI wire | |
| ties | |
| Fig.6.1.5 | A photograph of the school building: Plastering of the half |
| split bamboo that make up the gable walls | |
| Fig. 6.2.1 | A view of the small house with ferro cement band twin |
| bamboo arch supported A frames | |
| Fig. 6.2.2 | A view of the small house with ferro cement band twin |
| bamboo arch supported A frames | |
| Fig. 6.2.3 | An inside view of the A frames supported by Twin arches |
| with ferro cement band ties | |
| Fig. 6.2.4 | A plan of the small house with ferro cement band twin |
| bamboo arch supported A frames and bamboo mat boards as | |
| roof | |
| Fig. 6.3.1 | A plan of the small house with near horizontal roof |
| Fig. 6.3.2 | A view of the small house with near horizontal roof of light |
| weight cellular concrete from the top of a building on the | |
| south | |
| Fig. 6.3.3 | A view of the small house with near horizontal roof from |
| the north-east | |
| Fig. 6.3.4 | A view of the small house with near horizontal roof during |
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| construction | |||
| Fig. 6.3.5 | Floor plan | of the small house with near horizontal roof | |
| Fig. 6.4.1.a | An interior | view | of the small house with thatched roof |
| over bamboo bows | |||
| Fig. 6.4.2 | A view of the small house with thatched roof from the north | ||
| Fig. 6.4.3 | A view from the east of the small house ready to on the | ||
| thatch for the roof | |||
| Fig. 6.4.4 | A plan of the small house with thatched roof | ||
| Fig. 6.5.1 | A view of the 30m long sheds from east | ||
| Fig. 6.5.2 | A view of the two long sheds from the south | ||
| Fig. 6.5.3.a | An interior view | of the long shed with vertically separated | |
| twin bamboo arches with bamboo ties and ferro cement | |||
| band ties | |||
| Fig. 6.5.3.b | An interior view of the long shed: landings of the bows | ||
| with ferro cement band ties | |||
| Fig. 6.5.3.c | An interior view of the long shed : 3 ties for each bow | ||
| between the horizontal tie and lower arch – enables one to | |||
| use the space between the horizontal ties and roof bottom as | |||
| a huge storage area | |||
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6.1 7.3 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a primary school building in HET campus.
Size of the building: **10.6 m long and 7.3m wide** Figs. 6.1.1 to 6.1.3 show the photographs of the building.
Fig. 6.1.1 A photograph of the school building with bamboo mat boards
Fig. 6.1.2 Interior of the school building, shelves of plastered half split bamboos below the window level
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Fig. 6.1.3.a A photograph of the interior of the school building, gable wall from inside.
Fig. 6.1.3.b A photograph of the interior of the school building, landings of the Twin arch supported A frame
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Columns:
There are three columns separated by 3.6 m in the central part of each long wall Each of the columns is of 2m high spun cement pipe of outer dia 30cm and inner dia 26 cm. Only 1m of the pipe stands above the floor level while the rest goes down into the foundation and elevation of close to 45 cm.. It is filled with sand cement mortar all the way to the top but for the last 30cm. A 10cm x 10cm cross section RCC garden post is put into the spun pipe from the top to a depth of 30 cm and the inside of the pipe is completely grouted with cement concrete.
Arch foundations:
In the space between the columns is built an arch with RR masonry except for the last 15cm which is of brick masonry. This is referred to as arch foundation.
Walls:
The long walls: These are built with fly ash bricks to a thickness of 22.5cm up to the lentil level and 10cm thickness for about 75cm above the lentil level.
The short walls: These are 10 cm thick single brick walls that meander providing cup boards two on either side of the black board in the North side wall and three on the South side wall up to the lentil level or the black board level.
Above that it is a a single brick 10cm thick wall. All the walls are plastered on both sides.
Lentil tie beam cum sun shade:
On three sides around the building, a single thin beam of thickness 5cm and width of 110cm is casted out of which we get sun shades to a width of 45cm on the out side of the walls and 55cm wide slabs on to the inside of the walls to act as luggage storage bin. The fourth side(North facing short wall) has a big black board and hence the lentil beam does not have either the projection into the room or sun shade out side. The steel reinforcement is 6 nos of 6mm dia steel rods along the length and 8 mm dia steel rods in the transverse direction every 20 cm.
There is another thin RCC tie at the top of the wall linking the steel rods that come out of the top of the RCC garden posts through two 6mm dia steel rods.
The twin vertically separated twin bow arches supporting the ‘A’ frames:
The ‘A’ frames are supported by the twin vertically separated bamboo arches with ferro cement band ties with a span of 7.3m(24 ft) which are described earlier in section 5.5. These are further strengthened by three vertical ties of half split bamboos that go up all the way from bottom horizontal tie to the A frame sides at the top. Two cross GI wire ties from center of the horizontal tie to ferro cement band ties at the quarter span points further reinforce the frame.
A sketch of the ‘A’ frame supported by the bamboo arches is shown in Fig. 6.1.4.
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Ferroceemnt band ties
Bamboo
Brick walls
GI wire ties
Fig. 6.1.4 A sketch of the 7.3m Span A frame supported by the twin bamboo arches vertically separated by ferro cement bands with three vertical bamboo ties and Centre 2 cross GI wire ties.
Note: The two bamboos in the middle of the 2 GI wire ties are used to twist the GI wires, originally in the form a loose loop, locally called “Bisi”. Upon twisting, the GI wire loop reduces in length and becomes tight.
The advantage is that holes and bolts & nuts are not necessary. Traditionally the coconut fibre ropes are used for the purpose. With time, if the tie becomes loose, then the bamboo is twisted a little further to make the tie tight.
In all, 10 such A frames are used out of which 8 are evenly spaced in the centre with about 1.15m spacing while the last one on either side rest directly over the short walls.
The large ferro cement band ties at the ends of the A frames rest on the brick work that is raised from the lentil beam slab that projects into the room doubling as luggage storage utility.
Originally this brick work became necessary as the distance between the top of the long walls is so much that the end ferro cement bands of the ‘A’ frame got a bearing of just a few cm on the wall. This is probably due to a mistake in the measurement of the wall separation. But for this mistake, the end bands of the ‘A’ frame should have rested over the top of the long walls directly with about 10 cm bearing on each wall with out the additional brick work over the lentil slab beam.
Purlins and cross ties:
Both the arches and the sloping sides are tied with several round bamboos as purlins parallel to the long walls but obviously at different vertical planes.
Two giant X ties are made with bamboos and these have eight edges in all: four of these edges start from the four corners of the room; two each of the other four edges start from the two mid points of the long walls. The bamboos of these X crosses curve around the different arches of the A frames and are tied to the same at several places with binding wire ties. Further, three bamboos on each side start from the top of the short walls and lean against the fourth arch from the short wall
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and are tied to these securely with several binding wire ties. These help in keeping the A frames in vertical position even when the gable walls are subjected to wind loads.
Gable walls:
Over the short walls, the ‘A’ frames have a big triangular opening. It was decided to close these openings with what are called gable walls.
Round bamboos are tied at three different levels horizontally over the short wall. These are tied to different vertical and cross ties of the over lying ‘A’ frames. Half split bamboos of suitable lengths are then vertically placed above the short walls next to each other with their troughs facing out side closing the triangular space. Chicken mesh is then stretched on the out side of the half split bamboos and tied to the bamboos. This is then plastered with sand cement mortar.
Fig.6.1.5 A photograph of the school building: Plastering of the half split bamboo that make up the gable walls
6.2 3.5 m span bamboo mat board sloped roof over bamboo bow supported ‘A’ frames for a small house.
This is located in the second campus of Haritha Ecological Institute.
This has six columns each of 3.35 m long RCC garden post out of which 2.45 m is above the floor level which itself has an elevation of about 0.4m above the natural ground. These are in two rows of three each separated by 3.5m and their tops are joined by 6 round wood beams of dia about 15 cm.
7 of the twin arch bow beams supported ‘A’ frames rest over the wooden beams directly. The walls are of single brick and 10 cm thick.
The roof is of bamboo mat boards which by themselves give an eve of 60 cm on all sides.
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Figs. 6.2.1 to 6.1.3 show some photographs of the house while Fig. 6.2.4 shows a sketch of the plan of the house.
Fig. 6.2.1 A view of the small house with ferro cement band twin bamboo arch supported A frames.
Fig. 6.2.2 A view of the small house with ferro cement band twin bamboo arch supported A frames.
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Fig. 6.2.3 An inside view of the A frames supported by Twin arches with ferro cement band ties
Shelves, 2m high
Verandah,
Room, with 6 windows and two doors
North
Doors(2)
Shelves up to kitchen top
Fig. 6.2.4 A plan of the small house with ferro cement band twin bamboo arch supported A frames and bamboo mat boards as roof.
6.3 3m & 3.4 m Span ‘Flat Roof’ small house over bamboo bow supported beams: bamboo roof panels with ferro cement over lay, in HET campus.
This small house has two portions, one with aspan of 3m and the other with a span of 3.4 m.
The smaller portion is a single room while the larger portion has a verandah and bath cum toilet in it.
Fig. 6.3.1 shows the plan of the house while figs 6.3.2 to 6.3.4 show the photographs of the house.
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| Shelves, 2m high | Dressing | Roof over hang | ||||||||||||||||||||
| Bamboo arches | ||||||||||||||||||||||
| with 3m span | Bath &Toilet | |||||||||||||||||||||
| Room, with 6 | ||||||||||||||||||||||
| windows and | North | |||||||||||||||||||||
| two doors | ||||||||||||||||||||||
| 3.3m span | ||||||||||||||||||||||
| Bamboo arches, | ||||||||||||||||||||||
| Doors(2) | FerCem band ties | |||||||||||||||||||||
| Shelves up to kitchen | Verandah, | |||||||||||||||||||||
| top | ||||||||||||||||||||||
| Fig. 6.3.1 | A plan | of the small house with near horizontal roof. | ||||||||||||||||||||
Fig. 6.3.2 A view of the small house with near horizontal roof of light weight cellular concrete from the top of a building on the south.
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| Fig. 6.3.3 | A view of the small house with near horizontal roof from the |
| north-east. |
Fig. 6.3.4 A view of the small house with near horizontal roof during construction.
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| Shelves, 2m high | Dressing | ||
| room | Bath &Toilet | ||
Room, with 6 windows and two doors
Verandah,
North
Doors(2)
Shelves up to kitchen top
Fig. 6.3.5 Floor plan of the small house with near horizontal roof
6.4 4.2 m span simple bamboo bow supported ‘A’ frames with a thatched roof house of 30 sq.m area, in Paloncha. (Not covered under the project)
Figs 6.4.1 to 6.4.3 show the photographs of the house while Fig. 6.4.4 shows the plan of the house.
Fig. 6.4.1.a An interior view of the small house with thatched roof
over bamboo bows
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PDF to Word
Minor Bridge Project
| CONTENTS | ||
| 1. INTRODUCTION | ||
| 1.1 DEFINITION OF A BRIDGE | 2 | |
| 1.2 OTHER IMPORTANT DEFINITIONS | 2 | |
| 2. SITE INSPECTION | ||
| 2.1 SELECTION OF SITE | 5 | |
| 2.2 EXISTING DRAINAGE STRUCTURES | 5 | |
| 3. COMPONENTS OF BRIDGE | ||
| 3.1 FOUNDATION | 6 | |
| 3.2 SUB - STRUCTURE | 9 | |
| 3.3 BEARINGS | 11 | |
| 3.4 SUPER STRUCTURE | 12 | |
| 4. DESIGN OF STRUCTURE | ||
| 4.1 DESIGN LOADS & STRESSES | 17 | |
| 4.2 HYDROLOGY | 18 | |
| 4.3 SUB-SOIL INVESTIGATION | 18 | |
| 4.4 TEMPORARY WORKS | 18 | |
| 4.5 DESIGN | 19 | |
| 4.6 REINFORCED EARTH RETAINING | 21 | |
| STRUCTURES | ||
| 4.7 SAFETY BARRIERS | 23 |
[1]
1.INTRODUCTION
1.1 DEFENITION OF A BRIDGE
A bridge is a structure providing passage over an obstacle without closing the way beneath. The required passage may be for a road, a railway, pedestrians, a canal or a pipeline. The obstacle to be crossed may be a river, a road, railway or a valley.
In other words, bridge is a structure for carrying the road traffic or other moving loads over a depression or obstruction such as channel, road or railway.
A bridge is an arrangement made to cross an obstacle in the form of a low ground or a stream or a river without closing the way beneath.
For bridges having length more than 60m, detailed estimate is required to be submitted to Govt. for obtaining Administrative Approval. It is, therefore, necessary that site is finalized by the Superintending Engineer, Designs Circle so that detailed soil explorations as may be necessary could be done by Road Project Divisions.
1.2 SOME IMPORTANT DEFINITIONS
Small bridge
Overall length of the bridge between the inner faces of dirt walls is up to 30m and where individual span is not more than 10m
Minor bridge
Total length up to 60m
Major bridge
Total length greater than 60
Culvert
A cross drainage structure having total length of 6 m or less between inner faces of dirt wall
Foot Bridge
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A bridge extensively used for carrying pedestrians, cycles and animals
High Level Bridge
A bridge, which carries the roadway above H.F.L. of the channel
Submersible Bridge/ Vented Causeway
A bridge designed to be overtopped during floods.
Clearance
| The | shortest distance between boundaries at | a | specified | position | of | bridge |
| structure | ||||||
| Freeboard | ||||||
| The | difference between H.F.L. (allowing afflux) and foundation level of road | |||||
| embankment on approaches | ||||||
H.F.L.
Highest flood level is the level of highest flood ever recorded or the calculated level for design discharge
L.W.L.
Lowest flood level is the level of the water surface obtained in dry season
Length of Bridge
The length of a bridge structure will be taken as overall length measured along the center line of the bridge between inner faces of dirt wall
Linear Waterway
Width of waterway between the extreme edges of water surface at H.F.L.
measured at right angles to the abutment face
Effective Linear Waterway
The total width of the waterway of the bridge at H.F.L. minus effective width of obstruction
Safety Kerb
A roadway kerb for occasional use of pedestrian traffic
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Width of Carriageway
Minimum clear width measured at right angles to the longitudinal centerline of bridge between inside faces of roadway kerb or wheel grades
Vertical clearance
The height from the design highest flood level with afflux of the channel to the lowest point of the bridge superstructure at the position along the bridge where clearance is denote
20. Bearings
The part of the bridge structure which bears directly all the forces from the structure above and transmits the same to the supporting structure
Abutment
The end supports of deck of bridge, which also retains earth, fill of approaches behind fully or partly
Spill through Abutment
An abutment where soil is allowed to spill through gaps along the length of abutment such as column structure where columns are placed below deck beams and gap in between is free to spill earth
Afflux
The rise in the flood level of the river immediately on the upstream of a bridge as a result of obstruction to natural flow caused by the construction of bridge and its approaches
Bearing Capacity
The supporting power of a soil / rock expressed as bearing stress is referred to as its bearing capacity
Foundation
The part of bridge is in direct contact with and transmitting load to the founding strata
Pier
Intermediate supports of the superstructure of a bridge
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Retaining Wall
A wall designed to resist the pressure of earth filling behind
Return Wall
A wall adjacent to abutment generally parallel to road or flared up to increase width and raised up to the top of road
Toe wall
A wall built at the end of the slope of earthen embankment to prevent slipping of earth and / or pitching on embankment
Wing Wall
A wall adjacent to abutment with its top up to R.T.L. near abutment and sloping down up to ground level or a little above at the other end. This is generally at 45 degrees to the alignment of road or parallel to the river and follows the profile of earthen banks
Substructure
The bridge structure such as pier and abutment above the foundation and supporting the superstructure. It shall include returns and wing walls but exclude bearings
Skew angle of Bridge
It is the angle between the perpendicular to the flow of traffic direction and the flow direction of river
2. SITE INSPECTION
2.1 SELECTION OF SITE
Where there is any choice, select a site:
(1) Which is situated on a straight reach of the stream, sufficiently below bends
(2) Which is so far away from the confluence of large tributaries as to be beyond their disturbing influence
(3) Which has well-defined banks
(4) Which makes approach roads feasible on the straight
In siting small bridges and culverts, due consideration should be given to the geometrics of the approach alignment and the latter should essentially govern the
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selection of site unless there are any special problems of bridge design.
2.2 EXISTING DRAINAGE STRUCTURES
If, by chance, there is an existing road or railway bridge or culvert over the same stream and not very far away from the selected site, the best means of ascertaining the maximum discharge is to calculate it from data collected by personal inspection of the existing structure.
It should be seen whether the existing structure is too large or too small or weather it has other defects. All these should be carefully recorded.
3. COMPONENTS OF BRIDGE
3.1 FOUNDATION
3.1.1 Depth of foundations
The foundation shall be taken to such depth that they are safe against Scour, or protected from it. Apart from this, the depth should also be sufficient from consideration of bearing capacity, settlement, stability and suitability of strata at the founding level and at sufficient depth below it.
Depth of shallow foundations may be taken down to a comparatively shallow depth below the bed surface provided a good bearing stratum is available and the foundation is protected
Selection of a particular type of foundation is a very important job as it affects the entire proposal for the bridge. On the other hand if scour depth is less and flood depth is also reasonably small the raft foundation could be the choice.
3.1.2 Important Points
The following points are to be noted while preparing bridge proposal.
(a) Span to height ratio for Raft foundation be kept as 1.00 to 1.25
Open foundation be kept as 1.25 to 1.50
Pile foundation be kept as 1.25 to 1.75
Well foundations it should be 1.50 to 2.00
(b) The dimensions of pier, abutment and well foundation to be taken from type
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designs or from the latest I.R.C. Codes.
(c) Proper uniform sitting of well foundation could be ensured by taking the foundation into rock by about 15 cm.
(d) The raft foundation details are taken from the type designs as applicable.
(e) Other similar designs prepared and approved by the Designs Circle should also be studied and referred to.
(f) Open foundations are comparatively easy to decide about.
(g) Anchorage of open foundation into the rock shall be as per IRC-78 i.e. minimum 0.60m into hard rock and 1.50 m into soft rock excluding scour able layers.
(h) Leveling course and annular filling should be proposed for open foundation. Annular filling should be done with M 15 concrete up to rock level.
(i) Stability of foundation should be worked out. The beginner should obtain the standard calculation sheets from office, and do the calculations manually to gain confidence.
3.1.3 FOUNDATION TYPES
Generally two types of foundations are adopted for bridge structures. (i) Shallow foundations - Open foundations - Raft foundations
(ii) Deep foundations - Pile foundations - Well foundations
Open Foundations
Open foundations are preferred over any other type. These are to be provided when good-founding strata are available at shallow depth and there is not much problem of dewatering. R.C.C. footings are preferred over P.C.C. footing in case of RCC piers.
Raft Foundations
Raft foundation is designed as R.C.C. solid slab. The additional component of cut off walls on both sides U/s and D/s was considered necessary to take care of seepage and possible undermining of the raft due to seepage and the scour due to floods.
It was observed that the raft was showing signs of cracks between pier and cut off walls. The arrangement was, therefore, subsequently changed by resting pier on raft over the cut off walls.
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Raft foundation is, however, not recommended when
- Spans more that 10m raft being uneconomical.
- Bridge foundation that cannot be inspected during its service life.
- Serious problem of dewatering due to large in flow of water/standing water.
- Where open foundations are feasible.
In other cases of small span bridges on weak soils, the raft foundations may be a most practicable solution.
Well Foundations
Some important points to be noted regarding well foundations are as follows –
a. If the external diameter of single circular wells exceeds 12 m relevant provisions of clause 708.1.2 of IRC: 78-2000 shall apply.
b. The steining thickness of well shall not be less than 500 mm and shall satisfy the following relationship
h = kd L where h = minimum thickness of steining in m d = external diameter of circular well in m
L = depth of wells in m below top of well cap or LWL whichever is more
K = constant(for wells in cement concrete 0.03,brick masonry 0.05 and twin D wells 0.39(For details refer to clause 708.2.3 of IRC: 78-2000).
Piles Foundations
| Type of Strata | Minimum Embedment | |
| Hard rock | 1.5 x dia. of pile | 400 |
| Soft rock | 3.0 x dia. of pile | 250 |
| 2.0 x dia. of pile | 200 | |
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Although piles can be designed as end bearing or friction piles, only end bearing bored cast-in-situ piles drilled with rotary rig be preferred. Designs with single row of piles per substructure and annular piles filled or not filled should not generally be preferred.
3.2 SUB - STRUCTURE
Type designs available would provide sufficient information about the dimensions of the P.C.C. piers and abutments up to a height of 10m. These type designs available are for non-seismic zones only.
Grade of Concrete as are specified below : For bridges(Length > 60 m) :
| Structural member | Conditions of Exposure | ||
| Moderate | Severe | ||
| P.C.C. | M 25 | M 30 | |
| R.C.C. | M 30 | M 35 | |
| P.S.C. | M 35 | M 40 | |
| For other bridges or Culverts (<60m) : | |||
| P.C.C. | M 15 | M 20 | |
| R.C.C. | M 20 | M 25 | |
The proposed allowable compressive, tensile and shear stresses are as follows:
(i) Flexural compression scb = 0.33 fck for all grades of concret
(ii) Flexural tension stb = 0.033 fck for all grades of concrete
(iii) Shear = As below
(a) The allowable shear stress for R.C.C. members subject to flexure, shear
and members subject to axial compression, the allowable shear stress carried by
the concrete (tc) shall be as per following table.
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| 100 A | Permissible Shear Stress in Concrete, t 14/mm2 | ||||
| bd | Grade of Concrete | ||||
| M 20 | M 25 | M 30 | M 35 | M 40 and above | |
| (1) | (2) | (3) | (4) | (5) | (6) |
| 0.15 | 0.18 | 0.19 | 0.20 | 0.20 | 0.20 |
| 0.25 | 0.22 | 0.23. | 0.23. | 0.23. | 0.23. |
| 0.50 | 0.30 | 0.31 | 0.31 | 0.31 | 0.32 |
| 0.75 | 0.35 | 0.36 | 0.37 | 0.37 | 0.38 |
| 1.00 | 0.39 | 0.40 | 0.41 | 0.42 | 0.42 |
| 1.25 | 0.42 | 0.44 | 0.45 | 0.45 | 0.46 |
| 1.50 | 0.45 | 0.46 | 0.48 | 0.49 | 0.49 |
| 1.75 | 0.47 | 0.49 | 0.50 | 0.52 | 0.52 |
| 2.00 | 0.49 | 0.51 | 0.53 | 0.54 | 0.55 |
| 2.25 | 0.51 | 0.53 | 0.55 | 0.56 | 0.57 |
| 2.50 | 0.51 | 0.55 | 0.57 | 0.58 | 0.60 |
| 2.75 | 0.51 | 0.56 | 0.58 | 0.60 | 0.62 |
| 3.00 and above | 0.51 | 0.57 | 0.60 | 0.62 | 0.63 |
For slabs the allowable shear stress carried by concrete shall be Ktc Where K has the values given below
| Overall | depth | of300 or more | 275 | 250 | 225 | 200 | 175 | 150 | or |
| slab (mm) | less | ||||||||
| K | 1.00 | 1.05 | 1.10 | 1.15 | 1.20 | 1.25 | 1.30 | ||
Forces to be considered for stability of piers and abutments are given in IRC:6-2000 Loads & Stresses. The permissible increases in stresses in the various members under different load combinations are also given in the code. The same is summarized as below
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| DING RETURAN | B | |
| ROAD TOP LEVEL | ||
| PIER CAP | ||
| 1 | 1 | |
| n | n | |
| RIDING RETURN | PIER | |
| BB | ||
| FB | ||
| DOWELS | ||
| RCC RAFT | ||
| B | ||
| SECTIONAL ELEVATION ALONG A-A | ||
| ES | CUT OFF | |
| WALL | ||
| Sr. No. | Load Combination | Increase in permissible | ||
| stresses. | ||||
| 1. | Dead + Live | NIL | ||
| 2. | 1 + Secondary + Deformation + Temperature | 15% | ||
| 3. | 2 | + wind + wave pressure | 33 1/3 % | |
| 4. | 2 | + seismic + wave pressure | 50% | |
| 5. | 2 | + barge impact + wind load | 33 1/3 % | |
| 6. | Dead + water current + buoyancy + | 33 1/3 % | ||
| Earth pressure + erection + friction + | 50% | |||
| wind + grade effect 6 + Seismic - Wind | ||||
Apart from above-mentioned combinations, following load combinations should generally be checked.
- Dead + Live + wind in transverse direction Wind acting perpendicular to deck.
65 % perpendicular and 35 % along the deck. The wind velocity and method of computation of forces is given IRC: 6-2000. (Section-II).
- One span dislodged (i.e. smaller span not in position) for pier and no span condition for abutment.
3.3 BEARINGS
3.3.1 Types
Various bearings in use by the department are M.S. plate, cast steel rocker rollers, neoprene, and POT/ PTFE, R.C.C. Roller.
3.32 Selection
The selection of Bearings should be as follows :
1 | Spans upto and including 10 m for solid slab | Tar paper |
| superstructure | ||
2 | Span > 10 m and < 25m | Neoprene |
3 | For larger spans | POT/PTFE |
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Reference should be made toI.R.C.83 Section IX
Part I Metalic Bearings
Part II Elastomeric Berings
Part III POT, POT/PTFE
3.3.3 Seismic arrestors
To prevent dislodgement of superstructure reaction blocks or other types of arrestors shall be provided and designed for twice the seismic force.
3.4 SUPER STRUCTURE
Various types of superstructures are Arches, Masonry, C.C., R.C.C. Girder and deck slab, Solid Slab, R.C.C. T-Beam Slab, R.C.C. Box Beam, Voided Slab, P.S.C. Two Girder, Three Girder, Multi- Girder, Box Girder, Simply supported continuous Cantilever, Balance Cantilever, Hammer Head, Bow string girder, composite construction, cable stayed, suspension.
3.4.1 Selection of Proper Superstructure
Generally the following criteria should be followed for selection of superstructure depending on span length.
- Spans upto 10m. R.C.C. solid slab.
- Spans- 10 to 15m R.C.C. solid slab /Ribbed slab,
- Spans - 15m.to 20m R.C.C. Multi-girder slab system.
- Spans - 20m.to 30m P.S.C. Girder/Box type superstructure.
- Span - 30m to 60m P.S.C. Box girder.
For spans more than 60 m the discussions should be held with Superintending Engineer, Designs Circle regarding selection of the type of superstructure.
For spans up to 10m solid slab superstructures are found most suitable. As the span increases beyond 10m the thickness of solid slab poses difficulties during concreting. Lot of construction joints are created in the structure if proper programme of concreting is not prepared and insisted upon.
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Spans between 15m to 20m, multi-girder system would be desirable. Two-girder system should be avoided as far as possible. In case of single lane bridges two-girder system is natural choice.
For spans between 20m and 30m R.C.C. box type superstructure is considered suitable. Use of R.C.C. girder and slab system might result in excessive deflections under live load. Box girder is a more desirable shape for the superstructure.
Beyond 30 m span, it is necessary to go for P.S.C. This enables us to somewhat restrict the deck height to the desired level. For spans greater than 60m discussions should be held with Superintending Engineer, Designs Circle for deciding the type of superstructure.
3.4.2 Type Design
Type designs are available for solid slab and girder type superstructures. The type designs prepared by M.O.S.T. are also available for R.C.C. solid slab up to 10 m, R.C.C. Girder slabs upto 24 m and P.S.C. girder slab bridges upto 40 m spans.
3.4.3 Minimum thickness
Minimum thickness of deck slab shall not be less than 300 mm and 200 mm at tip of cantilever in transverse direction and minimum thickness of soffit slab shall be 240mm irrespective of provisions elsewhere. All the specified minimum thickness are from durability point of view.
3.4.4 Expansion Joints
To cater for the expansion and contraction of superstructure suitable expansion joint is required to be provided. The expansion joint is also supposed to be leak proof so that the superstructure, bearings and piers do not get damaged due to such leakage of rainwater etc.
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SUITABILITY CRITERIA FOR ADOPTION OF DIFFERENT TYPES
OF EXPANSION JOINTS
| Sr. | Type of | Suitable for adoption joint | Service | Special Consideration | |
| No | Expansion | Life | |||
| 1 | Buried | Simply supported | 10 years | Only for decks | |
| . | spans up to 10m | With bituminous | |||
| asphaltic wearing | |||||
| coat. | |||||
| 2 | Filler Joint | Fixed end of simply | 10 years | The sealant and joint | |
| . | supported spans with | filler would need | |||
| In-significant movement. | replacement if found | ||||
| damaged. | |||||
| 3 | Asphaltic | Simply supported spans | 10 years | Only for decks with | |
| . | Plug Joint | for right or skew upto | bituminous /asphaltic | ||
| (20 degree) moderately | wearing coat. Not | ||||
| curved or wide deck | suitable for bridge with | ||||
| with maxi- mum | longitudinal gradient | ||||
| horizontal movement | more than 2% and | ||||
| not exceeding 25mm. | cross camber/super- | ||||
| elevation exceeding | |||||
| 3%. | |||||
| 4 | Compression | Simply support of | 10 years | Chloroprene/ closed | |
| . | Seal Joint | continuous spans right or | Foam Seal may need | ||
| skew (upto 30°), | replacement during | ||||
| moderately curved with | service. | ||||
| maximum horizontal | |||||
| movement not exceeding | |||||
| 40 mm. | |||||
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| 5 | Elastomeric | Simply supported or | 10 years | Not suitable for | |
| . | slab seal joint | continuous spans Right or | bridges located in | ||
| skew (less than 70 degree) | heavy rainfall area and | ||||
| moderately curved with | spans resting on | ||||
| maximum horizontal | yielding support. | ||||
| movement up to 50 mm. | |||||
| 6 | Simple strip | Moderate to large simply | 25 years | Elastomeric seal may | |
| . | seal joint | supported.(cantilever/ | need replacement | ||
| continuous construction | during service. | ||||
| having right, skew or | |||||
| curved deck with | |||||
| maximum horizontal | |||||
| movement upto 70 mm. | |||||
| 7 | Modular strip/ | Large to very large | 25 years | Elastomeric seal may | |
| . | Box Seal | continuous/cantilever | need replacement | ||
| Joint | construction with right, skew | during service | |||
| or curved deck having | |||||
| maximum horizontal | |||||
| movement in excess | |||||
| of 70 mm. | |||||
| 8 | Special | For bridge having wide | 25 years | Elastometric seal may | |
| . | joints for | decks/span length of | need replacement during | ||
| special | more than 120 m. or/and | service. Provision of | |||
| condition | involving complex | these joints may be | |||
| movement/rotations in | made with prior approval | ||||
| different directions/ | of competent authority. | ||||
| plans, provision of special | |||||
| type of modular expansion | |||||
| joints such as swivel joists | |||||
| joints may be made. | |||||
These are proprietary items for which 10 years warranty shall be insisted upon from the suppliers.
For larger expansion gaps, of about 50mm and more the joint has to be designed suitably. Other types of joints are :
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- Finger type joint (Cast steel).
- Strip seal joint (Elastomeric)
- Compression seal joint (Elastomeric)
- Slab seal joint (Elastomeric)
- Modular joints. (Modules with Elastomeric)
The above joints are costly as compared to conventional joint described earlier. We are, however, left with no choice for long span bridges but for adopting them. For details of material properties refer latest M.O.S.T. specifications for Roads and Bridges.
The above item are presently patented and hence detailed design calculations are not generally made available. It should be insisted upon.
For details of these joints refer literature given by the manufacturers.
Extra care need be taken for maintaining line and level of the joint to match perfectly with the geometry of the deck surface. Expansion joint is the place wherein lies the comfort of the road users. Improper fixing invites criticism from public.
3.4.5 PARAPET AND KERB
Deciding the type of railing, kerb etc., as per the type of bridge i.e. high level or submersible.
(i)For High Level Bridge
Superintending Engineer Designs Circle’s Type drawings or Sanchi Type parapet as mentioned in designs criteria can also be adopted.
(ii) For Submersible Bridge
Railing shall be removable type. Either pipe railing or collapsible type as shown in the type drawings.
3.4.6 WEARING COAT
Earlier upto 1980 R.C.C. wearing coat was generally adopted. Now as per Govt. in P.W.D. Circular No.CEC/1179/50677/CR-225/D-29-A dated 12.08.80, following type of wearing coat are generally provided for bridges.
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Conventional Practice
High Level Bridges : Bituminous 50 mm DBM + 25 mm AC/SDBC
Submersible Bridges : C.C. M-20 with temperature steel.
Long Span Bridges : Bituminous.
Better treatment considered today is –
12 mm Mastic Asphalt as leak proof layer.
+ 50 mm DBM
+ 25 mm Bituminous concrete / Mastic Asphalt
3.4.8 WATER SPOUTS
Waterspouts are required to drain out the rainwater from the deck surface quickly. The deck has camber or super elevation, which help rainwater get quickly towards kerbs. The waterspouts located near the kerb further disposes the water out. One water spout per 20 sq.m. of the deck area is considered adequate.
- 4. DESIGNING
4.1 DESIGN LOADS & STRESSES
All new structures shall be designed for the condition when footpath is used as carriageway. The footpath portion may be provided at the same level as the bridge carriageway and separated by crash barrier in non built-up areas. In built-up areas, raised footpaths shall be provided.
All the components of structures shall be designed for a service life of 100 years except appurtenances like crash barriers, wearing surface and rubberized components in expansion joints and elastomeric bearings. All the requirements to achieve durability and serviceability shall be implemented.
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4.2 HYDROLOGY
All the structures shall have adequate waterway, which shall in any case be not less than that of existing bridge (except when such waterways can be reduced in cases like clogging or silting of spans, etc.). The design discharge shall be evaluated for flood of 100-year return period.
4.3 SUB-SOIL INVESTIGATION
Independent sub-soil investigations shall be carried out to establish the soil parameters required for detailed design of foundations in accordance with relevant provisions of IRC:78 and MORTH Specifications.
4.4 TEMPORARY WORKS
4.4.1 Form Work
The Concessionaire shall be responsible for the safe, workable design and methodology for all temporary or permanent forms, staging and centering required for supporting and forming the concrete of shape, dimensions and surface finish as shown on the drawings (Refer IRC:87). Adequate foundation for the staging shall be ensured. Redundancy in support system shall also be ensured by providing diagonals and additional members.
The following guidelines shall be adopted:
(i) Formwork shall be of steel, marine ply or laminated plywood.
(ii) Only such shuttering oil (release agent) shall be used, which permits easy removal of shutters without leaving stains or other marks on the surface of the concrete. Requirements given under Clause 3.5 of IRC:87 shall also be complied with.
(iii) In case of tubular staging of heights more than 10 m, special attention shall be paid to the structural adequacy of the system, efficacy of the connections (clamps etc), and foundations. Foundation blocks of adequate thickness in M15 cement concrete shall be provided under the base plates to prevent differential settlements.
(iv) In case of prestressed concrete members, the side forms shall be removed as early as possible and the soffit forms shall permit movement of member without restraint, when prestress is applied.
(v) Adequate foundations for formwork shall be ensured.
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4.4.2 Special Temporary and Enabling Works
Designs, drawings and methodology proposed by the Concessionaire in the use of special temporary and enabling works like Launching Girders, Cantilever Construction Equipment, Tall Formwork, Shoring for Earth Retention, Lifting and Handling Equipments and the like shall be submitted to the Independent Engineer (IE) for his review and comments if any. The Concessionaire shall be fully responsible for the design and structural adequacy of all temporary and enabling works. Review by IE shall not relieve the Concessionaire of this responsibility.
4.5 DESIGN
4.5.1 Foundations and Sub-structures
The design of foundations and sub-structures shall conform to IRC:78.
Open Foundations
The design of open foundations shall conform to IRC:78. Floor protection shall be provided as per Section 2500 of MORTH Specifications.
Pile Foundations
(i) The design of pile foundations shall be done as per IRC:78. The Concessionaire shall submit a method statement supported by the following:
(a) Bore-log details for each foundation;
(b) Design assumptions;
(c) Design calculations both for single pile or group of piles and for pile type;
(d) Type of piles-Bored cast-in-situ piles and driven piles;
(e) Procedure adopted for installation of piles;
(f) Arrangements for load testing of piles;
(g) Format for reporting of test results.
(ii) The Concessionaire shall submit the following information regarding proposed proprietary system of piling:
(a) General features of the process/system along with specifications and standards.
(b) Authenticated copies of license/agreement, if any;
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(c) Details of plant and equipment to be used along with the names of manufacturers and name of process/system;
(d) Details of projects where the process/system has been successfully used;
(e) Limitations, if any;
(f) Acceptance tests and criteria;
(g) Installation and maintenance procedure and schedule; and
(h) Performance warranty.
Well Foundations
(i) For conventional method of well sinking, the Concessionaire shall submit a method statement including the following:
(a) Design calculations and drawings,
(b) Procedure for sinking and plugging of well,
(c) Format for reporting of test results.
(ii) If proprietary system of well sinking like jack down method is proposed to be used, the Concessionaire shall submit relevant information covering inter-alia the following:
(a) General features of the system along with specifications and standards and justification for the thickness of steining proposed to be adopted;
(b) Authenticated copies of license/agreement, if any;
(c) Details of plant and equipment to be used along with the names of manufacturers and name of process/system;
(d) Details of projects where the process/system has been successfully used;
(e) Limitations, if any;
(f) Acceptance tests and criteria;
(g) Installation and maintenance procedure and schedule; and
(h) Performance warranty.
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(iii) The Concessionaire in his Methods Statement shall include the procedure for sinking by special methods, carrying out tests, if any, of wells including design criteria/calculations, drawings and formats for reporting test results.
4.5.2 Approach Slabs
Approach slabs shall be provided as per Clause 217 of IRC:6 and Section 2700 of MORTH Specifications.
4.5.3 Superstructures
The design of reinforced and pre-stressed concrete superstructures shall be as per IRC:21 and IRC:18 respectively. The design of steel and steel-concrete composite super structures shall conform to IRC:24 and IRC:22 respectively.
The Concessionaire shall submit Method Statement indicating inter-alia the following:
(i) Sources of materials,
(ii) Design, erection and removal of formwork,
(iii) Layout of casting yard together with necessary details,
(iv) Production, transportation, laying, compacting and curing of concrete,
(v) Sequence of concreting in cast-in-situ construction, side shifting of girders, if applicable and placing of girders on the bearings,
(vi) Details of construction joints,
(vii) Prestressing system, if required,
(viii) Methodology and equipment for side shifting and launching of pre-cast girders,
(ix) Key personnel for execution and supervision,
(x) Testing and sampling procedure,
(xi) Equipment details.
4.6 Reinforced Earth Retaining Structures
Reinforced earth retaining structures shall not be provided for height more than 6 m unless otherwise specified, and near water bodies. Such structures should be given special attention in design, construction, ground improvement where necessary,
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maintenance and selection of System/System design. Local and global stability of the structure shall be ensured.
Design Accreditation and warranty for life of the structure from the approved supplier/ manufacturer shall be obtained and furnished. A qualified and experienced technical representative of the approved supplier/manufacturer shall be present on site throughout during the casting and erection phases to ensure that the quality of the works executed by the Concessionaire is in accordance with good industry practice.
The Concessionaire shall submit relevant information on the system covering inter-alia the following:
(i) General features of the system along with specifications and standards;
(ii) Authenticated copies of license/agreement, if any;
(iii) Details of plant and equipment to be used along with the names of manufacturers and name of process/system;
(iv) Details of projects where the process/system has been successfully used;
(v) Limitations, if any;
(vi) Acceptance tests and criteria;
(vii) Installation and maintenance procedure and schedule; and
(viii) Performance warranty.
The Concessionaire shall submit a method statement including the following:
(i) Design assumptions, calculations and drawings,
(ii) Construction Procedure,
(iii) Tests to be conducted including frequency and the formats for reporting the test results.
The packaging of reinforcing elements shall clearly indicate the name of the manufacturer/ supplier and brand name, date of production, expiry, if any and batch identification number along with the manufacturer’s test certificates.
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4.7 Safety Barriers
(i) For bridges without foot paths, concrete crash barriers shall be provided at the edge of the carriageway on all new bridges.
(ii) The type design for the crash barriers may be adopted as per IRC:5. The design loading for the crash barriers shall be as per Clause 209.7 of IRC:6.
(iii) For bridges with foot paths, pedestrian railing shall be provided on the outer side of footpath.
(iv) The railings of existing bridges shall be replaced by crash barriers, where specified in Schedule-B of the Concession Agreement.
(v) Parapets/Railings of the existing bridges/culverts to be repaired/replaced shall be specified in Schedule-B of the Concession Agreement.
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