Traffic Analysis of Gomti Nagar with respect to Pedestrian FacilitiesSRMGPC LUCKNOW [INDIA]

SeminarTopic- Bridges In Hilly Challenges

ByAbhinav [1112200004]

Under Guidance of-Mr. Gangesh Kr. KasaudhanAsstt. ProfessorDepartment of Civil Engineering

Introduction

• A Bridge is a structure build to span a valley, road, river, body of water, or any other physical obstacle.

• Designs of Bridges will vary depending upon the function of the bridge and nature of the area where the bridge is to be constructed.

• The first bridges were made by nature itself—as simple as a log fallen across a stream or stones in the river.

• The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement.

• Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another.

Ctd.

• A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope capable of binding and holding together the materials used in early bridges.

• Hilly region pose unique problem for bridge construction. In a restricted hilly area itself climatic conditions, geological features and hydrological parameters vary considerably.

• Keeping in view the bridge site and various constraints, type of bridge and method of construction are to be selected carefully for safe, economical and successful completion of bridge construction.

Fig.1 History of Bridge Development

Challenges in Hilly Area Bridges Construction

Various challenges that come across while constructing bridges in hilly area are:

• Construction of bridge across deep gorges;• Construction of bridge on rivers with boundary beds;• Construction of bridges in extreme temperature zones;• Construction of bridges on sharp turn on highway;• Landslide or Debris flow.

Bridge Foundation and Substructure

• Foundation construction for any large bridge takes time. • Problems encountered during construction of foundation depend upon type of

foundation, soil strata encountered, equipment/plant deployed and logistic problems. Construction difficulties anticipated during the execution be kept in view while planning the works/ period for the job.

• Foundation can be opened foundation, pile foundation, well foundation or any other types of foundation.

• In case of well foundation, the various type of soil are encountered and it becomes difficult to give any clear time schedule about the sinking of wells unless the soil details are very clear and the anticipated profile matched with the actual encountered.

• In case of boundary and clayey soil the rate of sinking schedule is likely to be slow when compared with the sandy soil.

• Also there may be requirement of pneumatic sinking technique subsequent to open grabbing due to difficulties in sinking of well.

Superstructure

• For particular site there are numerous structural arrangements possible.

• Final proposal be made based on the greater examination of site condition may be technical, aesthetic and construction methodology.

• Special care need to be taken in case of deep gorge where there is sizable difference between soffit level and bed level. This may pose difficulties for staging and shuttering.

• Proposal recommended for site should be well read in advance. After the proposal has been finalized for particular bridge, the construction can be planned.

• The quantities of each items involved and execution method be listed. Basically method statement should be kept ready for overall execution including job estimate.

Plant Management

Requirement of equipment/plant be assessed systematically and accordingly action may be taken to arrange this for a particular job. • Quantum of work covering all the items with specifications;• Time available for work execution;• Details of equipment and also minimum requirement as per job position;• Rated capacity of equipment/ plant;• Assessed capacity;• Schedule of maintenance;• Inventory of spare parts required;• Repair cover to equipment/plant.

Material Management

• Material management is a parallel activity along with start of the Project.

• This cover procurement of camp material, office equipment, major purchased items, such as aggregates, sand, cement, steel, structural steel, shuttering consumables, electrical fittings.

• Forecasting of quantities and cost of various items on monthly basis must be done at least three to six months in advance which should be regularly reviewed.

Finance Management

• No project and implimentation or project and implimentation management can be meaningful without this.

• In case of Government work the manager should get his budget fixed on monthly basis, on the basis of work done or minimum to be fed at site, on the decision of higher authorities.

• Key to measure financial planning lies in taking all above action and taking suitable measures at appropriate times to ensure that individual inputs are achieved to the maximum and capital investment kept at the lowest level.

Types of Hilly Area Bridges

• Beam Bridge;• Truss Bridge;• Cantilever Bridge;• Arch Bridge;• Tied-Arch Bridge;• Suspension Bridge;• Cable-Stayed Bridge.

Beam Bridge

• Beam bridges are the simplest structural forms for bridge spans supported by an abutment or pier at each end.

• No moments are transferred throughout the support, hence their structural type is known as simply supported.

• The simplest beam bridge could be a stone slab or a wood plank laid across a stream.

• Bridges designed for modern infrastructure will usually be constructed of steel or reinforced concrete, or a combination of both.

Fig.2 Beam Bridge

Truss Bridge

• A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements forming triangular units.

• The connected elements may be stressed from tension, compression, or sometimes both in response to dynamic loads.

• Truss bridges are one of the oldest types of modern bridges. • The basic types of truss bridges shown in this article have simple designs

which could be easily analyzed by 19th- and early 20th-century engineers. • A truss bridge is economical to construct because it uses materials

efficiently.

Fig.3 Truss Bridge

Cantilever Bridge

• A cantilever bridge is a bridge built using cantilevers, structures that project horizontally into space, supported on only one end.

• For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed concrete.

• The steel truss cantilever bridge was a major engineering breakthrough when first put into practice, as it can span distances of over 1,500 feet (460 m), and can be more easily constructed at difficult crossings by virtue of using little or no falsework.

• A simple cantilever span is formed by two cantilever arms extending from opposite sides of an obstacle to be crossed, meeting at the center.

Fig. 4 Cantilever Bridge ComponentsFig. 5

Fig. 6 Howrah Bridge

Arch Bridge

• An arch bridge is a bridge with abutments at each end shaped as a curved arch.

• Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side.

• A viaduct (a long bridge) may be made from a series of arches, although other more economical structures are typically used today.

Fig. 7 Zhijinghe River Bridge

Tied-Arch Bridges

• A tied-arch bridge is an arch bridge in which the outward-directed horizontal forces of the arch, or top chord, are borne as tension by the bottom chord, rather than by the ground or the bridge foundations.

• Thrusts downward on such a bridge's deck are translated, as tension, by vertical ties of the deck to the curved top chord, tending to flatten it and thereby to push its tips outward into the abutments, like other arch bridges. However, in a tied-arch or bowstring bridge, these movements are restrained not by the abutments but by the bottom chord, which ties these tips together, taking the thrusts as tension, rather like the string of a bow that is being flattened. Therefore, the design is often called a bowstring-arch or bowstring-girder bridge.

Fig.8 Tied-Arch Bridge

Suspension Bridge• A suspension bridge is a type of bridge in which the deck (the load-bearing

portion) is hung below suspension cables on vertical suspenders. • The first modern examples of this type of bridge were built in the early 19th

century. • Bridges without vertical suspenders have a long history in many mountainous

parts of the world.• This type of bridge has cables suspended between towers, plus vertical suspender

cables that carry the weight of the deck below, upon which traffic crosses. • This arrangement allows the deck to be level or to arc upward for additional

clearance. • Like other suspension bridge types, this type often is constructed

without falsework.

Fig.9 Capilano Suspension Bridge

Cable-Stayed Bridge

• A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck.

• There are two major classes of cable-stayed bridges: harp and fan.• In the harp or parallel design, the cables are nearly parallel so that the height of

their attachment to the tower is proportional to the distance from the tower to their mounting on the deck.

• In the fan design, the cables all connect to or pass over the top of the towers. The fan design is structurally superior with minimum moment applied to the towers but for practical reasons the modified fan is preferred especially where many cables are necessary. In the modified fan arrangement the cables terminate near to the top of the tower but are spaced from each other sufficiently to allow better termination, improved environmental protection, and good access to individual cables for maintenance.

• The cable-stayed bridge is optimal for spans longer than cantilever bridges, and shorter than suspension bridges.

Fig.10 Cable stayed Bridge over Cooper River

Conclusion

• All bridges held generally the same amount of weight. The arch bridges held a little more than the other bridges. They were in the 1400-1500 gram range. The other bridges were in the 1000-1200 gram range.

• The bridges would not stand up on their own, so a support at each end had to be constructed. Balancing the weights on the bridges required patience. Clamps were used to hold the bridges during gluing.

• The bridges supported different amounts of weights because each type has different construction. The arch bridges supported the most weight because of the great natural strength of the arch. The pier bridges supported the least weight because the supporting piers broke during construction.

Thank You