28GENERAL DATA COLLECTION location of bridge site.Transportation of bridge site.Nature of crossing and affordability.Availability of local material.Traffic volume.Availability of local bridge builders.Temporary crossing.Local participation.
30Important Definition Linear water way. Economical span. Design discharge.Scour depth.Vertical clearance above HFL.
31LINEAR WATER WAYA river or canal ,or other body of water serving as a route or way of travel.
32Economic span Economic span depend upon the cost of : Substructure Superstructure
33Scour DepthThe depth which is produced due to scouring action of waterDepth of scour below the high flood levelScour depth has important in determination depth of foundationMean scour depth(d)=9.2mMax .scour depth for piers=2d =18.4m
34VERTICAL CLEARANCEMinimum vertical clearance of 5m should be ensure over the full width of roadway.The vertical clearance should be measured with regard to the highest point of carriageway.Allowance for any future raising of pavement is also be made.
36POINTS FOR SELECTION OF BRIDGE TYPE Geometric condition of the site(road alignment, design flood and highest water mark)Traffic capacity.Structural stability.Foundation conditions and strength of a abutment.Available material.Knowledge and equipment of the contractor.Clearance requirement above and below the road way.General requirements with respect to location ,financing and community values.