AIM : To decide final Bridge location & Bridge scheme.
Principle Factor in finalising Bridge scheme:
i) Total cost of Bridge & its approaches
ii)Upto 60m : bridge location governed by alignment of approaches
60m to 300m : bridge location governed by both alignment of approaches & bridge site.
above 300m : bridge location governed by Bridge site primarily.
General points to remember while selecting bridge site
i) on stable & well defined banks
ii) right angle to direction of flow.
iii)across narrowest width of river.
iv)15m straight stretch on both side of bridge approach.
Preparation of Hydraulic report (Check List )
a) Statement of Case
b) Recommendation of OC , CDR , CE & ADGBR (E/NW)
c) TBOO ( Comparative study of alternatives sites , Finding, opinion & Recommendation of Board.
Comparative study of alternatives sites includes Rough cost Assessment of all proposed sites (based on last estimate/ per meter cost) , Merits & demerits.
d) Appendix I of TI 3:Data for alternative bridge sites ( for all proposed Bridge sites)
e) Appendix II of TI 3 :Hydraulic data of selected bridge site ): only for finally selected bridge.
f)Appendix III of TI 3 : SSI :Sub surface investigation data ( required if applicable ).
g) Appendix IV of TI 3 :calculation of Design Discharge , Scour depth (silt factor) & Depth of foundation
h) Standard Authentication Sheet & additional information sheet (site investigation & hydraulic data)
j) Sketches & Plans:
i)Toposheet marked with alternative sites
ii)Images clicked with camera .
iii) google map/ google earth images with latitude & longitude
iii)Index map / Site Plan of Area near Bridge site (1:50000) showing proposed location, alternative bridge sites, existing road and bridge & physical features (town etc))
iv) Contour plan of stream with contour interval usually 2m (100m and 300m upstream & downstream of proposed site for catchment area upto 3 sq km & 3 to 15 sq km respectively)
v) (a)cross section of river at proposed bridge site & existing bridge site (horizontal : 1:1000, vertical :1 :100)
(b)Additional cross section of stream : one upstream , one downstream ( for smaller stream )
:two upstream & two downstream (for large rivers)
cross section : including bed level, HFL, OWL, LWL
vi)Longitudinal Section of stream (bed levels, HFL,OWL,LWL)
vii) Longitudinal section of road (upto distance 300m or more): showing ground level & proposed approach road level
viii) Alignment Plan of existing &Proposed approaches to bridge sites.
Note :
-Select atleast 2/3 Proposal of bridges
-Mark TBM on ground
RBAT :
- will prepare draft bridge scheme ( covering bridge site, type of superstructure with span arrangement, location & type of sub structure &deck level.
-will also indicate number of boreholes & extent of exploration.
