Padma Multipurpose Bridge Project

38. The composite steel truss is considered the preferred superstructure scheme for the main bridge.This scheme has the following key advantages over an extradosed concrete girder scheme:It has a lower estimated construction cost;It uses a proven form of structure for a combined road and rail bridge;Construction time would be reduced and is more suited to the seasonal nature of the site;It provides the opportunity for high quality of construction with a significant part of the workbeing constructed off site;It best accommodates the major services to be carried on the bridge;It provides better safety provision by separating road from railway and utility crossings;It provides the most direct access for future inspection and maintenance.39. Option H1 is the preferred horizontal alignment for the transition structure. It has the lowest cost,aesthetically pleasing, and more flexibility in the selection of structural bridge forms and clearancerequirements.40. Alternative 1, revetment along south bank, is the preferred scheme for RTW. The advantages ofthis option compared to other options are: Less sensitive to future changes - (i) situated along the existing bank, (ii) leaves room for ariver with higher discharge, (iii) less sensitive to channel shifting as guiding the flow parallel tothe bank. Less impact on the river downstream, as opposed to solutions aggressively narrowing downthe channel. Lower scour depth: revetments are associated with less river depth, which means lessadaptation and maintenance as opposed to short structures. Less negative social impact - (i) no additional erosion between protected area and (ii) directaccess to the river along a stable bank.Less impact on river and floodplain ecologyLess impact on the floodplain - no disturbance of flow patterns along upstream approach roadas revetment ends at floodplain.6-31