Engineering and environmental materials - Essay Example

These two lanes of traffic were to be constructed on the lower deck level of the bridge. The same conclusion had already been given by Bristol city council. The second recommendation by the group was the removal of the upper part of the bridge that comprises of the stiffening plates. The third conclusion was that the weight of the proposed cantilever beam of the footway could be adequately and safely supported by the bridge. The method of analysis employed by Halcrow Group Ltd was SAM. In this analysis method, the individual members of the bridge were modeled in collaboration with section properties.

The section properties were obtained from site measurements as well as original drawing scripts. In determination of the section properties of the individual members, assumption was made on their ultimate tensile strengths (UTS). These sections were accredited with low ultimate tensile strength of the main members. 2D Diagrams of the bridge A. Bridge in current use B. Cross section of the Bridge The assumption in the model for the bridge in use is that the movable part is able to move freely along x-x axis since the diagram is in 2D.

The movable part has 4 degrees of freedom. The second degree of freedom is in y-y axis during lifting up and down with the help of a crane. The rationale of the movable structure of the bridge is to allow space for recreational activities within the stream .The stationary parts are fixed to a rigid base. The assumption of the cross section model is that the reaction and action are equal and opposite. The reaction of the principal structure in the footway is capable to accommodate the weight of the pedestrians.

The same applies to the principal structure in the traffic lane. Since the lane is two-way traffic, the principal structures are assumed to possess double tensile strength so as to withstand the weights of the vehicles. The rationale of the second model is to provide maximum utilization of the bridge. Most of bridges are constructed with one rationale that is to provide footway for the pedestrian. However, that is not the case in Ashton Bridge. This bridge is designed so as to provide maximum utilization.

The moment of inertia is great so as to withstand the action force (Domone & ILLston, 2010). Evaluation of the actions of the proposed bridge A. Pedestrian and cycle traffic The pedestrians would be inconvenient with the proposed repairs and maintenance. The cantilevering of the footway with steel beam supports and decking will mean indefinite closure of the existing footway. This information is obtained from Halcrow Group Ltd rapid transit report. The cycle traffic will also be affected. This is because of the removal of the corroded deck plates together with the concrete decking. B. Bus loading Bus loading will also be affected.

This is because of the proposed cutting of top corner stiffening plates. The ultimate action will be increased headroom for loading buses. C. Self weight A lot of interference will not be caused to the bridge self weight. This is because during all the proposed operations the rigid base of the bridge will not be interfered with. As indicated in the report the proposed new carriageway will be constructed on the existing steel deck plate before the deck plates are replaced. The overall weight of the bridge will increase due to the addition of the drainage modifications and