The bridge was a pedestrian cable stayed bridge, See fig (18). It was 52 m arched span, composite steel pipe truss in the shape of triangles and a precast concrete deck. The pylon was concrete, has the transitional curve shape, and would be founded on the rock. See pictures below.
My Role in the Project (in Detail):
1) I reviewed the relevant project correspondence, documents and drawings.
2) I built up a 3D finite element analytical model, using MIDAS Civil Software, see fig (19).
3) I used the Unknown Load Factor technique in Midas to find out the cable forces. A Lot of cable forces could be suggested, while one of these force values will satisfy some critical criteria and considered optimal. In my opinion, the criteria (that I have implemented them in the model) to get these values were:
· Minimum vertical deflections of the floor beam connections with the stayed cables.
· Minimum compression stresses in the main bottom chord (laterally constrained steel pipe).
· Acceptable bending moments in the pylon sections (less than the cracking moment).
4) I reanalyzed the model after including the proposed cable forces, using geometric nonlinear analysis, fig. (20). I elaborated with my supervisor to adjust the design.
Loads, factors, and combinations that I used were according to South Africa Bridge Code. I also checked them according to CHBDC and CSA-Handbook of Steel Construction.
Figure (18) 7th Avenue Pedestrian Bridge
Figure (19). The finite element bridge model.
Figure (20) the analysis results of the bridge A) Stress contour in the deck, B) cable forces and deformed shape. 