Description of the Project:
The bridge was constructed in 1925 over Al-Furat River in Der Ezour, Syria. 18 years ago, the owner of the bridge had dedicated it for small vehicles and pedestrians. The bridge was a combined suspension–cable stayed, had 5 spans (35,112.5, 112.5, 112.5, and 35). The cross section included steel stringers, floor beams, two main girders, as well as concrete deck. All the cables were anchored at the top of the pylons using steel rings, eye bars and axles. The 4 concrete pylons (30 m height each) had two high rise columns and were connected by three architectural arches. The piers were founded on the bedrock of the river without piles but massive concrete layers with the assistant of sheet piles and were surrounded by gabions. Two buried dead massive concrete anchorages were built behind the approaches. The two approach spans were composite steel girders with concrete slab. See Appendix for figure (100), and more pictures.
My Role in the Project (in Detail):
1) I reviewed carefully the existing data and the construction documents of the bridge.
2) I inspected the bridge and I was representative of the project director in site. We as a team were 3 engineers, well qualified person and 3 workers. Lots of tools were used (like calipers) to measure all the dimensions and detailed thicknesses for all components, members and sections. I joined the surveying team who was responsible to get the exact existing profile of the bridge. I supervised and confirmed the accuracy of the detailed AutoCad drawings produced for the whole bridge in the office utilizing the field measurements and photos (as part of so called the comprehensive permanent bridge file), see figures (101, 102, 103, 104, and 105).
The in-site scope of work was: to produce description, as-built drawings, inventory forms for the bridge, and fulfill careful bridge inspection paying attention to fatigue critical areas and connection details. One of the problems that we faced as a team was how to access under the deck. I suggested fabricating a steel platform with rollers and sliding it on the main two girders of the superstructure. I gave the design of this platform to an ironwork shop and we use it as an access. I conducted three kind of inspections (regarding the access), over deck (walking along the bridge, climbing the piers and abutments), below the deck (using platform and by boats), and underwater (by hiring a professional diver). By inspecting the bridge I found: lots of cables had sagged, the coating systems had failed and flaked especially at the gussets and cables, rust stains everywhere, pit corrosion in the outer wires of some cables, the concrete deck was obsolete and severely spalled and delaminated, see fig (106). I paid more attention to some non-redundant and important details in the bridge, and I recommended that these specific details to be verified by destructive tests (concrete core extracting, rolled steel section samples) and non–destructive tests (rebound hammer test). These tests were performed by a very qualified personnel (belong to the university of Damascus), and the specimens were tested in the university’s labs. Another set of non-destructive tests for steel (ultra sonic pulse, penetrating liquids) were carried out by professionals (belong to the Association of Scientific Research) to make sure about the safety of some specific parts, i.e. anchorage plates, eye bars and connections.
3) I developed 3D model for the bridge using the prepared drawings and photos, fig. (107).
4) I performed P-∆ analysis using STAAD PRO. To get the exact second order effects of the bridge. All structural elements, cables, and connections were examined. The load rating showed sufficient capacity, and the safety factors for the members in the bridge ranged from 2.1 t0 3.7.
5) I used time history analysis to assess the seismic vulnerability of the bridge and its need for retrofitting. 3 records were used and scaled to satisfy the real seismic condition on the site.
6) After the inspection and the structural evaluation I assured to the client that the bridge is safe, and then I participated in preparing the in-field-test of the bridge. I verified to the client the safety of the bridge during the movement of 5 fire trucks along the bridge provided one truck in each span.
7) I submitted (with my supervisor) bridge maintenance, improvement and strengthening plans, short-term urgent repair plan that had 25 items and long-term plan. The urgent items would upgrade the structural performance of the bridge during service, for instance: increase the transverse stiffness by means of new composite deck, replace members, add plates, straighten some buckled members, erect stainless steel extended bearing plates, sand blast, apply 3 different layers of coatings, replace bolts, provide cable protection and waterproofing system, install expansion Joints, figure (108). The long-term suggested items dealt with probability of widening the bridge and increase its structural capacity, for instance: widening, adding new horizontal cross bracings for the deck, new cables and vertical cross bracing for the pylons.
8) I participated in preparing the permanent maintenance guide of the bridge with list of activities and schedule to be done periodically. The client’s defined objectives and requirements for this project were met within the time frame provided in the RFP.
I used AISC to match the sections in the bridge with these in the standard, and used two methods in AASHTO to conduct the evaluation; the inventory and operating rating. Another textbooks were used regarding cable stayed bridges and fatigue, and will be listed in separate page.
