The Owner (Client): General Establishment of Syrian Railways (CFS Lattakia Region).
The bridge contained 7 spans concrete girders, 13.5 m span each, se fig. (80), 6 hollow tapered piers with maximum height 67 m and two abutments. The bridge was heavily deteriorated due to illegal moving loads, i. e. overload condition. The deteriorations were mainly cracks in the girders (shear, flexural, as well as hairline cracks at the supports) and cracks in the pier’s caps (between the concrete pads that carry the bearings). See below for further pictures and explanation.
My Role in the Project (in Detail):
This bridge was handled very carefully as it was the practical part of my master’s thesis. The main responsibilities that I undertook in this project were:
1) I inspected the bridge in 2 separate times: the first one (with my supervisor) dedicated to attach concrete mortars on the cracks (considered as labels with reference to the date of attachment) to figure out which of these cracks live and still active. I did a thorough second inspection procedure after 2 weeks (with the inspection team), fig. (81). The deficiency’s grades were carried out according to Swedish Norm (Sweroad). During the 2nd inspection my colleague and I drew a 100 mm x 100 mm grid on the surfaces of some girders to trace the crack propagations exactly, and then these cracks were drawn in the office by drafter with the help of the photos. All the cracks were handled by AutoCad as a layer like the beam’s profile layer and the reinforcement cage layer as well.
2) I did the structural analysis and evaluation using two different models:
· Elastic grillage model and the results were in terms of diagrams, fig (82). This model was used for rating purposes; two codes were used UIC (which depends basically on EuroCode), and AREMA.
· Sophisticated nonlinear analysis utilizing ANSYS, see fig. (83). This model was carried out for the cracked beams using smeared crack model technique, in which I modeled the concrete as a solid brick elements (solid 65) with 3 DOF in each node, while all reinforcement (longitudinal, bent over, stirrups, and side bars) were modeled using 3D bar elements (link 8) with 3 DOF in each node. Special considerations were employed to the interface between those two different elements (i.e. different constitutive laws). The material models were accounted for plastic behavior (i.e. Von Mises for steel and Willam and warnke for concrete). I verified the accuracy of the model by matching the cracks that were inspected in the real girders (the traced cracks between the grid lines that discussed earlier) and the cracks that were one of the outputs from the software. The results in this analysis were: volumetric contours, compression fields and vectors for the principal stresses, crack patterns and propagations as Avi films, the load that cause crack initiation and that which cause failure. I displayed the capacity curve of the girders in terms of load–displacements function to represent the stiffness degradation, safety margins and the current service level of performance for the superstructure, see figure (84 and 85).
3) I cooperated with my supervisor to find the appropriate strengthening process taking the existing residual strength into consideration. According to the inspection and the structural evaluation, the strengthening process were concluded as follows:
Design reinforced concrete jackets that were erected around the caps of the bridge piers, to confine the cracked caps, fig (86). Design carbon fibers (fiber reinforced polymers FRP) i.e. plates to increase the flexural capacity in mid span and biaxial sheets to increase the shear capacity. The FRP were added to the required limits that would keep the bridge on service for the next 25 years carrying the prospected up-to-date UIC standard trains. I identified another items such as: joint replacements, cleaning, debris removals, and applying protective coatings.
