PSI - Issue 18

Muhammad Fawad et al. / Procedia Structural Integrity 18 (2019) 189–197 M.Fawad/ Structural Integrity Procedia 00 (2019) 000–000

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to detect the exposed damages of the structures. Based on this study, proper strengthening methodology can be implemented to enhance the life span of structure. So, based on the problem statement research work is carried out for the selection of strengthening methods and analysis of their application using 3D nonlinear FEM analysis. Complete and detailed comparison based on the results of 3D analysis, taking the economy, efficiency and feasibility into account is also included in the scope. 2. Methodology Methodology involves the observation and analysis of existing situation of bridge on the basis of which strengthening can be applied. Physical observation show that the surface or bridge along the sidewalls has a large number of rust spots visible from the side of the bridge and they were extended along the bridge throughout. The rust spots were also visible on one side of the bridge formwork. These rust spots were not only visible on the formwork but also seen on the knitting wires and on the spacers made of steel sheets. The main reasons were the concrete mortar deposits along the walls and slabs and even the small amount of concrete cover as well. The expansion joints of the bridge were also observed to be defective because the water seepage was seen at certain places. The neoprene pads at the supports of the bridge sections were also observed to be very older because of their excessive use. The box-girder section of bridge contains a large number of cracks. These cracks are of significant spaciousness. The extent of these cracks, their locations and spaciousness were also observed which would be described later in the result section. For detailed analysis destructive, non-destructive testing, crack analysis of bridge, Linear and Non-linear static analysis show two types of major concerns that are critical in case of this bridge. One of them is the cracking and the other one is displacement. Therefore, based on the existing condition of bridge it can be concluded that the Displacement of structure is appropriate because the maximum value (19.9mm) is less than the maximum allowable deflection of bridge (L/400=69mm). Surface stress and strain values are considerable and satisfying the ULS. Bridge have an appropriate shear resistance therefore; results are verifying the conclusions of observations made earlier. Sidewall and bottom plate are severely attacked by the cracks where the critical value of crack width is above the limiting value that needs special attention. There are very less cracks at the central support of two spans but these cracks are more critical due to stiff resistance to the vehicular burden. Results of structural cracking is exactly according to the observations of crack analysis.

Figure 1- Steel Plate Strengthening

3. Retrofitting of Bridge 3.1 Retrofitting Using Steel Plates

Externally bonded steel plates can increase the load carrying capacity of RC bridge. An adhesive agent continuously bonds the steel plates to the original structure. The bonded steel plate strengthening can be applied with or without anchorage at the plate end. To avoid the delamination of the steel plate, its end section can be anchored by bonded steel sections. Steel plates used for the strengthening are ASTM A500 galvanized mild steel plate. These plates are available in different sizes but 5mm thick steel plates having the width of 500mm are used. These plates will be connected with each other through the weld connection. So total number of steel plates needed for each span are 20