Bridges, Concrete

Wheel load distribution on highway bridges is an important response parameter in determining structural member size and consequently the strength and serviceability of bridge members. It is, therefore, of critical importance in the design of new bridges and the evaluation of the load carrying capacity of existing bridges. The finite element method was used to carry out detailed analyses of different bridge types-solid slab bridges and slab-on-girder bridges with varying skew angles. The actual loads used in the bridge tests were modeled in the analysis. The available field test results for different skew bridges types viz., solid slab and slab-on-girder, were compared with the analytical values based on AASHTO, LRFD code and Finite Element Method. Important parameters such as beam spacing, span length, slab thickness, flexural rigidities of longitudinal and transverse girders, number of traffic lanes and total curb-to-curb deck width were identified in the load distribution of the skew bridges for varying skew angles.

The flexural behavior of rectangular concrete beams strengthened with externally bonded Carbon Fiber Reinforced Plastic (CFRP) laminates was studied by varying the number of plates bonded to their bottom tensile face. The increases in strength and stiffness of the beams provided by the bonded plates, over control beam without CFRP plates, were evaluated. Failure loads of the beams were determined by the ACI strain compatibility method using a FORTRAN software developed for this purpose. The predicted collapsed load agrees reasonably well with the actual failure load. Precracked solid and voided slab bridge models retrofitted with varying number of CFRP laminates were used to evaluate their contribution to the flexural resistance. The increases in strength and stiffness of the retrofitted slabs were based on the deflections, strains and crack patterns at ultimate load. Theoretical analyses to predict the load-deflection behavior of the precracked sections were performed using PCFRAME software. The predicted values agree reasonably well with the experimental results.

This study presents and illustrates a methodology to calculate the capacity of an existing reinforced concrete bridge under a non-conventional blast load due to low and intermediate pressures. ATBlast program is used to calculate the blast loads for known values of charge weight and stand off distance. An excel spreadsheet is generated to calculate ultimate resistance, equivalent elastic stiffness, equivalent elastic deflection, natural period of the beam, the maximum deflection, and the maximum rotation in the support for a simple span solid slab and T-Beam bridges. The allowable rotation could be taken as to two degrees. Naval Facility Engineering Command (NAVFAC) approach was adopted, where the inputs were material properties, span length, and area of reinforcement. The use of the Fiber Reinforced Polymer for increasing the capacity of an existing bridge is also presented in this study. Parametric studies were carried out to evaluate the performance of the solid slab and T-Beam bridges under the assumed blast load.