Bridges, Box girder

The automation of retaining structure selection and design by utilizing artificial intelligence tools is presented herein. The study involved the development of a microcomputer based expert system, RESTEX (REtaining STructure EXpert). The modules of the expert systems RETAININGEARTH, with M.1 knowledge base, and REFLEXYS have been updated and the resulting RESTEX modules are written in C using Exsys Professional for high speed and efficient utilization of memory. RESTEX is an interactive menu-driven system consisting of modules for Structure Selection, Preliminary Design, Soils Classification, Stability Analysis, and Reinforcement Design. The system is capable of performing selection, analysis, and design of gravity walls, cantilever walls, counterfort walls, reinforced earth, gabion, cantilever and anchored sheet piles.

Temperature and thermal stress variations in a segmental box girder bridge arc studied. A finite element model using the general finite element software MARC is used to predict temperature and thermal stress variation, for segmental box girder bridges. The predictions are compared with actual measured temperature data of two segmental box girder bridges, instrumented with thermocouples and vibrating wire strain gages, in Davie, Florida. Continuous monitoring was carried out for two months in July-August, 1991, and for one month in January-February, 1992. Comparison are also made with the NCHRP suggested profiles. A Monte Carlo analysis is performed to accommodate the probabilistic variation of ambient temperature conditions.

The behavior of a precast single-cell segmental box bridge with external post-tensioning is studied based on a 1:3.5 scale model of the Long Key bridge in the Florida Keys. Constant amplitude fatigue loading was applied on the model at a critical location simulating HS20-44 AASHTO truck loading. The performance of the bridge model was evaluated in terms of deflections, strains in concrete and across the joints, and behavior of joints between the segments with increasing number of cycles of fatigue loading. Thermal response of the bridge model was also studied using finite element analysis and the predicted temperature distributions were compared with the experimental values.

The feasibility of the use of precast prestressed concrete multi-box beams with transverse post tensioning is examined for a medium span bridge system based on analytical and experimental studies on a 1:2.5 scale model. Constant amplitude fatigue loading was applied on the model at typical locations simulating HS20-44 AASHTO truck loading. The performance of the bridge system was evaluated in terms of deflections, strains in the concrete, wheel load distribution, and behavior of longitudinal joints with increasing number of cycles of fatigue loading. A grillage analysis of the bridge system was carried out to predict the elastic behavior and the cracking moments and the results compared with the experimental values.