| This project is a continuation of research which addresses some of the numerous bridge problems on Iowa's low volume road (LVR) system. Results from the first two phases of the investigation supported the need of investigating the Modified Beam-in-Slab Bridge (MBISB) design. This final phase of the investigation was undertaken to evaluate two modifications: an alternative shear connector (ASC) as a means to develop composite action and a transverse arch formed between the girders to reduce the self weight of the system. By including the modifications, a lower cost LVR bridge replacement (the MBISB) for spans greater than 50 ft was proposed.; This dissertation presents the development of the MBISB system in the form of three technical papers; the first paper summarizes the previous research and provides an overview of the laboratory testing for the MBISB system. The results from the laboratory phase, presented in detail in the second technical paper, indicated the modifications were applicable to full scale LVR structures; thus, two demonstration bridges were designed and constructed. The first bridge, MBISB 1 (L = 50 ft, W = 31 ft), consists of 16-W12 x 79 girders on 2 ft centers; the second bridge, MBISB 2 (L = 70 ft, W = 32 ft), consists of 6-W27 x 129 girders on 6 ft centers.; The demonstration bridges were instrumented for strains and deflections at critical sections and were field tested to determine the structural behavior. The resulting data confirmed compliance with strength and serviceability requirements. Based on the field data and subsequent analysis, the demonstration bridges were found to exceed design requirements with considerable reserve capacity. The results of the field testing are presented in the third technical paper. The two demonstration bridges were constructed by in-house forces and had a total cost of approximately 20 percent less than conventional designs.; A MBISB design methodology was then developed based on the test results and applicable American Association of State Highway and Transportation Officials (AASHTO) Load Resistance Factored Design (LRFD) Bridge Design Specification requirements for use in designing other MBISBs. |
