Researchers at the Iowa State University (ISU) Bridge Engineering Center have developed the modified beam-in-slab bridge (MBISB) system as an alternative replacement for use on low-volume roads. The system consists of longitudinal steel girders with a concrete arched deck cast between the girders. Composite action between the concrete and steel is obtained by using an alternative shear connector, also developed at ISU. Other than the nominal transverse reinforcement required for the ASC, the MBISB requires only minimal additional reinforcement. After an extensive laboratory testing phase, two demonstration bridges were constructed and field tested to determine the properties of the design. The demonstration bridges, MBISB 1 (L=50 ft, W=31 ft) and MBISB 2 (L=70 ft, W=32 ft), were constructed by in-house forces using standard construction equipment. The resulting structures saved the bridge owner slightly more than 20% over the costs of conventional designs. Test results indicated that the MBISB design exceeded strength and serviceability requirements, and the experimental lateral load distribution factors were comparable to AASHTO LRFD values. The experimental data were corroborated through analytical modeling, leading to the development of a design methodology for MBISBs ranging in length from 40 ft to 80 ft. An HS-20 truck was used as the design vehicle and all applicable AASHTO LRFD design criteria for steel girder/concrete deck bridges were satisfied. Design tables based on the desired bridge length, width, material strengths, and deck thickness were developed, along with design aids that include a sample design and standard plan sheets. The design tables are included in Volume 2 of the final report for Iowa DOT Project TR-467.
Samenvatting