Effects of support settlement on continuous deep beams and STM modeling

This paper investigates the effects of differential support settlement on the strength and behavior of two-span Continuous Deep Beams (CDBs). An experimental program consisting of six specimens has been carried out with spring supports to investigate the effects of differential settlement and the web reinforcement on the beam behavior. Test results including crack patterns, load–deflection curves, strains in steel, serviceability loads and ultimate loads are presented and discussed with the effects of support stiffness and web reinforcement. It is shown that settlement of the middle support significantly affects the serviceability load, crack pattern and failure mode. However, for ultimate strength, the beams exhibit considerable tolerance in accommodating differential support settlement, particularly for those with web reinforcement. A direct Strut-and-Tie Model (STM) is proposed for beams subjected to support settlement. Good agreement is found between the test results and STM predictions on support reactions and ultimate loads. The method can be easily implemented through an excel spreadsheet, thus making it an attractive tool for engineers.