Barooah, Usha Rani (2016-08). The Flexural Design of Pretensioned Bent Caps. Master's Thesis.
The use of pretensioned bent caps has brought the opportunity to utilize the advantages of accelerated construction and increased worker safety. At the same time they offer the benefits of enhanced performance. To facilitate a widespread implementation of pretensioned bent caps, this research seeks to develop flexural design procedures and recommendations on design and detailing that can benefit design engineers with readily available guidelines. A design procedure for pretensioned bent caps is proposed in this work. In this procedure, the bent caps will be primarily designed to achieve zero tension under dead load, to provide adequate strength under design load combinations and to satisfy the stress limits specified in the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design specifications. To evaluate the design procedure, a bridge inventory comprising standard Texas Department of Transportation (TxDOT) bridges with I-girders, box beams and X-beams, as well as non-standard bridges have been considered. Design results indicate no cracking expected under service loads and limited cracking expected under ultimate loads. End region detailing of the pretensioned bent caps, for resistance against tensile stresses during prestress transfer, have been reviewed from previous investigations. The pocket connections, used between pretensioned bent caps and columns, offer benefits in the use of concrete instead of grout and in the availability of large construction tolerance. A medium pocket size formed by corrugated pipe is preferable for accommodating accidental misalignment of column. The connection provides resistance to vehicle collision loads. Optimization of bridges with pretensioned bent caps has been assessed with modifications to the prestressing layout and the reconfiguration of the arrangement of columns. Change in strand design and geometry contributed in reduction of flexural cracking and increasing performance. Elimination of the column is expected to result in economic benefits.