Evaluation of Performance Levels and Response Modification Factors for Prestressed Reinforced Concrete Frames Using Nonlinear Pushover Analysis

Abstract

The use of different methods of prestressing systems is very common in gravity frames at the present time. This technology can also be used in lateral load resisting frames. In addition to ordinary moment frames, this technology can be used in intermediate and special moment resisting frames. The use of post-tensioned prestressed slabs as primary members of the seismic load resisting load path in special moment resisting frames is not permitted based on available codes. The use of prestressed beams in special moment resisting frames includes some limitations. In this study, after the design of special prestressed moment frames with prestressed beams and slabs using conventional methods, considering special seismic design criteria, nonlinear pushover static analysis has been carried out in order to investigate performance levels and vulnerability of this type of frames. After performing nonlinear static analysis, target displacement of desired frames has been calculated and the plastic hinges formation sequence and related acceptance criteria for these hinges is investigated. Also, in order to study the effect of prestressing on seismic behavior of special prestressed moment resisting frames, response modification factor and related seismic parameters of this type of frames are obtained. Finally, all the above steps are repeated for the corresponding reinforced concrete special moment resisting frames, and the results were compared with prestressed frames. The obtained results show that in addition to applying restrictions on the use of prestressed beams in special moment resisting frames, target building performance levels and structural performance levels are acceptable, compared to reinforced concrete frames. Higher ductility factor and response modification factor has been achieved for prestressed frames compared to reinforced concrete frames and the base shear at yield strength for this type of frames are considerably lower than the similar value for reinforced concrete frames.

Keywords

• prestressed concrete special moment resisting frame
• performance levels
• plastic hinge
• nonlinear static analysis
• target displacement
• response modification factor