Experimental validation of steel post-tensioned connections with web hourglass pins

Abstract

In this paper, a new self-centering beam-tocolumn connection is proposed. The connection uses post-tensioned high-strength steel bars to provide self-centering capability and carefully designed EDs that consist of steel cylindrical pins with hourglass shape. The proposed EDs: 1) have superior energy dissipation and fracture capacity; 2) are placed between the upper and the bottom flanges of the beam so that they do not interfere with the composite slab; and 3) can be very easily replaced if damaged. A simplified performancebased procedure was used to design the proposed connection. The connection performance was experimentally validated under quasi-static cyclic loading. The specimens were imposed to drift levels beyond the expected design ones in order to identify all possible failure modes. The experimental results show that the proposed connection exhibits stable self-centering behavior by eliminating residual drifts, sufficient energy dissipation capacity, and, strength and stiffness comparable to those of a conventional moment connection. In addition, repeatable tests on a connection specimen were conducted along with replacing damaged EDs. These repeatable tests show that the1 INTRODUCTIONConventional ductile steel moment-resisting frames (MRFs) are currently designed to form a global plastic mechanism under strong earthquakes through the development of plastic hinges at the end of beams and at the base of the columns (Eurocode 8 2004). This design approach provides well known advantages such as acceptable behaviour able to protect human life, economy, low base shear force and controlled total floor accelerations. However, plastic hinges in structural members involve significant cyclic inelastic deformations and local buckling which result in difficult to inspect and repair damage as well as residual drifts. Therefore, conventional steel MRFs result in socio-economical losses such as damage repair costs and loss of building use or occupation after a major seismic event. In addition, they may result in building demolition due to the complications associated with repairing large residual drifts.