Seismic reliability of low-prestressed self-centering braces considering steel dissipater fracture

Abstract

Low-Prestressed Self-Centering (LPSC) braces are newly developed brace systems which limits both seismic peak and residual deformations, with a low requirement of prestressing forces. These systems utilize ratchet components to minimize the resistance from dissipaters to re-centering systems. Two types of LPSC braces, i.e., Symmetric Hysteresis LPSC (SH-LPSC) brace and Tension-Only LPSC (TO-LPSC) brace, have three common features of their steel dissipaters: 1) occupy a small portion of the entire brace; 2) slender; 3) made by carbon-steel. These characteristics denote a new challenge, that the seismic elongation demand (which cumulates in cyclic loadings) might exceed their limited capacity of steel dissipaters. To secure the use of LPSC braces, this study focuses on evaluating the seismic reliability of LPSC braces considering the fracture of steel dissipaters. First, the elongation capacity of carbon-steel dissipaters, which was adopted in previous studies, and stainless-steel dissipaters, which was proposed, were experimentally investigated. Then, numerical models for both LPSC systems were developed and used to calculate the elongation demand of LPSC systems under mainshocks and mainshock-aftershock sequences through nonlinear dynamic analyses. Based on the numerical results, a mathematic model was developed to predict the elongation demand of steel dissipater. Furthermore, the seismic reliabilities of the two LPSC systems with carbon- and stainless-steel dissipaters were investigated by comparing the elongation demand of steel dissipaters against their capacity in a probability manner. Results indicate that SH-LPSC systems have a higher reliability than TO-LPSC systems because it has lower probability of steel dissipaters fracture at certain drifts. When carbon-steel dissipaters were used, LPSC systems showed a high fracture likelihood, particularly under mainshock-aftershock sequences (15.29 % for SH-LPSC and 27.92 % for TO-LPSC systems). Conversely, stainless-steel dissipaters consistently exhibited near-zero fracture probabilities. Overall, adopting stainless-steel dissipaters substantially reduces brace failure risks, thereby enhancing the seismic reliability of LPSC braces.