Performance of Steel Buildings with Pretensioned Steel Cable Braces under Seismic Loading

Abstract

Concentric braced frames are one of the most effective measures for controlling damages induced by earthquakes in buildings. In compression, conventional concentric hot-rolled steel braces buckle under seismic loading, which leads to catastrophic failure of buildings. The buckling in hot-rolled braces develops pinched hysteresis behavior, which leads to a lag in the total energy capacity. This limitation of hot-rolled steel braces drives the present study to use pretensioned steel cables as braces in concentric braced frames. The performance of the proposed self-balancing pretensioned steel cable braces system is assessed by comparing it with conventional concentric braces utilizing stocky hot-rolled steel braces. Two types of steel cables are used in this study: a self-balancing pretensioned steel rope brace system and a self-balancing pretensioned spiral strand steel cable brace system. A total of 57 models (19 each for hot-rolled steel braces, spiral strand steel cables, and steel ropes) are analyzed in SAP 2000 and are designed following Indian standards, maintaining a constant ultimate compressive capacity of the braces in all systems. The performance in all systems (hot-rolled steel braces, spiral strand steel cables, and steel ropes) is examined by total strain energy capacity, fundamental time period, base shear demand, interstory drift, self-centering capabilities under maximum considered earthquakes, and section size of members. On average, the total strain energy capacity of the steel rope system is enhanced by 1.5 and 2 times that of the spiral strand steel cables and hot-rolled steel brace systems, respectively. Similarly, the base shear demand in steel rope system is reduced by 13% and 39.2% of the spiral strand steel cables and hot-rolled steel brace systems, respectively. Pretensioning in cables eliminates brace buckling and ensures the system’s self-centering capability. Finally, a design guideline for the self-balancing pretensioned steel cable braces system following Indian standards is proposed.