Post-Tensioned Self-Centering System Efficiency against Extreme Wind Loads

For tall buildings, wind demand under extreme wind loads is so large that design based on conventional elastic behavior can be difficult. A practical solution is to permit inelastic behavior to introduce hysteretic damping and reduce design wind force. There-fore, the inelastic behavior of structures subject to wind loads should be thoroughly investigated. The presumption is that applica-tions currently applied in inelastic seismic design can be employed in inelastic wind design of concrete buildings. In this research, behaviors of elastic, bilinear, and self-centering single-degree-of -freedom systems under along-wind load were studied for various design wind speeds using nonlinear time-history analysis. Self -centering systems-in particular, unbonded post-tensioned concrete systems-given their wide use and high potential and flexibility for self-centering behavior, were found to have smaller maximum displacement than bilinear systems, with differences being consid-erable at higher wind speeds. Results found highlight the role of post-yield stiffness in reduction of maximum displacement. Self-centering systems were also found to be highly influenced by reverse-yielding values. Systems with reverse yield strength equal to the standard deviation of the elastic force (approximately 20% of [mean + background + resonant components]) demonstrated minimum displacement. In addition, design parameters such as ductility, overstrength, and displacement factor are reported for inelastic design based on the concept of a response modification factor.