Influence of P-Delta Effect on Ductility and Vulnerability of SMRF Steel Buildings

Juan Carlos Vielma Pérez,Manuel Antonio Cando Loachamín

doi:10.2174/1874149501509010351

Abstract

Current earthquake-resistant procedures prescribe generic values for the response reductions factors, regardless of the configurational characteristics of the designed buildings. It is well know that these response reduction factors values reflect the expected behavior of the structures when they are under strong ground motions, being this seismic behavior usually evaluated through ductility and over-strength. In this work calculated values of the ductility of special moment-resisting steel frames with different span lengths and designed according the Ecuadorian Construction Code are presented. Results show that the buildings’ ductility is strongly influenced by the spans length and they would reach inadequate values if the second-order effect P-Δ occur, and then indicating that the structures are more vulnerable than structures not affected by P-Δ effect.

Highlights

The procedures used for the seismic assessment of structures are usually based on the comparison of the coefficients which characterize the response and led to determine whether the behavior is adequate or not [1, 2]
In order to know the influence of the P-Δ effect in structures with different spans lengths, it is useful to process the results of non-linear analysis
6131 6132 6161 6162 6231 6232 6261 6262 6331 6332 6361 6362 c) 6.00. These design factors must be revised in order to guarantee the structural safety of buildings located in high seismic-prone countries, as is the case of Ecuador. It has been presented in this work a brief summary of a procedure for the determination of the yield and ultimate displacements, necessary to compute the value of ductility

Summary

INTRODUCTION

The procedures used for the seismic assessment of structures are usually based on the comparison of the coefficients which characterize the response and led to determine whether the behavior is adequate or not [1, 2]. Among the main coefficients used the ductility is the most important It is computed from the pseudo-static non-linear analysis (Pushover analysis) from this Equation [3]:. In the Methodology of FEMA P695 [6] this coefficient has received special attention, introducing a new approach in which the ductility μT is formulated based in the structural period, according to: μT. For the specific case of moment-resisting steel framed structures, in which the excessive displacements produced by the structural flexibility under lateral forces may introduce second-order effects like the P-Δ effect, it is important to pay special attention to the determination of the displacements required for the ductility computation. Ductility is an important coefficient for the seismic characterization and in order to determine the vulnerability of structures. Special a comprehensive study of the P-Δ effect is presented

THE P-Δ EFFECT

Criterion Used for the Ultimate Displacement Determination

ARCHETYPES STUDIED

Acceleration-based lp

RESULTS

CONCLUSION