Reliability of buildings in service limit state for maximum horizontal displacements

Abstract

Brazilian design code ABNT NBR6118:2003 - Design of Concrete Structures - Procedures - [1] proposes the use of simplified models for the consideration of non-linear material behavior in the evaluation of horizontal displacements in buildings. These models penalize stiffness of columns and beams, representing the effects of concrete cracking and avoiding costly physical non-linear analyses. The objectives of the present paper are to investigate the accuracy and uncertainty of these simplified models, as well as to evaluate the reliabilities of structures designed following ABNT NBR6118:2003[1&] in the service limit state for horizontal displacements. Model error statistics are obtained from 42 representative plane frames. The reliabilities of three typical (4, 8 and 12 floor) buildings are evaluated, using the simplified models and a rigorous, physical and geometrical non-linear analysis. Results show that the 70/70 (column/beam stiffness reduction) model is more accurate and less conservative than the 80/40 model. Results also show that ABNT NBR6118:2003 [1] design criteria for horizontal displacement limit states (masonry damage according to ACI 435.3R-68(1984) [10]) are conservative, and result in reliability indexes which are larger than those recommended in EUROCODE [2] for irreversible service limit states.

Numerical-experimental study of neighboring wind effects on tall buildings related to serviceability via reliability

“…where x δ and y δ are displacements in the x and y directions respectively (m); x a and y a are accelerations in the x and y directions respectively (m/s 2 ); lim δ = annual limit displacements; and lim a = annual limit accelerations. In this study, lim δ , for 1-year return period, assumes the value of H/1700, based on NBR 6118 [31] and Corelhano et al [32], and H/1370 based on Huang et al [33], being H the total height of the building. The term lim a , for 1-year return period, is worth 0.084 m/s 2 , recommended by ISO 10137 [34] for residences, and 0.048 m/s 2 based on NBR 6123 [25].…”