Energy demands for seismic design against low‐cycle fatigue

Abstract

A seismic design procedure that does not take into account the maximum and cumulative plastic deformation demands that a structure is likely to undergo during severe ground motion could lead to unsatisfactory performance. In spite of this, current design procedures do not take into account explicitly the effect of low-cycle fatigue. Based on the high correlation that exists between the strength reduction factor and the energy demand in earthquake-resistant structures, simple procedures can be formulated to estimate the cumulative plastic deformation demands for design purposes. Several issues should be addressed during the use of plastic energy within a practical performance-based seismic design methodology.The results in this paper were obtained from the dynamic response of single-degree-of-freedom (SDOF) systems having elastic-perfectly-plastic behaviour and 5% critical damping. The conclusions and design expressions offered have been established by considering systems with period of vibration (T ) ranging from 0.2 to 5.0 s. The dynamic response of these systems was established using Newmark's integration method with constant acceleration.Four sets of ground motions are considered, three of them corresponding to the Los Angeles (LA) urban area and one corresponding to Mexico City. The ground motions for LA, established for the FEMA/SAC Steel Project [11], were grouped in sets of 20 motions as follows: design earthquake for firm soil with 10% exceedance in 50 years (LA 10in50), design earthquake for ENERGY DEMANDS FOR SEISMIC DESIGN Assume max = f (judgement), and b = f (detailing) 2Determine T Determine T 3Estimate max = f (T, u , b) Estimate u = f (T, max , b) 4Estimate

UNA MEDIDA DE INTENSIDAD SÍSMICA BASADA EN UN PARÁMETRO PARA CARACTERIZAR LA FORMA ESPECTRAL DENOMINADO Np

“…Los movimientos sísmicos de banda angosta tienen la característica especial de afectar considerablemente estructuras específicas en un corto intervalo de periodos (especialmente, estructuras que sufren por ablandamiento o con periodos estructurales cercanos al periodo del suelo). De hecho, estos registros demandas grandes cantidades de energía a las estructuras comparados con movimientos de banda ancha (Terán y Jirsa, 2007). Un caso especial donde se generan este tipo de movimientos corresponde a la zona del lago de la ciudad de México.…”

Hysteretic Energy Demand in SDOF Structures Subjected to an Earthquake Excitation: Analytical and Empirical Results

“…Another major advantage of energy-based approach is that the structural resistance and the earthquake effect in terms of energy are basically uncoupled since input energy is a quite stable response parameter and hardly depends on hysteretic characteristics of the structure. Accordingly, there have been extensive attempts for estimating earthquake input energy [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42].…”

Influence of Low-Cycle Fatigue and Corrosion Phenomena on the Ductile Behaviour of Steel Reinforcing Bars

“…Modern codes allow the development of significant plastic phenomena in specific structural elements during severe seismic excitations, causing the deterioration of the structural properties especially if deformations overpass the elastic limit. The failure of primary structural elements, as a consequence, can happen for strain levels lower than the ones corresponding to the collapse limit, condition generally known as "lowcycle fatigue" [4].…”

“…Many works were presented in the current literature dealing with the evaluation of the effective seismic demand on different kinds of structures and sub-structures [4,6,7,8,9,10,11,12] but in general, no information were provided about the effective ductility demand on steel reinforcing bars, in terms of both strain level and energy dissipation. In their work, Barrera et al [13] presented the results of experimental tests executed on r.c.…”