Comportamiento Sísmico De Edificios Con Base en Marcos Dúctiles De Concreto Reforzado Con Contraventeo Chevrón

Abstract

RESUMENSe presenta un estudio en que se evalúa, mediante análisis dinámicos no lineales paso a paso, el comportamiento sísmico de edificios de diferentes alturas (ocho, 15 y 24 niveles) estructurados con base en marcos dúctiles de concreto reforzado con contraventeo metálico tipo chevrón. Los edificios se diseñaron para tres diferentes zonas (zona costa del estado de Guerrero y zonas IIIa y IIIb del lago del Distrito Federal), de acuerdo a la altura de cada modelo. De los resultados expuestos, es posible concluir que si se emplean conceptos de diseño por capacidad, así como parámetros de diseño específicos al sistema estructural considerado, es posible obtener capacidades de deformación y sobrerresistencia adecuados, así como un desempeño estructural satisfactorio.Palabras Clave: marcos dúctiles contraventeados; contraventeo chevrón; marcos de concreto reforzado; diseño por capacidad; análisis dinámicos no lineales; desempeño estructural ABSTRACTIn this paper the authors summarize the results of a study devoted to evaluate, using nonlinear dynamic analyses, the seismic behavior of ductile moment-resisting reinforced concrete concentric braced frames structures (RC-MRCBFs) using chevron steel bracing (eight, 15 and 24 stories in height). RC-MRCBFs were assumed to be located in three different soil conditions in Mexico (coastline zone of the state of Guerrero and lakebed zones IIIa and IIIb of Mexico City). From the results obtained, it is possible to conclude that if capacity design principles and specific design parameters for the new design of RC-MRCBFs are used, suitable global ductility capacities and overstrength demands are obtained, and a satisfactory structural performance is achieved.

Nonlinear behavior of code-designed reinforced concrete concentric braced frames under lateral loading

“…This methodology, which is briefly described here and presented in detail elsewhere [28], explicitly takes into account the sequence for designing resisting elements in order to warrant the expected collapse mechanism: (1) bracing elements, (2) beams, (3) columns, (4) connections between the frame and the bracing system and, (5) panel zone (joint area). The axial force transmitted from the bracing system to connections, columns, as well as to the beams subjected to such forces because of the bracing configuration, is addressed in this design procedure, something that it is not currently addressed properly in RC building codes.…”

“…Therefore, depending on how slender the member is, the effective buckling stress may slightly increase or may slightly decrease. In addition, increasing f y diminishes the effective buckling length for the bracing as well [28].…”

“…This effect can also be observed in Table 2, in which the strength variation in columns across the analysis for all models is also reported for the overstrength case. The phenomenon mentioned becomes less evident as the height of the models decreases, as well as when the lateral shear strength provided by the reinforced concrete columns of the frame increases [28]. It is worth noting that limit states reported in Table 2 are defined as follow: (a) Elastic response: it corresponds to a load-step in which the behavior of the lateral shear-drift curve is still elastic, (b) First yielding: it corresponds to a load-step where the first yielding occurs in a beam or a column, or when the first inelastic deformation occurs in a brace element, (c) First plastic hinge: it corresponds to a loadstep in which the rotation capacity (beams or columns) or the buckling length (braces) is exceeded for the first time, (d) Collapse: it corresponds to a load-step in which the theoretical collapse mechanism of the structure was formed.…”

“…For simplicity, lateral load distributions selected to perform the pushover analyses were based upon the fundamental mode of vibration for all models. This was done to have a general framework of comparison, taken into account that: (a) building height ranges from 4 to 24 stories, (b) the modal mass associated to the fundamental mode is higher than 70% for most of the buildings with ductile behavior (Table 1) and, (c) RC-MRCBF's have a relatively large lateral stiffness and, therefore, higher mode effects have a reduced impact, as demonstrated by Godínez-Dominguez [28] when comparing the results obtained with pushover analyses based upon the fundamental mode with those obtained with modal pushover analyses as presented in the literature [36,37].…”

“…Storey and global lateral shear vs drift curves were obtained for all the described models [28]. The curves obtained for the eightstory, sixteen-storey and twenty four-storey models are shown in Figs.…”