A SIX-STRUT MODEL FOR NONLINEAR DYNAMIC ANALYSIS OF STEEL INFILLED FRAMEs

Abstract

A two-dimensional computational model for infill walls is presented. The behavior of an infill wall is prescribed by a strength envelope and a hysteretic loop equation which provide smooth continuous curves. The infill is idealized with six compression-only inclined struts, which follow the behavior defined by the strength envelope and hysteretic loop equations. Three parallel struts are used in each direction, and the off-diagonal struts are located to represent the interaction between the infill and confining steel frame at locations along the beam-column spans where plastic hinges have been observed to form. The advantages of this analytical model are the following: (a) both strength and stiffness degradation of infill walls are modeled; (b) the parameters of the model have physical meaning and can be readily adapted to fit experimental data; (c) the off-diagonal struts allow modeling of the interaction between the infill and the bounding frame; and (d) local behavior, such as the effects of openings, lack of fit, and interface conditions, can be modeled.

Preliminary analysis of a soft‐storey mechanism after the 2009 L'Aquila earthquake

“…while the remaining stiffness, given by the two off-diagonal struts, can be evaluated by the principle of virtual displacements [10]. If an equal axial stiffness ( 2 k and 3 k ) is assumed for the off-diagonal struts, than 23 k( k k )  depends on the infill stiffness K and on the axial stiffness of the central strut 1 k according to the following expression:…”

“…Observed damage points to collapse as a result of a brittle failure mechanism. Given the likely scenario collapse inferred by observed damage, an analytical model of the building was built up taking into account nonlinear behavior of the infills; local interaction with columns was also considered by means of a three strut macro-model [10,11,12]. Two parametric hypotheses based on Italian code [13] prescriptions were assumed for infill mechanical properties.…”

Seismic Design of Masonry and Reinforced Concrete Infilled Frames: A Comprehensive Overview

“…Chrysostomou et al (2002) proposed the use of three compression parallel struts, as depicted in Fig.10a for modeling the strength and stiffness degradation of masonry infill walls in steel frames. The properties of the three struts are calculated by means of the principle of virtual work and it is assumed that the central strut deteriorates faster than the two outer struts.…”

Inelastic Response of Masonry Infilled Reinforced Concrete Structures

“…A significant bracing action, affecting both the strength and stiffness, originates by this mechanism, as demonstrated by a large number of experimental investigations [1][2][3][4][5][6][7][8][9][10][11][12][13] and analytical-numerical studies [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. However, despite several modelling strategies available in the literature, going from pinned equivalent struts macromodeling to FE micromodeling [33][34][35][36][37][38], masonry infills are generally not accounted for in models because of the large amount of uncertainties arising during their structural identification.…”