Inelastic Design of Infilled Frames

Abstract

This paper describes a new method of analysis and design for steel frames with concrete or masonry infilling walls subjected to in-plane forces. The method is based on data generated from previous experiments as well as results from a series of nonlinear finite-element (NLFE) analyses. The method accounts for elastic and plastic behavior of infilled frames considering the limited ductility of infill materials. The proposed method predicts the strength and stiffness of infilled frames as well as the infill diagonal cracking load. The method also allows for the major practical imperfections, such as lack of fit and shrinkage ofthe infil!. Variations, such as infill aspect ratio and beams having different strength and stiffness from the columns, are accounted for and it is concluded that the behavior of frames with pin or semirigid joints can also be predicted. The method is further developed to model multistory infilled frames as braced frames, replacing the infills by equivalent diagonal struts.

Comparative Assessment of Strut Models for the Modelling of in-Plane Seismic Response of Infill Walls

“…The strength predicted by Panagiotakos and Fardis [19] is, on the average, higher than the actual one, while the other models ( [17,18]) underestimate the infill strength. Concerning the stiffness, none of the models reproduce satisfactorily the actual values.…”

“…It is noted that: strength values predicted by Panagiotakos and Fardis [19] are higher than the actual (experimental) ones; the model proposed by Paulay and Priestley [15] and Priestley and Calvi [16] is almost unbiased; the other models tend, on the average, to underestimate the infill strength. The highest and the lowest coefficients of determination are obtained, considering the whole dataset, using the formulation proposed by the Decanini and Fantin [14] and Saneinejad and Hobbs [17], respectively. The comparison between predicted and experimental lateral stiffness is made considering the reduced database.…”

“…The equation suggested by Paulay and Priestley [15], which gives a conservative value of the width, is recommended for a lateral force level of 50% of the ultimate capacity. The value suggested by Saneinejad and Hobbs [17] is related to the attainment of the resisting loads R cc and R dc . The formula reported in FEMA 306 [18], which was initially proposed by Mainstone [21], was found suitable for the estimation of the infill secant stiffness if the masonry elastic modulus in the horizontal direction is used [19].…”

“…Panagiotakos and Fardis [19] = 1.3 In the analytical method developed by Saneinejad and Hobbs [17] all failure modes are considered. In equations 9 to 12 (Table 2), is the load factor and ′ is depicted in Figure 1.…”

Empirical-Based Infill Model Accounting for in-Plane/Out-of-Plane Interaction Applied for the Seismic Assessment of Ec8-Designed Rc Frames

“…OOP acceleration can produce infills' collapse by their overturning, which is a great risk for life safety as well as an obstacle to escape/rescue operations during seismic emergency [2]: in this sense, the OOP collapse of infill walls is associable to the attainment of the Life Safety Limit State (LS). A great number of experimental and analytical works concerning the IP behaviour of URM infills is available in literature ( [3][4][5][6], among many others) and some analytical and experimental works have been proposed about their OOP behaviour, especially in recent years ( [7][8][9][10][11][12][13][14][15], among others), and concerning the IP-OOP interaction phenomena, i.e., the effects of IP actions on the OOP behaviour and vice versa. For instance, several authors showed through analytical and experimental studies how the IP displacement demand affects the OOP response of infills in terms of capacity and demand acting on them.…”