Effect Of Infill Panels Research Articles

Effects of Infill Panels with Various Configurations on the Non-Linear Dynamic Responses of Reinforced Concrete Structures

Abstract: This study presents the effects of including infill panels on the non-linear dynamic response of a hypothetical reinforced concrete frame when subjected to an earthquake. Infill panels are represented by equivalent diagonal struts using three different configurations, i.e., single, double with three different connection locations with the beams, and triple struts. The main goal is to determine the simplest and most appropriate representation of the infill panels by analogous struts. The effect of panel sizes on the non-linear dynamic response of the structure is also presented in this work. The main results showed that including infill panels in the analysis reduced the natural period, roof displacement, and story drift ratio, increasing the roof acceleration and shear forces at the structure base. Utilizing the triple model and the double strut joined at the midspan of the beams showed a good agreement with those using the complete infill model.

A sub-assembly based technique for calibration of numerical models of infilled r.c. frames according to experimental tests

Most existing buildings in the Mediterranean area suffer from structural deficiencies and need to be retrofitted. However, a proper selection of the seismic upgrading technique stems from a reliable assessment of seismic response based on accurate numerical models. Furthermore, it is widely accepted that the effect of infill panels should be considered to properly reproduce the seismic response of buildings with r.c. framed structure. Indeed, several studies have demonstrated that infill panels significantly increase the lateral stiffness of the frame and influence its dissipative capacity and collapse mechanism. Unfortunately, despite all buildings are endowed with infill panels, the contribution of these non-structural elements to the structural response has been often “conservatively” neglected, in favour of computational simplicity. In this framework, this paper presents a technique for calibration of the finite element numerical model of r.c. frames with infill panels based on the results of a quasi-static cyclic experimental test of a prototype infilled frame. The proposed technique is based on a sub-assembly approach and relies of the fact that (1) the response of the system is mainly governed by the infill panel for small amplitude displacements, while (2) it becomes coincident with that of the bare r.c. frame for large amplitude displacements. Hence, the mechanical properties of the bare frame and those of the infill panel could be separately extracted from the same cyclic response of the infilled frame. This technique has been here applied for the calibration of the numerical model of a one-bay one-storey r.c. frame with infill panel. A full-scale cyclic test of the infilled frame is also executed and the obtained structural response is assumed as target to be fitted.

Effects of Base Isolation and Infill Panels on the Nonlinear Time History Analysis of Reinforced Concrete Building

This paper presents the predicted results of nonlinear time history analysis of 11 storey (G+10) Reinforced Concrete (RC) residential building under the effects of a strong earthquake. The paper includes studying the effects of using Lead Rubber Bearings (LRB) as base isolators to improve the performance of RC building to sustain the impact of an earthquake. It also includes the effects of the infill panels on the overall dynamic response of both fixed base and base-isolated buildings subjected to a strong earthquake. The main results that are presented in this study include the variation of roof acceleration, roof displacement, base shear with time. The effects of using LRB and including the infill panels on the storey drift are also presented. Maximum reduction in the story drift was obtained when infill panels are included in the analysis of the base isolated building. The inclusion of the infill panels has only marginal effects on the variation of roof displacement with time when the building is isolated by LRB. The main important improvements that emerged from using LRB as well as the infill panels in the analysis are the reduction of inelastic energy and upgrading the elastic one that is summed up along the period of the earthquake.

Influence of soil\u2013structure interaction on seismic pounding between steel frame buildings considering the effect of infill panels

The present research aims to study the influence of the soil–structure interaction (SSI) and existence or absence of masonry infill panels in steel frame structures on the earthquake-induced pounding-involved response of adjacent buildings. The study was further extended to compare the pounding-involved behavior versus the independent behavior of structures without collisions, focusing much on dynamic behavior of single frames. The effect of SSI was analyzed by assuming linear springs and dashpots at the foundation level. The infill panels were modeled using equivalent diagonal compression struts. The steel frames were assumed to have elastic–plastic behavior with 1% linear strain hardening. The dynamic contact approach was utilized to simulate pounding between the adjacent buildings. Nonlinear finite element analysis was performed for two adjacent multi-story structures with four different configurations representing cases that can exist in reality. The seismic response of the studied cases generally emphasized that ignoring the soil flexibility and/or the contribution of the infill panels may significantly alter the response of adjacent structures. This may result in a false expectation of the seismic behavior of buildings exposed to structural pounding under earthquake excitation.

Seismic pounding behavior of multi-story buildings in series considering the effect of infill panels

The aim of the present paper is to study the influence of the infill panels on the seismic pounding response of adjacent structures in series. The contribution of the masonry infill has been simulated using equivalent diagonal compression struts. Steel frames have been assumed to have elastic-plastic behavior with 1% linear strain hardening. The dynamic contact analysis has been utilized where contact surface model (target and contactor) has been applied without any connectors between the adjacent buildings. Nonlinear finite element analyses have been conducted on different configurations of infill distribution throughout the structures. The results of the analysis reveal that the existence of infill panels can substantially change the seismic behavior of the structures and may have a serious influence on their behavior during exposure to mutual pounding under seismic excitation. Moreover, the distribution of infill throughout the structure can significantly affect its behavior during earthquakes.

Experimental tests and global modeling of masonry infilled frames

The effects of infill panels on the response of r.c. frames subjected to seismic action are widely recognized. Numerous experimental investigations were effected and several analytical models were developed on this subject. This work, which is part of a larger project dealing with specific materials and structures commonly used in Italy, discusses experimental tests on masonry and samples of bare and infilled portals. The experimental activity includes tests on elemental materials, and 12 wall samples. Finally, three one-bay one-story reinforced concrete frames, designed according to the outdated Italian technical code D.M. 1996 without seismic details, were tested (bare and infilled) under constant vertical and cyclic lateral load. The first cracks observed on the framed walls occurred at a drift of about 0.3%, reaching its maximum capacity at a drift of 0.5% while retaining its capacity up to a drift of 0.6%. Infill contributed to both the stiffness and strength of the bare reinforced concrete frame at small drifts thus improving overall system behavior. In addition to the experimental activities, previously mentioned, the recalibration of a model proposed by Comberscue (1996) was evaluated. The accuracy of an OpenSees non linear fiber based model of the prototype tested, including a strut element was verified through a comparison with the final experimental results. This work has been partially supported by research grant DPC-ReLUIS 2014.

Comparative Study on the Effects of Infill Walls on Reinforced Concrete Frame Structures

Based on the quasi-static test of single-layer, two-bay RC frame model, using DIANA finite element program, a finite element Macro-model of masonry-infilled frame structure was established, and nonlinear finite element analysis of frame structures filled with different masonry materials was conducted. As a result of the existence of infill walls, the failure modes of frame structure have been changed, and which is easy to cause shear failure at the top of frame columns. If masonry materials of infill walls are different, the effects of infill panels on frame structures will be different. Comparative analysis shows that the influence of clay bricks is the largest, followed by autoclaved bricks’ influence, while aerated concrete blocks’ influence is the smallest. Therefore, to avoid the associated failure mechanism caused by infill walls, lightweight masonry materials are suggested to be used in actual engineering.

Free and Forced Vibration Analysis of an Infilled Steel Frame: Experimental, Numerical, and Analytical Methods

Structural frames with masonry infill panels make up a significant portion of the buildings constructed in earthquake-prone areas prior to the developing of the seismic design standards. In this paper, the effects of masonry panels on the vibration response of an infilled steel-frame building are investigated. Various ambient and steady state forced vibration tests are carried out to realize the dynamic characteristics of the system. 3D finite element models of the building with and without infill panels are provided based on marcomodeling theorem. A set of analytical approximate formulas are also derived to estimate the vibrational period. The natural frequencies of the building are computed using numerical, analytical, and experimental methods. The results show that neglecting the effect of infill panels leads to considerable error. Moreover, it is shown that there is good agreement among the results obtained by the three methods considering the effect of infill panels.

The Effect of Compressed Infill Panels on Cyclic Performance of Exterior Beam-Column Joints

The confining effect of infill panels on the hysteresis performance of the external beam-column joints has been studied experimentally. Four hinged joints and two rigid joints have been tested under cyclic loading with the interaction of infill panels on both the sides of the joints. The infill panels have remained subjected to different compression loads applied either at centre or at the end positions of the infill panels. This effect of infill panels has shown an increase with the increase in amount of compression load. The cyclic evaluation of hinged joints with infill panels has been used to determine the shear resistance of infill panels which has not only depended upon the amount but also on the location of compression load. It has been observed that the load-deformation diagrams of rigid beam-column joints with infill panels manifest a significant increase in the capacity of the joint by confining the joint with infill panels. The obtained capacity has almost been the result of the combined effects of two independent systems, ie. bare rigid joint system and compressed infill panel system.

Implementation and verification of a masonry panel model for nonlinear dynamic analysis of infilled RC frames

The effect of infill panels on the response of RC frames subjected to seismic action is widely recognised and has been subject of numerous experimental investigations, while several attempts to model it analytically have been reported. In this work, the implementation, within a fibre-based Finite Elements program, of a double-strut nonlinear cyclic model for unreinforced masonry panels is carried out. The adequacy of the model in predicting the cyclic/seismic response of multi-storey infilled reinforced concrete frames is then verified through comparisons against experimental results.

Seismic analysis of infilled reinforced concrete frames

This paper presents a numerical method for the analysis of infilled frames subjected to earthquake excitation. The method is based on the concept of equivalent struts used to idealize the infill panels. Properties of the mathematical model are determined using the stiffness matrix method. Dynamic equations of motion are solved numerically in the time domain using the modified step-by-step linear acceleration method known as the Wilson-θ method. The above procedure is implemented into a computer program SAPF (Seismic Analysis of Plane Frames) to be run on an ICL computer. The program has many capabilities such as mesh automatic generation, static, dynamic and spectrum analysis. This program has been used to solve 13 cases of bare and infilled frames in order to assess the effect of different factors such as the presence and continuity of infill panels, the height of the structure, infill material, panel rectangularity ratio and width of the equivalent strut. Results show that infill panels have a great effect on the behavior of such structures. A comparison of this method with existing seismic code formulae showed that the latter overestimate the shear forces in the building due to the fact that they do not consider the effect of infill panels.