RC Infill Walls Research Articles

Performance of channel shear connectors in steel frame with reinforced concrete infill walls

To examine the mechanical properties of channel shear connectors employed in steel frame with reinforced concrete infill wall (SRCW) structures, the improved push-out tests were performed on three specimens of channel shear connectors subjected to the monotonic and cyclic loading. This study investigated the influences of loading protocol and concrete strength on the mechanical behavior of channel shear connectors. After the refined finite element (EF) models of channel shear connectors were validated based on the push-out tests, a systematical parametric analysis was conducted to evaluate the effects of RC infill wall thickness, concrete strength, and channel dimensions on its shear strength of the channel shear connectors. In addition, this study also compared the accuracy of the CSA S16, AISC 360 and GB50017 design code in predicting the shear capacity of channel shear connectors in SRCW structures. The experimental results and parametric studies indicated that the current design equations inaccurately evaluate the shear capacity of channel shear connectors used in SRCW structures. Consequently, an alternative equation was developed to estimate the shear-resistant capacity of channel shear connectors in SRCW structures, which provided the desirable calculation precision for engineering design.

Cyclic behavior and pushover analysis of large scale two-bay, two-story reinforced concrete frames infilled with walls with openings

This study presents experimental results on the seismic behavior of a large-scale two-bay, two-story RC frame with RC infill walls, including openings typical of low-rise RC row buildings in Taiwan. The test findings indicated that the specimen failed due to the failure of the vertical members of the first story. Specifically, the critical wall segments located between openings and between an opening and a boundary column and short columns resulting from the presence of these openings were shown to be the main contributors to the failure. Based on the observed phenomenon during the test, an analytical model was verified and proposed for the tested specimen’s pushover analysis. The selection of plastic hinges in the analytical model was determined according to the Taiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA). Pushover analysis performed by commercially available software indicated that the analytical model could well capture the specimen's behavior regarding peak base shear, initial stiffness, displacement of each story, and development of plastic hinges.

Response of steel frame filled by prefabricated RC infill walls with eccentric opening: Experimental study

A steel frame filled by prefabricated RC infill wall (SFRCW) is an effective lateral load-resisting system wherein RC infill walls are embedded inside. The presence of eccentric opening (EO) such as door or window usually significantly reduces the lateral stiffness and strength. In order to accurately evaluate the effect of the EO on the seismic performance of the SFRCW structure, the cyclic quasi-static tests on two, 1/3-scaled, two-story, single-span SFRCW-EO specimens were performed. Both specimens showed the shear-dominated failure mode, moderate ductile behavior, and pinching hysteretic feature. The concrete cracks were induced from the corners of the EO and were attributed to stress concentration phenomena. The initial lateral stiffness was approximately 50 kN/mm, overall ductility ranged from 2.48 to 2.95, and the overstrength factor reached 2.5. The interface slips and separations between RC infill wall and surrounding steel frame in SFRCW-EO specimens were considerably tiny that could be neglected. The flushed end-plate connection, which had the enough rotation capacity and tension-resisting capacity, was an effective partially-restrained (PR) connection used in the SFRCW-EO. The overall seismic behavior of SFRCW-EO was weaker compared to that of the steel frame with solid RC infill walls because it failed by serious concrete crush. In addition, the on-site assembly was more convenient for the SFRCW-EO specimen. Further, strengthening measures such as the use of an embedded beam were essential for ensuring the integrity of infill walls and improving their overall seismic behavior.

Test, Analysis, and Seismic Design Approach of RC Infill Walls Isolated by PVC Tubes in Coupled Shear Wall Systems

Test, Analysis, and Seismic Design Approach of RC Infill Walls Isolated by PVC Tubes in Coupled Shear Wall Systems

Nonlinear numerical parametric study of the number and arrangement of dowels connecting the wall to the bounding frame for the seismic strengthening of RC frames with RC infill walls

Nonlinear numerical parametric study of the number and arrangement of dowels connecting the wall to the bounding frame for the seismic strengthening of RC frames with RC infill walls

Numerical simulation of RC frames infilled with RC walls for seismic strengthening of existing structures

Although it is evident that the RC infill wall is an economic and practical way to improve the lateral strength of framed structures and a retrofitting method for existing buildings to withstand earthquake loads, there are still a lot of limitations regarding their application. Codes do not provide any guidance for their design and detailing or specific regulations for their interaction with the bounding frame. Furthermore, specific directions do not exist for the modelling or evaluation of frame bays converted into RC walls, depending on the type and details of the connection. A representation of the real behaviour of the wall and its interaction with the bounding frame during an earthquake is necessary to provide more accurate guiding information. For this aim, numerical models of this structural system were developed and are presented in this paper. The experimental results of the project SERFIN, which was a full-scale four-storey model tested with the pseudo-dynamic method at the ELSA facility of the Joint Research Centre in Ispra, were used to calibrate the numerical models. Two-dimensional (2D) frames were modelled in DIANA FEA, and nonlinear transient analyses were performed to simulate the experimental results obtained from the SERFIN full-scale experiment. In this paper, the FE model simulation of the test specimen is presented along with a comparison between the experimental results and the numerical ones. It was concluded that the developed numerical models capture effectively the behaviour of the studied structural system and can be used for parametric studies to examine the effects of the number of dowels on the behaviour of the system and propose design guidelines based on the results of the parametric study.

Study of effect of shear wall in the seismic response of the existing buildings

In Iraq, it has been observed that an increase in seismic activity, and that most existing buildings are not seismically designed and that can suffer serious damage or collapse, thus causing loss of life. In this paper, a numerical simulation of the experimental laboratory sample on the subject of non-seismically designed buildings and methods of strengthening them was performed using a seismic strengthening technique using an infill RC wall in order to maintain the risk of earthquakes. This study was carried out through the work of verifying the numerical and practical model by matching the results of laboratory work with the results of numerical analysis using the analysis finite element analysis method (FEAM) by Abaqus CAE 2019 software and then using the model to study the effect of openings in the infill RC walls and the extent of its impact on the response of the building. The practical model is a full four-story building tested laboratory in Elsa, Italy using pseudo dynamic test (PSD). The experimental model is a sample of not seismically design buildings (gravity design only) and ways to improve them by adding new RC walls with different contact details to the existing building. The goal of the experimental test was to study the effectiveness of adding RC infill walls with two types (North and South) infill RC walls, including designing it and the contribution of two types of dowels that connect the new infill walls to the existing RC building. In other words, it’s a way of strengthening by converting selected bays into RC walls with two types of reinforcement and connection between new infill RC walls and existing builders called (north and south) frames. The results of analytical modeling show that the percentage of differences in X- Direction of top story displacement between Abaqus software and Experimental tested at ELSA results are 2.47% in positive and 3.12% for negative X direction, which refer to a very good similarity and accurate building simulation.

Nonlinear Finite Element Analysis of the Seismic Retrofitting of Existing Buildings

Finite Element Analysis (FEA) is a helpful tool for finding solutions to civil engineering problems. In this paper, the numerical analysis was performed by simulating an experimental test by using FEA tools, Abaqus /CAE2019 was used to develop and retrofit solutions to sustain existing structures for seismic hazard. The 3D building was modeled, and nonlinear analysis was adopted. This experimental building was tested at the Joint Research Centre (JRC) of the ELSA facility that is in Ispra-Italy. This model was a building of a full-scale four-story tested using the pseudo-dynamic (PsD) techniques. The retrofitting model was done by adding new RC walls with different connection details to the existing building. This building corresponding in gravity design only. The goal of the experimental test was to study the effectiveness of adding RC infill walls as retrofitting method, including designing it and the contribution of dowels that connect the new infill wall to the existing RC building. In other words, it is a strengthen method carry out by conversion of selected bays into new infilled RC walls. The results of analytical modeling of the RC structure in the Abaqus software show that the percentage of differences of X- Direction in top story displacement between Abaqus software and Experimental tested at ELSA results are 2.47% in positive and 3.12% for negative X direction, which refer to a very good similarity and accurate building simulation.

Seismic performance of RC frames strengthened by RC infill walls

This study presents the shake-table tests of a 1/5-scaled RC frame retrofitted with RC infill walls. The intensity of input ground motions increased gradually to comprehensively evaluate the structural seismic behavior. We performed a comparison of the results from the RC frame with masonry walls and that with RC walls. The results showed that the presence of RC infills effectively improved the lateral structural stiffness and loading capacity of the frames and reduced their damage and story drift. RC walls acted as the first seismic line of defense, and their failure was dominated by bending failure and concentrated on the low stories. The displacement ductility of the structure decreased with increasing stiffness of the introducing infills.

Evaluation Seismic Response for Soft Storey Building Retrofitted with Infill, Steel Bracing and Shear Wall

Open ground construction is quite prevalent from last 25 years in metropolitan India. Buildings with open ground stories are to be particularly exposed to collapse, and severe damage under earthquake excitation. Although, many buildings constructed in recent times have been observed adverse effect during Bhuj earthquake. The study has been performed to work out the performance of RC building with open ground storey subjected to seismic loads. In present work, twelve storied building are taken into account and the performance of structure evaluated by using pushover analysis in SAP 2000 software. The analytical results discussed in the nature of capacity curve, structure performance point and plastic hinge development pattern. Result indicated that, there are formations of plastic hinges at ground storey column level. To counteract the total collapse of soft storey structures, there is need to retrofit the open storey. Therefore, the alternative measures are recommended to get better the reaction of soft storey like RC shear wall, steel bracing, and infill wall.

Seismic performance analysis of multi-story RC frames strengthened with RC infill wall

Seismic performance of RC frame structures was investigated by creating 3-D models of the frame with additional solid RC infill wall along the height of Honolulu Building prescribed in FEMA design examples. Layered-shell element (LSE) was used to model the infill wall and gap element was introduced at the interface between the wall and the bounding frames. The modelling technique was validated against test results reported in the literature prior to its application on the 12 story building. The push over curves of all models were compared to obtain the most efficient model that conform to the strength and stiffness requirement of the seismic codes of Indonesia. The results showed that the non-linear behaviour of RC frame with RC infill wall can be modelled accurately using LSE and gap element. The RC wall addition improved the strength, stiffness and performance of the frame significantly. The most efficient model was that with infill wall up to the first 4 story levels in which, the performance of the structure improved from collapse prevention to immediate occupancy.

Response of RC Frames Strengthened by RC Infill Walls: Experimental Study

AbstractThe experimental results of a research program on the response of 1/3-scale reinforced concrete infilled frames are presented and evaluated. The main objective was to assess the seismic per...

Experimental and numerical study on the hysteretic behavior of composite partially restrained steel frame-reinforced concrete infill walls with vertical slits

The work presented in this study aimed to investigate the hysteretic behavior of composite partially restrained (PR) steel frame-reinforced concrete infill walls (PSRCW) with vertical slits, which consisted of a PR steel frame, a slit-reinforced concrete (RC) infill wall, and shear connectors. An experimental program at one-third scale of a one-bay by three-story PSRCW with vertical slits was tested under horizontal cyclic loading. The seismic behavior was examined in terms of the lateral load-carrying capacity, ductility, deformability, lateral stiffness, and energy dissipation. The results showed that this kind of structure exhibited superior ductility and deformability, as well as excellent energy-dissipation capacity. The slit RC infill walls exhibited flexure-dominated behavior and significantly increased the lateral load-carrying capacity. In contrast, the slit RC infill walls decreased the rotation demand on the PR connections from earthquake, which avoided the fracture failure of the beam-to-column connection. Additionally, the test results were verified, and relative parametric analyses of PSRCW with vertical slits were conducted by using a simplified macro fiber model to illustrate the factors that influence the structural hysteretic behavior.

COMPARISION OF INTERNATIONAL CODES FOR STEEL ANCHORS DETAILS USING IN SEISMIC STRENTHENING

Having poor seismic performance reinforced concrete frame must be strengthened to reach sufficient seismic performance. The main factor that affects the seismic performance, designing and application of the anchor dowels in the connection zone of infill shear wall and weak reinforced frame. Connection between the frame and the infill wall are usually achieved by using dowels that are placed in the holes drilled into inner faces of the frame members, and fixed by a resin. In this study, the design and detailing guidelines for the design of the post-installed anchors in TEC (2007), ACI 318, JCI (2001) and IS15988 have been compared. According to the results, in ACI 318-14, the shear capacity of anchors is effected by embedment depth, anchor bar diameter, concrete strength, strength of the bar and edge distance. In TEC-2007, shear strength is affected only by two properties of the anchor bar: strength and diameter. JCI-2001 design code considers the two factors outlined in TEC-2007 and concrete strength. Based on the comparison conducted in this study, there are insufficient guidelines in TEC-2007 for the design and detailing of anchor bars that are typically used as connection between an existing frame and new RC infill wall.

Numerical simulation of the experimental results of a RC frame retrofitted with RC Infill walls

The effectiveness of seismic retrofitting of RC-frame buildings by converting selected bays into new walls through infilling with RC walls was studied experimentally using a full-scale four-storey model tested with the pseudo-dynamic (PsD) method. The frames were designed and detailed for gravity loads only using different connection details between the walls and the bounding frame. In order to simulate the experimental response, two numerical models were formulated differing at the level of modelling. The purpose of this paper is to illustrate the capabilities of these models to simulate the experimental nonlinear behaviour of the tested RC building strengthened with RC infill walls and comment on their effectiveness. The comparison between the capacity, in terms of peak ground acceleration, of the strengthened frame and the one of the bare frame, which was obtained numerically, has shown a five-fold increase.

Field investigation on severely damaged aseismic buildings in 2014 Ludian earthquake

The 2014 magnitude 6.5 Ludian earthquake caused a death toll of 617, many landslides and tens of thousands of collapsed buildings. A field investigation to evaluate the damage to buildings was carried out immediately after the occurrence of the earthquake. Severely damaged aseismic buildings, which were basically observed in the downtown of Longtoushan Town, were carefully examined one by one with the aim to improve design codes. This paper summarizes the damage observed to the investigated aseismic buildings in both the structural and local levels. A common failure mode was observed that most of the aseismic buildings, such as RC frame structures and confined masonry structures, were similarly destroyed by severe damage or complete collapse of the first story. The related strong ground motion, which was recorded at the nearby station, had a short duration of less than 20 s but a very large PGA up to 1.0 g. The RC frames based on the new design codes still failed to achieve the design target for “strong column, weak beam”. Typical local failure details, which were related to the interaction between RC columns and infill walls and between constructional columns and masonry walls, are summarized with preliminary analyses.

Research on the Connection Modes and Numerical Simulation Methods of RC Frame and Infill Wall

In the evaluation of the seismic performance of masonry-infilled RC frames, the main difficulty is determining the type of interaction between the infill and the frame, which has a major impact on the structural behavior and load-resisting mechanism. This paper addresses the connection modes of the RC frames and masonry panels in regulations in China. The method of flexible connection suggested in standard has not been widely used in actual engineering, and rigid connection was adopted in universal. The finite element model with interface element is advisable for simulating the interaction of the frames and panels, and the accuracy of the nonlinear finite-element models has been evaluated with experimental data. The comparison of the numerical and experimental results indicates that the models can successfully capture the highly nonlinear behavior of the physical specimens and accurately predict their strength and failure mechanisms.

Appraisal of masonry infill walls effect in the seismic response of RC framed buildings: A case study

In the last few decades, the scientific community has been extensively involved in the investigation about the interaction between infill masonry walls and RC frames in the seismic structural behavior, both for new and for existing buildings. With respect to this issue, some extensions of the N2 Method have been proposed in order to evaluate the contribution of masonry infill to the structural response. This paper presents an extensive case study regarding the analysis of an existing RC framed building located in a high seismic risk area in Calabria (Southern Italy), for which the project, dated back to the early ‘70s, provided only the presence of vertical loads. In order to collect the data required for the application of the safety assessment procedure and achieve the necessary knowledge level, a broad experimental test campaign was performed on the building in order to assess the condition and quality of both RC elements and infill walls. A number of non-linear static (pushover) analyses were performed on proper structural models of the building, considering both the bare framed structure and the infilled one, in order to appraise the influence of infill walls on the failure mechanisms. In particular, a sensitivity analysis was performed by assigning different Partial Safety Factors (PSF) to the mechanical parameters of infill walls, in order to investigate their effect on the overall structural response of the building.

Cyclic behavior of partially-restrained steel frame with RC infill walls

In order to investigate the behavior of partially-restrained steel frame with RC infill wall (PSRCW), two specimens with one-third scale, one-bay, and two-story were performed under reversed cyclic lateral load, where one specimen was with concealed vertical slits in the infill walls and another specimen with solid infill walls. Test results showed that both specimens obtained enough lateral stiffness for controlling drift and yielded enough strength appropriate for resisting lateral load. PSRCW with solid infill walls exhibited moderate ductility capacity and energy dissipation due to the degradation of post-peak strength. PSRCW with concealed vertical slits exhibited much larger ductility, deformability, and energy dissipation capacity than the other one. Once concealed vertical slits were crushed, infill walls behaved as a series of flexural columns provided fairly ductile response and stable cyclic performance. PSRCW with concealed vertical slits can improve post-peak strength degradation considerably. In addition, damaged PSRCW structure subjected to earthquake is easy to be repaired, through knocking off the heavy crushed infill walls and recasting concrete infill walls. This is another advantage of this composite structure.

A non-linear masonry infill macro-model to represent the global behaviour of buildings under cyclic loading

The presence of masonry infill walls in RC buildings is very common. However, and even today, in the design of new buildings and in the assessment of existing ones, these infill walls are usually considered as non-structural elements and their influence in the structural response is generally ignored. For horizontal loading, infill panels can drastically modify the response, attracting forces to parts of the structure that have not been designed to resist them. This paper presents an improved non-linear numerical simulation model for the influence of the masonry infill walls in the seismic behavior of structure. The model is implemented in the PORANL program. After the implementation and calibration of the proposed masonry model, a series of non-linear dynamic analyses of a building representative of Modern Architecture in Europe were carried out. The main objective was to investigate the behavior of this type of building, and any weakness under seismic loading. The building geometry and the dimensions of the RC elements and infill walls were set in the original project, and confirmed in the technical visits. The building under study has nine storeys and the structure is mainly composed of 12 plane frames oriented in the transversal direction. The building was analyzed with a simplified plane model, for each direction, and the existing infill panels were looked at in accordance with their dimensions and location. The earthquake action adopted in this study was simulated through three series of artificially generated earthquakes, for a medium/high seismic risk scenario in Europe.