Reinforced Concrete Infill Wall Research Articles

Seismically resistant progressive collapse behavior of infilled frame structures under seismic loads and column loss: A numerical investigation

This research investigated the seismic performance of multi-story reinforced concrete (RC) frames with infilled walls. The study employed a two-step numerical approach: first, a verification process ensured the model's accuracy by comparing it to past experimental results. Following validation, a parametric study explored various factors influencing the frames' behavior. These factors included the number of stories (3, 6, and 12), the earthquake ground motion (Vrancea, El Centro, and Kahramanmaraş), and the effect of removing an internal column. Additionally, the study examined the impact of incorporating polypropylene (P.P.) fibers into different parts of the structure: the RC frame itself, the mortar between infill wall bricks, or both. The findings revealed significant improvements in seismic performance due to the presence of infill walls. In the three-story frame, the wall reduced plastic drift by a remarkable 98.9 %. Furthermore, strengthening with P.P. fibers demonstrated exceptional effectiveness. For example, on the first floor of the three-story frame, the maximum drift value dropped from 0.751 to a 0.004 for the IRCPM model (fibers in the infill wall mortar only) and even lower (0.003) for the IPPM model (fibers in both the RC frame and infill wall mortar). These results highlight the potent ability of P.P. fibers to improve earthquake resistance. The study also assessed the efficacy of strengthened infill walls as partial replacements for lost columns. When an internal column was removed, the presence of a P.P. fiber-reinforced wall (IPRCL model) helped mitigate the structural impact, reducing the base shear force by 11 % compared to the control model without fibers (CIRCL). Similar trends were observed in taller frames. While including fibers in the RC frame of the 6-story model with a removed column resulted in an 11 % decrease in base shear force, models with fibers in the wall components of the 12-story frame exhibited a 31.62 % increase in base shear force after column removal.

Bidirectional seismic performance and design approach of RC infill wall with PVC tubes

In some regions, masonry infill walls are replaced by cast-in-situ reinforced concrete (RC) infill walls to effectively solve problems such as leakage, long construction periods, and high out-of-plane vulnerabilities. However, these high-stiffness RC infills impose excessively high constraints on the adjacent structural components, leading to disadvantageous seismic responses. Therefore, a flexible connection is required to isolate the infill walls and main structures. However, flexibly connected RC infill walls are not widely used in practical engineering because they are weakly supported by relevant standards and codes and have an insufficient calculation basis, especially for evaluating out-of-plane seismic properties. This study considers a type of RC infill wall with a common layout of polyvinyl chloride (PVC) tubes for coupled shear wall systems. The in-plane and out-of-plane seismic performances of the system are studied using quasi-static loading tests and finite element analysis, respectively. The system exhibits satisfactory seismic properties during the test because the PVC tubes provide effective flexible isolation. Out-of-plane pushover analysis and bidirectional loading are successively simulated with different parameters to study the out-of-plane reliability of the infill walls with and without openings. Finally, a seismic design approach for such infill walls, considering both in-plane and out-of-plane resistances, is proposed and validated using novel and concise design formulas. The accuracy of the design approach is verified using finite element calculations.

Evaluation of progressive collapse resistances of RC frame with contributions of beam, slab and infill wall

This study aims to present practical calculation models to predict the deformation capacity and the progressive collapse resistance of reinforced concrete (RC) frames for design purpose. It is well known that beams, floor slabs and infill walls have significant contributions to progressive collapse resistance of RC frame structures. Considering contributions from RC beams, floor slabs and infill walls, calculation models are proposed based on the summary of available experimental phenomena and data in existing studies. It is shown that the proposed calculation models give acceptable predictions to experimental and numerical data, which can be used as alternative methods for evaluations of RC frame structures in the collapse-resistance design.

Experimental quantification of seismic damage for RC infill walls using static and dynamic loading test

In Taiwan, the reinforced concrete (RC) infill walls are often used for exterior and interior walls in general buildings. Due to the higher lateral stiffness and strength of the RC infill walls, it is necessary to understand the residual seismic capacity of RC infill walls damaged by an earthquake. To quantify the post-earthquake residual seismic capacity of RC infill wall members, experimental data for 6 wall specimens with shear failure are used to obtain the residual seismic capacity of damaged RC infill members for specified damage levels in this work. Different from the previous static loading test research, dynamic loading is also used to evaluate the residual seismic capacity of RC infill wall members. Besides the experiment data, the reduction factors of strength and stiffness for damaged RC infill wall members with and without horizontal interface slippage are also investigated, respectively. Finally, the modified method of the mechanical properties of RC infill walls corresponding to damage levels is proposed, and verified by using the strength development curve of the test data of damaged specimens. Restated, following the proposed seismic damage quantification method and mechanical properties of damaged RC infill walls, their residual seismic capacity can be considered in the pushover analysis.

Seismic Performance and Collapse Safety Assessment of Post-Tensioned Hybrid Precast Concrete Infill Wall-Frames and Comparison with Reinforced Concrete Infill Wall-Frames

ABSTRACT Post-tensioned hybrid (PH) precast concrete wall-frame buildings provide excellent seismic performance, by reducing structural damage and residual drifts. In the present study, the use of PH precast concrete walls, as partial infill walls in low-rise reinforced concrete (RC) moment-resisting frames is evaluated and compared with RC infill wall (RIW) frames with a similar structural configuration. For this purpose, the seismic performance and collapse safety of 4-story post-tensioned hybrid precast concrete infill wall (PIW) frames and RIW frames with different frame shear ratios are studied. Following the FEMA P695 methodology, fragility curves are generated, the collapse margin ratio is determined, and then the adjusted collapse margin ratio of each frame is compared with acceptable adjusted collapse margin ratio . The results indicate that, peak normalized floor displacements, inter-story drifts, and the column chord rotation demand of the PIW frames are for the most part slightly larger than the corresponding RIW frames but the PIW frames show better seismic performance in reducing the residual inter-story drifts than RIW frames, under design earthquake level and risk-targeted maximum considered earthquake level ground motions. Although a slight decrease in the is observed with increasing , for both PIW and RIW frames, exceeds the indicating that the PIW frames show satisfactory collapse performance.

Study on the seismic performance of retrofitted RC frames with RC infill wall mega braces

This paper proposes a novel arrangement of RC infill walls made possible by RC infill wall mega braces (RCIWMBs). The seismic behavior of a reinforced concrete (RC) frame structure retrofitted by the RCIWMB was investigated through 1/5-scale shaking table tests. The seismic damage characteristics and the dynamic responses of the model structure under different input ground motions are presented in detail. The results show that the presence of the RCIWMB has a slight effect on the failure of beam-column joints, but it can lead to punching shear failure of its connected frame columns. When the RC walls are arranged diagonally, the RCIWMB can form a macroscopic brace effect, serving as the first seismic line of defense. Compared with traditional RC infill wall retrofitted frame structures, the drawback is obvious failure, which appears on the lower stories of this novel type of structure and is prone to forming a weak story. This indicates a poor structural story ductility and more severe damage to the integral structure. However, the addition of the RCIWMB resulted in a substantial increase in the integral lateral bearing capacity, integral lateral stiffness and integral ductile behavior, a decrease in lateral displacement, and a reduction in damage to the original frame structure. The novel structural system performed better under extensive seismic tests, providing a new method for upgrading the seismic performance of existing buildings.

Comparison of seismic performances of reinforced concrete frames strengthened by different techniques

The aim of this study is to compare the seismic performances of strengthening techniques applied to reinforced concrete (RC) non-ductile frames tested under the effects of seismic loads. In the experimental part of the study, one-third scale, one-bay, two-storey non-ductile hollow brick infilled RC frames were strengthened with five different techniques and tested under reversed cyclic lateral loads. One being reference, five of the frames were infilled with hollow bricks and plastered on both sides, one was strengthened with plain mortar, one was strengthened with steel fiber reinforced mortar, two were strengthened with precast RC plates. The last frame was strengthened with RC infill wall. Strengthening techniques increased strength and stiffnesses of the frames in the ranges from 57% to 189% and from 186% to 486% respectively. In the numerical analysis part, an existing RC non-ductile building located in Istanbul, strengthened with the techniques, were analyzed using a computer program. Numerical results were evaluated in terms of interstorey drift ratio together with the overall seismic performance of the building.

Behavior of reinforced concrete frame with masonry infill wall subjected to vertical load

The effectiveness of masonry infill wall on behavior of a Reinforced Concrete (RC) frame subjected to a column failure is studied experimentally. For this reason, one full scale RC frame designed according to Eurocode is statically tested to investigate the behavior of the frame with and without masonry infill wall. The obtained results show that infill wall can significantly increase the load carrying capacity of RC frame and thus serve as an important robustness reserve in the case of unpredictable extreme events (i.e. local impact, blast or earthquake). A photogrammetry analysis is carried out to study the behavior of the structure. Results give valuable information about the alternative load path, transfer of the applied load to the column and beams, and interaction forces between RC frame and infill wall. At the end, the experimental program is simulated by the OpenSees software to study the behavior of the frame. After having demonstrated that this model can predict the load deflection with good accuracy, a parametric study is conducted to evaluate the effect of the percentage of longitudinal reinforcement ratio of beams and columns on the load carrying capacity of the infilled RC frame.

An effective simplified model of composite compression struts for partially-restrained steel frame with reinforced concrete infill walls

To resolve the issue regarding inaccurate prediction of the hysteretic behavior by micro-based numerical analysis for partially-restrained (PR) steel frames with solid reinforced concrete (RC) infill walls, an innovative simplified model of composite compression struts is proposed on the basis of experimental observation on the cracking distribution, load transferring mechanism, and failure modes of RC infill walls filled in PR steel frame. The proposed composite compression struts model for the solid RC infill walls is composed of α inclined struts and main diagonal struts. The α inclined struts are used to reflect the part of the lateral force resisted by shear connectors along the frame-wall interface, while the main diagonal struts are introduced to take into account the rest of the lateral force transferred along the diagonal direction due to the complicated interaction between the steel frame and RC infill walls. This study derives appropriate formulas for the effective widths of the α inclined strut and main diagonal strut, respectively. An example of PR steel frame with RC infill walls simulating simulated by the composite inclined compression struts model is illustrated. The maximum lateral strength and the hysteresis curve shape obtained from the proposed composite strut model are in good agreement with those from the test results, and the backbone curve of a PR steel frame with RC infill walls can be predicted precisely when the inter-story drift is within 1%. This simplified model can also predict the structural stiffness and the equivalent viscous damping ratio well when the inter-story drift ratio exceeds 0.5%.

Cyclic Tests of Steel Frames with Concealed Vertical Slits in Reinforced Concrete Infill Walls

AbstractExperimental testing revealed that installing concealed vertical slits in reinforced concrete (RC) infill walls enabled the RC infill walls to behave in a more ductile manner (as compared t...

Numerical simulation of RC infill walls under cyclic loading and calibration with widely used hysteretic models and experiments

Addition of reinforced concrete (RC) infill walls into the structural system has been a commonly preferred strengthening technique within the last decades for seismic rehabilitation of RC frames. As a consequence, generating a representative numerical model of an RC infill wall has become an important issue. As the initial step of this study, measured structural responses of two selected well-known large-scale RC infill wall experiments subjected to displacement controlled cyclic loading are taken into account. Later, by calibrating the numerical model prepared in Perform-3D computer program utilizing fiber cross-sections, a practical and a compatible analytical model is obtained and proposed herein. Structural systems of the experiments are mathematically modeled by elements consisting of vertical and horizontal fiber layers to represent the bending/axial behavior and to control the out of plane displacements, respectively. Nonlinear behavior of the reinforcing steel is represented by a tri-linear backbone curve without strength degradation, while a multi-linear hysteretic behavior considering the strength loss is utilized for the structural concrete. Furthermore, those recently conducted experiments are simulated by a couple of widely used hysteretic models for comparative purposes, which are preferred in most cases by the researchers during the analytical investigation of RC structures, so that their adequacy for reflecting the nonlinear behavior of infill walls are also studied. It is shown with comparisons for the experimentally measured and the analytically derived results that the calibrated mathematical model proposed herein is more compatible with the measured values than the widely used hysteretic rules for capturing the behavior of these types of frames retrofitted by RC infill walls under reversed cyclic loading. Although numerical simulations are carried out for a limited number of tests and it is assumed that sufficient amount of anchoring dowels is provided at the interface of the existing frame and the RC infill, the proposed calibrated model conforms to both experiments’ measured responses by means of seismic behavior for not only the undamaged single bay frames converted to the RC infill wall, but also pre-damaged multi-bay strengthened structures, which include structural deficiencies like low concrete strength, inadequate stiffness and insufficient confinement.

Investigation of Ductility Reduction Factor in Seismic Rehabilitation of Existing Reinforced Concrete School Buildings

Converting existing Reinforced Concrete (RC) frames into RC infill walls is one of the most efficient seismic strengthening technique due to its simplicity in application providing high rigidity, stability and strength in structures. On the other hand, this method affects the seismic behavior of existing RC structure in terms of the energy dissipation capacity or in other words, ductility reduction factor, Rμ. This research is an attempt to investigate the RC infill wall ratio effect on ductility reduction factor in terms of the seismic rehabilitation of the typical RC school buildings. For this purpose, nonlinear static pushover analyses are conducted for existing 3 and 5 story RC school buildings which were rehabilitated with different RC infill wall ratio. Numerical analyses are carried out by using the fiber element based modeling approach in the software, Perform-3D. Based on these analytical results, correlation between the ductility reduction factor and the RC infill wall ratio is obtained for the seismic rehabilitation of the RC school buildings. In addition, two mathematical expressions for the variation of the ductility reduction factor with RC infill wall ratios are proposed in terms of the preliminary seismic rehabilitation assessment of the existing RC school buildings.

변형경화형 시멘트 복합체의 인장성능에 따른 끼움벽의 내진성능

이 논문에서는 비내진상세 골조의 손상완화능력 향상을 위한 연구의 일환으로 변형경화형 시멘트 복합체 끼움벽의 내진성능을 실험적으로 평가하였다. SHCC의 인장변형능력 및 균열거동 특성이 끼움벽의 전단 거동에 미치는 영향을 구명하기위해 총 3개의 끼움벽 실험체를 제작하여 반복하중 하에서 실험을 실시하였다. 이 연구에서 사용된 시멘트 복합체의 종류는 콘크리트와 SHCC로 하였다. SHCC는 인장 특성에 따른 영향을 검토하기위해 PVA1.3%+PE0.2% 및 PVA0.75%+PE0.75%로 두 종류의 배합조건을 갖도록 계획하였다. 끼움벽의 균열손상 발생 부위를 중앙부로 유도하기위해 모든 끼움벽 실험체의 좌·우측면에 100 mm 깊이의 노치를 설치하였다. 실험 결과, SHCC 끼움벽의 경우 철근 콘크리트 끼움벽에 비해 우수한 균열제어성능을 나타냈으며, 최대하중 도달 시점에서의 층간변위 또한 높게 나타났다. 특히, 초기 경사균열 발생 이후에도 SHCC 내의 보강 섬유간 섬유가교작용에 기인하여 완만한 강성 저하 양상을 나타냈다. 게다가 끼움벽의 균열폭을 기준으로 손상 식별 단계를 분석한 결과, PIW-SHD 실험체가 PIW-SLD 실험체에 비해 약 3배에 해당하는 우수한 내진성능을 나타냈다. 또한 대각 보강근의 변형률 진전 양상을 비교한 결과, 우수한 균열분산 특성에 기인하여 철근에 집중되는 인장응력을 SHCC 매트릭스가 일정 부분 부담하는 것으로 나타났다.

Experimental study on separating reinforced concrete infill walls from steel moment frames

In a multistory building frame, stiff reinforced concrete (RC) infill walls may be terminated above the first story for architectural purposes, which may create a soft-first-story structure. To eliminate this detrimental situation, this paper proposes to separate the RC infill wall from the steel moment frame by slits. An experimental program of four one-bay-by-one-story steel moment frame specimens along with pushover analyses of multistory frame models were presented to validate the proposed idea. This study conducted cyclic loading tests on a total of four moment-resisting-frame specimens, which included one bare frame; one with ordinary RC infill wall; and two with side slits between RC wall and frame members. Furthermore, pushover analyses of multistory frame models with soft first story configurations were also conducted to illustrate the effect of RC infill walls with or without slit separation. Both experimental and analytical results showed that the stiff RC infill wall dominated the lateral resistance and drift capacity of the test specimens, and that by adding slit-separated features at the edges of infill walls improved the drift capacity. It is concluded that the slit-separated features can be a viable option to eliminate the soft-story problem caused by vertically irregular configuration of RC infill walls.

Experimental and Analytical Analysis of RC Frames Strengthened Using RC External Shear Walls

In this study, we have investigated the application of an external RC shear wall as a method of improving the performance of reinforced concrete (RC) frames in an earthquake. We produced a series of eight RC frames, each of which was modeled at a 1/3 scale with two floors and two spans. These frames were of the same size and had design and construction deficiencies commonly encountered in the RC buildings in Turkey. We tested four of the eight frames without any strengthening, under reversed cyclic lateral loadings resembling earthquake loads. The remaining four frames we tested under the same conditions after strengthening them with RC external shear walls. We arranged the axial force loads applied to the columns of the test models in two different ways to result in tensile and compression failure. The test results were analyzed on the basis of a comparison using static push over analysis. The results of the experimental tests and analytical studies showed that the RC external shear wall improved the seismic character of the existing RC frame as much as RC infill walls, therefore this method can be used as an alternative strengthening method. Also, the method provides effective, practical and economical strengthening that minimizes the need for additional works and does not restrict the use of the RC building.

Strengthening of deficient RC frames with high strength concrete panels: an experimental study

An economic, structurally effective and practically applicable strengthening technique was developed for reinforced concrete (RC) framed buildings. The idea of the technique is to convert the existing hollow brick infill wall into a load carrying system acting as a cast-in-place RC infill wall by bonding relatively thin high strength precast concrete PC panels to the plastered hollow brick infill. For this purpose, a total of eight one-third scale, one bay, one story frames were tested under reversed-cyclic lateral loads. Test frames were designed and constructed with common deficiencies observed in practice. Four different panel types were used for strengthening. Test results showed that both strength and stiffness of the frames were significantly improved by the introduction of PC panels. Experimental results were compared with the analytical approaches suggested by the authors.