Bare Reinforced Concrete Frame Research Articles

An efficient framework for structural seismic collapse capacity assessment based on an equivalent SDOF system

Assessing the structural collapse capacity efficiently and accurately is a key issue in earthquake engineering. Here, an efficient framework for structural seismic collapse capacity assessment based on an accurate equivalent single-degree-of-freedom (ESDOF) system is proposed. The corresponding ESDOF system is calibrated by matching the cyclic static pushover (SPO) curves of a more complex multi-degree-of-freedom (MDOF) system (e.g., high-fidelity finite element models) through a meta-heuristic optimization method. In this way, both the backbone curve and hysteretic characteristics (the stiffness and strength deterioration, and pinching behavior) of the complex MDOF system are considered in the corresponding ESDOF system. Then, incremental dynamic analysis (IDA) is carried out to assess the structural seismic collapse capacity using the ESDOF system instead of the corresponding MDOF system to improve the computational efficiency. The efficiency and accuracy of the proposed framework have been validated through three case studies, including a bare reinforced concrete (RC) frame, a steel frame, and an infilled wall RC frame. These results affirm that the proposed framework can accurately and efficiently assess the collapse capacity of low-rise bare and infilled RC frame structures, as well as steel frame structures.

Determination of the seismic vulnerability of infilled RC buildings according to the Quadrants assessment method

The earthquake vulnerability of the buildings has become more important after significant structural damages due to seismic events. The Quadrants assessment method is one of the effective procedures for the determination of the earthquake performance of the buildings. In this study, the impact of the infill walls on the structural vulnerability of reinforced concrete (RC) buildings was investigated using this method. Five different building models are designed such as bare RC frame, RC frame with strut infill as per field test (open ground story), RC frame with strut infill as per ASCE-41-06 (open ground story), full RC frame with strut infill as per field test (fully infilled), and full RC frame with strut infill as per ASCE-41-06 (fully infilled). All structural analyses were performed using an adaptive pushover analysis in the SeismoStruct software. The infills in the studied RC buildings were modeled as an equivalent strut as per field test or ASCE-41-06 code. The influence of different building models on the performance point, overstrength factor, response reduction factor, and ductility reduction factor was evaluated. The performance point is calculated as per the ASCE-41-06 code which is based on the “displacement coefficient method” and the application of the performance point is used to decide on the intervention/retrofit of RC structures through the “Quadrants assessment method”. In this study, the results depict that the strut width of the infill as per ASCE-41-06 is underestimated as compared to field test. Thus, the impact of the strut width is quantified on the seismic design parameters. It is concluded that there is a need for intervention/retrofit of the bare frame and open ground story RC infilled frame based on the “Quadrants assessment method” due to the absence of infills and the calculated values of the response reduction factor (R) obtained for the infilled RC building models are higher than the bare frame structure due to presence of infills.

Effect of masonry infill on the response of reinforced concrete frames subject to in-plane blast loading

This paper presents a numerical study investigating the effect of masonry infill on the response of reinforced concrete (RC) frames subject to in-plane blast loading. Three-dimensional single-bay single-story masonry infilled reinforced concrete (MIRC) frames were modeled, in which a simplified micro-modeling approach was adopted for the masonry infill. The surface-based cohesive model was employed between the expanded brick units by adopting the traction-separation law. A non-integral modeling approach was considered with an appropriate contact algorithm between the infill wall and bounding RC frame. The dynamic material models with explicit dependency on strain rate were incorporated in the finite element (FE) models and validated against the experimental test data. The developed FE models of bare RC and MIRC frames were subjected to surface blasts with variable scaled distances representing the far-field, near-field, and close-in blasts. The effect of masonry infill on the response of RC frames subject to in-plane blast loading was investigated using the general-purpose FE software ABAQUS without employing user-defined subroutines. The blast response was characterized using displacements, energy dissipation, strain localization and accumulation, stiffness degradation, and damage modes. Results highlight the beneficial influence of masonry infill in reducing the local deformation and altering the failure modes of RC frames subject to in-plane blasts. However, results suggest that the effects of infill on the overall structural response, including axial, flexural, and shear demands, must be considered during the design of bounding RC frames. Furthermore, parametric studies were carried out based on varying masonry bonding patterns and wall thickness, number of bays and stories, and masonry infill heights, and provided conclusive remarks.

Seismic performance of two-story three-bay reinforced concrete frame equipped with K-configured buckling restrained braces

This study presented experimental and numerical investigations into the seismic performance of reinforced concrete (RC) frames equipped with buckling restrained brace (BRB) systems in the central span. The study evaluated the effectiveness of the K-configured BRB system in strengthening the RC frame for engineering construction applications in the seismic region. A 1/3-scaled, three-span, two-story, RC frame was designed in accordance with seismic design requirements and tested under low-reversed lateral cyclic loading. A finite element model of the BRB-equipped RC frame was created using ABAQUS and validated by comparing the numerical and experimental results. The validated model was also modified by removing the BRBs to create the bare RC frame. Seismic behaviors of the bare and RBR-equipped RC frames were numerically examined and compared in terms of failure modes, hysteretic response, ductility, energy dissipation, strength degradation, and stiffness deterioration. The results indicated that the BRB-equipped RC frame achieved a plastic hinge failure mechanism at the beam ends with no severe concrete damage in the supporting columns. Furthermore, the use of the K-shaped BRB in the central span improved the load-carrying capacity by up to 80% and the energy dissipation capacity by up to 50%. Parametric studies were also conducted to investigate the influence of critical design parameters and provide design suggestions for potential improvement in the RC frame's ductility and energy dissipation capacity.

Experimental and numerical studies of improving cyclic behavior of infilled reinforced concrete frame by prefabricated wall panels with sliding joints

This paper aims to introduce a new type of damping infill wall system to alleviate the negative infill-frame interaction of fragile infill walls for reinforced concrete (RC) frames and improve the cyclic behaviors of the entire system. Three tested specimens including specimen BF (a bare RC frame), specimen CWF (an RC frame with ordinary infill walls), and specimen DWF (an RC frame with novel damping infill walls) are designed and fabricated. Quasi-static cyclic tests are conducted to them for exploring and comparing their cyclic behaviors. Experimental results reveal that severe destruction appears upon the conventional infill walls due to the negative infill-frame interaction. On the contrary, no significant cracks or damage are viewed in the new damping wall panels at the inter-story drift ratio of 4.00%. It confirms that the unfavorable infill-frame interaction under horizontal loadings can be mitigated by the developed damping infill systems effectively. The developed innovative infilled RC frame and the bare RC frame exhibit similar cyclic behaviors, including the hysteretic response, loading capacity deterioration, secant stiffness deterioration, and displacement ductility. Furthermore, by using the advanced infill wall system, the RC frame can dissipate energy more efficiently by over 15.71% and ameliorate the degradation of energy dissipation capacity through the stable damping force from the sliding joints. Additionally, numerical models and specimens show similar cyclic behaviors, which testifies to the validity of the pseudo-static experiment and numerical simulation. Parametric results reveal that the influence of developed wall panels made of different strengths of concrete for ameliorating seismic performance of infilled RC frames is very little, whereas the friction factor in the sliding joint is the essential element for enhancing the capacity of infilled RC frames to bear the lateral loadings.

Assessment of seismic retrofitting interventions in reinforced concrete structures

Destruction of reinforced concrete (RC) structures, particularly non-ductile RC structures, in recent earthquakes demonstrate their vulnerability under lateral forces generated in an earthquake. Despite the extensive literature on the subject and the wide variety of strengthening techniques available, there is no consensus on the efficiency of these techniques in improving the seismic performance of RC structures. In this study, a five-storeyed RC-framed building is considered to evaluate its seismic performance through static non-linear pushover analysis. To examine the effect of various cases encountered in practice, the pushover analysis is carried out on the RC frame for various cases, i.e. a bare RC frame, an RC frame with masonry infills but with an open ground storey, and RC frames with shear walls with a variety of thicknesses and steel reinforcement ratios. Further, to investigate the effect of retrofitting, the RC frame is strengthened using local jacketing and bracings. From the results, it is observed that the initial stiffness and base shear of masonry infilled RC frame with an open ground storey exhibit an increase of 2.6%, and 19%, respectively, as compared to the bare frame. The use of shear walls increases the initial stiffness and base shears, and they increase by 6–14% and 8–20%, respectively, with an increase in the reinforcement ratio in the shear wall. Retrofitting with the use of both diagonal bracings causes the base shear to increase by a factor of 7.7 as compared to that of the open ground storey. Finally, the probability of damage to the RC frame in all cases was compared using seismic fragility curves.

A novel seismic strengthening method for RC frames: Precast ultra-high performance concrete braces

A novel bracing method to strengthen the seismic behavior of reinforced concrete (RC) frames was developed in the study. The brace was made using steel reinforced ultra-high performance concrete (UHPC). UHPC is a class of tensile strain-hardening cementitious composites and has ultra-high compressive strength of greater than 120 MPa. To utilize the capacity of the UHPC brace prior to the onset of major inelastic response of the RC frame, a design method for the UHPC brace was established. In the developed strengthening method, the in-situ construction process was simplified by conveniently installing the precast UHPC brace using the UHPC connections that was constructed in-situ to link the UHPC brace to the frame. The performance of the UHPC bracing method was evaluated using cyclic loading tests on two frame specimens, i.e., a bare RC frame and a UHPC brace-strengthened RC frame. The test results showed that the UHPC brace effectively enhanced the initial stiffness, peak strength, and energy dissipation capacity of the original frame. Moreover, it successfully preserved the capacity of the columns when the UHPC brace was active without magnifying the shear demand in the columns. As a result, the strengthening method allowed the original columns to utilize their full force resisting capacity after the capacity of the UHPC brace was depleted. In addition to the experimental study, an analytical model, which was derived based on equilibrium, compatibility, and suitable material constitutive laws, was developed to reasonably evaluate the load-displacement response of RC frames strengthened with UHPC braces.

Seismic performance comparison between reinforced concrete frame structures with and without energy dissipating cladding panel system: Shaking table test and numerical simulation

An energy dissipating cladding panel system (EDCPS) for reinforced concrete (RC) structures, in which the U-shaped steel dampers (USDs) are introduced to connect the main structure and the panel, is proposed, aiming to control and eliminate the damage to the main structure and cladding panels, respectively. To validate the dual damage control effects, 1/2-scale shaking table tests were conducted on RC frames with and without EDCPS. The test results indicated that a satisfactory control effect was realized for the RC frame with EDCPS. The maximum roof displacement and inter-story drift ratio of the RC frame with EDCPS were approximately 20% and 60% lower than those of the bare RC frame under the design basis earthquake (DBE) and maximum considered earthquake (MCE), respectively, where the influence of loading histories was not eliminated. No damage was observed on the cladding panels, which could successfully convert inter-story deformations into shear deformations of the USDs, thus realizing the damage control. Furthermore, a multi-scale simulation method was introduced and validated against the test results with a good accuracy, emphasizing the consideration of loading histories. For the RC frame with EDCPS, the relative differences in the predicted critical responses with and without consideration of loading histories were less than 2.3%. Moreover, for the RC frame without EDCPS, the corresponding relative differences reached 4.0% and 26.8% under the DBE and MCE, respectively. The control effect of the maximum inter-story drift ratio under the MCE ignoring and considering loading histories were 37.8% and 60%, respectively. This research provides valuable experimental data and identifies an effective numerical simulation method for investigating RC structures with EDCPS.

Experimental and numerical study on seismic response of RC frames strengthened by shotcrete sandwich panel infills and CFRP strips

The present study evaluates the utilization of shotcrete sandwich panel (SSP) infill and CFRP strips to strengthen reinforced concrete (RC) frames. To this end, a CFRP diagonal strip-infilled RC frame, an SSP-infilled RC frame, and a control specimen (a bare RC frame) were examined as single-story specimens in terms of the in-plane seismic response. This work compared the specimens in the stiffness degradation, damping, and cyclic lateral response. Also, the available empirical techniques were subjected to performance comparison in the stiffness and capacity calculation of masonry infills for the SSP infill system. The structural performance levels of the system were calculated and compared to the ASCE 41 code. Eventually, numerical analyses were carried out in order to examine the specimens in nonlinear behavior. It was found that the SSP-infill led to a two-fold rise in RC frame strength, even though system stiffness increased. Moreover, the ductility of the infilled frame experienced a 42% improvement in light of the CFRP diagonal strips.

Influence of Masonry Infill on Seismic Design Factors of Reinforced-Concrete Buildings

Infill walls are the most common separator panels in typical reinforced-concrete (RC) frame structures. It is crucial to investigate the influence of the infill walls on the earthquake behavior of RC frames. The load resistance of infill materials was often not taken into account in the designing phase, whereas the infill walls have significant contributions to the structural behavior under lateral and vertical loadings. A three-dimensional 4-story RC building is designed, and in order to make a realistic model, different infill walls configurations were taken into account with the openings in the infill. Four different models were created for structural analysis for infill wall effects, namely, full RC infilled frame (Model I), corner infill at ground story RC infilled frame (Model II), open ground story RC infilled frame (Model III), and bare RC frame (Model IV). Static adaptive pushover analysis has been performed for all structural models by using the SeismoStruct software. The double strut nonlinear cyclic model was used for modeling the infill walls. In this study, three different compressive strengths of infill walls are taken into consideration, and the effects on seismic design factors (namely, the response reduction factor, the ductility, the overstrength factor, and the deflection factor) are calculated. The obtained values of the response reduction factor (R) are compared with the given values in the BIS code. The results show that the R factors of all RC infilled frames are decreased when the compressive strength of the masonry infill reduces. However, the R values of bare frames are less than the corresponding values recommended in the BIS code. It is worth noting that the National Earthquake Hazards Reduction Program (NEHRP) provisions underestimate the deflection factors of the reinforced-concrete (RC) frames according to the evaluated deflection factors of the herein studied RC frames.

In-plane cyclic behaviour of RC frames strengthened with composite sandwich panels

This paper presents an experimental study about the development of a sustainable and multifunctional composite sandwich panel for the rehabilitation of reinforced concrete (RC) buildings from the 1960s to the mid-1980s. For this purpose, the cyclic behaviour of representative RC frames was assessed by performing in-plane quasi-static cyclic tests on three different specimens: (i) a bare RC frame (individual behaviour of the frame); (ii) an RC frame with masonry infill wall (representative of target buildings); and (iii) an RC frame strengthened with an innovative sandwich panel formed by outer wythes in recycled steel fibre reinforced micro-concrete and polystyrene core layer. The results show that, in comparison with the traditional masonry infill wall solution, the proposed rehabilitation solution significantly improved the cyclic performance of the RC frame, reaching higher levels of load carrying capacity (395% vs. 349% increase) and energy dissipation (700% vs. 524% increase). Moreover, the sandwich panel has maintained its structural integrity with low level of damage in its internal load-bearing layer for high values of lateral drift (up to 2.1%).

Advanced Composite Retrofit of RC Columns and Frames with Prior Damages—Pseudodynamic Finite Element Analyses and Design Approaches

This study develops three-dimensional (3D) finite element (FE) models of composite retrofits in deficient reinforced concrete (RC) columns and frames. The aim is to investigate critical cases of RC columns with inadequate lap splices of bars or corroded steel reinforcements and the beneficial effects of external FRP jacketing to avoid their premature failure and structural collapse. Similarly, the RC-frame FE models explore the effects of an innovative intervention that includes an orthoblock brick infill wall and an advanced seismic joint made of highly deformable polymer at the boundary interface with the RC frame. The experimental validation of the technique in RC frames is presented in earlier published papers by the authors (as well as for a four-column structure), revealing the potential to extend the contribution of the infills at high displacement ductility levels of the frames, while exhibiting limited infill damages. The analytical results of the advanced FE models of RC columns and frames compare well with the available experimental results. Therefore, this study’s research extends to critical cases of FE models of RC frames with inadequate lap splices or corroded steel reinforcements, without or with brick wall infills with seismic joints. The advanced pseudodynamic analyses reveal that for different reinforcement detailing of RC columns, the effects of inadequate lap-spliced bars may be more detrimental in isolated RC columns than in RC frames. It seems that in RC frames, additional critical regions without lap splices are engaged and redistribution of damage is observed. The detrimental effects of corroded steel bars are somewhat greater in bare RC frames than in isolated RC columns, as all reinforcements in the frame are considered corroded. Further, all critical cases of RC frames with prior damages at risk of collapse may receive the innovative composite retrofit and achieve higher base shear load than the original RC frame without corroded or lap-spliced bars, at comparable top displacement ductility. Finally, the FE analyses are utilized to propose modified design equations for the shear strength and chord rotation in cases of failure of columns with deficiencies or prior damages in RC structures.

A new method of seismic retrofitting cost analysis and effectiveness for reinforced concrete structures

Modeling, analysis and design of retrofitting interventions has been a topic of numerous research projects that aim in providing answers to complex questions such as “which retrofitting technique is more effective in terms of cost and frame mechanical enhancement?”, and “what is the overall strength enhancement in terms of structural seismic performance?” Therefore, a main purpose of this manuscript is to support decision-making, thus providing a numerical method that can be used to select the optimum retrofit strategy based on the mechanical response of reinforced concrete (RC) structures. The currently available numerical tools for the 3D detailed mechanical limit state study of the structural behavior of retrofitted RC elements are currently bound by numerous numerical and computational constraints, thus are usually implemented at the level of a single structural member under nonlinear or elastic monotonic loading. This work alleviates these constraints through the use of the hybrid modeling (HYMOD) approach [1–3] which is used to develop a finite element model that is numerically validated through the use of a full-scale multistorey RC building that was retrofitted with infill RC walls and carbon fibre reinforced polymer (CFRP) jacketing. Further validation was also performed and presented in this manuscript on joints that foresaw the use of 3 layers of CFRP sheets. The understudy 4-storey RC building, which was experimentally tested under ultimate limit state cyclic loading, was used to develop 24 models that foresaw different retrofitting strategies. Two retrofitting techniques were investigated herein, the CFRP jacketing and the infill RC shear walls, where for the case of the later four different rebar materials were investigated (Steel-, Glass-, Aramid- and Carbon-FRP). In order to determine the optimum cost-effectiveness of each strengthening intervention, an optimum retrofitting cost-effectiveness factor is proposed that takes into account the overall cost of the retrofitting strategy in relation to the respective strength and energy dissipation enhancement that is achieved compared to the initial bare RC frame. Based on the proposed factor and the numerical findings during the seismic assessment of the understudy retrofitting strategies, it was concluded that the use of infill RC shear walls with Aramid-FRP rebars was the most cost-effective strengthening method when both strength and energy dissipation enhancement was within the desired design. For the case where the main objective was the increase of strength (base shear) the use of infill RC shear walls with CFRP rebars was found to be the most cost-effective option. Furthermore, when comparing standard steel-reinforced shear walls with CFRP jacketing, the use of CFRP sheets was found to be more cost-effective in the case where strength enhancement was the main objective. According to the numerical investigation performed herein, more numerical investigation is deemed necessary for the study of the cost-effectiveness of more strengthening methods and seismic isolation systems, where more RC structures and bridges will also be considered.

A Review on the Progressive Collapse Analysis of Reinforced Concrete Frame Structures

The progressive collapse analysis of a reinforced concrete (RC) building occurs when an extreme event arises (vehicle collision, gas explosion, bomb blasts, etc.), which often cause damage to the RC structural frame were a sudden loss of primary structural element takes place or due to the failure of one or more critical structural element leading the structure to partial or entire collapse. The fear of progressive collapse is growing, due to the partial collapse of the 22-story Ronan point apartment in 1968, leading to a gas burst and attacks in Oklahoma City, the Alfred P. Murrah Federal Building in 1995, and the attacks on the world trade center in Lower Manhattan, New York in the year 2001. The trend is now to attain strong buildings which can be operational after such extreme events, especially when the building is occupied by a large number of persons. This paper reviews the progressive collapse study on RC frame structure based on various numerical, analytical, and experimental methods which are reported and discussed in the literature. In comparison with bare RC frame, the advantageous impact of the masonry infill wall on the RC structural frame is summed up against the progressive collapse.

Practitioner-friendly design method to improve the seismic performance of RC frame buildings

Reinforced concrete (RC) frame buildings are a widely used structural system around the world. These buildings are customarily designed through standard code-based procedures, which are well-suited to the workflow of design offices. However, these procedures typically do not aim for or achieve seismic performance higher than code minimum objectives. This article proposes a practical design method that improves the seismic performance of bare RC frame buildings, using only information available from elastic structural analysis conducted in standard code-based design. Four buildings were designed using the proposed method and the prescriptive approach of design codes, and their seismic performance is evaluated using three-dimensional nonlinear (fiber) models. The findings show that the seismic performance is improved with the proposed method, with reductions in the collapse fragility, higher deformation capacity, and greater overstrength. Furthermore, an economic analysis for a six-story building shows that these improvements come with only a 2% increase in the material bill, suggesting that the proposed method is compatible with current project budgets as well as design workflow. The authors also provide mathematical justification of the method.

Numerical studies on the progressive collapse resistance of multi-story RC buildings with and without exterior masonry walls

This paper investigates the influence of perforated masonry walls on the progressive collapse resistance of multi-story reinforced concrete (RC) structures. In this study, bare and infill-wall RC frames are studied by considering column failure at corner and exterior locations. Infill-wall panels are simulated by using equivalent compression struts and their provision of alternate load paths under the removal of a critical load-bearing element is examined. Linear static, nonlinear static, and nonlinear dynamic analyses are conducted by following the General Service Administration (GSA) guidelines. The analysis results show that the infill walls are beneficial in the redistribution of loads after the failure of the column and the collapse resistance of the RC building is increased. Empirical dynamic amplification factors (DAF) are also calculated in the sequel and the factor instructed in the GSA guidelines is judged by comparing with these computed dynamic factors. The results show that the DAF of 2, recommended by the GSA guidelines, is conservative and the presence of infill walls does not significantly affect the value of DAF.

Structural health monitoring of seismically vulnerable RC frames under lateral cyclic loading

The effectiveness and the sensitivity of a Wireless impedance/Admittance Monitoring System (WiAMS) for the prompt damage diagnosis of two single-storey single-span Reinforced Concrete (RC) frames under cyclic loading is experimentally investigated. The geometrical and the reinforcement characteristics of the RC structural members of the frames represent typical old RC frame structure without consideration of seismic design criteria. The columns of the frames are vulnerable to shear failure under lateral load due to their low height-to-depth ratio and insufficient transverse reinforcement. The proposed Structural Health Monitoring (SHM) system comprises of specially manufactured autonomous portable devices that acquire the in-situ voltage frequency responses of a network of twenty piezoelectric transducers mounted to the RC frames. Measurements of external and internal small-sized piezoelectric patches are utilized for damage localization and assessment at various and increased damage levels as the magnitude of the imposed lateral cycle deformations increases. A bare RC frame and a strengthened one using a pair of steel crossed tension-ties (X-bracing) have been tested in order to check the sensitivity of the developed WiAMS in different structural conditions since crack propagation, damage locations and failure mode of the examined frames vary. Indeed, the imposed loading caused brittle shear failure to the column of the bare frame and the formation of plastic hinges at the beam ends of the X-braced frame. Test results highlighted the ability of the proposed SHM to identify incipient damages due to concrete cracking and steel yielding since promising early indication of the forthcoming critical failures before any visible sign has been obtained.

Effect of Different Bracing Systems in Reinforced Concrete Frames under Cyclic Loading

Reinforced concrete (RC) framed structures are widely used as load transferring system in residential and commercial buildings. Even though the RC frames are designed for gravitational and seismic forces, but they are week under severe seismic events. The main disadvantage of the framed structures is inefficient bracing systems designed in it. This investigation is conducted mainly to study the effective bracing system in the RC framed structure to transfer the seismic force. This research aims to study the seismic performance of RC frames influenced by the various types of cross bracings under cyclic loading. The finite element analysis software package ABAQUS is used to investigate the braced RC frames analytically. The research scheme consists of three RC frames; the bare frame, the bare frame with single X-bracing (X frame), double X bracing (D-X frame) along the height. The structural parameters include, load-displacement hysteresis envelope, stiffness degradation and energy absorption were studied to analyze the performance of bracings. The results showed that the X frame and D-X frame noticeably increased the lateral strength, stiffness and energy dissipation properties compared to the bare RC frame. The results also indicated that the addition of X bracing along the height significantly enhanced the structural parameters of the RC frame.

Cyclic behavior of lightly reinforced concrete moment frames with partial- and full-height masonry walls

Existing lightly reinforced concrete (RC) moment frames are vulnerable to earthquakes. The seismic behavior of these frames could be affected by the presence of masonry infill walls. The objective of this study was to investigate the seismic behavior of gravity-designed RC frames having partial- and full-height masonry infill walls. For this purpose, experimental and numerical studies were conducted. Three one-story and one-bay gravity-designed RC moment frames with and without partial- and full-height masonry infill walls were made and tested under cyclic lateral loads. Numerical models for RC moment frames and masonry walls were proposed based on test data. Nonlinear static and incremental dynamic analyses (IDAs) were conducted for three-story RC moment frames with and without partial- and full-height masonry infill walls using the numerical models. Both experimental and numerical studies demonstrated that the masonry-infilled RC frames had larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. The partial-height masonry-infilled RC model frame had the least collapse strength among the frames.

Load-displacement Response of Gravity Load Designed Reinforced Concrete Moment Frames with Various Height of Masonry Infill Walls

Lightly reinforced concrete (RC) moment frames may suffer significant damage during large earthquake events. Most buildings with RC moment frames were designed without considering seismic loads. The load-displacement response of gravity load designed frames could be altered by masonry infill walls. The objective of this study is to investigate the load-displacement response of gravity load designed frames with masonry infill walls. For this purpose, three-story gravity load designed frames with masonry infill walls were considered. The masonry infilled RC frames demonstrated larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. A specimen with a partial-height infill wall showed the least drift capacity and energy dissipation capacity. This specimen failed in shear, whereas other specimens experienced a relatively ductile failure mode (flexure-shear failure).