Masonry Infilled Reinforced Concrete Frames Research Articles

Prediction of seismic performance of a masonry-infilled RC frame based on DEM and ANNs

In this paper, discrete element modelling and artificial neural networks (ANNs) were adopted to evaluate seismic performance of a masonry-infilled reinforced concrete (RC) frame. Discrete element models were developed to simulate quasi-static tests of infilled frames and were validated by using experimental data from the literature in terms of ultimate bearing capacities, initial stiffnesses and hysteresis curves. Parametric analysis was conducted based on the validated models to further investigate the influence factors of infilled RC frames and to collect a database for training ANN models. Subsequently, 440 datasets were divided into a training set (70 %), a validating set (15 %), and a testing set (15 %). Back propagation neural network (BPNN) and radial basis function neural network (RBFNN) were employed to predict the seismic behavior of a masonry-infilled RC frame. The BPNN model used the Levenberg-Marquardt algorithm exhibited the highest coefficient of determination, and it was better than the RBFNN model with more neurons. Eventually, a practical ANN model was proposed to evaluate the seismic performance of a masonry-infilled RC frame.

Solving the Problem of Short Column Effects in Masonry Infilled RC Frames: Numerical Investigations

In this study, the common issue related to the masonry infilled reinforced concrete (RC) frames under earthquake loading has been investigated. Namely, infilled RC frames are used in construction sector all over the world since they are easy and fast to construct. However, every medium to strong earthquake showed that this system is highly vulnerable to the seismic effects. Significant damage of infill walls, but also of the load carrying frame system demonstrates that stiff mortar connection between brittle masonry and highly deformable RC frames is not adequate. Damage of infilled RC frames lead to the high amounts of losses after earthquakes. Therefore, there is need to improve this behavior. Several problems caused by the infill/frame interaction have been investigated for decades and different approaches for modelling and improvement have been proposed. However, still there is no consensus on the modelling approach for infilled frames, as well none of the proposed solutions has not been accepted in practice. The most promising solution is to decouple infills from the frames and in this way diminishes negative effects of infill/frame interaction. This paper focuses on the short column effects, where infill walls increase shear forces in the columns, thus causing their damage. The numerical investigation of the short column effects on the traditional and decoupled infill has been presented. The analysis shows that the proposed decoupling system significantly improves the behavior of infilled RC frames. Infills are not activated by the frame deflection under earthquake loading and infills are not causing increase of forces in the surrounding frame. Results confirm that decoupled infills behave much better than traditional infills where contact between frame and infill has been achieved via mortar. Much higher in-plane drifts can be reached by using the decoupling INODIS system.

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.

Full-scale testing of masonry-infilled RC frames retrofitted with cross-laminated timber panels

This paper presents the results from an experimental study on an innovative timber-based seismic retrofit solution for existing reinforced concrete (RC) buildings. The intervention aims at enhancing the overall seismic resistance of RC framed structures with a light, cost-effective, sustainable, and reversible approach, allowing possible integration with energy efficiency upgrades. The retrofit technique relies on cross-laminated timber (CLT) panels mechanically connected through steel fasteners to the RC frame. This strengthening technique is investigated experimentally for the first time in this paper. The study examines two intervention configurations with different degrees of invasiveness: the first (RC-TP) involves replacing the existing masonry infill wall with a CLT panel, whereas the latter (RC-TPext) consists in applying the panel to the outer face of the frame. Both retrofit configurations were assessed experimentally through cyclic quasi-static in-plane tests on full-scale single-storey, single-bay RC frames. The frames were identical in geometry and characterised by poor mechanical material properties and steel reinforcement details, promoting the development of a strong-beam-weak-column mechanism. The experiments comprised tests on four specimens: a non-retrofitted masonry-infilled frame employed as a reference specimen and three frames strengthened with CLT panels as infills or externally connected retrofitting elements. The paper presents construction details of the strengthening interventions, demonstrates a step-by-step application procedure, and summarises the main observations from the tests, illustrating the evolution of structural damage, the ultimate failure mode, and the cyclic hysteretic response of the specimens. The experiments showed promising results, proving that both retrofit configurations improved the seismic behaviour of the RC frames considerably. Specifically, the RC-TP and RC-TPext retrofit interventions increased the lateral strength of the reference frame by approximately 169% and 104%, respectively. At the same time, both configurations prevented the shear collapse of the columns.

Experimental Research on Seismic Performance of Masonry-Infilled RC Frames Retrofitted by Using Fabric-Reinforced Cementitious Matrix Under In-Plane Cyclic Loading

Fabric-reinforced cementitious matrix (FRCM) composites, also known as textile-reinforced mortars (TRMs), represent a new advancement in structural repair and reinforcement technology. Aiming to improve the energy efficiency and seismic performance of existing buildings, this research focused on the development of an FRCM system in combination with phase change materials (PCMs) and extruded polystyrene sheets (XPS) to achieve adequate mechanical and thermal properties for reinforced concrete (RC) and masonry structures. Accordingly, the in-plane behaviour of five FRCM-strengthened RC frames with hollow-brick wall infill was tested under cyclic loading to investigate the improvement in earthquake resistance. The system was comprehensively evaluated by calculating hysteresis curves; comparing the lateral stiffness, ductility, and energy dissipation capacity; measuring the deformations of the specimens; and analysing the failure modes mechanically. Finally, it was proved that this novel integrated approach could significantly enhance the mechanical and seismic performance of masonry-infilled RC frames.

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.

Quantification of Equivalent Strut Modeling Uncertainty and Its Effects on the Seismic Performance of Masonry Infilled Reinforced Concrete Frames

ABSTRACT Quantifying aleatory and epistemic uncertainty in nonlinear structural response simulation is key to robust performance-based seismic assessments. This paper focuses on the modeling parameters that are used to describe the nonlinear force-deformation response of the equivalent infill struts used in models of reinforced concrete frames with infills. The variability in several parameters is characterized by developing empirical and theoretical multivariate probability distributions based on the deduced-to-predicted ratios derived using data from 113 physical experiments. The effect of the uncertainty in the infill strut modeling parameters on maximum story drift ratios and associated limit state fragility functions is investigated for a 3-story reinforced concrete frame building with infills. Multiple stripe analysis is performed using hazard-consistent ground motions. Relative to when only record-to-record variability is considered, modeling parameter uncertainty has a non-negligible effect on the dispersion of the maximum story drift ratios, and affects both the median and dispersion of the limit state fragilities.

Framework to assess the seismic performance of non-engineered masonry infilled RC frame buildings accounting for material uncertainty

Non-engineered construction accounts for more than half of the building stock in low and middle-income countries. A significant portion of these buildings is constructed using masonry infilled reinforced concrete (RC) frames with inadequate seismic detailing. This type of construction is prone to high levels of variability in the material properties, posing a significant challenge in their seismic performance evaluation. This research proposes a framework to assess the seismic performance of non-engineered constructed masonry infilled RC frame buildings, which considers the material uncertainty. A four-stage procedure based on Monte Carlo simulations is introduced, wherein engineering demand parameters and seismic performance are expressed in terms of probability distributions. The framework is demonstrated using a non-engineered housing archetype located in Sincelejo, Colombia. The results showed that the framework allows capturing the uncertainty in the materials construction variability of non-engineered houses. The results also showed that mean values of material properties may lead to significant errors in the seismic performance assessment of non-engineered constructed masonry infilled RC frames. The differences between the predicted minimum and maximum exceedance probabilities of a damage state can be greater than 80%.

Quantification of the effects of different uncertainty sources on the seismic fragility functions of masonry-infilled RC frames

The presence of masonry infills is known to have a significant effect when assessing the seismic vulnerability of reinforced concrete (RC) structures, and including these elements in the numerical modelling has become imperative. In computationally-intense probabilistic analyses such as those integrated in performance-based earthquake engineering (PBEE) frameworks, the simulation of the masonry infills is often performed using the single strut approach/technique. Despite the advantages of this modelling approach, it can be related to several sources of uncertainty that can impact probabilistic performance results such as fragility functions. In this context, the proposed study examines the effect of the uncertainty associated to the parameters of the strut model representing the infills, and to the definition of global limit state thresholds reflecting the lateral deformation capacity of infilled structures. The study considers RC structures of different sizes and with different infill configurations, and the relative importance of both sources of uncertainty is analysed by comparing fragility functions defined for different limit states. The comparisons are first performed qualitatively followed by a statistical analysis based on the results of several two-sample tests. Results indicate that, depending on the infill modelling options and on the way limit state values are considered, the corresponding fragility functions can be significantly different. These results highlight the need for further research dedicated to the uncertainty quantification and propagation associated with limit state values for infilled structures and with empirical models that provide parameters for simulating the behaviour of infills under earthquake loading.

In-plane/out-of-plane seismic performance of masonry infilled RC frame structure made of nano-SiO2 reinforced mortar: Experimental study

Due to the seismic vulnerability of conventional masonry infill wall Reinforced Concrete (RC) frame buildings, which caused the infill wall structure to break and collapse, resulting in serious casualties and property damage. It was necessary to fully understand the action mechanism and seismic strengthening of the infill wall structure. Considering that few researches had paid attention to the effect of mortar performance on the seismic behaviors of infill wall structure, this study was the first to use a nano-SiO2 (NS) reinforced mortar to construct masonry infill wall RC frame structure. The pure out-of-plane (OOP) and in-plane and out-of-plane (IPOOP) loading tests were conducted to validate the structure's seismic performance. The experimental results of comparison with ordinary mortar specimen were shown. Due to the mitigation of the cracking of wall in pure OOP test, the initial stiffness, load-bearing capacity and ultimate displacement of new mortar specimen were increased by 65.88%, 23.57% and 11.12%, respectively. However, both infill wall specimens exhibited the similar cracking characteristics and load-displacement response, those indicated that the improvement in mortar performance was not sufficient to change the failure mode. In the in-plane (IP) tests, the infill walls constructed with new mortar provided a better diagonal bracing mechanism, resulting in a 13.32% and 12.67% increase in the IP load-bearing and energy dissipation capacity. The less side shear cracking of infill wall caused stiffness degrades more slowly. In the IPOOP tests, at approximately the same previous IP damage level, the slower propagation of crack resulted in a slower reduction in the load-bearing capacity and an increase in the deformability during subsequent OOP loading. Therefore, the application of the new mortar improved the shear and bond strength of the members, which mitigated IP damage and improved the stability of the wall, while slowed down the OOP cracking of the wall and reduced the risk of collapse.

Numerical Modeling Technique of Damage Behavior of MaSonry-Infilled RC Frames

The damage pattern of masonry-infilled reinforced concrete (RC) frame structures in earthquake events is complicated, and understanding the detailed failure behavior of these structures and modeling it accurately has been a challenging task. In this paper, the extended finite element method (XFEM) is introduced to reproduce arbitrary cracks initiating and propagating in concrete frame and masonry units, combined with interface elements to model various behaviors of masonry-infilled RC frames. Within the finite element analysis program FEAP, a user element subroutine is adopted for the incorporation of XFEM and two types of extended finite elements with and without crack tip enrichments are built to simulate the behavior of concrete material for frame members and masonry blocks for the infill panel, respectively. In addition, a macro command is created to check the crack-propagation criterion and update crack and enrichment information. Furthermore, numerical examples are performed with existing test data, which reveal the efficiency of the implementation procedure. A comparison of the analytical and experimental results show that the proposed modeling can be used to predict the crack and failure process and the load-bearing capacity curves of the structures and reflect accurately the interaction of masonry infill and RC frames.

Effect of In-Plane Damage on Out-of-Plane Response of FRCM Strengthened Masonry Infilled RC Frames

The out-of-plane (OP) strength of masonry infills is reduced when damaged under the action of the in-plane (IP) forces. A strengthening approach using a fabric-reinforced cementitious matrix (FRCM) was proposed for improving the OP strength of damaged infill walls. A finite-element (FE) model of a reinforced concrete (RC) frame, infilled with FRCM-strengthened masonry, was developed and validated using experimental results and analytical predictions. Interaction curves representing the interplay between in-plane damage and out-of-plane response were generated for unstrengthened (ordinary) and FRCM-strengthened infill walls using FE analysis. Results of the FE analysis showed that FRCM-strengthened infills had greater OP strength in the undamaged state and suffered less strength degradation at high-damage states compared to unstrengthened infills. Anchoring of the fabric proved effective in utilizing the strength and ductility of the FRCM reinforcement. The fabric with ±45° orientation contributed more in resisting the diagonal tension under in-plane shear but was not as effective as 0°–90° orientation in resisting the OP flexural stresses corresponding to in-plane damage at 2.2% drift level. A novel definition of damage state was introduced for fragility analysis that can consider the effect of in-plane damage and out-of-plane strength using interaction curves. A four-bay, five-story masonry infilled RC frame was analyzed using the capacity spectrum method, and fragility curves were developed for unstrengthened and FRCM-strengthened infills. The effect of variation in out-of-plane demand and in-plane damage on each floor was included in the analysis. The RC frame using FRCM strengthened infills exhibited a smaller probability of exceedance of the performance limit than the unstrengthened infills. The proposed methodology helped identify critical infills that require strengthening.

Masonry-Infilled RC Frames Exposed to Blast Loads: A Review on Numerical Modeling and Response

The spurt in terrorist activities worldwide has drawn the attention of engineers and researchers to the vulnerability of building structures to blast loads. Response of masonry-infilled reinforced concrete (RC) frames subjected to blast loads is a widely researched area that still poses considerable complexity and challenges. Most of the works are based on finite element (FE) methodology to simulate the blast-induced behavior of the masonry-infilled RC structures considering the material constitutive and interaction aspects. Many literature studies have focused on FE codes for numerical modeling of masonry-infilled RC frames and interpretation of their response to various blast load scenarios (far-field, near, and contact blasts). The review presented herein addresses the aspects to include: Estimation of the blast load parameters, including the code provision and its simulation in the analysis module; updated knowledge on geometric and material modeling; effect of strain rate on constitutive parameters while modeling the materials; macro, micro, and simplified micro approaches to model masonry infill walls and their response under blast loading; modeling of interaction between RC frame and masonry infills and the performance of the integral and nonintegral system under blast loading. It is envisaged that such studies, in turn, would facilitate evolving the rational design methodologies for the blast-resistant design of framed structures. At the end of this paper, some parametric studies of field interest that are carried out in the literature are reported to understand the behavior of masonry-infilled RC frames against blast loads and derived some valuable conclusions. The review presented in this study provides a thematic analysis of the available literature aimed to assist the analyst in selecting a suitable tool for investigating masonry-infilled RC frames exposed to blast loads.

Seismic Retrofitting of Masonry Infilled Reinforced Concrete Frames with an Open Ground Story Using Inverted-Y Steel Bracing System

ABSTRACT This paper presents results from numerical investigation into the seismic retrofit of masonry infilled reinforced concrete (RC) frame structures with soft ground story using inverted-Y steel bracing system. The dynamic response of the retrofitted four-story RC frame with an open ground story is evaluated and compared with the response of the original frame. Comparisons are carried out with the variation of the mechanical characteristics of infills in order to investigate the way in which the soft story mechanism occurs. Results from nonlinear dynamic analyses indicate that this type of bracing can effectively eliminate the formation of a soft-story collapse mechanism.

Numerical analysis of the in-plane behaviour of decoupled masonry infilled RC frames

Damage of reinforced concrete (RC) frames with masonry infill walls has been observed after many earthquakes. Brittle behaviour of the masonry infills in combination with the ductile behaviour of the RC frames makes infill walls prone to damage during earthquakes. Interstory deformations lead to an interaction between the infill and the RC frame, which affects the structural response. The result of this interaction is significant damage to the infill wall and sometimes to the surrounding structural system too. In most design codes, infill walls are considered as non-structural elements and neglected in the design process, because taking into account the infills and considering the interaction between frame and infill in software packages can be complicated and impractical. A good way to avoid negative aspects arising from this behavior is to ensure no or low-interaction of the frame and infill wall, for instance by decoupling the infill from the frame. This paper presents the numerical study performed to investigate new connection system called INODIS (Innovative Decoupled Infill System) for decoupling infill walls from surrounding frame with the aim to postpone infill activation to high interstory drifts thus reducing infill/frame interaction and minimizing damage to both infills and frames. The experimental results are first used for calibration and validation of the numerical model, which is then employed for investigating the influence of the material parameters as well as infill’s and frame’s geometry on the in-plane behaviour of the infilled frames with the INODIS system. For all the investigated situations, simulation results show significant improvements in behaviour for decoupled infilled RC frames in comparison to the traditionally infilled frames.

Computation of Natural Frequencies of Masonry Infilled RC Frames Validated with Modal Assurance Criterion

Contribution of infill walls to in-plane structural response of reinforced concrete (RC) frame is an important aspect that many researchers have studied using experimental and numerical methods. This paper presents the modeling of 3D RC unreinforced masonry infill (MI) frames using multiple nodes to one node constraint (MTOCO) with the independent node at the center of gravity of infill with mass and inertial properties of infill. This method of modeling is then compared with other macro and micro modeling methods. A macro model with equivalent diagonal strut using 1D element and two micro models, both with 8-noded brick elements with the interface between infill and RC frame modeled using node to surface tied interface in one and small sliding contact in another. All these four models are solved using a Virtual Performance Solution (VPS) implicit FE solver. Natural frequencies of the structure from these four numerical solutions are then compared with available experimental shake table [25] results. To assess the degree of consistency between the four numerical methods, Modal Assurance Criterion (MAC) [29] is used. The Modal Assurance Criterion is a statistical indicator that is most sensitive to large differences and relatively insensitive to small differences in the mode shapes. This yields a good statistical indicator and a degree of consistency between mode shapes. From a functional point of view, the openings in the infills are a significant parameter to consider because they influence the lateral stiffness and strength. Having established its validity as explained above, this new methodology is then extended to RC frames with openings and partial fillings. A comparison of the results of both micro and macro methods shows a very good correlation.

Reinforced Concrete Infilled Frames

Masonry-Infilled Reinforced Concrete Frames are a very widespread structural typology all over the world for civil, strategic or productive uses. The damages due to these masonry panels can be life threatening to humans and can severely impact economic losses, as shown during past earthquakes. In fact, during a seismic event, most victims are caused by the collapse of buildings or due to nonstructural elements. The damage caused by an earthquake on nonstructural elements, i.e., those not belonging to the actual structural body of the building, is important for the purposes of a more general description of the effects and, of course, for economic estimates. In fact, after an earthquake, albeit of a low entity, it is very frequent to find even widespread damages of nonstructural elements causing major inconveniences even if the primary structure has reported minor damages. In recent years, many territories have been hit worldwide by strong seismic sequences, which caused widespread damages to the nonstructural elements and in particular to the masonry internal partitions and the masonry infill panels of the buildings in reinforced concrete, with damage to the floor and out-of-plane expulsions/collapses of single layers. Unfortunately, these critical issues have arisen not only in historic, but also in recent buildings with reinforced concrete, in many cases exhibiting inadequate seismic behavior, only partly attributable to the intrinsic vulnerability of the masonry panels against seismic actions. Such problems are due to the following aspects: lack of attention to construction details in the realization of the construction, use of poor-quality materials, and above all lack of design tools for the infill masonry walls. In 2018, regarding the design of nonstructural elements, the formulation of floor spectra has been recently introduced in Italy. This entry article wants to focus on all these aspects, describing the state of the art, the literature studies and the design problems to be solved.

Experimental investigation of strengthening of masonry-infilled RC frames using prefabricated engineered cementitious composite panels

Cement-based composite materials such as engineered cementitious composites (ECCs) are appropriate for retrofitting buildings because of their high tensile strength and strain. This research evaluated the lateral behavior of strengthened masonry-infilled reinforced concrete (RC) frames reinforced with prefabricated engineered cementitious composite (PECC) panels. The goals of the proposed technique were to increase the energy absorption capacity and the lateral capacity of infilled RC frames and protect the stability of the masonry infills after cracking and brittle failure in the out-of-plane direction, which can contribute to the seismic vulnerability of a structure. The mechanical characteristics of the ECC materials, such as the tensile strength and strain and multiple cracks, were first determined. Then, nine diagonal compression tests were done on masonry panels strengthened with PECC panels. In these tests, two types of connection were compared and the best one was selected. Next, an existing one-story RC moment frame with one bay was scaled down for testing under lateral cyclic loading. The results indicated that the strength, deformation, stiffness, and energy absorption of the RC frames increased considerably. Additionally, the effects of the precast panel thickness, performance of the connections, and type of damage sustained were compared between the different types of tests. Overall, the PECC panels connected to the infill wall with the proposed connections improved the lateral behavior of the system in the in-plane direction and markedly mitigated the risk of collapse by confining the masonry infill wall.

Experimental testing of decoupled masonry infills with steel anchors for out-of-plane support under combined in-plane and out-of-plane seismic loading

Because of simple construction process, high energy efficiency, significant fire resistance and excellent sound isolation, masonry infilled reinforced concrete (RC) frame structures are very popular in most of the countries in the world, as well as in seismic active areas. However, many RC frame structures with masonry infills were seriously damaged during earthquake events, as the traditional infills are generally constructed with direct contact to the RC frame which brings undesirable infill/frame interaction. This interaction leads to the activation of the equivalent diagonal strut in the infill panel, due to the RC frame deformation, and combined with seismically induced loads perpendicular to the infill panel often causes total collapses of the masonry infills and heavy damages to the RC frames. This fact was the motivation for developing different approaches for improving the behaviour of masonry infills, where infill isolation (decoupling) from the frame has been more intensively studied in the last decade. In-plane isolation of the infill wall reduces infill activation, but causes the need for additional measures to restrain out-of-plane movements. This can be provided by installing steel anchors, as proposed by some researchers. Within the framework of European research project INSYSME (Innovative Systems for Earthquake Resistant Masonry Enclosures in Reinforced Concrete Buildings) the system based on a use of elastomers for in-plane decoupling and steel anchors for out-of-plane restrain was tested. This constructive solution was tested and deeply investigated during the experimental campaign where traditional and decoupled masonry infilled RC frames with anchors were subjected to separate and combined in-plane ‬and out-of-plane loading. Based on a detailed evaluation and comparison of the test results, the performance and effectiveness of the developed system are illustrated.

Experimental and numerical investigation on cyclic behavior of masonry infilled RC frames retrofitted with partially bonded CFRP strips

This paper investigates experimentally and numerically the behaviors of retrofitted masonry infilled reinforced concrete (RC) frames using totally bonded or partially bonded diagonal carbon fiber reinforced polymers (CFRP) strips under cyclic loads. Five 1/2-scaled, one bay, one storey nonductile RC frames were built and tested as bare and infilled reference specimens, and as x-cross CFRP sheets retrofitted specimens. Retrofitting the RC frames was based on the use of two different techniques; (a) totally bonded CFRP strips (b) partially bonded CFRP strips. Significant findings were noted while comparing the retrofitted specimens with reference specimens in terms of inter-storey drift, lateral load capacity, energy dissipation capacity, stiffness, and the observed damages. Moreover, using CFRP anchors delayed the debonding failure mode. A two-dimensional (2D) finite element model (FEM) of the tested frames was also developed to predict the behaviors of these specimens under cyclic loading. Element types and materials constitutive model of cyclic behavior were described. The infill-frame interaction, in addition to the interactions between CFRP and RC frames, were accurately mimicked. The suggested (2D) FEM was compared with experimental test results. Results of the FEM showed good agreement with test results, showing high accuracy in relation to ultimate load capacities and modes of failure. Bonded and partially bonded CFRP stripes showed similar lateral strength and stiffness.