Masonry Infilled RC Frames Research Articles

Development of a Macro-Model for concrete masonry infilled frames

Masonry walls, when built to infill a frame structure, have been shown to have a significant effect on the strength, stiffness, and seismic properties of the frame structure. The accurate consideration of this effect is crucial in lateral behavior analysis of the infilled frame structures, especially under the seismic loading condition. This study proposes a new macro-model in an effort to developing a practical and rational approach for evaluating the masonry infill contribution in the design of masonry infilled frames. This model accounts for the compressive and shear behavior of the masonry infill as well as the infill effect on the bounding frame. Compressive behavior was represented through compressive struts located in the diagonal direction connecting loaded corners of the infill. Two sets of three struts were used to replace the top and bottom half of the masonry infill. The shear behavior of the infill was captured through a shear spring connecting the two sets of struts at the center of the infill. The struts and shear spring were configured in a serial manner such that both compressive and shear sliding failure can be predicted. The constitutive laws assigned to the struts and spring were based on consideration of orthotropic properties of masonry and experimental observations. This model was verified against the test results of masonry infilled masonry frames obtained in this study and of masonry infilled RC frames reported in the literature. Both monotonic pushover and quasi-static cyclic analyses were considered in the model verification. The results showed that the proposed model is capable of simulating the in-plane response of infilled frames of both materials and in both loading conditions adequately.

Behaviour of Masonry-Infilled RC Frames Strengthened Using Textile Reinforced Mortar: An Experimental and Numerical Studies Overview

ABSTRACT A large part of the existing building stock was not designed according to the current codes in seismic prone regions. The poor performance of some reinforced concrete structures was related to the presence of the masonry infill walls. Although the infill walls can increase the lateral resistance of frames in many cases, it is widely recognized that there is a high vulnerability of the masonry infill walls subjected to loadings along and perpendicular to their plane. Several collapses were observed after past earthquakes in infilled frame buildings. For this reason, different retrofitting design approaches have been proposed and used during the last years; however, many of them do not fit with the building’s owners’ economic demands or technical knowledge of the workmanship. Over the years, significant research has been conducted for masonry wall elements retrofitted with textile-reinforced mortar (TRM). However, much less has been carried for masonry-infilled frame RC frames. Thus, this manuscript aims to provide a literature review about research on assessing the effectiveness of using TRM technique to reduce masonry-infilled RC frames’ seismic vulnerability. Experimental findings will be deeply analysed to provide full insight concerning the TRM’s efficiency under in-plane and/or out-of-plane demands of infilled frames and some variables such as anchorage of the TRM to the structure. Numerical modelling approaches to simulate the complex behaviour of infilled frames with TRM are also presented to stress their benefits or limits. Covering completely all aspects of this manuscript is essential to briefly describe the studies conducted so far to examine either numerically or experimentally the effectiveness of using TRM for retrofitting masonry wall elements.

Performance of Prefabricated Foam Concrete as Infilled Wall Under Cyclic Lateral Loading

Every year earthquakes occur in various regions in Indonesia because Indonesia is located near earthquake faults. The cyclic lateral loading test in the laboratory has been widely used to simulate lateral loads caused by earthquake events. This research is an experimental study on the behavior of prefabricated foam concrete as an infill wall against lateral cyclic loads. Prefabricated foam concrete was used in this study to make it an alternative to brick and autoclaved lightweight concrete (ALC) blocks that have been widely used as infill walls. This study analyzes the relationship between performance levels, lateral loads and drifts ratio on RC infilled prefabricated foam concrete. Lateral cyclic loading with displacement control method was applied to evaluate the structural behavior where the test refers to ASTM E2126-02a. This study adopts FEMA 273, which regulates the performance levels to be achieved by the structure of a building. The results showed that at performance levels Operational Level (OL), Immediate Occupancy (IO) and Life Safety (LS), the RC frame infilled with prefabricated foam concrete blocks had a drift ratio of 0.2%, 1.2% and 2.4%, respectively. Damage to the RC frame infilled with prefabricated foam concrete blocks was similar to the masonry infilled RC frame.

Development and Calibration of a 3D Micromodel for Evaluation of Masonry Infilled RC Frame Structural Vulnerability to Earthquakes

Within the scope of literature, the influence of openings within the infill walls that are bounded by a reinforced concrete frame and excited by seismic drift forces in both in- and out-of-plane direction is still uncharted. Therefore, a 3D micromodel was developed and calibrated thereafter, to gain more insight in the topic. The micromodels were calibrated against their equivalent physical test specimens of in-plane, out-of-plane drift driven tests on frames with and without infill walls and openings, as well as out-of-plane bend test of masonry walls. Micromodels were rectified based on their behavior and damage states. As a result of the calibration process, it was found that micromodels were sensitive and insensitive to various parameters, regarding the model’s behavior and computational stability. It was found that, even within the same material model, some parameters had more effects when attributed to concrete rather than on masonry. Generally, the in-plane behavior of infilled frames was found to be largely governed by the interface material model. The out-of-plane masonry wall simulations were governed by the tensile strength of both the interface and masonry material model. Yet, the out-of-plane drift driven test was governed by the concrete material properties.

Development and Validation of New Bouc–Wen Data-Driven Hysteresis Model for Masonry Infilled RC Frames

During the last years, several mechanics-based macromodels have been proposed to assess the cyclic response of infilled RC frames. However, the uncertainties behind the assumptions on damage and failure mechanisms compromise the reliability of such approaches. For this reason, this paper proposes a new data-driven hysteresis model for the cyclic response of infilled RC frames. The infill panel is schematized as a single-degree-of-freedom element, whose constitutive law is given by the proposed hysteresis model. The model combines a degrading Bouc–Wen element with a slip-lock element, which is introduced specifically to reproduce the pinching effect due to crack openings in the masonry panel. The parameters governing the model have clear physical meanings and are calibrated on the basis of an experimental data set of cyclic responses of single-story single-bay RC infilled frames. The calibrations are carried out by means of a genetic algorithm–based optimization. Analytical correlation laws linking the model parameters with geometric and mechanical properties of the RC infilled frame are proposed and validated by blind validation tests. Results show adequate accuracy of the model in reproducing the cyclic response of infilled frames characterized by significantly different geometrical and mechanical features. The model is defined by a smooth analytical hysteresis law, with great advantages regarding numerical stability and computational effort. This makes it suitable for dynamic and stochastic simulations.

Time period estimation of masonry infilled RC frames using machine learning techniques

The accurate estimation of the fundamental time period is critical for the error-free risk and reliability estimation of infrastructure systems. Although complex empirical models are available in the literature, this paper estimates the application of machine learning approaches for the time period estimation. Recently, a good database of masonry-infilled RC frames and their fundamental period exist in literature and preliminary approaches like artificial neural networks have been tried out on them. In this work, we use advanced machine learning algorithms based on bagging and boosting approaches, and the comparison of our results with those already published shows that these methods can outperform the existing ones. The contribution of each variable to the fundamental time period is explained locally and globally using Shapely Additive Explanations.

Structural significance of Pneumatic Interface in Masonry infilled RC frames

Reinforced concrete framed construction is a common method adopted in developing countries. Failure of these structures in seismic regions indicate that unconfined interaction between the infill and the RC bounding frame is a prime cause. During these failures infill failure leads to collapse of the structure. Since, masonry work in the frame increases the stiffness of otherwise Bare frame. Infills in these structures altered the ductile behavior of RC bare frame. To avoid this, an interface medium can be provided between the masonry work and the frame to significantly change the impact on masonry work under in-plane static-cyclic loading condition. In this study finite element analysis is carried out to study the structural performance of masonry infill and RC frame under static cyclic loading with and without interface medium which can change its stiffness. Such a medium is made up of tube filled with air, called as pneumatic medium. The structural parameters of masonry infilled RC frame with pneumatic interface with varying pressure is analyzed and compared with RC Bare frame and masonry infilled RC frame, under static monotonic loading.

Lateral Cyclic Load Test of Masonry Infilled RC Frames Strengthened with Ultra-High Performance Concrete Diagonal Strips

Infilled frame structures have been a common form of construction. However, their behavior is one of the least understood and investigated among all the major construction systems. For a long time, these structures were built with a general lack of conclusive research and design information. An experimental program was undertaken which aims at investigating the behavior of masonry infilled RC frames strengthened with Ultra-High Performance Concrete (UHPC). In this study, UHPC cross diagonal strips, having a width of 355 mm, were bonded onto the masonry substrate using high strength epoxy mortar. Single-side strengthening layout was adopted due to the fact that it is frequently implemented in the case of external facade walls of existing masonry buildings to preserve the building exterior aesthetics and also on internal walls which have some sorts of artworks on one side. Regarding the CFRP strengthened infilled frame, 60% and 160% increase was achieved in the lateral load carrying capacity and energy dissipation, respectively, when compared to the reference frame. Furthermore, the drift capacity at failure was improved by 1.58 and 1.40 times for UHPC and CFRP strengthened specimens, respectively, when compared with the reference specimen.

Out-of-plane cyclic response of masonry infilled RC frames: An experimental study

This paper presents the development of an experimental campaign to investigate the cyclic, out-of-plane response of reinforced concrete frames containing masonry infill walls, using non-contact optical techniques to measure contour strains and deformations. Bare RC frames, as well as fully infilled walls, both with and without window and door openings, were tested in the laboratory. From the analysis of the results, it was found that neither the infill walls nor the openings significantly affected the overall behaviour of the specimens. However, the infill walls suffered substantial damage within a storey drift ratio of 1.25−2.50%, which poses a risk to life and livelihoods. In addition, it was found that masonry walls containing openings, sustained further damage, especially those with eccentrically positioned openings, when compared with the fully infilled frames. Finally, in the case of masonry infills containing openings and when debonding of the infill from the surrounding frame occurred, parts of infill walls could fall out due to inertia and could influence the overall combined, in-plane behaviour of the specimen.

Effect of Masonry Infill Constitutive Law on the Global Response of Infilled RC Buildings

Masonry-infilled reinforced concrete frames represent a very common construction typology across the Mediterranean countries. The presence of infills substantially modifies the global seismic performances of buildings in terms of strength, stiffness, and energy dissipation. Although several research studies focused on the overall performances of infilled reinforced concrete frames, the modeling of infill panels remains an open issue due to the complex interaction between the infill and the frame and the uncertainties involved in the definition of the problem. In the present paper, an existing masonry-infilled RC frame designed according to obsolete seismic codes is chosen as a case study. A refined three-dimensional finite element model is built for performing nonlinear static and time-history analyses in order to investigate some significant aspects related to the modeling of infills. In particular, it is investigated the effect of different infill constitutive models on the seismic performance of infilled RC building expressed in terms of engineering demand parameters such as interstory drift ratios and peak floor accelerations, and on the generation of damage fragility curves.

Seismic collapse risk of RC frames with irregular distributed masonry infills

Masonry infills are normally considered as non-structural elements in design practice, therefore, the interaction between the bounding frame and the strength contribution of masonry infills is commonly ignored in the seismic analysis work of the RC frames. However, a number of typical RC frames with irregular distributed masonry infills have suffered from undesirable weak-story failure in major earthquakes, which indicates that ignoring the influence of masonry infills may cause great seismic collapse risk of RC frames. This paper presented the investigation on the risk of seismic collapse of RC frames with irregularly distributed masonry infills through a large number of nonlinear time history analyses (NTHAs). Based on the results of NTHAs, seismic fragility curves were developed for RC frames with various distribution patterns of masonry infills. It was found that the existence of masonry infills generally reduces the collapse risk of the RC frames under both frequent happened and very strong earthquakes, however, the severe irregular distribution of masonry infills, such as open ground story scenario, results in great risk of forming a weak story failure. The strong-column weak-beam (SCWB) ratio has been widely adopted in major seismic design codes to control the potential of weak story failures, where a SCWB ratio value about 1.2 is generally accepted as the lower limit. In this study, the effect of SCWB ratio on inter-story drift distribution was also parametrically investigated. It showed that improving the SCWB ratio of the RC frames with irregularly distributed masonry infills can reduce inter-story drift concentration index under earthquakes, therefore, prevent weak story failures. To achieve the same drift concentration index limit of the bare RC frame with SCWB ratio of about 1.2, which is specified in ACI318-14, the SCWB ratio of masonry-infilled RC frames should be no less than 1.5. For the open ground story scenario, this value can be as high as 1.8.

Effect of prior in-plane damage on the out-of-plane behavior of masonry infill walls

Out-of-plane collapse is one of the most important failure modes for masonry infill walls in frame structures during earthquakes and may result in significant economic loss, blocked evacuation pathways and even injuries and fatalities. To investigate the effect of prior in-plane damage on the out-of-plane behavior of masonry infill walls, a series of full-scale masonry infilled RC frame specimens that conform to the Chinese practice were subjected to sequential in-plane and out-of-plane quasi-static loading. The results show that the out-of-plane strength of the masonry infill walls was reduced by 22% and 47% at 1/500 and 1/200 prior in-plane drift ratios, respectively, whereas the out-of-plane stiffness was not significantly affected by the prior in-plane damage. Based on the test results of the present experiment and the collected data available in the literature, an empirical equation was derived to relate the out-of-plane strength reduction factor with both the prior in-plane drift ratio and the slenderness of the wall panel. According to the equation, the out-of-plane strength starts to degrade when the in-plane drift ratio reaches approximately 0.1% to 0.3% depending on the wall slenderness. Both the rate and extent of the strength degradation are greater for slenderer wall panels. Through a numerical example, we demonstrate that neglecting such an in-plane-out-of-plane interaction may lead to substantial underestimation of the loss by seismic damage of masonry infill walls in buildings.

Architectural and engineering design criteria for earthquake resistant masonry infilled RC frames containing openings

In earthquake resistant design of RC frame structures, the definition of masonry infilled frame is often split between reinforced concrete and the masonry structures. However, it is known that the frame elements and the masonry wall work as a coupled system. Additionally, a dedicate chapter for the definitions of openings size, quantity and position is missing. The definition of a full, partial or non-masonry infilled frame with opening is not establish in engineering and architectural codes; rather, recommendations are given. A competent masonry infilled frame with openings would mean to correlate the architectural and engineering concepts as to define an engineered or non-engineered infilled wall. Likewise, certain boundaries should be established using both the architectural and engineering concepts to relate the importance of illumination and air ventilation product of the openings and masonry infilled frame failure patterns.

Machine learning and nonlinear models for the estimation of fundamental period of vibration of masonry infilled RC frame structures

In this work, the estimation of the fundamental period of vibration of masonry infilled RC frame structures is achieved using both Machine Learning techniques and concise nonlinear formulas. The data used are extracted from a recently published extensive database that associates the period with relevant information, such as the height of the structure, the span length between columns, the wall opening ratio, and the masonry wall stiffness. It is shown that, as compared to the utilized data, the proposed methods produce excellent results at the cost of various levels of complexity.

The Effects of Amount and Location of Openings on Lateral Behavior of Masonry Infilled RC Frames

Many design codes didn’t consider masonry infills as structural elements inside moment resisting frames. Therefore, their presence is not assumed in analysis and design process. While, in real they could affect strength, energy dissipation, ductility, stiffness and many other features of moment frames. The presence of masonry infills could also change the reaction of frames exposed to lateral loads like earthquake and wind. This issue becomes more important if the built frame was placed in seismically active region. In current study, the effects of opening location by placing openings in 3 different places and its percentage was evaluated. To this purpose an experimental scaled model was constructed and subjected to cyclic loading. Thereafter, by using simplified micromodeling, numerical modeling performed for extending studies. Subsequently, sensitivity analyses were done to survey the effects of opening ratio on the lateral behavior of intermediate RC moment frames. Analytical results indicate that the openings which were lo20cated at upper corner of the masonry infills will loss more strength. In all of the numerical specimens by increase in opening percentage the lateral strength was decreased. The lateral strength was negligible for infills with greater than 40% openings.

Behaviour of Reinforced Concrete Frames with Central Opening Masonry Infill under Lateral Reversed Cyclic Loading.

This paper will describe the seismic behaviour of masonry infilled RC frame with a central opening structure under reversed cyclic lateral loading. To achieve the purpose of this study, four 1/4-scale single story and single bay RC frame specimens were tested, i.e. one bare frame, one clay brick masonry infilled RC frame without opening and two clay brick masonry infills with a central opening in infills. The ratios of opening size to panel area were 25% and 40%. Through reversed cyclic lateral loading tests, the seismic performance of RC frames with a central opening brick masonry infills was investigated. As the results, significant distinctions of failure mechanism, lateral strength, stiffness, and ductility were observed between these specimens. In the case of infills with a central opening, the cracks sprouted and developed at the corners of the opening. Although the presence of the opening in infill reduces the lateral strength and stiffness overall structure, the brick infilled frames with a central opening of 25% and 40% of panel area show better seismic performance as compared to the bare frame.

Nelinearna seizmička analiza AB okvirnih konstrukcija sa zidnom ispunom

Nelinearna seizmička analiza AB okvirnih konstrukcija sa zidnom ispunom

A novel macromodel for prediction of shear failure in columns of masonry infilled RC frames under earthquake loading

Columns of masonry infilled reinforced concrete frames are prone to shear failure due to the detrimental effect of infill under lateral earthquake loads. This effect is catastrophic in ground storey columns, where the shear force demand is very high. The primary objective of the study is to understand the applicability of the codal recommendations to estimate the shear demand on the columns realistically, and propose an alternative solution for prediction of shear failure of columns by improving the existing macro-modelling techniques. Half-scaled specimens of masonry infilled RC frames tested in an experimental study were considered to evaluate the proposed improvements. Applicability of the improved macromodel was also verified with the results obtained in other past experimental studies. The proposed simplified analytical modelling technique can be used for practical engineering purposes to assess the shear failure of columns and can be utilized for designing or strengthening the shear deficient columns in such frames.

Out-of-Plane Strengthening of Masonry-Infilled RC Frames with Textile-Reinforced Mortar Jackets

AbstractThis paper presents an experimental investigation on the use of textile-reinforced mortar (TRM) jackets as a means of improving the out-of-plane performance of masonry infill walls in reinf...

Evaluation of earthquake load resistance of masonry infilled RC frames using linear and non-linear dynamic analysis

The understanding of the dynamic behavior of structures is essential to design them to resist the lateral loads due to earthquakes. Recent past earthquakes have demonstrated the importance of proper designing of structural members to avoid damages in the buildings and loss of life. Generally the lateral load resistance of masonry infilled moment resisting frames is achieved by frame action and truss action. In this paper the seismic performance of a G + 9 storeyed masonry infilled RC framed building is evaluated by linear and non-linear dynamic analysis. The analysis is carried out using the finite element software-ETABS. The response spectrum and time history pertaining to the specifications as given in the Indian Seismic Code IS 1893:2016 is considered for the analysis. Three different frame models are studied namely, bare frame, fully infilled frame and soft storey frame to understand the lateral load resistance of the frames. The dynamic characteristics of the frames such as time period, frequency, mode shapes, storey displacements, inter-storey drift, over-turning moments and energy dissipation capacity are evaluated and compared. The fully infilled frame shows better seismic behavior than that of other two frames though it attracts more forces.