Reinforced Concrete Masonry Research Articles

In-Plane Cyclic Response of Reinforced Concrete Masonry Shear Wall with Large Cross-Section Core Columns

In-Plane Cyclic Response of Reinforced Concrete Masonry Shear Wall with Large Cross-Section Core Columns

FAST-NEPAL: Regionally Calibrated Spectral Method for Reinforced Concrete With Masonry Infills

Reinforced concrete (RC) with masonry infill is one of the most common structural typologies in Nepal, especially in the Kathmandu Valley. Masonry infills are typically made of solid clay bricks produced locally in Nepal. This study aims to calibrate the spectral-based analytical method, namely, FAST, for Nepalese RC-infilled buildings. The FAST method has been initially conceived for Southern European RC buildings with hollow clay brick infills. The calibration is achieved by reviewing code prescriptions and construction practices for RC masonry infills in Nepal and updating the FAST method. The variables of FAST method are calibrated using different information sources and a Bayesian updating procedure to consider the global and local material properties for solid clay bricks. The FAST-NEPAL method obtained is then verified, considering a single school design, for which a detailed state-of-the-art vulnerability assessment is available. Being particularly suitable for large-scale assessment, the method is further validated using data from Ward-35 of Kathmandu Metropolitan City (in the vicinity of Tribhuvan International Airport) obtained from photographic documentation included in a geo-referenced database of buildings collected after the 2015 Nepal earthquake and prepared for census purposes. The comparisons show that the FAST-NEPAL method can be conservative relative to the other data sources for vulnerability and is more accurate at capturing low-level damage. This makes the approach suitable for large-scale preliminary assessment of vulnerability for prioritisation purposes.

In-plane cyclic response of high-rise reinforced concrete masonry structural walls with boundary elements

The majority of tested Reinforced Concrete Masonry (RCM) shear walls with boundary elements represented walls in low- to mid-rise buildings. In addition, these tested walls had continuous vertical reinforcement with no lap splices, which is impractical in multi-story masonry buildings. Therefore, this study aims to evaluate the structural performance of high-rise RCM structural walls with boundary elements under reversed cyclic loading simulating seismic actions. This is achieved by constructing and testing four half-scale fully grouted RCM shear walls with boundary elements under constant axial load and quasi-static reversed cyclic loading. The walls were designed and constructed with similar geometry and material properties and were tested under the same level of axial compressive stress. The studied parameters are the wall’s shear span-to-depth ratio, the type of boundary elements’ masonry blocks (stretcher or C-shaped), and the lap splicing of vertical reinforcement in the plastic hinge region. The objective is to quantify the cyclic response of ductile RCM shear walls and to provide experimental evidence of its reliable structural performance for higher aspect ratios. Furthermore, the present study investigates the impact of the presence of lap splices in the plastic hinge region on the ductile response of high-rise RCM walls with boundary elements. The tested walls had an enhanced cyclic response due to its end zone confinement. The testing results demonstrated that the shear span significantly influences the distribution and layout of cracks, the lateral stiffness and resistance, and the post-peak response. Using the C-shaped blocks instead of the regular stretcher blocks in constructing the boundary elements enhanced the construction and performance of the walls. Lap splicing of vertical rebars increased the initial lateral stiffness, resulted in a higher rate of stiffness and strength degradation, and slightly limited the ultimate displacement ductility. However, with proper detailing of the splice and confinement of the end zones, the premature tensile bond failure was prevented.

Effect of Ductile Shear Wall Ratio and Cross-Section Configuration on Seismic Behavior of Reinforced Concrete Masonry Shear Wall Buildings

Reinforced masonry buildings typically have a load-bearing wall structural system. Thus, the reinforced masonry shear walls must be capable of resisting both vertical forces from gravity loads and lateral forces from seismic and wind loads. Typically, because the walls are subjected to high axial loads, ensuring the ductile response becomes challenging. A possible solution at the component level would be the utilization of walls with confined ends (i.e., walls with boundary elements) to reduce the compression zone and increase the compression strain. Another solution, which is at the system level, is the introduction of a hybrid structural system composed of two types of walls: (1) ductile walls with or without boundary elements to resist the lateral forces and part of vertical forces, and (2) gravity walls that resist only axial loads. This paper proposes a combination of both solutions (i.e., at component and system levels). Additionally, it utilizes a series of linear and nonlinear static and dynamic analyses to evaluate and quantify the effect of cross-section configuration and ductile shear wall area to total floor area (i.e., ductile shear wall ratio) on the seismic response of masonry buildings. The numerical analyses are performed by a macro model detailed to simulate the nonlinear response. The primary objective is to recommend a range of ductile shear wall ratios that optimize the design and overall performance. The study targets mid-rise and high-rise masonry buildings located in regions with moderate seismic hazard. The findings emphasize that utilizing the ductile walls with boundary elements in the proposed hybrid structural system resulted in major favorable enhancements in the structural response and optimization of the design. In addition, the results demonstrate the possibility of vertically reducing and terminating the specially detailed boundary elements, thus promoting ductile reinforced concrete masonry shear wall buildings as a competitive building system.

Structural Design of Reinforced Concrete Masonry Building

大阪北部の閑静な住宅街に位置する地上3階建ての社員寮に，鉄筋コンクリート組積造（RM造）を採用し，設計を行った。RC造やS造といった主要な構造種別と比較すると，建物への適用事例が少ないRM造について，その特徴や採用の利点・設計の考え方について紹介を行うとともに，RM造の特徴を活かして提案した設計手法を提示する。

Cyclic Analyses of Reinforced Concrete Masonry Panels Using a Force-Based Frame Element

AbstractThis paper presents the calibration of a frame element that can be used to model the flexural as well as the shear behavior of reinforced masonry panels subjected to monotonic and cyclic lo...

Brittle failure in RC masonry infilled frames: The role of infill overstrength

The interaction between an infill panel and a reinforced concrete (RC) column can lead to the brittle failure of the structural element. A novel combination of cutting-edge analytical modelling approaches for masonry infills and RC elements is employed to simulate five experimental tests (three infilled and two bare) characterized by brittle failure modes. The infill is modelled with a multi-strut idealisation, and the RC column is modelled using the recently developed PinchingLimitStateMaterial in OpenSees. The effects of the infill type (solid or hollow) and ductility characteristics of the RC elements on the optimal modelling parameters are investigated. The focus of this study is on the assumption of the overstrength ratio between the maximum and cracking strengths of the panel when brittle failure occurs. The preliminary assumption for this parameter is the widely accepted value of 1.3 suggested in the formulation by Panagiotakos and Fardis. This value is found to influence the shear failure simulation. To more accurately predict brittle failure, higher overstrength values of the infill are used in the numerical model to improve the matching between the numerical and experimental tests. These values are then compared with the approximate estimation of the overstrength ratio from a database of 98 experimental tests. The suggested estimation of the overstrength ratio is systematically greater than 1.3 and dependent on the infill type (i.e., 1.44 for hollow and 1.55 for solid infills). The proposed values can have a high impact on future code-compliant recommendations aimed at verifying the likelihood of the occurrence of brittle failure in columns due to their interaction with infill panels.

Fragility functions and floor spectra of RC masonry infilled frames: influence of mechanical properties of masonry infills

A wide number of experimental studies conducted in latest years pointed out the high influence of the mechanical properties of masonry units and mortar bed joints on lateral strength and stiffness of masonry panels. This feature significantly modifies the global response of infilled frames under seismic actions as well as the local interaction phenomena. Despite a wide investigation on the influence of the infills on global behaviour of reinforced concrete (RC) frames has already been provided, different features characterizing the seismic performances of buildings suggest the need of accurately evaluating local interaction phenomena as well as the influence of the panel on specific and relevant aspects, as the accelerations transferred to non-structural components. This study provides a parametrical analysis of the influence of shear strength and elastic modulus of masonry infills on the seismic behaviour of RC frames originally designed for gravity loads. Regular buildings with different height were analysed using the Incremental Dynamic Analysis in order to provide fragility curves, investigate on the collapse mechanisms and define the floor spectra depending on the properties of the infills. Results obtained pointed out the high influence of the considered parameters on the fragility of existing RC frames, often characterized by inadequate transversal reinforcement of columns, which may lead to brittle failure due to the interaction with the infills. Floor response spectra are also significantly affected by the influence of masonry infills both in terms of shape and maximum spectral accelerations. Lastly, on the basis of the observed failure mechanisms, a parameter defining the ductility of the frames depending on the properties of the infills was also provided (Capacity Design Factor). The correlation between the mechanical properties of the infills and this parameter suggests its reliability in the simplified vulnerability analysis of existing buildings as well as for the design of new buildings.

Finite Element Analysis of Reinforced Concrete Masonry Infilled Frames with Different Masonry Wall Thickness Subjected to In-plane Loading

In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

Blast Resistance of Fully Grouted Reinforced Concrete Masonry Veneer Walls

AbstractThis paper describes the full-scale experimental evaluation of the out-of-plane flexural response of fully grouted RC masonry walls subjected to uniform static pressure and to dynamic pressure resulting from an explosion. The investigation was performed as part of a larger effort to improve the design methodologies for reinforced masonry subjected to blast loading. The masonry walls were non-load-bearing and vertically spanning, which represents a significant amount of common construction in the United States. Both single-wythe and veneer wall sections were evaluated. Two types of concrete masonry units were used, i.e., conventional and A-block concrete masonry units. The results of the program provide a better understanding of the ultimate dynamic capacities and ductility of reinforced masonry walls—both single-wythe and veneer walls—which will ultimately help engineers produce designs that are safer and more economical.

Seismic Performance of a Six-Story Reinforced Concrete Masonry Building during the Canterbury Earthquake Sequence

During the Christchurch earthquake of February 2011, several midrise reinforced concrete masonry (RCM) buildings showed performance levels that fall in the range of life safety to near collapse. A case study of one of these buildings, a six-story RCM building deemed to have reached the near collapse performance level, is presented in this paper. The RCM walls on the second floor failed due to toe crushing, reducing the building's lateral resistance in the east–west direction. A three-dimensional (3-D) nonlinear dynamic analysis was conducted to simulate the development of the governing failure mechanism. Analysis results showed that the walls that were damaged were subjected to large compression loads during the earthquake, which caused an increase in their in-plane lateral strength but reduced their ductility capacity. After toe crushing failure, axial instability of the model was prevented by a redistribution of gravity loads.

Study on Reinforced Concrete Masonry High-Rise Building by Abaqus

Pseudo static tests of 10 specimen made of 290 mm thick reinforced concrete masonry wall were finished, then test results were simulated by ABAQUS which use shell element, pamameters of the materials were defined by the comparison between the calculation results and that of the test. A 100 m high reinforced concrete masonry building in China was analyzed, elastic-plastic deformation check calculation under earthquake action by time-history analysis method were detailed. The story drift of the building is 1/666 for fortification intensity 6 and 1/326 for intensity 7 under strong earthquake, it is feasible.

Study on Seismic Performance of Reinforced Concrete Masonry High-Rise Building

The design process of the 100 m high reinforced concrete masonry building in China was firstly presented, deformation check calculation under earthquake action by mode-superposition response spectrum method and time-history analysis method were detailed and deformation under wind load was also checked. Then elastic-plastic deformation under earthquake action was checked by time-history analysis method and pushover analysis method with both under uniform load and reverse triangle load. The conclusion is construct 100 m high office building built in Fortification intensity 6 by reinforced concrete masonry is feasible. Then the building was redesigned as built in fortification 7, the same check was performed as that have been done in fortification 6, it is feasible too.

The Effects of Applied Axial Stress on Lateral Bearing-Load Capacity for Fully Grouted Reinforced Concrete Masonry Shear Walls

Ten full-scale fully grouted reinforced concrete masonry shear walls were tested under force-displacement controlled reversed cyclic lateral loads simulating seismic effects. Relevant experimental phenomena and data indicated four walls failing in shear failure and the other six walls failing in flexure to evaluate seismic performance under compress, flexure and shear combined action. The paper mainly examinates lateral bearing-load capacity through two parameters: initial crack and ultimate strength under different failure modes. Through experimental analysis it can be concluded that the shear strength at the initial crack and ultimate load improved with the increased applied axial stress, and the increment of the shear strength was different in shear failure and flexural failure modes. Meanwhile, the ratio of the initial crack load to ultimate load on shear mechanism was from 0.57 to0.59,which was more stable than that(from 0.52 to 0.66)on flexural mechanism. In other words, the applied axial stress have more significant influence on flexural failure walls than shear ones.

Performance of masonry buildings and churches in the 22 February 2011 Christchurch earthquake

As part of the ‘Project Masonry’ Recovery Project funded by the New Zealand Natural Hazards Research Platform, commencing in March 2011, an international team of researchers was deployed to document and interpret the observed earthquake damage to masonry buildings and to churches as a result of the 22nd February 2011 Christchurch earthquake. The study focused on investigating commonly encountered failure patterns and collapse mechanisms. A brief summary of activities undertaken is presented, detailing the observations that were made on the performance of and the deficiencies that contributed to the damage to approximately 650 inspected unreinforced clay brick masonry (URM) buildings, to 90 unreinforced stone masonry buildings, to 342 reinforced concrete masonry (RCM) buildings, to 112 churches in the Canterbury region, and to just under 1100 residential dwellings having external masonry veneer cladding. In addition, details are provided of retrofit techniques that were implemented within relevant Christchurch URM buildings prior to the 22nd February earthquake and brief suggestions are provided regarding appropriate seismic retrofit and remediation techniques for stone masonry buildings.

Upgrading the Seismic Performance of Reinforced Masonry Columns Using CFRP Wraps

Compared with reinforced concrete, relatively fewer experimental studies address the behavior of masonry columns under com- bined axial load and cyclic flexure. There exist reinforced concrete masonry (RCM) columns that are part of the moment resisting system of masonry structures that are in need of seismic upgrade. Wrapping such susceptible RCM columns with carbon fiber-reinforced polymers (CFRP) is expected to enhance the seismic behavior of reinforced masonry columns considerably. This paper focuses on assessing the seismic performance of RCM columns wrapped with CFRP. In this experimental study, six 1.4-m reinforced masonry columns were constructed and tested when subjected to constant axial force and cyclic lateral excitations. The columns had a cross-section of 390 mm × 390 mm and were constructed using bull-nosed concrete units. The first column had no CFRP wraps and was used as a control specimen whereas the other five columns werewrapped using different layers of CFRP sheets or different wrapping schemes. From the tests, it was observed that wrapping the masonry columns with CFRP wraps enhanced the seismic performance of the columns by offering more ductile behavior, increasing both strength and energy dissipation capacity. DOI: 10.1061/(ASCE)CC.1943-5614.0000252. © 2012 American Society of Civil Engineers. CE Database subject headings: Reinforced concrete; Masonry; Columns; Fiber reinforced polymer; Seismic effects; Ductility. Author keywords: Reinforced concrete masonry (RCM) columns; CFRP wraps; Seismic; Ductile behavior.

Study on Earthquake Response Analysis of Reinforced Concrete Masonry Structure

According to the analysis of a six-story reinforced concrete masonry building model with the methods of nonlinear time history analysis, the seismic performance of structure has been studied in this paper. The interstory shear-deformation and stiffness of linear elastic model is established. The availability of the analysis model, hysteretic model and relevant parameters adopted and the computation program developed are verified. The longitudinal deformation of structure is bigger than the lateral deformation under different earthquake waves, from this it can be showed that longitudinal seismic performance is smaller than lateral wall; for seven-story concrete block building with core-and tie-columns, the requirement of the seismic fortification intensity can be met. The analysis of this paper provides a reference for reinforced concrete block buildings.

Characteristics of Rectangular, Flanged, and End-Confined Reinforced Concrete Masonry Shear Walls for Seismic Design

This paper contains detailed analyses of an experimental study conducted to evaluate the ductility, stiffness degradation and energy dissipation characteristics of rectangular, flanged, and end-confined reinforced masonry (RM) shear walls failing in flexure. The test program consisted of seven two- and three-story RM shear walls, with aspect ratios of 1.5 and 2.2, tested under reversed cyclic lateral displacements simulating seismic loading effects. Documentation of the compressive strains at the wall toes, wall base curvatures, and ductility levels attained are presented. The paper focuses on determining the extent of plasticity over the wall height, evaluating the contribution of flexure and shear deformations to the overall wall lateral displacements, identifying the trend of stiffness degradation, and quantifying the amount of energy dissipation. The rectangular walls displacement predictions at ultimate loads using Canadian Standards Association (CSA) S304.1 were in better agreement with the experimental results compared to the Masonry Standards Joint Committee (MSJC) code predictions. However, both the MSJC code and the CSA S304.1 significantly overestimated the test results for the flanged and end-confined walls. Analysis of the measured displacements showed that the contribution of shear displacement to the overall wall displacement was, on average, 21 and 25% of the total displacement for the walls with aspect ratio of 2.2 and 1.5, respectively. The relationship between the energy dissipation and the ratio of the postyield to the yield displacements was found to be almost linear for the test walls. In addition, the wall stiffnesses degraded rapidly to about 60% of their gross stiffness at very low drift levels (0.1% drift). Measured compressive strain at the wall toes were almost double those specified in both North American codes. Extent of plasticity over the wall height was about 75% of the wall length. The data presented in this paper is expected to facilitate better understanding of RM wall behavior under in-plane load to researchers, practicing engineers, and code developers. This study aimed at presenting the flanged and end-confined categories as cost-effective alternatives to enhance the seismic performance of midrise RM construction in North America.

In-Plane Behavior of Partially Grouted Reinforced Concrete Masonry Shear Walls

The objectives of this research were to experimentally establish the in-plane behavior of partially grouted (PG) reinforced concrete masonry shear walls and to assess the appropriateness of current seismic design provisions for such walls. To accomplish these, four PG special reinforced masonry shear walls (SRMSWs) were constructed based on the provisions of the Masonry Standards Joint Committee (MSJC) code and subjected to in-plane reversed cyclic displacements. The experimental test variables included mortar formulation, level of axial stress, and boundary conditions. The results of this study indicate that PG masonry shear walls respond similar to in-filled frames and provide little coupling between vertical reinforcing steels. Using these results along with those from past research, it is shown that the shear strength expression for reinforced masonry shear walls provided by MSJC (along with others) appears unconservative for PG masonry shear walls. In terms of displacement ductility, the results indicate that the response of PG SRMSW is consistent with the R factors provided by the 2006 International Building Code due to the required capacity design and increased shear demand provisions of the MSJC.

Behavior of Fully Grouted Reinforced Concrete Masonry Shear Walls Failing in Flexure: Experimental Results

In this paper, the possibility of achieving a high level of ductility by flexural yielding in fully grouted reinforced concrete masonry shear walls is evaluated. Six full-scale walls were tested to failure under reversed cyclic lateral loading to investigate the effects of amount and distribution of vertical reinforcement and the level of axial compressive stress on the inelastic behavior and ductility. Results showed that yielding of the outermost vertical bars extended to a height equivalent to half the wall length. Also, the top wall displacement (drift) at the onset of yielding of the vertical reinforcement was highly dependent on the amount of reinforcement, but only minimally affected by the level of axial compressive load. However, at maximum loads, the displacements were less sensitive to either the amount of vertical reinforcement or the level of axial compression. Correspondingly, the displacement ductility was found to be very sensitive to the amount of vertical reinforcement, but was not dependent on the level of axial compression. In general, high levels of ductility and energy dissipation capabilities accompanied by relatively small strength degradation were observed for the test specimens.