Reinforced Concrete Block Research Articles

Multiphysics simulation of recent experiments on alkali‐silica reaction expansion in reinforced concrete members

AbstractAlkali‐silica reaction (ASR) is an important degradation process that causes volumetric expansion and damage in concrete, and is affected significantly by the local temperature, moisture and stress conditions that often vary across the regions of a structure. Numerical simulation is essential to predict the progression and effects of ASR on the performance of structures. Because of the interactions between thermal and moisture transport and mechanical deformation, it is important for numerical models to represent all these physical phenomena and the coupling between them. Simulations of ASR in reinforced concrete (RC) structures are further complicated by the need to capture interactions between concrete and embedded reinforcing bars. This paper describes the implementation of a scalable, coupled‐physics ASR model for simulating RC structures and assesses the ability of that model to predict ASR‐induced expansion in recent laboratory tests on RC block and beam specimens. These laboratory tests and the simulation approach were selected because of their applicability to RC structural‐scale simulations. This validation study helps builds confidence the ability of this approach to model ASR expansion in large, complex RC structures, which is a current high‐priority need.

Volumetric Reinforced Concrete Block for Housing Construction with Flexible Apartment Layouts. Flexible Form-tooling and a Standfor the Manufacture of a Volumetric Block

Volumetric Reinforced Concrete Block for Housing Construction with Flexible Apartment Layouts. Flexible Form-tooling and a Standfor the Manufacture of a Volumetric Block

Hysteretic stressing state features of RCB shear walls revealed by structural stressing state theory

• Propose the methods for modeling the hysteretic stressing states of RCB shear walls. • Reveal the mutation features in the hysteretic stressing state evolution of RCB shear walls. • Define the hysteretic failure load at the starting point in the failure process of the RCB shear wall. • Define the hysteretic design load at the elastic-plastic branch point of the RCB shear wall. • Explore the value of the experimental hysteretic strain data of RCB shear walls. This study reveals the essential stressing state features of reinforced concrete block (RCB) shear walls in their hysteretic working process by applying structural stressing state theory and method. The experimental strains of the RCB shear wall are transferred into generalized strain energy density (GSED) values to build the stressing state mode and the parameter characterizing the mode. Then, the Mann-Kendall criterion is used to detect the mutation feature in the evolution of the stressing state characteristic parameter with the hysteretic load increase. Correspondingly, it is verified that the stressing state mode also presents the mutation feature. The stressing state mutation is the essential feature in the structural working process as structural failure starting point, which is the embodiment of the natural law from quantitative change to qualitative change of a system. Furthermore, the stressing state analysis reveals the elastic-plastic branch point in the working process of the RCB shear wall, which could be directly taken as the design point. In total, this study explores a new way to analyze the structural hysteretic working behavior and provides the rational reference to improve the existing design code.

Muon Tomography of the Interior of a Reinforced Concrete Block: First Experimental Proof of Concept

Quality assurance and condition assessment of concrete structures is an important topic world-wide due to the aging infrastructure and increasing traffic demands. Common topics include, but are not limited to, localisation of rebar or tendon ducts, geometrical irregularities, cracks, voids, honeycombing or other flaws. Non-destructive techniques such as ultrasound or radar have found regular, successful practical application but sometimes suffer from limited resolution and accuracy, imaging artefacts or restrictions in detecting certain features. Until the 1980s X-ray transmission was used in case of special demands and showed a much better resolution than other NDT techniques. However, due to safety concerns and cost issues, this method is almost never used anymore. Muon tomography has received much attention recently. Novel detectors for cosmic muons and tomographic imaging algorithms have opened up new fields of application, such as the investigation of freight containers. Muon imaging also has the potential to fill some of the gaps currently existing in concrete NDT. As a first step towards practical use and as a proof of concept we used an existing system to image the interior of a reference reinforced 600 kg concrete block. Even with a yet not optimized setup for this kind of investigation, the muon imaging results are at least of similar quality compared to ultrasonic and radar imaging, potentially even better. The data acquisition takes more time and signals contain more noise, but the images allowed to detect the same important features that are visible in conventional high energy X-ray tomography. In our experiment, we have shown that muon imaging has potential for concrete inspection. The next steps include the development of mobile detectors and optimising acquisition and imaging parameters.

Analysis and Optimization of Three-Beam Traverse Structure Elements for Reactor Cavity Reinforced Concrete Block Installation

Increased demands are placed on the reliability and strength of structures used in the installation of equipment for nuclear power plants. At the same time, an excessive safety margin of the equipment used leads to an increase in its dimensions, weight and a significant rise in cost. The issue of reducing the metal consumption of structures while maintaining the required performance criteria for this equipment is very relevant. The paper presents a model for optimizing the design of a three-beam traverse with a carrying capacity of 100 tons for reactor cavity reinforced concrete block installation. A verification calculation is carried out and recommendations on the optimization of design parameters are proposed on its basis.

Behavior of Seismically Detailed Reinforced Concrete Block Shear Walls with Boundary Elements under Out-of-Plane Loading

AbstractAlthough boundary elements have been known to enhance the in-plane performance of reinforced concrete block shear walls under seismic loading, research examining their influence on the wall...

PREDICTING CRACK SPACING OF REINFORCED CONCRETE TENSION MEMBERS USING STRAIN COMPLIANCE APPROACH WITH DEBONDING

A novel technique based on strain compliance for investigating the crack spacing of reinforced concrete (RC) tension members has been developed. The new method is based on the mean strain and the partial interaction (stress-transfer) approaches. The strain compliance principle is established by equating together the mean strains of a reinforced concrete block between adjacent primary cracks estimated by the mean strain and the stress-transfer approaches. The distribution of reinforcement strains within the RC block must be known to apply the stress-transfer approach. This technique is intended for the stabilized cracking stage, where formation of new primary cracks has ceased. This work accounts for local effects – fully damaged bond between the concrete and reinforcement near the cracks. Knowledge of a benchmark data point obtained from a reference element is required. The point is defined by the reinforcement ratio, bar diameter and mean crack spacing values. This data point enables the estimation of the mean crack spacing for other RC tension elements. A comparative investigation was carried out, with two different mean strain approaches, following the free-of-shrinkage tension stiffening law and provisions in Eurocode 2. The obtained results provide reasonably accurate estimates of crack spacing compared to experimental values.

Experimental Investigation on the Seismic Behavior of Newly-Developed Precast Reinforced Concrete Block Masonry Shear Walls

Typically, a special type of concrete block with cleaning holes is used in the bottom layer of traditional reinforced masonry shear walls (RMSWs) for mortar cleaning and vertical rebar connection, which results in reduced integrity and weakened structural behavior. In this paper, a precast construction technology was introduced to overcome these shortcomings. The cleaning-hole blocks were eliminated in the newly-developed precast RMSWs. Quasi-static tests on two traditional and two precast fully grouted RMSWs were conducted. The results showed that the flexural capacity of precast walls exhibited about a 10% increase when compared to traditional RMSWs under the same axial compression. Precast RMSWs that failed in flexural mode showed favorable deformation capacity and the displacement ductility value corresponding to 15% strength degradation reached 4.9. The wall stiffness degraded rapidly to 50% of the initial stiffness, K0, at 0.2% drift and, at 0.5% drift, the corresponding stiffness decreased to about 21% K0 at a more gradual rate. Furthermore, precast RMSWs exhibited significant energy dissipation capacity. The experiment suggests that precast RMSWs have a satisfactory seismic performance.

Experimental Assessment of the System-Level Seismic Performance of an Asymmetrical Reinforced Concrete Block–Wall Building with Boundary Elements

AbstractUsing boundary elements in reinforced masonry (RM) walls allows closed ties to be used and multiple layers of vertical bars to be accommodated, thus providing a confining reinforcement cage...

Response Analysis of Reinforced Concrete Block Infill Panels under Blast

AbstractIncreased exposure to the detrimental effects of blast events has led to the release of several guidelines and the recent publication of two North American standards that provide guidance on the hardening and performance quantification of structures subjected to this type of loading. The safety and security logistics and the high cost associated with performing experimental blast testing has led to a number of codes and guidelines accepting the use of simplified dynamic modeling techniques to analyze the response of structural components. Past research in blast-masonry interaction has primarily focused on the strengthening and retrofit of existing unreinforced masonry wall systems, whereas research related to evaluating the blast response of reinforced masonry (RM) has been limited. The focus of this study is to evaluate the accuracy of using simplified dynamic modeling techniques to predict the blast performance of nonintegral RM infill walls. To evaluate the accuracy of the simplified dynamic mo...

Experimental Evaluation of the System-Level Seismic Performance and Robustness of an Asymmetrical Reinforced Concrete Block Building

AbstractIn recent years, research interests in studying the response of different seismic force-resisting systems have been shifting from component-level to system-level studies. Building on the existing knowledge of component-level performance of reinforced masonry shear walls (RMSW), the current study evaluates some similarities and discrepancies between RMSW system-level and component-level responses under seismic loading. The study also focuses on evaluating the system-level seismic robustness of a RMSW building by quantifying key relevant robustness indicators proposed in the literature. To meet the study objectives, an experimental asymmetrical two-story reduced-scale RMSW building was tested to failure under simulated seismic loading. Subsequently, the study first presents a brief summary of the experimental program followed by a discussion of the damage sequence and the load-displacement hysteretic behavior of the RMSW building. In general, the experimental results demonstrated the impact of both ...

Influence of Floor Diaphragm–Wall Coupling on the System-Level Seismic Performance of an Asymmetrical Reinforced Concrete Block Building

Understanding the inelastic seismic response of reinforced masonry shear walls (RMSW) is the first step to develop predictive models of the system-level (i.e., complete building) response under different levels of seismic demand. Such predictive models will not only have to be capable of accurately accounting for the different system-level-specific aspects but will also have to be easy enough to be adopted by design engineers. In this respect, the influence of the floor diaphragms on a building’s seismic response is typically recognized only through the role of the former in distributing the shear forces on the building’s seismic force resisting system (SFRS) as a result of the diaphragms’ in-plane stiffness. Subsequently, the current paper focuses on analyzing experimental data of a series of RMSW tested as individual components and within two asymmetrical building systems. The analyses showed that the out-of-plane stiffness of the floor diaphragms played an important role in flexurally coupling the RMSW aligned along the loading direction with those walls aligned orthogonally. This system-level aspect affected not only the different wall strength and displacement demands but also the failure mechanism sequence and the building’s twist response. For the building system under consideration, the diaphragm-wall coupling resulted in doubling the building’s initial stiffness, and also significantly increasing the building’s strength. The results of the study show that neglecting diaphragm out-of-plane coupling influence on the RMSW at the system-level may result in unconservative designs and possibly undesirable component-level failure modes as a result of violating capacity design principles. To develop an analytical model that can account for the aforementioned influences, simplified load-displacement relationships were developed to predict RMSW component- and system-level responses under lateral seismic loads. In the current study, three approaches were proposed to account for the diaphragm coupling influences on the RMSW response. The developed analytical model presents a useful system-level response prediction tool for displacement- and performance-based seismic design of RMSW buildings.

The New Method of Cohesion Quality Assessment of Basalt Plastic Lining of Reinforced Concrete Blocks for Engineering Collectors

The article is devoted to assessment of cohesion quality of basalt plastic lining with reinforced concrete block's surface. It is suggested to use new type of nondestructive method instead of existing ones (visual, breaking-off, etc.) that don’t give exact and complete data. The new method gives the possibility to determine stratification between basalt plastic lining and reinforced concrete base and has to be considered as necessary part of production technology and exploitation of collectors made from reinforced concrete blocks with of basalt plastic lining. The problems of nondestructive method of control within the scope of these methods come to the next: to determine accordance of ready reinforced concrete blocks with basalt plastic lining for technical specifications and to reject some of them that have separations mentioned above; to obtain information about time and a place of appeared separation during manufacturing blocks that is necessary to optimizing production technology of basalt plastic lining and coupling with reinforced concrete base; to indicate places of separation during construction of collectors for carrying out proper repairs until the beginning of its putting into operation; to get periodical information about appeared separations into collectors to prevent any abnormal situation, that increase intervals between repairs and periods of exploitation, shorten duration time of repairs.

Seismic Response Evaluation of Ductile Reinforced Concrete Block Structural Walls. II: Displacement and Performance–Based Design Parameters

AbstractA typical seismically designed reinforced masonry building is composed of structural walls, constructed following the same prescriptive detailing requirements corresponding to a code classified seismic force resisting system (SFRS). However, due to architectural requirements (i.e. to allow for requirements such as openings and wall intersections), some of these walls might have the same overall aspect ratio but differ in their cross-section configurations. The companion paper presented the experimental results and force-based seismic design parameters for walls that fall under the Canadian Standards Association (CSA) ductile shear walls and the Masonry Standards Joint Committee (MSJC) special-reinforced walls SFRS classifications. The current paper utilizes the experimental results to extract key displacement-based seismic design parameters, including wall yield and ultimate curvatures, wall displacements at yield and at the post-yield stages, stiffness degradation, period elongation, and equivale...

Seismic Response Evaluation of Ductile Reinforced Concrete Block Structural Walls. I: Experimental Results and Force-Based Design Parameters

The reported experimental study documents the performance of six fully grouted reinforced concrete block structural walls tested under quasistatic cyclic loading. The walls fall under the ductileshear walls and the special reinforced masonry walls seismic force resisting system (SFRS) classification of the Canadian and U.S. standards, respectively. The test matrix consisted of one rectangular, one flanged, and two slab-coupled walls, all with an overall aspect ratio of 1.4. In addition, two rectangular walls, representing the individual components of the slab-coupled wall systems, were tested to quantify the wall slab coupling effects. In addition to discussing the experimental results, the study also presents key force-based seismic design (FBSD) parameters, such as the wall lateral load capacity, plastic hinge length, wall failure modes, and displacement ductility capacities. Moreover, the effects of wall cross-sectional configuration and slab coupling on the cyclic response and deformation capabilities of the walls are discussed. In general, the yield and ultimate loads were found to be accurately predicted using the Canadian Standards Association (CSA) S304-14 and Masonry Standards Joint Committee (MSJC) formulations. The wall experimental displacement ductility values (calculated at 20% strength degradation) ranged between 5.4 and 7.6, whereas the idealized displacement ductility values at the same strength degradation level ranged between 3.4 and 5.4. The analysis results reported in the paper highlight the fact that walls designed and detailed within the same SFRS classification possess significantly different FBSD parameters. The results also indicate that slab coupling, although not recognized as a wall coupling mechanism in the current editions of the CSA and MSJC, can have significant influences on the seismic response of ductile/special reinforced masonry wall systems.

System-Level Seismic Performance Assessment of an Asymmetrical Reinforced Concrete Block Shear Wall Building

AbstractIn this study, a two-story reinforced concrete block scaled building was tested to failure under fully reversed quasi-static displacement-controlled loading. The building’s seismic force-resisting system (SFRS) consisted of eight structural walls in total, with four walls, aligned along the loading direction, placed asymmetrically to result in a center of rigidity eccentricity from the floor center of mass of approximately 20% of the building width, evaluated on the basis of elastic analysis. The other four orthogonal walls were placed symmetrically around the building floor center of mass to provide torsional restraints to the building. As such, the focus of the paper is on evaluating the influence of twist as a system-level aspect on the ductility capacity of the building and the ductility and strength demands of its wall components. This paper presents the details of the building SFRS and wall configurations and characteristics and the main test observations and results. This is followed by ana...

Response Evaluation of Reinforced Concrete Block Structural Walls Subjected to Blast Loading

With the introduction of the new American and Canadian standards for blast resistant design, there is a need to evaluate the response of different structural components under such extreme loads. This paper focuses on experimentally evaluating the damage levels and the out-of-plane response of fully grouted reinforced concrete block structural walls under blast loading—a load that they are typically not designed to resist. The scaled walls reported in this paper cover a range of design parameters and charge weights that reflect different vulnerabilities and threat levels. Three different reinforcement ratios and three different charge weights have been used, with scaled distances as low as 1.61 m/kg1/3 and two different boundary conditions, to evaluate the walls’ response. In general, the results show that the walls are capable of withstanding substantial blast load levels with different extents of damage depending on their vertical reinforcement ratio and scaled distance. However, brittle behavior was observed in the walls with a reinforcement ratio higher than 0.6%. This is attributed to the fact that seismically detailed (concrete or masonry) structural walls designed to respond in a ductile manner under in-plane loads might develop brittle failure under out-of-plane loads. This is a consequence of the increased concrete block wall reinforcement ratio in the out-of-plane direction compared with the same in the in-plane direction. The maximum experimental support rotation values were compared with the corresponding values predicted using an available nonlinear single-degree-of-freedom (SDOF) model presented in the Unified Facilities Criteria document. In general, the comparison between the experimentally obtained and the analytically predicted support rotation values indicated reasonable agreement. The test results are expected to contribute to the growing masonry blast performance database of experimental results and to the future development of reinforced concrete block wall design provisions under blast loading in North America, in which a balance between the wall strength and ductility might be necessary to remain below the different damage classifications specified by the performance-based design oriented ASCE and Canadian Standards Association (CSA) standards.

Seismic Response Analysis of a Reinforced Concrete Block Shear Wall Asymmetric Building

AbstractThis paper presents detailed analyses of experimental results pertaining to the cyclic behavior of a reduced-scale reinforced masonry (RM) asymmetric building with walls aligned in two orthogonal directions. The current study focuses on analyzing the influence of twist, as a system-level effect, on the displacement and strength demands of the building’s individual seismic force resisting system (SFRS) wall components. The study evaluates the individual wall contributions to the overall building response characteristics within both the elastic and the inelastic response phases. Documentation of the compressive strains at the wall toes is also presented and correlated to the damage levels anticipated for each wall. In addition, the building center of rotation and center of strength are determined and the corresponding twist angles and moments and building torsional stiffness values are evaluated throughout the loading history. Moreover, the trends of stiffness degradation for the walls and for the b...

Shake Table Seismic Performance Assessment of Lightly Reinforced Concrete Block Shear Walls

AbstractThere is a need to develop a reinforced masonry (RM) seismic performance database (SPD) of experimental results in order to facilitate adoption of RM seismic force-resisting systems (SFRS) in the next generation of performance-based seismic design (PBSD) codes. As a contribution to this SPD, and within a larger ongoing research program, this paper reports on recent shake table tests performed on lightly reinforced masonry shear walls. The test walls covered a range of design parameters to facilitate benchmarking, further performance investigation, and calibration of numerical models as well as future development of fragility curves within the context of PBSD. The design parameters of the walls were selected to meet the requirements of the lightly reinforced conventional construction category. This particular RM wall category is not permitted in moderate and high seismic zones in the Canada based on Canadian masonry design code. Within the context of PBSD, the wall seismic performances, in terms of...

Seismic Response Analysis of Lightly Reinforced Concrete Block Masonry Shear Walls Based on Shake Table Tests

AbstractThis paper presents detailed analyses of experimental shake table test results with the goal of providing a better understanding of the seismic performance of lightly reinforced fully grouted masonry shear walls. The paper first gives a brief summary of the experimental program followed by detailed analyses of the inelastic behavior characteristics of the walls. This includes quantifying the walls’ displacement ductility levels, extent of plastic hinge zones, and equivalent plastic hinge lengths based on the experimental results. Separation of the various energy components of the system, including those of the shake table, the walls, and the external mass support system, based on the experimental results, is also carried out. Utilizing the evaluated energy components, the characteristics of the system, including the change of input energy levels with time and the contributions of the different energy dissipation mechanisms (e.g., hysteretic, viscous damping, and coulomb friction damping), are quan...