Concrete Block Masonry Research Articles

Seismic Capacity Assessment of Unreinforced Concrete Block Masonry Buildings in Pakistan Before and After Retrofitting

This article presents the results of an experimental study on the performance of a full-scale unreinforced concrete block masonry (URCBM) building system tested under quasi-static loading. The configuration and materials used for the single-story URCBM building are typical of those found in the northern areas of Pakistan affected by the 2005 Kashmir earthquake. The retrofitting of the building was done using ferro-cement overlay and cement based grout injection. Combined shear and flexure failure was observed during the test before retrofitting. The lateral load capacity of the retrofitted building was significantly improved (more than 200% of the original strength) and the damage mechanism was transformed from mixed compression-flexure-shear to a more stable flexural rocking mode. Damage patterns and force-deformation behavior of the retrofitted structure are compared with those of the intact structure to quantify the beneficial effects of retrofitting scheme, which is proposed as an efficient approach for the rehabilitation of the existing buildings. Experimental data were analyzed and presented in the form of force-deformation hysteresis loops and envelope curves. Based on the measured data, different performance levels before and after retrofitting of the structure have been established. Response modification (R), displacement ductility (μD), and displacement amplification (Cd) factors were also derived. The results from this study are expected to guide future efforts on development of design recommendations and vulnerability assessment of buildings in Pakistan.

Research on Compressive Strength of Grouted Dry-Stack Concrete Block Masonry

Compressive strengths of full-grouted dry-stack concrete block masonry were tested. Contribution of block and grouted concrete in carrying capacity of the masonry were analyzed through compressive strength data of 18 specimens. Related masonry capacity formulas were recommended accordingly.

Out-of-plane behaviour of hollow concrete block masonry walls unstrengthened and strengthened with CFRP composite

This paper presents an experimental investigation conducted on full-scale masonry walls subjected to out-of-plane loading. This study contributes in detail both the global behaviour of hollow concrete block masonry walls unstrengthened and strengthened by composite, as well as the behaviour of constituent materials. On one hand, on a global level, this study has multiple objectives. It first quantifies the bearing capacity in the case of uniform pressure in quasi-static loading, and highlights the associated modes of rupture, and second estimates the improvements achieved in terms of overall behaviour when the structure is strengthened with Carbon Fibre Reinforced Polymer (CFRP) layers. The masonry walls strengthened with CFRP reinforced from 50% to 140% of bearing capacity wall. One of the important points of these tests was to reproduce the totally real boundary conditions by the presence of two return walls and of the reinforced concrete foundation. Sensitivity of these real boundary conditions towards the response of masonry walls was discussed. In particular, the digital image correlation (DIC) technique was applied to damage mechanism assessment of return wall. On the other hand, on a local level, the non-destructive testing (NDT) methods were also invested to identify the characteristics of the constituent materials.

The Masonry Crack Propagation Simulation Based on LS-DYNA

Due to the development of the computer hardware and the difficulties in determining the constitutive relation, it is difficult to research the crack propagation of large-scale masonry with the finite elements analysis method. The paper analyses the single storey concrete block masonry experimental model with the software LS-DYNA, using winfrith concrete material model instead of masonry material. And the calculated results were compared with the test results. The comparison indicates that the crack propagation of masonry can be simulated better with winfrith material model, which can be used in the finite elements analysis of large-scale masonry.

Shaking table test on building in masonry structure with construction waste recycled brick

Based on the shake table test on "tie column-ring beam-cast-in-place slab" construction waste recycled brick masonry structure, a 1/3 scaled model of 4 stories is tested to analyze the seismic behavior of the multi-storey masonry structure. The test is conducted with EL-Centro seismic wave, Taft wave and artificial wave to simulate the damages observed and the seismic response under different earthquake levels. On the basis of test results, the seismic performance of the model is good and the overall structure could satisfy seismic fortification requirements in the region of intensity 8. At the same time, there was no obvious difference between this masonry structure and recycled aggregate concrete block masonry structure. The lintel of the door and window damage seriously. The base damages more easily than the superstructure. Masonry structure with construction waste recycled brick can satisfy the requirement of the masonry structure buildings in eight degree of aseismatic design area.

Effects of Transverse Bar Spacing on Bond of Spliced Reinforcing Bars in Fully Grouted Concrete Block Masonry

AbstractTwenty-seven wall-splice specimens reinforced with number (No.) 15 (0.6 in.) deformed bars were tested to evaluate the effect of transverse bar spacing on the tensile resistance of the lap-spliced reinforcement. All specimens were 2 1/2 blocks wide and 13 courses tall and were constructed in running bond with all cells fully grouted. In all cases, the lapped bars were located within a single block cell and were either spaced 0, 25, or 50 mm (0, 1, or 2 in.) apart. It was determined that the calculated tensile resistance of the reinforcement was greater for bars that were in contact and furthermore, is insensitive to the magnitude of the transverse spacing provided in the case of noncontact lap splices. It would appear that both the American and Canadian provisions are appropriate for both contact and noncontact lapped bars given the resulting levels of conservatism.

Observed damages in Pakistan due to 16 April 2013 Iran earthquake

This paper presents the record of damages which were observed in Pakistan due to a strong earthquake on 16 April 2013 in Iran. Mashkel was the nearest town in Pakistan close to the epicentre of earthquake. The damages were documented by a survey team during the visit of Mashkel. The intensity of earthquake in most of the visited areas was found to be VIII on the Modified Mercalli Intensity scale. The infrastructure facilities were undamaged and were operating satisfactorily. On the other hand, heavy damage to adobe buildings was caused by the earthquake. Most of the building failure was resulted by the out-of-plane wall collapse; nearly 40 % adobe buildings were collapsed due to ground shaking in some of the affected areas. Reinforced concrete and cement concrete block masonry buildings performed better than adobe buildings. Using the data of building damage and earthquake intensity fragility curves for adobe buildings in Mashkel were developed.

ANALYSIS AND DESIGN OF MULTI-STOREYED LOAD BEARING REINFORCED MASONRY STRUCTURE AND FRAMED RC STRUCTURE

Load bearing masonry structures in India are generally restricted to 3 or 4 storeys in height. This is mainly because of lack of availability of good quality masonry unit and associated workmanship. Also, it is generally perceived that load bearing masonry storey may perform in brittle manner under excessive lateral loads. However, with the advancement of availability of engineered hollow concrete blocks which has a scope to introduce reinforcement, it is perhaps possible to design and eventually construct multistoreyed reinforced masonry building. In this paper an attempt has been made to analyse and design the structural components of a multi-storeyed residential building using reinforced hollow concrete block masonry. (i) Residential occupancy in ground floor + 8 floors. The building is analysed and designed for all the load combination as per the codal provisions. Later the same building is analysed and design by considering it as conventional RC framed structure system. The structural comparison of both of them has been made. Based on the study it is found that the requirement of reinforcing steel and concrete is significantly lesser, when compared to building designed as load bearing masonry system. It is also found that masonry prism strength of 7.5MPa with nominal vertical reinforcement is adequate to withstand the combination of axial and lateral loads.

Compressive Strength of Double H Concrete Block Masonry Prisms

This study investigated the compressive strength of double H concrete block masonry prisms. A total of 42 (i.e., nine ungrouted, 15 half-grouted, and 18 full-grouted) specimens were tested under uniaxial compression. The effects of mortar strength, grouting, and grout strength on the compressive strength of the prism were discussed. The test results show that the compressive strength of H-block prisms decreased with an increase of grouting, although the ultimate load of the prisms increased greatly.

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...

The prediction of compressive strength of ungrouted hollow concrete block masonry

The objective of this paper is to develop a simple and accurate empirical formula to predict the compressive strength of ungrouted hollow concrete block masonry fm′. A large database of compressive test results on masonry prisms reported in the literature was assembled and analyzed for this purpose. The collected database was also utilized to evaluate the predictive capability of the proposed model compared to those of major international masonry design codes. The study showed that the masonry codes underestimate the compressive strength of ungrouted masonry with high coefficients of variation, whereas the proposed formula gives the most accurate prediction of compressive strength with the least variation. The research also highlights the necessity for improving the prediction of compressive strength of concrete masonry by masonry design codes.

Experimental Study on Compressive Property of New Concrete Block Masonry with Multi-Row Cores

With the development of energy-saving in buildings, new energy-saving block masonry with multi-row cores is commonly used. In this paper, from the study of typical bearing capacity of multi hole concrete block masonry of combining multiple rows of holes, holes in the multi block wall masonry capacity test of heat insulation material characteristics. Test results show that, in the process of multi hole masonry brittle failure characteristics, built-in straw block in the insulation at the same time, can improve the compressive strength of masonry; masonry local diffusion mechanism under the action of stress is significant; and offer the engineering measures.

Study on the Basic Mechanical Properties of Recycled Concrete Hollow Block Masonry

By the experimental studying on the basic mechanical properties of recycled concrete hollow block masonry, the compressive and shear behavior of recycled aggregate concrete hollow block masonry under different mortar strength were analyzed. Research indicated that the compressive and shear behavior of recycled aggregate concrete hollow block masonry was similar to that of ordinary concrete hollow block masonry. The normal formula was recommended to calculate the compressive strength of the masonry. The shear strength of the masonry was affected by the mortar strength. The shear strength calculation formula of recycled concrete hollow block masonry was proposed according to the formula of masonry design code. The calculating results were in good agreement with the test results.

Study on the Seismic Performance of Block Masonry

For the time being there are few literatures about study on the seismic performance of concrete hollow block masonry based on the finite element method, left fewer conclusions for reference. According to characteristics of the finite element software, which has strong capability of nonlinear analysis, some key problems are discussed, including the modeling of the concrete hollow block masonry structure, constitutive relations of the materials in block masonry, damage assessment, solution methods, the application of the dead and live loads and the earthquake wave and the seismic performance analysis. The time-history analysis is carried out on three different type walls with openings. Some key factors, such as core columns and ring beams, which have a great influence on the damage pattern and stability of the structure, are discussed. The conclusion from the paper can provide a beneficial reference for in-depth study of the seismic performance of concrete hollow block masonry and the damage patterns.

Experimental Research of Hollow Concrete Block Masonry Stress Deformations

The article discusses the results of experimental investigation of highly hollow concrete block masonry and concrete infill block masonry behaviour under compression. The research revealed that upon failure of hollow block masonry, the longitudinal shells are detached from the web which results in crumbling. Masonry deformations of the blocks with concrete infill are similar to those of the infill concrete control samples for longitudinal deformations, which proves fairly good mutual block and infill concrete performance.

Design of Reinforced Concrete Block Masonry Basement

Common concrete miniature hollow block masonry is the main promotion material in wall materials reform of China. The paper presents the structural design and the calculation process of the tall building wall emphatically. It meets the specification. The design can be used as a reference to similarity engineering.

Mechanical Behavior of Concrete Block Masonry

Mechanical Behavior of Concrete Block Masonry

The Impact of Cracks on Different Age of Concrete Small-Sized Hollow Block Masonry

In the latter part of concrete small-sized hollow block masonry cracks after using many reasons, including the design factors that are not in place, the material factors, construction factors, climate, natural conditions, factors, etc., in which the age of c concrete small-sized hollow block length of cracks in the masonry of the impact is different. Cracks in the masonry structure will cause adverse effects, affecting the use of construction and durability, this paper field test, to identify non-instars of concrete small-sized hollow block masonry cracks on impact. To reduce or prevent age of concrete hollow block the effects of crack, to strictly control the construction of block wall on the age, age as long as possible, especially in areas influenced by temperature, such as wall, the top wall, should pay attention to blocks of age, in a possible, concrete hollow block age should be greater than 42 days, the best age to block more than 56 days is better.

Shaking Table Tests on a Recycled Concrete Block Masonry Building

A full scale model of a block masonry building with the tie column + ring beam + cast-in-place slab system, which was made of recycled aggregate concrete (RAC), was tested on the MTS shaking table at the State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai, China. The design and production of the test model, the design of the testing program and the experimental phenomenon were described in detail. The natural frequency, equivalent stiffness of the structure, the structural damping ratio, the acceleration response, the seismic force response, the displacement response, the base shear response and the structural fragility etc. were analyzed and discussed. The test results demonstrate that the RAC block masonry structure confined by the ‘tie column + ring beam’ system is a good solution to withstand earthquakes. The storey drift ratio and the overall behavior meet the requirements of Chinese design code. Generally, the RAC block masonry structure bounded by the ‘tie column + ring beam’ system with proper design exhibits good seismic behavior and can resist the earthquake attacks under different seismic levels in this study.

Experimental and numerical investigation on in-plane behaviour of hollow concrete block masonry panels

This paper presents the details of studies conducted on hollow concrete block masonry (HCBM) units and wall panels. This study includes, compressive strength of unit block, ungrouted and grouted HCB prisms, flexural strength evaluation, testing of HCBM panels with and without opening. Non-linear finite element (FE) analysis of HCBM panels with and without opening has been carried out by simulating the actual test conditions. Constant vertical load is applied on the top of the wall panel and then lateral load is applied in incremental manner. The in-plane deformation is recorded under each incremental lateral load. Displacement ductility factors and response reduction factors have been evaluated based on experimental results. From the study, it is observed that fully grouted and partially reinforced HCBM panel without opening performed well compared to other types of wall panels in lateral load resistance and displacement ductility. In all the wall panels, shear cracks originated at loading point and moved towards the compression toe of the wall. The force reduction factor of a wall panel with opening is much less when compared with fully reinforced wall panel with no opening. The displacement values obtained by non-linear FE analysis are found to be in good agreement with the corresponding experimental values. The influence of mortar joint has been included in the stress-strain behaviour as a monolith with HCBM and not considered separately. The derived response reduction factors will be useful for the design of reinforced HCBM wall panels subjected to lateral forces generated due to earthquakes.