Masonry System Research Articles

An inter-comparison of a steady-state and transient methods for measuring the thermal conductivity of thin specimens of masonry materials

Recent standardization developments within the European Union relating to masonry and block systems now allow calculation of thermal performance to be undertaken based on the block configuration and reliable values of the material thermal conductivity. In general, to attain the optimum thermal resistance of a block a minimum amount of material is used such that the webs and faces bounding the air spaces are usually of the order of 6—8 mm. However, the current standard measurement methods are not suitable or precise enough for direct measurement on thin specimens cut from blocks. As a result the masonry industry requested that CEN TC89 investigate and recommend candidate alternative methods suitable for standardization. A working group was established and following consideration of the issues involved, including, in particular, the thermal conductivity range, simplicity, small size, and short operating times, two methods were proposed for further investigation. The first was the steady-state guarded heat flow meter and the second the transient hot strip in both its linear and disc configurations. In order to verify their applicability both methods were used in an initial inter-comparison involving a total of nine organizations. Measurements were made at or close to room temperature on uniform thin test specimens fabricated from a batch of one typical masonry material. This article contains details of the distinctive features and suitability of each method for the task, the participants, the material and test criteria, and includes a summary and discussion of the results that includes unexpected effects due to anisotropy in the particular material. Overall, the results were very promising such that a further series of intercomparison measurements is now underway on some typical materials within the total conductivity range for masonry type products.

Compressive behaviour of a new reinforced masonry system

This paper presents the behaviour in compression of an innovative reinforced masonry system. The system is made of horizontally perforated units, having common steel bars or prefabricated trusses as horizontal reinforcement. At the wall edges or crossings, confining columns for vertical reinforcement are built with vertically perforated units. Experimental tests, aimed at obtaining basic mechanical characterisation of the construction system, were performed on single constitutive elements i.e., confining columns and masonry panels made of horizontally perforated units, and on completed reinforced masonry walls. Non-linear numerical models, interpreting stress and strain distributions, were developed on the basis of the results. In particular, this paper presents: (a) results of compression tests on columns, masonry panels, and complete reinforced masonry system; (b) comparison of walls built with two types of horizontal reinforcement; (c) outcome of numerical models; and (d) effectiveness of various design equations to evaluate the compressive strength of the system.

Test Method for Determining the Efflorescence Potential of Masonry Materials Based on Soluble Salt Content

Abstract A single test method that is capable of determining the efflorescence potential for all materials in a masonry system is needed. The need for preconstruction testing is referenced in ASTM C1400-1—“Standard Guide for Reduction of Efflorescence Potential in New Masonry Walls”—but the standard acknowledges that there is not a suitable test method for all masonry materials. In the past, soluble salt measurements have been used to quantitatively access the efflorescence potential of masonry materials. To determine the water-soluble salt content of masonry materials, a simple leaching procedure was developed to remove the salts followed by quantification of the water-soluble salt content by ion chromatography. A series of modified efflorescence tests using salt solutions and real masonry materials has been used to determine the significance of water-soluble salt measurements. A clear threshold for soluble sulfate content that indicates a high potential for the development of visible efflorescence has been identified. Sulfate salts are the most common water-soluble compounds associated with efflorescence complaints.

Toughness of fibre reinforced hydraulic lime mortar. Part-1: Quasi-static response

There are several stone masonry structures of historical importance in Canada that lie in regions of varying degrees of seismicity. Hydraulic lime mortars are used in the repair of such heritage buildings. While this mortar works as a sacrificial element in the stone masonry system, a tougher and more durable mortar is expected to offer the best repointing binder. This paper reports the results of a study on the compressive, flexural and shear toughness of plain and fibre reinforced hydraulic lime mortar. Polypropylene micro-fibres were incorporated at 0, 0.25 and 0.5% volume fraction. As expected, hydraulic lime mortar was seen to be weakest in flexure. However, fibres were effective in increasing the flexural toughness as well as the shear strength.

Improving the Thermal Resistance of Brick Masonry Systems

Abstract Finite element modeling was used to relate the coring or cell configuration of brick to the heat flow through brick masonry wall systems. Core or cell configurations that minimize thermal bridging through the brick thickness substantially reduced the heat flow through the masonry. The effect of bed depth on heat flow was also investigated. Larger units with optimized coring designs resulted in substantial reductions in heat flow. Heat flow through the mortar joint was also compared to heat flow through the brick. Wall designs that minimize the mortar joint thickness also reduce the heat flow. From these simulations, it is clear that a masonry system can be optimized to reduce heat flow. The effect of core or cell filling with various materials was also studied. Insulating materials reduce heat flow primarily by displacing mortar in the cores or cells.

Detailing Masonry Veneer/Steel Stud Backup Systems at Fenestration Systems to Avoid Moisture Problems

Abstract Through more than 20 years of investigating water leakage and condensation problems, the authors have observed that a high percentage of moisture problems related to masonry walls are associated with the interface between masonry veneer and fenestration systems. These problems are often associated with wall systems in aggressive exposures where the drainage system and air seal details at interfaces are not adequately considered by the designers and contractors. In many cases, drainage systems are not provided or not properly installed at joints between these systems. Air barriers and vapor retarders often are not sealed to fenestration systems or contain voids that permit the flow of air into the wall system. Problems can occur when anchors, lintels, support angles, and sill flashings are either not thermally improved or where the location of thermal breaks is not coordinated with the location of insulation within the walls. This paper outlines considerations for detailing the interface between masonry veneer over steel stud wall systems and fenestration systems. The fenestration systems reviewed in this paper include typical storefront or operable windows and curtain walls. Both masonry systems with the insulation positioned within the stud space and systems with the insulation positioned within the masonry air space are discussed.

Ensayo en Lima (Perú) de edificio de adobe sismorresistente construido con el sistema de albañilería integral

This paper presents an adaptation of the Integral Masonry System (IMS) developed in Europe under the “AllWall System” trade name for concrete or clay, block or brick masonry walls using just mortar. In this case the system is modified for an adobe block infill to allow the construction of earthquake resistant housing in developing countries. When adobe block is employed as an infill it is impossible to transfer the bond stresses of the reinforcement bars as these structures are not bonded with mortar and the reinforcement then has to transfer the stresses purely within the reinforcement. The truss-shaped reinforcement may intersect in the three spatial directions and allow the construction of reinforced walls and slabs. It is then only necessary to infill with locally made adobe blocks or flooring in order to provide sufficient rigidity to the structure. A two-storey, 6x6x6 m, adobe building employing the IMS system has been tested for earthquake resistance at half scale at the PCUP (Pontificia Universidad Catolica del Peru) in Lima in collaboration with the UPM (Universidad Politecnica de Madrid) to test the viability of this new type of building construction for seismic areas in the Third World. The test results have shown that the IMS system with adobe block remained stable without significant cracking even under 130 mm displacement seismic movement, equivalent to 10.0 on the Richter magnitude scale.

Evaluation of Masonry Deep Beams Externally Strengthened with CFRP Sheets

In this study, carbon fiber-reinforced polymer (CFRP) sheets were examined as a means to strengthening existing masonry walls allowing for efficient creation of doors, windows, and passage openings. The research reported here deals with eight masonry walls made with concrete blocks, subjected to three-point quasistatic loading. The parameters examined include the reinforcement configuration and their amount. While CFRP sheets were used as external reinforcement, companion studies were carried out with conventional steel rebars. Test results indicate an increase of 180% in shear strength of the reinforced walls as compared to reference unreinforced walls. Load-deflection relationships indicate that the combined plain masonry and CFRP laminate system possessed some nonlinear deformability. The use of CFRP laminates on the walls was found to have an influence on the mode of failure. Anchoring the CFRP laminates at both support regions helped in using a larger portion of the strength of the laminates. The rei...

Ultra low U-value walls for low-carbon-dioxide homes

This paper describes various walling systems capable of providing an ultra low U-value wall construction for use in a domestic application. The target U-value is 0·11 W/m2K −36% less than the minimum requirement for the German ‘Passivhaus’ standard and some 60–70% more onerous than current UK building regulations; this value was chosen because of the high degree of challenge it presents whilst remaining technologically achievable. The paper briefly discusses whether static U-value is truly relevant to most domestic applications in the UK, or whether it is the less understood dynamic U-value that should be the focus of attention. The positive and negative characteristics, including wall thicknesses, embodied energy, toxicity, expected lifespan and ease of installation, of various systems are discussed. Test data provided by manufacturers to support U-value claims are carefully examined. The walling systems discussed cover a broad range of technologies, including structural insulated panels (SIPs), vacuum insulation panels (VIPs), insulating concrete formwork, traditional cavity wall masonry, external insulation of masonry and cellulose-based systems such as straw. The paper concludes by summarising the benefits of each system type and recommending applications that are particularly suitable for each type of wall.

Nonlinear finite element analysis of grouted and ungrouted hollow interlocking mortarless block masonry system

The main feature of the interlocking hollow block masonry is the replacement of mortar layers commonly used in bonded masonry with interlocking keys (protrusions and grooves). This study covers the modelling and the analysis of interlocking mortarless ungrouted (hollow) and grouted concrete block system subjected to axial compression loads using FEM. The main features simulated in the developed finite element code are the mechanical characteristics of the interlocking dry joints including the geometric imperfection of the shell beds of the blocks, the interaction between block units, the progressive debonding between the block and grout and material nonlinearity. The applicability of the proposed FE model is investigated by demonstrating the nonlinear structural response and failure mechanism of individual block, ungrouted and grouted interlocking mortarless prisms. The results found show good agreement with the experimental test results.

Innovative seismic design of a post-tensioned concrete masonry houseThis article is one of a selection of papers published in this Special Issue on Masonry.

Post-tensioned concrete masonry walls provide improved seismic performance, but have had limited application in seismic regions because of a lack of research pertaining to their in-plane response. Following focused research over recent years, a consortium of product suppliers has collaborated with the University of Auckland to construct New Zealand’s first post-tensioned concrete masonry house. A feature of this innovative design was that all incorporated products were commercially available, with no proprietary products being specifically developed for the prestressed masonry system used. Consequently, it is hoped that this house will be a showcase, and provide exposure for the technology in New Zealand and elsewhere. This paper provides a brief review of previous post-tensioned concrete masonry research applications, then discusses post-tensioning details and their application to house design and construction.

Behavior of Interlocking Grouted Stabilized Sand–Fly Ash Brick Masonry under Uniaxial Cyclic Compressive Loading

An experimental investigation of the behavior of interlocking grouted stabilized sand–fly ash brick masonry under unaxial cyclic compressive loading with different bed joint orientation is presented. Five cases of loading at 0, 22.5, 45, 67.5, and 90° with the bed joints were considered. The brick units and masonry system developed by Professor S. N. Sinha are used in the present investigation. Eighteen specimens 500 mm×100 mm×700 mm and 27 specimens 500 mm×100 mm×500 mm were tested. The envelope stress-strain curve, common point curve, and stability point curve were established for all five cases of loading with respect to the bed joints. A general analytical expression is proposed for these curves which fit reasonably well with the experimental data. It was inferred that the peak stress of the stability point curve may be considered as the maximum permissible stress level and is found in the range of 0.745–0.775 times the masonry strength depending upon the load case. It was also inferred that the permi...

Finite element analysis of interlocking mortarless hollow block masonry prism

Interlocking mortarless masonry system has been developed as an alternative system for the conventional bonded masonry. This paper covers the analysis of interlocking mortarless hollow concrete block system subjected to axial compression loads using FEM. An incremental-iterative finite element code is written to analyze the masonry system till failure. The stress–strain relation obtained from test is employed and equivalent uniaxial strain concept is used to account for the material nonlinearity in the compression stress field. The developed program is also capable of simulating the nonlinear progressive contact behaviour (seating effect) of dry joint taking into account the block bed imperfection. The comparison shows a good agreement between the developed FE program and the experimental test results.

Computational Analysis of Masonry Structures with a Funicular Model

This paper presents a computational approach for the assessment of masonry structures based on the well known analogy between the equilibrium of arches and that of hanging strings or cables working in tension. According to the analogy, the hanging strings model the inverted shape of the equilibrium lines (or thrust lines) describing the locus of the equilibrium forces acting across the sections of the arch. The approach proposed combines two developments. First, a new cable element is proposed to numerically model the strings used to describe the equilibrium lines. The formulation proposed, obtained as a modification of the conventional equations for inextensible cables, is based on an exact analytical derivation. Compared to other available numerical approaches, it has the advantage of ensuring the exact equilibrium of the cable net after deformation. Second, complementary algorithms are proposed for the assessment of the strength of masonry structures by the application of the limit theorems of plasticity (static approach). These algorithms are intended to find optimized solutions complying with the so-called safe (or lower-bound) and uniqueness theorems. Two examples of application are described to illustrate the accuracy of the method and its ability to handle masonry structural systems.

Structural Behaviour of Mortar-Less Interlocking Masonry System under Eccentric Compressive Loads

Interlocking masonry wall as a structural load-bearing element is still unexplored simply because its basic behaviour and complete response to failure is not known. In addition, there is no design code available to provide necessary guidance for a safe design of interlocking walls. This paper provides an attempt to ascertain the structural response of interlocking masonry walls compared to conventional bonded walls. Individual block units, prisms and full-scale wall specimens were tested under the action of concentric and eccentric compressive loads. The effect of different patterns of reinforced concrete stiffeners has also been investigated. The test results were discussed in terms of wall efficiency, strength capacity, deflection, strain distribution, cracking patterns and failure modes. The results indicate a promising future use of the interlocking masonry system in construction.

Influence of bed joint orientation on interlocking grouted stabilised mud-flyash brick masonry under cyclic compressive loading

This paper describes a series of laboratory tests carried out to evaluate the influence of bed joint orientation on interlocking grouted stabilised mud-flyash brick masonry under uniaxial cyclic compressive loading. Five cases of loading at , , , and with the bed joints were considered. The brick units and masonry system developed by Prof. S.N. Sinha were used in present investigation. Eighteen specimens of size and twenty seven specimens of size were tested. The envelope stress-strain curve, common point curve and stability point curve were established for all five cases of loading with respect to bed joints. A general analytical expression is proposed for these curves which fit reasonably well with the experimental data. Also, the stability point curve has been used to define the permissible stress level in the brick masonry.

Fatigue behaviour of interlocking grouted stabilised mud-fly ash brick masonry

A series of laboratory tests have been conducted to investigate the fatigue behaviour of interlocking grouted stabilized mud-fly ash brick masonry. Three cases of loading at 0°, 45° and 90° to the bed joints are considered. The brick units and masonry system developed by Sinha is used in present investigation. Eighteen specimens of size 500 mm × 700 mm × 100 mm and nine specimens of size 500 mm × 500 mm × 100 mm are tested. For each of three levels of minimum stress, the number of cycles to failure is determined for each of various maximum stress levels considered. The fatigue study presented here is limited to approximately 8000 load cycles. For the range of tests considered, it is found that the effect of repeated compressive loading can cause reduction in the compressive strength of brick masonry as high as 25%.

Behaviour of interlocking mortarless block masonry

Various types of interlocking mortarless (dry-stacked) block masonry system have been developed worldwide. However, the characteristics of dry joints under compressive load, and their effect on the overall behaviour of the interlocking mortarless system, are still not well understood. This paper presents an experimental investigation into the dry-joint contact behaviour of masonry and the behaviour of interlocking mortarless hollow blocks for grouted and ungrouted prisms under compression. Two experimental test set-ups are proposed to evaluate the contact behaviour of dry joints, considering the geometric imperfections in the contacting faces. The results show that the contact behaviour of a dry joint is highly affected by geometric imperfections in the block bed. Different patterns of deformation are distinguished in mortarless hollow (ungrouted) and grouted prisms. Dry joints predominantly affected the hollow prism deformation until the compressive load reaches 0·57 of the maximum load. However, this behaviour is not common in grouted prisms, because noticeable deformation commences after 0$38 of the maximum load. Furthermore, the variations of strength and deformation in grouted specimens are diminished compared with those in ungrouted specimens.

Loading–unloading curves of interlocking grouted stabilised sand-flyash brick masonry

Loading–unloading and reloading stress–strain curves of interlocking grouted stabilised sand-flyash brick masonry under uniaxial cyclic compressive loading are presented. Five cases of loading at 0°, 22.5°, 45°, 67.5° and 90° to the bed joints are considered. The brick units and masonry system developed by Prof. S.N. Sinha is used in present investigation. A mathematical model to describe the Loading–unloading–reloading response of this masonry system is proposed. The model accounts for the effect of residual strain on the cyclic compressive behaviour. The model uses simple polynomial functions. The loading and unloading curves are transformed to a normalised co-ordination system on which all the curves plot within a narrow range. A parent polynomial is developed to fit the curve on this coordinate system. Then individual reloading and unloading curve are obtained by transferring the parent equation to the stress–strain coordinate system. The present model for Loading–unloading and reloading curves compare well with the experimental data for five cases of loading under consideration.

Durability of masonry systems: A laboratory study

We deal with the textural aspects, porometry and hydric behaviour of combinations of building materials and their durability under attack by salt crystallisation and freezing. We selected 4 types of lime mortar (pure lime mortar, lime mortar + air-entraining agent, lime mortar + pozzolana and lime mortar + air-entraining agent + pozzolana) which were used in combination with either brick or calcarenite stone. Lime mortars were chosen because they are compatible with traditional building materials, including the bricks and calcarenites that were widely used in the historical buildings that make up our architectural heritage. There are more similarities between the pore size ranges in calcarenites and mortars than there are between those in bricks and mortars. In all cases, a fine layer of calcite microcrystals develops at the contact surface between the mortar and the stone or brick. This is produced by the transformation of the portlandite, which concentrates in this area due to capillary moisture migration. This surface may on the one hand represent an obstacle to the flow of water between the different parts of the system formed by these materials, but on the other it may also favour greater adherence between the components, especially in the calcarenite + mortar combination, which proved to be the most resistant to deterioration in the freeze–thaw tests.