Veneer Walls Research Articles

Cyclic loading test for brick masonry veneer anchored to reinforced concrete walls

Despite the importance of seismic design for brick masonry veneer anchored to reinforced concrete (RC) backup walls, the effects of several design parameters on the seismic capacity of such nonstructural component remain unexplored. In this study, material tests and cyclic loading tests were performed to investigate the seismic performance of connection for the brick masonry veneer wall anchored to a RC back-up wall under excitation. To this end, tensile tests were first carried out for each element comprising the unit connection to investigate the basic material strengths. A cyclic loading test was then performed on brick-tie-concrete subassembly to investigate the seismic capacity of the unit connection subjected to seismic loads. The major test parameters included the type and embedded depth of veneer anchor, type of mechanical fastener, compressive strength of concrete, and use of insulation. Based on the material strengths and unit specimen strength, the failure mode and seismic capacity of the unit connection for brick veneer anchored to concrete block were evaluated. The test results showed that the presence of the insulation significantly affected the seismic capacity. Based on the test results, design recommendations were proposed to improve the prescriptive design or general design in current practice for brick masonry veneer walls.

Numerical assessment of movement joint spacing in masonry veneer walls with high-strength steel bed joint reinforcement

Numerical assessment of movement joint spacing in masonry veneer walls with high-strength steel bed joint reinforcement

Structural behavior of steel tie connections in masonry veneer walls: Proposal of a simplified approach for practice

Steel ties perform a key structural role in ensuring the stability of buildings façades built with brick masonry veneer walls. These elements are responsible for transferring the loads acting on the veneer wall to the main structure, which typically consists of masonry infill walls used in reinforced concrete frames buildings. Such constructive system is common in Portugal and other Mediterranean countries where the seismic hazard is high. In the event of an earthquake, the ties have to transfer the out-of-plane loads and are subjected to significant tension and compression stress. The characterization of the seismic behavior of these tie connections is an insufficiently explored topic. Despite the codes available for the design of brick masonry veneers and ties, recent earthquakes brought to light the seismic vulnerability of this constructive system. The present paper proposes a simplified spring numerical model validated with experimental results. The simplified model can be applied to perform numerical analyses of greater scale (e.g. to analyze full façades of buildings), which can help to optimize the design. Finally, the paper identifies a common construction problem, which is the probable misalignment of the mortar joints of the masonry walls. A construction solution is proposed by the authors.

Shaking table tests of veneer masonry wall retrofitted with long-rawlplug screw anchors

Veneer masonry walls are vulnerable to lateral forces such as seismic loads, and their failure has caused human casualties and property damage. This study developed a new anchor for existing veneer walls and evaluated its seismic performance using shaking table tests. The presence or absence of retrofit anchors, combination of anchors and steel strips, and anchor spacing were considered as the experimental variables. Out-of-plane excitation was applied to the specimens, and the magnitude of the seismic acceleration was calculated according to the required response spectrum defined in ICC-ES AC156. The experimental results showed that overturning occurred on the non-retrofitted veneer wall; however, the veneer wall reinforced using the proposed anchor exhibited no overturning. The peak ground acceleration, relative displacement, amplification coefficient, and shear force of the reinforced specimens decreased relative to those of the unreinforced specimens. Notably, the proposed method achieved a high seismic reinforcement performance even when the anchor spacing was set to 800 mm.

Failure analysis and structural reliability of unreinforced masonry veneer walls: Influence of wall tie corrosion

Corrosion appears to be a very common problem in historical and aged structures with steel ties and anchorages. A potential rapid deterioration of the wall tie due to the corrosion leading to a premature structural failure poses a serious threat to the built heritage infrastructures’ safety. This paper describes an overview of the probabilistic failure analysis of the unreinforced masonry (URM) veneer wall system with flexible backup under uniformly distributed out-of-plane loadings. Moreover, a framework is proposed to consider the wall tie corrosion in the stochastic finite element analysis (FEA) while estimating the structural reliability. A probabilistic experimental study where 18 full-scale URM veneer wall systems with theoretically identical geometries and properties were tested under inward and outward lateral loading. Wall failure statistics along with the probabilistic characterisation of veneer wall constituent materials including mortar, wall tie and timber were accomplished. A stochastic computational model was then developed which combines the FEA and Monte Carlo simulation to evaluate the failure progression and system peak load (veneer capacity) while considering the spatial variability of veneer wall material properties. Two scenarios, with and without wall tie corrosion, are considered, and the probabilistic characterisation of the veneer capacities for these scenarios under inward and outward out-of-plane loading is also reported. The model error statistics were combined with the probabilistic load models to determine the reliability index corresponding to the Australian Standard for Masonry Structures AS 3700. Annual reliabilities are compared to target reliabilities recommended by ISO 2394. Capacity reduction factor and design minimum tie strength consideration for corroded wall tie is also discussed.

Wind-driven rainwater penetration through brick veneer with and without surface treatments

Rainwater penetration through building enclosures is a critical factor affecting building performance and durability. Understanding and assessing rainwater penetration and its prevention through the brick veneer and brick wall is crucial to controlling and avoiding moisture-related problems such as fungal growth and damages in interior structural elements. Addition of a layer of clay bricks as a cladding (veneer) to the exposed surface of a building envelope is a common practice in Canada. Though clay brick veneer provides adequate weather resistance for the building, it does not offer complete resistance to wind-driven rainwater penetration unless other measures such as surface treatment or additional layer of cladding is incorporated. Hence, studying the aspects of resistance to water penetration of commonly used cladding systems is of utmost importance. This paper presents outcomes of an experimental study conducted to determine water penetration of brick veneer specimens with two different initial rate of absorption values, two void amounts, and three different surface treatments. The study found that the surface treatment is a viable method for improving the resistance of water penetration inside the building envelope and the plastering was found to be the most effective method. The study also found that the initial rate of absorption and thickness of the bricks affect the water penetration; however, void amount in the brick does not affect much on water leakage of the masonry walls. • This paper presents various options to minimize and stop water penetration into the building envelope. • Three different surface treatments of brick veneer on rainwater penetration were studied. • Surface treatment with plaster is able to completely prevent water penetration. • Between the two water repellent treatments, water-based water repellent showed a better performance. • The paper also presents effect of IRA and void percentage of clay bricks on rainwater penetration.

Trends in Residential Building Materials in the State of Victoria

As the population in Victoria continues to grow, there has been a corresponding increase in building approvals across the State. Houses characterised as low-rise residential buildings often take the largest share of these approvals, with incessant residential building activities being driven by record low interest rates. Low-rise residential buildings comprise various building forms that use a number of specified construction materials to construct the building envelope and other structural and non-structural elements. As materials used for constructing residential building envelopes continue to evolve, these materials must be fit for purpose, and satisfy design criteria and performance requirements, while being aesthetically pleasing. This research analyses the trend in construction materials used in building envelopes of low-rise residential buildings using data from building permits issued between 1996 to 2019. The trend analysis shows that traditional double brick wall systems and suspended timber floors have reduced in popularity for houses built in the 21st century. The analysis also shows that brick veneer wall cladding systems built over slab-on-ground footings is the dominant construction form while the roof cladding material is influenced by geographical location. Insights from the data analysis indicate very little innovation has emerged in materials for residential building envelopes despite its crucial role in providing thermal comfort for inhabitants. Results from this research will serve as a basis to provide quantitative assessment of the trend in materials resource; provide insights about the impact of new building envelope products on existing industries; and perspectives on materials for future building envelopes.

Resilience of Canadian residential brick veneer wall construction to climate change

Canada employs a prescriptive-based code for residential buildings. The minimum requirements as prescribed in the 2015 National Building Code were developed based on historical climate which was assumed static. It is now evident that the climate is changing and it is anticipated that wind-driven rain events will be more frequent, of longer duration and of increased intensity. These changes may affect the durability of wall assemblies designed following the minimum requirements set in the building code. In this study, the moisture performance of residential wood-framed walls using brick veneer as cladding and meeting the minimum requirements of the National Building Code were evaluated for different climatic regions of Canada. Various types of brick veneer were evaluated using hygrothermal simulations and projected future climate loads. The mold growth index on the sheathing panel was used as performance indicator. Results showed that the future moisture performance of brick veneer walls depends on the brick properties and varies with climatic region. In particular, for brick veneer having relatively high water absorption coefficient and lower vapor permeability, there may be a heightened risk to mold growth in the future if used in locations on the east and west coasts of Canada. As consequence, the minimum requirements for brick veneer walls may need to be reviewed in these locations to ensure their long-term performance.

Mould Growth Risks for a Clay Masonry Veneer External Wall System in a Temperate Climate

To reduce greenhouse gas emissions, nations have introduced energy efficiency regulations for new and existing buildings. This has been considered advantageous as more efficient building envelopes would reduce energy consumed to heat and cool home interiors to within accepted thermal comfort bandwidths. However, as these methods have been adopted, many nations have identified an unintended visible presence of surface and interstitial condensation and mould in new code-compliant buildings. In Australia, it has been estimated that up to 50% of Australian houses constructed in the last decade (2006–2016) have a presence of condensation and mould. Australia introduced its first condensation and mould-related building regulations for new homes in 2019. This paper reports on the hygrothermal and mould growth analysis of the most common low-rise residential external wall system, a timber-framed clay masonry veneer wall. A key component of this paper discusses the application of innovative methods in the Australian context. The external wall’s moisture accumulation and mould growth were simulated for a period of ten years using the transient hygrothermal simulation tool, WUFI® Pro, and the mould growth model, WUFI® VTT. This study identified significant risks for this typical external wall system when constructed in a temperate climate.

Fire resistance of external light gauge steel framed walls with brick veneer cladding

This paper presents the details of an experimental study to evaluate the fire resistance of external light-gauge steel-framed (LSF) walls with brick veneer cladding. Brick veneer is one of the most opted external cladding in Australian low to mid-rise construction for their aesthetic appeal with load bearing light-gauge steel framing or timber framing as the structural backing. However, no experimental data is available on the fire resistance of brick veneer walls with LSF backing. This experimental study included five small-scale non-load bearing fire tests of LSF walls with brick veneer cladding exposed to the standard fire. Two test walls with brick veneer constructed using normal and high temperature mortars were tested with fire from the external side (brick veneer exposed to fire), and the third wall constructed using normal mortar was tested with fire from the internal side (plasterboard exposed to fire). The first two test walls were also exposed to a second fire exposure. This study also included detailed elevated temperature thermal property tests of brick and the two types of mortar used in the fire tests. Brick veneer cladding provided very good protection to the thin-walled steel studs. No failure was observed in all the five fire tests giving fire resistance level of more than 240 min. Structural failure times of load bearing walls were also estimated to be more than 240 min for fire on the external side under load ratios of up to 0.4 while it was 30 min for fire on the internal side.

Spatial variability and stochastic finite element model of unreinforced masonry veneer wall system under Out-of-plane loading

Inconsistency in the quality of workmanship, the weather during construction, and materials may result in the high unit-to-unit spatial variability of mechanical properties in the same masonry structure. This paper develops a numerical modelling strategy and focuses on the stochastic assessment of unreinforced masonry (URM) veneer walls with spatially variable wall constituent material properties subjected to out-of-plane loading. 3-D finite element modelling of experimentally tested veneer walls was conducted using a micro-modelling approach combined with the Monte Carlo Simulation technique. Spatial stochastic finite element analysis considered the spatial variability of the properties of the wall components (mortar flexural tensile strength) and compared them with non-spatial analysis. The non-spatial analysis overestimates the wall system failure compared to spatial analysis, and the spatial analysis is considered to more realistically represent the variabilities of the URM veneer wall system. Sensitivity analysis is conducted to check the sensitivity of the veneer system behaviour to variability in the various input parameters. The variability of experimental results obtained in a parallel study are quantified and compared with stochastic finite element analysis (SFEA) results. The SFEA model developed in this study can estimate the behaviour and system peak load reasonably and are considered to be from the similar population as test results. Model errors are also included to assess the efficiency of the SFEA model.

Numerical Simulation of the Tension–Compression Behavior of Tie Connections in Brick Masonry Walls

Brick masonry veneer walls connected to infill walls inserted in a reinforced concrete (RC) frame are a common constructive system in Portugal. The stability of the veneer wall is ensured by ties that make the connection with the masonry infill walls. These ties enable the transferring of out-of-plane loads to the main structure due to wind, and particularly due to earthquakes. However, the characterization of the seismic behavior of these tie connections is an insufficiently explored topic. The present paper shows a numerical investigation that aims to simulate experimental results of tension and compression tests performed on masonry prisms connected by means of steel ties. The main objective of the present research is to obtain a better understanding of the complex structural behavior of this specific construction system to then develop simplified numerical tools to be used in engineering practice for the seismic design and retrofitting of brick masonry veneer walls. The numerical results match well the experimental ones, and the validated approach can be used in the future to carry out parametric analyses to evaluate the influence of material and geometric properties of the tie and masonry, as well as the type of action and construction details.

Monte-Carlo laboratory testing of unreinforced masonry veneer wall system under out-of-plane loading

This paper presents the results of a probabilistic experimental study into the behaviour of full-scale unreinforced masonry (URM) veneer walls with flexible backup subjected to out-of-plane loading. The actual safety and reliability of the contemporary Australian URM structures are unknown due to the absence of information regarding the probabilistic behaviour of the whole veneer wall system and material characterisation of the wall constituent materials. The study focused on masonry typologies representative of modern URM buildings in the Australian context. In this study, 18 full-scale URM veneer wall systems with theoretically identical geometries and properties were tested under inward and outward out-of-plane loading. For each loading type, one specimen was tested under semi-cyclic loading to check whether the monotonic loading can capture the overall behaviour of the cyclic response. For each mortar batch mixed, bond wrench testing was conducted at the same age as the test for the associated wall constructed using that mix. Batch to batch variabilities were statistically analysed, and probability distributions for flexural tensile strength were established. Lognormal distributions with aggregated means of 0.40 MPa and 0.42 MPa for inward and outward loading, respectively, were estimated for flexural tensile strengths. After the wall tests, all timber studs used to build the veneer walls were tested to evaluate the probabilistic characterisation of timber stiffness. This probabilistic information is essential for a stochastic finite element analysis (FEA) to conduct the reliability analysis. From the wall tests, veneer wall system behaviour was observed and measured until the collapse or 20% post-peak drop of the peak load. Outward loaded specimens exhibited higher variabilities for masonry cracking and system peak load compared to inward loading due to variabilities from materials, testing arrangements and failure mechanism. The true coefficient of variations of system peak loads were calculated as 0.10 and 0.19 for inward and outward loadings, respectively, considering the effect of testing variability.

Numerical assessment of movement joint spacing in masonry veneer walls with high-strength steel bed joint reinforcement

Numerical assessment of movement joint spacing in masonry veneer walls with high-strength steel bed joint reinforcement

Probabilistic constitutive law for masonry veneer wall ties

ABSTRACT In a masonry veneer wall system, tie strengths and stiffnesses vary randomly and so are not consistent for all ties throughout the wall. To ensure an economical and safe design, this paper uses tie calibration experimental approach in accordance with the standard AS2699.1 to investigate the tie failure load under compression and tension loading. Probabilistic wall tie characterisations are accomplished by estimating the mean, coefficient of variation and characteristic axial compressive and tensile strength from 50 specimens. The displacement across the cavity is recorded, which resulted the complete load versus displacement response. Using the maximum likelihood method, a range of probability distributions are fitted to tie strengths at different displacement histogram data sets, and a best-fitted probability distribution is selected for each case. The inverse cumulative distribution function plots are also used along with the Anderson-Darling test to infer a goodness-of-fit for the probabilistic models. An extensive statistical correlation analysis is also conducted to check the correlation between different tie strengths and associated displacement for both compression and tension loading. Based on the findings, a wall tie constitutive law is proposed to define probabilistic tie behaviour in numerical modelling.

Effects of climate change on the moisture performance and durability of brick veneer walls of wood frame construction in Canada

The objective of this study was to assess the potential effects of climate change on the moisture performance and durability of red matt clay brick veneer walls of wood frame construction on the basis of results derived from hygrothermal simulations. One-dimensional simulations were run using DELPHIN 5.9 for selected moisture reference years of the 15 realizations of modelled historical (H: 1986-2016) and future (F: 2062-2092) climate data of 12 Canadian cities. The mold growth index at the outer layer of the OSB sheathing panel was used to compare the moisture performance under H and F periods. Results for the base design that meet the minimum requirements of the National Building Code of Canada showed that cities within the interior of the country, characterized by a low annual rainfall, are less likely to develop significant mold growth under H and F periods, whereas cities in coastal areas, characterized by high annual rainfall, present a heightened risk to mold growth under both H and F periods. For cities located on the west coast, a possible solution could be to use a 38-mm ventilated drainage cavity as this measure would help dissipate moisture from within the cavity. On the east coast, apart from using a 38-mm ventilated drainage cavity, other measures aiming at reducing the wind-driven rain deposition (i.e., increasing overhang ratio or the height of the roof) could be introduced. However, the feasibility of such measures needs to be considered in respect to whether these are to be implemented as part of a new building or retrofit of an existing one.

Design, Detail, and Attachment of Shelf Angles to Concrete and Masonry

AbstractShelf angles are attached to the structural system and are designed and detailed properly to provide support for veneer walls. They are secured to concrete or masonry structural systems thr...

A service life model of metal ties embedded in the mortar joints of brick veneer walls with applications to reinforced concrete

The issue regarding the corrosion of steel ties connecting brick veneer to a structural backing is well documented. In this paper, the predicted corrosion rate and resulting service life estimates, produced by a time-stepped service life model developed in Visual Basic for EXCEL, for metal ties embedded in mortar, are compared with the empirically determined corrosion rates and service lives of 16 zinc galvanized tie specimens taken from 13 buildings located in 6 different Canadian cities. This tie service life model, coined the “Tie Service Life Predictor”, correlates the external environment of the building to the tie life. As with most corrosion models for steel embedded in concrete (or mortar), the model is broken into two distinct phases: corrosion initiation using Fick’s law of diffusion and corrosion propagation. By considering the mortar surrounding the tie as the tie’s atmosphere, the Tie Service Life Predictor characterizes the microenvironment (atmospheric conditions) surrounding the tie from the macroenvironment conditions. Once the atmospheric conditions were established, the ISOCORRAG atmospheric corrosion model could be used to predict the corrosion rate of zinc galvanized steel ties embedded in the mortar joints of the exterior wythe of brick veneer wall systems. The methods used to create the Tie Service Life Predictor could also be applied to service life estimation of reinforcing steel in concrete structures such as bridge decks and parking structures.

Protection of masonry veneer walls against driving rain

AbstractThe present article reports on investigations into the protection of masonry veneer walls according to Eurocode 6 against driving rain including consideration of window openings through rain exposure tests on eight test samples with different waterproofing variants. The results were published in the paper “Resistance of Masonry Veneer Walls against Rain Penetration” at the 13th Canadian Masonry Symposium (Halifax, Canada, June 4th – June 7th 2017). At the conference, the paper was awarded the C. T. Grimm‐Award for the best publication worldwide on the durability of masonry. It is summarised in excerpts below.

Experimental assessment of the mechanical behaviour of ties on brick veneers anchored to brick masonry infills

Masonry veneer walls have been used successfully in a wide variety of structures in modern building construction. However, their vulnerability under seismic actions is recognized as the result of poor material selection, design and construction practices. The knowledge of the local behaviour of ties under different loading conditions should provide important information to help in the selection of the most appropriate wall ties, improving seismic performance. An experimental campaign of different brick-tie-brick assemblages subjected to cyclic tension–compression loading is presented in this paper and the results (stiffness, strength, dissipation of energy and failure modes) are discussed in detail.