Tatheer Zahra

Queensland University of Technology | QUT · School of Civil and Environmental Engineering

Reinforced concrete (RC) shear walls are primarily designed to resist lateral actions in buildings, in addition to carrying the vertical loads from above. Recent changes in the Australian concrete standard (AS 3600) enforces RC walls to have double layers of reinforcement in the horizontal and vertical directions to be considered as ductile walls,...

The provisions related to design of reinforced masonry (RM) walls subjected to axial compression have recently been revised in the Australian Masonry Standards (AS 3700). Especially, the provisions pertaining to lateral ties have been relaxed, where if the vertical reinforcement bars are surrounded by a compacted grout annulus of at least two times...

The provisions pertaining to detailing of reinforced masonry (RM) walls in Australian Masonry Standards (AS 3700) are mainly drawn from Australian Concrete Standards (AS 3600). Recent changes in the AS 3600 specify that the reinforced concrete (RC) shear walls should have double layers of reinforcement (horizontally and vertically) to achieve a duc...

Reinforcing bars are often embedded into cement mortar layers (bed joints and surface bonded) of masonry structures to enhance their structural performance to various effects. However, there is limited research available on the bond characteristics of steel bars embedded in the masonry mortars. This study was focused on assessing the bond stress an...

Masonry construction is popular around the world, but the use of mortared masonry presents numerous challenges. In recent decades, masonry construction systems incorporating interlocking masonry units have been proposed to eliminate mortar. The interlocking between masonry units can be achieved using specially shaped units. This paper presents a co...

Reinforced concrete (RC) columns are critical elements in a building frame and their failure would have serious consequences that may lead to complete collapse of the structure. Corrosion is one of the primary reasons for the deterioration of reinforced concrete columns. Although plenty of experimental studies have been conducted to assess the perf...

Bonded brickwork used for loadbearing walls is widely found in heritage structures worldwide. The evaluation of bonded masonry structures and their strengthening strategies against dynamic actions require appropriate understanding under cyclic loading. Subsequently, a simplified 3D microscale numerical model is developed in this paper to analyse bo...

Confinement of masonry columns using fibre reinforced polymer (FRP) composites have displayed to enhance the axial capacity and ductility. Although, mechanisms of FRP confined masonry column (CMC) subjected to monotonic compression loading with various configurations have been investigated and rational design rules were developed, the response of F...

Auxetic materials, possessing negative Poisson’s ratios (NPRs), have the ability to shrink (or expand) in the lateral direction under an axial compressive (or tensile) force respectively. Due to this unique feature, an auxetic material is found to sustain high energy absorption capacity, fracture toughness and shear resistance and thus regarded as...

This paper summarises the development of a state-of-art impact testing machine for simulating impacts such as vehicular crashes or debris impacts onto structures. The machine has a 200 kg pneumatically powered projectile which can travel horizontally within the barrel of the machine with a maximum velocity of 50 m/s to impact the target structure....

Lateral restrainers are traditionally provided in reinforced masonry (RM) walls to prevent the vertical steel bars from buckling. In the current version of the Australian Masonry Standards (AS 3700–2018), the use of lateral restrainers in RM walls is relaxed, if the vertical rebars are surrounded by grout annulus of twice the diameter of the bars....

Hollow block masonry buildings constructed alongside busy roads are vulnerable to vehicular impacts resulting in damage to property and harm to the building and vehicle occupants. This paper presents a method for the design and insertion of various forms of geometrically modified auxetic foam structures inside the hollow cores of block masonry wall...

This paper presents the development of 3D finite element (FE) technique to model and analyse reinforced masonry (RM) walls under axial compression. The Arc-length algorithm integrated with initial geometric imperfection has been used to model the geometric nonlinear response of both the embedded steel and that of the RM wall to allow for the occurr...

The provisions pertaining to design of reinforced masonry (RM) walls under axial compression in the Australian masonry standard AS 3700 (2018 version) have been revised based on the recent findings that the lateral restraining ties do not significantly affect the performance under axial compression. The other design codes such as Canadian (CSA S304...

Vehicular crashes into buildings seem to be an on-going problem with severe consequences. When the building is of masonry, the damage at the impact zone is more severe with possible intrusion of the vehicle into the building, depending on the velocity of impact. In all these cases, vibration is propagated from the impact zone to the wall edges and...

Bonded brickwork loadbearing walls are commonly seen in many colonial period structures around the world; however, most research studies in the past and the current design provisions are primarily based on single leaf brickwork. Due to the anisotropic nature of brickwork, the strength and deformation characteristics would be different for bonded br...

The stress-strain characteristics of reinforced masonry (RM) under axial compression should be correctly understood to effectively analyse and design RM elements. However, past studies have overlooked this aspect and mainly focused on assessing the stress-strain behaviour of grouted or confined masonry. An experimental programme was executed in thi...

Three-dimensional (3D) printing of auxetic materials is an emerging research field due to their intriguing negative Poisson’s ratio (NPR) behaviour which enables improved load resistance than conventional materials for various applications. In this research, re-entrant chiral auxetic (RCA) structures of three different geometries were printed using...

Changes in Australian Masonry Standards and National Code of Construction for reinforced masonry (RM) under compression impress the need of a grout annulus and vertical bar confinement using 6 mm tie bars. Maintaining the verticality and centricity of reinforcement and restraining them with the tie bars is challenging and time consuming. BlockAid h...

Bonded brickwork walls of large thickness constructed with double or triple bricks are common in loadbearing historical masonry structures in many regions which require interventions and compression capacity evaluation. However, current design provisions for compression capacity prediction are primarily based on single brick prisms and wallette spe...

Reinforced masonry (RM) walls are mostly used in low to mid rise residential/industrial buildings in cyclonic and seismic regions. They are conventionally constructed with grout embedded vertical steel reinforcements positioned in the middle of the hollow blocks. However, these reinforcing bars are rarely detailed with lateral restrainers, which ar...

Prefabrication has shown to be an effective way of construction in the modern day context. Although, much progress has been made in developing reinforced concrete (RC), timber and steel prefabricated elements/structures, prefabrication of masonry walling systems have received limited attention in the past. Conventional masonry construction is labou...

This paper reports a study on the failure of masonry walls subject to vehicular impacts. The investigation encompasses a homogenised masonry material model incorporating strain rate effects suitable for impact dynamic applications using a layered shell element formulation in an explicit finite element framework. As the focus of the study is on the...

Auxetic materials have counteractive properties due to re-entrant geometry that enables them to possess Negative Poisson's Ratio (NPR). These materials have better energy absorbing and shock resistance capabilities as compared to conventional positive Poisson's ratio materials. The re-entrant geometry can be created through 3D printing for convenie...

The lateral confinement of masonry columns using composites have shown to improve their strength and ductility. Although, several research studies were focused on investigating the monotonic compression behaviour of confined masonry columns in the past, their cyclic compression characteristics, which are necessary for seismic and dynamic analyses,...

This paper aims to assess the strength of a 100 + year old masonry arch bridges in Australia that are currently in operation and routinely subjected to train loadings. Towards this end, 45 cores of 150 mm diameter with varied lengths and joint configurations were drilled from a typical bridge and tested. Out of these samples, 30 were tested under d...

Concrete hollow block masonry is widely used in North American and Australasian countries because it enables to accommodate grouting and reinforcement to resist higher axial and lateral actions, where it ultimately facilitates to construct high-rise masonry buildings. Subsequently only certain grades of mortars are recommended for the concrete bloc...

This paper presents a review of the literature on masonry-infilled frame structures subjected to lateral loads. A database of 167 experimental studies on the parameters that influence the response of masonry infill are first discussed. It is shown that there are far too many geometrical and material parameters that affect the behaviour and that the...

Most masonry arch railway bridges in the world are servicing the communities well beyond their intended design lives. However, these bridges would have undergone numerous deteriorations over the period of several decades of service life. The asset owners of these bridges are confronted with the decision over whether to continue servicing or decommi...

This paper reviews the approach of eleven national codes on the analysis and design of masonry-infilled frames. It is shown that, in general, codes can be divided into two groups. The first group isolates the masonry and frame members by providing gaps to minimize the interaction between them. This method ensures that the complexities involved in a...

Masonry buildings constructed along busy roads are vulnerable to vehicular impacts resulting in damage to property and harm to occupants. This paper presents two strategies that use either carbon fibre or auxetic composite render for mitigating the adverse effects of such impacts and compares the merits of the two strategies. As masonry is a relati...

This paper presents a concept of Interfacial Transition Zone (ITZ) enrichment for the characterisation of masonry under biaxial stress states to a nonlocal transient damage representative volume element (RVE) model developed by the authors (Jelvehpour et al., 2019). ITZ enrichment has been realised through a series of transition layers on either si...

Masonry buildings constructed along busy roads are vulnerable to vehicular impacts. As most of these impacts are likely to occur at low velocity due to severe braking by drivers to avoid catastrophe, the present study reports a failure analysis of masonry walls subject to low velocity impacts. An explicit finite element modelling method incorporati...

Despite the existence of many historic buildings containing drystack walls, this walling system is not regarded as a legitimate masonry in many national standards. Unlike the thick historic drystack walls, the thin contemporary drystack walls require rendering to survive unavoidable eccentricities in the vertical compression loading and lateral loa...

Common building materials including concrete, masonry and mortar are brittle in nature and fractured due to dissipation of energy under extreme loads caused by impact, blast and seismic forces. The structures made of these materials are required to be protected against brittle collapse by maximising the energy absorption. The strengthening and prot...

As the conventional masonry construction is labour and time intensive, it faces challenges from new generation materials and construction techniques. Mortarless masonry system (MMS) is considered as an alternative to conventional masonry as it minimises skilled labour requirement and improves the construction productivity. Despite these advantages,...

Shear walls are critical lateral load resisting elements in buildings. These walls exhibit complex failure modes as they are subject to a combination of vertical compression and in-plane shear loads and are vulnerable to shear dominated failure depending up on their aspect ratio, vertical load to compressive strength ratio and reinforcement ratio....

An experimental investigation on the flexural response of polymer cement mortar matrix overlayed or inserted with carbon fibre or auxetic fabric layers subject to four levels of rates of loading (1–150 mm/min) is reported. Seventy-two specimens made from plain polymer cement mortar, composites with auxetic and carbon fibre fabric layers overlayed a...

This study focuses on the improvement of predictive capabilities of elasto-damage model, initially proposed by Khan et al., for concrete subjected to multiaxial state of stress. The critical energy release rate 𝑅𝑐, which was initially assumed constant, is defined as a function of 𝑓𝑐′, and 𝐸𝑜 in the present study. Parameters 𝛼,𝛽 and 𝛾 used in effect...

Widely reported damage modelling methods inherently use elastic brittle rapidly decaying responses for materials under both uniaxial tension and compression, in spite of the existence of ample experimental evidences that the damaging process under compression is significantly different to that under tension. This paper reports a damage evolution la...

Serviceability deflections and strains at the crown, support, and quarter point of two aged masonry arch bridges under operating passenger and freight trains were assessed using a digital image correlation method. Three lasers recorded the passage of the wheels; these data were used to ascertain the wheel positions, which corresponded well with the...

Contact surface unevenness of the dry-stackable, interlocking blocks adversely affects the constructability of the drystack system. This paper presents the contact surface characteristics of these blocks and strategies for mitigating the unevenness through systematic experimental and numerical studies. First, the contact surface characteristics of...

Masonry boundary walls protect buildings and structures of national as well as common interests from intruding vehicles. As masonry is weak in tension, the impact due to vehicle intrusions induces tensile stresses in the walls resulting local damage failure. Strengthening masonry walls using various forms of Fiber Reinforced Plastics (FRP) can prev...

Application of auxetic materials in automobile and biomedical engineering is widely reported and their usage in civil engineering is emerging. This paper reports the manufacturing and characterising of cementitious polymer mortar – auxetic foam composites suitable for wall rendering. The deformation behaviour of the composites with the high negativ...

A generalised model based on damage mechanics for predicting the response of masonry subjected to compression is presented. The model accounts for the behaviour of the constituents of the masonry, viz., the units, the mortar and the unit–mortar interfaces; in this paper, the unit–mortar interfaces and the mortar layers have been treated as a homoge...

Building structures use brittle materials extensively. Under impact or blast loads these structures perform poorly due to tensile strains caused by Poisson’s effect normal to the direction of such loadings. Auxetic materials exhibit negative Poisson’s ratio – a property which can be exploited to eliminate those tensile strains. In this study, Auxet...

Masonry walls allow easy intrusion of the impacting vehicles into the impacted buildings. The cause of the damage due to vehicular impacts in masonry walls is the generation of tensile stresses due to “Poisson’s effect”. Auxetic foams, due to their negative Poisson’s ratio, can eliminate these tensile stresses. In this study, masonry walls with and...

Interlocking dry stack masonry has several benefits over the conventional masonry because of its ease of construction and higher compressive strength due to the absence of mortar joints. Dry contacting surfaces between the blocks play a major role on the performance of dry stack masonry. In this study, the characteristics of the dry contacting surf...