Two roof structures representing vintage unreinforced masonry (URM) building components were subjected to longitudinal pseudo‐static cyclic loading. The overall roof dimensions were 8.94 m (span) by 3.1 m (length), with each roof incorporating a pair of as‐built timber trusses that were retrieved from two demolished URM buildings. Both roofs were tested first with nailed connections representing original construction and then again with connections that included proprietary metal brackets and straps representing a remediation of the original construction. The loading was applied perpendicular to the trusses, hence parallel to the diaphragm purlins. Damage patterns and deformation profiles were used to interpret the mechanics governing the roof behaviour utilizing existing modelling techniques for timber floors. It was found that the roof behaviour was shear‐dominated, akin to the in‐plane response of timber floors. For the direction of applied loading, both roof stiffness and roof strength were governed by the strength of the connections between the trusses and the diaphragm purlin members and the purlin spacing. Consistent with these findings, a method was suggested to estimate the stiffness and strength of similar roof structures that may have different aspect ratios using the results from the tests. A comparison between the various test results showed that implementing upgrades that were focused on the connections significantly improved the roof stiffness and roof strength.

In this study, a new traction‐separation based constitutive model for use in finite element simulation of masonry joints under complex loading conditions is developed for cohesive elements. The proposed model is formulated using damage parameters and plastic deformation with mutual couplings, and can accurately simulate the complex nonlinear behaviors of masonry joints considering hardening or softening of strength and stiffness degradation. To enhance the numerical stability of the model, plasticity and damage are separated algorithmically and implemented in two phases. In the first phase, the plastic deformations are treated using a multi‐surface plasticity model composed of a smooth hyperbolic yield surface for tension‐shear mixed‐mode failure and an elliptical cap primarily for the compressive failure. This is implemented in effective stress space and helps restrict the evolution of yield surfaces with no softening, significantly enhancing the efficiency of stress return mapping by the closed point projection method. In addition, an adaptive sub‐stepping scheme is adopted to further improve the robustness of the numerical implementation. In the second phase, nominal stresses are computed from the effective stresses using damage parameters. The evolution of these damage parameters is defined in terms of plastic work which is defined by a polynomial form, and is recommended in this study for a better calibration capability. Improvements are made in the formulation of compressive cap including incorporation of hardening of strength and stiffness degradations as these are ignored in existing interface models. This approach helped improve simulation of masonry under cyclic loads with tension‐compression transitions. For the structural level applications, the interface model is implemented within a finite element program, which is utilized to simulate failure of a number of masonry specimens under in‐plane/out‐of‐plane monotonic/cyclic loading. The simulated results are rigorously validated with existing experimental data that shows a good potential in modeling masonry structures.

Ultra-high-performance fiber-reinforced concrete (UHPFRC) has gained a great deal of increasing interest in structural engineering applications, particularly where high ductility, strength, and high impact resistance are of prime concern. This study focuses primarily on the size effects ductility characteristics of UHPFRC with varying fiber concentrations subjected to uniaxial compressive load. It shows how to process the data from compression cylinder tests to extract the size-dependent strain at peak stress to provide a generic size-dependent stress-strain analytical model. For a slenderness factor of 2, the predicted peak stress from the analytical model deviated 0.34%, 0.26%, and 10.5% from the experimental peak stress results for a fiber concentration of 1%, 2%, and 3%, respectively, indicating good estimate of the analytical model with the experimental results. Furthermore, a numerical flexural segmental moment-rotation approach is applied to incorporate an analytical model to quantify apparently disparate UHPFRC member strength and ductility. Tests have shown that it is not the enhancement in the material concrete compressive strength but the phenomenal brittle ductility nature, observed as a result of increasing the slenderness of the specimen; in contrast, a substantial increase in ductility was achieved after crushing of concrete due to the addition of fibers. A size-dependent analytical approach has estimated good fit with the experimental and other published results. Finally, numerical simulation using a segmental approach at the ultimate limit state of rotation dealing with flexural ductility is significantly influenced by the increase in slenderness factor of the specimens and fiber concentrations. This is evident as the rotation capacity decreased by 62% and 75% for a slenderness factor of 3 and 4, respectively, compared to the slenderness factor 2, when the fiber concentration was 1%. Furthermore, for 2% fiber concentration, the decrease was 54%, and 80%, and for 3% fiber concentration, the decrease was found to be 49%, and 79% for the slenderness factor of 3 and 4, respectively in comparison to the slenderness factor 2, suggesting both slenderness factor and fiber concentration have a significant impact on the flexural ductility.

A coupled damage-plastic based constitutive model using a traction-separation law is developed in this study to simulate the behaviour of mortar joints in masonry structural panels subjected to in-plane (2D) and out-of-plane (3D) loading. A smooth hyperbolic failure surface is used to develop the interface material model, which is implemented numerically using a fully implicit backward Euler integration technique is unconditionally stable. To further improve the accuracy and robustness of the interface model, an adaptive sub-stepping scheme and associated consistent tangent operator are formulated considering the effects of damage and plastic deformations. This is beneficial for simulating full-scale masonry structures because the size of load step for some locations with higher deformations can be significantly larger than other locations. The model is first validated using a single cohesive element within a finite-element modelling platform, to assess its behaviour under all possible deformation modes: tensile, compressive with shear and tensile-shear mix-mode behaviour. The cyclic response of a masonry couplet is then simulated to assess model performance in the unloading scenario. Finally, the model is applied to masonry structural walls for simulating their failure response under in-plane and out-of-plane loads, and a good correlation with the experimental results is observed. (C) 2021 Elsevier Ltd. All rights reserved.

A damage plasticity based interface constitutive model for simulating complex mixed behaviour of masonry joints is proposed in this paper. To improve the computational efficiency and robustness of the interface model, a novel modelling strategy is adopted to algorithmically decouple the damage and plastic deformations, which are treated separately in two stages. This approach helps to simulate elastic-perfectly-plastic behaviour in effective stress space and pro-vides a non-evolving yield surface in the first stage which significantly improves the convergence of stress return mapping. In the second stage, a separate function is employed to model the evolution of damage used to quantify stress softening. The interface model is implemented within a finite element code used to analyse masonry structures of different scales/sizes under mono-tonic and cyclic loads. The experimental validation of the simulated results demonstrates good performance of the model in terms of accuracy and robustness. Moreover, the effects of different parameters on the model performance are investigated. One of the key parameters is the degradation of dilation angle incorporated through an energy based evolution function, which is observed to have importance in improving physical response and numerical performance.

For other than minor modifications or additions to existing masonry structures, an understanding of the in-situ mechanical properties of the masonry is required. Estimation of shear strength of the masonry bond is often made using the in-plane shove test as it only requires access from one side of the masonry being tested, and is therefore considered to be only mildly invasive. In-situ and laboratory simulations of the shove tests have however shown that a number of site-specific problems can arise. These include: preparation of the test area which can damage the mortar joints resulting in loss of cohesion, imprecise alignment of both the loading system and instrumentation leading to complications with data interpretation, and without an adequately long section of wall to be tested, flexural cracking and lateral displacement of large wall sections. In an attempt to address these issues, in this paper, an alternative in-situ test is proposed. This new 'pull test' measures shear strength by extracting a single brick orthogonally in the wall's out-of-plane direction. A laboratory investigation is performed to compare the two types of in-situ test (shove and pull) using plain and frogged units, as well as lime and cement mortars, and both tests are further benchmarked using the standard laboratory couplet test. It is demonstrated that for regular (rectangular), plain units with weak mortar, the two in-situ tests produce strength measurements that are statistically equivalent, indicating that under this specific scenario the out-of-plane shear strength can be used as a proxy for the in-plane shear strength, and that the pull test could be used as an alternative to the shove test. In addition, the new pull test is shown to perform with demonstrated repeatability, requires minimal instrumentation, and is particularly relevant for design of anchorages under out-of-plane loading.

The suitability of 'design' height amplification factors (HAF) for the purpose of seismic assessment of existing non-structural unreinforced masonry (URM) components with known strength was evaluated through a numerical study. Four building typologies were included that represented pre-1940 URM construction in Australia and New Zealand. Through pushover and incremental dynamic analyses, the effects of diaphragm flexibility and nonlinear building response on floor accelerations were studied. It was found that Australia/New Zealand code procedures include significant inelastic building behaviour that reduces HAF. An interpretation was made on the applicability of the assumptions in the context of assessing non-structural URM components.

Failure of unreinforced masonry following the 2011 Christchurch earthquake demonstrated that many masonry strengthening solutions were inadequate for the peak ground accelerations that were experienced, and also that many of the failures were associated with underperformance of masonry anchors. Recent in-situ pull-out tests of anchors in vintage masonry structures has identified that in these tests, the failure is predominantly via splitting of the masonry units. This finding is in contrast to current design approaches that only consider failure via the formation of a cone or wedge, or masonry unit extraction. To further examine the potential for unit splitting prior to the failure modes identified in current design approaches, a laboratory campaign investigating masonry unit properties and anchor pull-out capacities, covering quasi-static, cyclic and impact loading of anchors and also incorporating the influence of quality of installation is reported here. The results of this campaign confirm that the unit splitting is an important failure mode, which may explain the observed anchorage underperformance. It is further observed that whilst cyclic and impact loading, as well as poor quality of installation have a detrimental effect on anchor performance, performance nonetheless exceeds published characteristic strengths. Additionally, as part of the laboratory campaign, a simple method for supporting masonry test units has been developed which has demonstrated good replication of the in-situ test results.

The rapid adoption of 3D-printing (3DP) technologies in construction, combined with an increased willingness to reduce environmental impact, has facilitated reapproaching earth materials for modern building industry. The feasibility of 3DP earth-based materials has been under investigation in recent years, with a particular focus on cob due to its favourable characteristics toward the 3DP process. Yet, there is a lack of definitive information on the construction of 3DP cob. Hence this paper investigates the structural feasibility of 3D-printed cob walls in low-rise buildings. The investigation involved experimental compression tests on 3DP cob samples to obtain key mechanical properties including the compressive strength and elastic modulus. These properties were then used as inputs for structural analyses with respect to three alternate types of 3DP cob wall patterns to evaluate their load-carrying capacity based on a limit-state design framework. Results from the analyses were implemented in modelling an idealised low-rise cob building covering a range of floor spans and wall heights. The analytical study found that 3D-printed walls have the potential to sustain gravity loads typical of residential construction. Further, since the 3DP material was shown to have similar mechanical performance to conventional (non-3DP) cob on the material scale, the 3D-printing process provides the opportunity to produce wall sections that are structurally more efficient than the solid section used in conventional cob construction. This results in lower material consumption, making 3DP cob attractive from the point of view of resource efficiency. An important outcome of the study is the demonstration of a model design technique for low-rise 3DP cob buildings that could be implemented as part of a broader optimisation procedure to satisfy structural and architectural design objectives.

In the experimental assessment of the in-plane behaviour of unreinforced masonry (URM) walls containing openings, accurate measurement of the deformations occurring in the pier and spandrel substructures is important. Eight full-scale perforated URM walls were tested under in-plane cyclic loading and constant vertical pre-compression load. To measure the deformation of the walls (pier-spandrel substructures) during testing and to capture the full-field cracking of the masonry, a two dimensional (2D) Digital Image Correlation (DIC) technique was used in parallel with traditional hard-wired instrumentation (Linear Variable Differential Transformers, commonly referred to as LVDTs for short). This paper describes the detailed procedures of using DIC in large scale masonry wall testing. Firstly, the digital images at the first peak of each displacement amplitude in both push and pull directions for one specimen were analysed using the VIC-2D software to validate the DIC results against the LVDT recorded measurements. After confirming the accuracy of the DIC measurements for the specimen, the pier-spandrel movements and the cracking analyses of all the walls were performed in order to better understand the integrity of these elements during cyclic in-plane loading.

This paper presents the seismic assessments of unreinforced masonry (URM) walls subject to out-of-plane two-way bending using examples of eight URM wall specimens which have been subject to quasistatic loading tests. The seismic assessments of the tested walls have been undertaken using simple techniques based on force, velocity and displacement procedures. More rigorous seismic evaluations involving time-history simulations have been undertaken for critical cases requiring further investigation. The hysteretic models used in the time-history analyseswere representative of the hysteretic behaviour of theURMwalls observed in the cyclictests. These models feature strength degradation behaviour and self-centering behaviour on unloadingwhich have been found to vary significantly amongst thewall specimens. Sensitivity studies have been undertaken to quantify the relative significance of the hysteretic model parameters in terms of the out-of-plane displacement demand of the walls when subject to excitations of different forms. © 2007 Taylor & Francis Group, London.

The present study was conducted to investigate the global and local in-plane response of perforated URM walls under earthquake loading, based on observations of damage from previous earthquakes. To do so, full-scale cyclic in-plane testing of URM walls with an arched opening which were designed to represent walls in heritage URM structures in Australia was performed. The study investigated the behaviour of both pier and spandrel elements within the walls. Emphasis was also given to the position of walls within a multi-storey building by varying the pre-compression loads (representing gravity loads) on the walls. The tested walls were then simulated using nonlinear finite element analyses (FEA) where simplified micro-modelling (crack-shear-crush) approaches were used to analyse the wall behaviour. Finally, the shear capacities and the failure modes of the walls obtained from the experimental tests and FE analyses were compared to the proposed New Zealand Society for Earthquake Engineering (NZSEE) predictions.

This paper presents numerical modelling of the in-plane shear behaviour of unreinforced masonry (URM) walls with a semicircular arch opening. To do so, two dimensional finite element (FE) modelling of a series of experimentally tested walls was conducted using the simplified micro-modelling approach. The models successfully captured the load-displacement behaviour and, to a large extent, the failure modes of the piers and spandrels observed in the experimentally tested walls. The exception was that the FE modelling did not show pier diagonal shear cracking which was observed in some of the tested walls. The model was then used to perform parametric studies to investigate the effect of geometric variations of the walls as well as the effect of vertical pre-compression stresses on the lateral in-plane capacity of the walls. The results obtained from the FE analyses were compared to the anticipated maximum shear strength and the predicted failure modes according to the New Zealand Society for Earthquake Engineering (NZSEE, 2017). From this study, it is shown that there is a significant effect of the wall geometry and vertical pre-compression load on the failure modes and the lateral load resistance capacity of the walls. In most of the cases investigated, the NZSEE equations for maximum shear strength and failure modes agree well with the FEM results. The arch opening was remodelled to a rectangular opening and it was found that the effective pier height for an equivalent rectangular pier adjacent to a semicircular arched opening can be taken up to the half height of the arch radius.

Investigations of damage sustained following the 2010–2011 Canterbury earthquake sequence highlighted premature failure of anchorages in previously strengthened masonry. These failures suggest that a lack of understanding surrounding anchorage design is limiting the ability to seismically retrofit masonry structures. In order to provide experimental observations for use in developing and calibrating anchorage models a series of in-situ tests have been undertaken on three masonry structures to quantify in-situ mechanical properties and corresponding anchor pull-out loads and failure modes. Importantly, the outcomes of this field testing show poor correlation with the outcomes predicted by current design standards and approaches – that is, that the failure of anchorages by splitting of the masonry units rather than cone/wedge type failure or masonry unit extraction was the predominant observation. Additionally, due to difficulties with common test procedures, interpretation of standardised tests such as the “shove” test and the bond wrench test have been difficult. Alternative material tests and statistical distributions are proposed and a new anchorage failure model is suggested.

The results of an investigation of the probability of earthquake damage to nonstructural unreinforced masonry (URM) components are presented. The components include parapets, chimneys, and out-of-plane loaded facades typical of low-rise pre-1940 construction in Australia and New Zealand. The study is based on a street survey of component geometry, in situ data on material strength, and simplified mechanical models. Uncertainties in capacity and demand were quantified based on, respectively, stochastic and deterministic approaches. The damage probabilities were compared with relevant guidelines and empirical damage data from three earthquakes. The study established a link between the qualitative damage states reported in existing guidelines and the quantitative URM component damage states. While some median damage state thresholds correlated well with the data from the guidelines, a larger dispersion value was found in the current study due to the large variations in component properties. Comparisons with empirical data suggest that the developed fragility data provide a realistic estimate of nonstructural component damage that occurred in similar buildings, with a reasonable level of conservatism. The outcome is useful in rapid assessment of the seismic risks due to nonstructural component collapse in URM precincts.

This study presents an experimental investigation of the effect of environmental exposure on the fiber-reinforced polymer (FRP) to clay brick masonry bond when the reinforcement is near-surface-mounted. Three alternate types of exposure are considered: (1) thermal loading with single or multiple thermal exposure cycles, (2) water immersion, and (3) hygrothermal cycling. The latter two treatments were used to condition the samples over a long-term period with testing undertaken after 3, 6, 15, and 24 months from initial exposure. Since previous tests on externally bonded FRP have shown that environmental conditioning can often cause failure in the adhesive, both an epoxy and cementitious adhesive are investigated. The results of the study indicate that although environmental conditioning caused some degradation in the mechanical properties of the various constituents, the strength of the FRP-to-masonry bond remained highly durable regardless of the adhesive used. (C) 2019 American Society of Civil Engineers.

This paper presents the results of an experimental study into the behavior of perforated (containing openings) unreinforced masonry (URM) walls subjected to cyclic in-plane lateral loading. Damage to perforated URM walls during previous earthquakes has revealed that the in-plane response is mainly influenced by the pier and spandrel geometry, as well as the level of axial compressive stress on the walls due to gravity loading. The study focused on masonry typologies representative of historical URM buildings in the Australian context. To investigate this behavior, eight full-scale URM walls with semicircular arched openings, double wythe thickness, and materials representing masonry construction from the mid-19th to mid-20th century were constructed for pseudostatic cyclic in-plane testing. The experimental program considered varying spandrel depths and pier widths and the imposed vertical loading on the piers was also varied to observe the lateral load capacity and the variation of pier-spandrel failure modes. The test results showed that the in-plane capacity and the failure modes were significantly affected by changes of wall geometry and the imposed vertical precompression loading. Predictions of wall strengths, in-plane stiffnesses, and failure modes according to ASCE guidelines show that the guidelines agree well with the test observations. (C) 2020 American Society of Civil Engineers.

A formulation is presented for simplified evaluation of the roof acceleration response for the purpose of assessing non-structural components in unreinforced masonry buildings with flexible diaphragms excluding torsional effects. The method is based on modal calculations that are further studied through nonlinear time-history analysis (NLTHA) of four case study buildings. The NLTHA results for a relatively small level of ground shaking was used to validate the overall ability of the simplified modal method to predict the diaphragm flexibility effects. The NLTHA results were also used to discuss the effects of the building inelastic response in the conservatism of the simplified modal technique. It was found that, in lieu of a comprehensive modal analysis, it is possible to calculate roof accelerations in symmetric low-rise buildings with flexible diaphragms using a simplified two-mode modal method. Based on this study, a predictive method is proposed for conservative estimation of peak roof accelerations in these buildings.

The use of Fiber-Reinforced Polymer (FRP) materials as Externally Bonded Reinforcement (EBR) to strengthen and/or repair existing Reinforced Concrete (RC) structures is widely documented, and various methods exist to increase the bond strength and/or ensure load-path continuity between FRP composites and the concrete substrate. The use of FRP anchors to increase the capacity of EBR systems offers a number of critical advantages compared to other existing methods. However, despite the significant amount of research previously undertaken on the topic a concise summary of the experimental performance of FRP anchors has not yet been reported. Consequently, a database consisting of five tables comprising the results from studies focused on testing isolated FRP anchors and four additional tables with results related to the use of FRP anchors in combination with FRP-EBR systems to strengthen and/or repair RC structures is presented. A number of tentative design models previously published for various failure modes are reported and reanalyzed in a critical way, and behavioral trends were identified as an effort to discern what models are ready to be used and what new further research is needed in the development of design guidelines for FRP anchors.