Ductility Of Walls Research Articles

Strength Enhancement of Interlocking Hollow Brick Masonry Walls with Low-Cost Mortar and Wire Mesh

Cement–clay Interlocking Hollow Brick Masonry (CCIHBM) walls are characterized by poor mechanical properties of bricks and mortar. Their performance is observed to be unsatisfactory under both gravity and seismic loads. There is an urgent need to develop sustainable, environmentally friendly, and low-cost strengthening materials to alter the structural behaviour of brick masonry walls in terms of strength and ductility. The results of an experimental investigation conducted on the diagonal compressive response of CCIHBM walls are presented in this study. In this experimental study, a total of six CCIHBM walls were constructed using cement–clay interlocking hollow bricks. One was tested as a control or reference wall, whereas the remaining walls were strengthened using cement mortar. In some walls, the cement mortar was also combined with the wire mesh. The research parameters included the type of Ordinary Portland Cement (OPC) (Type 1 and Type 2), thickness of cement mortar (10 mm and 20 mm), and layers of wire mesh (one and three layers). The experimental results indicate that control or unstrengthened CCIHBM walls failed in a very brittle manner at a very low ultimate load and deformation. The control CCIHBM wall, i.e., W-CON, failed at an ultimate load of 247 kN, and corresponding deflection was 1.8 mm. The strength and ductility of cement mortar and wire mesh-strengthened walls were found to be higher than the reference CCIHBM wall. For example, the ultimate load and deformation of cement-mortar-strengthened wall were found to be 143% and 233% higher than the control wall, respectively. Additionally, the ultimate failure modes of cement mortar and wire mesh strengthened were observed as ductile as compared to the brittle failure of reference wall or unstrengthened CCIHBM wall, which increased by 66% and 150% as compared with the control wall.

Experimental research on the behavior of masonry walls reinforced with dry-connected steel plate frames under axial compression

This paper conducted several experimental tests and theoretical analyses to present a comprehensive study on the behavior of dry-connected steel plate frame-reinforced brick walls under axial compression. One unreinforced brick wall, two brick walls reinforced with dry-connected steel plate frame, and one brick wall reinforced with steel strips were fabricated for axial compression tests. The experiments generally showed that steel plate frames effectively improved the structure's bearing capacity and axial stiffness and impeded its cracking. Increasing the thickness of steel plates further improved the bearing capacity but undermined the ductility of the composite wall. Besides, based on the buckling theory of steel plate and the existing calculation theory of masonry strength, this paper also proposed formulas for determining the bearing capacity of the composite wall. The calculations of formulas exhibited acceptable accuracy in comparison with the experimental results.

Seismic Behavior of Steel-Fiber-Reinforced High-Strength Concrete Shear Wall with CFST Columns: Experimental Investigation

To improve the seismic behavior of shear walls, a new composite shear wall composed of a steel-fiber-reinforced high-strength concrete (SFRHC) web and two square concrete-filled steel tube (CFST) columns, namely a steel-fiber-reinforced concrete shear wall with CFST columns, is proposed in this paper. Therefore, the main purpose of this paper is to present an experimental investigation of the seismic behavior of the SFRHC shear wall with CFST columns. Pseudo-static tests were carried out on seven composite shear walls, and the seismic performance of the shear walls was studied and quantified in terms of the aspects of energy consumption, ductility and stiffness degradation. Furthermore, the experimental results indicated that adding steel fiber can effectively restrain the crack propagation of composite shear walls and further help to improve the ductility and energy dissipation capacity of composite shear walls and delay the degradation of their lateral stiffness and force. Moreover, the seismic behavior of the SFRHC shear wall with CFST columns was obviously superior to that of the conventionally reinforced shear wall, in terms of load-bearing capacity, ductility, stiffness and energy dissipation capacity, because of the confinement effect of the CFST columns on the web. Finally, the preliminary study demonstrated that the composite shear wall has good potential to be used in regions with high seismic risk.

Experimental Study on Seismic Behavior of Composite Shear Wall with Inclined Bars

The composite shear wall is the core component of the thermal insulation integrated structure, which is a load-bearing shear wall with good thermal insulation, sound insulation, and seismic resistance. To improve the applicable height of the composite shear wall structure, a cohesive sandwich heat-insulation composite shear wall with door frame inclined tendon and diamond-shaped inclined tendon is proposed, and the quasistatic force of four 1/2-scale shear wall test specimens is carried out. Different specimens are analyzed, including failure modes, hysteresis curves, skeleton curves, stiffness degradation, ductility performance, and energy dissipation capacity. The following conclusions are drawn: the failure modes of the specimens are bending and shear failure; the ultimate strength and deformation performance of the composite wall close to the solid wall; the composite wall with the door frame inclined tendon can effectively delay the wall cracking and improve the bearing capacity and energy consumption capacity of the composite wall; the configuration of the diamond-shaped inclined tendon improves the ductility and energy dissipation capacity of the composite wall.

Seismic performance of new adobe bricks masonry: Design and experiment

At present, adobe houses with traditional characteristics are still widely used in rural areas in western China, but their seismic performance is relatively poor, and they often suffer serious damage under earthquake. To improve the seismic performance of traditional adobe buildings while retaining the characteristics of residential buildings, the mechanical properties of compressed earth blocks (CEB) were tested in this study, and the microstructure characteristics of CEB after failure were analyzed by electron microscope. On this basis, six adobe wall specimens were designed and tested by quasi-static loading to investigate the influence of core columns and different types of bricks on its seismic performance. The results show that the core column can improve the bearing capacity and shear capacity of hollow CEB, and it can also significantly increase the bearing capacity, energy dissipation capacity, and ductility of CEB wall. In general, the adobe wall with core columns shows excellent seismic performance, which can provide a new choice for improving the seismic performance of the adobe house.

Experimental study on shear performance of improved high-performance polymer cement mortar–glass fiber reinforced plastic reinforced masonry wall

The improved high-performance polymer cement mortar (PCM) and glass fiber reinforced plastic (GFRP) system reinforcement was used in the research to strengthen and repair the masonry structure, so as to improve its bond stress, anchoring force, and integral performance without changing the original structure and further study the shear performance of masonry structure strengthened by the combination of the two. The optimum ratio of improved high-performance PCM was determined by analyzing the bend-press ratio of PCM test block. Improved high-performance PCM and GFRP were combined to strengthen the damaged masonry wall, and a five-piece masonry wall composed of “improved high-performance PCM+ with or without GFRP+ different original wall failure modes before reinforcement” was designed. Through diagonal loading shear test, the shear strength, vertical displacement, horizontal relative displacement, and failure models of masonry walls were obtained, and the effects of five different reinforcement methods and different materials on shear strength, stiffness, ductility, and failure modes of masonry walls were studied. The results show that compared with the unreinforced original wall, the shear strength of the masonry wall reinforced with the improved O4PCM is 43.5% higher, and its stiffness is also greatly improved, but the failure mode is still brittle failure; the shear strength of masonry walls strengthened by O4PCM and GFRP is 6.5% higher than that of masonry walls strengthened by O4PCM alone, and the stiffness is also increased. Its failure mode changes from brittle failure to ductile failure; with a failure mode of ductile failure, the shear strength of masonry walls strengthened by P4PCM and GFRP and that strengthened by P6PCM and GFRP are 4.8% and 12.7% higher than that strengthened by O4PCM and GFRP, respectively, and the stiffness is also increased compared with that strengthened by O4PCM and GFRP. After experimental comparison, it is the best scheme to strengthen masonry wall with improved P6PCM and GFRP.

Compressive behaviour and environmental evaluation of sludge-derived masonry walls

The Paris Agreement, with its target of net-zero emissions by 2050, has forced the concrete industry to reduce its energy consumption and carbon emissions. Therefore, the development of green concrete with a lower environmental impact is urgently required. In this case study, alum sludge was used as both sand and cement replacement in concrete blocks, and the compressive behaviour of concrete blocks and constructed masonry walls was first investigated. For cement replacement, the strength of blocks decreased with increasing alum sludge ash (ASA) content when the cement replacement ratio was higher than 10% by weight. These results were attributed to the fact that the filler effect and pozzolanic reaction of ASA compensated for the cement dilution effect at a moderate replacement ratio. However, the cement dilution effect dominated the mechanism with further ASA addition. For sand replacement, 10% oven-dried alum sludge addition degraded the mechanical performance of blocks significantly due to high organic content, which might hinder cement hydration. The compression behaviour of masonry walls was also influenced by alum sludge, and the testing results showed that the sludge addition increased ductility of the masonry wall but decreased the strength insignificantly. Therefore, the sludge-derived blocks were suitable for masonry application. Furthermore, a life cycle assessment model was developed based on the designed sludge-derived cement supply chain in South Australia. The obtained results indicate that the annual reduced greenhouse gas emissions were around 1,3339,549 tons, which equaled to the amount of greenhouse gas released from 28,898 passenger vehicles driven for a year.

In-plane and out-of-plane structural performance of fully grouted reinforced masonry walls with varying reinforcement ratio – A numerical study

Most international masonry design standards include the contribution of reinforcements to enhance the capacity of reinforced masonry walls subject to seismic loading. As masonry is brittle, it can potentially fail before the reinforcing bars yield, especially in closely spaced reinforced masonry walls. The assumption that these bars yield at the ultimate load could, therefore, result in an unrealistic over-prediction of the flexural and shear capacities of the walls. This paper presents a detailed investigation of several fully grouted reinforced masonry (FGRM) walls subject to in-plane and out-of-plane loading that is independent of each other. The analyses include the level of pre-compression and a wide range of reinforcement ratios. The assessment has been carried out through an explicit finite element (FE) model. Validation of the FE model is briefly presented and the structural performance, i.e., load capacity, lateral drift index, displacement ductility and stiffness of the FGRM walls are discussed in detail. The influence of reinforcement ratio on the yielding of reinforcing bars in the FGRM walls under in-plane and out-of-plane loading is also shown. It is found that the increase in reinforcement ratio beyond a critical limit degraded the structural performance of the FGRM walls and a suitable reinforcement ratio range is proposed.

Experimental study on seismic behavior of novel AAC prefabricated panel walls

To attain sustainability and resilience goals in construction, there is a great need for lightweight and high-strength panel elements with simple and rapid construction, and enhanced heat insulation and sound attenuation. Accordingly, this study explores the seismic performance of novel prefabricated autoclaved aerated concrete (AAC) panel-walls that satisfy the above sustainability criteria. The corresponding failure process, load versus displacement, hysteresis behavior, stiffness skeleton, degradation curve, and ductility coefficient of the AAC panel-wall specimens were analyzed. Different design parameters including the size of the splicing panels, reinforcement, and constructional column settings were investigated and compared to the behavior of benchmark block walls. The experimental findings indicate that: (i) compared with the benchmark block walls, the AAC panel-walls had higher seismic shear capacity; (ii) the size of splicing panels did not affect the stress distribution, failure pattern, seismic shear capacity, and ductility of the panel-wall member; (iii) the in-panel reinforcement can make the stress distribution in the wall more uniform, increase its seismic shear capacity, reduce the rate of stiffness degradation, and enhance the wall ductility; (iv) and using constructional columns can enhance the ultimate load-bearing capacity of the wall. The construction of the panel-wall is convenient. Its seismic and shear performance are suitable for practical engineering applications.

Modelling of mid-rise concrete shear walls reinforced with superelastic shape memory alloys: Nonlinear analysis

The response of hybrid Shape Memory Alloy (SMA)-steel reinforced concrete shear walls containing Nickel-Titanium superelastic SMA as alternative reinforcement in the plastic hinge region was investigated using nonlinear finite element modelling. The hybrid wall system promotes self-centering and significant reduction of permanent deformations. Two types of conventional steel-reinforced concrete shear walls were designed for a prototype 10-storey office building according to the current Canadian concrete design standard, assuming two distinct seismic design scenarios. A moderately ductile shear wall was designed for a moderate seismic zone in eastern Canada, whereas a ductile shear wall was designed for a high seismic zone in western Canada. Equivalent, hybrid SMA-steel reinforced concrete shear walls were defined following the design of the two conventional shear walls, in terms of geometry and reinforcement layout. Full-scale, two-dimensional finite element models were developed to assess the pushover and hysteretic responses of the walls. Similarities in wall cross-section and yield force capacity of the steel and SMA reinforcement permitted a comparison between the walls, including strength, stiffness, self-centering, and energy dissipation capacities. The results indicate similar lateral strength and displacement capacities, and superior restoring capacity of the SMA-reinforced walls in comparison to the steel-reinforced walls. Furthermore, a preliminary study was conducted to investigate the effect of the SMA-bar length in the ductile wall due to concentration of damage near the base of the wall. Lengths corresponding to approximately 50% and 20% of the original SMA length were considered. Based on the analyses, a satisfactory response could be achieved with shorter SMA reinforcing bars, which reduces the quantity of SMA reinforcement without significant loss in self-centering capacity.

Design recommendations to prevent global out-of-plane instability of rectangular reinforced concrete ductile walls

Observations of out-of-plane (OOP) instability in the 2010 Chile earthquake and in the 2011 Christchurch earthquake resulted in concerns about the current design provisions of structural walls. This mode of failure was previously observed in the experimental response of some wall specimens subjected to in-plane loading. Therefore, the postulations proposed for prediction of the limit states corresponding to OOP instability of rectangular walls are generally based on stability analysis under in-plane loading only. These approaches address stability of a cracked wall section when subjected to compression, thereby considering the level of residual strain developed in the reinforcement as the parameter that prevents timely crack closure of the wall section and induces stability failure. The New Zealand code requirements addressing the OOP instability of structural walls are based on the assumptions used in the literature and the analytical methods proposed for mathematical determination of the critical strain values. In this study, a parametric study is conducted using a numerical model capable of simulating OOP instability of rectangular walls to evaluate sensitivity of the OOP response of rectangular walls to variation of different parameters identified to be governing this failure mechanism. The effects of wall slenderness (unsupported height-to-thickness) ratio, longitudinal reinforcement ratio of the boundary regions and length on the OOP response of walls are evaluated. A clear trend was observed regarding the influence of these parameters on the initiation of OOP displacement, based on which simple equations are proposed for prediction of OOP instability in rectangular walls.

More efficient design of CFS strap-braced frames under vertical and seismic loading

Strap-braced stud walls are one of the primary lateral-force resisting systems for conventional cold-formed steel (CFS) buildings. While CFS wall-panels in general exhibit a satisfactory seismic performance, previous studies showed that they may experience a premature brittle failure in the presence of vertical loading. However, current design codes do not make any provisions for calculating the lateral load capacity and ductility of strap-braced stud wall frames under vertical loading. This study aims to develop, for the first time, a practical design methodology for seismic design of CFS strap-braced stud wall frames under such conditions. To this end, a comprehensive parametric study was carried out using experimentally validated detailed numerical models in ABAQUS, accounting for material nonlinearities, initial geometric imperfections, and secondary moments due to P-Δ effects. Parameters of the investigations were the strap thickness and the intensity of the vertical loading. Design formulae were derived, and a preliminary design methodology was proposed for predicting the lateral load capacity and ductility of single strap-braced stud walls under a range of vertical loading ratios. The efficiency of the proposed method compared to Eurocode 8 design was then demonstrated for a 6-storey CFS frame, which highlighted the importance of considering the effects of vertical loads in the seismic design of these systems. It was demonstrated that ignoring those factors can lead to a brittle lateral response even if all other code requirements are satisfied, while the proposed design methodology was shown to be efficient to reach the target lateral load and ductility capacities.

Damage indices and fragility assessment of coupled low-yield-point steel plate shear walls

A new multiple lateral force resisting system consisting of coupled low-yield-point steel plate shear walls (C-LSPSW) was proposed as a promising alternative to improve the ductility, energy-dissipation capacity, architectural flexibility, and economic efficiency of steel plate shear walls (SPSWs). To investigate its seismic performance and damage behavior, eight C-LSPSW specimens with different configuration parameters, including two different stories and four different section sizes of coupling beams (CBs), were designed and the corresponding numerical models were established by verified modeling approach. The incremental dynamic analyses (IDA) were conducted on these specimens, and the multi-stage damage indices of the C-LSPSW system were proposed based on different damage states. The design suggestions for the C-LSPSW system were proposed in terms of the fragility analyses. The analytical results demonstrated that the ductile damage mechanism with the sequence of “infill plates to CBs or horizontal boundary elements (HBEs) to vertical boundary elements (VBEs)" was achieved more easily in the C-LSPSW system, which gave full play to the superiority of multiple seismic defense lines. Under high seismic excitation, the failure probability of the C-LSPSW system was smaller than that of the LSPSW system, and the coupling superiority was more obvious in higher structures. The optimum performance of C-LSPSW system was observed when the plastic moment capacity ratio of CBs to HBEs (MpCB/MpHBE) was 2.0. As a result, an optimal solution with MpCB/MpHBE = 2.0 was suggested as a good compromise between the architectural requirements, material efficiency, and seismic performance.

Behaviour of slender concrete shear walls with high-strength reinforcement under reverse cyclic loading

Research on seismic behaviour of shear walls with high-strength steel is limited. A combined experimental and analytical investigation was conducted to assess seismic behaviour of flexure-dominant shear walls. A large-scale concrete shear wall with Grade 690 MPa (ASTM A1035) reinforcement and 84 MPa concrete was tested under simulated seismic loading. The wall represented a 6-story building shear wall with 4.53 m height and 1.45 m length. It sustained a lateral drift of 1.8% prior to developing failure due to the rupturing of longitudinal reinforcement. This is 35% less than the drift capacity of a companion wall reinforced with 400 MPa reinforcement tested earlier. VecTor2 software was used to conduct an analytical parametric study to expand the experimental findings. The results indicate that the reinforcement grade has a significant impact on strength, ductility, and hysteretic behaviour of shear walls.

Evaluation of current Eurocode 8 provisions on R/C ductile wall design

In this study, the applicability and conservativeness of current Eurocode 8 (2004) provisions for the design of ductile reinforced concrete (R/C) shear walls are evaluated. Apart from adequate strength supply, a successful design also requires that the provided section curvature ductility should satisfy the respective demand. The Code, striving to maintain a balance between ease of application and accuracy, provides practical directives to facilitate the required ductility supply. However, at the end of the design there is no tangible verification whether the provided ductility satisfies the requirement. To provide insight regarding the applicability of these Code provisions, an extensive series of rectangular wall cases is analyzed, and various design approaches adopted by engineering practice are evaluated. Moment-curvature analysis including confinement effects is performed on all wall configurations for verification purposes. It is found that simplified Code approaches cannot always guarantee an acceptable design; in this regard, a few alternatives are presented, favoring conservativeness and accelerating the design workflow. The paper concludes with an evaluation of the current design practice, under the light of the upcoming Code revision.

Molecular dynamics simulations of ultrathin PMMA films

The mechanical properties of an ultrathin film made from a thermoplastic differ from the bulk due to the presence of the free surface. Here, molecular dynamics simulations are used to explore the thickness dependence of uniaxial and equi-biaxial tensile responses of polymethyl methacrylate (PMMA) films. The sensitivity of deformation response to temperature, molecular weight and the degree of side-branching is determined. We find that the tensile failure strain decreases with decreasing film thickness, temperature, and with decreasing molecular weight. The degree of side-branching plays a secondary role in dictating the tensile response. Failure is by the initiation of voids at the free surface, followed by the expansion of the voids in the thickness direction. Recent solid−state nanofoaming experiments and models suggest that the attainable porosity of nanofoams is less than that of macro−scale foams due to the reduced ductility of the cell walls of the nanofoam. Our results provide a physical explanation for this observation.

Reinforced masonry shear wall blast response limits for ASCE 59 and CSA S850

The current blast response limits for reinforced masonry (RM) walls in North American blast standards are based on parameters that neither account for the wall ductility capacities nor the influence of different design configurations on the wall damage tolerance levels. Specifically, ASCE (2011) and CSA (2012) currently assign a support chord rotation limit for each damage state (i.e., Superficial, Moderate, Heavy, and Hazardous) regardless of the different ductility capacities that structural components may possess when different design configurations are adopted. However, recent relevant studies demonstrated that wall configurations and their different design parameters significantly influence the out-of-plane performance of RM walls. For example, RM shear walls with boundary elements are considered a promising blast-resisting system due to their enhanced out-of-plane characteristics (e.g., strength and ductility) compared to those with typical cross-sections (i.e., rectangular). Nonetheless, the aforementioned standards do not assign separate design requirements or response limits for this new system due to the limited number of relevant studies available when such standards were being developed. To address this knowledge gap, the current study evaluates the blast behavior of such walls with different configurations and subsequently proposes new related blast response limits for ASCE 59 and CSA S850. An OpenSees model was developed and then validated through the results of several previous test programs under quasi-static and blast loads. Subsequently, the new response limits were generated using the model and compared to those currently available (i.e., ASCE 59–11/CSA S850-12) using pressure-impulse diagrams. Finally, the blast response of several RM walls with different configurations was evaluated when such walls were subjected to different blast demands. The results highlight the blast-resistance enhancements that boundary elements can provide to RM shear walls at different damage states and the need to develop category-specific blast response limit within blast design standards.

Experimental study on seismic performance of strengthening masonry wall using hybrid fiber-reinforced reactive powder concrete

An experimental study was conducted to investigate the seismic performance of masonry walls strengthened using hybrid fiber-reinforced reactive powder concrete (HyFRRPC) as a coating. The proposed reinforcement technique was employed to improve the overall strength and structural integrity of the confined masonry wall. In order to guarantee the composite action between the masonry substrate and the coating material, material tests were conducted to achieve an optimal mixture for the HyFRRPC. Then, six full-scaled confined masonry specimens strengthened by HyFRRPCs with varied strengthening configurations were tested under in-plane quasi-static horizontal loading. The test and analysis results indicated that the proposed HyFRRPC-strengthening technique can effectively improve the lateral carrying capacity, displacement ductility, and energy dissipation capacity of masonry walls, and provide an optimal reinforcement. Finally, a simplified analytical model was also proposed for practical application.

Experimental investigation on the in-plane seismic performance of damaged masonry walls repaired with grout-injected ferrocement overlay

• The performance of damaged masonry wall with and without reinforcement was discussed. • The strengthening technique is based on the use of ferrocement overlay. • The use of the strengthening technique requires low cost and low-tech workmanship. • The seismic response of damaged wall is significantly improved by GFOR. This experimental study compares two scaled unreinforced masonry (URM) walls before and after being repaired by grout-injected ferrocement overlay reinforcement (GFOR), with the aim of investigating the effectiveness of an alternative ferrocement overlay technique. In the experiment, loading was performed on a multistory opening URM wall to induce damages, and the reinforced wall (defined as FRM) was retested using the same procedure. A comparative analysis of the seismic performances of the two walls in terms of failure modes, bearing capacity, hysteresis curve, energy dissipation capacity, and deformation behaviors was performed. The experimental results indicated the following. (i) The application of GFOR on the damaged URM wall altered its diagonal shear failure into the flexural-dominant mode. (ii) The ultimate resistance and residual strength of FRM increased by 6% and 13%, respectively, compared with those of URM. (iii) The ultimate and residual deformations of FRM increased by 110% and 60%, respectively, compared with those of the URM. (iv) The ductility of the overall walls improved from 2.48 to 2.72. This study verified the reasonability and effectiveness of the application of GFOR to damaged masonry structures.

An Investigation of Performance of Masonry Wall Reinforced with Timber lumbers

The current article seeks to investigate the behavior of masonry wall reinforced with timber lumbers and effect of timbers on increasing the shear strength and ductility of wall. To determine the mechanical properties of the timbers, two experiments according to ASTM D143 were performed. All of the mechanical properties required for timber simulation were determined via tensile and compressive tests, and using parametric equations. The behavior of the timbers under tensile force was brittle, and under pressure was semi-ductile. Hill yield criterion was utilized for timber behavior modelling. Predictably, the location of the plastic strain formation in the tensile and compressive specimen was consistent with the location of the fracture in the experimental specimens. In the next parts of the research, the obtained parameters were used to model the mechanical behavior of the timbers. Macro and meso approaches were used for the numerical modeling of the masonry wall. The Willam–Warnke yield criterion was used on the macro scale, and the cohesive-frictional interface constitutive model was utilized on the meso scale. Both numerical models were in good agreement with the laboratory results. However, due to the gap and sliding of the masonry wall in the numerical model, the Meso scale was used in the research. The masonry wall was retrofitted and strengthened by three different patterns of timber placement. An examination of the analysis results showed that by placing the timbers, the wall cracking pattern tends to change, and the ductility and shear capacity of the wall considerably enhances.