In-plane Cyclic Loading Research Articles

Experimental Study on the Seismic Behavior of a Modified Adobe-Brick-Masonry Composite Wall with a Wooden-Construction Center Column

Damage to adobe constructions might occur due to a long wall and a lack of effective restraint in the middle of the wall, causing it to collapse under an earthquake. Aiming at these problems, a technology for improving the seismic performance of a modified adobe-brick-masonry composite wall with a wooden-construction center column is proposed. It uses modified mud, a wooden center column, steel-wire mesh, and nylon ropes to reinforce the wall. On this basis, four specimens of composite wall and one specimen of modified adobe wall were subjected to proposed quasistatic, cyclic in-plane loading tests to study their failure modes and seismic performance indicators. The results show that the failure modes of all walls were shear failure. The difference is that the modified adobe wall had horizontal cracks in the middle, whereas the composite walls were largely intact. Moreover, the composite walls relied on the modified mud to improve the seismic bearing capacity of each wall. They relied on the center column and the tie materials to form a second line of defense that would increase the wall ductility and collapse residual area. As a result, the phenomenon that caused wall damage and stiffness degradation was lessened.

Cold-formed steel centre-sheathed (mid-ply) shear walls of intermediate resistance

To enter the market for mid-rise buildings, cold-formed steel (CFS) framed steel sheathed shear walls need to resist seismic forces in excess of 60 kN/m. An innovative configuration in which the sheathing is placed at the mid-line of the framing was developed through a laboratory test program. These centre-sheathed shear walls provided a substantial increase in shear resistance, over four times that currently found in the AISI S400 Standard, as well as an increase in ductility. Nine additional shear walls subjected to asymmetric in-plane cyclic loading were investigated in this study. These walls reached intermediate shear resistances between 46.7 kN/m and 91.0 kN/m and could maintain this resistance beyond drift ratios of 4%. In addition, three tests were carried out on the bare frame to identify the shear capacity provided by the specially detailed perimeter frame. An updated equation-based model, including the frame effect, was proposed for predicting the ultimate shear strengths of these shear walls.

FEM analysis of the effect of various brick bond patterns on masonry walls under in-plane cyclic loading

FEM analysis of the effect of various brick bond patterns on masonry walls under in-plane cyclic loading

Behaviour of reinforced mortarless interlocking brick wall under cyclic loading

Interlocking brick masonry has gained much attention due to its high construction efficiency and low labour skill requirement. Most designs of interlocking bricks only use interlocking keys to provide alignment for easy construction, and most previous studies of interlocking masonry structures concentrate on their static loading capacities. This study examines the behaviour of reinforced mortarless interlocking brick walls under cyclic loading. Interlocking brick wall made of a specific type of interlocking bricks with large keys that provide not only alignment in construction but also shear resistance is constructed and tested under in-plane cyclic loading. A detailed numerical model is generated and validated with the testing data, which is then used to assist the analysis of wall responses. The damage mode, hysteresis response and energy dissipation characteristics are analysed. The test results are compared with conventional masonry wall from literature to demonstrate the superior performance of interlocking masonry wall in resisting seismic loading and dissipating seismic energy. The influences of axial precompression and shear span-to-length ratio are investigated via numerical modelling.

Experimental study on the in-plane response of cast-in-situ reinforced concrete sandwich walls under combined vertical and horizontal load

Cast-in-situ Reinforced Concrete Sandwich Panel (cRCSP) technology represents a viable and increasingly popular solution for the construction sector to face recent crucial challenges, such as great housing demand or environmental sustainability. Recently, cRCSP-based buildings are being widely used also in earthquake-prone countries, like Italy. Nevertheless, so far, the available studies in the literature studies focused on the seismic response of this structural typology are not-exhaustive and, besides, relevant structural technical codes do not provide specific design rules. The present study deals with an experimental campaign carried out on four full-scale cRCSP walls subjected to increasing in-plane cyclic lateral loading. Two wall configurations have been considered different for shape and openings: the first has no openings and a squat profile; the second has a central door-type opening and a square profile. Two levels of uniformly distributed vertical load have been applied and kept constant during the test. Materials, specimens, and test set-up are described. The main experimental outcomes in terms of recorded force-displacement curves and observed damage states are discussed in detail. In particular, different failure modes and seismic performances have been observed.

Thermo-mechanical characterization and hysteretic behavior identification of innovative plastic joint for masonry infills in reinforced concrete buildings

Modern approaches in buildings design strive to fulfill multiple performance requirements simultaneously. Accordingly, as far as buildings in earthquake-prone areas are concerned, damage limitation under seismic loads must be ensured while paying attention on the issues related to the environmental sustainability of the construction, ranging from its ecological footprint to the thermal efficiency. Masonry infills in framed reinforced concrete buildings are especially important in this context. In fact, they are vulnerable to earthquakes and greatly impact on the environmental sustainability of the building because they employ a significant amount of construction materials and influence its energy consumption throughout the lifetime. In light of this, the main novelty of the present work is concerned with a new deformable joint for masonry infills in framed reinforced concrete buildings. A detailed description of such innovative system for masonry infills is provided, together with numerical and experimental investigations about its mechanical and thermal behavior. The proposed joint is made of recycled plastic material, namely Regenerated Polypropylene Homopolymer. Geometry and manufacturing process of the proposed joint are initially described. Then, stress–strain relationships for the plastic material are obtained from uniaxial tensile tests at different temperatures. An assembly of fired hollow clay bricks and plastic joints is also tested under in-plane cyclic load, and a phenomenological model is thus proposed to simulate the experimental hysteretic behavior. Finally, experimental tests and finite element-based numerical simulations are performed to investigate the thermal performance of masonry infills with plastic joints.

Behaviour of double-corrugated steel plates under cyclic in-plane shear loading: An experimental study

Double-corrugated plate shear wall (DCPSW) is a new member developed based on the single-corrugated plate shear wall (CPSW). Due to its improved stability and shear resistance, it has good application potential in buildings subjected to large shear loads. Up to now, the reported experimental data of DCPSWs under cyclic loading are limited and the shear behaviour of double-corrugated steel plates in DCPSWs is needed to be further understood. This paper presents an experimental study on the double-corrugated steel plate under cyclic in-plane shear loading. Ten specimens were tested and the varied parameters included the height of corrugation, the width of subpanels in corrugation, the spacing of connecting bolts and the number of bolt columns at each valley region. The experimental results in terms of failure modes, load versus deformation hysteretic curves, skeleton curves, energy dissipation and stiffness degradation were discussed. By analysing the effects of important parameters, the mechanism of the double-corrugated steel plate under pure shear loads was revealed. It is found that the specimens failed with shear buckling which behaved as either global buckling or local buckling. Due to the combination effect, the shear resistance of the double-corrugated plate was higher than that of the single-corrugated plate with the same steel volume. Increasing the corrugation height is beneficial to improving the shear buckling load and maintaining the energy dissipation capacity. It is suggested that the ratio of corrugation height to thickness is higher than 15 in the design of the double-corrugated plate.

In-plane cyclic response of unreinforced masonry walls retrofitted with ferrocement

Unreinforced masonries are weak against seismic loads which necessitates their retrofitting. Ferrocement is widely used as it is cheaper than alternative methods of retrofitting. Some crucial parameters can significantly affect the performance of such retrofitted structures under cyclic loading conditions, such as: aspect ratio, difference of wire mesh arrangements & pattern of retrofitting. To quantify the impact of these parameters, this study has implemented two variations of each parameter. This study conducts experimental investigations of the ferrocement retrofitted unreinforced masonry walls (URM) and evaluation of their properties such as energy dissipation, stiffness degradation, hysteretic damping, ductility, and load deformation responses. Results show notable increase in strength after ferrocement retrofitting of URM walls. Retrofitting of URM walls with inexpensive material such as ferrocement is gaining popularity, our research is guided towards finding the in-plane cyclic load characteristics of such method of retrofitting. Sample walls were prepared in two categories: (1) Long walls (aspect ratio 0.57) and (2) Short walls (aspect ratio 1). A total of ten clay masonry walls (five for each category) were constructed with reinforced concrete base slab. The first variable parameter for the tests was ferrocement coating difference. Some sample walls were retrofitted completely even the base slab & wall panel connection point while on some walls the ferrocement lamination was only applied on the wall panels. Steel wire mesh’s opening size is another crucial variable test parameter. Two different wire mesh opening sizes: (1) 3.2 × 3.6 mm and (2) 8.5 × 8.5 mm were used on the walls. One control specimen with no retrofitting for both short and long walls were prepared for test comparison purpose. Laterally reversed cyclic loads and vertical loads both were applied to the sample walls during tests. Improvements in hysteretic damping, stiffness, energy dissipation and ductility were scrutinized in particular. Finally, a comparison was drawn between the test findings and allowable load provisions prescribed in the Bangladesh National Building Code (BNBC) 1993.

Seismic performance evaluation of non-structural light-gauge-steel frame drywall partition subjected to in-plane cyclic loading

A light-gauge-steel (LGS) drywall partition is an interior non-structural wall system widely used for frame buildings across the globe. In Japan, this system features a sliding track-stud connection of the base frame. An experiment was conducted to investigate the in-plane seismic performance of a typical light-gauge-steel (LGS) wall constructed in accordance with Japanese practice. Fifteen light-gauge-steel (LGS) walls were subjected to in-plane cyclic loading, and the results showed that the degree of damage was related to the envelope curves of the strength-story drift ratio relationship of light-gauge-steel (LGS) specimens. The characteristic points of the envelope curve were defined based on the test results to generate the performance level of the light-gauge-steel (LGS) wall. By evaluating these characteristic points, equations for strength, stiffness, and story drift ratio were established. The prediction results from the equations of drift ratio were found to be within the safe margin. Subsequently, the equations were adopted to define the damage limit states based on damage observations during the test.

Experimental assessment of in-plane behavior of traditional Tibetan three-leaf walls

Multi-leaf masonry is a technique that can be dated back many centuries, but limited reports can be found on the seismic behaviors of three-leaf walls (TLWs). This study intended to understand better the seismic capacity of traditional Tibetan three-leaf walls (TTTLWs) constructed with stones and mud mortar by an in-plane cyclic shear loading test. A series of test results, including failure modes, hysteretic behavior, ductility, stiffness degradation, energy dissipation, and in-plane and out-of-plane bulge of tested walls were analyzed and discussed. And the experimental values of the shear strength and shear modulus were compared with the predicted values given by prediction models available in literature. Three types of failure modes were found on the wall specimens in this test: sliding of mortar joints, cracking of block stone at wall toe, and separation between external and inner leaves. The TTTLWs may be concluded to have a low shear strength of 0.118–0.162 MPa and medium shear modulus of 99–147 MPa compared with the published data of multi-leaf stone masonry. The shear strength of TTTLWs is controlled by the flexural failure, and can be predicted by the formulas recommended by ASCE.

In-plane cyclic testing of full-scale reinforced concrete frames with innovative isolated infill walls strengthened by highly ductile concrete

Conventional infilled frames exhibit weak seismic performance in high-intensity zones owing to the strong infill-frame interaction and vulnerability of the infill masonry. In this study, an innovative infill frame system with isolated infill walls retrofitted with highly ductile concrete (HDC) layers is proposed with the aim of minimizing the infill–column interaction and improving the lateral strength and deformation of masonry-infilled frames. Four full-scale specimens, including one bare frame, one conventional infilled frame, one conventional infilled frame retrofitted with HDC layers, and one isolated infilled frame retrofitted with an HDC layer, were tested under in-plane cyclic loading. The results indicated that the proposed isolated infill solution could effectively minimize the interaction between the isolated infill and columns. The observed damage on the isolated infill wall was minimal, whereas the damage to the columns was nearly identical to that of the bare frame. The isolated infill frame exhibited a higher lateral strength, deformation, and energy dissipation than the conventional infilled frame. Additionally, the proposed analytical model is highly consistent with the experimental results and can be used in design-oriented equations for innovative isolated infill frames.

Experimental and numerical investigation on seismic performance of semi-precast concrete sandwich shear wall

This study investigated the seismic performance of an innovative semi-precast concrete sandwich shear wall (SCSSW) system. The system consists of two precast reinforced concrete (RC) wythes, a core cast-in-place RC wythe, a core thermal insulation layer, the fiber reinforced polymer connectors and the steel trusses. A total of three RC shear wall specimens were fabricated and tested under in-plane cyclic load. They consists of one conventional cast-in-place RC shear wall, one structural wythe of SCSSW (i.e., the assemble of a precast and a cast-in-place RC wythe), and one typical SCSSW. The failure mode, hysteretic curve, ductility and energy dissipation of the three specimens were studied and compared. Furthermore, numerical simulation based on multi-layer shell element was conducted to reproduce the test, and parametric analysis was conducted to facilitate a better understanding on the SCSSW. It was concluded that the SCSSW presented a ductile failure behavior; the seismic performance of the SCSSW including hysteretic curves, skeleton curves, stiffness degradation and the energy dissipation was similar to that of the cast-in-place RC shear wall, while the ductility of the SCSSW was slightly lower; and the facade precast RC wythe contributed few effect on the seismic performance of the SCSSW.

In-plane behavior of Chuan-Dou style wooden frames with infill under cyclic loading

Chuan-Dou style wooden frames (CDWFs) with different infill are used widely for residential buildings in Southwest China due to their cost-effectiveness and ease of construction. Four full-scale samples of CDWF were laboratory tested to study the contribution of different infills on its seismic behavior. They are two bare wooden frames, a frame with wooden panel infills and a frame with brick masonry infills. One bare wooden frame was subjected to monotonic load to determine the reference displacement for the in-plane Cyclic loading test in the other frame samples. The damage characteristics, ultimate lateral load carrying capacity, hysteretic behavior, stiffness degradation, strength degradation and energy dissipation were investigated. Test results indicated that the CDWF has exceptional ductility to lateral movement and good energy dissipation capacity. Both the wooden panel infill and brick masonry infill increase the lateral load resistance, lateral stiffness and energy dissipation of the CDWF system. The contribution of masonry infills to the improvement of lateral resistance capacity of wooden frames is much greater than that of wooden panel infills.

Cyclic in-plane behavior of unreinforced and confined masonry walls retrofitted by shotcrete: Experimental investigation

This study aimed to investigate the efficiency of shotcrete retrofitting method for seismic rehabilitation of conventional unreinforced and confined masonry walls. In this regard, six large-scale masonry walls have been built using fired clay bricks and sand-cement mortar. The specimens were listed as unreinforced and confined masonry walls with vertical concrete ties before and after retrofitting using shotcrete overlay. Moreover, a relatively new approach was adopted for seismic retrofitting of unreinforced masonry (URM) walls as an alternative to vertical concrete ties. Correspondingly, a series of material tests were carried out to obtain the mechanical properties of the masonry, in particular the compression test on masonry prisms, shear triplet, and diagonal compression tests. The masonry walls were tested under simultaneous gravity and reversed cyclic in-plane loading. The dominant failure mode of the URM wall was rocking, while in the case of shotcrete-retrofitted specimens, the failure mechanism was predominantly bed-joint sliding. Besides, the confined masonry walls with vertical ties failed mainly due to diagonal cracking. Evaluation of the cyclic performance of the specimens showed that vertical concrete ties significantly increased the ultimate lateral resistance and the cyclic dissipated energy, though a reduction in the ductility capacity was identified. The specimens retrofitted by shotcrete exhibited a significant enhancement in the lateral strength and a more gradual strength deterioration in the post-peak behavior, even though the shotcrete reinforcing bars were neither anchored to the foundation nor to the concrete ties. Furthermore, the shotcrete-retrofitted specimens exhibited maximum dissipated energy and minimum stiffness degradation among the specimens.

Dynamic Performance Analysis by Laboratory Tests of a Sustainable Prefabricated Composite Structural Wall System

In recent decades, steel frames infilled with precast load-bearing walls have been successfully employed as lateral load-resisting structural systems in high-rise buildings. This is due to their structural efficiency as outer and major inner facades and to the higher construction speed of the building. This paper presents a detailed experimental investigation of a sustainable, prefabricated, composite structural wall system, using a representative test model named the Precast Concrete Steel Panel-Infilled Steel Frame (PCSP-ISF) in full-scale dimensions and subjected to in-plane cyclic loading. A series of experiments was conducted on critical structural specimens, including three-point bending, concentric axial compression, and diagonal compression, together with additional cycling loading tests on steel connection joint specimens, with the aim of validating the reliability and the structural response of the connections. The resulting test data and the observed failure mechanisms are discussed carefully to optimise the sustainable structural performance of the system. A theoretical approach for the evaluation of the shear capacity of the total frame system is also discussed to expand the experimental results for several numerical and experimental research cases. The failure mechanism of this module was formed by a combination of developed plastic hinges on the steel joints and diagonal cracks on the concrete panel. The obtained hysteretic behavior of the system at a parameter with major impact is mainly analysed and discussed. The outcomes indicate a satisfactory and sustainable seismic performance of the PCSP-ISF model, indicating that it can be a very promising lateral load-resisting system for earthquake-prone regions.

Feasibility experiments of seismic concrete block walls without joint mortar

The authors developed two types of block systems consisting only of main block and key block without joint mortar in consideration of seismic performance and workability. Two types of block systems have different key block shapes: One is the peanuts shape and the other is the dumbbell shape. In this study, the proposed two types of block walls as well as a typical block wall were experimentally investigated to evaluate the seismic performance. In the tests, full-scale, single-story specimens were tested under static cyclic in-plane loading, and failure patterns and cracks were carefully observed. In this paper, the loading bearing capacity, energy dissipation capacity and reuse ratio of block walls are discussed in detail. As a result, the deformability, energy absorption capacity and reuse ratio of the proposed block systems were considerably higher than those of typical block system.

Seismic performance of the ancient pagoda wall strengthened with GFRP bars embedded in the horizontal mortar joint under in-plane cyclic loading

The low strength and bonding of the mortar joints of the ancient pagoda wall result in the vulnerability to earthquake. To protect ancient pagodas under earthquakes, the seismic performances of the ancient pagoda wall strengthened with glass fiber reinforced plastic (GFRP) bars embedded in the horizontal mortar joint were studied. Six half-scale ancient pagoda wall specimens with semicircular arched openings, including two undamaged strengthened specimens, one severely damaged strengthened specimen, and three un-strengthened specimens, were tested under in-plane cyclic loading. The results indicated that the seismic performances of the strengthened specimens were effectively improved. Specifically, GFRP bars can effectively inhibit the generation of stepped cracks, and the failure modes of the strengthened specimens were changed from brittle shear failure to ductile shear failure. The shear bearing capacity of the strengthened specimens increased by 25% compared with the un-strengthened specimens. Moreover, the ultimate displacement, the energy dissipation capacity and the stiffness of the strengthened specimens were obviously increased. GFRP bars embedded in the horizontal mortar joint and glutinous rice mortar filled into mortar joint to strengthen the severely damaged specimen could effectively recover the seismic performance of the specimen. Furthermore, the calculation formulas of the shear bearing capacity of the strengthened ancient pagoda walls with semicircular arched openings were developed.

Cyclic Behavior of Masonry Shear Walls Retrofitted with Engineered Cementitious Composite and Pseudoelastic Shape Memory Alloy.

The behavior of masonry shear walls reinforced with pseudoelastic Ni–Ti shape memory alloy (SMA) strips and engineered cementitious composite (ECC) sheets is the main focus of this paper. The walls were subjected to quasi-static cyclic in-plane loads and evaluated by using Abaqus. Eight cases of strengthening of masonry walls were investigated. Three masonry walls were strengthened with different thicknesses of ECC sheets using epoxy as adhesion, three walls were reinforced with different thicknesses of Ni–Ti strips in a cross form bonded to both the surfaces of the wall, and one was utilized as a reference wall without any reinforcing element. The final concept was a hybrid of strengthening methods in which the Ni–Ti strips were embedded in ECC sheets. The effect of mesh density on analytical outcomes is also discussed. A parameterized analysis was conducted to examine the influence of various variables such as the thickness of the Ni–Ti strips and that of ECC sheets. The results show that using the ECC sheet in combination with pseudoelastic Ni–Ti SMA strips enhances the energy absorption capacity and stiffness of masonry walls, demonstrating its efficacy as a reinforcing method.

Characterization of metallic bushings in RTM-made composites by in-situ leak detection under mechanical loading

Fiber reinforced plastics/polymers (FRP) provide excellent mechanical properties and corrosion resistance. Therefore, they are increasingly integrated into multi-material designs. This again requires intelligent solutions for the connection of different materials, e.g. FRP with metals. Metal bushings inserted in the FRP laminate can provide for removable connections for load transfer or fluid handling. Most research to this date was focused on mechanical aspects but not on leak formation. A pipe going through a FRP laminate is an application independent bushing used in this study to investigate the performance of different metals in terms of permanent tightness of the metal-FRP interface. For this, a customized leak detection method was established to detect leaks under in-plane cyclic loading. Three different metal alloys were tested and the bushing integration was varied (cutting a hole in the fabric vs. displacing the fibers). A special RTM-tooling was developed to manufacture the hybrid specimens. The maximum permissible strain for leak onset is used as characteristic parameter. The results show that the insertion method of the bushing has the greatest effect compared to the different alloys. Pressure sensitive films showed that compaction and residual stresses could be the reason for this.

Evaluation of the Limit State of a Six-Inch Carbon Steel Pipe Elbow in Base-Isolated Nuclear Power Plants

The installation of base isolation systems in nuclear power plants can improve their safety from seismic loads. However, nuclear power plants with base isolation systems experience greater displacement as they handle seismic loads. The increase in relative displacement is caused by the installed base isolation systems, which increase the seismic risk of the interface piping system. It was found that the failure mode of the interface piping system was low-cycle fatigue failure accompanied by ratcheting, and the fittings (elbows and tees) failed due to the concentration of nonlinear behavior. Therefore, in this study, the limit state was defined as leakage, and an in-plane cyclic loading test was conducted in order to quantitatively express the failure criteria for the SCH40 6-inch carbon steel pipe elbow due to low-cycle fatigue failure. The leakage line and low-cycle fatigue curves of the SCH40 6-inch carbon steel pipe elbow were presented based on the test results. In addition, the limit state was quantitatively expressed using the damage index, based on the combination of ductility and energy dissipation. The average values of the damage index for the 6-inch pipe elbow calculated using the force−displacement (P–D) and moment−relative deformation angle (M–R) relationships were found to be 10.91 and 11.27, respectively.