In-plane Tests 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.

Characterisation of out-of-plane shear behaviour of anisotropic sheet materials based on indentation plastometry

This paper presents a new methodology for characterising the out-of-plane plastic anisotropy behaviour of sheet metal, based on indentation testing. Conventionally, advanced yield criteria are used to describe plastic anisotropy, requiring multiple in-plane mechanical tests (such as uniaxial and biaxial tests) to calibrate a model. However, in certain forming applications (e.g. blanking, ironing and incremental forming), the influence of mechanical behaviour through thickness cannot be ignored, necessitating the characterisation of out-of-plane material behaviour. To do this, a 3D plastic anisotropy model must be used and calibrated for the out-of-plane shear parameters, which can be difficult to determine. Researchers often assume an isotropic case or equal shear parameters for in-plane and out-of-plane behaviour. More advanced calibrations involve the crystal plasticity model. In this work, we propose a two-stage calibration procedure. In the first stage, we calibrate the in-plane parameters of the YLD2004–18p yield function conventionally. In the second stage, after fixing the in-plane parameters, we determine the remaining out-of-plane shear parameters based on the results of the ball indentation test. We show for the first time that out-of-plane shear parameters can be determined from a macro-mechanical test for a 2.42 mm thick cold-rolled AA5754-H22 series aluminium sheet.

Experimental study on seismic behavior of fabricated lightweight steel solid waste High-strength foam concrete composite wall

In order to actively implement the “dual carbon” goal and promote the popularization and application of green energy-saving prefabricated buildings in low-rise and multi-storey residential structures in villages and towns, a prefabricated light steel solid waste high-strength foam concrete composite wall was proposed. The wall is composed of high-strength foam concrete, cold-drawn steel wire mesh and cold-formed steel, which can realize the integration of load-bearing and energy-saving of wall components. The failure characteristics, hysteresis characteristics, bearing capacity and deformation performance, stiffness degradation and energy dissipation capacity of the wall specimens with different structures were analyzed through monotonic load and in-plane lateral cyclic loading test on three different wall specimens. The results show that under the action of cyclic load, the wall specimens with three different structures all have shear failure, and the wall specimens without cold-formed steel at the ends have low bearing capacity and poor seismic behavior. The bearing capacity and seismic behavior of the wall specimens with cold-formed steel at the ends were significantly improved, and the cold-formed steel, cold-drawn steel mesh, and high-strength foam concrete had good coordination performance. Considering the inherent characteristics of foam concrete, based on the existing specifications, the formula for calculating the shear bearing capacity of the prefabricated light steel solid waste high-strength foam concrete composite wall is given. The shear bearing capacity of wall members with different structures, different loading methods and different axial compression ratios are tested and calculated, and the calculated results of shear bearing capacity are in good agreement with the test results.

Seismic Retrofitting of Indonesian Masonry Using Bamboo Strips: An Experimental Study

Unreinforced masonry (UM) is well known as a vulnerable structure against earthquakes. However, it remains a popular structural system for low-rise residential housing in many high-seismicity areas, particularly in developing regions due to its low cost and easy construction. In the present study, a retrofitting strategy using locally available material, bamboo strips, was proposed. In addition to its fast-growing rate, the tensile strength of bamboo is considered high, nearly comparable to its steel counterpart. A series of experimental tests were performed in this study, including the bamboo tensile test, the mortar flexural test, the diagonal compressive shear test on the masonry assemblages, and the in-plane pushover test on masonry wall specimens without and with bamboo reinforcement. The retrofitted specimens with different volumes of bamboo reinforcement were also considered. The results show that the application of bamboo reinforcement, at a proper volume, significantly increases the ultimate strength and the ductility of the masonry wall. Such results indicate that the brittle failure of UM structures can be avoided by means of bamboo retrofitting.

In-Plane Dynamic Analysis of Complex-Shaped Laminated Cracked Plates with Irregular Holes

This paper reports the unified in-plane vibration solutions of irregular laminated cracked plates having complex holes under various boundary restrictions. According to the geometric features of the studied structure, an irregular plate with/without the dropoff ply is decomposed into a variety of intact triangular and quadrilateral laminated elements. These elements are then mapped to two-dimensional regular square plates for deriving the unified formulations of the element energy integral. Simultaneously, the boundary restrictions at the external edge of the plate and fully rigid connections between the substructures are emulated through in-plane translational springs. The in-plane variables of intact plate elements are characterized by Chebyshev element expansions. Thus, the in-plane modal and harmonic response solutions are extracted by performing the general Rayleigh–Ritz procedures. Some in-plane vibration tests and finite element simulations concerning cracked plates with built-in holes are further executed. The applicability and accuracy of the proposed dynamic model are validated by comparison with the experimental data and those computed by finite element models (FEM). Also, some parametric cases are presented to investigate the influence of structural parameters, laminated configurations, and the dropoff ply effect on the in-plane dynamic characteristics of complex-shaped plates, which may provide useful benchmarks for structural design and damage detection of engineering structures.

Comparative analysis of the mechanical performance of 3D woven honeycomb composites produced in warp and weft directions

This research work focuses on the design and manufacturing of 3D woven honeycomb fabrics and their composites in both warp and weft directions. An experimental investigation of the mechanical properties of these two composite materials was carried out. For this purpose, at first, a 3D woven honeycomb in both directions was fabricated on a customized multi-beam 3D weaving machine using E-glass fibers. The composites were created by VARIM (Vacuum assisted resin infusion method) process using epoxy resin and Aradur hardener. The mechanical characteristics such as compression, three-point bending, and in-plane impact of composite samples were investigated keeping cell parameters constant. There will be a change in composite properties as tension in warp and weft is different. Crimp and modulus will also be different. The comparison of mechanical properties of these two honeycomb composite samples revealed that warp way honeycomb shows better properties in edgewise compression and three-point bending test while weft way honeycomb shows higher energy absorption under flatwise compression and in-plane impact test. The direction of cell channels gives the direction of loading to the threads, which affects the mechanical properties.

Evaluation of collapse resistance of masonry-infilled RC frame building under blast loadings

As non-structural members, the masonry-infilled (MI) walls are always ignored in the numerical and experimental study on the blast and collapse resistance of RC frame buildings, while the contribution of MI walls on preventing the large-scale collapse has been observed according to the past explosion incidents. This paper aims to propose and verify a numerical simulation approach considering the blast- and collapse-resistant effects of MI walls, and further evaluate the collapse resistance of MI RC frame buildings under blast loadings. Firstly, based on our previously validated hybrid finite element (FE) modelling approach for RC frame structures and Multi-material Arbitrary Lagrangian-Eulerian method for applying blast loadings, the simplified micro-model and compressive strut model of the MI wall were adopted to characterize its blast and collapse resistance in the near- and far-regions of building, respectively. Secondly, the out-of-plane explosion test and in-plane quasi-static collapse test were numerically reproduced to verify the applicability of adopted FE modelling approaches for MI walls. Furthermore, by establishing the hybrid FE models of prototype bare and MI RC frame buildings, the propagation of blast waves, damage modes as well as dynamic responses of RC frame buildings under two design-based threat of explosion at corner and side columns were derived and examined. Finally, the applicability of the anti-collapse design method specified by U.S. Department of Defense, i.e., alternate path method (APM), for RC frame buildings under external explosions was examined. It derives that, (i) the presence of MI walls can efficiently block the blast waves into the building structures, and relieve the upward arch of slabs and damage degree of interior columns; (ii) compared with the bare RC frame buildings, the MI walls provide sufficient alternate load paths to enhance the structural robustness and restore the gravity stability of MI RC frame buildings after the explosions; (iii) the APM is only applicable to evaluate the collapse resistance of MI RC frames under the external explosion of cargo van bomb (1814 kg of equivalent TNT) or even less charge weight.

In-plane cyclic tests of strengthened rubble stone masonry

This paper focuses on the in-plane behaviour of rubble stone masonry with lime mortar strengthened with different solutions. For that, 12 rubble stone masonry wall specimens, with construction features typical of ancient historic buildings of Southern Portugal and Mediterranean countries, were subjected to in-plane quasi-static cyclic tests. The applied retrofit solutions are specific for historic masonry buildings, such as the injection of mortar and FRCM systems, with glass and carbon meshes. The main experimental results obtained are presented through envelope curves, in terms of resistance, deformation capacity, and deformed shapes. Moreover, dissipated energy is also commented on. Horizontal drift results are compared and analysed together with the ones obtained in the literature for equivalent strengthening solutions in masonry walls.

In-plane/out-of-plane seismic performance of masonry infilled RC frame structure made of nano-SiO2 reinforced mortar: Experimental study

Due to the seismic vulnerability of conventional masonry infill wall Reinforced Concrete (RC) frame buildings, which caused the infill wall structure to break and collapse, resulting in serious casualties and property damage. It was necessary to fully understand the action mechanism and seismic strengthening of the infill wall structure. Considering that few researches had paid attention to the effect of mortar performance on the seismic behaviors of infill wall structure, this study was the first to use a nano-SiO2 (NS) reinforced mortar to construct masonry infill wall RC frame structure. The pure out-of-plane (OOP) and in-plane and out-of-plane (IPOOP) loading tests were conducted to validate the structure's seismic performance. The experimental results of comparison with ordinary mortar specimen were shown. Due to the mitigation of the cracking of wall in pure OOP test, the initial stiffness, load-bearing capacity and ultimate displacement of new mortar specimen were increased by 65.88%, 23.57% and 11.12%, respectively. However, both infill wall specimens exhibited the similar cracking characteristics and load-displacement response, those indicated that the improvement in mortar performance was not sufficient to change the failure mode. In the in-plane (IP) tests, the infill walls constructed with new mortar provided a better diagonal bracing mechanism, resulting in a 13.32% and 12.67% increase in the IP load-bearing and energy dissipation capacity. The less side shear cracking of infill wall caused stiffness degrades more slowly. In the IPOOP tests, at approximately the same previous IP damage level, the slower propagation of crack resulted in a slower reduction in the load-bearing capacity and an increase in the deformability during subsequent OOP loading. Therefore, the application of the new mortar improved the shear and bond strength of the members, which mitigated IP damage and improved the stability of the wall, while slowed down the OOP cracking of the wall and reduced the risk of collapse.

Prediction and characterization of forming limits at necking from shear to equi-biaxial loading using the biaxial tensile testing method: Feasibility study and application to AA6061-T4

Determination of forming limit curve (FLC) over a wide range of strain paths can provide a more thorough understanding of sheet metal formability. In this work, for the first time, in-plane biaxial tensile tests employing two distinct cruciform specimens are performed to construct the FLC of AA6061-T4 sheets from shear to equi-biaxial stretching. Four different necking detection methods are investigated in a FE (finite element) procedure to find proper ones for the defined specimens. This procedure consists of the FE modeling of the biaxial tensile test and the Marciniak test. An anisotropic Gurson-Tvergaard-Needleman (GTN) plasticity model based on Hill’48 yield function is calibrated and implemented in simulations to reproduce the anisotropic plasticity and failure behavior of AA6061-T4 sheets. Then, the selected necking detection methods are applied to the biaxial tensile test to experimentally identify the limit strains at necking. The results show that considering two distinct cruciform specimens is an effective solution for the biaxial tensile test to determine the FLC covering a wider range of strain paths. The predicted FLCs show good agreement with the experiments, indicating that the numerical biaxial tensile test combined with the anisotropic GTN plasticity model is an efficient tool for predicting sheet metal formability.

Experimental study on in-plane behavior of composite frame slabs and the influence of out-of-plane effect

This paper experimentally investigated the in-plane behavior of a steel–concrete composite frame slab under cyclic loading by considering the influence of the out-of-plane effect. A pure in-plane loading test and two in-plane loading tests of frame slabs with different out-of-plane loads were designed and conducted. Subsequently, the test observations, load–displacement relationships, and shear and flexural deformation components were discussed to investigate the in-plane load resistance behaviors and failure mechanisms of the composite frame slabs with different out-of-plane loads. The experimental results of the pure in-plane loading test demonstrated an evident shear cracking concentration behavior and a pinching hysteretic curve associated with a typical shear-tension failure mode of the composite frame slab. Further, the in-plane loading test of the composite frame slab with small out-of-plane loads also exhibited a typical shear-tension failure mode, and thus had a load–displacement relationship similar to that of the pure in-plane loading test. In contrast, the in-plane loading test with large out-of-plane loads exhibited a horizontal shear failure mode, and thus exhibited a load–displacement curve with a more obvious pinching effect and significantly decreased ultimate load capacity. In addition, the influence of the out-of-plane loads on the in-plane stiffness of the composite frame slab was analyzed.

In-Plane Behaviour of Unreinforced Masonry Strengthened with a Structural Glass Window: A Proof of Concept

Innovative solutions for seismic-retrofitting existing structures are currently required, as often traditional strategies are expensive, non-reversible, highly invasive, and/or fail to address both serviceability and ultimate limit states together. The present paper describes a preliminary experimental campaign performed at TU Delft to investigate an innovative structural glass window for strengthening masonry buildings. To this purpose, a prototype composed of a timber frame, a semi-rigid adhesive, and a 20 mm thick structural glazing layer was designed. The prototype aimed to improve the structure’s behavior against minor but more frequent service vibrations (SLS), as well as against ultimate ones (ULS). Specifically, an increase in the structure’s in-plane capacity and stiffness was targeted to reduce cracking at low drifts/displacements, while at larger drifts, the adhesive’s tearing and timber crushing were used to activate damping. To evaluate the prototype’s performance, a quasi-static, cyclic, in-plane test on a strengthened full-scale wall was performed and compared with available data on a similar, yet unstrengthened, wall. Although the benefits were not pronounced in terms of cracking and energy dissipation, the implementation of the proposed strategy provided an increase in terms of initial stiffness (18%), force capacity (8%, 36%), and ductility (220%, 135%). This outcome provides the ground for numerical studies that will help better delineate the proposed strategy and improve the current design.

Failure progression and toughening mechanism of 3D-printed nacre-like structures under in-plane compression

Nacre (also called mother-of-pearl) is known to have a delicate balance of stiffness, strength, and toughness, which originates from its ‘brick-and-mortar’ structure. In this study, nacre-like structures are fabricated using a high-resolution, multi-material 3D printer, where two different polyurethane acrylates (one that is hard and another that is soft) are used to represent the tablets and matrix. Six nacre-like structures are designed and fabricated to explore the influence of geometric parameters on the mechanical behaviors. Quasi-static in-plane compression tests and simulations are carried out to explore the failure mechanism of the nacre-like structures. The results show that the quasi-static compression responses of nacre-like structures have four stages: elastic, plateau, fragmentation, and densification. It is found that tuning the nacre architecture can optimize the mechanical performance of the specimen, including the peak load, ductility and stress reduction behavior et al. As the results of the numerical model show good agreement with the stress–strain response observed in the experiments, the model is applied to further investigate the strain distributions of the nacre-like structures. The patterns of the strain distribution suggest that synergistic deformation is the key toughening mechanism for the nacre-like structures.

In-plane seismic performance of an innovative steel modular reinforcement system for URM walls

An experimental and numerical research, aimed at evaluating the in-plane seismic performance of an innovative steel modular system for the reinforcement of load-bearing masonry walls (named "Resisto 5.9", designed by Progetto Sisma s.r.l.), is currently underway at the EUCENTRE Foundation in Pavia. Two different masonry typologies, representing common solutions in Italian existing buildings, were considered in this campaign: one made up with solid clay bricks and lime mortar, with "header bond" pattern, and the other with a typical Italian hollow clay "doppio UNI" unit and cement-lime mortar, assembled in a "Flemish bond" pattern. The experimental tests included first the complete mechanical characterization of units, mortars, masonry typologies and of the strengthening system components (i.e. steel elements and anchors). In-plane quasi-static tests were performed on different batches of full--scale specimens to investigate the influence of the proposed reinforcement system on the lateral in-plane response of the walls, compared to their unreinforced conditions. The cyclic behaviour of the masonry piers was analysed in terms of elastic stiffness, lateral strength, displacement capacity and energy dissipation, depending on the achieved damage mechanism. The numerical study of the ongoing campaign consisted of a series of parametric analyses on advanced discontinuous models based on the Distinct Element Method (DEM), considering different wall dimensions, vertical load levels and boundary conditions, in addition to those tested experimentally. Moreover, the numerical campaign was extended also to other possible masonry typologies, varying the bond pattern and the mechanical properties with respect to the experimentally tested solutions. In this paper, the results of the experimental tests on solid brick masonry together with a preliminary overview of the findings of the numerical study, still ongoing, were reported.

Study on the effectiveness of the CRM system: numerical simulations on masonry piers with OOFEM layered elements

A macro-modeling strategy for masonry elements strengthened by using the Composite Reinforced Mortar (CRM) system is presented in the paper. The CRM system consists in the application, on the walls surface, of a mortar coating reinforced with pre-formed composite meshes, based on long fibers, and in the installation of connectors in the masonry thickness. The numerical strategy, developed by using of the free, open-source, finite elements code OOFEM, is based on multi-layer elements, composed of plies oriented along the wall thickness, representing the masonry, the plaster and fiber-based reinforcement.Non-linear static analyses are performed; a "Concrete Damage Plasticity" material model is adopted for both the masonry and the mortar coating, while, for the equivalent layer representing the composite mesh, an elastic-brittle behavior in tension is considered. The characteristics of the materials are independently calibrated on the basis of the results of experimental tests performed on unstrengthened masonry, on mortar samples, on composite yarns and on CRM coupons. The model is applied to simulate the in-plane and out-of-plane behavior of CRM strengthened piers; the results are compared with experimental outcomes coming from in-plane shear-compression tests and out-of-plane three-point bending tests performed on rubble stone samples (350 mm thick). The comparison shows that the simplified model is able to realistically reproduce the experimental results both in terms of resistance and displacement capacities and in terms of failure modes.

Experimental tests for seismic assessment of ventilated façades

Ventilated facades are currently one of the most used technologies for external envelope of buildings. This kind of external cladding offers many advantages in terms of energy saving, sound insulation, protection of the structures, and has also a considerable architectural value. However, these nonstructural components must have suitable features to ensure their integrity in case of earthquakes. Their damage during a seismic event can have relevant consequences, on the safety of human life, on the operability of strategic buildings and can also have a significant economic impact related to post-earthquake retrofit actions. The aforementioned reasons paved the way to several studies referring to the evaluation of seismic behavior of such components, especially by means of experimental tests, even if up to now no standard procedures for seismic assessment of ventilated facades are available in Europe. This paper focuses on an experimental campaign carried out on a ventilated façade sample, 2.4 m wide and 4 m high. An innovative seismic test facility, located at the Construction Technologies Institute (ITC) of the National Research Council of Italy (CNR) in San Giuliano Milanese (Milan), is used to perform both quasi-static and dynamic tests on the sample.Results of the tests performed by using existing experimental procedures for in-plane crescendo tests, i.e. AAMA 501.4 (2009), are compared with those obtained by applying a new loading protocol proposed by the Authors. The innovative aspect of the latter consists in the introduction of test frequencies closer to those of the buildings usually hosting this kind of façades and then obtaining a more realistic behaviour of the tested specimen. The obtained results will be the basis for the definition of harmonized assessment methods for the seismic evaluation of ventilated façades to be possibly introduced in harmonized European technical specifications.

Asphalt shingle modeling and parameter estimation under short period loading condition

Asphalt shingles are one of the major sources of insurance damage claims after a hailstorm. The mechanical behavior of asphalt shingles needs to be thoroughly investigated to evaluate their hail resistance performance. In this study, tensile tests are conducted on the asphalt shingles samples and one of the important components of asphalt shingles - the fiberglass base mat. The elastic moduli of samples cut from different orientations vary. The simplified representative volume element (RVE) model of asphalt shingle is developed, and its constituent material properties are estimated through optimization to ensure the simulation results match the experimental results. To investigate the effectiveness of modeling asphalt shingles as an orthotropic material, the developed asphalt shingle RVE model is used to estimate the effective orthotropic material model properties and the in-plane tensile tests simulation results can reasonably match the experimental results. Meanwhile, the effect of fiber volume ratio and constituent material properties on the asphalt shingle moduli are further investigated based on the asphalt shingle RVE model.

Behaviour and design of high strength steel homogeneous and hybrid welded I-section beams

The behaviour and design of high strength steel (HSS) beams are addressed in the present study. Six in-plane three-point bending tests on three different welded I-sections − two homogeneous S690 steel welded I-sections and one hybrid welded I-section with S690 steel flanges and an S355 steel web, were first conducted. The beam tests were carried out in major axis bending and a bespoke restraint system was designed and employed in the test programme to prevent lateral-torsional buckling. Following the experimental investigation, a thorough finite element (FE) modelling programme was performed, which included a validation study confirming the accuracy of the developed FE models in replicating the flexural behaviour of HSS welded I-section beams, and a parametric study generating additional FE data on HSS welded I-section beams over a broader range of cross-sectional slendernesses, steel grades and loading configurations. The test results obtained in the present study and collected from the literature, together with the generated FE data from the parametric study, were used to evaluate the suitability of the current Eurocode 3 cross-section slenderness limits for HSS homogeneous and hybrid welded I-sections in bending. It is shown that the current Eurocode Class 2 and Class 3 slenderness limits are suitable for the classification of the outstand flange (in compression) and internal web (in bending) elements of both HSS homogeneous and hybrid welded I-sections subjected to major axis bending, while stricter Class 1 slenderness limits are considered necessary to achieve sufficient rotation capacity for plastic design. The findings from the present study indicate that plastic design can be used for HSS structures, provided the proposed stricter Class 1 slenderness limits are employed.

Development and Experimental Verification of a High-Temperature and In-Plane Biaxial Testing Apparatus

Given the lack of primary data on heat-resistant composites under high-temperature conditions, the focus of this paper is the development of an in-plane biaxial apparatus under high temperatures and complex loads. Besides loading complex loads up to 80 kN, the apparatus can load under high-temperatures up to 2500 °C. A C/C tensile/compression test at 1700 °C illustrates the successful use of high-temperature digital speckle pattern technology to evaluate the in-plane mechanical properties of heat-resistant composites at 1700 °C under biaxial stress. A high-temperature impact test of a graphite specimen at 2500 °C shows that this apparatus can load at a high temperature in a vacuum and inert gas atmosphere. The yield characteristics of the Q235 steel sheet under in-plane stress show that the apparatus can conduct various mechanical loads, including tension–tension, tension–compression, and compression–compression loads. The proposed equipment can measure the in-plane mechanical properties of composite materials, particularly heat-resistant composites. The obtained results can be applied to structural design, life prediction, and reliability evaluation, as well as for the development, research, and design of aerospace instruments and critical materials.

Impact Tests and Computed Tomography Scans of Prismatic Battery Cells

Recently, the use of prismatic cells in electric vehicles has increased significantly. Unlike the cylindrical or pouch format, the prismatic cell format has not been sufficiently investigated. In this study, quasi-static mechanical tests are performed on prismatic cells. The tests include a cylindrical and a hemispherical impactor that mechanically load the cells in all three spatial directions. In both in-plane directions, a cell stack consisting of three cells is tested to capture the influence and loading of the outer cells of a cell stack. It is found out that, in the in-plane tests, short-circuiting occurs first in the outer cells and subsequently in the middle cell, which is targeted by the impactor. This result can also be supported by computed tomography scans. The results illustrate that, when evaluating the crash safety of battery cells, several cells should always be tested in order to capture the different loading of the cells.