• Computers and Concrete
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• v.25 no.4
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• pp.293-302
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• 2020

Connections play a significant role in strength of structures against earthquake-induced loads. According to the post-seismic reports, connection failure is a cause of overall failure in reinforced concrete (RC) structures. Connection failure results in a sudden increase in inter-story drift, followed by early and progressive failure across the entire structure. This article investigated the cyclic performance and behavioral improvement of shape-memory alloy-based connections (SMA-based connections). The novelty of the present work is focused on the effect of shape memory alloy bars is damage reduction, strain recoverability, and cracking distribution of the stated material in RC moment frames under seismic loads using 3D nonlinear static analyses. The present numerical study was verified using two experimental connections. Then, the performance of connections was studied using 14 models with different reinforcement details on a scale of 3:4. The response parameters under study included moment-rotation, secant stiffness, energy dissipation, strain of bar, and moment-curvature of the connection. The connections were simulated using LS-DYNA environment. The models with longitudinal SMA-based bars, as the main bars, could eliminate residual plastic rotations and thus reduce the demand for post-earthquake structural repairs. The flag-shaped stress-strain curve of SMA-based materials resulted in a very slight residual drift in such connections.

• Structural Engineering and Mechanics
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• v.76 no.3
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• pp.337-354
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• 2020

Reinforced concrete beam-column (RCBC) joints of laterally loaded unbraced frames are sometimes controlled by their shear behavior. This behavior relies on multiple and interdependent complex mechanisms. There are already several studies on the influence of some parameters on the shear strength of reinforced concrete joints. However, there are no studies methodically tackling all the most relevant parameters and quantifying their influence on the overall joint behavior, not just on its shear strength. Hence, considering the prohibitive cost of a comprehensive parametric experimental investigation, a nonlinear finite element analysis (NLFEA) was undertaken to identify the key factors affecting the shear behavior of such joints and quantify their influence. The paper presents and discusses the models employed in this NLFEA and the procedure used to deduce the joint behavior from the NLFEA results. Three alternative, or complementary, quantities related to shear are considered when comparing results, namely, the maximum shear stress supported by the joint, the secant shear stiffness at maximum shear stress and the secant shear stiffness in service conditions. Depending on which of these is considered, the lower or higher the relevance of each of the six parameters investigated: transverse reinforcement in the joint, intermediate longitudinal bars and diagonal bars in the column, concrete strength, column axial load and confining elements in transverse direction.

• Structural Engineering and Mechanics
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• v.72 no.4
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• pp.409-420
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• 2019

The paper presents the results of an experimental and numerical programme to characterize the behaviour of steel beams reinforcement by composite plates. Important failure mode of such plated beams is the debonding of the composite plates from the steel beam due to high level of stress concentration in the adhesive at the ends of the composite plate. In this new research, an experimental and numerical finite element study is presented to calculate the stresses in the sika carbodur and sika wrap reinforced steel beam under mechanical loading. The main objective of the experimental program was the evaluation of the force transfer mechanism, the increase of the load capacity of the steel beam and the flexural stiffness. It also validated different analytical and numerical models for the analysis of sika carbodur and sika wrap reinforced steel beams. In particular, a finite element model validated with respect to the experimental data and in relation to the analytical approach is presented. Experimental and numerical results from the present analysis are presented in order to show the advantages of the present solution over existing ones and to reconcile debonding stresses with strengthening quality.

• Smart Structures and Systems
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• v.24 no.4
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• pp.491-506
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• 2019

Literature regarding concrete walls reinforced by super elastic shape memory alloy (SMA) bars is rather limited. The seismic behavior of a system concurrently including a distinct steel reinforced concrete (RC) wall, as well as another wall reinforced by super elastic SMA at the first story, and steel rebar at upper stories, would be an interesting matter. In this paper, the seismic response of such a COMBINED system is compared to a conventional system with steel RC concrete walls (STEEL-Rein.) and also to a wall system with SMA rebar at the first story and steel rebar at other stories ( SMA-Rein.). Nonlinear time history analysis at maximum considered earthquake (MCE) and design bases earthquake (DBE) levels is conducted and the main responses like maximum inter-story drift ratio and residual inter-story drift ratio are investigated. Furthermore, incremental dynamic analysis is used to accomplish probabilistic seismic studies by creating fragility curves. Results demonstrated that the SMA-Rein. system, subjected to DBE and MCE ground motions, has almost zero and 0.27% residual maximum inter-story drifts, while the values for the COMBINED system are 0.25% and 0.51%. Furthermore, fragility curves show that using SMA rebar at the base of all walls causes a larger probability of exceedance 3% inter-story drift limit state compared to the COMBINED system. Static push over analysis demonstrated that the strength of the COMBINED model is almost 0.35% larger than that of the two other models, and its general post-yielding stiffness is also approximately twice the corresponding stiffness of the two other models.

• Earthquakes and Structures
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• v.8 no.1
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• pp.225-251
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• 2015

This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.413-423
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• 2021

Piers are the main lateral force-resisting members of high-speed railway (HSR) bridges used in China and are characterized by low axial load ratios, low longitudinal reinforcement ratios, low stirrup ratios, and high shear span ratios. It is well known that flexural, flexural-shear, and shear failures of piers may occur during an earthquake. In this study, a new shear strength model was developed to simulate the seismic failure of HSR solid piers accurately. First, low cyclic-loading test data of solid piers obtained in recent years were collected to set up a database for model verification. Second, based on the test database, the applicability of existing shear strength models was evaluated. Finally, a new shear strength model for HSR solid piers with round-ended cross-sections was derived based on the truss model and ultimate equilibrium theory. In comparison with existing models, it was demonstrated that the proposed model could be used to predict the shear strength of HSR piers more accurately.

• Steel and Composite Structures
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• v.39 no.3
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• pp.275-290
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• 2021

The main purpose of this research work is to investigate the critical buckling load of functionally graded (FG) porous plates with graphene platelets (GPLs) reinforcement using generalized differential quadrature (GDQ) method at thermal condition. It is supposed that the GPL nanofillers and the porosity coefficient vary continuously along the plate thickness direction. Generally, the thermal distribution is considered to be nonlinear and the temperature changing continuously through the thickness of the nanocomposite plates according to the power-law distribution. To model closed cell FG porous material reinforced with GPLs, Halpin-Tsai micromechanical modeling in conjunction with Gaussian-Random field scheme are used, through which mechanical properties of the structures can be extracted. Based on the third order shear deformation theory (TSDT) and the Hamilton's principle, the equations of motion are established and solved for various boundary conditions (B.Cs). The fast rate of convergence and accuracy of the method are investigated through the different solved examples and validity of the present study is evaluated by comparing its numerical results with those available in the literature. A special attention is drawn to the role of GPLs weight fraction, GPLs patterns through the thickness, porosity coefficient and distribution of porosity on critical buckling load. Results reveal that the importance of thermal condition on of the critical load of FGP-GPL reinforced nanocomposite plates.

• Steel and Composite Structures
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• v.32 no.5
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• pp.583-594
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• 2019

In recent years, composite concrete-filled steel tubular (CFST) members have been widely utilized in framed building structures like beams, columns, and beam-columns since they have significant advantages such as reducing construction time, improving the seismic performance, and possessing high ductility, strength, and energy absorbing capacity. This paper presents a new composite joint - the composite CFST beam-column joint in which the CFST member is used as the beam. The main components of the proposed composite joint are steel H-beams, CFST beams welded with the steel H-column, and a reinforced concrete slab. The steel H-beams and CFST beams are connected with the concrete slab using shear connectors to ensure composite action between them. The structural performance of the proposed composite joint was evaluated through an experimental investigation. A three-dimensional (3D) finite element (FE) model was developed to simulate this composite joint using the ABAQUS/Explicit software, and the accuracy of the FE model was verified with the relevant experimental results. In addition, a number of parametric studies were made to examine the effects of the steel box beam thickness, concrete compressive strength, steel yield strength, and reinforcement ratio in the concrete slab on the proposed joint performance.

• Journal of Conservation Science
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• v.34 no.6
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• pp.549-556
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• 2018

In November 2011, various artifacts were excavated from the No. 8 stone-lined tomb in Suchon-ri, Gongju by the Chungnam Institute of History and Culture. These included artifacts with lacquered mainframe and silvery metal ornament. These were recovered together with soil and underwent conservation treatment. In this paper, we discuss the scientific analysis and conservation treatment of the lacquered artifacts excavated from the Suchon-ri site. Among our findings is that the artifacts have three layers of lacquer coating and the metal parts are primarily composed of Ag. As the artifacts were recovered with soil from the site, the soil was removed from underneath and inside the artifacts. The inside of the lacquerware was reinforced with rayon paper using 3% funori, and the metal was treated with acrylic resin after removing the acrylic resin previously used to recover the artifact, followed by cleaning. The metal was also internally reinforced with gauze. Finally, the interior reinforcement was made using PVA and resin in pulp and attached with funori to preserve the shape of the lacquerware, and the exposed rayon was finished with acrylic paint. The main advantages of this study are its review of conservation treatment strategies for lacquer artifacts whose numbers have recently increased, and the application of new conservation treatment methods.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.34-41
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• 2020

Ready-mixed concrete is unconsolidated concrete typically transported to construction sites by using mixer trucks. A proper rotation of concrete is necessary to prevent its solidification in mixer trucks during transport: in accordance with the manufacturing method and quality inspection prescribed in KSF4009, this movement is maintained after the manufacturing of concrete in professional production plants and the addition of water, solid materials, and admixtures. Unfortunately, mixer truck parts wear out over long periods of time. In order to improve the wear resistance of the main part of mixer trucks, we used a steel plate with good wear resistance or partially added a reinforcement plate. In this study, we first tested the properties of concrete (as required for the DEM), and then carried out mixing and discharge simulations to define the actual operating conditions of mixer trucks. For each condition, we calculated the amount and location of wear. The reliability of our results was finally verified by comparing them with the measurement values. Overall, this study provided basic data for an optimal design of mixer trucks: one that would reduce the vehicles' weight and production costs.