Resumo em Inglês:

Abstract The present research introduces a new configuration of thin-walled nested tube structure as a possible energy absorber subjected to lateral compression. The nested-tube structures were configured in a system comprising of four tubes arranged in different ways. All the nested systems were quasi-statically compressed in the lateral direction on a universal mechanical tester to obtain their energy absorption characteristics. Two modes of deformation, asymmetric mode referred to as “overlap” and symmetric mode referred to as “side-by-side”, were identified in the four-tubes nested systems. The specific energy absorbed by the inverted four-tubes systems was larger than that of the three-tubes nested systems by 20%. The experiments were also modelled using ABAQUSv6.13. Good correlations were obtained for the deformation modes and the corresponding lateral crush force-displacement. The validated model was thereafter used in parametric study to investigate the effectiveness of the nested system under two different boundary conditions; rotation of the specimen by different angles and impact at different angles.

Resumo em Inglês:

Abstract The concrete open-web sandwich slab is composed of the vierendeel girders intersecting each other. The vierendeel girder are composed of the upper rib, lower rib and shear key. The upper and lower rib mainly bear the axial force, and the shear keys mainly bear the shear force. A double scalar elastic damage constitutive model considering shear damage was derived to accurately simulate the mechanical property of the shear key in which one scalar reflected the volume damage, and the other one reflected the shear damage. The damage constitutive model in the study, the uniaxial tension and compression damage constitutive model (GB50010 (2015)), and the double scalar elastic damage constitutive model of tension and compression (Liu (2021)) were compared by simulating the shear key. The results showed that the elastic damage constitutive model proposed in the study can be used for the mechanical property analysis of the shear key and can better evolve the damage development of the shear key. The damage constitutive calculation model can be provided for the analysis of the vierendeel girder and the open-web sandwich slab.

Resumo em Inglês:

Abstract The study aims to investigate the behaviour of reinforced hybrid concrete columns consisted of two fully-bonded concretes subjected to biaxial loading. Experimental tests were conducted on 5 square columns of 200mm side dimensions. Two columns were cast from one type of concrete but with varied strength. The other three specimens were cast by hybrid concrete with different hybrid’s ratios. The study also comprised the derivation of an analytical model, simulating the behaviour of the tested column by numerical models, and statistical evaluation. Whereas a computer program was constructed to evaluate the ultimate strength of hybrid columns and finite element models were executed for the numerical analysis. Both results were compared with the experimental outcomes and good agreement was observed. The results revealed an increase in the ultimate load of hybrid columns by 33.5% as compared with conventional columns. Also, the ultimate load increased by 38% with decreasing the hybrid’s ratio to 0.16. It was concluded that hybrid columns with small hybrid’s ratios sustain higher loads, moments and exhibited fewer axial strains.

Resumo em Inglês:

Abstract This investigation analyzes the cost-benefit ratio of the Transformation Field Analysis to compute the elastoplastic behavior of periodically perforated metal sheets. Evaluation of accuracy and computational cost are analyzed by implementing a finite element approach coupled with the Transformation Field Analysis technique for different meshes and finite element orders. Numerical studies are employed to compare Transformation Field Analysis accuracy with standard Finite Element Analysis for elastoplastic analysis of periodically perforated metal sheets. Additionally, experimental data is employed to validate the Transformation Field Analysis results. The Transformation Field Analysis requires calculating the strain concentration and influencing tensors employing the finite element method. The numerical results show the technique's capabilities and favorable scenarios, besides the influence of domain discretization and finite element order.

Resumo em Inglês:

Abstract Active suspension is considered to be a good way to improve the ride comfort of high-speed trains. According to the output index requirements of train’s active suspension, a giant magnetostrictive actuator(GMA) is proposed. This is mainly because giant magnetostrictive materials(GMM) has the characteristics of fast response, large output force and high energy conversion rate. It is verified by experiments that the output force is proportional to the excitation current. It is found in the experiment that the excitation frequency should be greater than 120Hz to obtain a stable output force, and it is also found that preload and excitation frequency will affect response time. On the basis of experiments, a 2-DOF physical and mathematical model of the vertical quarter train is built. An MPC algorithm is designed to control GMA active suspension. Through simulation analysis, the proposed control algorithm is compared with passive suspension and active suspension based on PID control algorithm. Both theory and practice show that the proposed control algorithm is effective.

Resumo em Inglês:

Abstract An alternative elastoplastic model based on the Flory’s right Cauchy-Green stretch tensor decomposition is proposed and applied to model soft cores of sandwich panels. It does not follow usual methodologies as the additive decomposition or the Kröner-Lee multiplicative decomposition of strains. It is based on an important hyperelastic relation, Flory’s decomposition, from which the total strain is separated in two isochoric and one volumetric parts. Using this decomposition, the volumetric strain energy continues to be elastic during all elastoplastic analysis and the isochoric parts are managed to produce the plastic evolution. As a consequence of Flory’s decomposition, the plastic flow direction is known and independent of the yielding surfaces. Moreover, it provides the well known deviatoric nature of plastic strains. For validation purposes, the resulting formulation is implemented using a special 3D prismatic element in a geometrical nonlinear positional FEM computational code. The achieved numerical results are compared with literature experimental data of soft core laminated structural elements.

Resumo em Inglês:

Abstract Recently, the concrete-filled twin-layer steel-sheet composite wall systems (TSCWs) ‎have become recommended by the engineers in the modern structures, since it has high ‎energy absorption, ductility, and capacity compared to the corresponding conventional ‎wall systems. Therefore, this paper presents and discusses the literature of researches ‎particularly concerning this type of composite wall system. The review ‎includes 80 papers ‎that investigated the performance of TSCWs. These investigations classified TSCWs into ‎two types: twin-layer flat steel sheet composite wall systems ‎(TFSCWs) and twin-layer profiled steel-sheet composite wall systems (TPSCWs). The ‎classification of these two types of TSCWs was based on the form of the sheeting as well as on the type of applied load. This classification introduced comprehensive mapping ‎tables on the study details, loading, infill material, and interaction concept. Furthermore, the findings from this literature review are ‎discussed, and the research gaps are summarized for each TSCW type, including the impact of providing an ‎opening on the TSCWs performance.‎

Resumo em Inglês:

Abstract Deep soil mixing method (DSM) is a novel in situ technology in soil improvement in which different cementitious materials are mixed with soil and form a soil-cement column with improved engineering characteristics. Due to the configurations of these improved soil-cement columns, different types of DSM are formed, such as wall type, grid type, block type, etc. Due to the expansion in the construction of massive industrial structures, the use of block type DSM to control the settlements has grown. In order to use this soil improvement under the foundation of different structures, it is essential to study the seismic behavior of this mixture using site response analysis and wave propagation. In this paper, the seismic behavior of block type DSM is studied through fully nonlinear analyses. Nonlinear soil is modeled using the overlay method, which uses the parallel element modeling concept. Whereas, the DSM is modeled with elastic perfectly plastic behavior. It is observed that utilizing block type DSM has positive effects in seismic response of the soil layer, such as a considerable reduction in surface response acceleration.

Resumo em Inglês:

Abstract Rock materials are often subjected to cyclic loads during construction. A full understanding of the deformation behavior of rock under cyclic loads is of great significance in engineering. In this study, by using the endochronic constitutive model proposed by Valanis, the reinforcement function form and constitutive parameters of the endochronic model are improved. An endochronic plasticity constitutive program for rock based on the finite element method is used to study the mechanical properties of rock under different cyclic loading conditions (of maximum loading stress, amplitude, and confining pressure), and through the use of red sandstone, marble, and basalt, experimental and simulation results are compared to verify the model. The results show that the theory can better simulate the hysteresis loop width and cumulative plastic strain of rock under cyclic loading and, under different loading conditions, the numerical simulation results are consistent with the actual rock experimental law. Therefore, the endochronic plasticity constitutive model in this study can be applied to investigate the influence of cyclic loading on the dynamic deformation behavior of rock.

Resumo em Inglês:

Abstract Advances in manufacturing techniques have allowed more flexibility to the design and new possibilities to apply composites materials in lightweight structures. Novel techniques such as the automated fiber placement allow the fibers to follow curvilinear paths, making possible laminate properties that vary within the laminate plane. These types of laminates are known as variable stiffness laminates or variable angle tow. In this work, the maximum critical buckling load of composite panels with variable stiffness through a spatially varying fiber orientation has been analyzed for two different boundary conditions. This works compares the outcomes of in-plane stress and critical buckling load for linear and cubic fiber angle considering four aspect ratios. Manufacturing constraint has been considered in the analysis of the laminates. The finite element method has been applied to solve the system elliptic partial differential equations that govern the in-plane behavior of these panels. The Ritz method has been used to find the buckling loads for the variable stiffness panels. Results for four different aspects ratios are presented. Improvements in the buckling load of up to 18% for cubic fiber angle variation over linear fiber angle variation were found.