• Steel and Composite Structures
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• v.46 no.1
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• pp.93-105
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• 2023

This paper examines a high-speed railway CRTS-II ballastless track-bridge system. Using the stationary potential energy theory, the mapping analytical solution between the bridge deformation and the rail vertical geometric irregularity was derived. A theoretical model (TM) considering the nonlinear stiffness of interlayer components was also proposed. By comparing with finite element model results and the measured field data, the accuracy of the TM was verified. Based on the TM, the effect of bridge deformation amplitude, girder end cantilever length, and interlayer nonlinear stiffness (fastener, cement asphalt mortar layer (CA mortar layer), extruded sheet, etc.) on the rail vertical geometric irregularity were analyzed. Results show that the rail vertical deformation extremum increases with increasing bridge deformation amplitude. The girder end cantilever length has a certain influence on the rail vertical geometric irregularity. The fastener and CA mortar layer have basically the same influence on the rail deformation amplitude. The extruded sheet and shear groove influence the rail geometric irregularity significantly, and the influence is basically the same. The influence of the shear rebar and lateral block on the rail vertical geometric irregularity could be negligible.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.817-822
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• 2006

Post-tensioning the full-depth precast slab longitudinally is to eliminate the tensile stresses in the transverse joints and to prevent any leakage through the joints. When the prestressing is applied to full-depth precast slab which does not composite steel girder, stress concentration occurs at the corners of shear pocket, and compressive stress is not uniformly distributed in the section of precast slab. In this paper, full-depth precast slabs using four different shapes of shear pockets are analyzed by commercial finite element program. Round type of shear pockets is superior to reduction in stress concentration.

• Steel and Composite Structures
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• v.45 no.3
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• pp.455-466
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• 2022

Despite the considerable lateral stiffness and strength of the Concentrically Braced Frame (CBF), it suffers from low ductility and low seismic dissipating energy capacity. The buckling of the diagonal members of the CBF systems under cyclic loading ended up to the shortcoming against seismic loading. Comprehensive researches have been performing to achieve helpful approaches to prevent the buckling of the diagonal member. Among the recommended ideas, metallic damper revealed a better success than other ideas to enhance the behavior of CBFs. While metallic dampers improve the behavior of the CBF system, they increase constructional costs. Therefore, in this paper, a new steel damper with flexural mechanism is proposed, which is investigated experimentally and numerically. Also, a parametrical revision was carried out to evaluate the effect of thickness, slenderness ratio, angle of the main plate, and height of the main plates on the proposed damper. For the parametrical study, 45 finite element models were analyzed and considered. Experimental results, as well as the numerical results, indicated that the proposed damper enjoys a stable hysteresis loop without any degradation up to a high rotation equal to around 31% that is significantly considerable. Moreover, it showed a suitable performance in case of ductility and energy dissipating. Besides, the necessary formulas to design the damper, the required relations were proposed to design the elements outside the damper to ensure the damper acts as a ductile fuse.

• Steel and Composite Structures
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• v.44 no.4
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• pp.473-488
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• 2022

A high-speed railway (HSR) bridge may undergo long-term deformation due to the degradation of material stiffness, or foundation settlement during its service cycle. In this study, an analytical model is set up to evaluate the influence of this long-term vertical bridge deformation on the track geometry. By analyzing the structural characteristics of the HSR track-bridge system, the energy variational principle is applied to build the energy functionals for major components of the track-bridge system. By further taking into account the interlayer's force balancing requirements, the mapping relationship between the deformation of the track and the one of the bridge is established. In order to consider the different behaviors of the interlayers in compression and tension, an iterative method is introduced to update the mapping relationship. As for the validation of the proposed mapping model, a finite element model is created to compare the numerical results with the analytical results, which show a good agreement. Thereafter, the effects of the interlayer's different properties of tension and compression on the mapping deformations are further evaluated and discussed.

• Steel and Composite Structures
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• v.44 no.6
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• pp.789-801
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• 2022

In order to study the influence of loading angles on seismic performance of steel reinforced concrete (SRC) special-shaped columns, cyclic loading tests and finite element analysis (FEA) were both carried out. Seven SRC special-shaped columns, including two L-shaped columns, three T-shaped columns and two cross-shaped columns, were tested, and the failure patterns of the columns with different loading angles were obtained. Based on the tests, the FEA models of SRC special-shaped columns with different loading angles were established. According to the simulation results, hysteretic curves and seismic performance indexes, including bearing capacity, ductility, stiffness and energy dissipation capacity, were analyzed in detail. The results showed that the failure patterns were different for the columns with the same section and different loading angles. With the increasing of loading angles, the hysteretic curves became fuller and the bearing capacity and initial stiffness appeared increasing tendency, but the energy dissipation capacity changed insignificantly. When the loading angle changed, the ductility got better with the larger area of steel at the failure side for the unsymmetrical section and near the neutral axis for the symmetrical section, respectively.

• Steel and Composite Structures
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• v.44 no.4
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• pp.587-602
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• 2022

In this study, the classical J₂ flow theory is explicitly proved to be inappropriate to describe the plastic behaviour of structural steels under different stress states according to the reported test results. A numerical framework of the characterization of the strain hardening and ductile fracture initiation involving the effect of stress states, i.e., stress triaxiality and Lode angle parameter, is proposed based on the mechanical response of structural steels under monotonic loading. Both effects on strain hardening are determined by correction functions, which are implemented as different modules in the numerical framework. Thus, other users can easily modify them according to their test results. Besides, the ductile fracture initiation is determined by a fracture locus in the space of stress triaxiality, Lode angle parameter, and fracture strain. The numerical implementation of the proposed model and the corresponding code are provided in this paper, which are also available on GitHub. The validity of the numerical procedure is examined through single element tests and the accuracy of the proposed model is verified by existing test results.

• Steel and Composite Structures
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• v.45 no.1
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• pp.119-131
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• 2022

Due to the complexity of the structure and the limits of classical SEA, a combined SEA approach is employed, with angle-dependent SEA in the low- and mid-frequency ranges and advanced SEA (ASEA) considering indirect coupling in the high-frequency range. As an important component of the steel box girder, the dynamic response of an L-junction periodic ribbed plate is calculated first by the combined SEA and validated by the impact hammer test and finite element method (FEM). Results show that the indirect coupling due to the periodicity of stiffened plate is significant at high frequencies and may cause the error to reach 38.4 dB. Hence, the incident bending wave angle cannot be ignored in comparison to classical SEA. The combined SEA is then extended to investigate the vibration properties of the steel box girder. The bending wave transmission study is likewise carried out to gain further physical insight into indirect coupling. By comparison with FEM and classical SEA, this approach yields good accuracy for calculating the dynamic responses of the steel box girder made of periodic ribbed plates in a wide frequency range. Furthermore, the influences of some important parameters are discussed, and suggestions for vibration and noise control are provided.

• Steel and Composite Structures
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• v.44 no.4
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• pp.489-502
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• 2022

The stiffeners, also known as ribs, are utilized to increase the resistance of T-stubs. The author's previous studies showed that stiffeners can increase plastic capacity by an average of 1.71 times. A combined experimental and numerical study was undertaken to examine the effects of the stiffener configuration on the behavior of T-stubs. A total of 20 stiffened T-stubs where the shape and angle of stiffeners were considered as the main parameters were tested under monotonic loading. Rectangular, triangular and AISC types of stiffener were tested under monotonic loading. The experimental results indicated that when the height of the stiffener is equal to or higher than the length of the stiffener, the shape of the stiffener does not have an influence on the behavior. A numerical study using the finite element tool ABAQUS was carried out in order to further investigate the effects of the stiffener shapes. In this case, the height is considered less than the length of the stiffener. Moreover, the shape of the stiffeners was investigated with the different thicknesses of the stiffener. The simulation findings revealed that when the height of the stiffener is less than the length of the stiffener, the shape of the stiffener significantly affects the plastic capacity. Based on the numerical and experimental results, it is recommended to use the triangular shape of the stiffener when height is equal to or higher than the length of the stiffener while it is recommended to utilize the rectangular shape of the stiffener when height is less than the length of the stiffener.

• Steel and Composite Structures
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• v.44 no.4
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• pp.569-586
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• 2022

This study introduces a novel friction damper as a component of a recentering frame connection, to solve the problem of structural repair costs, caused by stiffness deterioration and brittle fracture of the central brace frame (CBF). The proposed damper consists of shape memory alloy (SMA) bars with pretension applied to them to improve the stability. SMAs reduce the residual displacement by virtue of the properties of the materials themselves; in addition, a pretension can be applied to partially improve their energy dissipation capacity. The damper also consists of a friction device equipped with friction bolts for increased energy dissipation. Therefore, a study was conducted on the effects of the friction device as well as the pretension forces on the friction damper. For performance verification, 12 cases were studied and analyzed using ABAQUS program. In addition, the friction and pretension forces were used as variables in each case, and the results were compared. As a result, when the pretension and friction force are increased, the energy dissipation capacity gradually increases by up to about 94% and the recentering capacity decreases by up to about 55%. Therefore, it has been shown that SMA bars with adequate pretension in combination with bolts with adequate frictional force effectively reduce residual deformation and increase damper capacity. Thus, this study has successfully proposed a novel friction damper with excellent performance in terms of recentering and energy dissipation capacity.

• Steel and Composite Structures
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• v.44 no.4
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• pp.519-529
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• 2022

Sandwich structures with the superior mechanical properties such as high stiffness and strength-to-weight ratio, good thermal insulation, and high energy absorption capacity are used today in aerospace, automotive, marine, and civil engineering industries. These structures are composed of moderately stiff, thin face sheets that withstand the majority of transverse and in-plane loads, separated by a thick, lightweight core that resists shear forces. In this research, the finite element technique is used to simulate a sandwich panel with a truss core under axial compressive stress using ABAQUS software. A review of past experimental studies shows that the bondline between the core and face sheets plays a vital role in the critical failure load. Therefore, this modeling analyzes the damage initiation modes and debonding between face sheet and core by cohesive surface contact with traction-separation model. According to the results obtained from the modeling, it can be observed that the adhesive stiffness has a significant influence on the critical failure load of the specimens. To achieve the full strength of the structure as a continuum, a lower limit is obtained for the adhesive stiffness. By providing this limit stiffness between the core and the panel face sheets, sudden failure of the structure can be prevented.