• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.64-71
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• 2014

The generalized tangential stiffness matrix of semi-rigid frame element with shear deformations based on Haringx's shear theory is newly derived and compared with the previous study based on Engesser's shear theory. Also, linearized elastic and geometric stiffness matrices are newly presented from the exact tangential stiffness matrix. In oder to obtain the inelastic system buckling load of shear flexible semi-rigid frame structure, the Ef method by tangential modulus theory is adopted and the FE analysis programs are developed. Finally, the shear and semi-rigid effects of system bucking are investigated by two numerical examples.

• Steel and Composite Structures
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• v.47 no.2
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• pp.185-201
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• 2023

Despite the high lateral stiffness and strength of the Concentrically Braced Frame (CBF), due to the buckling of its diagonal members, it is not a suitable system in high seismic regions. Among the offered methods to overcome the shortcoming, utilizing a metallic damper is considered as an appropriate idea to enhance the behavior of Concentrically Braced Frames (CBFs). Therefore, in this paper, an innovative steel damper is proposed, which is investigated experimentally and numerically. Moreover, a parametrical study was carried out to evaluate the effect of the mechanism (shear, shear-flexural, and flexural) considering buckling mode (elastic, inelastic, and plastic) on the behavior of the damper. Besides, the necessary formulas based on the parametrical study were presented to predict the behavior of the damper that they showed good agreement with finite element (FE) results. Both experimental and numerical results confirmed that dampers with the shear mechanism in all buckling modes have a better performance than other dampers. Accordingly, the FE results indicated that the shear damper has greater ultimate strength than the flexural damper by 32%, 31%, and 56%, respectively, for plates with elastic, inelastic, and plastic buckling modes. Also, the shear damper has a greater stiffness than the flexural damper by 43%, 26%, and 53%, respectively, for dampers with elastic, inelastic, and plastic buckling modes.

• Steel and Composite Structures
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• v.5 no.4
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• pp.305-326
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• 2005

The inelastic buckling behaviour of continuously restrained two and three-span continuous beams subjected to concentrated loads and uniformly distributed loads are studied in this paper. The restraint type considered in this paper is fully restrained against translation and elastic twist applied at the top flange. These types of restraints are most likely experienced in industrial structures, for example steel-concrete composite beams and half through girders. The buckling analysis of continuous beam consists of two parts, firstly the moment and shear distribution along the member are determined by employing force method and the information is then used for an out-of-plane buckling analysis. The finite element method is incorporated with so-called simplified and the polynomial pattern of residual stress. Owing to the inelastic response of the steel, both the in-plane and out-of-plane analysis, which is treated as being uncoupled, extend into the nonlinear range. This paper presents the results of inelastic lateral-torsional and lateral-distortional buckling load and finally conclusions are drawn regarding the web distortion.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.497-505
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• 2008

Corrugated steel webs resist only shear force because of the accordion effects. The shear force in the web can cause three different buckling mode: local, global, and interactive shear buckling modes. The shear behavior of the corrugated steel webs have been investigated by several researchers. However, shear buckling behavior of the corrugated webs are not clearly explained yet. And, it lead the conservative design. This paper presents shear strength of trapezoidally corrugated steel webs. A series of the tests were also conducted to verified proposed shear strength. Firstly, local, global, and interactive shear buckling equations provided by previous researchers were rearranged as a simple form considering the profiles of the existing bridges with corrugated steel webs. And, global and interactive shear buckling coefficient, and shear buckling parameter for corrugated webs were suggested in this study. Inelastic buckling strength can be determined from buckling curves based on the proposed shear buckling parameter. From the test results of this study and those of previous researchers, it can be found that suggested shear strength provides good estimation of those of trapezoidally corrugated steel webs.

• International journal of steel structures
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• v.18 no.4
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• pp.1440-1463
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• 2018

The Wagner coefficient is a key parameter used to describe the inelastic lateral-torsional buckling (LTB) behaviour of the I-beam, since even for a doubly-symmetric I-section with residual stress, it becomes a monosymmetric I-section due to the characteristics of the non-symmetrical distribution of plastic regions. However, so far no theoretical derivation on the energy equation and Wagner's coefficient have been presented due to the limitation of Vlasov's buckling theory. In order to simplify the nonlinear analysis and calculation, this paper presents a simplified mechanical model and an analytical solution for doubly-symmetric I-beams under pure bending, in which residual stresses and yielding are taken into account. According to the plate-beam theory proposed by the lead author, the energy equation for the inelastic LTB of an I-beam is derived in detail, using only the Euler-Bernoulli beam model and the Kirchhoff-plate model. In this derivation, the concept of the instantaneous shear centre is used and its position can be determined naturally by the condition that the coefficient of the cross-term in the strain energy should be zero; formulae for both the critical moment and the corresponding critical beam length are proposed based upon the analytical buckling equation. An analytical formula of the Wagner coefficient is obtained and the validity of Wagner hypothesis is reconfirmed. Finally, the accuracy of the analytical solution is verified by a FEM solution based upon a bi-modulus model of I-beams. It is found that the critical moments given by the analytical solution almost is identical to those given by Trahair's formulae, and hence the analytical solution can be used as a benchmark to verify the results obtained by other numerical algorithms for inelastic LTB behaviour.

• Steel and Composite Structures
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• v.6 no.1
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• pp.1-14
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• 2006

Experiments have been carried out on six composite and two plain steel plate girders under shear loading to understand the elastic and inelastic behaviour of such girders. The failure mechanism assumed and used to develop design equations is normally based on the failure patterns observed in the experiments. Therefore, different types of cracks and failure patterns observed in the experiments are reviewed briefly first. Based on the observed failure patterns, a design method to predict the ultimate shear capacity of composite plate girders is proposed in this paper. The values of ultimate shear capacity obtained using the proposed design method are compared with the corresponding experimental values and it is found that the proposed method is able to predict the shear capacity accurately.

• Steel and Composite Structures
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• v.8 no.2
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• pp.159-178
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• 2008

An analytical procedure is presented for the determination of the buckling load and the buckling temperature of a straight, slender, geometrically perfect, axially loaded, translationally and rotationally restrained steel column exposed to fire. The exact kinematical equations of the column are considered, but the shear strain is neglected. The linearized stability theory is employed in the buckling analysis. Behaviour of steel at the elevated temperature is assumed in accordance with the European standard EC 3. Theoretical findings are applied in the parametric analysis of restrained columns. It is found that the buckling length factor decreases with temperature and depends both on the material model and stiffnesses of rotational and translational restraints. This is in disagreement with the buckling length for intermediate storeys of braced frames proposed by EC 3, where it is assumed to be temperature independent. The present analysis indicates that this is a reasonable approximation only for rather stiff rotational springs.

• Earthquakes and Structures
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• v.12 no.4
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• pp.469-478
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• 2017

This paper summarizes estimated seismic response results from three-dimensional nonlinear inelastic time-history analyses of some steel buckling-restrained braced (BRB) structures taking into account soil-structure interaction (SSI). The response results involve mean values for peak interstorey drift ratios, peak interstorey residual drift ratios and peak floor accelerations. Moreover, mean seismic demands in terms of axial force and rotation in columns, of axial and shear forces and bending moment in BRB beams and of axial displacement in BRBs are also discussed. For comparison purposes, three separate configurations of the BRBs have been considered and the aforementioned seismic response and demands results have been obtained firstly by considering SSI effects and then by neglecting them. It is concluded that SSI, when considered, may lead to larger interstorey and residual interstorey drifts than when not. These drifts did not cause failure of columns and of the BRBs. However, the BRB beam may fail due to flexure.

• Steel and Composite Structures
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• v.47 no.1
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• pp.103-117
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• 2023

This paper presents an investigation on the shear resistance of corrugated web steel beams (CWBs) with a circular web opening. A total of five specimens with different diameters of web openings were designed and tested with vertical load applied on the top flange at mid-span. The ultimate strengths, failure modes, and load versus middle displacement curves were obtained from the tests. Following the tests, numerical models of the CWBs were developed and validated against the test results. The influence of the web plate thickness, steel grade, opening diameter, and location on the shear strength of the CWBs was extensively investigated. An XGBoost machine learning model for shear resistance prediction was trained based on 256 CWB samples. The XGBoost model with optimal hyperparameters showed excellent accuracy and exceeded the accuracy of the available design equations. The effects of geometric parameters and material properties on the shear resistance were evaluated using the SHAP method.

• Journal of Korean Association for Spatial Structures
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• v.19 no.4
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• pp.45-52
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• 2019

The purpose of the paper is to introduce a system that reduces the occurrence of weak-story in the event of earthquake. Weak-story concentrates deformation on the story and causes all member to collapse before the capacity of all member is reached. This paper introduces Strong-Back system (SB) to protect weak story. SB is a hybrid of zipper frame, tied eccentrically braced frame, and elastic truss system and it is divided into elastic and inelastic areas. Elastic areas prevent the generation of weak story by distributing energy, and inelastic areas dissipate energy through buckling or yielding. In this paper, the seismic performance is evaluated by comparing the four type braced frame with SB through push-over analysis. The four criteria are compared from the base shear, the ductility capacity, the column failure order, and the quantity of brace. As a result, SB proved to have sufficient performance to protect the weak-story.