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The objective of this paper is to study the dynamic impacts of moving light-rail trains on viaduct bridges and the vibrations induced on the surrounding ground. The study is based on theoretical analysis and field experiment. The theoretical study is performed in two stages using a 2D interaction model of "train-bridge" system for obtaining the dynamic loads of moving trains on the bridge piers, and a 2D dynamic model of "pier-foundation-ground" system for analyzing the vibration responses of the surrounding ground. In the field experiment, the dynamic responses of bridge piers and the ground accelerations are measured at different distances under different train speeds.

The paper is concerned with a new buckling problem of columns subjected to a central force produced by the tension of a string. The central force can be characterized by having a movable center fixed on the deformed axis of a column at its intermediate position. Equilibrium equations of the column, together with the boundary conditions and the conditions of continuity, lead to the characteristic determinant. The characteristic determinant yields the buckling load, and then the buckling mode. If the intermediate center is set at the midspan of the column, the characteristic equation yields a double root. The double root makes buckling mode indeterminate. This fact is an interesting aspect of the present buckling problem. The imperfection method is applied to discuss a possible buckling mode. Experiment of the column was conducted to check the theoretical prediction. The theoretical buckling load and the corresponding buckling modes are compared with the experimental results to find a good agreement between the theory and the experiment.

In the Great Hanshin–Awaji earthquake of 1995, the phenomena of repetitive inelastic buckling were observed in many steel girders including horizontal girders of portal steel piers on elevated highways. The authors have been interested in the ability of steel girders to dissipate the hysteretic plastic strain energy due to such repetitive buckling of steel girders for earthquake-resistance design. This paper is focused on the repetitive buckling behavior of eight steel plate girders under inelastic shear or the combined shear and bending due to a concentrated point load adopting two independent cyclic loading patterns. The model girders were selected considering the combined variations of flange thickness, flange width and depth-to-thickness ratio of the web. Good correlations were found between the results of tests and finite element analyses using shell elements considering the material and geometrical nonlinearities in the repetitive inelastic buckling behavior of plate girders.

This paper deals with the geometrical nonlinear analyses of buckled columns. Differential equations governing the elasticas of buckled columns are derived, in which both the effects of taper type and shear deformation are included. Three kinds of taper types are considered, i.e. breadth, depth and square tapers. Differential equations are solved numerically to obtain the deflection of elasticas and the buckling loads of such columns. Both clamped ends and hinged ends are considered. The effects of shear deformation on the deflection of elasticas of buckled columns and on the buckling loads of columns are investigated extensively. The buckling load equations for uniform columns are expressed as a function of the implicit shear effect. Experimental studies are presented that complement the theoretical results of nonlinear responses of the elasticas.

Earthquake causes wide and severe damage to building structures, due to not just the great ground motion but also secondary actions, such as impact, blast or fire, occurring after earthquake. The extreme combined loading scenario should be considered for safety of buildings and lives. Taking fire for example, the combined load can be considered as an event in which the structures are first partially damaged under an earthquake and then attacked by fire. In order to investigate the post-earthquake loading scenario, it is important to assess the partial damage caused by earthquake on different components of structures. The behavior of welded steel I-beam to hollow square tubular columns is investigated herein. A detailed experimental study is presented in which two groups of unstiffened welded steel connections, with the same configurations, subjected to static and cyclic loading are considered. The flexibility and strength of the connections are measured, while the damage phenomena and failure modes are explored during the tests. The connection damage is found to be a cumulative fracture developing process which leads to significant gradual degradation of the mechanical properties of the connection. The quantificational evaluations of the cyclic loading induced damage are also carried out to investigate the connection damage level according to different loading intensities. A finite element modeling numerical study is also carried out to validate the experimental results and a good agreement is achieved. The test results and FE modeling provide a benchmark data for the unstiffened welded connections and can be used for further investigations of the connections subjected to combined actions such as post-earthquake fire.

The wavelet transform and Lipschitz exponent perform well in detecting signal singularity. With the bridge crack damage modeled as rotational springs based on fracture mechanics, the deflection time history of the beam under the moving load is determined with a numerical method. The continuous wavelet transformation (CWT) is applied to the deflection of the beam to identify the location of the damage, and the Lipschitz exponent is used to evaluate the damage degree. The influence of different damage degrees, multiple damage, different sensor locations, load velocity and load magnitude are studied. Besides, the feasibility of this method is verified by a model experiment.

The vibration of a four-span continuous plate with two rails on top and four extra elastic supports excited by a moving model car is studied through numerical simulations and experiments. Modal testing is carried out to identify the Young’s moduli of the plate material and the rail material. Shell elements and beam elements are adopted for the plate and the rails of their Finite Element (FE) model, respectively. An offset is required to connect the rails and the plate in the FE model and the offset ratio of the shell element is updated to bring the numerical frequencies of the structure (plate with rails) closest to its experimental frequencies. Modal Superposition (MS) method with numerical modes of the structure and an iterative method are combined to predict the vibration of the structure subjected to the moving car. The displacements of four points of the plate are measured during the crossing of the car and compared with predicted results. The two sets of results agree well, which validates the model of the system. Parametric analysis is then made using the validated system model.

The research reported herein follows the increased interest in buckling-induced functionality for novel materials and devices with a focus on cylindrical shells as a suitable structural prototype. The paper proposes the concept of using patterned thickening patches on the surface of cylindrical shells to modify and control their elastic postbuckling response. Cylindrical shells with non-uniform thickness distributions (NTD) were fabricated through 3D printing to understand rules for pattern designs and then tested under loading-unloading cycles. Strategic thickening patches act as governing imperfections that modify the response type, the number, the location and the sequence of the localized buckling events. The use of patterned thickening patches and their layout provides diverse design opportunities for a desired elastic postbuckling response and can be potentially used in design materials and structures with switchable functionalities.

In this paper, first a complete buckling experiment of the sandwich beams with the foam core is carried out, which includes the manufacturing of specimens and their experimental verification. Second, a refined sinusoidal zig-zag theory (RSZT) is established, which can describe the zig-zag effect during the in-plane compression of sandwich beam and accommodate the transverse shear free surface boundary conditions. Based on the established model combined with Hu–Washizu variational principle, a two-node beam element has been developed to address the buckling problem of the sandwich beams. Thus, the established beam element is able to accommodate interlaminar continuous conditions of transverse shear stress. Several examples have been investigated to validate the accuracy of the established method. The comparative analysis of the results including experimental data, the results acquired from three-dimensional finite element (3D-FEM) and diverse models has been made. Comparative analysis shows that the accurate buckling loads can be acquired from the established model. Nevertheless, other models discarding the continuous conditions of transverse stresses among the adjacent layers largely overestimate the critical loads.

This paper examines the differences in hysteretic behavior of buckling-restrained brace subsystem frames (BRBFs) with concentric and out-of-plane eccentric configurations. First, a quasi-static experiment was carried out on steel plate BRBF specimens to study the differences in mechanical properties, stability, and energy dissipation capacity between BRBFs with concentric and out-of-plane eccentric configurations. Second, a numerical simulation was carried out using the same steel plate BRBF specimens to study the difference in the stress distribution and high-order deformation patterns between the BRBFs with concentric and out-of-plane eccentric configurations. The test and numerical results showed that the out-of-plane eccentric BRBFs under in-plane quasi-static loads have different mechanical properties, larger compression strength adjustment factors ($\beta$) under larger loading amplitudes, higher $\beta$ value increasing rates, lower equivalent viscous damping ratios ($\zeta$), different yield processes, and different generation processes of high-order core deformation compared with the concentric BRBFs.

In recent decades, carbon fiber, glass fiber, polyester and Kevlar fiber have been utilized to replace the steel shims in conventional steel-reinforced elastomeric isolators (SREIs). This study chose nylon fabrics owing to their extreme low cost, low elastic modulus and good adhesion to rubber, and nine nylon fabric-reinforced elastomeric isolators (N-FREIs) were manufactured with different design parameters. Compression and compression shear tests were, respectively, conducted to investigate the mechanical properties together with their influential factors of the N-FREIs. Results show that the vertical load-carrying capacity of the isolator is high enough to sustain a compressive stress of 10MPa without visible damage. The compressive stiffness of N-FREI is much smaller than that of SREI, and the vertical damping ratio under cyclic compression reaches up to 7%. In the compression shear tests, the shear stiffness of the isolator first decreases and then increases as the shear strain increases within 300%, and the equivalent damping ratio varies between 9% and 14% for different sizes of the isolator. Additionally, due to the flexibility and extensibility of the low modulus nylon fabric, both vertical and horizontal stiffness decrease a bit with an increase in the number of fabric layers. Finally, a formula for calculating the horizontal stiffness of N-FREI is proposed, it provides a comprehensive mathematical model to predict the behavior of the N-FREI under horizontal shear conditions.