International Journal of Structural Stability and Dynamics

The vehicle–bridge interaction (VBI) is studied using a semi-analytical approach based on a three-mass vehicle model. As most work analyzes vehicle–bridge interaction numerically and/or analytically by treating the vehicle as a simplified lumped mass, to the best of the author’s knowledge, this work first presents the theoretical formulation of the three-mass VBI system, where a more realistic vehicle model equipped with a rigid mass and two unsprung mass-spring-damper systems is considered. By assuming the first modal vibration of beam, the semi-analytical solutions are derived, which can be served as the reference solutions for calibrating VBI analyses using different models or methods.

In this research, nonlinear thermal buckling and post-buckling behaviors of composite plate with the circular/elliptical cut-out are investigated using particle semi-energy (PSE) method. The semi-energy method is based on the solution of compatibility equation via an Airy force function and out-of-plane displacement function. The unknown parameters of these functions are determined by minimizing the potential energy. The integral of potential energy are replaced with summation of particles energy at perforated plate. The cut-out is modeled easily using these particles. The advantages of this method are easily cut-out modeling by particles and proposing just one of the displacement fields (i.e. out-of-plane). Based on the results, there is a good agreement (1.25%) between the post-buckling loads derived from PSE of this paper and experimental test of other literature. The accuracy of the finite element method (FEM) is 7.5% with respect to experimental test. The influences of temperature distribution, the cut-out size and elliptical cut-out rotating on post-buckling load and deflection of perforated plate are investigated.

A layered rock mass is a special type of geological body. The existence of a bedding surface may lead to a poor cutting effect (over/under-excavation of the surrounding rock), falling of blocks, or collapse, thereby affecting most constructions in areas with such rocks. Given the lack of a proper quantitative analysis method for surrounding rock damages, the construction process of layered surrounding rock tunnels becomes difficult. To address these problems, three types of cut blasting models with single, double, and four holes are studied in this paper. With this, the LS-DYNA program is used to analyze the behaviors of stress wave propagation, crack propagation, and fracture modes, as well as fracture mechanisms of mudstone, sandstone, and layered rock. Using the image processing technology and fractal theory, the fractal dimension change trend and progressive damage evolution behavior of the three types of rocks under different cut blasting conditions are determined. Also determined is the corresponding relationship between the fractal dimension and the rock damage degree. The results indicate that crack initiation, propagation, bifurcation, and fractal dimension evolution are more closely related to the phenomenon where the compression wave is ahead of the tension wave, and the$\setminus$incompatible deformation of the bedding under single-hole blasting. Under double-hole and four-hole blasting, the phenomena, such as spalling, bedding crack penetration, and fracture connection between the explosive holes are caused mainly by the effects of stress concentration, reflected tension waves, and stress wave superposition. Moreover, under different blasting conditions, the rocks exhibit a similar progressive damage process, i.e. a rapid increase at first, then a slow rise, and finally a stabilization phase. The dynamic damage degree of the rock exhibits a linear increasing trend under different blasting holes. The study results provide a useful reference for blasting scheme design and optimization of underground engineering projects.

In this study, the optimum position and minimum diameter of damping wire were investigated to maximize the fundamental frequencies of a rotating blade. The blade was modeled as an isotropic, homogenous and constant cross-sectional cantilever rotating beam. The damping wire was modeled as an intermediate elastic support. In most rotating-beam applications, such as turbine blades, the slenderness ratio is low; therefore, Timoshenko beam theory was selected to analyze the model. The optimal position and minimum stiffness of elastic support were determined to maximize the natural frequencies of the beam using the finite element method. Minimum diameter of the damping wire was calculated by determining the minimum stiffness. Parameter sensitivity analysis showed that the angular velocity of the blade has no remarkable effect on the optimal position and minimum diameter of damping wire.

The Homotopy Perturbation Method (HPM) is applied to investigate the nonlinear free and forced vibration behavior of the rotating cracked beam. Nonlinear governing equations considering the two-dimensional (2D) large flexible structure in a rotating reference frame considering centrifugal forces are obtained by the Lagrangian approach and the Assumed Mode Method (AMM). The crack is modeled as an elastic nonlinear massless rotational spring, which divides the beam into two parts. The Rayleigh–Ritz method is used to discretize the governing system of equations of the motion. Stability analysis along with bifurcation and phase portrait represents the different behavior of the system, depending on the variations of base angular velocity, crack location, and stiffness. Moreover, it is shown that as the rotational speed increases, a tensile force appears along the neutral axis, stiffening the cracked structure, which results in shifting the backbone to the right and highly affects the nonlinear features of the system. The results obtained through a comparative study of the HPM with first-order approximation and numerical simulations (Runge–Kutta algorithm) demonstrate an accurate and effective solution for structures with nonlinear dynamics.

The seismic isolation efficiency of different friction-based devices needs verification by shaking table test, but faces problems in scaling before the test due to their frictional nonlinearity. To solve the scaling problems, a simplified civil structure, isolated by a self-centering spring-friction device, was numerically scaled in different ways considering the effect of friction action. The seismic responses of the scaled models were scaled back to those of the prototype and compared with the seismic responses of the prototype. The scaling problems and solutions were validated by a shaking table test on simply supported bridges using friction pendulum bearings (FPBs). The results show that both the unscaled gravity on a shaking table and the unscaled non-uniform friction distribution cause an inaccurate friction force in the structural motion equations of scaled models, and thus causing the scaling errors. One new and valid solution, i.e. changing the friction coefficient and scaling the non-uniform friction distribution to keep an accurate friction force for the scaled models, is put forward to avoid the scaling errors thoroughly. Another new solution shows that an increasing peak ground acceleration (PGA) can increase the other forces, while weakening the ratio of inaccurate friction force in the structural motion equations of the scaled models, which therefore reducing the scaling errors of acceleration and relative displacement responses, but not the scaling errors of residual displacement responses. In addition, the time-varying friction, the interface separation and collision of bearings, and other complex factors are found to cause scaling errors and need further investigation.

Previously, the contact states between the bearing and journal of a spatial revolute joint (SRJ) with both axial and radial clearances were solved in the global coordinate system (GCS), which is complex and requires iterations. In this paper, a local-coordinate representation for the SRJs with clearance is combined with a vector-form particle-element method, i.e. finite particle method (FPM), to provide a more practical means for evaluation of the dynamic effects due to clearance. Firstly, the fundamentals of the FPM for analysis of spatial mechanisms are briefed. Then, a local-coordinate representation based on the revolution axis of the bearing is proposed. Specifically, the geometry of the journal and bearing is explicitly expressed using the coordinate transformation. The axial and radial contact states are evaluated by substituting the parametric equations and transforming them to quadratic and quartic equations, respectively, which can be analytically solved without iterations. The contact forces are evaluated in the local-coordinate representation and then transformed into the GCS representation. Two numerical examples, i.e. a spatial slider-crank mechanism and a spatial double pendulum, are provided to demonstrate the feasibility of the proposed method, by which the effects of joint-joint interaction and joint-flexible component interaction are fully discussed.

To efficiently and accurately evaluate the seismic system reliability analysis (SSRA) of cable-stayed bridges subjected to spatially varying ground motions, a direct probabilistic framework was developed in this paper. First, the relevant methods for the structural seismic reliability were presented, including the multiplicative dimensional reduction method, maximum entropy method with fractional moments (FMs), and the product of conditional marginals (PCMs). Second, based on the OpenSees platform, the 3D finite element model of the cable-stayed bridge was established, along with the uncertain structural parameters, stochastic ground motions, and failure modes of each structural component under earthquake loading summarized. Third, considering the double uncertainties of the bridge and ground motions, the nonlinear time history analysis was conducted for the bridge under various scenarios. Finally, the nonlinear seismic response and fractional moment of the structural response were obtained. The maximum entropy method with FMswas used to get the probability density function (pdf) of the structural response, together with the failure probability and reliability index of each component. Considering the correlation between components, the PCMs was used to obtain the failure probability of the bridge under earthquake loadings, and some critical conclusions were drawn.

In this paper, some of the displacement-based plate theories are used to investigate the elastic-plastic analysis of plates in the framework of the finite element method including the buckling and postbuckling effects with the focus on the general third-order plate theory (GTPT). The plate calculation results were compared with the results obtained using 64-nodes solid elements involving Lobatto integration scheme. The problem is solved using the Newton–Raphson method applying modified Crisfield constant arc-length procedure. The results show good agreement of results and the GTPT can be acknowledged to fulfill essential criteria for application to the elastic-plastic analysis of thin and thick plates.

Acoustic insulation optimization of the ship decks to contain impact noise is generally obtained by adopting suitable types of viscoelastic resilient materials. For this purpose, it is necessary to be able to make a correct choice of material. This is obtained by experimentally identifying the vibro-acoustic behavior of the combined semi-reverberant room and floor system according to an ISO standard (ISO 16283-2). These tests are generally onerous as they require the availability of the floor with both trimmed and untrimmed configurations. In addition, qualified technicians are needed to correctly spread the material on the floor. Finally, after the test has ended, the material must be removed and disposed of properly. To reduce this wasted time and cost, in this paper, a new methodology is proposed that predicts the vibro-acoustic behavior of the floor and viscoelastic material assembled together starting from separate dynamic information of the two components. Once these two elements are properly experimentally identified, the proposed method foresees the vibro-acoustic response of the overall system in presence of an impact footfall excitation.

The paper presents a modified differential quadrature (MDQ) method to investigate the dynamic response of perforated plates with elastically restrained edges under uniaxial impact compressive load. The perforated plate is divided into several separate plate elements that can be connected by using penalty function method (PFM) to ensure continuity along the shared edges. The in-plane stress distribution of the plate under the mechanical edge loading is determined by the pre-buckling analysis. To analyze the effect of elastically restrained edges on the dynamic response of perforated plates, artificial springs imposed for the edges are considered in the governing equilibrium equations. Verification analysis is carried out to demonstrate the efficiency and accuracy of the proposed method by comparing the results obtained with those available in the literature. Finally, the various effects of initial imperfection, rotational restrained stiffness, hole size and location, and shear load, on the dynamic response of perforated plates are investigated. The results show that the dynamic buckling load of perforated plates is significantly influenced by the rotational restraint stiffness, hole size and shear load as well as the initial geometric imperfection, whereas the effect of hole location can be neglected in the analysis of dynamic buckling of plates. Additionally, the results predicted by the proposed method can correlate well with the available numerical results.

Shape memory alloy (SMA) dampers are widely investigated passive control systems for structural vibration mitigation. However, the damping robustness of conventional austenite SMA dampers may be affected by environmental temperature. In this study, an innovative double SMA damper (DSD) system is presented to improve the temperature robustness of the SMA dampers. In the proposed system, double SMA hysteretic elements with different phase transition temperatures are arranged in parallel, where the SMA element with lower transition temperature behaves as austenite under room temperature, and the other with higher transition temperature behaves as martensite. To study the vibration control effect, both single-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) structures with DSD systems are employed. The thermal and mechanical behaviors of the SMA elements and the working principle of DSD are also introduced. Thereon, the equivalent linearization method for SMA’s output force and the motion-governing equations for SDOF structure with DSD are derived. Moreover, parametric studies are conducted to investigate the performance of the proposed DSD system in both frequency and time domains. Also, numerical analysis for the MDOF structure with DSD systems is carried out to illustrate the trend in response reduction with an increasing number of degrees of freedom. The analytical results show that the DSD can mitigate the structural seismic response more effectively than the conventional one with acceptable residual deformation, and is capable of delaying the degradation of SMA’s energy dissipation capacity. Less SMA material is required for the proposed DSD to fulfill the same mitigation requirement, and it is suitable for general applications for temperature robustness.

In this paper, a high-order cylindrical beam model, where the shear deformation is taken into account, will be used to analyze the buckling behaviors of the functionally graded cylindrical beams with radially and axially varying material inhomogeneities. The coupled governing equations for buckling of a cylindrical beam under axial compression are derived, which can be translated into a single differential equation by introducing an auxiliary function. The shifted Chebyshev polynomials are used to compute the critical buckling loads for kinds of boundary conditions. By comparing with the three-dimensional solutions for buckling of homogeneous circular beams, the validity of the introduced model is confirmed. Two typical material property distributions defined by the exponential- and power-law are considered. A parametric study is carried out to investigate the effects of material gradient indexes on the critical buckling loads.

This paper proposes a novel optimization algorithm called modal force information-based optimization (MFIBO) to identify the location and severity of damage in structures. The main idea behind the MFIBO is to take advantage of information captured from the modal force of structural elements to seek the optimum damage variables. The modal element force, defined as the internal element force caused by the action of mode shapes, allows the MFIBO to recognize promising directions in the search space and assists in accelerating the optimization process. Indeed, unlike meta-heuristic optimization algorithms, which disregard explicit information about the problem and rely only upon time-consuming stochastic search computations, the MFIBO employs an informed search strategy to perform optimization in a rational and directed manner. In order to assess the effectiveness and applicability of the proposed MFIBO algorithm, four benchmark damage identification examples of truss and frame structures are conducted under both noise-free and noisy conditions. In each example, the results of the MFIBO are also compared with those attained by two well-known meta-heuristic algorithms, namely the differential evolution and the teaching–learning-based optimization. The obtained results reveal that the MFIBO is able to accurately and reliably identify structural damage with a significantly lower computational burden compared to the meta-heuristic algorithms.

A time–frequency random approach is proposed in this paper for the prediction of subway train-induced tunnel and ground vibrations. This is a development of the random approach previously proposed by the authors, which takes the discrete track support, singular track defects, etc., into consideration. The proposed approach is developed using a two-step method. First, the pseudo-excitation method (PEM) and the two-dimensional multibody system/finite element method model are effectively combined to derive the track–tunnel pseudo-interaction forces by employing the power spectral density of track irregularity. Second, the random vibrations of the tunnel–soil system are obtained via the PEM in the wavenumber–frequency domain. To improve the computational efficiency, a fast-computing strategy is proposed based on the multipoint synchronous algorithm. Using numerical examples, the proposed time–frequency hybrid modeling process is verified by comparing it with the fully coupled time-dependent three-dimensional approach. Furthermore, the influence of the discrete track support on the random vibrations of the tunnel and ground is discussed by comparing the results predicted by the proposed approach with those predicted by the previously developed approach.

The purpose of this study is to investigate the nonlinear torsional flutter of a long-span suspension bridge with a double-deck truss girder. First, the characteristics of nonlinear flutter are studied using the section model in the wind tunnel test. Different aerodynamic measures, e.g. upper and lower stabilizers and horizontal flaps, are applied to improve the flutter performance of the double-deck truss girder. Then, the full bridge aeroelastic model is tested in the wind tunnel to further examine the flutter performance of the bridge with the optimal truss girder. Finally, three-dimensional (3D) flutter analysis is performed to study the static wind-induced effects on the nonlinear flutter of the long-span suspension bridge. The results show that single-degree-of-freedom torsional limit cycle oscillations occur at large amplitudes for the double-deck truss section at the attack angles of $0^{\circ }$ and $+3^{\circ }$. The upper and lower stabilizers installed on the upper and lower decks, respectively, and the flaps installed near the bottoms of the sidewalks can all effectively alleviate the torsional flutter responses. Meanwhile, it is found that the torsional flutter responses of the truss girder in the aeroelastic model test are much smaller than those in the section model test. The 3D flutter analysis demonstrates that the large discrepancies between the flutter responses of the two model experiments can be attributed to the additional attack angle caused by the static wind-induced displacements. This finding highlights the importance and necessity of considering the static wind-induced effects in the flutter design of long-span suspension bridges.