International Journal of Structural Stability and Dynamics

In regions of low to moderate seismicity, serviceability limits states such as inter-story drift under wind load govern the design of the lateral load resisting structural systems of high rise buildings. The key objective in this regard is to provide adequate lateral stiffness to control lateral deflections and inter-story drifts. Current design practice assumes that the structural system alone provides lateral resistance against wind, the dominant load considered for countries like Australia. The contribution of nonstructural components (NSCs) such as interior partition walls on lateral stiffness is generally disregarded in the analysis of the buildings, even though it is commonly acknowledged that the NSCs play a significant role on the lateral stiffness of buildings. This technical note presents the results of a parametric study on the effects of NSCs, in particular, the effects of masonry interior partition walls on the fundamental period of buildings. The parameters considered in this study include: the number and length of walls, their material properties, the number of parallel moment resisting frames and the height of buildings. The results of this study indicate that interior walls can have significant effects on the lateral stiffness of buildings.

Ice loads exerted on the transmission line can increase the probability of conductor breaking, which will lead to the stability failure of transmission towers. In this paper, a transmission tower-line system is established for two towers and three span lines. Then the nonlinear static stability analysis and nonlinear dynamic stability analysis induced by the conductor breaking are carried out to obtain the load versus displacement curves, while studying the failure modes of the transmission tower-line system. Moreover, the ice load and initial eccentricity are considered in the numerical simulation. In addition, a parametric analysis is performed to investigate the influence of span, insulator length and initial tension force on the stability failure of the system. The results show that the dynamic instability will occur earlier than the static instability due to the dynamic impact effect and conductor breaking with ice loads can lead to the progressive collapse of the transmission tower-line system. Finally, the span length has the greatest effect on the response of transmission tower caused by conductor breaking.

The probability density evolution method (PDEM) provides a feasible approach for the dynamic response analysis of nonlinear stochastic structures. The key step in this regard is to solve a generalized density evolution equation (GDEE) in order to establish the probability density function (PDF). Previously, a finite difference method (FDM) has often been resorted to solve the GDEE. However, one may encounter the problem of mesh sensitivity in the application of FDM to the PDEM. To this end, a novel difference-wavelet method that can improve the finite difference result by means of a nonlinear wavelet density estimation method is proposed in the present paper. By exploiting the multi-resolution property of wavelet functions and by choosing the optimal scale at each instant, it is expected that the bothering mesh sensitivity issue in finite difference method can be overcome to some extent and a better probability density result can be obtained. In order to verify the proposed method, a single-degree-of-freedom (SDOF) oscillator and an 8-story frame structure are investigated in detail. The results show the notable superiority of the proposed method to finite difference method.

The suppression of oscillations of an elastically mounted prism under galloping by a dynamic vibration absorber (DVA) with linear damping and stiffness is investigated. A model considering the dynamic coupling of the prism and the DVA is constructed, with the aerodynamic loads acting on the system represented by a quasi-steady approximation. Based on the coupled nonlinear governing equations of motion, a linear analysis is first conducted to explore the coupled frequency and damping, and the onset speed of galloping in the presence of the DVA. Subsequently, the normal form of the Hopf bifurcation for the coupled system near the onset of galloping is derived to characterize the type of instability (supercritical or subcritical), while evaluating the effects of the DVA parameters. The results show that with appropriate parametric values, the DVA has great impact on the onset speed of galloping and can significantly alleviate the oscillation amplitude of the prism.

A 3D finite-element model for the dynamic analysis of soil–pile–slab is presented, with the soil–pile–mattress–slab interaction included in studying the dynamic behavior of the rigid–pile–reinforced soils. The soil, piles, and mattress are represented as continuum solids, and the slab is represented by structural plate elements. Quiet boundaries are placed at the boundaries of the model to avoid wave reflection. The formulation is based on the sub-structure method. Different geometric configurations are studied in terms of dynamic impedance. The numerical results are presented to show the influence of the mattress stiffness and the pile–soil contact conditions on the dynamic response of the foundation system. The horizontal and vertical impedances of the pile foundations are presented with the results compared with those available in previous studies.

This paper introduces a novel formulation for the free rocking motion of a rigid block supported on a rigid plane. The equation of the motion between two subsequent impacts is expressed as a uniformly accelerated motion only depending on the assigned initial velocity. The constant acceleration is derived by an ad hoc approximation in order to fit the results of the standard model of Housner [B. Seismol. Soc. Am, 53(2) (1963) 403–417], which is herein revisited and explored. An extensive comparison between the standard and the proposed models is carried out in terms of moment-rotation relationship, critical rotational velocity, normalized amplitude and duration of the half-cycles.

An accurate evaluation of the dynamic responses on critical components of orthotropic bridge decks is of significance for identifying structural damage and predicting the fatigue life of long-span cable-stayed bridges. However, the traditional finite element (FE) methods are computationally cost-prohibitive for this application. In response, a new multiscale time-varying analysis method based on the dynamic balance equations and FE strategies is proposed and derived theoretically in this paper. Unlike most existing methods, the dynamic responses of this refined model is easily solved through repeated iterations, using the dynamic responses of a large-scale model as the boundary conditions. To validate the effectiveness of the method, a simply supported steel plate beam was used in a field test that demonstrated good correlation between the analytical dynamic responses and the experimental ones. To further validate this method, a case study involving a whole segment model of the Pingtan Bridge orthotropic bridge deck was established and the complex junction area between the plate and longitudinal ribs was modeled using two refinement processes. For comparison, a sufficiently refined model was also developed using ANSYS software based on the traditional FE methods. This study attempted to provide a new high-efficiency analysis framework for accurate analysis of local vibration problems. Under relatively small and easily manageable calculation conditions at each cross-scale processing level, the proposed method meets not only the requirements of global design for actual engineering applications, but also supports further in depth analysis.

The wavelength characteristic is a useful clue for locating and assessing the severity of slope discontinuity in beams. In this study, the slope discontinuity of a beam is represented by an internal hinge restrained by elastic springs, and the wavelength of the beam is calculated indirectly from the vertical response of a test vehicle during its travel over the beam. The key parameters of the problem at hand are first unveiled using an approximate, closed-form solution for the response of the vehicle moving at low speeds over the bridge. Then a two-beam element model with slope discontinuity is formulated for the vehicle–bridge interaction (VBI) system for use in numerical simulation. In the examples, the wavenumber-based response of the test vehicle is used to identify the location and severity of the discontinuity in the beam. It is demonstrated that the wavelength-based technique presented herein by using the moving test vehicle as a moving sensor system offers a promising, alternative approach for damage detection in girder type bridges.

This paper describes a case-study where the human-induced vibrations of a footbridge have been controlled by means of the modification of its natural frequencies. The structure, a Nielsen variable depth truss, is located over a highway on the outskirts of Malaga (Spain), so that it was designed to withstand low pedestrian densities and its dynamic behavior was just analyzed according to Spanish standards at the date of construction. However, the presence of a nearby sports pavilion originated unexpected large pedestrian flows. This new service condition was not properly anticipated, leading to significant longitudinal vibration levels. To overcome this problem, experimental and numerical studies were carried out, with the aim of finding a low cost solution that yet maintained the footbridge aesthetic appearance. Following these studies, corrective measures that increased its stiffness were then adopted. Subsequently, experimental tests and a finite element model tuning were performed to obtain: (i) its modified modal parameters; and (ii) a more accurate estimation of its dynamic behavior under different pedestrian flows. Presently, the footbridge has been in service for more than four years, maintaining an adequate comfort level.

Composite materials, with characteristics of light weight and high strength, are useful in manufacturing. Therefore, precise design and analysis is the first key procedure in composite applications, improper analysis or use of composite materials may cause serious failures. In this paper, wavelet finite element method (WFEM) based on B-spline wavelet on the interval (BSWI) is constructed for precise analysis of laminated plates and shells, which gives a guidance in design and application of composite structures. First, FEM formulations are derived from the generalized potential energy function based on the generalized variational principle and virtual work principle. Then, BSWI scaling functions are used as interpolation function to discretize the solving displacement field variables. At the same time, transformation matrix is constructed and used to translate the meaningless wavelet coefficients into physical space. At last, the static analysis results can be obtained by solving the FEM formulations. Due to the excellent features of BSWI, such as multiresolution, multiscale, localization and excellent numerical approximation characteristics etc., BSWI-based FEM can achieve accurate and efficient analysis by comparing with traditional methods. In the end, the effectiveness of the constructed BSWI WFEM is verified through several numerical examples.

In the framework of the Reissner–Simo rod theory and following Haringx’ approach for studying axial buckling in shear deformable rods, we give a mechanical interpretation of tensile instability, together with its mathematical justification, and we perform a linearized eigenvalue buckling analysis for tense planar rods. Buckled shapes and critical loads are calculated for most usual boundary conditions.

Buckling and free vibration behavior of functionally graded carbon nanotube reinforced polymer composite plate subjected to nonuniform temperature fields have been investigated using finite element approach. The effective material constants of the plate are obtained using the extended rule of mixture along with efficiency parameters of the carbon nanotube (to include geometry-dependent material properties). Influence of boundary conditions, aspect ratio, functional grading of the carbon nanotube, nonuniform thermal loading on thermal buckling and free vibration behavior of the heated plate are analyzed. It is observed that temperature fields and functional grading are influenced on the critical buckling temperature of the plates. Further, nature of functional grading showed significant change in buckling mode shapes irrespective of the boundary conditions. The first few natural frequencies of the plate under thermal load decreases as the temperature increases and they are influenced significantly by the nature of temperature field. Variations in free vibration mode shapes of the square plates found with not significant change as temperature increases. However, free vibration modes of the rectangular plates are sensitive to the nature of temperature field whenever there is a free edge associated with the boundary condition. Influence of functional grading on the free vibration mode shapes is not significant in contrast with the free vibration natural frequencies. The magnitude of free vibration natural frequencies of functional grade-X type carbon nanotube reinforcement showed higher in comparison with other two types of reinforcements considered here.

The present paper describes a numerical modeling approach to predict impact resistance and residual Shear Strength After Impact (SSAI) of fiber reinforced polymer composites subjected to bird strike loading. An improved damage mechanics based on material model, previously developed by the authors, is combined with an equation of state to simulate the progressive failure in composite aerostructures subjected to bird strike loading. A series of bird strike impacts on flat panels fabricated from low cost woven glass composite materials are used to validate the material model for practical composite component applications. A numerical study on the residual SSAI of a typical composite shear web is also presented. The panels are modelled with shell elements only. The proposed material model formulation accounts for the strain rate enhancement to strength and shear nonlinearities observed in composite materials. A hydrodynamic model for the bird, based on 90% water and 10% air, is derived to represent the behavior of the bird for all impact scenarios considered. The bird is heterogeneous in nature. However, a uniform material behavior is assumed with a geometry based on a 2:1 length to diameter ratio with a cylindrical body and spherical end caps using Lagrangian mesh. Appropriate contact definitions are used between the bird and the composite panel. The simulations results are compared to experimental results and conclusions drawn.

Blast wall is considered to be an effective passive measure for blast protection since it can effectively reduce the blast loads and protect the building structures and people behind it. However, the current practice in blast wall design mainly depends on the structural strength and ductility to resist blast loads. These designs often lead to huge solid walls which are not only expensive, but also unsuitable for construction in urban areas, as they are not aesthetically appealing. Moreover, failure of solid blast wall may generate a significant amount of debris, which imposes great threats to people and structures behind the wall. In this paper, a new fence type blast wall, instead of the solid wall, is proposed to resist the blast loads based on the concept of wave interference. The proposed fence wall uses structural columns placed at strategic locations as wave stoppers to generate wave reflection, diffraction and interaction between the reflected and diffracted waves from different columns to result in self-cancellation of wave energy, thus leads to substantial reduction in blast wall size in design. Numerical simulations are carried out to investigate the effectiveness of the fence wall layout with different column geometries, column spacing, column dimensions, and fence layers on blast loads reduction. Based on the results, an effective design of the fence type blast wall is proposed, which can reduce the pressure and impulse of the blast loads behind the wall upto 70%.

This paper analyzed the vibration of planar frame structures using the transfer function, which is obtained as the Laplace transform of Green’s function. The transfer function was used to represent the relationship between the excitation (including the initial and boundary conditions) and the response of the system; that is, it can determine the vibration response and stability of the system. The frame was divided into several joint blocks with substructures (beams). A state-space matrix form was used to represent the equation of motion in the beams. The compatibility between the joint blocks and beams allows us to establish the characteristic matrix of the frame, of which the determinant is the characteristic equation. With the eigenvalues obtained as the roots of the characteristic equation, one can establish the eigenfunction of the frame. The receptance of the structure with a single point excitation was also studied. The application of the transfer function to analysis of the L- and H-shaped planar frame structures was conducted in this paper. The results agree well with those published in the literature.