4
Temperature-induced responses, such as strains and displacements, are related to the boundary conditions. Therefore, it is required to determine the boundary conditions to establish a reliable bridge model for temperature-induced responses analysis. Particularly, bridge bearings usually present nonlinear behavior with an increase in load, and the nonlinear boundary conditions cause significant effect on temperature-induced responses. In this paper, the bridge nonlinear boundary conditions were simulated as bilinear translational or rotational springs, and the boundary parameters of the bilinear springs were identified based on the measured temperature-induced responses. First of all, the temperature-induced responses of a simply support beam with nonlinear translational and rotational springs subjected to various temperature loads were analyzed. The simulated temperature-induced strains and displacements were assumed as measured data. To identify the nonlinear translational and rotational boundary parameters of the bridge, the objective function based on the temperature-induced responses is then created, and the nonlinear boundary parameters were further identified by using the nonlinear least squares optimization algorithm. Then, a beam structure with nonlinear translational and rotational springs was simulated as a numerical example, and the nonlinear boundary parameters were identified based on the proposed method. The numerical results show that the proposed method can effectively identify the parameters of the nonlinear boundary conditions. Finally, the boundary parameters of a real arch bridge were identified based on the measured strain data and the proposed method. Since the bearings of the real bridge do not perform nonlinear behavior, only the linear boundary parameters of the bridge model were identified. Based on the bridge model and the identified boundary conditions, the temperature-induced strains were recalculated to compare with the measured strain data. The recalculated temperature-induced strains are in a good agreement with the real measured data.
33Seismic analysis of motorway bridges accounting for key structural components and nonlinear soil–structure interaction
Seismic analysis of motorway bridges accounting for key structural components and nonlinear soil–structure interaction
16Static inelastic analysis of steel frames with flexible connections
The effects of connection flexibility and material yielding on the behavior of plane steel frames subjected to static (monotonic) loads are presented in this paper. Two types of material nonlinearities are considered: flexible nodal connections and material yielding, as well as geometric nonlinearity of the structure. To account for material yielding, a plastic hinge concept is adopted. A flexible connection is idealized by nonlinear rotational spring. Plastic hinge is also idealized by nonlinear rotational spring attached in series with the rotational spring that accounts for connection flexibility. The stiffness matrix for the beam with flexible connections and plastic hinges at its ends is obtained. To illustrate the validity and accuracy of the proposed numerical model, several examples have been conducted.
Read moreSoftening and Stiffening Size Effects in Free Flexural Vibration of Small-scale Cracked Beams
Studying the dynamics of small-scale beams with cracks is crucial for damage detection and maintenance in micro- and nano-electromechanical systems. This paper studies the size-dependent free transverse vibration of miniaturized cracked beams using a local/nonlocal stress-driven gradient elasticity model. A key novelty of this model is its ability to simulate both softening and stiffening behaviors at small scales, unlike other stress-driven nonlocal models in the literature. The effect of cracks on the vibration of beams is modeled by introducing rotational and translational springs at the cracked cross-sections. The analysis considers a Timoshenko small-scale beam with an arbitrary number of cracks. To solve the problem, the beam is divided into sub-beams at the cracked cross-sections, and the higher-order equations of motion are solved for each sub-beam individually. The frequencies and associated mode shapes are derived by solving the eigenvalue problem constructed by the imposition of the standard variationally consistent and non-standard constitutive boundary and continuity conditions. The accuracy of the model is verified against experimental, molecular dynamics, and analytical results from the literature. The formulated model is further used to investigate the frequencies of intact and cracked beams with different boundary conditions. The effects of shear rigidity, boundary conditions, nonlocal parameters, crack length and location, and multiple cracks on frequencies and mode shapes are systematically analyzed.
Read moreA linear approximation for the regular reflection of a weak shock at a wedge satisfying sonic condition
A linear approximation for the regular reflection of a weak shock at a wedge satisfying sonic condition
3Chaotic oscillations of linear hyperbolic PDE with variable coefficients and implicit boundary conditions
<p style='text-indent:20px;'>In this paper, the chaotic oscillations of the initial-boundary value problem of linear hyperbolic partial differential equation (PDE) with variable coefficients are investigated, where both ends of boundary conditions are nonlinear implicit boundary conditions (IBCs). It separately considers that IBCs can be expressed by general nonlinear boundary conditions (NBCs) and cannot be expressed by explicit boundary conditions (EBCs). Finally, numerical examples verify the effectiveness of theoretical prediction.</p>
Read more2PREDICTING THE TRANSMISSIBILITY OF A GLOVE MATERIAL TO THE PALM USING A SIMPLE LUMPED PARAMETER MODEL OF THE HAND AND THE GLOVE
Assessing a glove for its ability to reduce vibration transmitted to the hand can be improved if the transmissibility of the glove to the hand can be predicted. This study proposes a simple lumped parameter model of the hand and the glove for predicting the transmissibility of a glove to the hand. The model of the hand consists of three main body segments: the palm, the fingers, and the palm tissues, connected via translational and rotational springs and dampers. The glove material was represented by translational spring and damper. The results showed that the glove transmissibility predicted using the model overestimated the glove transmissibility measured experimentally at frequencies greater than 62 Hz, implying that a simple three degree-of-freedom model of the hand and the glove may not be able to provide a reasonable prediction of glove transmissibility.
Read more6Simulation of cyclic response of precast concrete beam-column joints
Experience of previous earthquakes shows that a considerable portion of concrete precast buildings sustain relatively large damages especially at the beam-column joints where the damages are mostly caused by bar slippage. Precast concrete buildings have a kind of discontinuity in their beam-column joints, so reinforcement details in this area is too important and have a significant effect on the seismic behavior of these structures. In this study, a relatively simple and efficient nonlinear model is proposed to simulate pre- and post-elastic behavior of the joints in usual practice of precast concrete building. In this model, beam and column components are represented by linear elastic elements, dimensions of the joint panel are defined by rigid elements, and effect of slip is taken into account by a nonlinear rotational spring at the end of the beam. The proposed method is validated by experimental results for both internal and external joints. In addition, the seismic behavior of the precast building damaged during Bojnord earthquake 13 May 2017, is investigated by using the proposed model for the beam-column joints. Damage unexpectedly inducing the precast building in the moderate Bojnord earthquake may confirm that bearing capacity of the precast building was underestimated without consideration of joint behavior effect.
Read more13On equilibrium solutions of diffusion equations with nonlinear boundary conditions
The existence or the nonexistence of nonconstant stable equilibrium solutions for a diffusion equation with nonlinear Neumann boundary conditions is studied. We prove the nonexistence of nonconstant stable equilibria when the nonlinearity has a small Lipschitz constant or a second derivative of constant sign or either when the domain is a ball. We construct an example of existence for a connected domain with several disconnected boundary components.
Read more4Effects of Boundary Conditions on the Structural Dynamics of Wind Turbine Blades—Part 1: Flapwise Modes
Mode shapes and resonant frequencies of an individual wind turbine blade can be readily determined in either a laboratory or a blade test facility using experimental modal analysis. However, performing a modal test on a utility-scale wind turbine with several blades attached to a tower can be a challenge due to the number of sensors required, the size of these structures, the time required for testing, and cost. Therefore, understanding the influence of the coupled three-bladed turbine/tower system and identifying a correlation between the dynamic behavior of an assembled wind turbine to an individual blade or three-bladed turbine attached to a hub while disconnected from the tower is desirable. In this paper, which is the first part of a two-part paper, the influence of boundary conditions on flapwise mode shapes and resonant frequencies of wind turbine blades are numerically studied using a finite element beam analysis (a similar study was performed on edgewise modes of the turbine and is presented in the second part of this paper). In the current paper, translational and rotational springs are mounted to the hub of a three-bladed turbine and the sensitivity of dynamic characteristics (natural frequencies and mode shapes) to variations in the spring constants are investigated. Then, a model is developed of the three-bladed turbine installed on a tower and the dynamic characteristics of the assembly are compared to the three-bladed turbine with a free-free or fixed boundary condition at the hub. Furthermore, the mode contribution matrix of the assembled wind turbine is used to identify the necessary set of modal vectors of the tower and three-bladed turbine to accurately obtain the dynamic behavior of the final assembly. Many flapwise mode shapes of the assembled three-bladed wind turbine can be estimated by applying a fixed condition for a single blade (or a three-bladed turbine) instead of using a free-free boundary condition.
Read more3Boundary shape function iterative method for nonlinear second-order boundary value problems with nonlinear boundary conditions
Boundary shape function iterative method for nonlinear second-order boundary value problems with nonlinear boundary conditions
Read more7Elastic instability of beams subjected to a partially tangential force
Elastic instability of beams subjected to a partially tangential force
5Development of a new iterative method and its convergence analysis for nonlinear fourth‐order boundary value problems arising in beam analysis
In this study, an effective iterative technique based on Green's function is proposed to solve a nonlinear fourth‐order boundary value problem (BVP) with nonlinear boundary conditions, which models an elastic beam. An iterative Green's function approach and a shooting method are integrated in the proposed method. The mathematical derivation is further supported by examining the convergence analysis of the proposed method. The iterative method rapidly generates a convergent series solution to the given problem. The proposed method has many advantages over existing methods: (a) A rapid convergence and (b) the ability to generate a highly accurate series solution with just a few iterations for complex problems arising in elastic beam. To demonstrate the applicability and effectiveness of the proposed method, four numerical examples are tested. The numerical results show that our methodology delivers more efficient results compared to other existing methods.
Read more25A hydraulic cylinder subjected to Euler's load in aspect of the stability and free vibrations taking into account discrete elastic elements
A hydraulic cylinder subjected to Euler's load in aspect of the stability and free vibrations taking into account discrete elastic elements
Read more10Stress-driven nonlocal integral model with discontinuities for transverse vibration of multi-cracked non-uniform Timoshenko beams with general boundary conditions
Stress-driven nonlocal integral model with discontinuities for transverse vibration of multi-cracked non-uniform Timoshenko beams with general boundary conditions
Read more22A variational approach to free vibration analysis of shear deformable polygonal plates with variable thickness
A variational approach to free vibration analysis of shear deformable polygonal plates with variable thickness
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