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Katrin Beyer - One of the best experts on this subject based on the ideXlab platform.

  • force Displacement Response of in plane loaded unreinforced brick masonry walls the critical diagonal crack model
    Bulletin of Earthquake Engineering, 2017
    Co-Authors: Bastian Valentin Wilding, Katrin Beyer
    Abstract:

    This article introduces an analytical model to compute the monotonic force–Displacement Response of in-plane loaded unreinforced brick masonry walls accounting for walls failing in shear or flexure. The masonry wall is modelled as elastic in compression with zero tensile strength using a Timoshenko beam element. Its cross-section properties (moment of inertia and area) are continuously updated to capture the non-linearity that results from flexural and shear cracking. For this purpose, diagonal cracking of shear critical walls is represented by one Critical Diagonal Crack. The ultimate drift capacity of the wall is determined based on an approach evaluating a plastic zone at the wall toe. Validation against results of cyclic full-scale tests of unreinforced masonry walls made with vertically perforated clay units shows that the presented formulation is capable of accurately predicting the effective stiffness, the maximum strength and the ultimate drift capacity of the wall. It outperforms current empirical code equations with regard to stiffness and ultimate drift capacity estimates and yields similar results concerning strength prediction.

  • force Displacement Response of in plane loaded urm walls with a dominating flexural mode
    Earthquake Engineering & Structural Dynamics, 2015
    Co-Authors: Sarah Petry, Katrin Beyer
    Abstract:

    This article presents a new mechanical model for the non-linear force-Displacement Response of unreinforced masonry (URM) walls developing a flexural rocking mode including their Displacement capacity. The model is based on the plane section hypothesis and a constitutive law for the masonry with zero tensile strength and linear-elastic behaviour in compression. It is assumed that only the compressed part of the wall contributes to the stiffness of the wall and therefore the model accounts for a softening of the Response due the reduction of the effective area. Stress conditions for limit states are proposed that characterise the flexural failure. The new model allows therefore to link local performance levels to global Displacement capacities. The limit states criteria describe the behaviour of modern URM walls with cement mortar of normal thickness and clay bricks. The model is validated through comparison of local and global engineering demand parameters with experimental results. It provides good prediction of the effective stiffness, the force capacity and the Displacement capacity of URM walls at different limit states.

Kazuhiko Kawashima - One of the best experts on this subject based on the ideXlab platform.

  • relative Displacement Response spectra with pounding effect
    Earthquake Engineering & Structural Dynamics, 2001
    Co-Authors: Anat Ruangrassamee, Kazuhiko Kawashima
    Abstract:

    To avoid unseating of a deck, an adequate seat width must be provided. The seat width is basically determined from maximum relative Displacement between two bridge segments. Under a strong ground excitation, pounding between two decks may occur at a joint. The pounding will affect the Response of two bridge segments. This research is conducted to investigate the effect of pounding on the relative Displacement between two adjacent bridge segments. A simplified analytical model of two linear single-degree-of-freedom systems is employed. To take into account the pounding, the laws of conservation of momentum and energy are applied. The analytical results are represented in the form of relative Displacement Response spectra with pounding effect. It is found that due to the pounding the relative Displacement can be amplified, resulting in the requirement of a longer seat width to support a deck. The formulation of normalized relative Displacement Response spectra is presented together with an application example. It is found that the seat width determined from the relative Displacement Response spectra with pounding effect becomes close to the value specified in the Japanese design specifications for structures with large difference of natural periods.

  • residual Displacement Response spectrum
    Journal of Structural Engineering-asce, 1998
    Co-Authors: Kazuhiko Kawashima, Gregory A Macrae, Jyunichi Hoshikuma, Kazuhiro Nagaya
    Abstract:

    Structures subjected to strong earthquake ground shaking may be left in a displaced condition. The amount of this residual or permanent Displacement is determined by structural characteristics, including mass and hysteretic behavior, as well as ground motion. Residual Displacement is undesirable because it presents problems during repair and reconstruction after an earthquake. This paper describes analyses of many single-degree-of-freedom bilinear oscillators, with different natural periods, damping ratios, ductility factors, bilinear factors, and input ground motions. These analyses were carried out in order to obtain a method of estimating the likely residual Displacements of real single-degree-of-freedom structures. The residual Displacement was normalized by the maximum possible residual Displacement. Although there was scatter in the normalized residual Displacement for different earthquake records, trends in behavior were dominated by the slope of post-yielding branch of bilinear loop. A residual di...

K. Beyer - One of the best experts on this subject based on the ideXlab platform.

  • Limit states of modern unreinforced clay brick masonry walls subjected to in-plane loading
    Bulletin of Earthquake Engineering, 2015
    Co-Authors: S. Petry, K. Beyer
    Abstract:

    Recent research showed that the in-plane horizontal Displacement capacity of unreinforced masonry (URM) walls depends on numerous factors that are not yet captured by current empirical drift capacity models; e.g., axial stress, shear span, geometry of the walls and the material used. In order to improve the performance-based assessment of URM wall buildings, future research should aim at developing numerical and mechanical models that link the global force-Displacement Response of URM walls to local deformation measures such as strains. This paper addresses the behaviour of modern clay brick masonry and makes first contributions to such an endeavour by the evaluation of experimental results: first, two sets of limit states are proposed that link local damage limit states to characteristic points of the global force-Displacement Response of the URM wall. The two sets define limit states for walls developing a shear or a flexural mechanism respectively. Second, local deformation measures deemed suitable for the characterisation of these limit states are evaluated from optical measurement data of quasi-static cyclic wall tests. These include strains, compression zone depth and the ratio of shear to flexural deformations.

Xu Han - One of the best experts on this subject based on the ideXlab platform.

  • targeting the force Displacement Response of thin walled structures subjected to crushing load using curve decomposition and topometry optimization
    Structural and Multidisciplinary Optimization, 2019
    Co-Authors: Xu Han, Andres Tovar
    Abstract:

    This work introduces a new approach to targeting the dynamic Response of thin-walled energy-absorbing structures through the decomposition of the force-Displacement (FD) Response and the use of topometry (thickness) optimization. The proposed method divides the nonlinear optimization problem into a series of analytical subproblems. In each iteration, an explicit dynamic analysis is carried out and the dynamic Response of the structure is then used to define the subproblem. Numerical examples show that the algorithm can tailor the FD Response of the structure to a target FD curve. Progressive collapse, which is a high-energy collapse mode and desired in design for crashworthy, is observed in the optimized thin-walled structures. The proposed algorithm is computationally efficient as it uses a fewer explicit simulations to reach the target Response.

  • inversion of loading time history using Displacement Response of composite laminates three dimensional cases
    Acta Mechanica, 2002
    Co-Authors: G R Liu, W B, Xu Han
    Abstract:

    An inverse procedure is proposed to reconstruct the time history of transient loads on the surface of composite laminates from the knowledge of dynamic Displacement Response at only one receiving point. A hybrid numerical method (HNM) is adopted as the forward solver to compute the dynamic Displacement Response of composite laminates subjected to arbitrary loads. By introducing a kernel Displacement function — the dynamic Displacement Response of composite laminates excited by a point stepimpact load and the Displacement Response subjected to a load with an arbitrary force function are expressed in a form of convolution integral. The force history is reconstructed by employing an inversion algorithm, in which the least-squares optimization method being adopted to deconvolute the integral. Both point loads and loads with small spatial distribution are investigated and numerical verifications are given. The robustness of the procedure in the presence of noise is also investigated. Good agreements between the identified and true functions for all cases demonstrate the effectiveness of the present inverse procedure. The present inverse procedure is useful for determining impact loads on material surface using Response on a point remote to the impact point.

  • a combined genetic algorithm and nonlinear least squares method for material characterization using elastic waves
    Computer Methods in Applied Mechanics and Engineering, 2002
    Co-Authors: G R Liu, Xu Han, K.y. Lam
    Abstract:

    Abstract The inverse problem of material characterization is formulated as a parameter identification problem in which a set of parameters corresponding to the material property can be found by minimizing error functions formulated using the measured Displacement Response and the one computed by a forward solver based on projected candidates of parameters. A hybrid numerical method is employed as the forward solver to calculate the dynamic Displacement Response on the surface of the composite plate for given material property. A combined method is used as the inverse operator to determine the material property of composite plate. In this method, genetic algorithm is first used to select a set of better solutions close to the optima; then the nonlinear least squares method is applied using these better solutions as the initial guesses. Finally, the identification results can be determined from the solutions of nonlinear least squares method by comparing their corresponding error function values. Actual material characterizations of composites demonstrate the higher efficiency of the present method.

  • a quadratic layer element for analyzing stress waves in fgms and its application in material characterization
    Journal of Sound and Vibration, 2000
    Co-Authors: Xu Han, K.y. Lam, G R Liu, T Ohyoshi
    Abstract:

    Abstract A novel method is presented for investigating elastic waves in functionally graded material (FGM) plates excited by plane pressure waves. The FGM plate is first divided into quadratic layer elements (QLEs). A general solution for the equation of motion governing the QLE has been derived. The general solution is then used together with the boundary and continuity conditions to obtain the Displacement and stress in the frequency domain for an arbitrary FGM plate. The Response of the plate to an incident pressure wave is obtained using the Fourier transform techniques. Results obtained by the present method are compared with an existing method using homogeneous layer elements. Numerical examples are presented to investigate stress waves in FGM plates. The relationship between the surface Displacement Response and the material property of quadratic FGM plates has been analytically obtained for the material characterization. A computational inverse technique is also presented for characterizing material property of an arbitrary FGM plate from the surface Displacement Response data, using present QLE method as forward solver and genetic algorithm as the inverse operator. This technique is utilized to reconstruct the material property of an actual SiC-C FGM.

Snæbjörnsson, Jonas Thor - One of the best experts on this subject based on the ideXlab platform.

  • Improved long-span bridge modeling using data-driven identification of vehicle-induced vibrations
    'Wiley', 2020
    Co-Authors: Cheynet Etienne, Daniotti Nicolo, Jakobsen, Jasna Bogunovic, Snæbjörnsson, Jonas Thor
    Abstract:

    The paper introduces a procedure to automatically identify key vehicle characteristics from vibrations data collected on a suspension bridge. The primary goal is to apply a model of the dynamic Displacement Response of a long‐span suspension bridge to traffic loading, suitable for automatic identification of the vehicle passage over the bridge. The second goal is to improve the estimation of the structural damping of the bridge deck by utilizing the free‐decay Displacement Response induced by the passing vehicles. The vehicles responsible for a significant bridge vertical Response are first identified using an outlier analysis and a clustering algorithm. Utilizing a moving mass model, the equivalent mass and speed of each vehicle, as well as its arrival time, are assessed in a least‐squares sense. The computed vertical Displacement Response shows a remarkably good agreement with the full‐scale data in terms of peak values and root‐mean‐square values of the Displacement histories. The data acquired on the Lysefjord Bridge (Norway) indicate that the contribution of heavy traffic loading to the combined effects of wind and traffic excitation may be significant even at mean wind speeds above 10 m s−1. The critical damping ratios of the most significant vibrational modes of the Lysefjord Bridge are studied for low wind velocities, using the time‐decomposition technique and the traffic‐induced free‐decay Response of the bridge deck. The structural damping ratios estimated this way are found to be more accurate than those obtained with an automated covariance‐driven stochastic subspace identification algorithm applied to the same dataset.publishedVersio

  • Improved long‐span bridge modeling using data‐driven identification of vehicle‐induced vibrations
    John Wiley & Sons Ltd., 2020
    Co-Authors: Cheynet Etienne, Daniotti Nicolo, Jakobsen, Jasna Bogunovic, Snæbjörnsson, Jonas Thor
    Abstract:

    The paper introduces a procedure to automatically identify key vehicle characteristics from vibrations data collected on a suspension bridge. The primary goal is to apply a model of the dynamic Displacement Response of a long‐span suspension bridge to traffic loading, suitable for automatic identification of the vehicle passage over the bridge. The second goal is to improve the estimation of the structural damping of the bridge deck by utilizing the free‐decay Displacement Response induced by the passing vehicles. The vehicles responsible for a significant bridge vertical Response are first identified using an outlier analysis and a clustering algorithm. Utilizing a moving mass model, the equivalent mass and speed of each vehicle, as well as its arrival time, are assessed in a least‐squares sense. The computed vertical Displacement Response shows a remarkably good agreement with the full‐scale data in terms of peak values and root‐mean‐square values of the Displacement histories. The data acquired on the Lysefjord Bridge (Norway) indicate that the contribution of heavy traffic loading to the combined effects of wind and traffic excitation may be significant even at mean wind speeds above 10 m s−1. The critical damping ratios of the most significant vibrational modes of the Lysefjord Bridge are studied for low wind velocities, using the time‐decomposition technique and the traffic‐induced free‐decay Response of the bridge deck. The structural damping ratios estimated this way are found to be more accurate than those obtained with an automated covariance‐driven stochastic subspace identification algorithm applied to the same dataset

  • Improved long‐span bridge modeling using data‐driven identification of vehicle‐induced vibrations
    'Wiley', 2020
    Co-Authors: Cheynet Etienne, Daniotti Nicolo, Jakobsen, Jasna Bogunović, Snæbjörnsson, Jonas Thor
    Abstract:

    Publisher's version (útgefin grein)The paper introduces a procedure to automatically identify key vehicle characteristics from vibrations data collected on a suspension bridge. The primary goal is to apply a model of the dynamic Displacement Response of a long-span suspension bridge to traffic loading, suitable for automatic identification of the vehicle passage over the bridge. The second goal is to improve the estimation of the structural damping of the bridge deck by utilizing the free-decay Displacement Response induced by the passing vehicles. The vehicles responsible for a significant bridge vertical Response are first identified using an outlier analysis and a clustering algorithm. Utilizing a moving mass model, the equivalent mass and speed of each vehicle, as well as its arrival time, are assessed in a least-squares sense. The computed vertical Displacement Response shows a remarkably good agreement with the full-scale data in terms of peak values and root-mean-square values of the Displacement histories. The data acquired on the Lysefjord Bridge (Norway) indicate that the contribution of heavy traffic loading to the combined effects of wind and traffic excitation may be significant even at mean wind speeds above 10 m s(-1). The critical damping ratios of the most significant vibrational modes of the Lysefjord Bridge are studied for low wind velocities, using the time-decomposition technique and the traffic-induced free-decay Response of the bridge deck. The structural damping ratios estimated this way are found to be more accurate than those obtained with an automated covariance-driven stochastic subspace identification algorithm applied to the same dataset.Norwegian Public Roads Administration"Peer Reviewed