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1.
The evaluation of the out‐of‐plane behaviour of unreinforced walls is one of the most debated topics in the seismic assessment of existing masonry buildings. The discontinuous nature of masonry and its interaction with the remainder of the building make the dynamic modelling of out‐of‐plane response troublesome. In this paper, the results of a shaking table laboratory campaign on a tuff masonry, natural scale, U‐shaped assemblage (façade adjacent to transverse walls) are presented. The tests, excited by scaled natural accelerograms, replicate the behaviour of external walls in existing masonry buildings, from the beginning of rocking motion to overturning. Two approaches have been developed for modelling the out‐of‐plane seismic behaviour: the discrete element method and an SDOF analytic model. Both approaches are shown to be capable of reproducing the experimental behaviour in terms of maximum rotation and time history dynamic response. Finally, test results and numerical time history simulations have been compared with the Italian seismic code assessment procedures. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
A nonlinear macroelement model for the seismic analysis of masonry buildings 总被引：1，自引：0，他引：1 
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下载免费PDF全文 The macroelement technique for modelling the nonlinear response of masonry panels is particularly efficient and suitable for the analysis of the seismic behaviour of complex walls and buildings. The paper presents a macroelement model specifically developed for simulating the cyclic in‐plane response of masonry walls, with possible applications in nonlinear static and dynamic analysis of masonry structures. The model, starting from a previously developed macroelement model, has been refined in the representation of flexural–rocking and shear damage modes, and it is capable of fairly simulating the experimental response of cyclic tests performed on masonry piers. By means of two internal degrees of freedom, the two‐node macroelement permits to represent the coupling of axial and flexural response as well as the interaction of shear and flexural damage. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
A plasticity based constitutive model for anisotropic behaviour of soils is implemented in a finite element procedure based on the generalized Biot theory for the dynamic non-linear response of porous materials. The model represents a version in the hierarchical approach of constitutive modelling and allows for inelastic response during loading, unloading and reloading. The procedure has been verified previously with respect to closed-form solutions for wave propagation in porous media. In this paper, it is used to predict the behaviour of a realistic structure-saturated porous soil system subjected to earthquake loading. Both linear and non-linear analyses have been performed. It has been found that the predicted responses from the two analyses are significantly different; for example, in comparison with the linear analysis the non-linear response shows increased magnitudes and zones of concentration of pore water pressures, increased magnitudes of horizontal displacements, decreased magnitudes of vertical displacements and increased magnitudes of shear stresses. 相似文献
4.
The basic aspects of testing small-scale masonry building models on simple earthquake simulators are discussed. Since the scale effects represent a difficult problem to solve, the overall seismic behaviour of structural systems, and not the behaviour of structulal details, has been studied by testing the reduced-sized models on a simple earthquake simulator. Accurate results regarding the dynamic behaviour and failure mechanism of the tested structures have been obtained by means of testing the relatively simple, adequately designed small-scale masonry building models. A simple earthquake simulator capable of simulating the uni-directional earthquake ground motion has been developed to study the seismic behaviour of masonry building models. Although a multipurpose programmable actuator was used to drive the shaking table, the comparison of the dynamic characteristics of the generated shaking-table motion and the earthquake acceleration records used for the simulation of seismic loads showed an acceptable degree of correlation between the input and output seismic motion. 相似文献
5.
This paper presents some findings of an investigation into the dynamic behaviour of offshore gravity platforms excited by waves. Results obtained from a finite element model are presented in the form of dynamic magnification factor curves for two structures typical of current concrete platform designs. In order to facilitate interpretation of these results a simple two degree of freedom model is developed and the equivalent results presented. These are found to be very similar to those obtained from the more detailed idealization, and it is therefore concluded that the principal mechanisms involved in the dynamic behaviour of offshore gravity structures are adequately represented in the simple model. Several useful insights into this behaviour are then achieved by closer examination of the two degree of freedom configuration. 相似文献
6.
Using the concept of lumped masses and rigid floor slabs, several mathematical models were built using a popular PC‐based finite element program to model a tall building with a frame‐core wall structural system. These models were analysed to obtain the first nine mode shapes and their natural frequencies which were compared with those from field measurements, using numerical correlation indicators. The comparison shows several factors that can have a significant effect on the analysis results. Firstly, outriggers connecting the outer framed tube system to the inner core walled tube system have a significant effect on fundamental translational mode behaviour. Secondly, detailed modelling of the core considering major and minor openings as well as internal thin walls has the strongest influence on torsional behaviour, whose measurements were shown to be an important aspect of the dynamic behaviour for the structure studied. Fine tuning of an analytical model requires not just considering variation in values of structural parameters but also attention to fine detail. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
7.
The determination of displacement demands for masonry buildings subjected to seismic action is a key issue in the performance-based assessment and design of such structures. A technique for the definition of single-degree-of-freedom (SDOF) nonlinear systems that approximates the global behaviour of multi-degree-of-freedom (MDOF) 3D structural models has been developed in order to provide useful information on the dependency of displacement demand on different seismic intensity measures. The definition of SDOF system properties is based on the dynamic equivalence of the elastic properties (vibration period and viscous damping) and on the comparability with nonlinear hysteretic behaviour obtained by cyclic pushover analysis on MDOF models. The MDOF systems are based on a nonlinear macroelement model that is able to reproduce the in-plane shear and flexural cyclic behaviour of pier and spandrel elements. For the complete MDOF models an equivalent frame modelling technique was used. The equivalent SDOF system was modelled using a suitable nonlinear spring comprised of two macroelements in parallel. This allows for a simple calibration of the hysteretic response of the SDOF by suitably proportioning the contributions of flexure-dominated and shear-dominated responses. The comparison of results in terms of maximum displacements obtained for the SDOF and MDOF systems demonstrates the feasibility and reliability of the proposed approach. The comparisons between MDOF and equivalent SDOF systems, carried out for several building prototypes, were based on the results of time-history analyses performed with a large database of natural records covering a wide range of magnitude, distance and local soil conditions. The use of unscaled natural accelerograms allowed the displacement demand to be expressed as a function of different ground motion parameters allowing for the study of their relative influence on the displacement demand for masonry structures. 相似文献
8.
Ioannis N. Psycharis 《地震工程与结构动力学》1983,11(4):501-521
The dynamic behaviour of a simplified model of a multi-storey building, supported by an elastic foundation and allowed to uplift, is examined. The building is modelled by an n-degree-of-freedom oscillator, while the foundation is represented by a viscously damped two-spring model which permits uplift. This model has been shown in previous studies to be an accurate approximation to the more realistic but more complex Winkler foundation. Approximate values for the characteristic frequencies of the interacting system are presented and a simple, first-mode solution is developed. The response of the system is non-linear and the apparent fundamental period increases with the amount of lift-off. In contrast to the first mode of the superstructure which participates strongly in the interaction, the second and higher modes of the building are not affected significantly by either the interaction with the soil or the uplift. The study shows that lift-off results in larger rocking motion of the structure, but it is not clear from the analysis and the example whether the interfloor displacements are consistently increased or decreased, since this appears to depend on the properties of the system and the excitation. 相似文献
9.
L. A. S. Kouris H. Meireles R. Bento A. J. Kappos 《Bulletin of Earthquake Engineering》2014,12(4):1777-1803
Timber-framed (TF) masonry has been developed as an effective lateral-load resisting system in regions of high seismicity such as Southern Europe. A salient feature of the ‘last generation’ of TF buildings is the presence of diagonal members that may consist of two diagonal braces. The present study focusses on alternative modelling procedures, ranging from simple to rather complex, for this interesting type of traditional structure. All models are applied to study the behaviour of full-scale specimens of diagonally-braced TF panels. The complex model is based on plasticity with contact surfaces for the connection between timber diagonals and masonry infills. A parametric analysis using this model shows that masonry infills affect only slightly the lateral force carried by this TF panel configuration. Furthermore, two simple modelling techniques are put forward for application in the analysis of large, realistic structures incorporating TF walls. The first one is directly connected to the complex modelling and is based on substructuring. A nine-step procedure is developed and is found to properly reproduce the response of the test specimens. The second simple model is a phenomenological one, developed on the basis of observed behaviour during tests and is a complete hysteretic model; however, for comparison purposes, all models are evaluated here with respect to the prediction of the envelope (pushover) curve for the walls tested under lateral loads. 相似文献
10.
《地震工程与工程振动(英文版)》2015,(3)
Analytical models prepared from field drawings do not generally provide results that match with experimental results.The error may be due to uncertainties in the property of materials,size of members and errors in the modelling process.It is important to improve analytical models using experimentally obtained data.For the past several years,data obtained from ambient vibration testing have been successfully used in many cases to update and match dynamic behaviors of analytical models with real structures.This paper presents a comparison between artificial neural network(ANN) and eigensensitivity based model updating of an existing multi-story building.A simple spring-mass analytical model,developed from the structural drawings of the building,is considered and the corresponding spring stiffness and lumped mass of all floors are chosen as updating parameters.The advantages and disadvantages of these updating methods are discussed.The advantage is that both methods ensure a physically meaningful model which canbe further employed in determining structural response and health monitoring. 相似文献
11.
In this paper, a simple cyclic cracking model incorporating crack dilatancy effect is proposed to model the behaviour of reinforced
concrete structures under earthquake-like dynamic loading. This model has been implemented into a FE programme [LUSAS (2004)
Luscas User Manual (version 12.3), FEA Ltd., London, England] to simulate reversed and cyclic loading. A shaking table test performed in Switzerland
at the Swiss Federal Institute of Technology at Zurich (ETHZ) has been chosen for comparison. The test performed on the shaking
table simulated a wall of a 3-storey building. The natural frequency and the crack pattern have been calculated and show reasonable
agreement with the experimental results 相似文献
12.
A base-isolated building is liable to have a small horizontal eccentricity between the centre of mass of the superstructure and the centre of rigidity of the supporting bearings. In seismic analysis, the structure is modelled as a rigid block with tributary masses supported on massless elastomeric rubber bearings placed at a constant elevation below the centre of mass. This simplified system has three degrees of freedom: two translations and one rotation in the vertical plane. The investigation of the dynamic behaviour of a base-isolated building is carried out for both the detuned and the perfectly tuned cases. In the detuned case, the natural frequencies of the system are assumed to be well separated. In the perfectly tuned case, the uncoupled rocking frequency is assumed to be identical to the vertical translational frequency, which may result from an unusual mass distribution and/or an extreme aspect ratio of the superstructure. Perturbation methods are implemented in finding the dynamic characteristics for both cases. However, the dynamic response of the perfectly tuned case is the major concern in this investigation. The Green's functions for the displacement response of the three-degree-of-freedom system are derived for both the undamped and damped conditions. The response spectrum modal superposition method is used in estimating the maximum acceleration response. A simple method, accounting for the effect of closely spaced modes, is proposed for combining modal maxima and results in an approximate solution corresponding to a single-degree-of-freedom system. This approximate solution may be used for the preliminary design of a base-isolated structure. Numerical results for a base-isolated building subjected to the vertical component of the El Centro earthquake of 1940 were carried out for comparison with these analytical results. The proposed modal combination method showed superiority over the conventional Square Root of the Sum of the Squares method in estimating maximum responses. The results also indicated that the approximate single-degree-of-freedom system yields accurate estimations. It is shown that the effect of rocking coupling on the vertical response of base-isolated structures subjected to transient loadings, such as earthquake motions, can generally be neglected as a result of the combined effects of the time lag between the maximum translational and rotational responses and the influence of damping in the isolation system, which for elastomeric bearings can be as high as 8 to 10 per cent of critical. 相似文献
13.
The dynamic identification of a historical masonry palace located in Benevento (Italy) has been carried out. The case study is representative of many buildings located in historic Italian centres. Since the building has been instrumented by the Department of Civil Protection with a permanent dynamic monitoring system, some of the recorded data, acquired in various operating conditions have been analysed with basic instruments of the Operational Modal Analysis in order to identify the main eingenfrequencies and vibration modes of the structure. The experimental results have been compared to the numerical outcomes provided by a detailed three-dimensional Finite Element (FE) model of the building where Soil–Structure Interaction (SSI) has been taken into account. The comparison of experimental vs. numerical frequencies and vibration modes of the palace evidenced the role exerted by the subsoil on the dynamic response of the building. 相似文献
14.
The dynamic interaction of adjacent buildings in cities and urban areas through the soil medium is inevitable. This fact has been confirmed by various analytical and numerical studies. However, very little research is available on the physical modelling of the Structure-Soil-Structure Interaction (SSSI) problem and its effect on the dynamics of adjacent structures. In this paper, a series of shaking table tests was conducted at the Earthquake and Large Structures Laboratory (EQUALS) at the University of Bristol to examine the effects of SSSI on the response of a model building when bordered by up to two other model buildings under dynamic excitation. The results indicated that depending on their height, the presence of one or two adjacent building could positively or negatively alter seismic power and peak acceleration responses of a building in comparison to when it is tested in isolation. 相似文献
15.
16.
In this report, three different models in increasing order of complexity have been used to identify the seismic behaviour of a three-storey steel structure subjected to arbitrary forcing functions, all of which excite responses within the elastic range. All of the models are constructed using system identification. In the first model, five parameters have been used to identify the frame. Treating the system as a shear building, we assign one stiffness coefficient to each floor and introduce Rayleigh-type damping with two additional parameters. The mass, assumed to be concentrated at a floor level, is kept constant throughout the study. The parameters are established using a modified Gauss-Newton algorithm. The match between measured and predicted quantities is satisfactory when these quantities are restricted to floor accelerations or displacements. To remove the constraint imposed by assuming that the frame deforms as a shear building, a second model with eight parameters is introduced, allowing rotations of the joints as independent degrees of freedom. Six of the eight parameters are related to the stiffness characteristics of the structural members while the remaining two are related to damping as before. In constructing the eight-parameter model, we learned that it is the effective lengths of the members that change during optimization. We also found that the independent response quantities, floor accelerations and joint rotations, must be used in the cost function for the optimization algorithm to converge. The match between measured and predicted quantities for the eight-parameter model is excellent. The set of parameters derived from the minimum squared error gives a model that shows very good correlation using information on the full duration of the pulse or only a portion of it. Also the same correlation exists between the coefficients obtained from different excitations. In an effort to explain the values of the parameters associated with the girders, an additional degree of freedom, namely, the pitching motion of the shaking table, is introduced as an additional degree of freedom. The paper presents, therefore, a five-, an eight- and, finally, a nine-parameter model. 相似文献
17.
Correlating measured and simulated dynamic responses of a tall building to long‐distance earthquakes
For almost a decade, a 66‐storey, 280m tall building in Singapore has been instrumented to monitor its dynamic responses to wind and seismic excitations. The dynamic characteristics of the tall building have been investigated via both the finite element method and the experimental modal analysis. The properties of the finite element model have been shown to correlate well with those derived from the data recorded during the ambient vibration tests. During the study period, 21 sets of earthquake ground motions have been recorded at the building site. The basement motions may be divided into three categories based on their predominant frequency components with respect to the building's fundamental frequency. The calibrated three‐dimensional finite element model is employed to simulate the seismic response of the tall building. Correlation analysis of the time histories between the recorded data and the simulated results has been carried out. The correlation analysis results show that the simulated dynamic response time histories match well with those of the recorded dynamic responses at the roof level. The results also show that the simulated maximum response at the roof level is close to the peak response recorded during the earthquakes. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
Haruo Takizawa 《地震工程与结构动力学》1975,4(1):73-94
This paper is a study of idealizing a planar reinforced concrete frame as a non-linear dynamic system for the purpose of simulating its inelastic behaviour during severe earthquakes. After having estimated the restoring force characteristics of all constituent members by experimental means (represented, for example, by a group of empirical equations), it is possible to estimate the non-linear characteristics of the complete structure and to trace the damaging process for each constituent member under a given ground motion disturbance. However, this technique, which is directly based on member-level properties, generally requires rather laborious computational procedures; for practical reasons it is necessary to develop a simplified model, reducing the required calculation without losing the substance of the mechanical phenomena. Thus the reliability of simplification by conventional shear modelling is examined in direct comparison with the response results from rigorous modelling. It is concluded that the shear modelling generally yields an inadequate and, in many cases, erroneous result. The primary cause leading to this discrepancy is identified and, based on this discussion, a more appropriate modelling as simple as conventional shear modelling is proposed. 相似文献
19.
为提高大型复杂结构体系的计算效率,在深入分析约束模态综合法原理的基础上,论述了非比例阻尼体系中约束模态综合法对阻尼矩阵的处理方法,并探讨了如何缩减对接界面自由度的问题。同时,通过算例详细说明了该方法在高层建筑结构动力时程分析中的应用。计算结果表明,在利用约束模态综合法求解非比例阻尼体系的动力问题时,文中所采用的阻尼矩阵的处理方法是有效的,与有限元直接法相比具有很好的精度。对于地基土-高层建筑结构体系的地震响应分析问题而言,缩减对接界面自由度的约束模态综合法可达到很好的计算精度,能够更大程度的提高计算效率,为大型复杂结构的动力时程分析研究和工程应用提供了一定的依据和方便。 相似文献
20.
Seismic behaviour of shallow foundations: Shaking table experiments vs numerical modelling 总被引：1，自引：0，他引：1
The capability of a simplified approach to model the behaviour of shallow foundations during earthquakes is explored by numerical simulation of a series of shaking table tests performed at the Public Works Research Institute, Tsukuba, Japan. After a summary of the experimental work, the numerical model is introduced, where the whole soil–foundation system is represented by a multi‐degrees‐of‐freedom elasto‐plastic macro‐element, supporting a single degree‐of‐freedom superstructure. In spite of its simplicity and of the large intensity of the excitation involving a high degree of nonlinearity in the foundation response, the proposed approach is found to provide very satisfactory results in predicting the rocking behaviour of the system and the seismic actions transmitted to the superstructure. The agreement is further improved by introducing a simple degradation rule of the foundation stiffness parameters, suitable to capture even some minor details of the observed rocking response. On the other hand, the performance of the model is not fully satisfactory in predicting vertical settlements. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献