Evaluation of Modeling Strategies for Seismic Analysis of Confined Masonry Structures (original) (raw)
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Model for the Nonlinear Analysis of Confined Masonry Buildings
This paper presents a practical displacement-based evaluation procedure for the seismic assessment of low-height confined masonry buildings. First, the Coefficient Method is adapted to obtain rapid estimates of inelastic roof displacement demands for regular confined masonry buildings. Second, a nonlinear simplified model is introduced to perform pushover analysis of confined masonry buildings whose global and local behavior is dominated by shear deformations in the masonry walls. The model, which can be applied through the use of commercial software, can be used to estimate the capacity curve of a confined masonry building.
A numerical model for seismic analysis of masonry buildings: Experimental correlations
Earthquake Engineering & Structural Dynamics, 1984
A non-linear finite element model for plain masonry structures under lateral static loads and seismic base inputs is presented. Three super-imposed elasto-plastic shear elements are used in order to approximate the typical force-displacement curve for masonry. Material properties are identified with respect to results of shear tests on single piers. Modelling of entire structures is then performed and the numerical results are satisfactorily checked against the experimental outputs of static and shaking table tests of simple 1 and 2 storey buildings. The out of plane behaviour of walls is accounted for by means of a simplified method.
Engineering Model for Analyis of Masonry Structures
2nd Croatian Conference on Earthquake Engineering ‒ 2CroCEE
This paper presents the methodology for seismic analysis of masonry structures that can be employed in commercial software packages such as SAP2000. The concept of elementary block which combines non-linear spring and linear shell elements is used for discretization of masonry walls. The proposed modelling technique with localized nonlinearity can successfully simulate in-plane wall failure modes induced by compressive or tensile axial force and transverse force. It can also be used to investigate out-of-plane collapse which makes it a good candidate for 3D static and dynamic analysis of buildings. The modelling approach is tested on two examples where pushover analysis was performed: a single slender cantilever masonry wall and a family house. The response was verified against the results delivered by 3MURI and MINEA, and reasonable agreement was obtained. It is demonstrated that the transverse walls have significant contribution to the load bearing capacity of buildings.
A Simplified Approach for the Seismic Analysis of Masonry Structures
The Open Construction and Building Technology Journal, 2011
The strongly inelastic behaviour of masonry panels makes inadequate any kind of linear static analyses, and for this reason, both for academic and practical purposes, engineers have to deal with non-linear analyses of masonry buildings. On top of that, the need for non-linear static procedures (NSP) also arises as a consequence of the performancebased earthquake engineering concepts, that generally require the comparison of the seismic demand with the building capacity, expressed in terms of displacements. Within this framework, the choice of the appropriate models to use is fundamental matter: on one hand, the need for accurate predictions of the structural response leads to the adoption of very complex FEM models but, on the other and, the high computational skills and the very time-consuming analyses suggest the adoption of simplified models, such as the equivalent frame approach. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented, namely the software FREMA (Equivalent Frame Analysis of Masonry Structures) developed by the authors. In this work, the main innovative features of the proposed model (spread plasticity approach, displacement-driven loading process, accurate moment-curvature law for piers in rocking, flexural strength of spandrels) are discussed and an extensive validation of the model has been carried out by means of a comparison with experimental tests and accurate FEM models available in literature.
Nonlinear modelling of the seismic response of masonry structures: Calibration strategies
Bulletin of Earthquake Engineering, 2021
In this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibr...
The paper presents a comparison between two numerical modelling approaches employed to investigate the seismic behavior of unreinforced masonry buildings with flexible diaphragms. The comparison is performed analyzing a two-story prototype tested on a shaking table at the CNR-ENEA research center of Casaccia (Italy). The first numerical model was built by using the finite element (FE) technique, while the second one was built by a simplified macro-element (ME) approach. Both models were employed to perform non-linear dynamic analyses, integrating the equations of motion by step-by-step procedures. The shaking table tests were simulated to analyze the behavior of the prototype from the initial elastic state until the development of extensive damage. The main results of the analyses are discussed and critically compared in terms of engineering parameters, such as accelerations, displacements and base shears. The effectiveness of both models within the investigated typology of buildings is then evaluated in depth.
Numerical investigations on the seismic behaviour of confined masonry walls
In the last century, severe earthquakes highlighted the seismic vulnerability of unreinforced masonry buildings. Many technological innovations have been introduced in time in order to improve resistance, ductility, and dissipation properties of this type of constructions. The most widely diffused are reinforced masonry and confined masonry. Damage observation of recent earthquakes demonstrated the effectiveness of the response of confined masonry structures to seismic actions. In general, in this type of structures, reinforced concrete beams and columns are not main structural elements, however, they have the following functions: to confine masonry in order to increase its ductility; to bear tensile stresses derived from bending; to contrast the out-of-plane overturning of masonry panels. It is well evident that these functions are as much effectively performed as the connection between masonry and reinforced concrete elements is good (for example by mean of local interlocking or reinforcements). Confined masonry structures have been extensively studied in the last decades both from a theoretical point of view and by experimental tests Aims of this paper is to give a contribution to the understanding of the seismic behaviour of confined masonry walls by means of numerical parametrical analyses. There latter are performed by mean of the finite element method; a nonlinear anisotropic constitutive law recently developed for masonry is adopted. Comparison with available experimental results are carried out in order to validate the results. A comparison between the resistance obtained from the numerical analyses and the prevision provided by simplified resistance criteria proposed in literature and in codes is finally provided.
2016
The paper presents a comparison between two numerical modelling approaches employed to investigate the seismic behavior of unreinforced masonry buildings with flexible diaphragms. The comparison is performed analyzing a two-story prototype tested on a shaking table at the CNR-ENEA research center of Casaccia (Italy). The first numerical model was built by using the finite element (FE) technique, while the second one was built by a simplified macro-element (ME) approach. Both models were employed to perform non-linear dynamic analyses, integrating the equations of motion by step-by-step procedures. The shaking table tests were simulated to analyze the behavior of the prototype from the initial elastic state until the development of extensive damage. The main results of the analyses are discussed and critically compared in terms of engineering parameters, such as accelerations, displacements and base shears. The effectiveness of both models within the investigated typology of buildings is then evaluated in depth.
2009
Distinctive features which characterize the existing unreinforced masonry building (such as the presence of flexible floors and/or weak spandrels) make the possibility of simulating the actual conditions of the structure crucial: indeed, models usually employed for new constructions are not always suitable for existing ones. Different strategies of modelling can be adopted with increasing levels of accuracy and computational effort. In this paper attention will be focused on very Simplified Models, such as “strong spandrel-weak pier” or “weak spandrel-strong pier”, and much more complex models such as “Equivalent Frame Model” proposing a critical review of their use and of the reliability of the assumptions which they are founded on. Particular attention will be paid to the issues related to the assessment of the in-plane strength of URM walls distinguishing between those related to the idealisation of the masonry wall in an equivalent model (e.g. geometry and boundary conditions as...