Seismic vulnerability assessment of confined masonry structures by macro-modeling approach (original) (raw)
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Bulletin of Earthquake Engineering
All around the world, non-engineered masonry constructions (NECs) typically have high vulnerability to seismic ground motion, resulting in heavy damage and severe casualties after earthquakes. Even though a number of computational strategies have been developed for seismic analysis of unreinforced masonry structures, a few studies have focussed on NECs located in developing countries. In this paper, different modelling options for finite element analysis of non-engineered masonry buildings are investigated. The goal of the study was to identify the modelling option with the best trade-off between computational burden and accuracy of results, in view of seismic risk assessment of NECs at regional scale. Based on the experimental behaviour of a single-storey structure representative of Indian non-engineered masonry buildings, the output of seismic response analysis of refined 3D models in ANSYS was compared to that of a simplified model based on 2D, nonlinear, layered shell elements i...
Evaluation of Modeling Strategies for Seismic Analysis of Confined Masonry Structures
2022
Numerical models are effective tools for nonlinear seismic analysis required for performance-based design of structures. However, their potential often falls short while simulating the behavior of masonry structures because of their complex anisotropic behavior. The complexity increases further for con ned masonry (CM) where, in addition to masonry, RC con ning members are constructed around the periphery of masonry walls such that the structure work in unison. Though some modeling schemes have been developed for linear and nonlinear analysis of CM walls, their applicability and accuracy are a matter of contention as they were based on different assumptions and theories. Most design codes do not specify modeling schemes due to limited research, especially considering the highly variable masonry properties. The limited modeling choices, some of which have not been validated su ciently, pose di culty for practicing engineers and limit their con dence in adopting them. The present work provides an understanding of the challenges on using different modeling strategies from an engineering practice perspective. Commonly adopted models were rst used to simulate previously tested single-story CM wall specimens having different aspect ratios. The comparative assessment showed the e cacy of some schemes, while exhibiting ineffectiveness of others. The applicability of different methods was then assessed by analyzing a three-story CM building. The observed behavior clari ed the characteristics and potentialities of different procedures, and provides direction to adopt better approaches for nonlinear analysis of CM walls.
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.
Seismic performance assessment of masonry structures with a modified “concrete” model
Bulletin of Earthquake Engineering, 2015
This paper deals with the proposal of a constitutive model for the FEM nonlinear analysis of masonry structures as well as the use of a nonlinear static adaptive procedure in order to estimate the inelastic response and seismic performance of masonry buildings. In particular, the mechanical behaviour of masonry was simulated as a continuous, homogeneous and isotropic material, using a "concrete" smeared-crack model modified by an interaction with the plasticity Drucker-Prager domain as well as the definition of a new compression failure surface. The calibration and validation of the FEM model was carried out through a sensitivity analysis of the different mechanical parameters, which were based on the experimental data available in current literature. Subsequently, the proposed material constitutive model was used for the seismic performance evaluation of masonry buildings. With this aim, an incremental non-iterative procedure based on the capacity spectrum method and inelastic demand response spectra was applied. According to performance-based engineering, this procedure allows for the correlation between the different risk levels and the expected performance levels for each limit state to be taken into account. In conclusion, the results obtained from the FEM model were compared with those from a well-known macro-element model.
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.
Simplified Seismic Assessment of Confined Masonry Buildings Based on Displacement
2015
The experiences from past Earthquakes show the seismic vulnerability of the confined masonry structures (CMS) against earthquake. Based on the results of experimental analysis, damage in these structures depends on lateral displacement which is exerted to the walls. In this paper based on analytical and numerical models a simplified nonlinear displacement-based approach is presented for seismic assessment of CMS. The methodology is based on the concept of ESDOF and displacement demand compared with displacement capacity at the characteristic period of vibration according to performance level. Displacement demand is identified by using nonlinear displacement spectrum corresponding to a specified limit state. This approach is based on macro model and nonlinear incremental dynamic analysis (IDA) of 3 dimension prototype structure taking into account uncertainty of mechanical properties that finally results into a precise method in its simplicity for seismic assessment of CMS. For valid...
Dynamic Analysis of Confined Masonry Structures for Residential Buildings under Seismic Conditions
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
In India, unreinforced brick masonry and reinforced cement concrete are the go-to technologies when it comes to construction of modern residential buildings, with the design applications ranging from one-story nuclear family houses to multi-story apartment buildings housing several families. However, each major natural disaster in India has exposed several 'chinks in the armour' linked to both of these widely employed construction techniques. Enter confined masonry. Confined masonry offers a substitute to both, unreinforced brick masonry and reinforced concrete framed residential buildings for applications in disaster prone areas of the world while keeping the cost under check and optimizing the structural performance. Confined masonry has evolved over the last century through an informal process based on its satisfactory performance in past, mostly in countries with high seismic activity like Indonesia, Mexico and Turkey. It is used for both non-engineered and engineered construction as its field applications range from one-story single-family dwellings to six-story apartment buildings. Some countries have even adopted design provisions and construction guidelines for confined masonry in their building codes. The success and implementation of building technologies is totally dependent on the local conditions like the availability and cost of building materials, the skill level of construction labour and the availability of construction tools and equipment. The fact that confined masonry construction looks similar to reinforced frame construction with masonry infill walls and that it uses the same components, i.e., masonry infills, tie-beams and tie-columns, helps in an easy transition to adopt confined masonry. Although confined masonry construction practice doesn't require any advanced construction equipment or an extra skillset, it is necessary to lay emphasis on the quality of the construction for its satisfactory performance. Hence, to optimize the quality of confined masonry structures, this thesis employs the use of a modern easy-to-learn-and-use structural software known as ETABS.
Experimental and Numerical Assessment of Confined and Unreinforced Brick Masonry Structures
2019
Brick masonry is widely used for building construction throughout the world. However, unreinforced brick masonry buildings performed poorly in the 2005 Kashmir earthquake, in Pakistan, resulting in a decline in the use of masonry construction. To investigate and quantify the performance of masonry against the seismic forces by confining it through typical stiffer, line elements (column and beams), a full-scaled room model of an area 3048 × 3658mm (10 × 12 ft) and height of 3353mm (11 ft) was constructed using confined brick masonry and tested under quasi-static cyclic loading. Damage details were observed after each loading cycle. The structure's response was interpreted through a hysteresis curve, after which the envelop curves were drawn and the envelop curve was then converted into bilinear curve for determining different limit states and performance levels. A comparison 2.7.2 Predominant design failures in confined masonry during Earthquakes .......
Theoretical and Experimental Engineering Analysis for Seismically Damaged Masonry Buildings
2001
Romania is one of the countries undergoing a persistent, periodical severe seismic regime, generated by sources of tectonic origin. The strongest earthquakes occurring in our country are of an intermediary, subcrustal (70<H<170 km) type, having active focuses and standing for seismic phenomena unique throughout the world due to their strength, the geometric, kinematic and dynamic characteristics of their focuses and to their generating mechanism. This type of earthquakes is of utmost importance within the total number of earthquakes occurring on the territory of our country, having also the strongest intensities. Masonry construction is commonly employed in Romania and a large portion of the supporting elements in building structures consists of this material. Most of these structures are not aseismic designed, the elements are nor fit to transfer the earthquake forces and thus they must therefore be post-strengthened. For the evaluation of the resisting capacity to gravitational and seismic actions experimental and numerical methods of investigation were applied. The paper presents the steps followed in postseismic investigation and the strengthening solutions adopted for some masonry buildings, both monumental and usual constructions.
Confined masonry (CM) is a construction system which consists of masonry wall panels enclosed by vertical and horizontal reinforced concrete confining elements. The presence of these confining elements distinguishes CM from unreinforced masonry system and makes this technology suitable for construction of structures in regions subjected to intense seismic or wind actions. CM construction has been used in many countries and regions, and has performed well in past earthquakes. The purpose of the paper is to review past research studies related to the seismic in-plane and out-of-plane behaviour of CM structures. The authors have identified the key design and construction parameters which were considered in past research studies and have performed statistical analyses to establish their influence on the seismic performance of CM buildings. For the purpose of this study the authors have compiled databases of previous experimental studies on CM wall specimens which were used for statistic...