Seismic vulnerability assessment of Portuguese adobe buildings
10 May 2021-Buildings (Multidisciplinary Digital Publishing Institute (MDPI))-Vol. 11, Iss: 5, pp 200
TL;DR: In this paper, a set of 30 ground motion records with bi-directional components were selected, and non-linear time-history analyses were performed until complete collapse occurred, and two novel engineering demand parameters (EDPs) were used, and damage thresholds were proposed.
Abstract: Adobe construction represents 5.3% of the total Portuguese building stock according to the latest National Housing Census. The distribution of these adobe buildings is scattered across the country, with higher density in the central region and in Algarve in the south, where the seismic hazard is highest. A large proportion of these buildings are still in use for residential and commercial purposes and are of historical significance, contributing to the cultural heritage of the country. Adobe buildings are known to exhibit low seismic resistance due to their brittle behavior, thus making them vulnerable to ground shaking and more prone to structural damage that can potentially cause human fatalities. Three buildings with one-story, two-stories, and two-stories plus an attic were numerically modeled using solid and contact elements. Calibration and validation of material properties were carried out following experimental results. A set of 30 ground motion records with bi-directional components were selected, and non-linear time-history analyses were performed until complete collapse occurred. Two novel engineering demand parameters (EDPs) were used, and damage thresholds were proposed. Finally, fragility and fatality vulnerability functions were derived. These functions can be used directly in seismic risk assessment studies.
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TL;DR: The seismic performance assessment of buildings is a challenging process as mentioned in this paper, and the seismic performance of buildings can be classified into three categories: seismic performance, seismic performance and seismic performance degradation.
Abstract: The seismic performance assessment of buildings is a challenging process [...]
169 citations
TL;DR: In this article, the authors focus on unstabilized rammed earth (RE), which is locally available material with low embodied energy, and provide a comparative summary of experimental research conducted on walls and buildings to assess their seismic performance.
Abstract: Earthen architecture has a significant share in the world’s fund of both residential architecture and cultural heritage. It provides a home to more than half of the world’s population and can be found in seismically active areas. Empirically acquired knowledge on building with rammed earth (RE) has usually been passed down from generation to generation by word of mouth, with no written scientific grant for the load-bearing capacity and resistance of structural elements. Today, many countries still do not have standards for the design of RE structures. In the development of new as well as existing design standards, the results of experimental research play a significant role. The focus of this study was on unstabilized RE, which is locally available material with low embodied energy. This paper elaborates experimental campaigns, within which meticulous techniques were employed to provide new knowledge on RE for use in earthquake-prone areas. Furthermore, this paper includes: (i) ranges of values of mechanical properties determined on RE specimens from all over the world; (ii) a comparative summary of experimental research conducted on walls and buildings to assess their seismic performance; (iii) an overview of standards and testing methods used in experiments; and (iv) recommendations for further research.
5 citations
TL;DR: In this article , a technology for improving the seismic performance of a modified adobe-brick-masonry composite wall with a wooden-construction center column is proposed, which uses modified mud, a wooden center column, steel-wire mesh, and nylon ropes to reinforce the wall.
Abstract: Damage to adobe constructions might occur due to a long wall and a lack of effective restraint in the middle of the wall, causing it to collapse under an earthquake. Aiming at these problems, a technology for improving the seismic performance of a modified adobe-brick-masonry composite wall with a wooden-construction center column is proposed. It uses modified mud, a wooden center column, steel-wire mesh, and nylon ropes to reinforce the wall. On this basis, four specimens of composite wall and one specimen of modified adobe wall were subjected to proposed quasistatic, cyclic in-plane loading tests to study their failure modes and seismic performance indicators. The results show that the failure modes of all walls were shear failure. The difference is that the modified adobe wall had horizontal cracks in the middle, whereas the composite walls were largely intact. Moreover, the composite walls relied on the modified mud to improve the seismic bearing capacity of each wall. They relied on the center column and the tie materials to form a second line of defense that would increase the wall ductility and collapse residual area. As a result, the phenomenon that caused wall damage and stiffness degradation was lessened.
TL;DR: In this article , the uniaxial compressive mechanical properties of earth materials are tested, and the effects of four influencing factors, such as shape, size, curing age, and loading rate, on the strength, damage pattern, and stress-strain curve of the specimens are analyzed.
Abstract: In this study, the uniaxial compressive mechanical properties of earth materials are tested, and the effects of four influencing factors, such as shape, size, curing age, and loading rate, on the strength, damage pattern, and stress-strain curve of the specimens are analyzed. The standard uniaxially compressed specimen size and the recommended loading rate are proposed for the earth specimens. The uniaxial compressive constitutive equations of earth materials are modified on the basis of the Illampas constitutive equation. By fitting the results of this study and typical literature tests, the applicability of the modified constitutive equation form to the uniaxial compressive test curves of soils in different regions of China based on standard sizes is verified. Finally, the formulae for calculating the parameters related to the constitutive equation of earth materials are established. In its application, only the compressive strength of 100-mm-cubic standard specimens with a curing age of 28 d needs to be measured to calculate and determine the specific values of the relevant parameters of the constitutive equation. This is a good reference value for promoting the development of computational analysis methods for earth structures and promoting the engineering design applications of earth structures.
References
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TL;DR: Incremental dynamic analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads as mentioned in this paper, which involves subjecting a structural model to one or more ground motion record(s), each scaled to multiple levels of intensity, thus producing one (or more) curve(s) of response parameterized versus intensity level.
Abstract: Incremental dynamic analysis (IDA) is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. It involves subjecting a structural model to one (or more) ground motion record(s), each scaled to multiple levels of intensity, thus producing one (or more) curve(s) of response parameterized versus intensity level. To establish a common frame of reference, the fundamental concepts are analysed, a unified terminology is proposed, suitable algorithms are presented, and properties of the IDA curve are looked into for both single-degree-of-freedom and multi-degree-of-freedom structures. In addition, summarization techniques for multi-record IDA studies and the association of the IDA study with the conventional static pushover analysis and the yield reduction R-factor are discussed. Finally, in the framework of performance-based earthquake engineering, the assessment of demand and capacity is viewed through the lens of an IDA study. Copyright © 2001 John Wiley & Sons, Ltd.
3,334 citations
TL;DR: A comprehensive review of the existing modeling strategies for masonry structures, as well as a novel classification of these strategies are presented, which attempts to make some order on the wide scientific production on this field.
Abstract: Masonry structures, although classically suitable to withstand gravitational loads, are sensibly vulnerable if subjected to extraordinary actions such as earthquakes, exhibiting cracks even for events of moderate intensity compared to other structural typologies like as reinforced concrete or steel buildings. In the last half-century, the scientific community devoted a consistent effort to the computational analysis of masonry structures in order to develop tools for the prediction (and the assessment) of their structural behavior. Given the complexity of the mechanics of masonry, different approaches and scales of representation of the mechanical behavior of masonry, as well as different strategies of analysis, have been proposed. In this paper, a comprehensive review of the existing modeling strategies for masonry structures, as well as a novel classification of these strategies are presented. Although a fully coherent collocation of all the modeling approaches is substantially impossible due to the peculiar features of each solution proposed, this classification attempts to make some order on the wide scientific production on this field. The modeling strategies are herein classified into four main categories: block-based models, continuum models, geometry-based models, and macroelement models. Each category is comprehensively reviewed. The future challenges of computational analysis of masonry structures are also discussed.
238 citations
TL;DR: In this article, a rational method is proposed that defines the capacity of a building class by relating its deformation potential to its fundamental period of vibration at different limit states and comparing this with a displacement response spectrum.
Abstract: Earthquake loss estimation studies require predictions to be made of the propor- tion of a building class falling within discrete damage bands from a specified earthquake demand. These predictions should be made using methods that incorporate both computa- tional efficiency and accuracy such that studies on regional or national levels can be effec- tively carried out, even when the triggering of multiple earthquake scenarios, as opposed to the use of probabilistic hazard maps and uniform hazard spectra, is employed to real- istically assess seismic demand and its consequences on the built environment. Earthquake actions should be represented by a parameter that shows good correlation to damage and that accounts for the relationship between the frequency content of the ground motion and the fundamental period of the building; hence recent proposals to use displacement response spectra. A rational method is proposed herein that defines the capacity of a building class by relating its deformation potential to its fundamental period of vibration at different limit states and comparing this with a displacement response spectrum. The uncertainty in the geometrical, material and limit state properties of a building class is considered and the first- order reliability method, FORM, is used to produce an approximate joint probability density function (JPDF) of displacement capacity and period. The JPDF of capacity may be used in conjunction with the lognormal cumulative distribution function of demand in the classi- cal reliability formula to calculate the probability of failing a given limit state. Vulnerability curves may be produced which, although not directly used in the methodology, serve to illus- trate the conceptual soundness of the method and make comparisons with other methods.
215 citations
TL;DR: In this paper, the static pushover 2 incremental dynamic analysis (SPO2IDA) is used to estimate the seismic demand and capacity of first-mode-dominated multidegree-of-freedom systems in regions ranging from near-elastic to global collapse.
Abstract: Introducing a fast and accurate method to estimate the seismic demand and capacity of first-mode-dominated multidegree-of- freedom systems in regions ranging from near-elastic to global collapse. This is made possible by exploiting the connection between the static pushover ~SPO! and the incremental dynamic analysis ~IDA!. While the computer-intensive IDA would require several nonlinear dynamic analyses under multiple suitably scaled ground motion records, the simpler SPO helps approximate the multidegree-of-freedom system with a single-degree-of-freedom oscillator whose backbone matches the structure's SPO curve far beyond its peak. Similar methodologies exist but they usually employ oscillators with a bilinear backbone. In contrast, the empirical equations implemented in the static pushover 2 incremental dynamic analysis (SPO2IDA) software allow the use of a complex quadrilinear backbone shape. Thus, the entire summarized IDA curves of the resulting system are effortlessly generated, enabling an engineer-user to obtain accurate estimates of seismic demands and capacities for limit-states such as immediate occupancy or global dynamic instability. Using three multistory buildings as case studies, the methodology is favorably compared to the full IDA.
183 citations
TL;DR: In this paper, a Bayesian take on the cloud analysis is presented, which manages to take into account both record-to-record variability and other sources of uncertainty related to structural modelling.
Abstract: Cloud Analysis is based on simple regression in the logarithmic space of structural response versus seismic intensity for a set of registered records. A Bayesian take on the Cloud Analysis, presented herein, manages to take into account both record-to-record variability and other sources of uncertainty related to structural modelling. First, the structural response to a suite of ground motions, applied to different realizations of the structural model generated through a standard Monte Carlo, is obtained. The resulting suite of structural response is going to be used as “data” in order to update the joint probability distribution function for the two regression parameters and the conditional logarithmic standard deviation. In the next stage, large-sample MC simulation based on the updated joint probability distribution is used to generate a set of plausible fragility curves. The robust fragility is estimated as the average of the generated fragility curves. The dispersion in the robust fragility is estimated as the variance of the plausible fragility curves generated. The plus/minus one standard deviation confidence interval for the robust fragility depends on the size of the sample of “data” employed. Application of the Bayesian Cloud procedure for an existing RC frame designed only for gravity-loading demonstrates the effect of structural modelling uncertainties, such as the uncertainties in component capacities and those related to construction details. Moreover, a comparison of the resulting robust fragility curves with fragility curves obtained based on the Incremental Dynamic Analysis shows a significant dependence on both the structural performance measure adopted and the selection of the records.
178 citations