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Assessment of combined in-plane and out-of-plane fragility functions for adobe masonry buildings in the Peruvian Andes
(Frontiers Media S.A., 2020-05-01)
In the city of Cusco and in other parts of Peruvian andes, adobe masonry is the primarily construction material. Adobe continues being used for the construction of housing due to its low cost, its thermal properties, the use of unskilled labor as well as the local traditions of the Peruvian highlands. The Peruvian National Statistics Office (INEI) estimates that 67% of rural housing in Cusco is made of adobe masonry. Besides, previous seismic events and laboratory tests demonstrated that adobe dwellings without reinforcement are prone to collapse during an earthquake. Therefore, seismic vulnerability assessment of this type of dwellings is necessary aiming at developing proper contingency and mitigation risk policies. Then, fragility curves constitute a key tool when conducting seismic loss assessment since they provide information regarding the probability of exceeding a certain damage Limit State (LS) as a function of a given engineering demand parameter. This work aims at developing fragility curves, combining in-plane and out-of-plane loading conditions, for typical adobe buildings located in the city of Cusco. Initially, a set of one and two-story adobe houses were studied to determine the geometrical characteristics of representative local building typologies. Subsequently, 1000 artificial buildings were generated by means of Monte Carlo simulation based on the information gathered. The structural capacity of each artificial building was represented by simplified bilinear and trilinear capacity curves for in-plane and out-of-plane mechanisms, respectively. In order to represent the characteristics associated with subduction processes a set of ground motion records was established. The damage state of each building was assessed for each seismic record, and this information was collected into a Probability Damage Matrix (DPM). Finally, fragility curves were fitted for each damage state of the cumulative DPM. Preliminary results show that one and two-story adobe dwellings have a probability of collapse of 30% and 60%, respectively, when considering a peak ground acceleration (PGA) of 0.30 g, which corresponds to the expected acceleration related to a return period of 475 years over a soil type 2 according to the Peruvian Standards.
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Numerical analysis of bonding between masonry and steel reinforced grout using a plastic–damage model for lime–based mortar
(Elsevier, 2020-11-30)
This paper shows a numerical investigation with single-lap shear bond tests between Peruvian brick masonry and SRG system. For this purpose, the finite element method, elements and constitutive models implemented in ABAQUS library were used. Eight-node continuum elements were employed for modelling mortar, masonry and steel fibers assuming a linear-elastic behaviour for the last two materials. Eight-node cohesive elements with zero-thickness were used to model substrate-mortar and steel-mortar interfaces. Due to experimental results showed the detachment of the steel fiber from the mortar accompanied by cracking of the outer mortar layer, the non-linearity of the mortar was also considered by using a Concrete Damage Plasticity constitutive model. The effect of the mortar non-linearity was compared with other models assuming a linear and rigid material for mortar, as recommended by literature. This shows that modelling a non-linear mortar leads to more accurate results for future design and strengthening purposes, thus, its implementation is encouraged. A comparison in time between Bond–Slip Law (BSL) at steel–mortar interface and mortar constitutive law is analysed in order to investigate the stress-transfer mechanism during single–lap shear tests.
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Mechanical characterization of adobe masonry
(Springer Nature, 2021-01-01)
The characterization of the mechanical properties and behaviour of adobe masonry is fundamental for the understanding of the structural behaviour of adobe constructions. Thus, in the last decades, experimental studies focused on this topic have been carried out by different authors. Many of the existing experimental works, however, were carried out aiming to support broader studies focused on the seismic behaviour of adobe constructions and are not very detailed. Moreover, authors tend to adopt different procedures in their experimental work, since there are few indications in existing standards for testing adobe masonry. The wide variety in materials used, both for the adobes and mortars, further complicates this work, making it difficult to compare results obtained in different studies. This chapter provides an overview of the indications given by standards and other technical recommendations for the mechanical testing of adobe masonry. It presents a review of existing research on the mechanical behaviour of adobe masonry, addressing studies that focus on: (i) compression behaviour, (ii) shear behaviour, (iii) joint shear behaviour. It provides a global analysis of the existing knowledge, suggesting improvements for normative documents and identifying future research needs.
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Mechanical characterization of adobe bricks
(Springer Nature, 2021-01-01)
The mechanical characterization of adobe bricks is an important first step in the study of the behaviour of adobe masonry. For this reason, in the last decades, different authors have conducted research on the mechanical behaviour of adobes from various regions of the world. Despite the importance of mechanical characterization, there are still only a few standards and normative documents with clear indications for the mechanical testing of earthen materials and, in general, these indications are not thorough and vary among different countries. Consequently, authors tend to adopt different types of test specimens and procedures in their experimental work, thus obtaining results that are not directly comparable. The fact that the materials and procedures traditionally used are also not standardized, varying greatly from region to region, also contributes to the difficulty of comparing results from different studies. This chapter presents a review of the indications provided by codes, standards and other technical recommendations for the mechanical testing of adobe bricks, as well as a detailed review of procedures adopted, and results obtained by different authors regarding the mechanical characterization of traditional adobe bricks. This chapter focuses, in particular, on the behaviour of adobe bricks when subjected to simple compression. It provides an overview of the existing knowledge and identifies needs for future research and development.
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Numerical modelling of adobe structures
(Springer Nature, 2021-01-01)
Numerical assessment of adobe structures allow several drawbacks of experimental testing to be overcome, either to carry out back-analyses or to predict the seismic performance of real constructions. Among a number of modelling strategies, this chapter presents the main features of the finite element method, discrete element method and equivalent frame method, discussing their implementation in the case of adobe constructions. Pros and cons of each modelling approach are identified in view of real-world applications. Recent developments are discussed and research needs are detected for future studies.
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Shaking table testing of adobe masonry structures
(Springer Nature, 2021-01-01)
This chapter presents the seismic simulation systems (shaking tables) as essential resources for experimental research on adobe masonry structures. An overview of selected relevant shaking tables existing in laboratories around the world gives an idea of the broad testing scope possible with this type of equipment. Its use in testing of adobe masonry structures goes back to 1986 at the University of California at Berkeley and to 1988 at the Pontifical Catholic University of Peru (PUCP). Shaking table testing has been considered the experimental technique that may closest reproduce the real behaviour of an adobe structure during earthquakes. After the description of a typical shaking table test procedure, based on more than thirty years of PUCP experience, some seismic simulation tests on adobe masonry structures performed in different countries are briefly described. Each case presents the basic characteristics of the shaking table and some qualitative results obtained to understand the seismic behaviour of adobe masonry structures.
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Quasi-static in-plane testing of adobe masonry walls and structures
(Springer Nature, 2021-01-01)
The lateral seismic capacity and the in-plane failure pattern of adobe masonry may be understood by performing quasi-static experimental tests on full-scale adobe walls. Information regarding the maximum lateral capacity and the displacement ductility are normally obtained during these tests. Also, information about limit states could be obtained. Along the years, universities in Europe, Asia and Latin America have performed this type of tests and the results of some of these works are summarized in this chapter.
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Research developments and needs on seismic performance and strengthening of adobe masonry constructions
(Springer Nature, 2021-01-01)
The significant amount of studies on adobe masonry constructions, which have received growing interest from researchers and practitioners, allows preliminary conclusions on the state-of-the-art to be drawn. Besides, several research needs can be delineated to create the basis for knowledge development and implementation of seismic risk mitigation programmes. Past studies moved from material characterization to structural performance assessment through numerical simulation and experimental testing, as well as seismic strengthening. Future lines of research could focus on test standardisation, non-destructive and minor-destructive testing, full-scale testing to support structural modelling and strengthening, and numerical simulation through discrete element and equivalent frame methods.
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Adobe constructions in the world: a first overview
(Springer Nature, 2021-01-01)
Adobe constructions date back thousands of years and are a significant fraction of the world’s built heritage, including UNESCO sites. Even though adobe dwellings are still built in some regions, a number of experimental and theoretical studies have delineated the vulnerability levels of these constructions. A significant concentration of adobe constructions in regions with moderate-to-high levels of seismic hazard has been observed as well, resulting in huge human losses during earthquakes. Therefore, the knowledge of the structural performance and seismic reinforcement of adobe constructions provides the basis for their structural vulnerability reduction, allowing disaster risk mitigation and community preparedness. This is also a strategic task to meet sustainability and community resilience goals in multiple countries, where guidelines for both existing and new adobe constructions must be implemented. This chapter provides readers with preliminary information on history, worldwide distribution, construction features and observed performance of adobe constructions for different demand scenarios. These topics are recalled and discussed in more detail in subsequent chapters.
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Behaviour of adobe construction in recent earthquakes
(Springer Nature, 2021-01-01)
The adobe masonry is classified as a quasi-brittle material. This is because the material fails under very low tensile stresses. Then, under the action of any type of loading (especially dynamic one), adobe masonry behaviour rapidly changes into nonlinear behaviour. However, adobe masonry resists moderate compressional loading. During earthquake actions, the adobe material starts to fail at the zones of stress concentration, such as corners of openings. Also, vertical cracks at the intersection of two orthogonal walls may appear. This is due to the absence of confinement elements that could guarantee a box behaviour on each floor. If walls continue breaking, then the most probable failure is due to the overturning of walls and the roof collapse. In this chapter, the most common types of failure of adobe buildings are shown and discussed based on field surveys carried out after some earthquakes.

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