Seismic behavior of two Portuguese adobe buildings: part II —numerical modeling and fragility assessment

Considering the likely unfavorable behavior under seismic action of adobe construction, this article aims at providing a seismic fragility characterization of two adobe Portuguese traditional buildings, using numerical models calibrated over experimental results. The study of such two case-study buildings in the region of Aveiro contributes to the understanding of the seismic fragility of adobe construction in the region in general. The buildings were numerically modeled to estimate their structural behavior under seismic loading using adobe material properties that were calibrated based on the experimental results of a cyclic in-plane test of a full-scale double-Tshaped adobe wall. The method chosen to characterize adobe masonry and model its nonlinear behavior followed a total strain crack-based macro-modeling (TSCM) approach, whereas pushover analysis was carried out to reproduce the pseudo-static experimental test in order to enable a refined calibration of adobe masonry mechanical properties. Fragility functions were then derived, based on the above-mentioned numerical models, using nonlinear static analysis, bringing further insight on the seismic fragility of traditional Portuguese adobe construction.     

Seismic behavior of two Portuguese adobe buildings: Part I - in-plane cyclic testing of a full-scale adobe wall

This article addresses the laboratory testing of a full-scale double-T shaped adobe wall, under in-plane horizontal cyclic loading of increasing amplitude, with the aim of contributing to the understanding of the seismic behavior of adobe structures. The wall was built with lime adobes taken from an existing building and mortar with a traditional composition. The behavior of the wall was assessed in terms of: shear stress versus horizontal drift and moment versus rotation relationships; maximum lateral strength; drift and rotation at peak stress; evolution of stiffness, lateral displacements, dissipated energy, and natural frequency; and damage pattern. The wall exhibited brittle behavior and in-plane strength corresponding to 56% of the vertical load. Cracking was observed with an X-shaped pattern whereas no sliding occurred at its base. This research supported the subsequent development of a repair and retrofit solution and also of numerical models to simulate the seismic behavior of two adobe buildings.     

Seismic Retrofitting Techniques for Historic Adobe Buildings

This article presents a comprehensive overview of the techniques available for the seismic retrofitting of adobe buildings. It analyzes these techniques’ viability from a structural engineering standpoint and evaluates their suitability in the context of historic preservation. Analysis was based on an exhaustive review of studies addressing retrofitting techniques of earthen structures, as well as consultation with field experts. The guiding principles of conservation relating to the structural reinforcement of monuments were taken into account. Traditional techniques that enhance the stability of the building, such as wooden ring beams, wooden ties interconnecting parallel walls, corner keys, and the addition of buttresses were found to be effective solutions since they employ compatible and low-cost materials such as earth and wood. When these techniques prove insufficient, minimally invasive measures such as introducing a plywood diaphragm, horizontal steel rods, a geomesh covered with mud rendering or a strapping system can be appropriate.     

Predictive Tri-Linear Benchmark Curve for In-Plane Behavior of Adobe Walls

In the present study, numerical simulations are conducted to estimate the in-plane response of adobe walls subjected to pseudo-static cyclic loading based on the finite element code ABAQUS. The simplified micro-modeling approach is adopted and an interface model reported in ABAQUS material library is applied as material model for zero-thickness interface elements. The comparison between obtained results and field test data results in good agreement. Parametric studies are carried out to evaluate the effectiveness of independent parameters changes on response of adobe walls. It is noted that mechanical properties of joints and adobe units play an active role on in-plane behavior of walls. A tri-linear benchmark curve is proposed to predict the response of aforementioned walls. In this regard, a statistical study is performed to derive the predictive tri-linear benchmark curve. The regressive analysis on 59 numerical models resulted in proposing predictive models. Finally, by comparing tri-linear curves obtained from the regressive analysis, numerical analysis, and experimental study, appropriate accuracy of theoretical model can be found.     

Seismic performance of historical vaulted adobe constructions: a numerical case study from Yazd,Iran

Past earthquakes have demonstrated that historical vaulted adobe buildings are highly vulnerable to seismic actions. Hence, it is crucial for such building typologies to be evaluated in terms of seismic capacity. To this end, this article deals with the seismic performance of historical vaulted adobe houses from the city of Yazd, Iran as one of the seismically active areas of the world and possessing a very rich adobe heritage. Thus, and based on a detailed geometrical survey, a representative sample of adobe houses from Yazd was studied using a simplified in-plane analysis based on three geometric indexes. Concerning the out-of-plane behavior, a deeper assessment was conducted by performing a numerical study, where the main influential parameters on the seismic behavior of vaulted adobe buildings were considered. The numerical analyses were carried out by adopting the limit analysis theory implemented in the Block2D software. The results obtained indicate the safe in-plane behavior of most of the houses and the safe out-of-plane response of the sample under gravitational loads. However, the sample out-of-plane safety under earthquake-induced loads seems to be a matter of concern.     

民居中的奇迹——福建的土楼

土楼是福建西南部以永定为中心的客家人的民居。这种民居非常特殊,有方形、园形。多为四层,中间为庭院。居民多属同族、同宗、同姓。它是北方因战乱而南迁的移民带来的。在东汉以后。北方战乱,大姓士绅多聚居建成坞壁,作为保护自己。客家人南迁到福建西南,在少数民族与荒野之中,也采取这种形式建筑以适应防守需要。永居的土楼在当地环境亦有发展,特别是园形土楼,形成独特形式。由于客家人聚族迁移此地,土楼既适应其特殊环境,而且也进一步促进了客家人以耕读为中心的强大内聚力的文化的发展。因此,土楼既是客家文化的一种外在景观,又是其文化内涵的外在条件。     

The Use of Adobe in the Mormon Cultural Region

The distinctiveness of the Mormon culture region has been described by several authors. One of the items which contributes to this distinctiveness was the widespread use of adobe (sun-dried brick) in relic buildings in the region. The process of adobe making was diffused from Spanish settlements in the American Southwest, and highly modifed by the Mormon builders in the Great Basin. Adobe was initially used in almost all forms of construction because of limited timber for construction and fuel to kiln-dry bricks. Advent of the railroad prompted construction of lines to open coal mines providing a cheap fuel for brickmaking. With low-cost kiln-dried brick, adobe was rapidly replaced as a building material. Thousands of the original adobe structures still remain, however, and constitute an important element in the landscape of the region. Existing adobe structures are normally plastered over, but the distinctive architectural styles associated with the period when most were constructed make them easily recognizable.     

Preventive Intervention for a Group of Buildings in the Historic Centre of Manresa (Barcelona)

The preservation of old downtowns has become a necessity of growing interest. New urban policies have been approved in different countries in order to revive the old city centers and make them economically sustainable. In this global trend, the municipality of Manresa (Barcelona) developed an important urban planning operation in the old district that included the demolition of a group of existing buildings and the construction of a new modern one in close proximity to a group of old residential buildings which are cultural heritage of the city. As a consequence, specific areas of risk were generated which lead to the adoption of precautionary measures to ensure safety. This article presents the preliminary analysis, diagnostics and monitoring carried out on this group of heterogeneous old buildings, as well as the results and precautionary measures taken to ensure their safety. The article also provides a translatable methodology that combines qualitative and quantitative aspects.     

The devolution of mudbrick: ethnoarchaeology of abandoned earthen dwellings in the Bolivian Andes

This ethno-geoarchaeological study considers the formation of archaeological deposits through a study of abandoned contemporary mudbrick structures on the Taraco Peninsula, Bolivia. The study site was a domestic compound with rooms for different functions that had been abandoned for over 50 years. Structures were in variable states of decay in terms of roof cover, walling integrity and abandonment fills. Geoarchaeological samples were collected from intact and weathered adobes, earthen hearths, mud plaster, and flooring. Adobes and mud plaster were locally derived from topsoil containing archaeological sediments with added gravel and plant temper. This study found a relatively light anthropogenic signature for decayed earthen houses.Rising damp exfoliated mud plaster despite un-mortared cobble wall foundations. Organic matter from roof fall attracted thriving soil faunal populations, which furthered site destruction through bioturbation, particularly packed earth floors. Sediments derived from weathered mudbrick retained little evidence of prior use as construction materials unless exposed to heat. Sediments exposed to high-temperatures produced the most distinctive rubified features but were structurally compromised. Isolated thermal features from decomposed adobe would not be distinguishable from other hearth types. Adobes exposed to low or moderate heat had few distinctive features in thin section. Intact adobes and floors that were not exposed to heat have fewer pores than natural sediments and distinctive grass inclusions. These adobes disarticulated into loose sediments when exposed to weathering. Adobe fall outside the crumbling structures blended into topsoil.This study sheds light on functional attributes of pre-Columbian construction practices. Thick, fine-textured sterile flooring is commonly encountered in the study region. This would control bioturbation from roof fall in a previous occupation enabling reconstruction in abandoned dwellings. In contrast to the contemporary dwelling, prehistoric mortared cobble foundations would resist rising damp. Cobbles without mortar may relate more to design and construction than durability. These contrasts between contemporary and prehistory construction practices reflect differences in the design, construction costs and functional use-life of adobe structures.     

Assessment of Construction Techniques and Material Usage in İzmir Rural Houses

The domestic architecture in the rural villages of ?zmir comprises a unique built environment with their masonry wall textures, semi-open sofas, round tiled-hipped roofs, and chimneys, and represents an important part of the cultural and architectural heritage. This assessment is mainly based on field observations that focus on the architectural and structural layout of intact, damaged, and destroyed houses. During field observation and the analysis of data certain plan typologies and relationships between the geological formations of the region and choice of materials and construction techniques were observed. While load-bearing masonry and timber skeleton systems are common, extensive use of timber laces, stone, and fired or adobe brick masonry with mud mortar and timber frames infilled with masonry materials were frequently seen. Generally, round timber elements such as wall plates, laces, lintels, posts, and frames of flooring systems are used. Architectural degenerations in authentic houses, defective details and partially due to the earthquake-prone nature of the region seismicity have been evaluated. An overall approach for the preservation and sustainability of this heritage is suggested.     

The preservation of exposed mudbrick architecture in Karanis (Kom Aushim), Egypt

Excavations in the arid regions of Egypt provide insight into the many types and uses of mudbrick architecture. Upon exposure the inherently unstable building material decays rapidly, resulting in severe loss or complete destruction of once well-preserved buildings. The preservation of mudbrick structures is relatively complicated and expensive. Research has focused on the circumstances that enable preservation and the influence of climate and weather over time. Conservation treatments should address these two processes as soon as possible after exposure of the structures. Our assessment of a range of conservation methods leads to the conclusion that reburial is among the least objectionable method of preservation, despite its drawback of returning the excavated buildings to a situation where they are invisible to both researchers and the public.     

Mine blast vibration response spectrum for structural vulnerability assessment: case study of heritage masonry buildings

Ground-borne vibrations induced by mine blasting are typically of low amplitudes, which are not considered a major concern for modern engineered structures. However, historic structures are often considered more vulnerable due to inadequate knowledge regarding the state of construction materials and structural response. Specifically, the construction materials used might be fragile or have deteriorated to a stage that could be vulnerable to such vibrations. Simplistic rule based on peak ground motion parameter has been adopted worldwide for safety assessment, while the frequency characteristics of vibrations are not taken into account. Further, there is very limited study on response of heritage structures to near-field blasting. This article presents a practical structural vulnerability assessment method for mine blast-induced vibrations. In particular, a design response spectrum model is proposed based on close range measurements of nearby mine blasting, which is compared with an existing design spectrum model for far-field mine blasts and a typical design spectrum model for earthquake actions. The method is illustrated through a case study of heritage masonry buildings in Australia. The unique blast data presented and the generalized methodology would be useful to both structural engineers and blast engineers in considering potential effects of blasting on heritage structures.     

Middle east architectural traditions in golden horde mansion construction

The article deals with the largest mansion-type buildings in the Golden Horde towns of the Lower Volga region. These buildings had many rooms and walls made of hard-burned and adobe bricks. A large ceremonial hall was located at the center of the building; vestibule premises were located adjacent to the hall on the northern and southern sides; residential and utility rooms occupied the eastern and the western wings. Golden Horde mansions are compared with the palaces and mansions of China, Mongolia, and the countries of the Middle East. The infl uence of the architectural traditions of these countries led to the emergence of an original building type based both on a typical Western Central Asian layout, and principles of organizing space borrowed from Eastern Central Asia.     

In Situ Characterization of Rammed Earth Wall Renders

The Algarve region in southern Portugal has one of the most significant rammed earth construction legacies in the country. This construction method is characterized by its high susceptibility to water damage and external renderings are essential to the longevity of these constructions. This study collects and organizes data that provides the basis for the conservation and repair of renderings. Five earth buildings from western Algarve were selected to represent this heritage and its diversity of composition and susceptibility to water damage. Some of their commonest anomalies result from the interaction between the earth substrate and the traditional external renderings, given their distinct characteristics and behavior. The selected sample is described and the mechanical strength of the rammed earth walls and their renderings are evaluated through in situ tests. Samples of the external renderings and earth substrate of the five buildings comprising the sample were also collected and characterized in the laboratory. The characteristics of these two materials and their behavior as an assembly were analyzed. The results of the in situ and laboratory tests are compared and the viability of using a method based on in situ tests for the wider characterization of the type of construction under analysis evaluated.     

Historical Survey and Chronology of Bonajuto Chapel in Catania,Italy

Located in the historical center of Catania, Italy, in the Civita district, the Bonajuto Chapel is one of the oldest and best-conserved buildings of the city, which has survived the numerous earthquakes that struck eastern Sicily during the medieval and the modern ages, such as those particularly devastating in 1169 and 1693. However, both the date of this small monument, as well as its original use, still remain uncertain, as literary and documentary evidence are scarce and fragmentary. Most historians, analyzing prevalently the stylistic and constructive aspects, interpreted the chapel as a place of worship and assigned its construction to a rather long period of the early Middle Ages, from the 5th or 6th centuries ad to the 8th or 9th centuries ad—the phase during which the island was under the Byzantine domination. The excavations carried out in 1930 to 1939 and the last restoration works (in 2003) have not provided explicit chronological data. Its age determination is considered essential for a better knowledge of the real influence of this domination on the architecture of the Island. Therefore, a multidisciplinary and accurate analysis of the building using the existing bibliography has been carried out also in order to understand the functional and morphological transformations of the chapel during its long life. The thermoluminescence absolute dating methodology applied to some brickwork elements of the construction, has placed the monument chronology in a period of time that is notably shorter than that previously noted here. These new data, with the study of the architectural structure, have made a significant step forward in the knowledge of the chapel history.     

明清古建筑木结构典型抗震构造问题研究

为保护古建筑,采用分类统计方法,研究了我国明清古建筑木结构的典型抗震构造问题。基于大量工程现场勘查结果,对古建筑木结构的典型抗震构造问题进行了归纳汇总,分析了原因,提出了加固建议;基于典型算例,对古建筑木结构加固方法进行了深入论证。结果表明:我国古建筑木结构的柱子、斗棋、榫卯节点、梁架、屋顶等各部位都容易产生开裂、糟朽、变形、拔榫等抗震构造问题并影响结构的抗震性能,而这些问题的产生原因主要与木结构的构造特征、木材材料性质及施工保养等因素有关;对这些抗震构造问题及时采取合理有效的加固措施,可减轻或避免结构产生的震害。     

Establishment of conservation,design and construction criteria for protective shelters at Fort Selden State Monument,New Mexico

Abstract

Foit Selden State Monument, located in southern New Mexico, consists of the exposed adobe ruins of a military post that was occupied from 1865 to 1981. A management plan for the site is currently being developed in which an option being considered for preservation is the construction of a protective shelter.

The process of establishing conservation, design and construction criteria for a potential shelter at Fort Selden involves the assessment of technical issues and the evaluation of public support for the criteria and purpose of the monument. The conservation concerns are based upon accepted standards for conservation and construction criteria while the design and construction standards involve a higher degree of Public concern, particularly the public expectations exerted on a historic site in the United States.

The criteria for Fort Selden are currently being codified. This paper outlines the preliminary criteria as well as the process by which these criteria will be established and meshed with the public expectations of the site. The planning process is presented and the underlying philosophies of deciding to shelter, designing the shelter and constructing the shelter. Future evaluations of the shelter's success can be gauged against these original criteria and mindset.     

Modernist Unreinforced Masonry (URM) Buildings of Barcelona: Seismic Vulnerability and Risk Assessment

The main objective of this work is to assess the vulnerability and seismic risk of typical existing modernist unreinforced masonry (URM) modernist buildings and aggregates situated in the Eixample district of Barcelona, part of the architectural heritage of the city. The context of the analysis is the methodology proposed by the Risk-UE project. The buildings are characterized by their capacity spectrum and the earthquake demand is defined by the 5% damped elastic response spectrum, considering deterministic and probabilistic earthquake scenarios. A discussion addresses the basis of the seismic damage states probabilities and the calculated damage index. An important research effort has been focused on the buildings modeling. All the architectural elements and their mechanical properties have been studied and evaluated accurately. It has been evidenced that a detailed and complete knowledge of all the structural elements existing in this type of buildings influence directly their behavior and hence the calculations and the results. The analysis of the isolated buildings and of the aggregate building has been performed for both mentioned seismic scenarios. Finally, a complete discussion of the results is included.