Building survey forms for heterogeneous urban areas in seismically hazardous zones. Application to the historical center of Valparaíso,Chile

ABSTRACT

Building survey is an essential data-collection procedure to feed large-scale seismic vulnerability assessment. The available strategies usually consider survey forms to gather information about the urban buildings. The application of the available survey forms poses important challenges for the case of the heterogeneous urban centers including different structural typologies. This work proposes four specific survey forms for traditional structural typologies constructed with masonry, reinforced concrete, mixed steel-reinforced concrete, and timber. The proposed forms request essential information on the parameters necessary for seismic vulnerability assessment, by evaluating the lateral-load resistant system, regularity, condition of conservation, and existing damages. The survey forms were applied to the study of 111 buildings of the historical center of Valparaíso, Chile. The proposed methodology was complemented with the use of Geographic Information Systems to obtain a complete database with the structural characterization of the most representative typologies for future works of large-scale seismic vulnerability assessment.     

Reaction to Fire of Existing Timber Elements Protected With Fire Retardant Treatments: Experimental Assessment

Fire safety is an important issue of building safety, especially when the building’s fire load contents enhance the risks of fire deflagration. When existing timber structures are involved, the most usual way to improve its reaction to fire is to treat wood with fire retardants. This study focuses on the surface protection of existing timber roof structures against fire, through the use of fire retardant (FR) treatments applied on site. An experimental investigation was carried out to study the effect of FR treatments on timber reaction to fire, with a special emphasis on timber members with biological deterioration and previously treated with preservative products. The behaviour and effectiveness of intumescent and non-intumescent treatments was also investigated. The study showed that the application of FR treatments improved the reaction to fire of timber, even in the presence of previous preservative treatments. However, the choice of the specific FR treatment should take into account the substrate conditions. In addition, test results suggest that protection systems involving multi layers (intumescent and non-intumescent) with different functioning modes each are likely to have a good global performance on the protection of timber elements against fire.     

上下椽头尾搭接的木构古建筑受力性能的简化计算方法研究

古建筑木结构主要分为抬梁木构体系和穿斗木构体系,其结构布置与连接节点明显不同于现代木结构。为了进一步提高古建筑木结构的结构计算和结构安全评估的工程实用性,对常见木椽的受力性能简化算法、常见拼合檩条的受力性能简化算法、三架梁和五架梁受力性能的简化算法进行研究,并基于动力特性分析,初步提出古建筑木结构典型构架体系在进深方向和面阔方向结构基本自振周期的近似计算模型。研究成果可为古建筑木结构的结构性能计算、结构安全评估以及加固修缮设计提供依据和参考。     

Structural Assessment of Ancient Masonries before and during a Rehabilitation Process

ABSTRACT

The rehabilitation of old buildings requires detailed knowledge of the mechanical characteristics and stress state of the structural elements, which play an important role in the intervention process. In this sense, non-slightly destructive tests can estimate structural characteristics with good precision at relatively low costs. Consequently, this article presents a device, based on the flat jack technique, applied to continuous stress monitoring over time. It also focuses on the onsite determination of service stresses and its continuous monitoring in several masonry buttresses of a historic building, as well as the assessment of the structural safety before, during, and after an intervention process. A brief analysis of the research is performed, and the motivation and the methodology adopted are described. Finally, the evolution of the measurements recorded and the analysis of the results achieved are detailed. The study enabled recommendations to be made to the intervening agents that guarantee structural safety.     

Seismic Risk Assessment and Mitigation at Emergency Limit Condition of Historical Buildings along Strategic Urban Roadways. Application to the “Antiga Esquerra de L’Eixample” Neighborhood of Barcelona

ABSTRACT

This article presents a management tool for the large-scale assessment and mitigation of the seismic risk of urban systems. The research introduces a new perspective for a scientifically tackled holistic approach. The proposed methodology considers multiple objectives, from the identification of the most vulnerable buildings whose collapse may hinder the operationality of strategic urban roadways after the occurrence of an earthquake, up to the proposal of proper interventions to improve their functionality. The approach uses a performance-based approach founded on the concept of urban Emergency Limit Condition. Plotting maps of geo-referenced scenarios by means of GIS software have revealed to be extremely useful to detect the weak points of the urban network and to plan suitable strategies of seismic risk mitigation and appropriate enhancement of reliability. The proposed methodology is applied to the “Antiga Esquerra de l’Eixample” neighborhood of Barcelona that hosts the strategic route to the hospital and is characterized by high levels of seismic vulnerability of existing buildings and exposition of its high-density population.     

Guidelines for On-Site Assessment of Historic Timber Structures

In the scope of European Cooperation in Science and Technology–Wood Science for Conservation of Cultural Heritage (COST IE0601–WoodCultHer) (available at http://www.woodculther.org) it was agreed to produce Guidelines for the Assessment of Historic Timber Structures, covering the principles and possible approaches for the safety assessment of old timber structures of historical relevance that could be used as the basis for possible European Standards, as discussed with CEN/TC346 (Conservation of Cultural Heritage).

This approach was targeted at all those concerned with the conservation of heritage buildings. These guidelines should also help decision-making regarding the need for immediate safety measures. The aim is to guarantee that inspection and assessment measures provide the necessary data for historical analysis, structural safety assessment, and planning of intervention works, while having minimal impact on the building fabric (the original materials, structural systems, and techniques).This article provides information on the criteria to be used in the assessment of load-bearing timber structures in heritage buildings. It covers the preliminary assessment (desk survey, preliminary visual survey, measured survey, structural analysis, and preliminary report), as well as the detailed survey of timbers (with a special emphasis on visual strength grading on site) and carpentry joints. The subsequent diagnostic report and the detailed design of repairs are outside its scope.     

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.     

METHODOLOGY FOR THE PROBABILISTIC ASSESSMENT OF q FACTORS. A DAMAGE INDEX APPROACH

The objective of the present work is to present a methodology for the identification of relevant limit states, namely ultimate limit states leading to structural collapse, and for the assessment of design q factors (or force reduction factors) for reinforced concrete structures under seismic loading. It follows a probabilistic approach based on damage indices. The utilised nonlinear models, as well as the damage indices, which are those proposed by Miner and by Park and Ang, are.described. The methodology of analysis is presented emphasising its probabilistic characteristics. Some parametric studies are carried out, including the analysis of one regular plane frame reinforced concrete structure, designed for three different ductility classes (those proposed by Eurocode 8) and assuming different q factors in design. Results show how the chosen damage indices can be used as parameters to characterise the structural response and how the proposed methodology can be used to assess the design q factors. It is also shown that, for moderate seismic input, the three ductility classes are essentially equivalent in terms of maximum damage indices, but that for higher seismic levels the differences are evident, justifying the use of different q factors.     

基于荷载修正的传统木构建筑构件重要性分析方法研究

传统木构建筑的构件重要性对于整体结构状态的评估具有重要意义,为弄清楚传统木构建筑的构件重要性,开发了一种基于荷载修正的传统木构建筑构件重要性评价程序,基于荷载工况修正与荷载重分布修正重构了荷载分布矩阵,基于荷载施加构件修正改进了构件重要性计算方法。以典型传统木构建筑——保国寺大殿为例进行了数值模拟分析,并基于广义刚度评价了构件重要性,分析了各项修正对构件重要性的影响情况以及最终修正对构件重要性的结果变化率。结果表明:柱类构件的修正变化为-0.526%~2.192%;梁栿类构件的修正变化为-2.638%~50.598%;铺作类构件的修正变化为-12.763%~9.989%;槫类构件的修正变化为-7.586%~6.918%。保国寺大殿构件重要性排序:柱类>槫类>梁栿类>铺作类;修正后柱类、梁栿类重要性提高,铺作类、槫类重要性降低。可为传统木构建筑的结构状态评估和预防性保护提供参考。     

Improving Coastal Vulnerability Assessment Methodologies for Integrated Coastal Zone Management: an Approach from South Australia

The global concern about human-induced climatic change and its potential effect on sea-level has dominated the debate on coastal vulnerability, particularly since a common assessment methodology was developed by the Intergovernmental Panel on Climate Change in 1991. There have been numerous attempts to use or adapt this methodology but the focus has remained on sea-level rise as the single most important issue for coastal vulnerability. This paper presents a revised and more holistic coastal vulnerability assessment methodology which incorporates spatial and temporal scales relevant to the predicted impacts of climatic change and current human-induced hazards. Three studies in contrasting coastal environments of South Australia demonstrate that there are significant regional variations in sea-level response, human-induced hazards and local planning issues and that these may present a greater immediate threat than the possibility of sea-level rise.     

Application of In-Test Model Updating to Earthquake Structural Assessment

Analytical methods are frequently utilized for structural assessment due to their simplicity and cost-effectiveness. However, modeling of material inelasticity and geometric nonlinearity under reversed inelastic deformations is still very challenging and its accuracy is difficult to quantify. On the other hand, realistic experimental assessment is costly, time-consuming, and impractical for large or spatially extended structures. Hybrid simulation has been developed as an approach that combines the realism of experimental techniques with the economy of analytical tools. In hybrid simulation, the structural is divided into several modules such that the critical components are tested in the laboratory, while the rest of the structure is simulated numerically. The equations of motion solved in the computer enable the integration of the analytical and experimental components at each time increment. The objective of this article is to apply a newly developed identification and model updating scheme to acquire the material constitutive relationship from the physically tested specimen during the analysis to two complex hybrid simulation case studies. The identification scheme is developed and verified in a companion article, while the two experiments presented in this article are selected such that they address different structural engineering applications. First, a beam-column steel connection with heat treated beam section is analyzed. Afterwards, the response of a multi-bay concrete bridge is investigated. The results of these two examples demonstrate the effectiveness of model updating to improve the numerical model response as compared to the conventional hybrid simulation approaches.     

Sustainable Tourism Planning and Consultation: Evidence from the Project INTER.ECO.TUR

Expansion of territories targeted by travellers and growth of attendance rates make tourism sector of significant interest for the implementation of policies on environmental protection at the European Union (EU) level. The need to protect local natural heritage, to integrate tourism industry development policies with the ones pertaining to other sectors that characterize a given territory and to enhance the overall environmental performance are some of the priorities that may appear conflicting at times. This paper discusses a method of analysis and planning aiming to promote potential directives of local governance. This method, representing the outcome of a process coordinated and shared across territories, is oriented towards the sustainable development of the area and refers to the implementation of integrated policies, The Interreg Eco Tourism (INTER.ECO.TUR) project, co-financed by the European Commission under the EU's INTERREG IIIC, provided the research with a useful case study to analyse the dynamics of sustainable tourism development within the European Mediterranean area. The debate of its results offers evidences on the possibility to develop such a governance process effectively, providing insight into an assessment methodology enriched by a clear-cut analysis of its applied experiences.     

Knowledge-Based Performance Assessment of Existing RC Buildings

One of the most challenging aspects of the seismic assessment of existing buildings is the characterization of structural modeling uncertainties. Recent codes, such as Eurocode 8, seem to synthesize the effect of structural modeling uncertainties in the so-called confidence factors that are applied to mean material property estimates. The confidence factors are classified and tabulated as a function of discrete knowledge levels acquired based on the results of specific in-situ tests and inspections. In this approach, the effect of the application of the confidence factors on structural assessment is not explicitly stated. This work presents probabilistic performance-based proposals for seismic assessments of RC buildings based on the knowledge levels. These proposals take advantage of the Bayesian framework for updating the probability distributions for structural modeling parameters based on the results of tests and inspections. As structural modeling parameters, both the mechanical material properties and also the structural detailing parameters are considered. These proposals can be categorized based both on the amount of structural analysis effort required and on the type of structural analysis performed. An efficient Bayesian method is presented which relies on simplified assumptions and employs a small sample of structural model realizations and ground motion records in order to provide an estimate of structural reliability. As an alternative proposal suitable for code implementation, the simplified approach implemented in the SAC-FEMA guidelines is adapted to existing structures by employing the efficient Bayesian method. This method takes into account the effect of both ground motion uncertainty and the structural modeling uncertainties on the global performance of the structure, in a closed-form analytical safety-checking format. These alternative proposals are demonstrated for the case study structure which is an existing RC frame. In particular, it is shown how the parameters for the safety-checking format can be estimated and tabulated as a function of knowledge level, outcome of tests, and the type of structural analysis adopted.     

WORKER DISPLACEMENT AND JOB-SEARCH: A REGIONAL ANALYSIS OF STRUCTURAL IMPEDIMENTS TO REEMPLOYMENT*

ABSTRACT. This study investigates the human, and in turn the regional, consequences of industrial restructuring in the United States. Our methodology presumes that labor market outcomes of displaced workers can provide considerable information on the structural properties of local labor markets, and subsequently upon the capacity of such areas/regions to reemploy additional workers. The examination follows two steps. In the first, a multivariate model of reemployment likelihood is developed and subsequently estimated. Separate equations are obtained for various resons of the country, a disaggregation that permits one to identify how postdisplacement reemployment, and its determinants, vary systematically across space. In the second step, the above estimates are decomposed into two elements, one of which is reflective of regional structural conditions. Based upon this methodology and estimates obtained in the first step, regions of the country are compared as to magnitude of their structural economic problems, and thus as to their capacity to gainfully reemploy additional workers displaced by plant closure or relocation.     

基于能量方法的江浙地区抬梁式及穿斗式传统民居木构件重要性分析

为研究中国传统木构建筑的结构构件重要性排序问题,以江浙地区抬梁式和穿斗式两种典型的传统民居木结构类型为研究对象,基于能量方法采用构件属性改变后对结构整体应变能的单位体积改变率作为构件重要性的评价指标,运用有限元软件Ansys(16.0)开发了基于生死单元法和改变弹性模量法的构件重要性评价程序。分析结果表明,改变弹性模量法更适用于中国传统木构建筑的结构构件重要性分析。通过对抬梁式和穿斗式的单榀框架和整体框架在竖向荷载、水平地震荷载两种工况下的结构构件重要性的计算分析,得到了构件的重要性系数和排序,并提取出了抬梁式和穿斗式传统木构的关键构件。研究结果可以为确定传统木构建筑遗产在修缮施工、维护以及结构健康监测过程中需要重点关注的构件提供科学合理的理论依据。     

Making a Mountain Out of a Molehill? A Low-Cost and Time-Efficient Molehill Survey of the Lost Medieval Harbor Site of Monnikerede,Belgium

Grasslands pose a particular problem for archaeological survey involving artifact assessment, as no material is plowed up to the surface. Although finds in molehills are often the only source of information available on sites with such low visibility, an archaeology of molehills has thus far been largely disregarded. Yet, by applying a low-cost and time-efficient methodology, both the potential and the pitfalls of molehill archaeology come to the forefront. At the medieval harbor site of Monnikerede, it was possible to assess material culture and to locate certain structural elements. However, when artifact densities were compared with the underlying geophysical anomalies, a more complex relationship appeared at the level of individual features.     

西藏坚塞颇章宫的结构计算分析

本研究以全国重点文物保护单位西藏罗布林卡三大宫殿之一的坚塞颇章宫为实例,分析藏式古建筑的结构特点,探讨计算分析方法,并针对静力荷载工况和地震组合工况下的结构性能进行了讨论。本研究区别于以往藏式结构的研究方法,主要在于:在计算分析中将墙体建入整体结构模型,考虑墙体对结构的影响;考虑墙体和木柱的“收分”造型的影响;将楼板和屋面的密布木檩等刚度转化为单向板考虑;同时考虑构件已存的变形缺陷影响。计算结果表明:西藏坚塞颇章宫在静力荷载工况作用下,整体状态良好,梁柱墙及节点均满足承载力要求;在地震组合工况作用下,部分柱和墙不满足抗震承载力要求。在地震作用下,该建筑刚度较小的木结构构件首先发生振动。结构薄弱部位是中部四根二层通高木柱。这四根通高木柱长细比较大,刚度较小,一旦发生较大的变形,将直接影响整体结构安全。木柱与墙体之间的变形差异较大,两者变形协调性较差。此外,存在变形缺陷的中部通高木柱所在梁柱节点的抗震承载力不满足要求,应注意加强防护。研究涉及的计算分析方法及相关计算结论对藏式建筑结构的深入研究具有重要的参考价值。     

Design Methodology for Seismic Upgrading of Substandard Reinforced Concrete Structures

This article presents a design methodology for seismic upgrading of existing reinforced concrete (RC) buildings. The methodology is based on the modification of the deflected shape of the structure so as to achieve a near-uniform distribution of interstorey drift along the building height, thereby eliminating damage localization. Yield Point Spectra are utilized for the definition of demand and a direct displacement-based design approach is implemented. The fundamental steps of the method are described in detail, including a systematic evaluation of assumptions and limitations. A full-scale tested structure is used as a case study for assessment and verification of the proposed methodology. Alternative retrofit scenarios are set according to target response and performance levels. The role of the target deflected response shape and its influence on the outcome of the retrofit strategy is investigated. The viability of the alternative retrofit scenarios is studied for different ground motions including near-fault earthquake records.     

Shaking Table Testing of a Full-Scale Prefabricated Three-Story Timber-Frame Building

Shake table tests were carried out on a 7 m × 5 m three-story, timber light-frame building (7.5 m height) at the TreesLab laboratory (Eucentre) in Pavia. The aim of the research was to evaluate the seismic behavior of a typical Italian prefabricated timber building and to study the interaction between the individual structural components tested in quasi-static manner in a previous experimental study. The 1979 Montenegro Earthquake ground motion, recorded at the Ulcinj-Hotel Albatros station, was selected as the ground motion for seismic tests. The maximum peak ground acceleration was scaled to 0.07 g, 0.27 g, 0.5 g. 0.7 g, and 1 g in order to evaluate the building’s performance at different levels of seismic input. More than 100 instruments were used to monitor the behavior of the building during seismic tests measuring acceleration, displacement, and forces. The visual inspection shows that the building did not show any damage during all seismic tests. However the data analysis (dynamic identification, capacity spectrum, inter-story drift) confirm that during the 1.00 g test the structure went beyond its linear elastic limit. The results obtained from this experimental study suggest that the design hypotheses commonly adopted in practice for seismic analysis (e.g., in terms of force distributions between the walls, and also the behavior factor q) are not always consistent with the real behavior of timber frame multi-story buildings, and should be backed by more accurate knowledge of the contributions of the individual structural components.     

Methods and Approaches for Blind Test Predictions of Out-of-Plane Behavior of Masonry Walls: A Numerical Comparative Study

ABSTRACT

Earthquakes cause severe damage to masonry structures due to inertial forces acting in the normal direction to the plane of the walls. The out-of-plane behavior of masonry walls is complex and depends on several parameters, such as material and geometric properties of walls, connections between structural elements, the characteristics of the input motions, among others. Different analytical methods and advanced numerical modeling are usually used for evaluating the out-of-plane behavior of masonry structures. Furthermore, different types of structural analysis can be adopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.

Aiming to evaluate the capabilities of different approaches to similar problems, blind predictions were made using different approaches. For this purpose, two idealized structures were tested on a shaking table and several experts on masonry structures were invited to present blind predictions on the response of the structures, aiming at evaluating the available tools for the out-of-plane assessment of masonry structures. This article presents the results of the blind test predictions and the comparison with the experimental results, namely in terms of formed collapsed mechanisms and control outputs (PGA or maximum displacements), taking into account the selected tools to perform the analysis.