Rocking and kinematic approaches for rigid block analysis of masonry walls: state of the art and recent developments

The assessment of the rocking and overturning response of rigid blocks to earthquakes is a complex task, due to its high sensitivity to the input motion, variations in geometry and dissipation issues. This paper presents a literature review dealing with classical and advanced approaches on rocking motion with particular reference to masonry walls characterized by a monolithic behavior. Firstly, the pioneering work of Housner based on the concept of the inverted pendulum is discussed in terms of the most significant parameters, i.e., the size and slenderness of the blocks, the coefficient of restitution and ground motion properties. Free and restrained rocking blocks are considered. Then, static force-based approaches and performance-based techniques, mostly based on limit analysis theory, are presented to highlight the importance of investigating the evolution of the rocking mechanisms by means of pushover curves characterized by negative stiffness. From a dynamic perspective, a review of probabilistic approaches is also presented, evaluating the cumulative probability of exceedance of any response level by considering different earthquake time histories. Some recent simplified approaches based on the critical rocking response and the worst-case scenario are illustrated, as well.The authors acknowledge the sponsorship of the Italian Civil Protection, through the RELUIS Project-Line: Masonry Structures (2017).info:eu-repo/semantics/publishedVersio

Traditional and Innovative Approaches in Seismic Design

This special issue collects selected papers about a wide range of innovative applications in earthquake engineering. These studies were presented during the 2nd Edition of the International Workshop “Traditional and Innovative Approaches in Seismic Engineering”, held in Pisa in March 2017. The topics refer to the investigation of traditional and innovative materials for earthquake engineering applications: masonry, reinforced concrete, steel, structural glass and timber. In particular, advanced analytical and numerical analyses are described for considering effects of strength and material irregularities and rocking behavior under seismic excitations on historic buildings and industrial facilities. Experimental tests are also illustrated with the purpose of investigating the strengthening on masonry arches due to lime-based mortar composites and of obtaining reliable values of stiffness for moment resisting steel-timber connections. Among the innovative approaches, studies on original pavilions made of long-spanned TVT-portals braced with hybrid glass-steel panels are illustrate

Seismic assessment and rehabilitation of a historical theatre based on a macro-element strategy

The structural and seismic assessment of the 19th-century Petruzzelli theater in Bari (Italy) is presented. The macro-elements strategy was adopted to dismantle the whole structure in parts. The steel dome was verified through dynamic multi-modal analysis based on finite element model. Each masonry macro-element was firstly verified through a kinematic analysis aiming at excluding local collapse mechanisms. Afterwards, a nonlinear static analysis was carried out in order to evaluate its overall seismic capacity. The effectiveness of linear or nonlinear analyses and of the macro-element strategy compared with other modeling techniques is also discussed. After highlighting the structural deficiencies of the theater, upgrading solutions are proposed with consideration of the safety needs and the architectural preservation requirements based on the historical importance of the buildin

THE EARLY PHRYGIAN GATE AT GORDION, TURKEY: AN INVESTIGATION OF DRY STONE MASONRY IN SEISMIC REGIONS AND RECOMMENDATIONS FOR STABILIZATION

The archaeological site at Gordion, Turkey is located in a region of high seismic activity, which threatens the standing masonry structures—particularly the dry laid limestone walls—of the ancient Phrygian capital. First excavated in the 1950s, the citadel gate is composed of an ashlar limestone veneer encasing a rubble core. Although the gate has been the focus of several conservation efforts, the unreinforced masonry structure requires study and possible stabilization to mitigate and prevent further bulging or even collapse. The gate’s current conditions include extensive cracking, spalls, split faces, missing chinking stones, open joints and bulges, which partially result from the complex history of the site. Constructed around 900 BC, the Early Phrygian Gate only briefly served as the main entryway to the citadel; it was then affected by fire and burial and used as a foundational support for later structures. Partial excavation has largely exposed the North and South Courts of the gate complex. However, several courses of the later building stone remain in localized areas of the gate walls, and the interior of South Court still contains the almost 3,000 year old clay construction fill. These factors have contributed to displacement of the multiple leaf system by exerting lateral force and causing compression and shear cracks. This thesis synthesizes existing knowledge of the behavior of masonry during seismic events, properties of dry stone structures and site-specific characteristics as a basis for constructing recommendations for future monitoring and stabilization efforts

무보강 조적식 역사 구조물의 보존과 복구

학위논문(박사) -- 서울대학교대학원 : 공과대학 건축학과, 2021.8. 강현구.역사적 구조물은 인류의 문화적, 건축적, 역사적 가치를 지니며, 동시에 이러한 가치를 미래 세대에게 전달하는 데 있어 중요한 역할을 한다. 그러나, 많은 문화 유산들은 오랜 세월 지진이나 기타 자연재해로 심각한 피해를 입어왔다. 구조적인 측면에서 볼 때, 높은 질량, 낮은 인장강도, 낮은 전단강도 및 낮은 연성 등이 불리하게 작용하였으며, 조적조 구조물의 경우 재료의 특성, 형상, 구성, 요소 배치, 연결부, 기초의 강도 등 여러 변수가 해당 구조물의 내진거동에 영향을 끼쳤다. 이는 구조물의 부분 및 전체 붕괴로 이어질 수 있기에 역사적인 조적조 구조물의 보존과 보강은 계속적으로 연구가 필요한 주제이다. 본 논문에서는, 가장 중요한 구조적 요소인 비보강 조적조 벽체의 건축적, 구조적 특성을 분석하였고, 지진하중에 의해 야기되는 전형적인 손상에 대해 서술하였다. 그 후, 분석적 연구에 적합한 방법을 선택하기 위해 몇 가지 보강 방법에 대한 장단점을 조사하였다. 본 연구에서는 여러 유형의 비보강 조적조 벽체 중 건식 석조 벽체에 특히 집중하여 분석이 진행되었다. 유한요소해석을 통해 단조 및 반복 가력에서의 벽체 거동이 평가되었고, 수치해석 결과를 검증하기 위해 기존 연구자들의 실험결과가 사용되었다. 또한, 요소와 벽체의 배열 및 규모에 따라 매개변수적 연구가 수행되었다. 최종적으로 모델의 수치해석 결과와 파괴 양상을 고려하여 해당 구조물에 적합한 보강 방법이 선정되었다. 이 때, 기존의 역사적 구조물의 보강에 있어 가장 효율적이고 실용적인 방법 중 하나로 평가 받고 있는 철근 삽입 공법이 심층 분석되었다. 가장 효율적인 재료와 철근 배치를 탐구하기 위해 매개변수적 연구가 추가적으로 수행되었다. 본 논문의 연구를 통하여 궁극적으로 비보강 조적조 벽체의 내진거동과 적절한 보강 방법, 그리고 이를 어떻게 향상시킬 수 있는 지에 대한 해법을 도출할 수 있었다.Historical structures constitute the most significant part of the cultural, architectural, and historical values of past peoples, which play an important role in transmitting these values to future generations. Many of these cultural heritage buildings have been severely damaged by past earthquakes or other natural disasters. In terms of structural property, the main defects are related to high specific mass, low tensile strength, low to moderate shear strength, and low ductility. The seismic behavior of masonry buildings highly depends on the material properties, geometry, configuration, arrangements of units, connections, foundation strength, etc. These features may cause them to be vulnerable to a sudden movement which can be terminated by the partial or entire collapse of the structure. Therefore, preservation and protection of this type of structure is an interesting topic and of great concern for the engineering community. This dissertation deals with a detailed architectural and structural characterization of different types of unreinforced masonry (URM) walls as the most important structural element and explains their typical damage caused by seismic loads. Then, several retrofitting methods including their advantages and shortcomings were investigated to choose an appropriate method for analytical studies. Among all types of URM walls, the dry-stack stone masonry wall was selected and its behavior under monotonic and cyclic loads was evaluated using finite element method (FEM). To validate the results of numerical analysis, all FEM models were calibrated with a set of experimental investigations that have been conducted by other researchers. Then, some parametric studies were conducted for different arrangements and scales of units and walls. Regarding the results of numerical analysis and failure modes observed in the models, an appropriate retrofitting method was determined. Given the existing limitations on retrofitting historical structures, inserting rebars into the wall was considered as one of the most efficient and practical retrofit techniques. Finally, a parametric study has been done for materials and arrangements of inserted rebars with a hope to achieve the most efficient case. The results obtained by this study led to a deeper understanding of the seismic behavior of URM walls and how it can be enhanced by a proper retrofit technique.Chapter 1. Introduction 1 1.1 History and Motivation 2 1.2 Scope and Methodology 10 1.3 Organization 13 Chapter 2. Technical Investigation of HURM Structures 15 2.1 General Description 16 2.2 Architectural Characterization 17 2.2.1 Material classification 18 2.2.2 Geometry 24 2.3 Structural Characterization 26 2.3.1 Structural components 27 2.3.2 Masonry components 34 2.4 Wall Behavior 37 2.4.1 Wall behavior under compressive load 39 2.4.2 Wall behavior under tensile load 41 2.4.3 Wall behavior under shear load 43 2.5 Summary 44 Chapter 3. Typical Seismic Damage in HURM Buildings 45 3.1 Typical Damage of HURM Structures 46 3.2 Damage in Non-Structural Elements 48 3.3 Damage in Structural Elements 49 3.3.1 Connection failure 50 3.3.2 Wall failure 53 3.3.3 Diaphragm failure 61 3.3.4 Foundation failure 61 3.4 Impact of Erosion on the Performance of HURM Buildings 63 3.4.1 Wind 65 3.4.2 Temperature 66 3.4.3 Rain and humidity 66 3.4.4 Biological damage 67 3.4.5 Human intervention 68 3.5 Summary 68 Chapter 4. Technical Issues and Methods of Preservation for HURM Structures 69 4.1 Preservation Techniques for HURM 70 4.2 Improving Structural Integrity 73 4.2.1 Confinements 73 4.2.2 Transversal anchorage 78 4.2.3 Strengthening of junction 78 4.2.4 Textile reinforced mortar and steel reinforced grout 79 4.2.5 Mortar joint treatment 81 4.2.6 Strengthening of roof diaphragm 86 4.3 Reducing Seismic Demands 87 4.3.1 Base isolation 87 4.3.2 Seismic damper 89 4.4 Upgrading Structural Components 89 4.4.1 Reinforced concrete wall 90 4.4.2 Moment and braced frames 91 4.4.3 Surface treatment 92 4.4.4 External reinforcements 96 4.4.5 Post-tensioning 106 4.4.6 Mesh reinforcement 109 4.4.7 Reticulatus system 113 4.5 Technical Comparison 116 4.6 Summary 120 Chapter 5. Experimental and Numerical Methods for HURM Structures 121 5.1 General Description 122 5.2 Experimental Method 123 5.2.1 Material test 124 5.2.2 Structural test 133 5.3 Numerical Analysis Methods 137 5.3.1 Concept of macro and micro approaches 140 5.3.2 Kinematic method 146 5.3.3 Finite element method 149 5.3.4 Discrete element method 153 5.4 Analysis Types 155 5.4.1 Linear static analysis (LSA) 159 5.4.2 Linear dynamic analysis (LDA) 161 5.4.3 Nonlinear static analysis (NSA) 164 5.4.4 Nonlinear dynamic analysis (NDA) 167 5.5 Material and Joint Behavior 168 5.6 Summary 174 Chapter 6. Numerical Modeling of Stone Wall 175 6.1 General Descriptions 176 6.2 Experimental Research Program 178 6.3 ABAQUS Software 187 6.4 Numerical Model 191 6.5 Calibration and Validation of Numerical Models 198 6.6 Sensitivity Analysis 207 6.6.1 Penalty stiffness sensitivity analysis 207 6.6.2 Mesh size sensitivity analysis 210 6.6.3 Friction coefficient sensitivity analysis 214 6.6.4 Comparison of 2D and 3D analyses 218 6.6.5 Comparison of pushover and cyclic analysis 224 6.7 Parametric Study 232 6.8 Summary 245 Chapter 7. FEM Analysis of Stone Masonry Walls Retrofitted by Rebars 247 7.1 Proposed Retrofit Technique 248 7.2 Material Properties 251 7.3 Numerical Modeling Assumptions 254 7.4 Retrofitting Program 256 7.4.1 Horizontal rebar models 256 7.4.2 Vertical rebar models 262 7.4.3 Diagonal rebar models 282 7.5 Comparative Studies 302 7.6 Cyclic Analysis 306 7.7 Summary 318 Chapter 8. Summary and Conclusion 319 8.1 Summary 320 8.2 Conclusion 322 8.3 Future Work 328 References 329 Acknowledgment 359 Abstract in Korean 360박

Model Validation and Simulation

The Bauhaus Summer School series provides an international forum for an exchange of methods and skills related to the interaction between different disciplines of modern engineering science. The 2012 civil engineering course was held in August over two weeks at Bauhaus-Universität Weimar. The overall aim was the exchange of research and modern scientific approaches in the field of model validation and simulation between well-known experts acting as lecturers and active students. Besides these educational intentions the social and cultural component of the meeting has been in the focus. 48 graduate and doctoral students from 20 different countries and 22 lecturers from 12 countries attended this summer school. Among other aspects, this activity can be considered successful as it raised the sensitivity towards both the significance of research in civil engineering and the role of intercultural exchange. This volume summarizes and publishes some of the results: abstracts of key note papers presented by the experts and selected student research works. The overview reflects the quality of this summer school. Furthermore the individual contributions confirm that for active students this event has been a research forum and a special opportunity to learn from the experiences of the researchers in terms of methodology and strategies for research implementation in their current work

ROBUST MODEL DEVELOPMENT FOR EVALUATION OF EXISTING STRUCTURES

In the context of scientific computing, validation aims to determine the worthiness of a model in supporting critical decision making. This determination must occur given the imperfections in the mathematical representation resulting from the unavoidable idealizations of physics phenomena. Uncertainty in parameter values furthers the validation problems due to the inevitable lack of information about material properties, boundary conditions, loads, etc. which must be taken into account in making predictions about structural response. The determination of worthiness then becomes assessing whether an unavoidably imperfect mathematical model, subjected to poorly known input parameters, can predict sufficiently well in its intended purpose. The maximum degree of uncertainty in the model\u27s input parameters which the model can tolerate and still produce predictions within a predefined error tolerance is termed as robustness of the model. A trade-off exists between a model’s robustness to unavoidable uncertainty and its agreement with experiments, i.e. fidelity. This dissertation introduces the concept of satisfying boundary to evaluate such a trade-off. This boundary encompasses the model predictions that meet prescribed error tolerances. Decisions regarding allocation of resources for additional experiments to reduce uncertainty, relaxation of error tolerances, or the required confidence in the model predictions can be arrived at with the knowledge of this trade-off. This new approach for quantifying robustness based on satisfying boundaries is demonstrated on an application to a nonlinear finite element model of a historic masonry monument Fort Sumter

Multiscale approach toward the assessment and conservation of archaeological heritage at Pompeii

The protection and promotion of heritage structures must be addressed by following fundamental principles of compatibility, reversibility, distinguishability, and minimum intervention for the protection of both the material asset and intangible values. To do that, conservation, reinforcement, and restoration interventions of architectural heritage require multi-disciplinary approaches. Indeed, the achievement of comprehensive and detailed knowledge of the structural behavior and material characteristics of heritage structures is an essential part of the conservation and restoration process. The archaeological site of Pompeii was listed as a World Heritage Site for the outstanding value of its tangible and intangible heritage. The protection of this exceptional site set special challenges related to its great extension, the fragility of its built asset, and a large number of visitors hosted every day. Moreover, from a structural point of view, technical and conservation restrictions limit the possibility to perform extensive and in-depth investigation campaigns to characterize basic mechanical properties. This study was based on scientific cooperation between the Department of Structures for Engineering and Architecture (DiSt), of the University of Naples Federico II, and the authority of the Archaeological Park of Pompeii (PAP). The research programme developed in this thesis aimed at providing fundamental mechanical information, which was still lacking in the literature, and suitable diagnostic methodologies, mainly based on non-destructive techniques and correlations with destructive test outcomes, to support structural assessment and conservation. For this purpose, the study was developed through multiscale diagnostic approaches and involved different types of activities and methodologies: extensive surveys; archival research; in situ inspections; in situ and laboratory testing involving both non-destructive and destructive methods; and numerical simulations. The research mainly focused on two typical constructive elements of ancient Pompeian architecture, among those most representative and vulnerable of the site: rubble stone masonry structures, traditionally known as opus incertum; and free-standing multridrum tuff columns. The study of rubble stone masonry was developed through three main stages from the scale of the building materials to the scale of the masonry assemblages: i) the mechanical characterization of typical building materials (i.e. archeological stone units and mortars), which involved destructive tests (i.e. compression tests) and non-destructive tests (i.e. sclerometric tests and ultrasonic pulse velocity tests) performed on the stone units; ii) the characterization of archaeological masonry structures through in situ non-destructive tests, namely sonic pulse velocity tests; iii) the construction and characterization through non-destructive (i.e. sonic pulse velocity tests) and destructive tests (i.e. in situ diagonal compression tests and laboratory axial compression tests) of masonry panels reproducing the archaeological opus incertum. These were constructed by carefully following the ancient technique found at Pompeii and using original stone units and compatible mortar. Considering the impossibility of performing minor destructive tests or destructive tests on the archaeological materials, the extended and articulated investigation programme provided unique information on a very common masonry typology in heritage contexts. As regards the study of the multidrum columns, it involved two main stages: i) extensive surveys and analyses of their geometrical features and the most widespread forms of degradation, affecting their stability and seismic response, which included an analysis of past structural interventions and their effects on the current state of preservation of the columns; ii) the numerical modeling of these elements and simulation of their seismic response, under different real seismic inputs. Systematic and detailed knowledge of the geometrical properties and state of preservation of a considerable number of free-standing multidrum columns allowed identifying columns being potentially more vulnerable than others; moreover, approximate formulations for a primary estimation of the stability of multidrum columns towards the seismic risk were derived from the numerical simulations. In addition to that, a comprehensive and accurate research programme was developed for the design and characterization of a suitable repair mortar for structural interventions on archaeological structures. This part of the research was developed within a research visit at the University of Minho (Guimaraes, Portugal), Institute for Sustainability and Innovation in Structural Engineering (ISISE), and the research stay was coordinated and supervised by Prof. Eng. Miguel Azenha and Prof. Eng. Paulo B. Lourenco for ISISE. The mixture was prepared following traditional mix design and using raw materials as similar as possible to the ancient ones. In particular, precious and rarely available natural pozzolan from the Phlegrean area (i.e. the same volcanic region where the ancient Roman builders collected their pozzolan) was used. The experimental programme and the adopted methodologies were accurately controlled to monitor fundamental mechanical and physical properties of the mortar from the first days after the preparation up to 200 days, to provide useful information which is still lacking in the literature. This study aimed at supporting the conservation and valorization of heritage assets of immeasurable value, by contributing to achieving adequate knowledge from a structural point of view. The attainment of that objective was intended based on the development of investigation approaches that are: i) compatible with conservation requirements; ii) repeatable and comparable with experimental campaigns carried out in other contexts; iii) representative of the vast built heritage of the site. The achieved information could represent a useful tool for the definition of appropriate choices and new methodologies for the design and planning of suitable interventions on the heritage structures

Seismic vulnerability of historical structures with the discrete element method

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.Includes bibliographical references (p. 333-345).It is widely recognized that historical structures represent a cultural heritage which should be preserved and transmitted to future generations. In several countries, and particularly, in the Mediterranean area, where a large number of important monuments are exposed to seismic hazard, there is a growing interest for the problem of strengthening such structures in order to reduce their seismic vulnerability, while preserving their original architectural integrity. However the seismic vulnerability assessment of historical block structures is still a challenging task. In this work, after having explored the potentials and limitations of the Discrete Element Method for this type of problem, a new joint model for the quasistatic analysis of block structures is proposed. It accounts for (a) the non coplanarity of the contact surfaces, and (b) friction softening. The new model allowed a more accurate prediction of the inplane failure load and corresponding failure mechanism of opus quadratum walls (walls made of regular squared blocks without mortar). In particular it predicts the development of progressive internal displacements, and the formation of localized sliding band as observed in the experimental models. Such results confirm that even apparently negligible joint imperfections should not be ignored since they may cause significant modifications in the response of a block structure subjected to gravity and lateral loading.by Tommaso Pagnoni.Ph.D