Evaluation of seismic performance of cultural historic masonry structures considering soil-structure interaction

다국어 초록 (Multilingual Abstract)

Masonry structures have been widely used for religious, defensive, and residential purposes and form an important part of cultural heritage in many regions. Although they offer high compressive strength, durability, and favorable thermal and acoustic properties, they generally have low tensile strength, limited shear resistance, and brittle failure behavior, making them highly vulnerable to earthquakes. Recent events, such as the 2015 Nepal earthquake and the 2023 Türkiye earthquake, have shown the severe seismic vulnerability of historic masonry monuments. In many Asian countries, including Korea, China, Japan, and Nepal, ancient stone masonry structures have high cultural value, but their seismic behavior and probabilistic vulnerability remain insufficiently understood. This dissertation develops a numerical and probabilistic framework for evaluating the seismic performance of cultural historic masonry structures. The framework combines nonlinear numerical modeling, time-history analysis, incremental dynamic analysis, fragility assessment, and seismic reliability evaluation. Two Korean heritage structures are studied: a five-story stone pagoda and an ancient stone astronomical observatory. The pagoda is analyzed using a fixed-base condition without soil–structure interaction （SSI）, while soil–structure interaction is explicitly considered for the observatory to account for foundation flexibility, site response, and soil amplification. The distinct element method （DEM） is mainly used to simulate the dynamic response of the stone masonry structures because it can capture contact interaction, sliding, rocking, separation, impact, and collapse of individual stone components. For the observatory, the surrounding soil domain is modeled using site-specific properties to represent seismic wave propagation and soil amplification effects. Fragility curves are developed through incremental dynamic analysis （IDA） using ground motion records. Lateral displacement and contact gap are adopted as structural demand parameters, and the fragility functions are combined with seismic hazard curves to evaluate seismic reliability. For the five-story pagoda, a PGA of 0.469g corresponds to a 50% probability of collapse in the most conservative assessment, while the 50-year collapse probability at the most vulnerable site is 1.65%. The response is strongly affected by the predominant frequency of the input motion, with lower-frequency motions producing larger distortion. For the ancient astronomical observatory, PGA values of approximately 0.25g and 0.29g correspond to a 50% probability of very severe damage in the conservative and less conservative assessments, respectively. The upper portion above the two long beams experiences the largest distortion, and collapse mainly occurs through stone falling caused by sliding or rocking. At low PGA levels, the long beams help restrain downward propagation of distortion and improve the stability of the lower part. The effectiveness of polyurea coating as a seismic strengthening technique is also numerically investigated. The results show that, when appropriately applied, polyurea can improve energy dissipation, structural integrity, and damage delay, providing a potential low-intervention retrofit option for masonry structures. Overall, this dissertation contributes to the seismic assessment of cultural heritage masonry structures by integrating advanced numerical simulation, fragility analysis, and reliability assessment. The proposed framework provides a rational basis for predicting seismic vulnerability and supporting retrofit decisions for ancient stone structures under earthquake hazards.

목차 (Table of Contents)

• 1 INTRODUCTION 1
• 1.1 Problem description and motivation 1
• 1.2 Aim and objective 5
• 1.3 Organization of the dissertation 6
• 1.4 Contribution of research 7
• 1.5 Relevant publications 8
• 2 LITERATURE REVIEW 10
• 2.1 Seismic evaluation of historic masonry structures 10
• 2.2 DEM approach in masonry modelling 13
• 2.3 Soil–structure interaction consideration 17
• 2.4 Framework of fragility analysis 19
• 2.5 Concluding synthesis 22
• 3 MECHANICAL CHARACTERIZATION FROM STATIC TESTS FOR MASONRY STRUCTURE – VALIDATION WITH DIFFERENT APPROACHES 24
• 3.1 Introduction 24
• 3.2 Experimental–Numerical Correlation and Modeling Approaches for Masonry 26
• 3.2.1 Concrete model in 3DEC 29
• 3.2.2 Simulation of static tests with micro and simplified micro approaches 33
• 3.3 Concluding synthesis 39
• 4 SEISMIC FRAGILITY ANALYSIS AND RELIABILITY EVALUATION FOR ANCIENT STONE PAGODA 41
• 4.1 Introduction 41
• 4.2 DEM-based numerical simulation 44
• 4.3 Fragility analysis framework 51
• 4.4 IDA analysis 55
• 4.4.1 Selected ground motion records 55
• 4.4.2 Structural responses 58
• 4.5 IDA curves and fragility curves 64
• 4.6 Seismic reliability evaluation 73
• 4.7 Summary and conclusion 80
• 5 SEISMIC FRAGILITY ANALYSIS FOR ANCIENT ASTRONOMICAL OBSERVATORY 82
• 5.1 Introduction 82
• 5.2 DEM approach in 3DEC-FLAC3D coupling simulation 84
• 5.2.1 Structure modeling 84
• 5.2.2 Soil modeling 89
• 5.2.3 Damping for masonry structure and soil mass 97
• 5.3 IDA analysis 102
• 5.3.1 Strong ground motion selection 102
• 5.3.2 Soil responses 103
• 5.3.3 Structural responses 112
• 5.4 IDA curves and fragility curves 124
• 5.5 Conclusion 131
• 6 NUMERICAL INVESTIGATION OF SEISMIC RESPONSE OF MASONRY STRUCTURE STRENGTHENED WITH POLYUREA COATING 133
• 6.1 Introduction 133
• 6.2 DEM-based approach 137
• 6.2.1 General about DEM approach 137
• 6.2.2 Polyurea layer simulation 143
• 6.2.3 Soil structure interaction and damping 145
• 6.3 Framework for dynamic numerical simulation 148
• 6.4 Dynamic characteristics of the masonry structure 150
• 6.5 Numerical analysis results 152
• 6.5.1 Fixed-base condition 152
• 6.5.2 SSI condition 165
• 6.6 Summary and conclusion 171
• 7 EFFECTIVENESS OF POLYUREA COATING IN STRENGTHENING TO THE ANCIENT ASTRONOMICAL OBSERVATORY 174
• 7.1 Introduction 174
• 7.2 Effectiveness of polyurea strengthening on the seismic performance of the structure under the Kobe earthquake 179
• 7.3 Summary and conclusion 185
• 8 CONCLUSIONS AND RECOMMENDATIONS 187
• 8.1 Introduction 187
• 8.2 Summaries and Conclusions 188
• 8.3 Limitations and Future Works 191
• REFERENCES 195