Modeling of Restoring Force Characteristics from Collapse Test Data of Frame Structures

1999年9月21日凌晨在台灣地區發生的集集地震，造成了許多在1982年以前建造的老舊的結構物遭受了嚴重的損害並且有不少已經倒塌。針對這些低韌性的RC結構物而言，通常對抵抗強烈地震力的能力都偏低，特別是在結構物的容許韌性(ductility)和容許的能量消散(energy dissipation)方面。對一個結構工程師而言，要如何補修老舊結構物讓這些結構物能夠符合新規範更嚴苛的要求並且提升結構物的強度來抵抗未來可能發生的大地震可說是主要考量，同時這些考量也能提供雇主在評估結構物利益得失一個良好依據。 在本論文中，所提出的遲滯行為分析模型考慮了RC結構物峰後行為(Post-Peak Behavior)並且針對結構物倒塌後負向勁度的預測做了研究。藉著模擬國家地震中心所舉行的低韌性RC結構崩塌實驗結果，一方面可以加以證實提出的遲滯分析模型是否能有效模擬峰後行為，另一方面也能定義此實驗結構所對應分析模式中參數值。除了針對實驗數值所做的模擬外，論文中也對C. Lynn 在1996年所做的大型崩塌實驗中挑選兩組實驗來進行模擬來增加所提出分析模式的可靠性。 另一個重點則是除了考慮傳統規範中除了考慮結構物的最大反應(ductility)更能針對系統的殘留位移(residual displacement)來建立一個更能表示結構物性能的基礎形式(performance matrix)。之後舉出長週期和短週期結構的例子，考慮對應50年內發生機率為2%、5%、10%的危害程度下，分別針對雙線性遲滯模式、遲滯行為的收縮效果、系統強度衰減和勁度折減的現象來做分析和討論。During the September 21 (local time) 1999 Chi-Chi Taiwan earthquake, a large number of older buildings built before 1982 sustained severe damage and many others suffered from complete failure. These old buildings, having low ductility RC columns, are known to have poor seismic performance in terms of ductility and energy dissipation capacity during severe seismic events. Therefore, it is the main concerns of structural engineers and, at the same time, benefit of building owners how to retrofit these old buildings to match more strict requirements of the next generation building code to get better odds to survive probable future earthquake events. In this study, an analytical inelastic hysteretic model which includes strength and stiffness deterioration and post-peak behavior with negative stiffness (i.e. collapse behavior) is developed. By observing the result of the collapse test data of RC portal frame structure at NCREE, verification on the proposed hysteretic model with the consideration of post-peak behavior is conducted and modal parameters are identified. Verification is also extended to two simulation cases by C. Lynn (1996). Based on the proposed model, a combination of maximum ductility and residual displacement in the format of a performance matrix is generated to define the system's performance of hazard levels from 475years to 2475years. Hysteretic characteristics including pinching effect, strength deterioration, stiffness degrading, and as well as different period of system are considered.CONTENTS ABSTRACT (Chinese) I ABSTRACT (English) III CONTENTS V LIST OF TABLES VII LIST OF FIGURES VIII CHAPTER 1 INTRODUCTION 1 1.1 Background and Motivation 1 1.2 Literature Review 4 1.3 Objective 6 CHAPTER2 ANALYTICAL DESCRIPTION OF PINCHING 8 AND DEGRADING HYSTERETIC SYSTEMS 2-1 Bilinear Systems 8 2-2 Multi-linear Systems 14 2-3 Sensitivity Study on Modal Parameters 18 CHAPTER 3 FORMULATION OF HYSTERETIC MODEL WITH 20 CONSIDERATION OF POST-PEAK BEHAVIOR 3.1 Description of Hysteretic Model 20 3.2 Estimation of Shear strength 22 3.3 Formulation of Hysteretic Model with 23 Consideration of Post-Peak Behavior 3.4 The Post-Capping Stiffness on Collapse Capacity 26 3.5 Summarized the Proposed Hysteretic Model with Post-Peak Behavior 32 CHAPTER 4 The Collapse Test of Low-Confinement RC Columns 33 And Numerical Simulation 4-1 Collapse tests of Low-Confinement RC column 34 4-2 Observation from Collapse Tests of Low-Confinement RC Column 41 4-3 Simulation of Collapse Test 43 4-4 Verification the Hysteretic Model Using Lynn’s Test Specimen 47 4-5 Variability of the Proposed Model 50 CHAPTERS 5 MAXIMUM / RESIDUAL DRIFT 52 PERFORMANCE MATRIX 5-1 Inelastic Response and Strength Factor 53 5-2 Residual Displacement of Nonlinear System 54 5-3 Selection of Ground Motion for Generating 56 RD-based Performance Matrix 5-4 Generation of RD-based Performance Matrix 59 CHAPTER 6 CONCLUSION AND FUTURE WORK 65 6-1 Conclusion 65 6-2 Future Work 68 REFERENCE 69 APPEND A 13