臺灣博碩士論文加值系統

在近年間有許多國家核可位在地震區域的混凝土結構物採用高強度鋼筋。以較少量的高強度鋼筋取代原先的普通強度鋼筋能在設計強度不變的情況下，有效減少鋼筋壅塞及增進現地的施工性。然而，若維持斷面尺寸不變並改用較少量的高強度鋼筋，雖然擁有與原本相同的初始勁度，但開裂後勁度則會下降。本文即在探討若兩個構架擁有同樣的初始勁度但不同的開裂後勁度是否在地震下會有相似的位移反應。另外，由於結構物的最大變位對於災害評估相當重要，此研究也針對現有的預測位移方法是否適用於高強度鋼筋混凝土結構物進行討論。

本研究對兩座二層樓一跨的試體進行振動台測試。此兩座試體除了縱向鋼筋以外有完全一樣的設計參數。試體C1 採用SD420 普通強度鋼筋，其柱及樑的縱向鋼筋比分別為2.1%以及1.6%。而試體H1 則採用SD685 高強度鋼筋，其柱及樑的縱向鋼筋比分別為1.2%以及1.3%。兩座試體的預測基底剪力係數約為0.9。此研究中，兩座試體在台南國家地震中心分別進行了三組的振動台測試。所有的激振輸入皆採用修改後的El Centro (1940) 南北向地表加速度歷時。El Centro (1940) 地震歷時在本研究中其時間間格以2/3 的倍率壓縮，且其振幅也被等比例調整。在最大強度激振時(稱作100%)，該加速度資料的最大加速度(PGA)為1 g，最大速度(PGV)為73 cm/s。在第一組試驗中，試體依序經歷了10%、25%、50%、75%、100% 的激振。在第二組試驗中，試體依序經歷了100%-2、10%-2、25%-2、50%-2 的激振。第二組實驗後，試體將會以環氧樹脂進行補強。而後則是第三組試驗，試體依序經歷了10%-3、25%-3、50%-3、100%-3 的激振。

實驗結果顯示第一組和第二組實驗中 H1 的最大位移比C1 的最大位移平均多了10%。而對於第一組和第二組實驗中大於50%的激振，H1 的最大位移比C1 的最大位移平均高出了15%。然而，考慮到H1 比C1 省下了將近40%的縱向鋼筋量，此位移需求的增量似乎是划算的。

在第六章中，探討了三種不同的位移評估方式，並且將其評估結果與實驗量測值比較。1) 單自由度模型搭配假設的週期與阻尼比。2) 由Sozen (2003) 學者提出的位移預測方法。3) 利用 Elwood (2009) 學者提出的有效勁度搭配彎矩塑性鉸在SAP2000 中進行的非線性分析。Sozen (2003) 的位移預測方法提供了合理的預測值。而SAP2000 的非線性分析與實驗量測值在100%、100%-2、100%-3 的平均誤差約為10%。由Elwood (2009) 學者提出的有效勁度能用以反應C1 和H1 不同的開裂後勁度且採用其勁度的SAP2000 分析結果大致上與實驗結果吻合。

In recent years, building codes in a number of countries have permitted the use of high-strength steel in reinforced concrete structures in seismic areas. Substituting conventional strength steel with a smaller amount of high-strength steel can reduce reinforcement congestion and improve the workability onsite while keeping the nominal sectional strength unchanged. Nevertheless, provided cross-sectional dimensions remain the same, substituting the conventional steel in the longitudinal direction with a smaller amount of HSSR (high strength steel reinforcement) would lead to similar initial stiffness but lower post-cracking stiffness. The focus of this thesis is to investigate whether two frames with similar initial stiffness but different post-cracking stiffness have comparable drift demand. In addition, since peak drift ratio is crucial in damage evaluation, this study also investigates whether methods used in the past to evaluate drift response provide reasonable estimates for structures with HSSR.

Two 2-story, 1-bay moment frame specimens were tested. The two specimens were designed to be identical except for the grade and quantity of longitudinal reinforcement. Specimen C1 was reinforced with SD420 bars and specimen H1 was reinforced with SD685 bars. The gross longitudinal reinforcement ratio in columns was 2.1% and 1.2% in C1 and H1 respectively. Both specimens had similar calculated base shear coefficients of approximately 0.9. They were subjected to three series of ground motions on the earthquake simulator at the National Center for Research on Earthquake Engineering in Tainan, Taiwan. All ground motions were scaled versions of the NS component of the ground acceleration recorded in 1940 at El Centro, California. The record from El Centro (1940) was scaled in time by a factor of 2/3 and scaled in amplitude such that the strongest ground motion (referred to as 100%) had a peak ground acceleration (PGA) of 1 g, and a peak ground velocity (PGV) of 73 cm/s. In Series-1, specimens were subjected to motions in the following sequence: 10%, 25%, 50%, 75, and 100% (of the strongest ground motion considered in this study). In Series-2, specimens were subjected to motions in the following sequence: 100%-2, 10%-2, 25%-2, 50%-2. After 50%-2 in Series-2, the specimens were repaired by epoxy injection and then subjected to Series-3 which included the ground motions 10%-3, 25%-3, 50%-3, and 100%-3.

The tests results showed that on average H1 drifted 10% more than C1 in Series-1 and Series-2. For motions equal or larger than 50% in Series-1 and Series-2, H1 drifted 15% more than C1 on average. Nevertheless, considering savings of almost 40% of amount of longitudinal reinforcements by replacing SD420 with SD685, the increase of drift demand seems acceptable.

In addition, three methods were considered to compare estimates of drift with experimental measurements: 1) SDOF model with assumed period and damping, 2) a method proposed by Sozen (2003) and 3) nonlinear analysis in SAP 2000. The method proposed by Sozen (2003) provided reasonable estimates, considering the simplicity of the method. The average difference in peak drift ratio between experiments and SAP2000 analysis for 100%, 100%-2, and 100%-3 were about 10%.

口試委員審定書 ..................................................................................................................... i
Acknowledgements: ...............................................................................................................ii
摘要.......................................................................................................................................iii
ABSTRACT ...........................................................................................................................v
INTRODUCTION............................................................................................1
LITERATURE REVIEW.................................................................................3
2.1 Static Tests ...............................................................................................................3
2.2 Dynamic Tests .........................................................................................................4
2.2.1 Otani and Sozen (1972) ....................................................................................4
2.2.2 Laughery (2016) ...............................................................................................4
2.2.3 Yan (2020)........................................................................................................6
2.3 Numerical Investigations .........................................................................................6
2.3.1 Estimating Peak Drift, Sozen (2003)................................................................7
2.3.2 Effective Stiffness.............................................................................................7
EXPERIMENTAL DESIGN AND SETUP...................................................10
3.1 Overview of Experimental Program......................................................................10
3.2 Specimens ..............................................................................................................11
3.3 Test Setup ..............................................................................................................13
3.3.1 Mass................................................................................................................13
3.3.2 Out-of-plane Bracing......................................................................................13
3.3.3 Instrumentation...............................................................................................14
3.4 Ground Motion ......................................................................................................15
3.5 Test Procedure .......................................................................................................17
3.6 Numerical Model ...................................................................................................18
3.6.1 Moment-Curvature Relationships...................................................................18
3.6.2 Model Assumptions........................................................................................20
3.6.3 Expected Behavior of Frames.........................................................................21
TEST RESULTS ............................................................................................23
4.1 Data Processing......................................................................................................23
4.1.1 FDAC Data Acquisition System ....................................................................24
4.1.2 MOCAP system..............................................................................................24
4.2 Ground Motion ......................................................................................................25
4.3 Free Vibration and White Noise Test ....................................................................26
4.3.1 Free Vibration Test .........................................................................................26
4.3.2 White Noise Test ............................................................................................26
4.4 Specimen Response Histories ................................................................................27
4.4.1 Drift Comparison............................................................................................27
4.4.2 Story Responses..............................................................................................28
4.4.3 Curvature Distribution....................................................................................28
4.4.4 Force-displacement Relationship ...................................................................29
4.5 Damage ..................................................................................................................30
DISCUSSION OF OBSERVED RESPONSE ...............................................33
5.1 Maximum Base Shear ............................................................................................33
5.2 Stiffness .................................................................................................................34
5.2.1 Primary Curve ................................................................................................34
5.2.2 Effective Stiffness...........................................................................................35
5.3 Period and Damping Ratio.....................................................................................35
5.4 Drift Response .......................................................................................................37
5.4.1 C1 vs. H1 ........................................................................................................37
5.4.2 Series-1 vs. Series-2 .......................................................................................38
5.4.3 Excursions ......................................................................................................39
5.5 Summary of observed reponses .............................................................................40
NUMERICAL ANALYSIS RESULTS .........................................................42
6.1 SDOF model ..........................................................................................................42
6.1.1 SDOF model with apparent first mode...........................................................42
6.1.2 SDOF model with assumed first mode...........................................................45
6.2 Peak drift ratio, Sozen (2003) ................................................................................46
6.3 Nonlinear analysis, SAP2000 ................................................................................47
6.3.1 Using effective stiffness suggested by Elwood ..............................................47
6.3.2 Using effective stiffness suggested by ACI 318-19 .......................................49
6.3.3 Using effective stiffness determined from MC relationship ..........................49
6.4 Summary of the evaluations ..................................................................................49
SUMMARY AND CONCLUSIONS.............................................................52
7.1 Summary................................................................................................................52
7.2 Conclusions............................................................................................................54
7.3 Supplement and prospect .......................................................................................55
FIGURES .............................................................................................................................56
TABLES.............................................................................................................................211
REFERENCES...................................................................................................................239
APPENDIX ........................................................................................................................242
A1: Material ....................................................................................................................242
A1.1 Concrete .............................................................................................................242
A1.2 Reinforcement ....................................................................................................244
A2: Data conversion .......................................................................................................244
A2.1 First-story story drift from String Pots data .................................................244
A2.2 Story drifts from MOCAP data ....................................................................245
A3: Epoxy repair.............................................................................................................247
A4: Detailed beam crack maps .......................................................................................247
A5: Test Notes ................................................................................................................248

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