【S025】 Advances and Challenges in Structural Dynamics and Earthquake Engineering (結構動力與地震工程的進展與挑戰)

Thursday, 18 November, 14:30 ~ 16:00, Conference Room ROOM 6
Organizer: Wei-Tze Chang, Marco Bonopera
Chair: Wei-Tze Chang, Marco Bonopera


14:30 ~ 14:45 (15')
0255  台北盆地鋼構抗彎矩構架之震損與風險評估
Feng-Hsuan Chang and Tung-Yu Wu
由於鋼構建築物重量輕、施工工期短、延性(ductility)能力強等優點,故其被廣泛地應用在人口密集且常發生地震的台灣。而在過去五十年間,台灣的鋼結構及耐震設計規範皆經歷了幾次重大的改革,以致共存於台灣各都市中之鋼構造建築物,皆依不同時期之性能目標所設計建造而成,然而其對於都市整體震災風險之影響,卻尚未有系統性之探討。因此本研究依規範之演進設計一系列不同樓高之鋼結構抗彎矩構架作為原型構架,並參考美國FEMA P-58所提出之評估流程,以修繕時間、修繕金額、人員傷亡等指標來量化結構之震災韌性,配合商用數值軟體ETABS對原型構架進行非線性動力歷時分析,探討各時期鋼構造建築物在不同等級地震下之災損變化。評估結果顯示,在不考慮倒塌且執行地震強度評估法之前提下,隨著建物樓層數之提高,平均每層所需花費之修繕金額越高,但在高樓層之後其提高趨勢則趨於平緩。而依據921地震前之規範所設計之建物其災損明顯為最高,921地震後建物之震災韌性雖有顯著提升,但依現行法規新建之建物則因具有較大之樓層加速度反應而使非結構構件有較高之損害。最後依災損評估結果,對不同時期之建築物提出補強順序上之建議。


14:45 ~ 15:00 (15')
0259  Research on Seismic Behavior of RC Structure with 3D Finite Element Nonlinear Analysis
Jian-Hong Lin, Hsuan-Teh Hu and Fu-Pei Hsiao
According to the fault data announced by the Central Geological Survey, MOEA, ROC in 2012, there are 20 first-class active faults and 13 second-class active faults in Taiwan. As it is known to all that near-fault earthquakes have the unique characteristics of high velocity, large displacement and long-period seismic waves. And given that the past earthquake event, it is known that most buildings are collapsed due to localized damage caused by torsional irregularity. The torsional irregularity is the main cause of the column damage. Apart from these, doublet earthquakes have become more frequent in recent years, which means the building structure is more likely to face the impact under the damaged situation.
This study carries out a series of half-scale seven-story vibration table experiments to focus on the assessment of damaged torsional irregularity weak-layer buildings withstand near-fault earthquakes paired with ABAQUS to simulate the material damage and the seismic behavior of RC structure.
This analysis adopts ABAQUS to simulate the static and dynamic mechanical behavior of the RC structure, employs the CDP material model to describe concrete material and utilizes the damage model proposed by Y. Tao and J.F. Chen in 2015. Moreover, this study utilizes the restart analysis to ensure the plastic behavior can be controlled through the definition of the damage model and enhance the accuracy of the simulation and have an excellent knowledge of the doublet earthquakes more efficiently.
The following conclusions can be drawn according to the difference in component dimension, damage situation and ductility. First of all, the restart analysis function in ABAQUS can effectively analyze the damaged concrete and exhibits the characteristics of the hysteresis loop of the damaged column and undamaged column. Secondly, the function of damage parameters proposed by Y. Tao and J.F. Chen can accurately simulate and predict the seismic response of the RC structure through inputting the ground motion successively. Lastly, assign different damage models for ductile column and nonductile column depending on the degree of difficulty of damage due to different protection from transversal rebar. In this way, it can grasp the seismic response of the structure with ductility irregularity.

15:00 ~ 15:15 (15')
0283  既有抗彎矩鋼構造建築耐震能力評估
Minlang Lin
本研究針對抗彎矩鋼構造建築,採用ASCE 41-13建議之構件非線性鉸性質,考量傳統接頭及改良式接頭,研擬建議之性能目標,本研究提出進行耐震評估時須檢核之項目與方法,以協助工程師確保耐震評估結果之合理性,避免對於評估結果錯誤判讀,影響評估結果之準確性。最後,本研究進行四棟樓層數由二至十五層之抗彎矩系統鋼構造建築案例之詳細評估,說明評估流程及探討評估結果,以供工程實務參考。

15:15 ~ 15:30 (15')
0297  Investigation on the interference induced bistable aerodynamic phenomenon of double square prisms under uniform flows
Guan-Ying Chen and Yuan-Lung Lo
In the authors’ previous research results, the downstream interference effect induced by the downwind building has been addressed through a systematic series of wind tunnel tests. Due to the complex nature of the three-dimensional interference effects of high-rise buildings, an investigation based on two-dimensional interference effects is more preferred. This research intends to investigate the aerodynamic forces of two closely neighboring square prism models under uniform smooth and turbulent flows with such a background. The experiment was conducted in the sectional model wind tunnel at Tamkang University, which allows simulating a less than 0.5% smooth flow and is capable of uniformly turbulent (8%) flows with the installation of grid frames. Two prism models were placed tandemly with an adjustable distance. Both ends of the models were manufactured with end plates to avoid reverse flows. Micro-pressure scanning systems recorded the instantaneous surface pressures along the central ring position of both prism models. Pressure/force coefficients were then calculated based on stable background static pressures. Results show that the existence of the downwind prim reduced the drag force of the upwind square prism. For the smooth flow cases, a bistable phenomenon was identified when the distance between two prisms is in the range of X/D = 3.25 ~ 3.60 (X the distance; D the width of the prism). When the bistable phenomenon occurs, the aerodynamic forces of both prisms reveal two obviously different fluctuations intermittently. Such intermittent fluctuations are normally averaged out if following the conventional force determination. In a non-stationary concept, this bistable phenomenon implies the potential to trigger a larger amplitude in building vibration. With the existence of the approaching turbulence, the bistable phenomenon was disturbed and hard to find. Combined with the results in Sakamoto e al. (1988, 1989), this research concludes a bistable belt area concerning the distance and the approaching turbulence.

15:30 ~ 15:45 (15')
0306  近斷層地震對建築結構的影響
Yu-Chun Wang, Ker-Chun Lin, Wen-Yu Chien and Yung-Chih Wang
台灣地理位處環太平洋地震帶,且位於菲律賓海板塊與歐亞大陸板塊交界處,歐亞大陸板塊受菲律賓海板塊向西推擠,導致台灣東、西部產生多處斷層,大多呈南北走向。據中央地調所於2013年對臺灣活動斷層分布與地表變形觀測的調查結果顯示,台灣有20條第一類活動斷層與13條第二類活動斷層;並運用全球衛星定位系統(GPS)觀測地表變形發現,以花東地區的變形速度最大,約以每年6-8 cm向西偏北推擠。另由台灣人口分佈調查的統計結果發現,台灣約三分之一的人口居住在距斷層10公里範圍內。因此,在台灣的地震工程實務中,建築結構物受近斷層效應的影響為亟待面對與解決的重要議題。
觀察近斷層地震可發現,與遠域地震相較,除可能具較高的地震動值(加速度值)外,且在地震歷時有斷層破裂所造成的指向性效應(directivity effect)脈衝波(impulse wave),或斷層滑移效應產生的永久地表位移(fling),兩者皆有長週期速度脈衝(long-period velocity impulse)潛勢的特徵。若是結構週期與速度脈衝週期相近,可能對結構會造成的不利影響。就近斷層地震的指向性特徵而言,一般前指向性(forward directivity)較後指向性(back directivity)對結構的不利影響較為顯著。台灣於1999年集集地震之後,內政部營建署頒布之「建築物耐震設計規範與解說」 (內政部營建署,2005)乃至現行版本(內政部營建署,2011) ,為考量近斷層工址受近斷層地震作用的效應,是以中央地質調查所公布之第一類活動斷層進行危害度分析,藉由特徵斷層之地震規模密度函數配合傳統遠域地震均布危害度,決定近斷層因子NA、NV (分別為反應譜等加速度段以及等速度段的調整放大係數),直接增加原遠域設計加速度反應譜,以提升建築物的設計地震力需求。此調整方式僅反映前述近斷層地震特徵之高地震動值,但卻沒有考量近斷層地震速度脈衝的長週期特徵,因此無法反應長週期速度脈衝之近斷層地震的加速度反應譜形狀。針對具長週期速度脈衝指向性效應、斷層滑移效應的近斷層地震,有短時間內能量集中釋放的特徵,對結構反應需進一步探討。此外,隨著分析軟體的精進及電腦硬體運算速度的提升,為追求更精準、更具經濟效益的設計,特別是在隔、減震、超高層建築、特殊構造、或近斷層工址等無法掌握非線性行為等結構,可利用非線性動力歷時分析以獲得更精確的結構反應。然而,進行非線性動力歷時分析時,也需面臨地震紀錄選取和調整的議題。對於具長週期脈衝的近斷層地震而言,常用的地震紀錄調整方法中,相符法(matching)(實為人造地震(artificial earthquake)歷時)無法保有近斷層地震的長週期脈衝特性,為使調整後的地震紀錄與原始近斷層地震紀錄的頻率(或週期)特性相符,原則上應以縮放法(scaling)調整較為合理。目前國內規範僅簡單敘述非線性動力分析方法,並未特別提及近斷層地震地震紀錄選取及縮放方法。美國ASCE 7-16耐震設計相關規範中,雖規定近斷層地震須採用縮放法(scaling)調整,然而,此仍存在著近斷層地震反應譜與目標反應譜之顯著週期不一致之調整週期範圍的問題。本研究也探討國內建築物耐震設計規範第2.11節的地震力豎向分配,對於長週期(基本振動週期大於0.7秒)結構,在屋頂須額外增加一側力,此豎向分佈乃過去動力分析不發達年代,為獲得保守結構設計結果的做法。本研究採用動力全模態疊加法,評估不同週期結構的彈性動力地震力豎向分佈,並與國內現行豎向分佈比較其差異,且提出修訂建議。
本研究是以三棟分別為8層、15層、30層(分別代表一般樓高、中高樓高、高樓高)的鋼造抗彎構架結構系統建築,以模擬不同週期的結構物,並根據NIST GRC 11-917-15的計算公式建議採用7 筆地震紀錄,分別選取5筆1999年集集地震具長週期速度脈衝的近斷層地震紀錄,與2筆台灣具遠域地震特性的地震紀錄,進行非線性動力歷時分析。其中5筆長週期速度脈衝的近斷層地震紀錄中,包括具有指向性特性與斷層滑移特徵,及具有此兩種複合特徵的地震紀錄。本研究採用ETABS(2017年版)分析軟體進行非線性動力歷時分析,並採用ASCE 41-13的梁、柱塑鉸模型。作為分析用的地震紀錄是將原始地震紀錄以縮放法進行調整。縮放調整時,遠域地震的調整週期範圍介於0.2T1與1.5T1之間(其中T1為建築物基本振動週期),且包含90%振態參與質量所對應到的週期;近斷層地震的調整週期範圍介於0.2T0至1.2T0(其中,T0為該工址設計加速度譜轉角週期)。地震紀錄調整之目標加速度反應譜(target acceleration spectrum)採用近斷層工址考慮NA、NV放大因子的原設計加速度反應譜。對於近斷層地震的調整週期範圍主要採用設計反應譜短週期平台段(0.2T0至1.2T0)的觀點,乃認為與遠域地震相比,近斷層地震的長週期脈衝效應為額外效應,且不受結構物週期影響。基於前述分析條件對本研究3建築模型的非線性動力歷時分析結果顯示,就遠域地震的分析結果發現,高樓建築在較高樓層的變形需求相對於低樓層較大,此顯示樓高越高的建築,高模態效應越趨顯著。根據本研究結果,建議超過十五層之鋼結構建築宜採用非線性動力歷時分析檢核其樓層變形。另從近斷層地震的分析結果發現,指向性特徵之脈衝型地震會激發出結構高模態效應,對中高樓高及高樓高建築可能產生較不利的影響;斷層滑移引致永久地表位移的地震會使結構低樓層處產生明顯較大的層間位移角,因此,無論是一般樓高、中高樓高或是高樓高建築,在低樓層處產生嚴重破壞的潛勢相對較高。因此建議位於鄰近斷層的建築結構物,應進行非線性動力歷時分析,以考量脈衝型地震動特性、真實模擬結構非線性行為進行變形檢核。另外,近斷層工址建築物的興建需特別注意其適用性,並考量近斷層脈衝型地震對結構的負面影響。
針對用於靜力分析之地震橫力豎向分佈的研究中,是以彈性動力振態反應譜分析(elastic dynamic modal response spectrum analysis)法考慮100%的模態進行分析,並採用CQC(complete quadratic combination)振態疊加法,依此獲得的基底剪力經規範規定的靜力基底剪力調整後進行分析,並以此分析結果為比較基準。另分別採用現行國內建築物耐震設計規範(TBC-2011)與美國規範(ASCE7-16)規定的法規基底剪力與豎向分佈進行靜力分析。以前述3棟建築模型為標的,針對樓層剪力、傾覆力矩與樓層層間位移角三個物理量的結果進行分析比較。本研究結果顯示,若以100%的動力振態反應譜分析法的結果為基準,採用TBC-2011與ASCE7-16的靜力豎向分布,此3棟建築模型的各樓層剪力與傾覆力矩差距均較大,起引致之各層間位移角差距均較小(與動力振態分析結果比較均較保守)。隨著建築物樓層數的增加,TBC-2011的豎向分配方式在高樓層有明顯過於保守的現象。對於30層建築模型,TBC-2011的屋頂剪力比值最大達2.61,層間位移角比值最大為2.01;ASCE7-16的屋頂剪力比值最大達1.24,層間位移角最大僅1.42倍。因此,本研究建議國內現行建築物耐震設計規範的地震力靜力豎向分佈改採ASCE7-16的分佈方式,以均勻各樓層設計力的保守程度,可使在破壞潛勢較高的低樓層及中樓層處能提供較保守的設計,且高樓層處又不至於過度設計。