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  • 學位論文

單跨樁基礎橋梁模型之振動台實驗研究

Shaking table study on a single span pile foundation bridge model

指導教授 : 張國鎮

摘要


本研究探討單跨簡支含樁基礎之橋梁受沖刷裸露後之耐震行為,藉由雙砂箱剪力盒與振動台實驗,檢視橋柱與樁基礎之需求容量關係。實驗設計係參考公路橋梁耐震設計規範補充研究完成,提供合理之結構週期與柱、樁彎矩強度比。試體包含I型加勁鋼梁、U形鋼帽梁、構架式圓形鋼管橋墩、方形鋼基礎版、及鋁製空心圓管樁。支承條件採用橡膠支承模擬鉸接端,滾接端則以滾珠支承模擬。實驗規劃分為固定基礎及基礎裸露兩類,固定基礎者係將鋼基礎版鎖固於振動台面,且其下無樁基礎;基礎裸露者乃將鋁樁鎖固於砂箱剪力盒底部,並以相對密度50%之乾性石英砂逐層蓋覆。實驗主要參數以樁徑之倍數代表沖刷深度,符號系統分別以H、R、D說明鉸接端樁基礎、滾接端樁基礎、及樁徑,共計H0D-R0D、H0D-R3D、H3D-R3D、H3D-R6D、H6D-R6D等5組。輸入地表加速度歷時包含El Centro地震、集集地震TCU076測站及與規範反應譜相符之人造地震歷時,最大地表加速度範圍為100gal至350gal。實驗過程主要紀錄結構及土層之加速度與位移反應,並由樁身與柱底之應變計可間接求得其於振動過程中之彎矩與位移曲線函數,提供需求容量比(D/C ratio)之檢核。 實驗結果顯示,固定基礎之橋柱須能承擔較高的彎矩需求容量比,相較於基礎裸露者為一保守的設計條件。隨樁基礎裸露程度增加,結構顯著週期亦增加,大梁加速度則恰成相反,但大梁位移因與反應譜特性相關而無固定趨勢。相同地震作用下,當樁基礎裸露增加後,樁體最大彎矩發生位置越趨朝樁底方向移動,並非位於樁頂。如根據柱、樁彎矩之需求容量比檢討橋梁安全時,樁體彎矩比值之變化較小,但仍受地震特性影響須個案檢討,惟柱身彎矩比均呈現下降。如根據柱、樁之變形檢討橋梁安全時,橋柱相對位移放大趨勢則較樁明顯,應與基礎裸露後基礎版之旋轉貢獻有關。整體而言,當基礎裸露之橋梁受地震作用時,宜整體檢視柱、樁破壞模式轉移現象,尤以樁體彎矩及橋柱相對位移為檢查重點。 本研究另參考公路橋梁耐震評估與補強準則,建構橋梁分析模型探討含土壤彈簧模型之結構週期。初步結果顯示,無基礎裸露者之分析週期與實驗週期相近,但隨裸露程度增加則不盡理想,未來宜針對土壤性質適度模擬,以期許對全橋受震反應獲得合理與準確的評估。

並列摘要


This study investigated the seismic performance and soil-structure interaction of a scoured bridge with exposed pile foundation by dual biaxial laminar shear boxes and shaking table tests. The simply-supported bridge model was comprised of an I-section girder representing the superstructure, and two portal frames with cap-beam and circular tubes as substructure, individually supported by a massive block and single pipe as pile cap and pile foundation. Underneath the girder, two elastomeric rubber pads at left end stand for hinge condition, while a set of three rolling bearings at right end behaved ideal roller. The material for the bent, pile, and soil is steel, aluminum, and dry silica sand with relatively density of 50%, respectively. The pile tip was bolted at the bottom of the shear box. However, the pile is designated to be scoured as a ratio pile diameter (D) at either hinge-end (H) or roller-end (R) Category: H0D-R0D, H0D-R3D, H3D-R3D, H3D-R6D, H6D-R6D. The input ground motions included white noise of 30gal, acceleration records from El Centro, TCU076 station in Chi-Chi earthquake, and one spectrum-compatible time history converted from TCU076. The peak ground acceleration started from 100 gal and achieved 350 gal. Strain gauges and accelerometers were positioned along the height of pile surface. The pile and pier moment can calculate by strain gauges, and check the demand capacity ratio of structure. Both acceleration and displacement at girder, cap-beam , pile cap and frame of shear-box were also measured, the structure responses can be observed. Based on the experimental results, the general observation demonstrated that the structural period shifted longer as the scoured depth increased, as an evidence to explain why the response of maximum displacement of girder and column is getting larger while the maximum acceleration is getting smaller. Therefore, structural safety issue on the allowable criteria of column ductility and pile strength should be addressed and verified from rigorous analytical simulations.

參考文獻


[6]賴姿妤,「樁基礎沖刷橋梁模型之振動台試驗研究」,台灣大學土木工程學研究所碩士論文,民國100年6月
[17]周贊翔,「樁基礎沖刷橋梁模型之樁土互制研究」,台灣大學土木工程學研究所碩士論文,民國101年6月
[7]張國鎮、王修駿、劉光晏、陳家漢,「樁基礎沖刷橋梁模型之振動台試驗研究(II)」,國家地震工程研究中心研究報告(報告編號:NCREE-12-026),民國101年12月。
[3]Kohji Tokimatsua, Hiroko Suzuki, Masayoshi Sato(2005),.「Effects of Inertial and Kinematic Interaction on Seismic Behavior of Pile with Embedded Foundation」,Soil Dynamics and Earthquake Engineering,25,pp.753-762(accepted on 2004/11)
[13]Designation:D4253-00,「Standard Test Methods for Maximum Index Density and Unit Weight of Soils Using a Vibratory Table」,ASTM.

被引用紀錄


劉俊仁(2015)。受沖刷橋梁可靠度設計方法研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2015.02295
陳威宇(2015)。樁基礎橋梁含功能性支承之振動台試驗研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2015.01344
陳志豪(2014)。考量等效沖刷載重之橋梁可靠度設計方法研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2014.01696
曾子俊(2014)。橋梁含功能性支承與直接基礎之振動台試驗研究〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342%2fNTU.2014.00222
戴育錡(2015)。受沖刷橋梁之半主動結構控制〔碩士論文,國立中央大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0031-0412201512034690

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