【摘要】：橋梁的上部結構通過基礎與地基相連,結構-基礎-地基構成了相互依賴的完整體系。在地震作用下,地震波經(jīng)過土的傳播作用于結構體系,地震工程實踐表明,考慮土-結構相互作用的橋梁體系地震響應分析是值得做的。但是,由于考慮土-結構相互作用的橋梁體系結構比較大,對其進行模擬分析時,計算時間長、內存需求大、計算效率較小甚至無法實現(xiàn)。為了解決該問題,本文采用多尺度建模方法對該類結構進行建模并對其地震響應進行分析,主要工作和結論如下:(1)本文基于結構多尺度建模理論,在同一結構模型中通過采用精細單元模擬結構的關鍵(或易損傷)部位,宏觀單元模擬其他部分,在此之后不同單元之間進行截面耦合,使不同單元之間的變形協(xié)調達到了一致。(2)由于不同單元在進行截面連接時會松弛一部分自由度,使多尺度模型較實際模型整體剛度小,因此本文通過修改宏觀單元剛度實現(xiàn)多尺度模型整體剛度的修正,旨在滿足工程實際要求;對比地震荷載作用下修正后多尺度模型與精細模型的位移、速度和加速度響應,驗證了修正后多尺度模型與工程實際之間的一致性。(3)合理的地震動輸入是保證結構地震響應的關鍵因素,對于考慮土-結構相互作用的整體橋梁體系而言,地震動的輸入應該采用地下某一深度的地震波而不是采用基于地表記錄的地震波。因此,本文采用Thomson-Haskell傳遞矩陣法,推導了地震波經(jīng)過層狀土體時的傳遞函數(shù),根據(jù)得到的傳遞函數(shù)和基于地表所記錄的地震波時程(EI Centro波和天津波),得到了相應的地下地震波,其正確性也被驗證,旨為后續(xù)結構的地震響應分析做準備。(4)通過比較分析地下地震動激勵下橋梁結構的位移響應、墩底剪力、滯回曲線和耗能能力等特征,探究了土體、縱向配筋率和配箍率等參數(shù)對橋梁體系的地震響應影響規(guī)律。結果表明:考慮土-結構相互作用后,土體對地震能量有一定的耗散作用,對橋梁的抗震性能需求有所降低,在橋梁抗震設計時應加以考慮;提高縱向配筋率,墩頂最大位移呈減小趨勢,墩底最大剪力呈增大趨勢,但當繼續(xù)增大縱向配筋率時,墩底混凝土先于鋼筋破壞,出現(xiàn)超筋破壞現(xiàn)象,墩底最大剪力反而下降,因此對橋墩進行配筋時,縱向配筋率不宜過大;增加配箍率,墩頂最大位移變化較小,墩底最大剪力在一定范圍內波動,總體來說配箍率對橋梁結構的耗能能力不及縱向配筋率的大,但不容忽略。
[Abstract]:The superstructure of the bridge is connected to the foundation through the foundation, and the structure-foundation-foundation constitutes a complete interdependent system. Seismic wave propagating through soil acts on structural system under earthquake action. Seismic engineering practice shows that the seismic response analysis of bridge system considering soil-structure interaction is worth doing. However, due to the large structure of bridge considering soil-structure interaction, the calculation time is long, the memory requirement is large, and the computational efficiency is low or even impossible. In order to solve this problem, the multi-scale modeling method is used to model this kind of structure and its seismic response is analyzed. The main work and conclusions are as follows: (1) based on the theory of multi-scale structural modeling, In the same structural model, fine elements are used to simulate the key (or vulnerable) parts of the structure, and macro elements are used to simulate the other parts, after which the cross-section coupling is carried out between the different elements. The deformation coordination among different elements is consistent. (2) because different elements relax some degrees of freedom in cross-section connection, the multi-scale model has less overall stiffness than the actual model. In this paper, the overall stiffness of the multi-scale model is modified by modifying the macro-element stiffness to meet the practical engineering requirements, and the displacement, velocity and acceleration responses of the modified multi-scale model and the refined model under earthquake load are compared. The consistency between the modified multi-scale model and the engineering practice is verified. (3) reasonable earthquake input is the key factor to ensure the seismic response of the structure, and for the whole bridge system, the soil-structure interaction is considered. Seismic waves at a certain depth of the ground should be used instead of seismic waves based on surface records. Therefore, using the Thomson-Haskell transfer matrix method, the transfer function of seismic wave passing through layered soil is derived. According to the obtained transfer function and the time-history (EI Centro wave and Tianjin wave recorded on the ground, the corresponding underground seismic waves are obtained. Its correctness has also been verified, which is intended to prepare for the seismic response analysis of subsequent structures. (4) by comparing and analyzing the displacement response, pier bottom shear, hysteretic curve and energy dissipation capacity of the bridge structure under ground motion excitation, the soil mass is explored. The effect of longitudinal reinforcement ratio and hoop ratio on seismic response of bridge system is studied. The results show that considering the soil-structure interaction, the soil has a certain dissipation of seismic energy, and the demand for seismic performance of the bridge is reduced, which should be taken into account in the seismic design of the bridge, and the longitudinal reinforcement ratio should be increased. The maximum displacement at the top of the pier decreases and the maximum shear at the bottom of the pier increases. However, when the ratio of longitudinal reinforcement is increased, the concrete at the bottom of the pier is destroyed before the reinforcement, and the failure of the superreinforcement occurs, but the maximum shear at the bottom of the pier decreases. Therefore, the longitudinal reinforcement ratio should not be too large when the pier is reinforced, the maximum displacement of the pier top changes little with increasing the hoop ratio, and the maximum shear force at the bottom of the pier fluctuates in a certain range. Generally speaking, the energy dissipation capacity of bridge structure is less than that of longitudinal reinforcement ratio, but it can not be ignored.
【學位授予單位】：河北工程大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U441

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