學術(shù)論文列表
Vertical-to-horizontal response spectral ratio for offshore ground motions: Analysis and simplified design equation
摘要：In order to study the differences in vertical component between onshore and offshore motions, the vertical-to-horizontal peak ground acceleration ratio (V/H PGA ratio) and vertical-to-horizontal response spectral ratio (V/H) were investigated using the ground motion recordings from the K-NET network and the seafloor earthquake measuring system (SEMS). The results indicate that the vertical component of offshore motions is lower than that of onshore motions. The V/H PGA ratio of acceleration time histories at offshore stations is about 50% of the ratio at onshore stations. The V/H for offshore ground motions is lower than that for onshore motions, especially for periods less than 0.8 s. Furthermore, based on the results in statistical analysis for offshore recordings in the K-NET, the simplified V/H design equations for offshore motions in minor and moderate earthquakes are proposed for seismic analysis of offshore structures.
設(shè)置BRB橋梁排架墩基于位移抗震設(shè)計方法
摘要：基于"保險絲"和"損傷控制"的抗震設(shè)計理念,提出在橋梁雙柱式排架墩中通過設(shè)置屈曲約束支撐(BRB)以提高其橫橋向抗震性能的構(gòu)想。首先從獲得"抗震能力"的角度對設(shè)置BRB橋梁排架墩的抗震設(shè)計參數(shù)進行系統(tǒng)性分析,推導出與剪跨比和墩柱間距與直徑(邊長)比相關(guān)的BRB核心段最大和最小長度取值范圍;再從求解"地震需求"角度建立了設(shè)置保險絲的(SDOF)主結(jié)構(gòu)體系彈塑性反應譜基本方程,分析該體系的非線性地震反應一般規(guī)律;然后,基于體系的"抗震能力"和"地震需求",發(fā)展了設(shè)置BRB的橋梁排架墩基于位移的抗震設(shè)計方法,并結(jié)合一個具體橋梁排架墩實例說明建議設(shè)計方法的可行性。
Rapid repair techniques for severely earthquake-damaged circular bridge piers with flexural failure mode
摘要：In this study, three rapid repair techniques are proposed to retrofit circular bridge piers that are severely damaged by the flexural failure mode in major earthquakes. The quasi-static tests on three 1:2.5 scaled circular pier specimens are conducted to evaluate the efficiency of the proposed repair techniques. For the purpose of rapid repair, the repair procedure for all the specimens is conducted within four days, and the behavior of the repaired specimens is evaluated and compared with the original ones. A finite element model is developed to predict the cyclic behavior of the repaired specimens and the numerical results are compared with the test data. It is found that all the repaired specimens exhibit similar or larger lateral strength and deformation capacity than the original ones. The initial lateral stiffness of all the repaired specimens is lower than that of the original ones, while they show a higher lateral stiffness at the later stage of the test. No noticeable difference is observed for the energy dissipation capacity between the original and repaired pier specimens. It is suggested that the repair technique using the early-strength concrete jacket confined by carbon fiber reinforced polymer (CFRP) sheets can be an optimal method for the rapid repair of severely earthquake-damaged circular bridge piers with flexural failure mode.
Experimental and numerical investigations on the seismic behavior of bridge piers with vertical unbonded prestressing strands
摘要：In the performance-based seismic bridge design, piers are expected to undergo large inelastic deformations during severe earthquakes, which in turn can result in large residual drift and concrete crack in the bridge piers. In this paper, longitudinal unbonded prestressing strands are used to minimize residual drift and residual concrete crack width in reinforced concrete (RC) bridge piers. Seven pier specimens were designed and tested quasi-statically and the numerical simulations were carried out. The effectiveness of using vertical unbonded prestressing strands to mitigate the residual drift and concrete crack width of RC bridge piers are examined and discussed in detail. It is found that the residual drift and residual concrete crack width of the piers can be reduced significantly by using the prestressing strands. Moreover, the strands can increase the lateral strength of the piers while have little influence on the ductility capacity of the piers. The hysteretic curves, residual drifts and strand stress of the piers predicted by the numerical model agree well with the testing data and can be used to assess the cyclic behavior of the piers.
Research on the influencing factors for residual displacements of RC bridge columns subjected to earthquake loading
摘要：Following the 1995 Kobe earthquake, many RC bridge columns were demolished due to a residual drift ratio of more than 1.75 % even though they did not collapse. The residual drift ratio is a quantitative index for the performance objective of reparability in the bridge seismic design. Numerical models of the columns are built to study the factors that influence the residual displacement of RC bridge columns. In these models, both column bending and bar pulling out deformation are considered using the fiber column-beam element and zero-length section element, respectively. Then, nonlinear time history analyses are performed. The factors that influence column residual displacement, such as the characteristics of ground motion, the structural responses (the maximum lateral drift ratio and the displacement ductility factor), and the structural characteristics (the aspect ratio and the longitudinal reinforcement ratio) are investigated. It is found that the near-fault ground motion induces a larger residual drift ratio than the far-fault ground motion. The residual drift ratio becomes larger due to the increase of the maximum lateral drift ratio, the displacement ductility factor, and the aspect ratio. Further, a larger longitudinal reinforcement ratio can induce a larger residual drift ratio due to the contribution of the bar pulling out deformation.
粘彈性人工邊界在地震工程中應用研究綜述
摘要：介紹粘彈性人工邊界在結(jié)構(gòu)-地基動力相互作用等問題中應用的研究現(xiàn)狀。重點敘述了粘彈性人工邊界在有限元計算中的實現(xiàn)方法及其在地震工程中的應用。粘彈性人工邊界方法具有方便實現(xiàn)、計算精度高、穩(wěn)定性強等優(yōu)點,是解決近場波動問題的一種重要手段。隨著粘彈性人工邊界理論及其在有限元軟件中的應用日漸成熟,其在工程抗震分析等方面將具有廣闊的應用前景。
考慮橋墩剪切破壞的不規(guī)則橋梁排架抗震分析模型
摘要：基于OpenSees數(shù)值分析平臺的纖維梁柱、剪切彈簧和轉(zhuǎn)動彈簧單元,建立了考慮橋墩剪切破壞的不規(guī)則橋梁排架抗震數(shù)值分析模型.其中纖維梁柱單元模擬橋墩、蓋梁彎曲變形,剪切彈簧單元模擬橋墩剪切變形,轉(zhuǎn)動彈簧單元模擬縱筋拔出變形.基于圓形截面橋墩抗震試驗結(jié)果,并結(jié)合數(shù)值分析手段建立了橋墩剪切破壞時塑性鉸區(qū)轉(zhuǎn)角計算公式.并以此公式為基礎(chǔ),監(jiān)測數(shù)值模型中橋墩剪切破壞,剪切破壞前橋墩以彎曲反應為主,剪切破壞后橋墩側(cè)向強度和剛度發(fā)生顯著退化.最后以3座實際不規(guī)則橋梁排架為工程背景,進行了排架橫橋向地震作用下的滯回性能分析.研究表明,所建立的抗震分析模型可有效模擬由于橋墩剪切破壞造成的強度和剛度退化,為不規(guī)則橋梁結(jié)構(gòu)抗震性能分析提供了依據(jù).
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彎曲破壞型鋼筋混凝土橋墩地震變形成分及影響因素
摘要：鋼筋混凝土橋墩擬靜力試驗表明,彎曲破壞型橋墩墩頂位移主要由彎曲變形、滑移變形成分構(gòu)成。為進一步探討地震荷載作用下彎曲破壞型橋墩地震變形成分及其影響因素,首先基于Lehman以及李貴乾的橋墩試件擬靜力試驗,利用OpenSees平臺采用纖維梁柱單元模型附加零長度截面單元對試驗滯回曲線和墩頂變形成分進行數(shù)值模擬;其次建立原型橋墩數(shù)值模型,考慮近斷層和遠斷層地震動進行了非線性動力時程分析,探討了最大側(cè)移角、位移延性系數(shù)等結(jié)構(gòu)反應參數(shù),以及剪跨比、縱筋配筋率等構(gòu)件特征參數(shù)對橋墩地震變形成分的影響。結(jié)果表明,墩頂總位移中縱筋粘結(jié)滑移成分隨最大側(cè)移角和位移延性的增大而增大,隨剪跨比和縱筋配筋率的增大而減小。考慮縱筋粘結(jié)滑移的數(shù)值模型與僅考慮彎曲變形纖維梁柱單元模型相比,將增大橋墩的地震位移反應。
海底地震動特性及相關(guān)譜研究
摘要：利用日本K-NET與美國SEMS臺網(wǎng)中海底強震記錄研究了海底地震動特性。通過分析水平反應譜、豎向與水平加速度反應譜的比譜和彈塑性反應譜,比較了海底與陸地地震動的區(qū)別。發(fā)現(xiàn)海底豎向地震動的峰值加速度明顯更低。在大于0.2s的周期段,海底水平地震動反應譜大于陸地譜值,而且海底譜具有更長的特征周期,并隨震中距增長而增大。此外,海底地震動的豎向與水平加速度反應比譜與陸地地震動的差異很大,在小于1s的中短周期段海底地震動的比譜明顯更小。根據(jù)不同的震級與震中距的真實地震動記錄,提出了中等地震下不同震中距海底地震動比譜的簡化設(shè)計方程。最后,比較了海底與陸地地震動的彈塑性反應譜,可知總體上海底與陸地的等延性強度折減系數(shù)譜差異不大。
基于位移的中等跨徑減隔震橋梁抗震設(shè)計方法
摘要：為了給新建減隔震橋梁設(shè)計和既有橋梁減隔震加固設(shè)計提供參考,以中等跨徑的公路橋梁為研究對象,結(jié)合中國的抗震設(shè)計規(guī)范和減隔震支座技術(shù)標準,提出一種基于位移的抗震設(shè)計方法。該設(shè)計方法給出了選擇減隔震支座和估計設(shè)計目標位移的方法,從串聯(lián)體系受力特點的角度提出了橋墩-支座體系的位移分配方法,設(shè)計中允許橋墩屈服,但通過控制損傷程度確保震后不需要修復,也要求進行支座的安全性檢驗。構(gòu)造了具有不同外形特征和不同跨徑的36座連續(xù)梁橋進行減隔震設(shè)計,并通過動力時程分析驗證了設(shè)計方法的可行性。研究結(jié)果表明:提出的設(shè)計方法能夠較好地預測主梁的位移需求,易于把握支座和橋墩的性能狀態(tài);該設(shè)計方法也適用于非規(guī)則橋梁,可通過橫向位移變異系數(shù)判斷主梁的橫向位移變形模式。
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