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Probabilistic seismic response and uncertainty analysis of continuous bridges under near-fault ground motions

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Frontiers of Structural and Civil Engineering 2019年第6期13卷 1510-1519页

作者： Hai-Bin MA Wei-Dong ZHUO Davide LAVORATO camillo nuti Gabriele FIORENTINO Giuseppe Carlo MARANO Rita GRECO Bruno BRISEGHELLA College of Civil Engineering Fuzhou UniversityFuzhou 350108China Department of Architecture Roma Tre UniversityRoma 00154Italy College of Civil Engineering and Architecture Politecnico di Bari UniversityBari 70126Italy

Performance-based seismic design can generate predictable structure damage result with given seismic ***,there are multiple sources of uncertainties in the seismic design process that can affect desired performance *** paper mainly focuses on the effects of near-fault pulse-like ground motions and the uncertainties in bridge modeling on the seismic demands of regular continuous highway *** modeling a regular continuous bridge with OpenSees software,a series of nonlinear dynamic time-history analysis of the bridge at three different site conditions under near-fault pulse-like ground motions are carried *** relationships between different Intensity Measure(IM)parameters and the Engineering Demand Parameter(EDP)are *** selecting the peak ground acceleration as the most correlated IM parameter and the drift ratio of the bridge column as the EDP parameter,a probabilistic seismic demand model is developed for near-fault earthquake ground motions for 3 different site *** this basis,the uncertainty analysis is conducted with the key sources of uncertainty during the finite element *** the results are quantified by the"swing"base on the specific distribution range of each uncertainty parameter both in near-fault and far-fault *** the ground motions are selected from PEER database,while the bridge case study is a typical regular highway bridge designed in accordance with the Chinese Guidelines for Seismic Design of Highway *** results show that PGA is a proper IM parameter for setting up a linear probabilistic seismic demand model;damping ratio,pier diameter and concrete strength are the main uncertainty parameters during bridge modeling,which should be considered both in near-fault and far-fault ground motion cases.

关键词： continuous bridge probabilistic seismic demand model Intensity Measure near-fault uncertainty

Design of Dissipative Braces for an Existing Strategic Building with a Pushover Based Procedure

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Journal of Civil Engineering and Architecture 2014年第7期8卷 815-823页

作者： Alessandro Vittorio Bergami camillo nuti Department of Architecture University of Roma Tre Rome 00153 Italy

The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. An iterative displacement-based procedure, based on capacity spectrum, to design dissipative bracings for seismic retrofitting of the frame structures is described, and some applications are discussed. The procedure can be used with any typology of dissipative device and for different performance targets. In this work, the procedure has been applied, with both traditional pushover （load profile proportional to first mode） and multimodal pushover, to an existing RC （reinforced concrete） frame building. In the application, the buckling restrained braces have been used in order to prevent damages to both the structure and non structural elements. The use of multimodal pushover proves to be more effective than pushover based on single mode in case of medium rise RC frame building （higher than 30 m） but, once this building is retrofitted, and therefore regularized, with a bracing system, the difference between using monomodal or multimodal pushover becomes insignificant.

关键词： Dissipative braces earthquake engineering energy dissipation seismic retrofitting.

Asynchronous earthquake strong motion and RC bridges response

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Journal of Traffic and Transportation Engineering(English Edition) 2018年第6期5卷 454-466页

作者： Davide Lavorato Gabriele Fiorentino Alessandro Vittorio Bergami Bruno Briseghella camillo nuti Silvia Santini Ivo Vanzi Department of Architecture Roma Tre University College of Civil Engineering Fuzhou University Department of Engineering and Geology University of Chieti-Pescara "G.d'Annunzio"

The dynamic response of long structures(e.g., bridges) is sensitive to the spatial variability of strong ground motion(asynchronous motion). Ground motion differences increase from point to point with increasing foundation distance. This latter is due to two physical phenomena: soil-wave interaction, that causes the loss of coherence and local amplification; wave traveling with finite velocity, that causes signals time lag. This ground motion variability produces a different structural demand compared to the synchronous one,which is the only one considered by designers in the majority of cases. A few codes consider this type of actions, therefore further research efforts are necessary. In this study,asynchronous ground motions are generated by means of a new generation procedure implemented in the software GAS 2.0 using as input the simultaneous strong motion records from the April 6 th, 2009, L’Aquila(Italy) at the seismic stations AQA and AQV, located in the Aterno River valley. These records are used to calibrate the generation model and to produce sets of asynchronous earthquake sampling. The asynchronous earthquake sets are applied on a typical highway reinforced concrete bridge to study its dynamic response considering two different configurations: non-isolated with traditional supports and isolated bridge with lead rubber bearings. The bridge is placed in two positions along the wave propagation direction: a position near one recording station and a position between the two stations to consider local soil effects. The response parameters investigated are the maximum relative displacements of soil and deck. The results show that there is animportant variation of relative displacement along the direction of wave propagation due to asynchronous motion with effects that designer should consider for the structural details design of isolated and non-isolated bridges.

关键词： Asynchronous motion Bridges Seismic response Earthquake spatial variability

带小直径纵筋并外包CFRP的RC圆墩抗震性能研究

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中国公路学报 2022年第2期35卷 124-135页

作者：薛俊青 DAVIDE Lavorato 聂尚杰陈俊臻 BRISEGHELLA Bruno nuti camillo 福州大学土木工程学院福建福州350108 福州大学福建省土木工程多灾害防治重点实验室福建福州350108 罗马第三大学建筑学院拉齐奥大区罗马00184

桥梁震害调查显示,钢筋混凝土(RC)桥墩易受损,影响震后救援和灾后重建。采用小直径纵筋替换受损纵筋并外包碳纤维布(CFRP)的技术修复受损桥墩可缩短震后修复周期,节省重建费用。以某不规则连续梁桥的RC圆墩为工程背景,选择小直径纵筋的... 详细信息

桥梁震害调查显示,钢筋混凝土(RC)桥墩易受损,影响震后救援和灾后重建。采用小直径纵筋替换受损纵筋并外包碳纤维布(CFRP)的技术修复受损桥墩可缩短震后修复周期,节省重建费用。以某不规则连续梁桥的RC圆墩为工程背景,选择小直径纵筋的长度和直径、外包CFRP层数为参数,开展7根缩尺比例为1∶6的RC圆墩试件的拟静力试验;选用OpenSees建立有限元模型,采用试验结果验证其准确性,并开展参数分析。研究结果表明:设置小直径纵筋的桥墩的塑性变形集中在小直径纵筋高度范围内,桥墩破坏被限制在塑性铰区域内;与未设置小直径纵筋的桥墩相比,小直径纵筋使桥墩承载力降低20%~27%,但桥墩位移延性提高42%~85%,曲率延性提高47%~242%,耗能性能提高32%~56%;在满足桥墩承载力设计要求的情况下,使用小直径纵筋可有效提高桥墩抗震性能;设置小直径纵筋的桥墩在小直径纵筋区域内的实测CFRP最大应变明显大于未设置的试件,说明对设置小直径纵筋的桥墩外包CFRP,可防止桥墩过早破坏,提高延性;随着小直径纵筋长度增大或直径减小,桥墩耗能性能先增大后减小;建议以钢筋疲劳寿命需求为下限,塑性铰长度为上限选择小直径纵筋长度;选择满足保证塑性铰以外的纵筋受力始终在弹性范围内的条件下的最大直径为小直径纵筋直径;增大修复区域的混凝土强度可弥补设置小直径纵筋造成的桥墩承载力降低。

关键词：桥梁工程抗震性能拟静力试验钢筋混凝土圆形桥墩小直径纵筋碳纤维布

中欧规范RC桥墩抗震设计及验算方法对比研究

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世界地震工程 2022年第3期38卷 127-137页

作者：薛俊青邵恒陈俊臻 BRISEGHELLA Bruno nuti camillo 黄福云福州大学土木工程学院福建福州350108 罗马第三大学建筑学院罗马00184

地震作用下钢筋混凝土(RC)桥墩容易损坏。为完善RC桥墩的抗震设计及验算方法,对比最新中国和欧洲规范中关于RC桥墩的延性抗震设计及验算方法的不同之处。基于Midas/Civil软件所建立的常规连续梁桥有限元模型,对比分析采用中欧规范开展... 详细信息

地震作用下钢筋混凝土(RC)桥墩容易损坏。为完善RC桥墩的抗震设计及验算方法,对比最新中国和欧洲规范中关于RC桥墩的延性抗震设计及验算方法的不同之处。基于Midas/Civil软件所建立的常规连续梁桥有限元模型,对比分析采用中欧规范开展的RC桥墩延性抗震设计及验算结果。结果表明:中欧规范中关于RC桥墩的延性抗震设计理念、抗剪和变形验算方法及延性构造细节均有区别。基于中欧规范设计的RC桥墩配筋情况存在差异。与中国规范相比,欧洲规范关于RC桥墩的横向钢筋配筋率和纵筋最小配筋率要求较高,有利于保证结构的抗剪强度和延性;箍筋最大间距要求较低,不利于防止纵筋压曲。

关键词：钢筋混凝土桥墩抗震设计及验算对比研究中欧规范配筋率

钢木混合结构在不同性能水准下的层间位移角限值

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建设科技 2019年第17期 64-68,79,3页

作者：王希珺 Briseghella Bruno nuti camillo 李征孙永良同济大学建筑工程系上海200092 福州大学土木工程学院福州350116 同济大学建筑设计研究院(集团)有限公司上海200092

钢木混合结构是一种主要由钢框架、内填轻型木剪力墙和钢木混合楼盖组成的新型结构体系。抗震设计中,层间位移角是衡量结构和非结构破坏程度的重要指标。为获得钢木混合结构在不同性能水准下的层间位移角限值、定义钢木混合抗侧力体系... 详细信息

钢木混合结构是一种主要由钢框架、内填轻型木剪力墙和钢木混合楼盖组成的新型结构体系。抗震设计中,层间位移角是衡量结构和非结构破坏程度的重要指标。为获得钢木混合结构在不同性能水准下的层间位移角限值、定义钢木混合抗侧力体系的屈服点,在有限元软件OpenSees中对120个不同参数的钢木混合抗侧力体系进行推覆模拟,得到具有95%保证率的屈服位移角为0.48%;为定义钢木混合结构倒塌极限状态性能点,选取10条不同地震记录,在有限元软件OpenSees中对考虑不同木剪力墙和钢框架抗侧刚度比的三层和六层钢木混合结构进行增量动力分析,得到具有95%保证率的倒塌极限状态层间位移角为2.43%。基于分析结果和已有试验现象,建议钢木混合结构立即居住和防止倒塌性能水准层间位移角限值分别取0.5%和2.5%。

关键词：钢木混合结构层间位移角限值增量动力分析立即居住防止倒塌