水平双向地震作用下薄壁方形截面钢桥墩#br# 抗震性能试验及实用算法研究

钢板局部失稳破坏是钢桥墩结构典型的地震失效模式之一,但目前仍缺乏既能考虑局部失稳影响,又可方便用于工程设计的结构地震反应计算方法。通过对2个薄壁方形截面钢桥墩试件施加沿斜向的水平反复荷载,研究结构的地震破坏形式和抗震性能;在钢材修正双曲面滞回模型的基础上,通过对结构参数分析结果的数据拟合,建立考虑钢板局部失稳影响的方形截面钢桥墩纤维模型算法。结果表明：薄壁方形截面钢桥墩结构在水平双向地震作用下,首先会发生墩底钢板局部失稳,在荷载达到最高点后墩底焊缝处出现超低周疲劳破坏,在两种地震破坏的共同作用下结构承载力迅速下降;通过与试验结果的对比,验证结构地震有效损伤域Ld内的纤维单元采用等效滞回模型能准确反映钢板的局部失稳效应,为工程设计提供一种高精度的实用计算方法。     

Seismic design requirements for reinforced concrete piers considering aftershock-induced seismic hazard

The main purpose of this study is to develop an estimation procedure of seismic design level setting for reinforced concrete (RC) piers considering aftershock-induced seismic hazards. This work develops an assessment method of the seismic hazards induced by aftershocks and takes an example of the Chi–Chi Earthquake in Taiwan. The number of aftershocks is assumed to follow the modified Gutenberg–Richter law with lower and upper bounds when analysing the cumulative density function of the magnitude of the aftershock within a specified post-mainshock period for the earthquake. Additionally, this work considers the spatial uncertainty in the hypocentres of aftershocks to assess the aftershock-induced seismic hazards. Fragility curves and residual factors of damaged RC piers are used in the transition probability matrix of Markov Chain model for considering the cumulative damage induced by aftershocks by incorporating uncertainty into aftershock events, as well as into structural capacity and residual factors corresponding to a specified damage state, the exceedance probabilities for various damage states can be estimated using Markov Chain model and Monte Carlo Simulation. Finally, in the case study, the proposed procedure is used to determine the important factor in the preliminary seismic design of typical RC piers for the Chi–Chi Earthquake in Taiwan.     

Hybrid intelligent inference model for enhancing prediction accuracy of scour depth around bridge piers

Bridge-pier scouring is a main cause of bridge failures. Thus, accurately predicting the scour depth around bridge piers is critical, both to specify adequate depths for new bridge foundations and to assess/monitor the safety of existing bridges. This study proposes a novel artificial intelligence (AI) model, the intelligent fuzzy radial basis function neural network inference model (IFRIM), to estimate future scour depth around bridge piers. IFRIM is a hybrid of the radial basis function neural network (RBFNN), fuzzy logic (FL), and the artificial bee Cclony (ABC) algorithm. In the IFRIM, FL is used to handle the uncertainties in input information, RBFNN is used to handle the fuzzy input–output mapping relationships, and the ABC search engine employs optimisation to identify the most suitable tuning parameters for RBFNN and FL based on minimal error estimation. A 10-fold cross-validation method finds that the IFRIM model achieves at least 21% and 14.5% reductions in root mean square error and mean absolute error values, respectively, compared with other AI techniques. Study results support the IFRIM as a promising new tool for civil engineers to predict future scour depth around bridge piers.     

Parametric study of seismic performance of super-elastic shape memory alloy-reinforced bridge piers

One of the important measures of post-earthquake functionality of bridges after a major earthquake is residual displacement. In many recent major earthquakes, large residual displacements resulted in demolition of bridge piers due to the loss of functionality. Replacing the conventional longitudinal steel reinforcement in the plastic hinge regions of bridge piers with super-elastic shape memory alloy (SMA) could significantly reduce residual deformations. In this study, numerical investigations on the performance of SMA-reinforced concrete (RC) bridge bents to monotonic and seismic loadings are presented. Incremental dynamic analyses are conducted to compare the response of SMA RC bents with steel RC bents considering the peak and the residual deformations after seismic events. Numerical study on multiple prototype bridge bents with single and multiple piers reinforced with super-elastic SMA or conventional steel bars in plastic hinge regions is conducted. Effects of replacement of the steel rebar by SMA rebar on the performance of the bridge bents are studied. This paper presents results of the parametrical analyses on the effects of various design and geometric parameters, such as the number and geometry of piers and reinforcement ratio of the RC SMA bridge bents on its performance.     

某铁路特大桥桥墩加固设计

某铁路特大桥部分桥墩在施工过程中出现不同程度的水平、竖向和斜向裂缝,通过综合分析,决定对桥墩裂缝进行深层灌胶处理后,再采用置换高强加固型混凝土的方法进行裂缝封闭及对整体结构进行加固。为论证该加固方案的可靠性,采用ANSYS有限元软件进行模拟分析,分析了桥墩在未开裂工况、开裂工况、加固后工况下的应力、线刚度及偏心的变化。结果表明,该加固方案是安全可靠的,可供同类桥墩裂缝加固设计参考。     

荷泽南华康城住宅小区结构抗震措施浅析

由于菏泽地区是地震多发区,南华康城在结构方面从地基到主体采取各种措施,努力提高小区内住宅的的抗震性,给住户提供一个舒适、宜居、安全可靠的住宅。     

钢管混凝土高桥墩的极限承载力分析

钢管混凝土构件已经被广泛应用于土木工程,但用作桥墩还很少有文献报道。基于钢材和混凝土的本构关系,采用ABAQUS有限元软件对铜管混凝土高桥墩进行荷载一变形的全过程分析,确定其极限承载力,并对影响极限承载力的一些因素进行了分析。研究发现：提高钢材和混凝土的屈服强度以及构件的含钢率可以增大极限承载力,而自重的影响相对较小。     

超百米高低墩连续刚构铁路桥设计

文章针对叙大铁路三槽湾特大桥主桥(68+128+68)的预应力混凝土连续刚构,介绍了墩高超百米的高低墩刚构桥设计,分析计算了高低墩大跨连续刚构桥的静力特性和主桥车桥动力响应,对解决高低墩大跨连续刚构桥设计时刚度差的问题,以及梁部应力对高低墩的应力分配问题作了合理的实践,对山区铁路高桥设计具有较高的参考价值。     

近断层地震动下摇摆-自复位桥墩地震反应分析

为讨论摇摆-自复位（Rocking Self-Centering,RSC）桥墩在近断层地震动下的地震反应,基于OpenSees数值分析平台建立了RSC桥墩抗震分析模型。同时建立了普通钢筋混凝土（Reinforced Concrete,RC）桥墩,配置竖向无粘结预应力筋（Unbonded Prestressed Reinforced Concrete,PRC）桥墩的抗震分析模型作为对比。对各模型输入近断层地震动记录,进行增量动力分析。以墩顶最大位移角、残余位移角、预应力筋最大应力为考察目标,对比分析了不同墩高（剪跨比分别为2、4和6）、不同桥墩类型（RSC、RC和PRC桥墩）时各桥墩的地震反应。结果表明：随着耗能钢筋配筋率增加,RSC桥墩墩顶最大位移角和预应力筋最大应力均减小;RSC和PRC桥墩均可有效减少桥墩震后残余位移角。耗能钢筋配筋率与PRC桥墩纵筋配筋率接近的RSC桥墩,两者的最大墩顶位移角、残余位移角和预应力筋应力水平均接近。无论是RSC桥墩还是PRC桥墩,当剪跨比大于等于6.0时,易发生预应力筋失效。为避免预应力筋失效引起RSC桥墩产生过大的墩顶残余变形,RSC桥墩中耗能钢筋配筋率不宜低于0.75%。     

爆炸荷载下钢管混凝土墩柱的动力响应研究

设计并制作了3根普通钢管混凝土墩柱和1根复式中空钢管混凝土墩柱,进行了TNT药量分别为3 kg和50 kg的3发4工况静爆试验,获得构件的迎爆面及背爆面的柱面超压分布、残余变形以及最终破坏形态,结合有限元分析,研究了爆炸荷载下钢管混凝土墩柱的动态响应、破坏模态及参数影响。研究表明：50 kg TNT作用下、比例距离为0.14 m/kg^1/3时,外径同为273 mm、壁厚为7 mm的普通钢管混凝土墩柱抵抗爆炸荷载的变形能力优于中空钢管内径为50 mm、壁厚为4 mm的复式钢管混凝土墩柱;基于试验结果建立了多物质流固耦合的数值模拟方法,可有效模拟钢管混凝土墩柱在爆炸荷载下的动态响应;钢管混凝土墩柱三种典型破坏形态分别是：低超压峰值-高持时发生弯曲破坏、高超压峰值-低持时发生剪切破坏及介于两种情况之间的弯剪破坏;炸药当量为50 kg,比例距离z>0.3 m/kg^1/3时,爆炸荷载下试件柱的残余变形可忽略不计;核心混凝土强度等级的增强以及含钢率的提高,可有效降低柱中点水平残余变形;提高钢管屈服强度,可降低柱中残余变形,当钢材强度等级≥345 MPa时,继续增大屈服强度对提高钢管混凝土墩柱的抗爆性能意义不大。