钢筋混凝土桥墩基于位移的抗震设计方法

通过改进能力谱法,给出了一个可以实现“小震不坏、中震可修和大震不倒”多级性能目标的钢筋混凝土桥墩直接基于位移的抗震设计方法。首先以钢筋和混凝土的应变幅值建立了钢筋混凝土桥墩不同破损极限状态的量化准则,并基于曲率延性系数和位移延性系数关系转化为墩顶位移的表述形式。再以屈服位移和位移延性系数作为设计参考变量,采用屈服谱加速度和屈服位移(Ay-Dy)格式的地震需求谱求解系统在不同风险水平地震作用下的反应。最后以能力设计原理保证桥墩截面的抗剪强度需求。通过一个具体设计算例说明了建议方法的可行性。     

Seismic assessment of concrete buildings reinforced with shape memory alloy materials in different stories

Shape memory alloy (SMA) is a unique material with many beneficial characteristics such as superelasticity and excellent resistance against corrosion. However, the high expenses related to the material costs and difficulties associated with implementation of SMAs in reinforced concrete (RC) structures may limit their usage. To decrease the costs related to SMA installation, this paper investigates the seismic performance of RC moment‐resisting frames with the intention of specifying the optimal stories for SMA utilization. To this end, RC frames with 3, 5, 7, and 9 stories are modeled and various cases are considered for SMA locations in different story levels. For each building, 4 different cases are considered including a frame with regular steel reinforcement (Steel), a frame with SMAs in all story levels (full SMA), and 2 remaining cases consist of frames with SMAs in bottom and middle story levels only. In the first part, nonlinear dynamic time history analyses are conducted to evaluate the base shear, roof displacement, interstory, and residual drift demands of the structures using 10 ground‐motion records. In the second part, the incremental dynamic analysis is employed to assess the entire range of structural dynamic behavior. By using the generated data from incremental dynamic analysis procedure, fragility evaluation is conducted on multiple limit states to provide a comprehensive performance assessment for each case. The results indicate that frames with SMA in their lower story levels performed similar to frames equipped with SMA in all story levels. However, the fragility assessments show the better performance of frames with SMA in their bottom stories versus other cases. On this basis, the costs associated with SMA fabrication could be reduced noticeably (nearly two‐thirds) without sacrificing the overall performance of the frame and its post‐earthquake serviceability.     

螺纹钢法兰连接预制装配桥墩抗震性能研究

为研究在水平荷载作用下螺纹钢法兰连接预制装配桥墩的抗震性能,设计制作一个整体现浇桥墩、两个分别采用承插式和非承插式方案的螺纹钢法兰连接预制桥墩.通过开展拟静力加载试验,对比研究螺纹钢法兰连接预制装配桥墩与整体现浇桥墩的破坏模式、荷载-位移曲线特征.基于试验,建立三个桥墩的有限元数值模型与试验进行对比,两者结果吻合较好....     

Incremental dynamic analysis of steel frames equipped with NiTi shape memory alloy braces

This paper determines the seismic performance of four‐storey concentrically braced frames equipped with either steel buckling‐restrained braces or buckling‐restrained superelastic shape memory alloy (SMA) braces through incremental dynamic analysis. The incremental dynamic analysis technique is used to examine the behaviour of four‐storey braced frames with four different bracing configurations (including diagonal, split‐X, chevron‐V and inverted‐V) under 20 different ground motion records. The study reveals a satisfactory performance at the design intensity level for both types of braced frames. The results show that the SMA braces lead to a uniform distribution of inelastic response over the height of the buildings, as well as mitigating seismic response in terms of maximum inter‐storey drift and residual roof displacement. By comparing the responses of SMA and buckling‐restrained braced frames under higher intensities of earthquake loading, it is found that the SMA braces can be more beneficial especially under severe ground motion excitations. Copyright © 2014 John Wiley & Sons, Ltd.     

Implementation of shape memory alloy dampers for passive control of structures subjected to seismic excitations

Different crystallographic phases of shape memory alloy (SMA) materials were used in a damper in order to produce an effective behavior device capable of dissipating energy, while containing the recentering capability. Different methodologies were applied in the four proposed damper systems in order to optimize their implementation into the earthquake resistant structural systems. To compare the structural system performance by using the different devices, the idea of damage indicator was utilized with certain modifications. The structural damage, non-structural damage, and the damage to the contents of different systems with the permanent deformations of the systems were considered at different ground acceleration histories. The comparisons were made with the buckling restrained steel bracing system. The effectiveness of the implementation of SMA dampers in reduction of the residual deformations on the structure is presented even after very high ground motions.     

窗间墙锚固配筋砖混结构教学楼抗震性能试验研究

为改善砖混结构教学楼的抗震性能,通过对其纵向窗间墙局部配筋并在墙体两端采用竖向钢筋进行锚固配筋,按照1/2的缩尺比例设计了2个砖混子结构模型。采用拟静力试验分别对普通窗间墙和配筋窗间墙的子结构模型的破坏模式、承载能力、变形能力、刚度退化、延性、耗能性能以及窗间墙的破坏模式和纵墙的破坏机制等进行了分析。结果表明：普通窗间墙模型表现为层间破坏机制,窗间墙发生剪切破坏,纵墙发生“强梁弱柱”式破坏;窗间墙局部配筋并进行锚固的模型发生整体型破坏,窗间墙弯曲破坏,纵墙的破坏机制具有“强柱弱梁”特征,层间变形均匀,模型的破坏形态、耗能能力和延性等均得到改善。     

OpenSEES在混凝土桥墩滞回性能分析中的应用

利用有限元软件OpenSEES对粘钢加固钢筋混凝土墩柱进行了多维滞回荷载作用下的非线性分析,并将计算结果与模型试验进行了对比分析。结果显示计算所得的荷载-位移滞回曲线、骨架曲线与试验得到的曲线基本吻合,这表明OpenEES所建立的非线性有限元模型能够较好地模拟粘钢加固钢筋混凝土墩柱的受力性能。     

钢筋混凝土桥墩弹塑性地震反应分析

以连续梁桥为例,采用非线性有限元方法,基于梁理论的纤维单元模型,计算在地震激励下钢筋混凝土桥墩的响应,结果表明：大震激励下,桥墩产生了塑性变形。     

Prediction of time‐dependent local scour around bridge piers

Most formulas for predicting the scour depth around bridge piers result in over‐predictions. This is partly due to ignoring the fact that the local scour is a time‐dependent process. Formulas that take into account time‐dependent local scour around bridge piers have been developed in the past. However, these formulas predict the scour process well, but only when applied to datasets from which they were constructed. Motivated by this, the present study proposes a relationship for time‐dependent local scour using dimensional analysis and nonlinear regression. Similarly, another relationship for the time to equilibrium is also developed. The findings indicate that the proposed relationship predicts time‐dependent local scour better than existing formulas. The proposed relationships are applicable to local scour around cylindrical bridge piers. It is assumed that the bed sediment is uniform and the bedform effect is minor and can be ignored.     

连续梁桥悬臂拆除主墩受力分析与监测

以某连续梁桥悬臂拆除工程为背景,对主墩进行了拆除过程有限元仿真计算分析,并在主墩关键位置布置应变计进行施工监测,以确保拆除过程桥墩的结构安全,使拆除工作的全过程处于受控状态。     

Seismic response of steel braced frames with shape memory alloy braces

In this paper, the seismic performance of steel frames equipped with superelastic SMA braces was investigated. To do so, buildings with various stories and different bracing configurations including diagonal, split X, chevron (V and inverted V) bracings were considered. Nonlinear time history analyses of steel braced frames equipped with SMA subjected to three ground motion records have been performed using OpenSees software. To evaluate the possibility of adopting this innovative bracing system and its efficiency, the dynamic responses of frames with SMA braces were compared to the ones with buckling restrained braces. After comparing the results, one can conclude that using an SMA element is an effective way to improve the dynamic response of structures subjected to earthquake excitations. Implementing the SMA braces can lead to a reduction in residual roof displacement and peak inter-story drift compare to the buckling restrained braced frames.     

不同极限位移BRB的RC框架结构#br# 抗地震倒塌性能研究

设计6个装有不同极限位移BRB的RC框架结构,基于OpenSees建立相应的有限元模型并验证模型的可行性和BRB模拟准确性,对装有不同极限位移BRB的RC框架结构模型进行增量动力分析和地震易损性分析,研究不同极限位移BRB的RC框架结构抗地震倒塌性能。研究表明：随着BRB极限位移的增加,结构抗倒塌性能得到提升;当系数小于1.2倍时,罕遇地震下结构中出现BRB失效概率大于5%,当系数大于1.2倍时,BRB极限位移提高对结构抗倒塌性能提高有所下降;《建筑消能减震技术规程》（JGJ 297—2013）对消能减震装置极限变形取12倍安全系数是合理的。     

Seismic performance of precast hollow bridge piers with different construction details

Currently the design scheme of precast hollow concrete bridge piers will be adopted in bridge design in China, but there is no code including specific design details of precast segmental piers in high seismic risk area. For comparative study of seismic performance of the hollow bridge piers which had different design details, six specimens of hollow section bridge pier were designed and tested. The specimens consist of the monolithic cast-in-place concrete bridge pier, precast segmental prestressed pier with cast-in-place joint and precast segmental concrete bridge pier with dry joints. Results show that all specimens have good displacement capacity. The bridge pier with bonded prestressed strands exhibits better energy dissipation capacity and higher strength. The un-bonded prestressed strand bridge pier displays less residual plastic displacement and energy dissipation capacity. The bridge pier with both bonded prestressed strands at the edge of the section and un-bonded in the center of the section not only exhibits more ductility capacity and less residual plastic displacement, but also shows better energy dissipation capacity. Compared with experimental results of prestressed bridge columns, analytical result demonstrates the developed numerical analysis model would provide the reasonable and accurate results.     

Application of shape memory alloy bars in self-centring precast segmental columns as seismic resistance

The objective of this study is to investigate analytically the performance of self-centring precast segmental bridge columns with shape memory alloy (SMA) starter bars under nonlinear static and lateral seismic loading. For this purpose, a 3D finite element model for hybrid post-tensioned bridge column has been developed. The precast post-tensioned segmental bridge columns possessing a central tendon and adequate transverse confinement provided by the steel tube jacketing as self-centring bridge columns have an undesirable high lateral seismic demand due to their low energy dissipation. In order to eliminate this deficiency while keeping the residual displacement small, SMA starter bars are applied in this system. The effect of post-tensioning (PT) forces of the central strands and SMA bar size are investigated. The results indicate that in high seismicity zones, bridge columns with SMA bars at a higher level of PT forces have a superior performance against earthquake loading.     

高强轻质混凝土对桥梁抗震性能的影响分析

就高强轻质混凝土桥梁结构对地震响应的影响进行了比较分析,分析结果表明:高强轻质混凝土能有效地减小桥梁高阶自振周期,减小桥梁结构的地震内力响应和位移响应,同时,对于同一强度的高强轻质混凝土,其密度和弹性模量的改变对于桥梁结构的地震响应影响不大。     

铁路双线桥墩混凝土裂缝控制

阐述了铁路双线桥墩混凝土裂缝的分类及控制原则，从混凝土施工中的材料选用、配合比设计、外加剂等方面，分析了混凝土裂缝产生的影响因素，并对混凝土的浇筑养护作了探讨，以合理控制铁路双线桥墩混凝土裂缝的产生。     

桥梁时程分析所用加速度地震波的模拟研究

研究和分析了输入地震波的确定原则和有关计算，调整方法，介绍了目前某些方法存在的问题，指出为了达到桥梁结构的抗震设防目标，除了合理确定计算模型和结构分析方法外，还需选择合理的地面地震动输入。     

Parametric study on damage control design of SMA dampers in frame-typed steel piers

This paper focuses on damage control design of SMA dampers in steel frame piers. A parametric study based on time history analyses is carried out on frame-typed bridge piers with axial-type SMA damping device. The parameters examined are design parameters of strength ratio α_F and stiffness ratio α_K. Seismic performance indexes on displacement and strain are investigated under three JRA recommended Level 2 Ground Type П strong earthquake motions. Design recommendations are suggested following the results of the parametric study.     

高墩大跨连续刚构桥施工过程抗风舒适性分析

针对高墩大跨连续刚构桥悬臂浇筑过程中稳定性差的问题,研究了西北沟谷地形风场基本风速推算方法,采用动力荷载模拟结构在风作用下结构动力响应,并基于Diekemann的舒适度评价方法分析了施工人员的舒适性,提出了此类桥悬臂施工的适宜风速范围。     

Numerical study of geosynthetic reinforced soil bridge abutment performance under static and seismic loading considering effects of bridge deck

Although the use of Geosynthetic Reinforced Soil (GRS) bridge abutments has been increasing, the seismic performance of such structures has remained a significant concern due to their unknown behavior in load-bearing and stress distribution under bridge load and seismic conditions simultaneously. This paper investigates the static and dynamic response of GRS bridge abutment. A series of numerical models representing the realistic field conditions of these structures, including two reinforced soil walls and a single span deck that restrains the top of walls, rather than equivalent surcharge load, was developed. The calibrated numerical model in FLAC program was used to evaluate the effects of horizontal restraint from the deck on the GRS wall displacements and reinforcement loads at the end of construction and under harmonic base acceleration up to 0.5 g. Results indicated that the restraint mobilized from the bridge deck presence, considerably affected the results at both the end of construction and after the dynamic load was applied. Moreover, a series of the parametric studies were performed to investigate the influences of backfill soil relative compaction, reinforcement stiffness, reinforcement length, and reinforcement vertical spacing on the response of GRS abutments at the end of construction and post dynamic state.