An experimental study of a damage‐controllable plastic‐hinge‐supported wall structure

The reinforced concrete (RC) shear wall serves as one of the most important components sustaining lateral seismic forces. Although they allow advanced seismic performance to be achieved, RC shear walls are rather difficult to repair once the physical plastic hinge at the bottom part has been formed. To overcome this, a damage‐controllable plastic hinge with a large energy dissipation capacity is developed herein, in which the sectional forces are decoupled and sustained separately by different components. The components sustaining the axial and the shear forces all remain elastic even under a rarely occurred earthquake, while the bending components yield and dissipate seismic energy during a design‐level earthquake. This design makes the behavior of the system more predictable and thus more easily customizable to different performance demands. Moreover, the energy dissipation components can be conveniently replaced to fully restore the occupancy function of a building. To examine the seismic behavior of the newly developed component, 3 one third‐scale specimens were tested quasi‐statically, including 1 RC wall complying with the current design codes of China and 2 installed with the damage‐controllable plastic hinges. Each wall was designed to have the same strength. The experimental results demonstrated that the plastic‐hinge‐supported walls had a better energy dissipation capacity and damage controllability than the RC specimen. Both achieved drift ratios greater than 3% under a steadily increasing lateral force.     

BRB在双柱式桥墩抗震体系中的工作机理分析

以设置防屈曲支撑(Buckling-Restrained Braces,BRB)的双柱式桥墩体系为研究对象,系统分析上部结构惯性力在该体系中的传递机理;以某3×30m公路高架桥为工程背景,采用非线性时程反应分析法研究BRB的设置方式及参数取值对桥梁地震反应的影响规律,揭示BRB在双柱式桥墩中的工作机理。其研究结论为:(1)对于设置BRB的双柱式桥墩,当BRB未屈服时,通过其轴向刚度改变结构体系的传力路径,墩底弯矩、剪力降低,但墩底轴力改变量将增大,即以较大的墩身轴力改变量换取较小的墩底弯矩及剪力。(2)在BRB屈服的情况下,BRB通过改变下部结构的传力路径及滞回耗能双重机制影响结构的地震反应,BRB耗能作用将降低墩身的轴力改变量,使减震效果更优。(3)双柱式桥墩横桥向设置BRB是一种较为有效的减震体系,但其减震效果与BRB具体布置方式及力学参数取值有关。     

Experimental and numerical studies on buckling restrained braces with posttensioned carbon fiber composite cables

There has been an increasing interest in using residual deformation as a seismic performance indicator for earthquake resistant building design. Self-centering braced structural systems are viable candidates for minimizing residual deformations following a major earthquake. Hence, this study proposes an alternative type of buckling restrained brace (BRB) with externally attached posttensioned (PT-BRB) carbon fiber composite cables (CFCCs). The steel core of the brace is used as an energy dissipator, whereas the CFCCs provide the self-centering force for minimizing residual story drifts. Three proof-of-concept specimens are designed, fabricated, and cyclically tested at different posttensioning force levels. The CFCC behavior to obtain cyclic response, including the anchorage system, is examined closely. A parametric study is also conducted to show the effect of the different configurations of PT-BRBs on the inelastic response. Furthermore, optimal brace parameters are discussed to realize design recommendations. The results indicated that the implementation of partially self-centering BRBs in building frames can lead to the target residual displacements. A stable behavior is obtained for the proposed PT-BRBs when subjected to the loading protocol specified in the American Institute of Steel Construction (AISC) 2016 Seismic Provisions.     

Development of a ten-element hybrid simulation platform and an adjustable yielding brace for performance evaluation of multi-story braced frames subjected to earthquakes

This paper presents a ten-element hybrid (experimental-numerical) simulation platform, referred to as UT10, which was developed for running hybrid simulations of braced frames with up to ten large-capacity physical brace specimens. This paper presents the details of the development of different components of UT10 and an adjustable yielding brace (AYB) specimen, which was designed to perform hybrid simulations with UT10. As the first application of UT10, a five-story buckling-restrained braced frame and a special concentrically braced frame (BRBF and SCBF) were designed and tested with AYB specimens and buckling specimens representing the braces. Cyclic tests of the AYB, one- and three-element hybrid simulations of the BRBF, and four-element hybrid simulations of the SCBF inside the UT10 confirmed the functionality of UT10 for running hybrid simulations on multiple specimens. The tests also indicated that AYB was capable of producing a stable hysteretic response with characteristics similar to BRBs. Comparison of the results of the hybrid simulations of the BRBF and SCBF with their fully numerical models showed that the modeling inaccuracies of the yielding braces could potentially affect the global response of the multi-story braced frames further emphasizing the need for experimental calibration or hybrid simulation for achieving more accurate response predictions. UT10 provides a simple and reconfigurable platform that can be used to achieve a realistic understanding of the seismic response of multi-story frames with yielding braces, distinguish their modeling limitations, and improve different modeling techniques available for their seismic response prediction.     

轴向布置金属阻尼器力学性能研究

基于当前金属屈服消能器的应用特点和使用限制,提出一种轴向布置的金属阻尼器,其主要构造特征为耗能钢板直接与连接钢支撑组合,使得支撑与阻尼器组合为单一减震构件,解决了金属阻尼器需要斜撑对称布置的技术问题.推导了轴向布置金属阻尼器的屈服承载力、刚度计算公式;进行了构件的低周往复荷载试验,得到了轴向布置金属阻尼器的滞回曲线和骨...     

深水半潜式平台结构关键节点疲劳破坏机理试验研究

深水半潜式平台结构在深海环境荷载及作业动荷载的作用下容易产生疲劳损伤累积,加速疲劳裂纹扩展,导致结构发生疲劳破坏。对深水半潜式平台横撑部位的两类关键节点进行了疲劳试验研究,分析了关键节点的疲劳破坏现象、疲劳破坏过程以及疲劳裂纹扩展规律。试验结果表明:应用规范给出的裂纹扩展模型和参数估算关键节点的疲劳寿命低于试验所得的疲劳寿命,说明应用规范给出的裂纹扩展模型和参数估算节点的疲劳寿命比较安全;根据疲劳试验结果建立的关键节点的S-N曲线参数与DNV规范给出的较为吻合;关键节点焊趾处的ε-N关系曲线可以反映出关键节点疲劳破坏的三个阶段破坏规律。研究结果为有效地预测平台结构关键节点的疲劳损伤程度,及时进行维修加固延长结构的使用寿命提供参考。     

工程结构粘弹性消能支撑型式及设计参数的研究

针对工程中的实际需要,提出一些新型的粘弹性消能支撑型式,分析了它们的受力特点,推导了消能支撑变形的表达式,并给出了其控制力的计算公式;最后,研究了影响结构消能效果的设计参数,给出了设计参数合理的取值范围。     

变厚度钢板内芯防屈曲支撑试验研究

提出了一种变厚度钢板内芯防屈曲支撑（VTBRB）。设计了2个足尺变厚度钢板内芯防屈曲支撑试件,其中:1个试件在变厚度内芯端部设置加劲肋;另1个试件采用无肋式变厚度内芯。通过拟静力试验分析了2种内芯构造形式对变厚度钢板内芯防屈曲支撑的滞回性能、失效模式、受压承载力调整系数和累计塑性变形等的影响。研究表明:2个变厚度钢板内芯防屈曲支撑均表现较好的抗震耗能特性,其受压承载力调整系数均满足相关规范的限值要求。设置加劲肋可以减少变厚度内芯端部无粘结材料的磨损,并可以有效提高变厚度内芯防屈曲支撑的低周疲劳性能。     

Seismic performance of hybrid ductile‐rocking braced frame system

A new hybrid ductile‐rocking seismic‐resistant design is proposed which consists of a code‐designed buckling‐restrained braced frame (BRBF) that yields along its height and also partially rocks on its foundation. The goal of this system is to cost‐effectively improve the performance of BRBFs, by reducing drift concentrations and residual deformations, while taking advantage of their large ductility and their reliable limit on seismic forces and accelerations along a building's height. A lock‐up device ensures that the full code‐compliant lateral strength can be achieved after a limited amount of column uplift, and supplemental energy dissipation elements are used to reduce the rocking response. This paper outlines the mechanics of the system and then presents analyses on rocking frames with both ductile and elastic braces in order to highlight the large higher mode demands on elastic rocking frames. A parametric study using nonlinear time‐history analysis of BRBF structures designed according to the proposed procedure for Los Angeles, California is then presented. This study investigates the system's seismic response and the effect of different energy dissipation element properties and allowable base rotation values before the lock‐up is engaged. Finally, the effect of vertical mass modeling on analysis results was investigated. These studies demonstrated that the hybrid ductile‐rocking system can in fact improve the global peak and residual deformation response as well as reduce brace damage. This enhanced performance could eliminate the need for expensive repairs or demolition that are otherwise to be expected for conventional ductile fixed base buildings that sustain severe damage.     

SMA-VED混合自复位支撑钢框架地震易损性与风险分析

本文提出了一种新型形状记忆合金（Shape Memory Alloy,SMA）-黏弹性阻尼器（ViscoelasticDamper,VED）自复位支撑,设计了普通预应力筋自复位支撑钢框架与SMA-VED自复位支撑钢框架。采用组合模型以及改进材料模型准确模拟了支撑的力学行为,详细讨论了考虑构件失效的模拟方法,通过试验确定了VED的失效应变范围,最后基于概率统计方法进行了易损性分析以及全周期风险分析。研究发现: SMA-VED自复位支撑可显著提升框架抗震性能;倒塌风险以及残余变形超越概率均显著低于普通预应力筋自复位支撑钢框架,下降比例最高超过50%。预应力筋断裂失效导致框架倒塌风险可提高5倍以上; SMA-VED自复位支撑失效会造成残余变形超越概率有所上升但幅度不大。总体来说,SMA-VED自复位支撑钢框架具备更好的地震鲁棒性。