通过OpenSees对增大截面加固法、外包FRP加固法及外包ECC加固法3种常见的桥墩加固方案进行数值模拟和对比分析，基于美国太平洋地震工程研究中心的试验数据验证数值模拟的准确性。结果表明：增大截面法可显著增强桥墩的刚度、峰值荷载和耗能，加固60 cm高时，初始刚度、水平峰值荷载分别为22.8 kN/mm和131.9 kN,相比于普通RC柱的11.5 kN/mm和65.9 kN,分别提高了98.3%和100.2%,耗能是加固前的4.2倍。外包FRP类似“加强箍”作用于桥墩外围，能显著提升桥墩的延性性能，加固60 cm时，极限位移为56.2 mm,比加固前的32 mm提高了75.6%,累积耗能为108.1 kJ,是普通RC柱的3.8倍。外包ECC法采用高韧性的ECC材料取代普通混凝土保护层，在地震中通过ECC的均匀稳态开裂增强结构变形及耗能能力，加固60 cm后的极限位移达到49.1 mm,累积耗能为74.2 kJ,比原结构分别提高了53.7%和157.6%。

To study the strengthening effect of carbon fiber composite materials (CFRP) on recycled concrete columns subjected to different levels of seismic damage, four column specimens were designed for pseudo-static tests. The four specimens were categorized as non-destructive without strengthening (prototype), non-destructive strengthening, medium seismic damage strengthening, and severe seismic damage strengthening based on the replacement rate of recycled aggregates and the level of seismic damage. The characteristics of the deformation damage and seismic performance indicators of each specimen were compared and analyzed. The results were verified on the OpenSees platform. A decrease was observed in the initial stiffness of the seismically damaged recycled concrete column specimens strengthened with CFRP, while the ductility, peak bearing capacity, and energy dissipation capacity of the specimens were improved. In addition, with the reduction in seismic damage, the ductility and energy dissipation capacity of the strengthened seismically damaged recycled concrete column specimens were enhanced to different degrees. In particular, the cumulative energy dissipation of the strengthened specimens exposed to medium seismic damage increased most significantly, by 32.5%. In general, the hysteretic curves of the strengthened specimens were full, and the average ductility coefficients were 4.1–6.8. CFRP strengthening was more effective for restoring and enhancing the performance of the recycled concrete column specimens with medium and lower seismic damage levels (displacement ratio ≤ 3%). © 2023 by the authors.

Water pollution exacerbates water stress and poses a great threat to the ecosystem and human health. Construction and demolition waste (CDW) due to rapid urbanization also causes heavy environmental burdens. A major proportion of CDW can be effectively converted into recycled aggregates, which can be reused in many fields, including environment remediation. In this study, a nano ecological recycled concrete (nano-ERC) was produced with recycled aggregates and copper oxide nanoparticles (nCuO) to remove heavy metals (HMs) from a simulated wastewater effluent (SWE) for further treatment. Recycled aggregates were obtained from CDW, thereby simultaneously reducing the treatment cost of the SWE and the environmental burden of solid waste. The adsorption capacity of nano-ERC was presumed to be significantly enhanced by the addition of nCuO due to the unique large surface-to-volume ratio and other properties of nanoparticles. The SWE containing five common HMs, arsenic (As), chromium (Cr), cadmium (Cd), manganese (Mn) and lead (Pb), was filtered through a control ERC and nano-ERCs, and the concentrations of these HMs were determined with ICP-MS in the SWE and the filtrates. Results showed the nano-ERCs could significantly remove these HMs from the SWE compared to the control ERC, due to the enhanced adsorption capacity by nCuO. The relative weighted average removal percentage (RWAR%) was in the range of 53.05-71.83% for nano-ERCs and 39.27-61.65% for control ERC. Except for Cr, concentrations of these HMs in the treated wastewater effluent met the requirements for crop irrigation or scenic water supplementation; the Cr may be removed by multiple filtrations. In conclusion, nano-ERC can serve as a cost-effective approach for the further treatment of wastewater effluent and may be applied more widely in wastewater treatment to help relieve water stress.

Piers and bearings influence each other in earthquakes, and the failure of any component will affect the whole function of bridges. Thus, it is critical to consider the correlations between multiple components in the seismic vulnerability analysis of the overall bridge system. In this paper, a method of overall seismic vulnerability analysis with nested copula model was proposed to model the correlations between multiple components. The components were combined according to their types to construct the hierarchical structure of the system. The correlation of components was modeled with copula functions, and the nested copula model of the system was eventually developed. Maximum likelihood estimation and goodness-of-fit test were used to select and optimize the copula functions. The overall seismic vulnerability of the multispan bridge system was established using the nested copula model. A four-span continuous rigid frame bridge was used to illustrate the application of the proposed method. The results show that the nested copula model accurately simulated the correlations between multiple components, which would eliminate the overestimation or underestimation by the first-order boundary method.

A moment-independent importance measure analysis approach was introduced to quantify the effects of structural uncertainty parameters on probabilistic seismic demands of simply supported girder bridges. Based on the probability distributions of main uncertainty parameters in bridges, conditional and unconditional bridge samples were constructed with Monte-Carlo sampling and analyzed in the OpenSees platform with a series of real seismic ground motion records. Conditional and unconditional probability density functions were developed using kernel density estimation with the results of nonlinear time history analysis of the bridge samples. Moment-independent importance measures of these uncertainty parameters were derived by numerical integrations with the conditional and unconditional probability density functions, and the uncertainty parameters were ranked in descending order of their importance. Different from Tornado diagram approach, the impacts of uncertainty parameters on the whole probability distributions of bridge seismic demands and the interactions of uncertainty parameters were considered simultaneously in the importance measure analysis approach. Results show that the interaction of uncertainty parameters had significant impacts on the seismic demand of components, and in some cases, it changed the most significant parameters for piers, bearings and abutments.

大跨度斜拉桥作为高次超静定结构,通常包含主塔、斜拉索、主梁、辅助墩及连接墩等较多构件,由于地震作用下各构件相互影响,准确模拟构件地震响应之间的相关性对斜拉桥整体系统的易损性评估十分关键。因Pair Copula能较好地模拟构件两两之间的相关性,理论上可将Pair Copula分层迭代模拟斜拉桥整体系统,进而提出基于Pair Copula迭代模型的斜拉桥系统地震易损性评估方法。基于结构不确定性参数及地震动不确定性,采用拉丁超立方抽样技术建立桥梁-地震动概率地震响应分析样本;通过非线性动力时程及相关性分析,量化构件地震响应之间的相关性;采用极大似然估计拟合Pair Copula模型,基于AIC及BIC准则对其进行优选;通过Pair Copula分层迭代,建立斜拉桥整体模型并对其进行地震易损性评估。工程实例表明,基于Pair Copula分层迭代技术能准确模拟多构件之间的相关性,假定构件地震响应完全不相关,会显著高估斜拉桥整体系统的地震易损性。

为研究套箍加固钢筋混凝土中长柱的破坏特征、加固效果和受力性能,开展了2根普通钢筋混凝土中长柱（轴压、偏压各1根）和6根采用套箍加固的钢筋混凝土中长柱（轴压、偏压各3根）的静力破坏试验研究。结果表明:试件主要表现为材料破坏,破坏发生位置偏向加载端,偏压柱加固后破坏形态会发生改变;相对于未加固柱,加固后柱的承载力可以实现成倍增长;在加固后的受力过程中,轴压构件的核心柱和套箍层应变变化同步,偏压构件的核心柱相对于套箍层存在应变滞后;加固柱的最终横向挠曲变形基本符合半波正弦曲线;加固柱的纵向应变符合平截面假定。对试验试件的承载力计算,《公路桥梁加固设计规范》（JTG/T J22—2008）和《混凝土结构加固设计规范》（GB 50367—2013）的结果表现存在差异,具体为后者结果总体表现优于前者,前者相对于后者结果偏大。

为研究套箍加固RC轴压中长柱的承载力理论计算分析方法,采用切线模量理论,根据材料本构关系和内外力平衡条件,推导了套箍加固RC轴压中长柱的弹塑性稳定承载力计算方法。将理论计算结果与试验结果进行了对比分析,结果表明:理论计算值均低于实测值,且二者的偏差在15%以内。根据所推导的计算分析方法,研究了核心柱初始荷载水平β、柱子长细比l0/b、套箍层混凝土强度、套箍层配筋量四种参数对加固柱承载力Nu的影响规律,结果表明:Nu总体上随β增大而减小,当β＜0.7时,减小趋势不够明显,β＞0.7后,减小趋势变得明显;l0/b对Nu有明显影响,Nu随l0/b的增大而减小,但二者不是线性关系;Nu随套箍层混凝土强度提高而增大,随套箍层配筋量增大而增大。

为探究高承台下自由桩长对双薄壁墩连续刚构桥地震响应的影响,基于OpenSees程序建立了实桥有限元模型并进行弹塑性时程分析,通过对比不同自由桩长模型的时程曲线、峰值响应及滞回特性,分析了自由桩长对桥梁地震响应的影响。结果表明:自