The paper delves into the fragility analysis of a long-span continuous rigid frame bridge with high piers under multiple hazards. Taking a bridge of this kind prevalent in a mountainous region as a case study, we in this paper built a finite element model with the Open System for Earthquake Engineering Simulation (OpenSees) software and conducted nonlinear time-history analysis under wind and seismic loads. This was followed by assessing the bridge fragility in the conventional method of single-factor control variable (SFCV) fitting. Meanwhile, we, based on seismic fragility analysis, proposed an approach to fragility assessment under multiple hazards before drawing a comparison between the two. The results showed that in analyzing the demand-capacity ratio (DCR) and disaster intensity regression, we found log-linear regression to be more reasonable. The DCR-based log-linear regression analysis can reliably predict the probability of structural damage under wind and seismic loads, thus reducing calculations and avoiding inaccurate predictions arising from a traditionally inadequate wind speed classification. The proposed analysis can predict and assess the risks of bridges of this type in regions prone to multi-hazard events.

Due to the influence of design parameter errors, construction inaccuracies, and time-dependent material degradation, such as shrinkage and creep, it is challenging to directly predict the bearing capacity of existing concrete girder bridge structures using numerical simulations. To address this issue, a finite element model (FEM) updating method based on a proxy model (PM) is proposed and applied to a real-life plate girder bridge, aiming to enhance the accuracy of bearing capacity evaluation compared to traditional estimation methods. Firstly, considering the critical mechanical parameters that significantly influence structural performance, such as deflection and fundamental frequency, a bridge structure in service was simulated using the FEM and subjected to random static vehicle loads. This generated a large dataset of deflection and fundamental frequency samples. Based on these samples, a high-precision proxy model (PM) was constructed using a deep neural network. Additionally, through sensitivity analysis, key mechanical parameters of the bridge structure-such as boundary restraint stiffness, compressive strength of concrete, and elastic modulus of reinforcement-were determined. The finite element model was then updated using these parameters. The reliability and accuracy of the proposed method were validated against in-situ measured data. The difference between the measured deflection and the predicted deflection of the updated model was only 0.4 %. Among three proxy models, the deep learning network (DLN) showed the best prediction performance with sufficient samples, while XGBoost proved more effective in cases with missing samples. Furthermore, the updated FEM was used to predict the bearing capacity of the original bridge. The results demonstrated that the proposed proxy model (PM) method provided high accuracy in assessing the bearing capacity, offering a reliable approach for the safety evaluation of existing bridge structures and the residual bearing capacity assessment of damaged bridges, even with limited measured data.

实现地震后桥梁使用功能的快速恢复即基于韧性的桥梁抗震设计方法是当前研究的热点方向.首先,总结基于韧性的抗震设计理论,从摇摆体系、自复位体系、可更换构件体系3个方面展开详细探讨,介绍易损性分析曲线研究的发展阶段.然后,回顾国内外摇摆桥墩可恢复性设计理论与试验研究现状,分析摇摆桥墩在震后恢复上的优势及不同摇摆桥墩体系的特点.最后,归纳现有的计算分析方法,讨论当前基于韧性的桥梁抗震设计研究中的不足和发展趋势.研究结果表明:基于韧性的抗震设计理念及摇摆桥墩在桥梁震后恢复上的优势已得到普遍认可,但仍存在一些问题需进一步研究;基于韧性抗震设计亟待实现韧性指标量化及多道设防指标的梯度控制;摇摆桥墩的关键构造问题有待解决,应注重新材料、新构造形式的开发;现有分析模型忽略了增加耗能装置后的体系阻尼的变化,需进一步研究桥梁抗震性能与韧性耗能复位装置的交互作用.

To comprehensively consider and study the seismic performance of the self-center mortise-tenon segmental pier, its vulnerability under earthquake is evaluated. The reliability of the model is verified by comparing the cyclic pseudo-static test results with the finite element models. The model is used as the basis for vulnerability analysis. Taking the maximum displacement of the pier top as a damage index. Different damage states are described. The damage index limits μcy1, μcy, μc2, and μcmax of different damage levels are determined. The time history analysis of cast-in-place pier and mortise-tenon segmental piers under different earthquake actions is carried out by using finite element software. The probabilistic seismic demand model is established through IDA curves. And the seismic vulnerability analysis is carried out. The influence of various parameters on the seismic vulnerability of mortise-tenon segmental pier is studied by changing the longitudinal reinforcement ratio, axial compression ratio, and aspect ratio. The results show that the seismic vulnerability of the two types of piers designed according to the principle of equivalence is similar under different damage states. It can be considered that it has better seismic performance. The longitudinal reinforcement ratio, axial compression ratio, and aspect ratio have a great impact on the vulnerability of piers.

In this paper, the fatigue performance of six steel-concrete composite beam specimens was tested following subjection to chloride-induced corrosion and cyclic freeze-thaw conditions. The specimens included cast-in-place concrete slab composite beams with uniformly distributed studs and precast concrete slab composite beams with a cluster distribution of studs. According to the climatic characteristics of large temperature differences between day and night in alpine and high-altitude areas of Qinghai Province of China, together with the working conditions of bridges under deicing salt after snow, corrosion tests and freeze-thaw tests of composite beam specimens were performed prior to fatigue testing. The test results show that the freeze-thaw cycle causes obvious frost heave damage to the concrete, which affects its strength and stiffness. When the composite beam specimens were subjected to fatigue loads, tearing failure of the steel plates at the welds and interface failure at the studs were observed. Furthermore, with the influence of stress amplitude, fatigue life was found to be related to the initial crack defect within the specimen itself. Reduction in the initial stiffness of composite beams was found to be affected by the freeze-thaw cycle, stud arrangement type (uniformly distributed or cluster distributed), and steel type (ordinary steel or weathering steel). However, the stiffness degradation rate of all specimens against loading times was essentially identical before fatigue failure.

为促进预制拼装桥墩在中、高抗震设防烈度地区的可利用性,基于ABAQUS有限元模型开展了榫卯式节段拼装桥墩试验,进行了数值模拟对比.在纵向耗能钢筋不同截面配筋率、预应力筋不同初始预应力大小和有无黏结及不同布置位置的条件下对榫卯式节段拼装桥墩进行了抗震性能分析,并设计了一种外置可更换耗能软钢棒阻尼器,通过往复水平加载进行了抗震性能分析.结果表明:与未配置耗能钢筋的MTSP-S0 相比,内置耗能钢筋可提高榫卯式节段拼装桥墩的水平承载能力及耗能能力,水平承载能力及耗能能力随着截面配筋率的增大而增大,截面配筋率增大到一定程度时,耗能能力及残余位移的增加有所变缓,存在震后不易修复等不足;预应力筋初始预应力的增大减小了耗能能力,但设置 25%初始预应力大小的MTSP-Y0.25 会由于墩底相对滑移过大而产生破坏,建议初始预应力不低于 30%;预应力筋有无黏结及布置位置对水平承载能力、累积耗能等方面均有影响,对自复位能力影响较小;增设由 4 个软钢棒组成的外置耗能阻尼器MTSP-S0-D可大幅提高榫卯式节段拼装桥墩的水平承载能力、耗能能力,其抗震性能接近于配置 4 根直径为 20 mm的内置耗能钢筋MTSP-S4,且外置耗能软钢棒阻尼器可以通过更换阻尼器的方式实现震后修复.

为了对钢-混凝土组合梁在疲劳荷载作用下的弹性挠度和残余挠度分析,建立了组合梁疲劳荷载下的非连续传力模型.通过建立钢材和栓钉等材料的疲劳损伤退化模型,对组合梁在疲劳荷载情况下沿梁长方向的滑移分布情况和跨中挠度进行了计算.结合不同连接程度的组合梁疲劳试验数据,进行了参数分析,并验证了方法的可靠性.提出了疲劳荷载作用下钢-混凝土组合梁变形计算公式,采用该模型计算的滑移值、弹性挠度值与试验值有较高的吻合度.当考虑沿梁长方向各排栓钉的刚度退化情况时,对于组合梁变形计算有较大的影响.通过混凝土承担的轴力和弯矩可知,疲劳荷载作用下,栓钉承载能力降低造成组合梁截面曲率增大,刚度降低,自身截面刚度的退化影响较小.计算结果表明:在疲劳荷载加载时,组合梁界面栓钉出现剪力重分布现象,跨中栓钉承担的剪力由小变大,靠近梁端栓钉承担的剪力由大变小,且呈非线性变化趋势.当接近组合梁疲劳寿命时,组合梁跨中变形、截面滑移都呈指数型上升趋势.当达到疲劳寿命时,梁端栓钉承担的剪力急剧下降,最终造成以栓钉剪切疲劳破坏形式的组合梁疲劳破坏.该方法可供实际试验和工程实际参考.

In the past decades, more and more precast piers have been used in actual engineering, which brings convenience in construction and standardization of production. However, precast piers still have some shortcomings, such as shear slip between segments and poor energy dissipation. Thus, a self-centering mortise-tenon segmental bridge pier was proposed in this paper. To research the seismic performance of the self-centering mortise-tenon segment piers, three scaled model piers with their scale ratio as 1:3 were designed and prefabricated, namely as a cast-in-place model pier (CP) and 2 self-centering mortise-tenon segment model piers (designated as MTSP1 and MTSP2) with the initial pretension of 1302 MPa and 1488 MPa, respectively. The cyclic pseudo-static tests of the three piers were carried out. The comparison analysis was made respecting to the test results including the damage form, hysteretic characteristics, skeleton curve, energy dissipation capacity, residual displacement and equivalent stiffness of the three specimens. It was shown that MTSP specimens had higher horizontal bearing capacity. While the yield load, ultimate load, displacement ductility coefficient and initial stiffness of MTSP1 and MTSP2 were higher than those of CP. The MTSP had better performance considering the above aspects. The mean value of the residual displacement of MTSP2 was lower than that of CP 21.14 % and 29. 72 % respectively, as the drift ratio reaching 5 %. The MTSP specimens had better self-centering capacity due to the increased pretension stress which reducing the residual displacement greatly. The energy dissipation reinforcements improved the energy dissipation capacity of the segmental assembled piers. Based on the ABAQUS model, the numerical simulation was carried out and compared with the experimental data. MTSP had great energy dissipation capacity and self-centering capacity. It was suggested that MTSP should be used to make up for the deficiency of segmental assembled pier and improve the seismic performance of segmental assembled pier.

针对目前"结构力学"课程教学过程中较多关注于基本理论和计算方法,而忽视了专业及工程应用性的问题,探讨将工程结构的模型简化、力学建模、内力分析、结构优化、移动荷载作用下的结构内力计算等过程环节,通过学生程序编制的方式,融合进矩阵位移法和影响线及其应用等教学环节中;探索更灵活有效的教学案例,实现研究性课程教学的创新和实践,以期达到强化学生的概念理解和提升学生对工程结构的分析能力的目的.

为分析钢-混凝土组合梁在分别承受正弯矩和负弯矩2种荷载下的破坏形式和受力性能,设计制作了2片组合梁试件并进行了相关试验研究.试验表明,2种荷载模式下,组合梁受力均呈现出弹性、弹塑性和破坏3个阶段,且组合梁在负弯矩荷载作用下更易引起开裂.同时,2种荷载模式下的界面滑移分布规律不一致,正弯矩作用下的相对滑移最大值出现在靠近梁端处,而负弯矩作用下的相对滑移最大值出现在跨中处.

Bridge bearing as an essential component in the bridge structure is used in many bridge design and construction [1] The main role of bridge bearings in the bridge structure is to bear the dead weight from the superstructure and live loads caused by other bridges in vertical, longitudinal and transverse directions, and transfer these loads to the substructure. The bridge bearing offsets the displacement and rotation angle of the bridge beam caused by the above-mentioned load through its own deformation and rotation. At present, there is no precise quantitative index for the working performance of bridge bearings. Based on the correlation and sensitivity analysis, this paper proposes that the correlation between the output parameter and the input parameter and the sensitivity order are used as the basis for selecting the basin rubber bearing identification index. Further, the sudden change points of the sensitivity of each operating point are used as indicators. The basis of the division, and according to the established basin rubber bearing identification system, through a large number of operating point calculations, the pot rubber bearing grade is directly determined from the stress and corresponds to the vertical and shear forces of the pot rubber bearing. Combined with SVM, a safety level discriminant model for basin rubber bearings is formed.

In order to comprehensively evaluate the working state and safety performance of the bridge plate rubber bearing (PRB), the basic principle and method of SVM in machine learning theory (Support Vector Machine) was introduced in this paper. Firstly, the performance indices (such as the average compression stress, tangent value of the shear angle and the rotation angle of the PRB) were analyzed and calculated through its finite element model considering the different working conditions (axial compression, shear deformation and the rotation deformation of the PRB). Subsequently, considering the relevant indices affecting the safety performance of the PRB, the Pearson Correlation Coefficients (PCC) were calculated by SVM method for assessing the internal correlation of the performance indices of the PRB for different cases, respectively. The threshold values of the influential factors for different cases considering the PCC and the weight coefficient were obtained for grading the working state of the PRB as five levels. Moreover, in order to verify the validity and suitability of the evaluation of the working state of the plate rubber bearing by the SVM method, three apparent indices for grading the performance level of the PRB such as the crack, the undistributed spalling deformation and the dislocation of the PRB were analyzed and compared with the qualitative descriptions and the quantitative values. Finally, the corresponding threshold values for grading the performance levels of the PRB working states were proposed. It was shown that the SVM based evaluation method for the PRB is feasible and convenient, especially for the bridges with real-time monitoring devices to get the response data of the PRB.

The active noise reduction feature of highway tunnel is analyzed theoretically based on the principle of acoustic interference.The models of three full-sized tunnels are established based on finite element method (FEM).The distributions of sound pressure level are calculated,and the characteristics of sound field in tunnels are analyzed during active noise cancellation.The results show that the lower the noise frequency is,the better the effect of active noise control is when adding the spatial distance between the active noise control device and the noise source to the spatial distance between the active noise control device and the noise reduction position,getting a sum,then comparing the sum and the spatial distance between the noise source and the noise reduction position,there is a conclusion that if the difference value is the integral multiples of noise wavelength,noise reduction of more than 3dB can be achieved nearby the noise reduction area.

针对公路长大隧道内噪声声压级超过90 dB,且目前多采用降噪路面或隧道壁喷涂吸声材料进行被动降噪的现状,基于声波干涉原理尝试对高速公路隧道进行主动降噪.为了确定公路隧道内主动降噪技术的适用条件、实现方法和降噪效果,采用理论推导和有限元仿真相结合的方法,构建了沥青混凝土路面公路隧道内主动降噪声场模型,在隧道尺寸和噪声源位置确定的情况下,模拟分析噪声源频率、主动声源位置等因素对隧道声场降噪效果的影响,并将模拟结果与现场实际隧道主动降噪试验结果进行对比.结果表明:确定了噪声源位置和降噪区域后,根据所提出的噪声源、主动声源和降噪位置的空间关系式,以及主动声源应位于隧道断面中轴线上、运输车辆限高要求等因素,可以确定使需降噪区域实现最佳降噪效果的主动声源摆放位置;噪声频率越低降噪效果越好,主动降噪技术对100 Hz左右的沥青混凝土路面公路隧道噪声降噪效果显著;噪声频率为125Hz时,在隧道断面中轴线上沿纵向每隔3 m布置一台主动声源,可在工人检查走行区域的人耳高度处实现横向宽1 m、纵向长2m的区域降噪,该区域降噪幅度为3～8 dB;研究成果可为高速公路隧道内的主动降噪提供参考.

Based on the selected codes for aseismic design in China and foreign countries,the differences on the classification of the site soil were compared.Considering the factors,such as,return period of earthquake and importance coefficients of structures,the acceleration platforms and the curves of the response spectra with different earthquake levels,such as frequently occurred earthquake (FOE ),designed fortification earthquake (DE )and rarely occurred earthquake(ROE)in the main aseismic design codes of China were compared with those in the Code for Seismic Design of Railway Engineering (GB50111-2006,2009 Version).It was shown that the design earthquake actions at the level of FOE for long-span bridges in high-speed rail are conservatively higher than those in other seismic design codes;the seismic actions at the level of DE are similar to those in the other seismic design codes of China,while at the level of ROE,the seismic actions are relatively lower.Comparison analysis for the seismic actions for long-span bridges in high-speed rail between the code GB50111-2006,2009 Version and the Eurocode 8 showed that the FOE actions in China(50 years return period)are lower than those in the Eurocode 8(90 years return period),and the DE actions (both 475 years of return period)are also lower.Comparing the seismic actions coded in AASHTO and Caltrans with those in the code (GB50111-2006,2009 Version)showed that the FOE actions(50 years of return period)of China are much higher than those of AASHTO and Caltrans,due to the adoption of 1.5 as the importance coefficient of structures;the maximum acceleration values of the response spectra for the DE level of China(475 years of return period)are slightly lower than those of Caltrans(975 years return period),but slightly higher than those of AASHTO(1000 years return period);the curves of response spectra of China are similar to those of Caltrans,but a little higher than those of AASHTO;at the level of ROE(2475 years return period),the seismic actions of AASHTO are between those for the design acceleration 0.1g and those for 0.2g in the China code.In summary,it was shown that the design earthquake actions for long-span bridges in high-speed rail in China are relatively conservative.

Nevada is one of the major states that are currently suffering from graffiti problem. It was estimated that graffiti costs Southern Nevada around $30 million per year. The major highway structures that were suffering from graffiti were bridges, sound walls, retaining walls and traffic signs. Removing graffiti from these infrastructures was a big challenge to the maintenance division of Nevada Department of Transportation (NDOT). Thus, the department was looking for cost effective proactive countermeasures to prevent graffiti on highway infrastructure. This study first identified a spectrum of proactive countermeasures, and then evaluated them by conducting a cost-benefit analysis. Pedestrian fencing and chain link fence were found to be cost effective countermeasures for preventing graffiti on bridges and sound walls. However, for relative long sound walls, the chain link becomes less cost effective. Rat guard was found to be cost effective for road signs; however, it was more useful for traffic signs that are located in the area where the taggers cannot find the way to bypass the rat guard. Coating and landscaping were found to be cost effective for small structures. The security camera countermeasure was not cost effective at the locations where the reduction in graffiti was small. The software for spectrometers was relatively high cost and might hinder the cost effectiveness of this countermeasure. To reduce the cost of the software, developing the software internally could be adopted. And finally, the electronic database was recommended since it was not difficult to develop and maintain.

The uniform loading pattern is specified in the General Code for Design of Highway Bridges and Culverts (JTG D60-2015) and its former version in China.In recent years, bridge safety accident due to the heavy commercial trucks occurred and reported occasionally.Whether the design loads specified in the existing code could satisfy the bridge safety in the heavy load areas is a highlighted question.Through the 24hour traffic investigation at Xinghe segment of G6 Highway insitu, the statistical analysis respecting to the vehicle types, vehicle numbers and the distribution of vehicles spaces are carried out.The commercial trucks weight is investigated at a typical coal storage site close to G6 Highway road.Based on the investigation data, the load patterns of the routine vehicle teams and the congestion vehicle teams are developed and proposed.Choosing the simply supported and continuous girder bridges as the case bridges, the finite element models were established using MIDAS/Civil software.The load effects under the routine vehicle team load and the congestion vehicle team load are analyzed considering 2 lanes and 3 lanes, respectively.The calculating results were compared and analyzed with the results from the coded loads in 2 lanes and 3 lanes.It was shown from the comparing analysis that the congestion vehicle team load is the potential danger for the existing bridge.The bridge design should consider the regional traffic characteristics and its development.

The maximum seismic response of curved bridge is significantly related to the input angle of designated earthquake. Owing to structure irregularities, bridge reactions result from the interaction between the moment and torsion forces. Based on the solving of the seismic response of structure excited by a one-way earthquake input, a uniform expression of the unfavorable angle of the earthquake input was derived, and the corresponding maximum response of structure was determined. Considering the orthotropic and skewed dualdirectional earthquake input manners, the most unfavorable angles for the two cases were also derived, respectively. Furthermore, a series finite element models were built to analyze the multi-component seismic responses by examining an example of curved girder bridge considering the variation of curvature radius and the bearings arrangement. The seismic responses of the case bridges, were excited by earthquakes at different input angles, and were calculated and analyzed using a response spectrum method. The input angles of earthquake excitation were progressively increased. From the analysis and comparison based on the calculation results mentioned above, the most unfavorable angle of earthquake excitation corresponding to the maximum seismic response of the curved bridge could be determined. It was shown that the most unfavorable angles of earthquake input resulted from the different response combination methods were essentially coherent.

本文在建立车辆-道路耦合系统分析模型的基础之上,编制了车路耦合系统的动力仿真程序,研究了不同路面不平顺幅值,不同车辆行驶速度,不同车辆载重以及轴数的变化等参数情况下路面结构不同节点的位移及加速度随参数的变化情况;并探讨了不同路面结构层厚度组合情况下对路面结构的动力响应的影响,研究结果表明路面不平顺幅值对于路面结构的位移与加速度响应影响巨大;车速增加虽不影响路面结构的位移响应,但是增大了路面结构的加速度响应从而增大了对于路面结构的冲击作用;载重的增大会显著增大路面结构的位移与加速度响应;不同路面结构层厚度的组合会显著影响路面结构系统的动力响应,相关的研究还有待于进一步的理论与试验验证.