This study introduced a new type of welded joint called the non-planar oblique butt-welded joint. This joint conceptualized from cable-stayed bridge anchor plate involves mother plates with both out-of-plane and in-plane angles, leading to a complex stress concentration phenomenon. A dataset of equivalent structural stress concentration factors (ESCF) which was effective in evaluating complex welded structures fatigue was extracted from the test-validated finite element models. Five machine learning models were trained. The best-performing Support Vector Regression (SVR) was selected to build an ESCF prediction model based on the parameters (out-of-plane angle, in-plane angles, length-to-thickness ratio, and stress amplitude ratio), and then subjected to a SHapley Additive exPlanations (SHAP) analysis. Results showed that the ESCF on the concave side increased with the out-of-plane angle and decreased on the convex side, similar to the influence of the length-to-thickness ratio and the stress amplitude ratio. The increase of the in-plane angles led to the redistribution of ESCF value due to the change in structural stiffness. As a result of the analysis, an anti-fatigue design framework was developed. This framework assists designers in optimizing the parameters and predicting fatigue behavior of non-planar oblique butt-welded joints.

The stress analysis of the cable-pylon anchorage zone is usually calculated using solid finite elements.However,due to the complex structure and diverse types,it is not easy for general engineering designers to use.Therefore,this paper analyzed the transmission characteristics of the built-in steel anchor box anchoring system based on the actual project of a cable-stayed bridge and proposed a simplified calculation method based on the plane frame theory.Nonlinear analysis methods were used to establish an ANSYS finite element model of the anchorage zone to correct the formula.The results show that the error between the calculation results of the simplified formula before correction and the finite element model calculation results is about 10%.Considering the influence of the thickness of the pylon wall,the calculation height of the pylon,and the thickness of the anchor box side plate,the method of reducing the elastic modulus of concrete is used to compensate and correct the stress distribution of the bridge pylon,and the specific concrete reduction coefficient is determined by the method of nonlinear regression.Finally,the corrected formula was compared with the finite element model data.The results show that the error between the calculation results of the corrected formula and the finite element model calculation results is within 2%,indicating the corrected formula can well analyze the cable force distribution in the cable-pylon anchorage zone and has a certain practical engineering value.

In this study, an extensive parametric investigation for the stress concentration factor (SCF) of concrete-filled steel tubular (CFST) T-joints was conducted based on a validated finite element (FE) model in which the weld profile, mesh, and contact simulation were specifically and precisely dealt with. Distribution of the SCF on the intersecting line was depicted. Effect of non-dimensional geometric parameters and the elastic modulus of concrete was discussed in detail. Results show that the SCF is monotonically distributed on the intersecting line in the chord side, and the maximum SCF probably located at the crown position. There is the possibility that the maximum SCF of the brace occurs at a position neither the crown nor the saddle. Reducing the length of chord or promoting the elastic modulus of concrete lowers the SCF at most positions, but has no effect on the SCF at chord saddle. A back-propagation neural network (BPNN) model was established, and was trained based on 724 FE results of the SCF from the parametric study. The trained BPNN model predicts the SCF of CFST T-joints with a low error of 14.5%, and it improves the accuracy by 62.0% compared to the current formulae.

To study the mechanical characteristics and live load effect of the ultra-wide steel box girder of the cable-stayed rail-cum-road bridge, based on the study of the ultra-wide steel box girder section of Yibin Lingang Yangtze River Bridge with a width of 63.9 m, a model of the composite structure with a scale of 1∶10 was designed and constructed for static load model tests and finite element analysis, where the mechanical characteristics, longitudinal and transverse normal stress distribution and beam deformation characteristics of the ultra-wide steel box girder were investigated under the dead load condition, road vehicle load condition, railway train load condition and combination of different live load conditions. The results show that the box girder of the bridge has a significant lateral bending force behavior, with the girder body exhibiting the mechanical properties and deformation characteristics of a shoulder-supported girder under the live load conditions. The middle box shows the mechanical characteristics of a simply supported beam with positive bending moment under the load of the railway train, while the side boxes of the beam show the mechanical characteristics of the cantilever beam with a negative bending moment under the load of the road vehicles, pedestrians and non-motor vehicles, showing reasonable design of the cross-section of the girder body, clear live load action mechanism, and clear force transmission of the middle and side box structures. The research results provide important reference and design basis for the design and construction of ultra-wide steel box girders, and provide guidance for the design of similar bridges.

To extend the calculation method of hot spot stress concentration factors (SCFs) of circular hollow section (CHS) joints in concrete-filled steel tubular (CFST) joints, a calculation method of SCFs of CFST T/Y joints based on the modified equivalent thickness is proposed. Considering the contact relationship between the concrete and tubular wall and the axial force acting on the CFST chord, 36 finite element models of the CFST T/Y joint were established with different geometric parameters, and the stress distribution of the CFST chords and the CHS braces were investigated. According to the SCFs formula of grouted chord joints given by DNV, the modified equivalent thickness of CFST T/Y joints is derived based on the parametric FEA results. The modified calculation method of SCFs of CFST T/Y joints was established based on the modified equivalent thickness and CIDECT formulas. the proposed SCFs formulas for the CFST T/Y joints were verified by FEA and the experiment results with a calculation error of 20%.

运用有限元软件ANSYS建立钢管混凝土桁架焊接T型管节点模型,进行支管轴向拉力作用下管节点热点应力集中系数(Stress Concentration Factor,SCF)研究.结果表明:T型管节点的主管冠点处SCF与管径比、径厚比和壁厚比均成正相关,而主管鞍点处SCF虽与径厚比和壁厚比成正相关,但与管径比呈负相关;相比于主管,支管SCF整体水平较低,且随几何参数变化幅度较小;主管SCF沿管节点相贯线的分布模式与管径比、径厚比相关,但受壁厚比的影响很小;管节点SCF最大值与径厚比、壁厚比成正相关,随管径比的变化规律与径厚比的取值有关;基于有限元计算结果,可推导出钢管混凝土桁架焊接T型管节点SCF最大值计算式.

为研究悬挂式轨道梁在无车情况下的抗震能力,以某悬挂式轨道交通试验线为研究对象,利用MIDAS/CIVIL建立模型并采用反应谱法,研究不同地震峰值加速度(0.1g、0.15g、0.2 g、0.3 g、0.4 g)对Y型墩柱的影响.研究结果表明:该桥横向刚度较小;相较于横向地震,Y型墩柱在顺桥向地震作用下的内力响应更大;当地震加速度大于0.1g时,4号混凝土墩柱开始出现裂缝;当地震加速度大于或者等于0.25 g时,3号混凝土墩柱开始出现裂缝;在所讨论的地震峰值加速度中,Y型钢墩和混凝土墩柱均未出现屈服现象,但混凝土墩柱弯矩增长速率更快,有先屈服的趋势.

Stress concentration factors (SCFs) are used to quantify the hot-spots stress in tubular joints with circular hollow section for fatigue assessment, which are always obtained by finite element analysis or specimens testing. According to design specifications, complex formulas are recommended to calculate the SCFs at special locations of the intersection lines weld toe of tubular joints for individual load cases. To improve the fatigue performance of the joint, the concrete is filled in the chord to form a concrete-filled steel tube (CFST) joint. The capability of back-propagation neural network-based (BPNN) model in calculation of the SCFs in CFST Y-joints was investigated in this study. Three hundred FE numerical models were investigated to evaluate the effects of changes in different geometrical parameters on the SCFs of CFST Y-joint and the FEA results were used to train and test the neural networks. The nonlinear mapping relationships between the affecting variables and the SCFs distributions were established. Research results showed that SCFs prediction results of CFST Y-joints from BPNN models are close to the FE results, and properly trained and well calibrated BPNN can be reliable alternatives to complicated SCFs equations for predicting SCFs distribution at intersection line of CFST Y-joints.

栓钉连接件是钢-混组合结构中的重要部件，栓钉在焊接时会产生焊接残余应力，残余应力是降低焊接构件性能及可靠性的重要因素。为了研究低温环境对焊接残余应力分布规律的影响，本文通过ABAQUS建立栓钉模型进行数值模拟，考虑了5个不同的温度进行有限元热-固耦合分析。结果表明：mises应力、径向残余应力最大值均位于焊缝附近10mm处，随着距离的增加迅速衰减；环向残余应力在焊缝附近为残余拉应力，远离焊缝处为残余压应力，最大值位于焊缝中心；低温会提高焊接残余应力，mises应力集中表现在焊缝中心，环向残余应力集中表现在焊缝附近，径向残余应力在焊缝中心及焊缝附近均有所增加。低温对提高焊接残余拉应力影响明显，对残余压应力影响不大。

研究目的:郑北大桥索梁锚固结构采用锚拉板结构形式,该区域构造复杂,焊缝交错,部分位置存在明显的应力集中现象,恒载作用下易发生塑性破坏,反复荷载作用下易产生疲劳破坏.通过建立精细化有限元模型,分析锚拉板式索梁锚固结构的易损部位,对局部细节进行设计参数优化,从而改善其恒载和活载下的受力性能.提取疲劳易损部位热点应力,通过热点应力S-N曲线和线性累积损伤理论计算其疲劳寿命,验证参数优化效果. 研究结论:(1)在原设计的基础上适当优化锚拉板厚度能有效改善锚拉板式索梁锚固结构恒载下受力性能,防止材料塑性破坏;(2)经热点应力法计算疲劳寿命验证,在原设计的基础上适当优化圆形过渡区半径、锚拉板厚度、锚筒厚度能提升锚拉板的疲劳寿命;(3)本文研究结论可运用于今后的斜拉桥锚拉板式索梁锚固结构的设计中,以供相关设计人员参考.

研究目的:针对某大跨预应力混凝土连续刚构桥在施工过程中腹板开裂的问题,对该桥主桥腹板所有裂缝进行全面检查,完成可查裂缝宽度、深度的检测.通过归纳总结裂缝的分布特征,利用有限元分析软件ANSYS建立开裂混凝土节段的空间模型,结合腹板开裂相关理论,分析腹板开裂的原因,探究裂缝分布规律.研究结论:(1)腹板两侧的裂缝基本对称于箱梁纵轴线,较多出现在腹板内侧,与腹板下弯束的布置位置、方向符合程度较高;(2)有限元分析结果表明,腹板下弯束及其锚固点周围的部分区域主拉应力超过混凝土抗拉强度设计值,且该区域基本沿预应力束分布;(3)该腹板裂缝属于主拉应力裂缝,过大拉应力主要来源于预应力束径向力、箱梁空间效应产生的次拉力以及锚固应力扰动区的横向拉应力;(4)设计者应重视箱梁横向应力和空间效应,必要时对复杂受力区域进行精细的局部分析,以保证主拉应力不超过限值;(5)本研究成果可为预应力混凝土连续刚构桥的相关设计及施工提供参考借鉴.

为研究全熔透焊接十字接头残余应力空间分布特点,分析十字接头焊缝形式对焊接残余应力分布状态的影响,基于温度场和应力场间接耦合方式,对全熔透焊接十字接头残余应力开展了有限元数值模拟研究.采用ANSYS有限元软件,选择Q345C钢材典型热力学参数,构建全熔透焊接十字接头有限元模型,分析得到焊接过程结构温度场分布.将焊接十字接头温度场作为输入条件,基于ANSYS热–力耦合分析得到全熔透焊接斜十字接头三维残余应力场分布.结果表明,全熔透焊接十字接头残余应力峰值主要分布在焊趾和焊根处,焊缝角度变化会对焊缝处残余应力分布带来较大影响.