Journal of Constructional Steel Research最新文献_第8页

Model and uncertainty of compressive load capacity of steel equal angle connected by one leg 单腿连接等边角钢抗压承载力的模型和不确定性

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-29 DOI: 10.1016/j.jcsr.2024.109088

Xin Zhang, Qiang Xie, Hainan Wu

Steel angle often connects with single leg for construction convenience, which introduces uncertainties in load eccentricity and restraint, making capacity complex to calculate precisely. This research aims to establish a stability coefficient distribution pattern applicable for a wide range of section dimensions, and investigate the effect of structural uncertainty on it. Experiments were conducted to validate the FE models. Subsequently, stability coefficients under commonly used section dimensions were obtained, and influencing parameters were evaluated. Sensitivity and uncertainty analyses were employed to study the impact of structural uncertainty. It was found that the stability coefficients of steel angle connected by one leg form a distribution band, for which a mathematical model was developed. Connection plate dimensions had significant influence on the stability coefficient. Considering structural uncertainty, yield strength and element dimensions had notable sensitivity. And the stability coefficients of the steel angle followed a normal distribution with negative skewness. Therefore, the influence of structural uncertainties cannot be underestimated in the analysis of capacity, and this study provides a reference for their quantitative assessment.

为了施工方便，角钢通常采用单腿连接，这就带来了荷载偏心和约束的不确定性，使承载力的精确计算变得复杂。本研究旨在建立适用于各种截面尺寸的稳定系数分布模式，并研究结构不确定性对其的影响。实验验证了 FE 模型。随后，获得了常用截面尺寸下的稳定系数，并对影响参数进行了评估。采用敏感性和不确定性分析来研究结构不确定性的影响。结果发现，由一条支腿连接的角钢的稳定系数形成了一个分布带，并为此建立了一个数学模型。连接板尺寸对稳定系数有显著影响。考虑到结构的不确定性，屈服强度和元件尺寸具有显著的敏感性。角钢的稳定系数呈负偏态正态分布。因此，在承载力分析中，结构不确定性的影响不可低估，本研究为其定量评估提供了参考。

{"title":"Model and uncertainty of compressive load capacity of steel equal angle connected by one leg","authors":"Xin Zhang, Qiang Xie, Hainan Wu","doi":"10.1016/j.jcsr.2024.109088","DOIUrl":"10.1016/j.jcsr.2024.109088","url":null,"abstract":"<div><div>Steel angle often connects with single leg for construction convenience, which introduces uncertainties in load eccentricity and restraint, making capacity complex to calculate precisely. This research aims to establish a stability coefficient distribution pattern applicable for a wide range of section dimensions, and investigate the effect of structural uncertainty on it. Experiments were conducted to validate the FE models. Subsequently, stability coefficients under commonly used section dimensions were obtained, and influencing parameters were evaluated. Sensitivity and uncertainty analyses were employed to study the impact of structural uncertainty. It was found that the stability coefficients of steel angle connected by one leg form a distribution band, for which a mathematical model was developed. Connection plate dimensions had significant influence on the stability coefficient. Considering structural uncertainty, yield strength and element dimensions had notable sensitivity. And the stability coefficients of the steel angle followed a normal distribution with negative skewness. Therefore, the influence of structural uncertainties cannot be underestimated in the analysis of capacity, and this study provides a reference for their quantitative assessment.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109088"},"PeriodicalIF":4.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental and numerical investigation on the seismic behavior of a novel bolted inter-module connection 新型模块间螺栓连接抗震性能的实验和数值研究

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-29 DOI: 10.1016/j.jcsr.2024.109101

Jincheng Jiang , Zhihua Chen , Yang Liu , Xingwang Liu , Guannan Lu , Xinyu Lin

Modular steel buildings (MSBs) are innovative structures comprising complete components. The design of inter-module connections (IMCs) significantly influences onsite assembly convenience and overall structural performance. IMC designs often incorporate openings in corner fittings' side plates for installation ease, though these may compromise structural integrity. Existing research reveals three main gaps: limited focus on IMC performance under combined loading, inadequate study of openings' impact on seismic resilience, and absence of a restoring force model for unit connections. This study introduces a novel bolted IMC design featuring variable opening sizes. Seismic performance under combined loading was evaluated via experiments and finite element analysis (FEA), leading to a developed restoring force model. Four specimens underwent horizontal quasi-static loading tests under axial pressure, revealing failure modes, hysteresis curves, stiffness degradation, and energy dissipation. A detailed FE model was validated with experimental data, and parametric analysis varied axial compression ratio, bolt sizes, and end plate thickness. Results indicate the new bolted IMCs exhibit satisfactory seismic performance. However, openings significantly reduce seismic resistance, with increased box length notably enhancing it. A restoring force model (RFM) derived from skeleton curves, stiffness degradation, and hysteresis rules correlates well with experimental hysteresis curves, effectively capturing IMCs' seismic response. This model serves as a foundation for designing modular structural systems.

模块化钢结构建筑（MSB）是由完整组件组成的创新结构。模块间连接（IMC）的设计极大地影响了现场组装的便利性和整体结构性能。模块间连接设计通常在角配件侧板上开孔，以方便安装，但这可能会影响结构的完整性。现有研究发现了三个主要差距：对组合荷载下 IMC 性能的关注有限，对开口对抗震性影响的研究不足，以及缺乏单元连接的恢复力模型。本研究介绍了一种新颖的螺栓连接 IMC 设计，其特点是开口尺寸可变。通过实验和有限元分析（FEA）对组合荷载下的抗震性能进行了评估，从而建立了恢复力模型。四个试样在轴向压力下进行了水平准静态加载试验，揭示了失效模式、滞后曲线、刚度退化和能量耗散。详细的 FE 模型与实验数据进行了验证，参数分析改变了轴向压缩比、螺栓尺寸和端板厚度。结果表明，新型螺栓连接 IMC 的抗震性能令人满意。然而，开口会大大降低抗震性能，而增加箱体长度则会明显提高抗震性能。根据骨架曲线、刚度退化和滞后规则推导出的恢复力模型（RFM）与实验滞后曲线相关性良好，能有效捕捉 IMC 的地震响应。该模型是设计模块化结构系统的基础。

{"title":"Experimental and numerical investigation on the seismic behavior of a novel bolted inter-module connection","authors":"Jincheng Jiang , Zhihua Chen , Yang Liu , Xingwang Liu , Guannan Lu , Xinyu Lin","doi":"10.1016/j.jcsr.2024.109101","DOIUrl":"10.1016/j.jcsr.2024.109101","url":null,"abstract":"<div><div>Modular steel buildings (MSBs) are innovative structures comprising complete components. The design of inter-module connections (IMCs) significantly influences onsite assembly convenience and overall structural performance. IMC designs often incorporate openings in corner fittings' side plates for installation ease, though these may compromise structural integrity. Existing research reveals three main gaps: limited focus on IMC performance under combined loading, inadequate study of openings' impact on seismic resilience, and absence of a restoring force model for unit connections. This study introduces a novel bolted IMC design featuring variable opening sizes. Seismic performance under combined loading was evaluated via experiments and finite element analysis (FEA), leading to a developed restoring force model. Four specimens underwent horizontal quasi-static loading tests under axial pressure, revealing failure modes, hysteresis curves, stiffness degradation, and energy dissipation. A detailed FE model was validated with experimental data, and parametric analysis varied axial compression ratio, bolt sizes, and end plate thickness. Results indicate the new bolted IMCs exhibit satisfactory seismic performance. However, openings significantly reduce seismic resistance, with increased box length notably enhancing it. A restoring force model (RFM) derived from skeleton curves, stiffness degradation, and hysteresis rules correlates well with experimental hysteresis curves, effectively capturing IMCs' seismic response. This model serves as a foundation for designing modular structural systems.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109101"},"PeriodicalIF":4.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental and numerical investigation of fire resistance of G550 galvanized steel-concrete slabs G550 镀锌钢-混凝土楼板耐火性的实验和数值研究

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-25 DOI: 10.1016/j.jcsr.2024.109092

Yun Cheng , Xianglin Yu , Yongjiu Shi , YiuKwong Pang

This paper investigates the increasing demand for improved fire performance of composite floor systems in high-rise buildings by constructing a new type of composite slab, which is composed of concrete and closed profiled steel deck fabricated with G550 galvanized steel. Six full-scale standard fire tests of composite slabs are conducted to understand the thermal-mechanical response of the new composite slab. The results reveal that the fire duration of all the novel composite slabs exceeds 60 min, demonstrating significantly improved fire performance comparing to a conventional slab. The failure mode for all tested composite slabs is flexural failure, with limited end slip that indicates a good preservation of composite action during fire exposure. Based on the experimental results, numerical model is established and validated through the comparison of temperature and deformation data. A series of parametric analyses are carried out numerically, where overall slab depth, deck depth, supported span and uniform loads are identified as the dominant effects on the fire resistance. The results indicate that the existing design methods specified in the current standards are not fully applicable to the newly proposed composite slab. Simplified calculating methods for insulation-based and bearing capacity-based fire resistance are suggested.

本文通过建造一种新型复合楼板（由混凝土和用 G550 镀锌钢制造的封闭式异型钢板组成），研究了高层建筑对提高复合楼板系统防火性能的日益增长的需求。为了解新型复合楼板的热机械响应，对复合楼板进行了六次全尺寸标准火灾试验。结果显示，所有新型复合楼板的防火持续时间都超过了 60 分钟，与传统楼板相比，防火性能显著提高。所有测试的复合材料板的破坏模式都是挠曲破坏，末端滑移有限，这表明在火灾暴露期间复合材料的作用得到了很好的保护。根据实验结果，建立了数值模型，并通过温度和变形数据的比较进行了验证。通过数值分析进行了一系列参数分析，确定了板的总深度、桥面深度、支撑跨度和均布荷载对耐火性的主要影响。结果表明，现行标准中规定的现有设计方法并不完全适用于新提出的复合楼板。建议采用基于隔热和基于承载力的简化耐火计算方法。

{"title":"Experimental and numerical investigation of fire resistance of G550 galvanized steel-concrete slabs","authors":"Yun Cheng , Xianglin Yu , Yongjiu Shi , YiuKwong Pang","doi":"10.1016/j.jcsr.2024.109092","DOIUrl":"10.1016/j.jcsr.2024.109092","url":null,"abstract":"<div><div>This paper investigates the increasing demand for improved fire performance of composite floor systems in high-rise buildings by constructing a new type of composite slab, which is composed of concrete and closed profiled steel deck fabricated with G550 galvanized steel. Six full-scale standard fire tests of composite slabs are conducted to understand the thermal-mechanical response of the new composite slab. The results reveal that the fire duration of all the novel composite slabs exceeds 60 min, demonstrating significantly improved fire performance comparing to a conventional slab. The failure mode for all tested composite slabs is flexural failure, with limited end slip that indicates a good preservation of composite action during fire exposure. Based on the experimental results, numerical model is established and validated through the comparison of temperature and deformation data. A series of parametric analyses are carried out numerically, where overall slab depth, deck depth, supported span and uniform loads are identified as the dominant effects on the fire resistance. The results indicate that the existing design methods specified in the current standards are not fully applicable to the newly proposed composite slab. Simplified calculating methods for insulation-based and bearing capacity-based fire resistance are suggested.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109092"},"PeriodicalIF":4.0,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Sensitivity analysis and failure prediction of X80 pipeline under transverse landslide 横向滑坡下 X80 管道的敏感性分析和故障预测

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-25 DOI: 10.1016/j.jcsr.2024.109090

Youcai Xiang , Li Zhu , Bin Jia , Lei Zhao , Naixian Li , Youkai Gu , Peng Ren

To investigate the mechanical response of X80 pipelines under lateral landslide conditions, finite element simulations of X80 pipeline under 375 lateral landslide conditions are conducted in this paper to examine mechanical behavior under varying pipe diameters and wall thicknesses, and landslide width and displacement on pipeline strain is assessed. The results indicate that under the influence of lateral landslides, The pipeline strain is predominantly induced by the bending moment, with axial strain being the most significant, constituting over 95 % of the total strain. The peak strain is primarily concentrated in the middle section of the pipeline's leading span. Based on extensive numerical simulation data, a grey relational analysis was conducted, revealing that the primary factors influencing the maximum axial strain in pipelines, in descending order of significance, are landslide displacement, landslide width, pipeline diameter, and pipeline wall thickness. Furthermore, to predict the safety of X80 pipelines under lateral landslides, a BP neural network prediction model and a fitting formula are developed based on the four influencing factors. Both the model and the formula were validated to accurately predict the maximum axial strain of X80 pipelines affected by lateral landslides. Moreover, a failure assessment method for X80 pipelines under lateral landslide conditions was established using the strain failure criterion. Results indicate that the prediction errors of the neural network model and the formula, compared to simulation outcomes, are within 10 %, the high accuracy of the failure prediction results is similarly demonstrated.

为了研究 X80 管道在侧向滑坡条件下的力学响应，本文对 375 种侧向滑坡条件下的 X80 管道进行了有限元模拟，以研究不同管道直径和壁厚下的力学行为，并评估滑坡宽度和位移对管道应变的影响。结果表明，在横向滑坡的影响下，管道应变主要由弯矩引起，其中轴向应变最为显著，占总应变的 95% 以上。应变峰值主要集中在管道前跨的中间部分。在大量数值模拟数据的基础上，进行了灰色关系分析，结果表明影响管道最大轴向应变的主要因素从大到小依次为滑坡位移、滑坡宽度、管道直径和管道壁厚。此外，为了预测 X80 管道在横向滑坡作用下的安全性，根据这四个影响因素建立了 BP 神经网络预测模型和拟合公式。经验证，该模型和公式均能准确预测受横向滑坡影响的 X80 管道的最大轴向应变。此外，还利用应变失效准则建立了横向滑坡条件下 X80 管道的失效评估方法。结果表明，与模拟结果相比，神经网络模型和公式的预测误差均在 10% 以内，同样证明了失效预测结果的高准确性。

{"title":"Sensitivity analysis and failure prediction of X80 pipeline under transverse landslide","authors":"Youcai Xiang , Li Zhu , Bin Jia , Lei Zhao , Naixian Li , Youkai Gu , Peng Ren","doi":"10.1016/j.jcsr.2024.109090","DOIUrl":"10.1016/j.jcsr.2024.109090","url":null,"abstract":"<div><div>To investigate the mechanical response of X80 pipelines under lateral landslide conditions, finite element simulations of X80 pipeline under 375 lateral landslide conditions are conducted in this paper to examine mechanical behavior under varying pipe diameters and wall thicknesses, and landslide width and displacement on pipeline strain is assessed. The results indicate that under the influence of lateral landslides, The pipeline strain is predominantly induced by the bending moment, with axial strain being the most significant, constituting over 95 % of the total strain. The peak strain is primarily concentrated in the middle section of the pipeline's leading span. Based on extensive numerical simulation data, a grey relational analysis was conducted, revealing that the primary factors influencing the maximum axial strain in pipelines, in descending order of significance, are landslide displacement, landslide width, pipeline diameter, and pipeline wall thickness. Furthermore, to predict the safety of X80 pipelines under lateral landslides, a BP neural network prediction model and a fitting formula are developed based on the four influencing factors. Both the model and the formula were validated to accurately predict the maximum axial strain of X80 pipelines affected by lateral landslides. Moreover, a failure assessment method for X80 pipelines under lateral landslide conditions was established using the strain failure criterion. Results indicate that the prediction errors of the neural network model and the formula, compared to simulation outcomes, are within 10 %, the high accuracy of the failure prediction results is similarly demonstrated.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109090"},"PeriodicalIF":4.0,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of cyclic loading and high-temperature cooling on mechanical properties of Q450 weathering steel 循环加载和高温冷却对 Q450 耐候钢机械性能的影响

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-25 DOI: 10.1016/j.jcsr.2024.109084

Chuntao Zhang , Linwei Cui , Zhisong Wang

The investigation of the mechanical properties of steel structures after cyclic loadings such as earthquakes, wind vibrations, and high-temperature cooling helps to study the stability of steel structures in extremely complex environments. Hence, this study investigates the mechanical characteristics of cyclically loaded Q450 weathering steel after high-temperature cooling. Before the tensile test, Q450 weathering steel was previously damaged by cyclic loading, and then the Q450 weathering steel specimens with different cyclic loading damages were heated and cooled. Based on the test results, the effect of the sequence of cyclic loading and high-temperature cooling on the mechanical characteristics of steel was also discussed. The failure model of cyclically loaded Q450 weathering steel after high-temperature cooling was observed. The residual mechanical characteristics of Q450 weathering steel after being subjected to extreme environments were discussed by comparing the mechanical characteristics of undamaged steel specimens. The test findings reveal that the cyclic loading pre-damage, heating temperature, and cooling method greatly impact the important parameters of Q450 weathering steel, such as strength, elastic modulus, and ductility. Comparing the sequence of cyclic loading, heating and cooling, Q450 weathering steel with cyclic loading pre-damage of 95 % was considerably influenced by the sequence of extreme environments. In contrast, the influence of the extreme environmental sequence was not significant when the pre-damage was 50 % and 75 %. In addition, the modulus of elasticity is indifferent to the extreme environmental sequences, whereas the elongation displays complicated change patterns under varied degrees of pre-damage. Finally, the stress-strain relationship considering the interactive effects of cyclic loading damage, temperature, and cooling method was proposed using a multi-component numerical model.

对钢结构在地震、风振和高温冷却等循环加载后的机械特性进行研究，有助于研究钢结构在极其复杂的环境中的稳定性。因此，本研究调查了高温冷却后循环加载 Q450 耐候钢的机械特性。在进行拉伸试验之前，先对 Q450 耐候钢进行循环加载破坏，然后对不同循环加载破坏的 Q450 耐候钢试样进行加热和冷却。根据试验结果，还讨论了循环加载和高温冷却的顺序对钢材力学特性的影响。观察了高温冷却后循环加载 Q450 风化钢的失效模型。通过比较未损坏钢试样的机械特性，讨论了 Q450 耐候钢在极端环境下的残余机械特性。试验结果表明，损伤前的循环加载、加热温度和冷却方法对 Q450 耐候钢的强度、弹性模量和延展性等重要参数有很大影响。比较循环加载、加热和冷却的顺序，循环加载预破坏为 95% 的 Q450 耐候钢受极端环境顺序的影响很大。相比之下，当预损伤为 50% 和 75% 时，极端环境序列的影响并不显著。此外，弹性模量与极端环境序列无关，而伸长率则在不同程度的预破坏下显示出复杂的变化规律。最后，利用多组分数值模型提出了考虑到循环加载损伤、温度和冷却方法交互影响的应力-应变关系。

{"title":"Effects of cyclic loading and high-temperature cooling on mechanical properties of Q450 weathering steel","authors":"Chuntao Zhang , Linwei Cui , Zhisong Wang","doi":"10.1016/j.jcsr.2024.109084","DOIUrl":"10.1016/j.jcsr.2024.109084","url":null,"abstract":"<div><div>The investigation of the mechanical properties of steel structures after cyclic loadings such as earthquakes, wind vibrations, and high-temperature cooling helps to study the stability of steel structures in extremely complex environments. Hence, this study investigates the mechanical characteristics of cyclically loaded Q450 weathering steel after high-temperature cooling. Before the tensile test, Q450 weathering steel was previously damaged by cyclic loading, and then the Q450 weathering steel specimens with different cyclic loading damages were heated and cooled. Based on the test results, the effect of the sequence of cyclic loading and high-temperature cooling on the mechanical characteristics of steel was also discussed. The failure model of cyclically loaded Q450 weathering steel after high-temperature cooling was observed. The residual mechanical characteristics of Q450 weathering steel after being subjected to extreme environments were discussed by comparing the mechanical characteristics of undamaged steel specimens. The test findings reveal that the cyclic loading pre-damage, heating temperature, and cooling method greatly impact the important parameters of Q450 weathering steel, such as strength, elastic modulus, and ductility. Comparing the sequence of cyclic loading, heating and cooling, Q450 weathering steel with cyclic loading pre-damage of 95 % was considerably influenced by the sequence of extreme environments. In contrast, the influence of the extreme environmental sequence was not significant when the pre-damage was 50 % and 75 %. In addition, the modulus of elasticity is indifferent to the extreme environmental sequences, whereas the elongation displays complicated change patterns under varied degrees of pre-damage. Finally, the stress-strain relationship considering the interactive effects of cyclic loading damage, temperature, and cooling method was proposed using a multi-component numerical model.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109084"},"PeriodicalIF":4.0,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental study on a single-sided resilient composite beam–column joint 单面弹性复合梁柱连接实验研究

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-25 DOI: 10.1016/j.jcsr.2024.109102

Hao Wen , Yulong Feng , Yuhang Wang , Xiaogang Huang

This paper presents an experimental study on a single-sided resilient composite beam–column joint, in which a nonreplaceable concrete slab and connection plate and a replaceable buckling-restrained cover plate (BRCP) are installed at the top and bottom flanges, respectively. The seismic performance and replaceability of the proposed joint were investigated considering the influence of the concrete slab. One specimen was cyclically loaded under 2 % rotation, and then the damaged core plate of the BRCP was replaced to form a new specimen that was cyclically loaded under 4 % rotation. The results showed that the neutral axis was shifted upward to the top flange, which made the damage concentrate in the core plate, and only minor damage occurred to the connection plate and concrete slab under 2 % rotation. The hysteresis curve after replacement was almost the same as that before replacement under 2 % rotation and showed full and stable loops without decrease in load capacity under 4 % rotation, implying good seismic performance and replaceability. In addition, the proposed joint was compared with a bare steel joint to examine the effects of concrete slabs. Further, a numerical model of the specimen was developed and verified by comparison with the test results to better understand the test and study the influence of connection plates. Finally, the formulas for the yield moment and initial stiffness of the joint were derived and compared with test results to verify the accuracy of the formulas. The influence of the reduction in core plate area on the joint stiffness and neutral axis position was discussed using the formulas.

本文介绍了对单侧弹性复合梁柱连接的实验研究，其中在顶部和底部翼缘分别安装了不可更换的混凝土板和连接板以及可更换的屈曲约束盖板（BRCP）。考虑到混凝土板的影响，对拟议接头的抗震性能和可更换性进行了研究。一个试件在 2% 的旋转下循环加载，然后更换损坏的 BRCP 核心板，形成一个新的试件，在 4% 的旋转下循环加载。结果表明，中性轴向上移动到了上翼缘，这使得损坏集中在芯板上，而连接板和混凝土板在 2% 的旋转下仅发生了轻微损坏。在旋转 2% 的情况下，更换后的滞后曲线与更换前基本相同；在旋转 4% 的情况下，滞后曲线显示出完整而稳定的循环，承载能力没有下降，这意味着该接头具有良好的抗震性能和可更换性。此外，还将拟议的接头与裸钢接头进行了比较，以考察混凝土板的影响。此外，还开发了试件的数值模型，并通过与试验结果的对比进行了验证，以更好地理解试验并研究连接板的影响。最后，推导出了连接处的屈服力矩和初始刚度公式，并与试验结果进行了对比，以验证公式的准确性。利用公式讨论了核心板面积减小对连接刚度和中轴位置的影响。

{"title":"Experimental study on a single-sided resilient composite beam–column joint","authors":"Hao Wen , Yulong Feng , Yuhang Wang , Xiaogang Huang","doi":"10.1016/j.jcsr.2024.109102","DOIUrl":"10.1016/j.jcsr.2024.109102","url":null,"abstract":"<div><div>This paper presents an experimental study on a single-sided resilient composite beam–column joint, in which a nonreplaceable concrete slab and connection plate and a replaceable buckling-restrained cover plate (BRCP) are installed at the top and bottom flanges, respectively. The seismic performance and replaceability of the proposed joint were investigated considering the influence of the concrete slab. One specimen was cyclically loaded under 2 % rotation, and then the damaged core plate of the BRCP was replaced to form a new specimen that was cyclically loaded under 4 % rotation. The results showed that the neutral axis was shifted upward to the top flange, which made the damage concentrate in the core plate, and only minor damage occurred to the connection plate and concrete slab under 2 % rotation. The hysteresis curve after replacement was almost the same as that before replacement under 2 % rotation and showed full and stable loops without decrease in load capacity under 4 % rotation, implying good seismic performance and replaceability. In addition, the proposed joint was compared with a bare steel joint to examine the effects of concrete slabs. Further, a numerical model of the specimen was developed and verified by comparison with the test results to better understand the test and study the influence of connection plates. Finally, the formulas for the yield moment and initial stiffness of the joint were derived and compared with test results to verify the accuracy of the formulas. The influence of the reduction in core plate area on the joint stiffness and neutral axis position was discussed using the formulas.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109102"},"PeriodicalIF":4.0,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Computational analysis of wildland fire resistance for transmission line tower 输电线路铁塔抗野外火灾能力的计算分析

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-24 DOI: 10.1016/j.jcsr.2024.109097

Chang Chen , Hamid R. Valipour , Mark A. Bradford , Xinpei Liu , Donghong Zhang

Finite element (FE) analysis of the transmission towers under a fire event and the accompanying wind is presented. Several key aspects (including temperature-dependent non-linear material properties, geometric non-linearity, member eccentricity due to the single-leg bolted connection, and the temperature-dependent connection behaviour in both the axial and the rotational directions) are considered. A quasi-static analysis is also employed in the FE model using the explicit solver available in Abaqus. The member temperature variation during a realistic fire event is derived analytically based on the fire intensity and the resultant vertical gas temperature distribution so that the effect of the realistic wildland fire can be input as a member temperature profile. First, fire design guidance in terms of the most critical heating and wind pattern, as well as the effect of fire-affected heights are provided based on the case study results. Then, further fire analysis is carried out to investigate the most critical fire scenario and to evaluate the vulnerability of the tower during a realistic fire event. Lastly, an evaluation of a commonly used spray-on thermal insulation and its effectiveness in reducing the member temperature and preserving ultimate strength during a catastrophic wildland fire event are presented. The FE simulations revealed that a 45-degree wind associated with partial side heating leads to a more critical degradation of the overall strength, whereas the effect of fire height is less obvious. In terms of the fire scenario, a longer fire duration associated with a slower wind is more critical for the fire resistance/rating.

本文介绍了在火灾事件和伴随的风力作用下对输电塔进行的有限元（FE）分析。分析考虑了几个关键方面（包括与温度相关的非线性材料特性、几何非线性、单腿螺栓连接造成的构件偏心，以及轴向和旋转方向上与温度相关的连接行为）。FE 模型还使用了 Abaqus 中的显式求解器进行准静态分析。现实火灾事件中的构件温度变化是根据火灾强度和由此产生的垂直气体温度分布分析得出的，因此可以将现实野外火灾的影响作为构件温度曲线输入。首先，根据案例研究结果，从最关键的加热和风力模式以及受火灾影响高度的影响等方面提供火灾设计指导。然后，进行了进一步的火灾分析，以研究最关键的火灾情况，并评估塔楼在实际火灾事件中的脆弱性。最后，对常用的喷涂隔热材料及其在灾难性野外火灾事件中降低构件温度和保持极限强度的有效性进行了评估。有限元模拟结果表明，45 度风和部分侧面加热会导致整体强度的严重下降，而火灾高度的影响则不太明显。就火灾情况而言，火灾持续时间越长，风速越慢，对耐火性/等级的影响就越大。

{"title":"Computational analysis of wildland fire resistance for transmission line tower","authors":"Chang Chen , Hamid R. Valipour , Mark A. Bradford , Xinpei Liu , Donghong Zhang","doi":"10.1016/j.jcsr.2024.109097","DOIUrl":"10.1016/j.jcsr.2024.109097","url":null,"abstract":"<div><div>Finite element (FE) analysis of the transmission towers under a fire event and the accompanying wind is presented. Several key aspects (including temperature-dependent non-linear material properties, geometric non-linearity, member eccentricity due to the single-leg bolted connection, and the temperature-dependent connection behaviour in both the axial and the rotational directions) are considered. A quasi-static analysis is also employed in the FE model using the explicit solver available in Abaqus. The member temperature variation during a realistic fire event is derived analytically based on the fire intensity and the resultant vertical gas temperature distribution so that the effect of the realistic wildland fire can be input as a member temperature profile. First, fire design guidance in terms of the most critical heating and wind pattern, as well as the effect of fire-affected heights are provided based on the case study results. Then, further fire analysis is carried out to investigate the most critical fire scenario and to evaluate the vulnerability of the tower during a realistic fire event. Lastly, an evaluation of a commonly used spray-on thermal insulation and its effectiveness in reducing the member temperature and preserving ultimate strength during a catastrophic wildland fire event are presented. The FE simulations revealed that a 45-degree wind associated with partial side heating leads to a more critical degradation of the overall strength, whereas the effect of fire height is less obvious. In terms of the fire scenario, a longer fire duration associated with a slower wind is more critical for the fire resistance/rating.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109097"},"PeriodicalIF":4.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Design and shock isolation performances of two-layered ring-spring meta-isolation systems 双层环形弹簧元隔振系统的设计和隔振性能

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-24 DOI: 10.1016/j.jcsr.2024.109098

Dongyu Shi , Jue Han , Hualin Fan

Two-layered ring-spring-resonator (RSR) based meta-isolation system (RSR-M) has been developed to improve shock isolation effect. In the numerical calculations, shock acceleration ratio (SAR), shock displacement ratio (SDR) and relative displacement ratio (RDR) were introduced to evaluate the shock isolation performances of the conventional isolation system (CON) and the RSR-M, considering the effects of the excitation amplitude, the weight of the middle mass block and the stiffness of the lower isolators. The results demonstrate that the SAR of the RSR-M is always smaller than that of the CON, and the SDR of the RSR-M is first larger than that of CON in the shock amplification region and then smaller in the isolation region. The weight of middle mass blocks has little influence on the isolation performance of the RSR-M because of the softening behavior of the isolators. Finally, shock isolation experiments were also carried out to measure the damping ratios of the selected wire rope isolators and further analyze the isolation performance of the RSR-Ms. In general, meta-isolation system provides a new reference and idea for the design of the isolation system of engineering structures in some sense.

为改善隔震效果，我们开发了基于双层环簧谐振器（RSR）的元隔震系统（RSR-M）。在数值计算中，引入了冲击加速度比（SAR）、冲击位移比（SDR）和相对位移比（RDR）来评估传统隔振系统（CON）和 RSR-M 的隔振性能，同时考虑了激励振幅、中间质量块重量和下部隔振器刚度的影响。结果表明，RSR-M 的 SAR 始终小于 CON，RSR-M 的 SDR 首先在冲击放大区域大于 CON，然后在隔离区域小于 CON。由于隔振器的软化行为，中间质量块的重量对 RSR-M 的隔振性能影响不大。最后，还进行了隔振实验，测量了所选钢丝绳隔振器的阻尼比，进一步分析了 RSR-M 的隔振性能。总的来说，元隔振系统在一定意义上为工程结构隔振系统的设计提供了新的参考和思路。

{"title":"Design and shock isolation performances of two-layered ring-spring meta-isolation systems","authors":"Dongyu Shi , Jue Han , Hualin Fan","doi":"10.1016/j.jcsr.2024.109098","DOIUrl":"10.1016/j.jcsr.2024.109098","url":null,"abstract":"<div><div>Two-layered ring-spring-resonator (RSR) based meta-isolation system (RSR-M) has been developed to improve shock isolation effect. In the numerical calculations, shock acceleration ratio (SAR), shock displacement ratio (SDR) and relative displacement ratio (RDR) were introduced to evaluate the shock isolation performances of the conventional isolation system (CON) and the RSR-M, considering the effects of the excitation amplitude, the weight of the middle mass block and the stiffness of the lower isolators. The results demonstrate that the SAR of the RSR-M is always smaller than that of the CON, and the SDR of the RSR-M is first larger than that of CON in the shock amplification region and then smaller in the isolation region. The weight of middle mass blocks has little influence on the isolation performance of the RSR-M because of the softening behavior of the isolators. Finally, shock isolation experiments were also carried out to measure the damping ratios of the selected wire rope isolators and further analyze the isolation performance of the RSR-Ms. In general, meta-isolation system provides a new reference and idea for the design of the isolation system of engineering structures in some sense.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109098"},"PeriodicalIF":4.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Test-and-FE-based method for obtaining complete stress-strain curves of structural steels including fracture 基于测试和 FE 的结构钢完整应力应变曲线（包括断裂）获取方法

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-24 DOI: 10.1016/j.jcsr.2024.109095

Jingsheng Zhou , Shen Yan , Kim J.R. Rasmussen , Mengyao Zhang

Ductile fracture is a common limit state of frameworks of steel structures and can be predicted by incorporating models for fracture initiation and propagation in finite element (FE) analyses. However, accurate prediction of fracture relies on unique fracture parameters for a given material, requiring precise predictions of fracture strain and stress states obtained through coupon tests and accompanying FE data analysis. In recent decades, various methods have been proposed to predict ductile fracture initiation, including various design geometries of coupons, test setups and FE analyses, which may lead to inconsistent fracture strains and stress states. Hence, there is a need for proposing a standard procedure for the design, test and accompanying FE-based calibration of fracture parameters, as pursued in this paper. Given that ductile fracture initiates under significant plastic strain, a constitutive model for the full strain range is required, as also proposed in this paper. Moreover, to reduce the experimental and data analytical efforts, an empirical method is proposed that uses only a small number of coupon tests to calibrate the fracture parameters. The method encompasses three levels wherein one, two, or three coupon tests are required. All in all, the paper presents a methodology for determining the full-range true stress-strain curve and the initiation of fracture, including a new post-necking constitutive model and methods for determining the free parameters of the post-necking and fracture initiation models. While applied to steel in this paper, the proposed methodology is potentially also applicable to other metals.

韧性断裂是钢结构框架的常见极限状态，可以通过在有限元（FE）分析中加入断裂起始和扩展模型进行预测。然而，断裂的准确预测依赖于特定材料的独特断裂参数，需要通过试样测试和相应的有限元数据分析获得断裂应变和应力状态的精确预测。近几十年来，人们提出了各种预测韧性断裂起始的方法，包括各种试样设计几何形状、测试设置和 FE 分析，这些方法可能会导致断裂应变和应力状态不一致。因此，有必要提出一种标准程序，用于设计、测试和基于有限元分析的断裂参数校准，这也是本文所追求的目标。鉴于韧性断裂是在显著的塑性应变下发生的，因此需要一个全应变范围的构成模型，本文也提出了这一建议。此外，为了减少实验和数据分析工作，本文提出了一种经验方法，只使用少量的试样测试来校准断裂参数。该方法包括三个层次，分别需要进行一次、两次或三次试样测试。总之，本文提出了一种确定全范围真实应力-应变曲线和断裂起始的方法，包括一种新的缩颈后构成模型以及确定缩颈后和断裂起始模型自由参数的方法。本文所提出的方法适用于钢材，但也可能适用于其他金属。

{"title":"Test-and-FE-based method for obtaining complete stress-strain curves of structural steels including fracture","authors":"Jingsheng Zhou , Shen Yan , Kim J.R. Rasmussen , Mengyao Zhang","doi":"10.1016/j.jcsr.2024.109095","DOIUrl":"10.1016/j.jcsr.2024.109095","url":null,"abstract":"<div><div>Ductile fracture is a common limit state of frameworks of steel structures and can be predicted by incorporating models for fracture initiation and propagation in finite element (FE) analyses. However, accurate prediction of fracture relies on unique fracture parameters for a given material, requiring precise predictions of fracture strain and stress states obtained through coupon tests and accompanying FE data analysis. In recent decades, various methods have been proposed to predict ductile fracture initiation, including various design geometries of coupons, test setups and FE analyses, which may lead to inconsistent fracture strains and stress states. Hence, there is a need for proposing a standard procedure for the design, test and accompanying FE-based calibration of fracture parameters, as pursued in this paper. Given that ductile fracture initiates under significant plastic strain, a constitutive model for the full strain range is required, as also proposed in this paper. Moreover, to reduce the experimental and data analytical efforts, an empirical method is proposed that uses only a small number of coupon tests to calibrate the fracture parameters. The method encompasses three levels wherein one, two, or three coupon tests are required. All in all, the paper presents a methodology for determining the full-range true stress-strain curve and the initiation of fracture, including a new post-necking constitutive model and methods for determining the free parameters of the post-necking and fracture initiation models. While applied to steel in this paper, the proposed methodology is potentially also applicable to other metals.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109095"},"PeriodicalIF":4.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Failure of the SRC under freeze- thaw cycles by the push-out tests 在冻融循环条件下，通过挤出试验确定 SRC 的失效情况

IF 4 2区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Journal of Constructional Steel Research

Pub Date : 2024-10-24 DOI: 10.1016/j.jcsr.2024.109100

Weichen Wang, Junhua Li, Chen Pingjun, Chunheng Zhou, Yansheng Guo, Zhicheng Yao

This paper explores the impact of freeze-thaw cycles, the thickness of the protective layer, embedment length, and volumetric hoop ratio on the bond performance at the SRC interface, assessed through freeze-thaw and push-out tests. Results from SEM indicated significant cracking in concrete exposed to freeze-thaw cycles, with an increase in both the number and diameter of pores. Despite significant damage to the concrete exterior, the interface exhibited considerably less deterioration. Following 200 freeze-thaw cycles, the specimens displayed a maximum crack depth of 2.3 mm and a porosity rate of 35.1 %. As the cycles progressed, the failure mode of specimens under push-out loading transitioned from splitting to interfacial shear failure. Notably, the length of cracks on the end surfaces was markedly reduced, and the majority of specimens exhibited minimal cracking on the side surfaces. Additionally, interfacial bond stress decreased progressively with the increasing number of cycles. The ultimate bond stress declined more rapidly than residual bond stress, with the rate of decrease stabilizing after surpassing 100 cycles. Enhancements in protective layer thickness, embedment length, and volumetric hoop ratio effectively mitigated the reductions in bond stress. Among these, the protective layer had the most significant impact, followed by the volumetric hoop ratio, while embedment length had the least influence. The study concludes with proposed formulas for calculating bond stress and slip eigenvalues after freeze-thaw cycles, integrating experimental results and theoretical analysis.

本文通过冻融和推出试验，探讨了冻融循环、保护层厚度、预埋长度和体积环比对 SRC 接口粘结性能的影响。扫描电子显微镜的结果表明，暴露在冻融循环中的混凝土出现了明显的开裂，孔隙的数量和直径都有所增加。尽管混凝土外部受到了严重破坏，但界面的损坏程度要小得多。经过 200 次冻融循环后，试样的最大裂缝深度为 2.3 毫米，孔隙率为 35.1%。随着冻融循环的进行，试样在推出荷载作用下的破坏模式从劈裂过渡到界面剪切破坏。值得注意的是，端面的裂缝长度明显减少，大多数试样的侧面裂缝极少。此外，界面粘接应力随着循环次数的增加而逐渐减小。极限粘接应力比残余粘接应力下降得更快，在超过 100 次循环后，下降速度趋于稳定。保护层厚度、嵌入长度和体积环比的增加有效缓解了粘接应力的降低。其中，保护层的影响最大，其次是体积环比，而嵌入长度的影响最小。研究最后结合实验结果和理论分析，提出了冻融循环后粘结应力和滑移特征值的计算公式。

{"title":"Failure of the SRC under freeze- thaw cycles by the push-out tests","authors":"Weichen Wang, Junhua Li, Chen Pingjun, Chunheng Zhou, Yansheng Guo, Zhicheng Yao","doi":"10.1016/j.jcsr.2024.109100","DOIUrl":"10.1016/j.jcsr.2024.109100","url":null,"abstract":"<div><div>This paper explores the impact of freeze-thaw cycles, the thickness of the protective layer, embedment length, and volumetric hoop ratio on the bond performance at the SRC interface, assessed through freeze-thaw and push-out tests. Results from SEM indicated significant cracking in concrete exposed to freeze-thaw cycles, with an increase in both the number and diameter of pores. Despite significant damage to the concrete exterior, the interface exhibited considerably less deterioration. Following 200 freeze-thaw cycles, the specimens displayed a maximum crack depth of 2.3 mm and a porosity rate of 35.1 %. As the cycles progressed, the failure mode of specimens under push-out loading transitioned from splitting to interfacial shear failure. Notably, the length of cracks on the end surfaces was markedly reduced, and the majority of specimens exhibited minimal cracking on the side surfaces. Additionally, interfacial bond stress decreased progressively with the increasing number of cycles. The ultimate bond stress declined more rapidly than residual bond stress, with the rate of decrease stabilizing after surpassing 100 cycles. Enhancements in protective layer thickness, embedment length, and volumetric hoop ratio effectively mitigated the reductions in bond stress. Among these, the protective layer had the most significant impact, followed by the volumetric hoop ratio, while embedment length had the least influence. The study concludes with proposed formulas for calculating bond stress and slip eigenvalues after freeze-thaw cycles, integrating experimental results and theoretical analysis.</div></div>","PeriodicalId":15557,"journal":{"name":"Journal of Constructional Steel Research","volume":"224 ","pages":"Article 109100"},"PeriodicalIF":4.0,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142532215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0