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Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 297-307 doi: 10.1007/s11709-012-0162-x

摘要： Steel is widely used for the construction of bridges, buildings, towers, and other structures because of its great strength, light weight, ductility, and ease of fabrication, but the cost of fireproofing is a major disadvantage. Therefore, the resistance of a steel structure to fire is a significant subject for modern society. In the past, for simplification, creep behavior was not taken into account in research on the resistance of a steel structure to fire. However, it was demonstrated that the effect of creep is considerable at temperatures that commonly reach 600°C and should not be neglected in this context. In this paper, a co-rotational total Lagrangian finite element formulation is derived, and the corresponding numerical model is developed to study the creep behavior of plane steel frames in fire conditions. The geometric nonlinearity, material nonlinearity, high temperature creep, and temperature rate of change are taken into account. To verify the accuracy and efficiency of the numerical model, four prototypical numerical examples are analyzed using this model, and the results show very good agreement with the solutions in the literature. Next, the numerical model is used to analyze the creep behavior of the plane steel frames under decreasing temperatures. The results indicate that the effect of creep is negligible at temperatures lower than 500°C and is considerable at temperatures higher than 500°C. In addition, the heating rate is a critical factor in the failure point of the steel frames. Furthermore, it is demonstrated that the deflection at the midpoint of the steel beam, considering creep behavior, is approximately 13% larger than for the situation in which creep is ignored. At temperatures higher than 500°C, the deformed steel member may recover approximately 20% of the total deflection. The application of the numerical model proposed in this paper is greatly beneficial to the steel industry for creep analysis, and the numerical results make a significant contribution to the understanding of resistance and protection for steel structures against disastrous fires.

关键词： creep     plane steel frame     fire     finite element method     geometric nonlinearity    

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A model for creep life prediction of thin tube using strain energy density as a function of stress triaxialityunder quasi-static loading employing elastic-creep & elastic-plastic-creep deformation

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

《机械工程前沿（英文）》 2013年 第8卷 第2期   页码 181-186 doi: 10.1007/s11465-013-0257-7

摘要：

This paper demonstrates the application of a new multiaxial creep damage model developed by authors using stress traixiality to predict the failure time of a component made of 0.5%Cr-0.5%Mo-0.25%V low alloy steel. The model employs strain energy density and assumes that the uniaxial strain energy density of a component can be easily calculated and can be converted to multi-axial strain energy density by multiplying it to a function of stress trixiality which is a ratio of mean stress to equivalent stress. For comparison, an elastic-creep and elastic-plastic-creep finite element analysis (FEA) is performed to get multi-axial strain energy density of the component which is compared with the calculated strain energy density for both cases. The verification and application of the model are demonstrated by applying it to thin tube for which the experimental data are available. The predicted failure times by the model are compared with the experimental results. The results show that the proposed model is capable of predicting failure times of the component made of the above-mentioned material with an accuracy of 4.0%.

关键词： elastic-creep     elastic-plastic-creep     stress triaxiality     life prediction     pressure vessels     finite element analysis (FEA)    

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Elevated temperature creep model of parallel wire strands

《结构与土木工程前沿（英文）》   页码 1060-1071 doi: 10.1007/s11709-023-0981-y

摘要： Parallel wire strands (PWSs), which are widely used in prestressed steel structures, are typically in high-stress states. Under fire conditions, significant creep effects occur, reducing the prestress and influencing the mechanical behavior of PWSs. As there is no existing approach to analyze their creep behavior, this study experimentally investigated the elevated temperature creep model of PWSs. A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test. It was concluded that the temperature level had a more significant effect on the creep strain than the stress level, and 450 °C was the key segment point where the creep rate varied significantly. By comparing the elevated temperature creep test results for PWSs and steel strands, it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels. The parameters in the general empirical formula, the Bailey–Norton model, and the composite time-hardening model were fitted based on the experimental results. By evaluating the accuracy and form of the models, the composite time-hardening model, which can simultaneously consider temperature, stress, and time, is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.

关键词： parallel wire strands     experimental study     elevated temperature creep model    

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Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

《结构与土木工程前沿（英文）》 2009年 第3卷 第2期   页码 234-239 doi: 10.1007/s11709-009-0020-7

摘要： This paper aims to study the different vertical displacements in tall hybrid-structures and the corresponding engineering measures. First, the method to calculate the different vertical displacements in tall hybrid-structures is presented. This method takes into account the effects of construction process by applying loads sequentially story by story. Based on the concrete creep and shrinkage calculation formula in American Concrete Institute (ACI) code, with the assumption that loads are increased linearly in members, the creep and shrinkage effects of members are analyzed by adopting two parameters named average load-aged coefficient and average age-last coefficient. The effects of steel ratio on members creep are analyzed by age-adjusted module method (AEMM). The effects that core-tube were constructed in advance to outer steel frame were also considered. Then, based on the sample calculation, the measures to effectively reduce the different vertical displacements in hybrid-structures are proposed. This method is simple and practical in the calculation of different vertical displacements in tall and super-tall hybrid-structures.

关键词： creep     shrinkage     construction process     hybrid-structure    

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Creep-fatigue crack growth behavior in GH4169 superalloy

Dianyin HU, Xiyuan WANG, Jianxing MAO, Rongqiao WANG

《机械工程前沿（英文）》 2019年 第14卷 第3期   页码 369-376 doi: 10.1007/s11465-018-0489-7

摘要： This study aims to examine the crack growth behavior of turbine disc GH4169 superalloy under creep-fatigue loading. Crack growth experiments were performed on compact tension specimens using trapezoidal waveform with dwell time at the maximum load at 650 °C. The crack growth rate of GH4169 superalloy significantly increased with dwell time. The grain boundaries oxidize during the dwell process, thereby inducing an intergranular creep-fatigue fracture mode. In addition, testing data under the same dwell time showed scattering at the crack growth rate. Consequently, a modified model based on the Saxena equation was proposed by introducing a distribution factor for the crack growth rate. Microstructural observation confirmed that the small grain size and high volume fraction of the d phase led to a fast creep-fatigue crack growth rate at 650 °C, thus indicating that two factors, namely, fine grain and presence of the d phase at the grain boundary, increased the amount of weakened interface at high temperature, in which intergranular cracks may form and propagate.

关键词： crack growth rate     creep-fatigue     GH4169 superalloy     CT specimen     dwell time    

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Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0702-6

摘要： The creep life of an aeroengine recuperator is investigated in terms of continuum damage mechanics by using finite element simulations. The effects of the manifold wall thickness and creep properties of brazing filler metal on the operating life of the recuperator are analyzed. Results show that the crack initiates from the brazing filler metal located on the outer surface of the manifold with the wall thickness of 2 mm and propagates throughout the whole region of the brazing filler metal when the creep time reaches 34900 h. The creep life of the recuperator meets the requirement of 40000 h continuous operation when the wall thickness increases to 3.5 mm, but its total weight increases by 15%. Decreasing the minimum creep strain rate with the enhancement of the creep strength of the brazing filler metal presents an obvious effect on the creep life of the recuperator. At the same stress level, the creep rupture time of the recuperator is enhanced by 13 times if the mismatch between the minimum creep rate of the filler and base metal is reduced by 20%.

关键词： creep     life assessment     brazed joint     continuum damage mechanics     aeroengine recuperator    

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A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 36-45 doi: 10.1007/s11709-014-0243-0

摘要： This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete (SCC) mix with that of a corresponding conventional concrete (CC) mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials ( / ) ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

关键词： admixture     conventional concrete (CC)     creep     fracture mechanic     mechanical Properties     self-consolidating concrete (SCC)     shrinkage    

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Experimental research on the creep behavior and bearing capacity of repeatedly prestressed concrete beam

SHAO Xudong, LI Lifeng, YANG Jianjun

《结构与土木工程前沿（英文）》 2007年 第1卷 第3期   页码 305-311 doi: 10.1007/s11709-007-0040-0

摘要： In the prestress tensioning process of medium or short span prestressed concrete beam bridges, there are always many serious problems, such as the camber of straight beam being too large, curved beam going crosswise, and columns of rigid beam bridge cracking, that can be commonly seen because of its greater additional stress in prestressing. To solve the above problems, a new concept of repeatedly prestressed bridge structure was innovatively proposed in this work. It was proved, through theoretical and experimental comparison between this new structure and the traditional prestressed structure, that the application of repeated prestressing technology can greatly improve the mechanical and deformational performance of the low height beam during construction and long-term use. Furthermore, a kind of computational formula to calculate creep strain and deformation due to repeated prestressing in terms of time was derived in this paper and the bearing capacity of this new structure has been tested. Finally, the work concludes that there is a bright application prospect for this new structure for medium and short span prestressed beam bridges to control deformations.

关键词： computational     cracking     technology     prestressed concrete     application prospect    

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Creep and recovery behaviors of magnetorheological elastomers

Weihua LI, Yang ZHOU, Tongfei TIAN, Gursel ALICI,

《机械工程前沿（英文）》 2010年 第5卷 第3期   页码 341-346 doi: 10.1007/s11465-010-0096-8

摘要： This paper presents experimental and modeling study of creep and recovery behaviors of magneto-rheological elastomers (MREs) under constant stresses. Experimental study was accomplished using a rheometer with parallel-plate geometry. Under constant stresses ranging from a small value to a large one, the resultant strains were recorded. The experimental results demonstrated that MREs behave as linear visocleastic properties. The effects of the magnetic field and stress on MRE creep behaviors were discussed. Moreover, a four-parameter viscoelastic model was developed to describe MRE creep behaviors. The comparison between the experimental results and the modeling predictions indicates that the model can predict MRE creep behaviors very well.

关键词： magneto-rheological elastomers (MREs)     creep     recovery     linear viscoelastic model    

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Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 355-362 doi: 10.1007/s11465-009-0065-2

摘要： In recent years, the need for high temperature heat exchangers to improve the efficiency of power and chemical conversion systems has been growing. However, the creep design of the high temperature compact heat exchangers has been a primary concern because the working temperature can be well above the creep limit of the materials. To establish the high temperature design criterion for compact heat exchangers, creep behavior of the plate-fin structures and brazed joints are investigated in this paper. The time-dependent deformation and bending stress of the plate-fin structures are obtained analytically by simplifying the fins to elastic springs. The creep damage evolution inside the brazed joint is studied by coupling the finite element method with a damage constitutive equation. The significant effect of creep property mismatch in the brazed joint on the creep strength is demonstrated.

关键词： compact heat exchanger     creep     damage     brazing joint    

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钢管混凝土劲性骨架拱桥收缩徐变影响理论研究

谢肖礼,秦荣,彭文立,邓志恒

《中国工程科学》 2001年 第3卷 第3期   页码 80-84

摘要：

采用混凝土徐变理论、变形协调、中值理论及平衡条件，并考虑混凝土的弹性后效及受四周约束作用的徐变特性，导出了混凝土徐变、收缩引起的截面应力重分布的表达式。公式简单，应用方便，并对万县长江大桥收缩、徐变模型试验进行分析，所得结果与模型试验较为吻合，同时指出了影响该桥型应力的主要因素。

关键词： 钢管混凝土劲性骨架     收缩徐变     初应力     应力重分布    

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Influence of pressure and density on the rheological properties of rockfills

Erich BAUER, Zhongzhi FU, Sihong LIU

《结构与土木工程前沿（英文）》 2012年 第6卷 第1期   页码 25-34 doi: 10.1007/s11709-012-0143-0

摘要： Long-term deformations of rockfill dams can be related to the type of dam, the pre-compaction achieved during the construction of the dam, the history of loading events, the rheological properties of the rockfill material used, the seepage behavior caused by defects of the sealing, the interactions of the dam building with the foundation, and the hydrothermal phenomena of the stressed rockfill material. The present paper investigates the rheological properties of coarse grained rockfill materials using a hypoplastic constitutive model. Particular attention is paid to wetting deformation under different deviatoric loading states and pre-compactions. To quantify the state of weathering a so-called “solid hardness” is used in the sense of a continuum description. It is shown that an appropriate modeling of wetting deformations requires a unified description of the interaction at least between the state of weathering, the stress state, the density and the rate of deformation. The results obtained from the numerical simulations are compared with available experimental data for a rockfill material used in Xiaolangdi earth dam.

关键词： rockfills     solid hardness     wetting deformation     hypoplasticity     creep    

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武广客运专线32 m箱梁预应力效果监测及徐变上拱的控制措施

宋津喜

《中国工程科学》 2009年 第11卷 第1期   页码 60-66

摘要：

采用现场实测的方法对武广客运专线工程32 m预应力混凝土箱梁应力效果进行监测，并采用Midas/Civil结构分析程序进行了弹性上拱的理论分析，提出箱梁徐变上拱的控制措施，为同类工程提供借鉴及经验。

关键词： 武广客运专线     32 m箱梁     预应力效果监测     徐变上拱控制    

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Grade 91钢抗蠕变性能的计算热力学研究 Article

Andrew Smith, Mohammad Asadikiya, Mei Yang, Jiuhua Chen, Yu Zhong

《工程（英文）》 2020年 第6卷 第6期   页码 644-652 doi: 10.1016/j.eng.2019.12.004

摘要：

本研究旨在了解在焊接Grade 91（Gr.91）钢时，热影响区（HAZ）内不同的临界温度与第二相的稳定性之间的关系。IV型开裂出现在Gr.91钢的焊接热影响区。先前的研究表明，Gr.91钢的开裂失效与其抗蠕变性能有关，而Gr.91钢中第二相的稳定性对其抗蠕变性能有着举足轻重的影响。本研究运用计算热力学方法预测了Gr.91钢中的第二相，即M23C6相、MX相和Z相的稳定性。平衡凝固和Scheil凝固模拟方法分别被用于研究Gr.91钢在焊接过程中的相稳定性。本文讨论了四个不同临界温度，即Ac1（加热时奥氏体开始生成的温度）、Ac3（加热时奥氏体转变的终了温度）、M23C6相及Z相的阈值温度对热影响区的厚度和相稳定性的影响。本研究的模拟结果解释了Gr.91钢抗蠕变性能的影响机理，并为如何通过优化钢的成分、焊接和热处理工艺参数提高钢的高温抗蠕变性能提供了一种可行的解决方案。同时，本工作的模拟结果为新型合金的研发，即通过提高钢的抗蠕变性能来防止IV型开裂提供了指导。

关键词： Grade 91钢     抗蠕变性能     铁素体-马素体钢     焊缝组织     计算热力学     第二相     合金成分    

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Long-term behavior and safety assessment of Sance Rockfill Dam

Marta DOLEZALOVA, Ivo HLADIK

《结构与土木工程前沿（英文）》 2011年 第5卷 第1期   页码 79-89 doi: 10.1007/s11709-010-0010-9

摘要： Safety assessment of the 62 m high Sance Rockfill Dam based on long-term monitoring results and their simulation by numerical models is presented in the paper. Unexpectedly large settlements and horizontal movements of the crest together with the steep downstream slope questioned the safety of the dam. Calibrated 2D and 3D models fitting the monitoring results were applied for the safety assessment of the dam including slope stability analysis and estimation of the clay core cracking and hydraulic fracturing hazard. The modeling results contributed to the rehabilitation concept and project of the dam.

关键词： rockfill dam     path dependence     creep     calibration     cracking     hydraulic fracturing hazard    

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标题 作者 时间 类型 操作

Finite element analysis of creep for plane steel frames in fire

Hui ZHU, Yuching WU

期刊论文

A model for creep life prediction of thin tube using strain energy density as a function of stress triaxialityunder quasi-static loading employing elastic-creep & elastic-plastic-creep deformation

Tahir MAHMOOD, Sangarapillai KANAPATHIPILLAI, Mahiuddin CHOWDHURY

期刊论文

Elevated temperature creep model of parallel wire strands

期刊论文

Effect of concrete creep and shrinkage on tall hybrid-structures and its countermeasures

Pusheng SHEN, Hui FANG, Xinhong XIA

期刊论文

Creep-fatigue crack growth behavior in GH4169 superalloy

Dianyin HU, Xiyuan WANG, Jianxing MAO, Rongqiao WANG

期刊论文

Creep life assessment of aero-engine recuperator based on continuum damage mechanics approach

期刊论文

A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

期刊论文

Experimental research on the creep behavior and bearing capacity of repeatedly prestressed concrete beam

SHAO Xudong, LI Lifeng, YANG Jianjun

期刊论文

Creep and recovery behaviors of magnetorheological elastomers

Weihua LI, Yang ZHOU, Tongfei TIAN, Gursel ALICI,

期刊论文

Creep of brazed plate-fin structures in high temperature compact heat exchangers

Shantung TU, Guoyan ZHOU

期刊论文

钢管混凝土劲性骨架拱桥收缩徐变影响理论研究

谢肖礼,秦荣,彭文立,邓志恒

期刊论文

Influence of pressure and density on the rheological properties of rockfills

Erich BAUER, Zhongzhi FU, Sihong LIU

期刊论文

武广客运专线32 m箱梁预应力效果监测及徐变上拱的控制措施

宋津喜

期刊论文

Grade 91钢抗蠕变性能的计算热力学研究

Andrew Smith, Mohammad Asadikiya, Mei Yang, Jiuhua Chen, Yu Zhong

期刊论文

Long-term behavior and safety assessment of Sance Rockfill Dam

Marta DOLEZALOVA, Ivo HLADIK

期刊论文