共查询到20条相似文献,搜索用时 15 毫秒
1.
Conventional heat transfer analysis for the prediction of fire-induced damage in a tunnel is performed without consideration of the spalling and dehydration of concrete, meaning that the fire-induced damage of concrete may be underestimated. This study proposes a new model that is able to simulate structural loss during a fire by eliminating the elements exceeding a pre-determined critical temperature in a finite element analysis. The important parameters for the application of the proposed element elimination model include the critical temperature chosen as the element elimination criterion and the changes of the combined heat transfer coefficients, which are dependent on element size and the time–temperature history during a fire, respectively. These parameters are derived from a series of parametric studies based on real fire experiments using a high-temperature furnace. In order to verify the applicability of thermo-mechanical coupling analysis using the proposed model, the fire-induced damage of an unreinforced concrete tunnel lining was estimated with a focus on the spalling depth, temperature distribution, and equivalent stress in the remaining part of the concrete lining under RABT and RWS fire scenarios. 相似文献
2.
三面受火钢筋混凝土梁温度场非线性分析 总被引:5,自引:3,他引:5
根据三面受火钢筋混凝土梁离散体积单元的能量守恒原理,建立了有限差分平衡方程,在合理确定混凝土热工参数基础上,采用增大混凝土质量热容的方法,考虑混凝土中自由水与结合水的物理化学反应对混凝土温度场的影响。通过编制三面受火钢筋混凝土梁截面温度场非线性有限差分程序,并结合火灾情况下钢筋混凝土梁温度场的试验结果,合理地确定了混凝土质量热容放大系数和混凝土表面换热系数的计算式。结果表明:三面受火钢筋混凝土梁温度场的计算结果与试验结果符合较好,为进一步研究火灾情况下钢筋混凝土梁力学性能和耐火极限提供了条件。 相似文献
3.
4.
5.
6.
Nowadays, performance-based design methods are increasingly used for fire resistance assessment of structures. To implement these methods, it is paramount to determine the temperature development within a structural member exposed to fire as accurately and efficiently as possible. Numerical models are developed in this paper to simulate the temperature development in concrete-filled carbon and stainless steel tubes. It was found that the influence of the moisture content in concrete and the thermal contact conductance at the steel–concrete interface is significant. New models for thermal conductivity of concrete and thermal contact conductance at the interface are proposed in this paper. Comparisons of temperature development are made between numerical simulations and extensive experimental results. Improved agreement with test results is achieved when the proposed models are used in the heat transfer analysis. 相似文献
7.
为分析钢筋混凝土梁在火灾过程中的温度分布、结构变形非线性变化过程,在三组不同条件下对火灾后钢筋混凝土梁构件内部传热及变形过程进行全过程仿真。基于钢筋混凝土热工特性、温度-应变-应力本构特性,分析钢筋混凝土梁在受火时的温度分布演化过程,以及配筋率、初始载荷和受火时间等参数对钢筋混凝土梁防火承载力的影响。结果表明:火灾中材料强度的降低,自重和初始载荷以及不均匀升温引起的内部应力共同作用引起了构件的整体失稳。初始载荷对梁剩余承载力的影响不大,提高混凝土中钢筋数量能有效地提高钢筋混凝土梁的防火承载力。 相似文献
8.
9.
10.
地下压气储能圆形内衬洞室内压和温度引起应力计算 总被引:1,自引:0,他引:1
地下压气储能岩石内衬洞室内,不断变化的气体内压和温度引起的应力场是关乎洞室稳定性、耐久性的重要因素,由此提出了一种计算气压和温度引起应力变化的解析方法。将内衬洞室考虑成由密封层、衬砌和围岩组成,首先建立了洞室温度和气压求解的控制方程;利用拉普拉斯变换和叠加原理得到每个循环内洞室温度和气压随时间的变化;采用热弹性模型得到内压和温度引起的应力场。基于解析方法,给出了典型循环周期内洞室应力变化情况;接着通过一个热-力以及洞室气体耦合求解的数值模型以及不考虑密封层和衬砌的温度场解析方法来验证本文方法;最终探讨了温度对总应力的影响程度,以及不同换热系数的影响。结果表明:本文方法是可行的;温度和内压引起的密封层和衬砌内环向拉应力非常大;温度对于压气储能洞室有着不可忽略的作用,温度对于环向和纵向应力的影响程度要大于对径向应力的影响;换热系数对应力变化影响很大。 相似文献
11.
为在建筑结构设计时考虑地震引发火灾对建筑结构的作用和影响,提出建筑结构地震火灾效应分析计算方法,此方法结合结构地震反应分析与火灾热力反应分析,通过简化的建筑结构地震损伤模型,考虑地震损伤的同时,连接结构的热传导分析与热力分析,从而实现地震火灾效应计算.运用此方法对一单层和一多层混凝土框架分别进行了分析,并与没有考虑地震... 相似文献
12.
13.
本文根据某污水处理厂蛋形消化池火灾过程,建立热传导数学模型。对火场持续时间、火场温度、混凝土的热容、混凝土的热导率、大气温度、混凝土表面热交换强度等参量进行合理取值,进行计算分析,得到不同深度、不同时刻混凝土的温度场。根据混凝土、钢筋和预应力钢绞线在不同持荷条件下的化学稳定性、热力学特性,实现蛋形消化池钢筋混凝土预应力结构的火灾损伤定量分析,为蛋形消化池的火灾结构安全鉴定提供理论依据。 相似文献
14.
J. Ding 《Journal of Constructional Steel Research》2008,64(10):1086-1102
This paper employs the commercial finite element analysis package ANSYS to model the thermal and structural behaviour of isolated CFT columns in fire. Although CFT columns have been numerically analysed by many researchers, this paper presents details of a number of features which have often been neglected by many researchers, including the influence of an air gap and slip at the steel/concrete interface on CFT column temperatures and structural behaviour, the sensitivity of CFT fire resistance to concrete tensile behaviour and CFT column initial imperfections. The finite element model is validated by comparing the simulation results against experimental results of standard fire resistance tests on 34 CFT columns with different structural boundary and loading conditions. A numerical parametric study is then performed to investigate the sensitivity of simulation results to different assumptions introduced in the finite element model. The results of these numerical studies show that whether or not including slip between the steel tube and concrete core in the numerical model has minor influence on the calculated column fire resistance time. The fire resistance of CFT columns with an air gap is generally slightly higher than that without an air gap. However, including slip gives a better prediction of column deflection behaviour. Using different tensile strength or tangent stiffness of concrete has a minor effect on the calculated column fire resistance. Different amounts of column initial deflection have some influence on column fire resistance times. Nevertheless, the influence is relatively small so that it is acceptable to use a maximum initial deflection of L/1000 as commonly assumed by other researchers. 相似文献
15.
16.
Yanmin YANG Ying XIONG Yongqing LI Xiangkun MENG Peng WANG Tianyuan CAI 《Frontiers of Structural and Civil Engineering》2022,16(10):1351
In this study, fire tests of four single-section scaled-down utility tunnels were conducted. By analyzing temperature and structural responses of the utility tunnel throughout the fire exposure, the effects on the fire behavior of two different construction methods, cast-in-situ and prefabricated, and of two different materials, ordinary concrete and full lightweight concrete, were explored. The results of the study showed that the shear failure of the cast-in-situ utility tunnel occurred at the end of the top or bottom plate, and the failure of the prefabricated utility tunnel occurred at the junction of the prefabricated member and post-cast concrete. As the temperature increased, the temperature gradient along the thickness direction of the tunnel became apparent. The maximum temperature difference between the inner and outer wall surfaces was 531.7 °C. The highest temperature occurred in the cooling stage after stopping the heating, which provided a reference for the fire protection design and rescue of the utility tunnel. The displacement of the top plate of the prefabricated utility tunnel was 16.8 mm, which was 41.8% larger than that of the cast-in-situ utility tunnel. The bearing capacities of the ordinary concrete utility tunnel and full lightweight concrete utility tunnel after the fire loss were 27% and 16.8%, respectively. The full lightweight concrete utility tunnel exhibited good ductility and fire resistance and high collapse resistance. 相似文献
17.
截面温度不均匀钢柱火灾下将发生热弯曲及扭转屈曲破坏,同时对热变形的约束导致钢柱内在升温阶段产生附加压力,在降温阶段出现附加拉力。分别考虑3种约束刚度比和3种截面温度分布形式,进行了9根受约束钢柱的抗火试验,量测了受约束钢柱达到最大轴力时的温度(屈曲温度)、轴力恢复至初始荷载对应的温度(临界温度)及破坏温度,研究其在火灾升温和降温阶段的受力性能、破坏特征。试验结果表明,截面温度不均匀导致钢柱在绕截面对称轴弯曲时同时发生扭转;约束刚度比越大,钢柱的屈曲温度越低,破坏温度与屈曲温度之差越大;截面温差越大,钢柱屈曲温度和破坏温度越高。同时对试验钢柱进行了有限元分析,分析结果与试验结果基本一致,验证了所建立的有限元分析模型的正确性。 相似文献
18.
High-strength concrete-filled steel tube (CFST) columns offer a number of benefits and are widely used in high-rise building construction. This paper presents a brand new thermal modeling approach in comparison with tremendous test data for the heat transfer analysis. A heat transfer model has been developed to predict the thermal response of high-strength CFST columns under standard fire conditions with consideration of a number of parameters: steel and furnace emissivity, thermal interface conductance and concrete strength. The verified numerical models discussed the variation of emissivity of steel surfaces and thermal interface conductance in fire. It can be concluded that the influence of emissivity and thermal interface conductance is considerable in the numerical analysis. It is also demonstrated that thermal behavior of high-strength CFST columns subjected to fire during heating and cooling stages, and providing the guidance on predicting thermal response of high-strength concrete-filled steel tube columns. 相似文献
19.
混凝土结构对流换热效应的研究 总被引:1,自引:0,他引:1
综合分析了国内外学者对混凝土对流换热系数的研究成果,结合风洞实验,提出了混凝土对流换热系数计算公式,可用于混凝土结构温度效应分析。并利用有限元程序进行预应力混凝土简支箱梁的温度效应分析,计算中采用了标准化的太阳日辐射强度曲线和日气温变化曲线,以梁的跨中挠度和轴向变形的变化规律为例,讨论了对流换热系数取值对结构温度效应的影响。 相似文献
20.
Thermal properties of fire insulation namely thermal conductivity, specific heat, thermal strain and mass loss play a critical role in determining the effectiveness of these materials to improve fire resistance of steel structural members. These properties vary with temperature and are predominantly governed by moisture content and chemical constituents. This paper presents the effect of temperature on thermal properties of different types of spray applied fire resistive materials (SFRM). High temperature property tests were carried out on three types of commercially available SFRM to measure thermal conductivity, specific heat, mass loss and thermal strain in the range of 20–1000 °C. Data from these tests show that temperature has significant influence on thermal conductivity, thermal expansion and mass loss of fire insulation. The measured test data are utilized to develop thermal property relationships for fire insulation in terms of temperature. The proposed relations can be used as input data in thermo-mechanical analysis for evaluating fire resistance of steel structures. 相似文献