Investigation of insulated FRP-wrapped reinforced concrete columns in fire

Research has demonstrated that fibre-reinforced polymers (FRPs) can be used efficiently and safely in strengthening and rehabilitation of reinforced concrete structures. However, the use of FRPs in buildings has been limited because relatively little is known about the behaviour in fire of reinforced concrete structural members that have been strengthened with FRP systems. This paper presents the recent results of an ongoing experimental study of the fire performance of FRP-wrapped reinforced concrete circular columns. The results of fire tests on two columns are presented, one of which was tested without supplemental fire protection, and one of which was protected by a supplemental fire protection system applied to the exterior of the FRP-strengthening system. The primary objective of these tests was to compare the fire behaviour of the two FRP-wrapped columns and to investigate the effectiveness of the supplemental insulation system. The thermal and structural behaviour of the two columns are discussed. The results show that, although FRP systems are sensitive to high temperatures, satisfactory fire endurance ratings can be achieved for reinforced concrete columns that are strengthened with FRP systems by providing adequate supplemental fire protection. In particular, the insulated FRP-strengthened column in this study was able to resist elevated temperatures during the fire tests for at least 90 min longer than the equivalent uninsulated FRP-strengthened column.     

钢筋混凝土Z形柱的截面设计方法

根据正截面承载能力计算的基本假定,建立钢筋混凝土异形柱的基本计算公式,提出相应的设计计算方法,并和实测结果进行了比较,分析表明,计算值和实测值吻合良好.     

硅烷膏体浸渍剂在保护混凝土中的实际应用

渗透型有机硅成功用于保护混凝土在国外已有数十年的历史。用于保护钢筋混凝土,它可防止水分及氯离子的渗透,从而对于防止混凝土的腐蚀与破坏起到关键的作用。这种浸渍剂一般都由硅烷或硅氧烷组成。通常情况下,由于这些低粘度的液体非常容易挥发。尤其在桥梁底面及立面施工时,有效成分大量流失。为了避免出现这种情况,德国瓦克化学有限公司成功开发了一种新型的硅烷乳膏状产品。这种材料施工简单,只需一步完成,具有很高的遮盖率,由于不流淌,活性组分不会损失。与混凝土表面接触时间长,保证了在高等级混凝土中的渗透深度,而且在其表面不会残留任何痕迹。     

Advanced model for predicting the fire response of concrete filled tubular columns

In this work, a nonlinear finite element three-dimensional model is presented and validated in order to study the behaviour of axially loaded concrete filled tubular (CFT) columns with circular cross-section exposed to fire. A realistic sequentially coupled nonlinear thermal-stress analysis is conducted for a series of columns available in the literature. The model is validated by comparing the simulation results with the real fire resistance tests. By means of this model, and extensive sensitivity analysis is performed over a wide range of aspects concerning the finite element modelling of the problem under study, including new key factors not studied previously. Based on this sensitivity analysis several modelling recommendations are given in this paper, which will be useful for future research work. The validated numerical model is furthermore employed to study and discuss the Eurocode 4 Part 1–2 simple calculation model, which is deeply analysed in this paper.     

硅烷浸渍剂对混凝土保护作用的研究

本文系统进行了不同品种硅烷浸渍剂对普通混凝土和高性能混凝土的保护性能研究。探讨了不同品种硅烷浸渍剂、不同硅烷浓度等对混凝土保护性能的影响规律。试验结果表明：试验中所采用的未经稀释的硅烷浸渍剂都能对混凝土有很好的保护效果,粘附性能好的膏体硅烷浸渍剂在混凝土中的保护效果最为突出。     

火灾后钢筋混凝土结构火灾温度的判断方法

对火灾后钢筋混凝土结构火灾温度的现行判断方法进行了论述,并说明了各种方法的具体使用,以准确判断火灾后钢筋混凝土结构火灾温度,从而为判断火灾后混凝土结构损伤程度和进行结构修复提供依据。     

混凝土表面保护用喷涂聚脲徐料的研制与应用

介绍了混凝土保护用聚脲涂料的研制情况:对混凝土封闭底漆的匹配性以及聚脲配方进行了研究和设计,有效地提高了聚脲涂层与混凝土基材的附着力;总结了聚脲涂料在混凝土表面的施工工艺.     

Repair of fire damaged circular reinforced concrete columns with FRP composites

An experimental study was undertaken to investigate the axial capacity of post-heated circular reinforced concrete columns repaired with glass and carbon fibre reinforced polymers. The series of tests comprised columns which were un-heated, post-heated, post-heated seriously spalled and repaired with mortar, post-heated and wrapped with either glass or carbon fibre reinforced polymer, and post-heated seriously spalled and repaired with both mortar and either glass or carbon FRP. The post-heated columns were repaired with unidirectional glass and carbon fibre reinforced polymer jackets. All columns were tested under axial compression to determine their ultimate axial strength, stiffness and ductility. The results indicated that repairing heat damaged circular columns with a single layer of unidirectional glass or carbon fibre reinforced polymer has a significant effect on the axial strength and the ductility of circular columns. It was shown that the load-carrying capacity of post-heated columns can be restored up to the original level or greater than those of un-heated columns. However, it was shown that the effect of a single layer of glass or carbon fibre reinforced polymer on the axial stiffness was not significant.     

火灾下玻化微珠保温混凝土柱耐火分析

玻化微珠保温混凝土新形势下提出的一种新型建筑材料,可以同时满足建筑保温和结构承重性能的要求。通过试验,对常温及100~700℃高温后玻化微珠保温混凝土导热系数进行比较,在此基础上得出高温下玻化微珠保温混凝土导热系数推算计算式,为高温下玻化微珠保温混凝土热工性能研究提供理论依据。运用ANSYS对玻化微珠保温混凝土柱在三面受火的情况下进行热分析,得出此时柱截面及钢筋的温度分布规律,为火灾后混凝土柱的检测与加固提供依据。     

Effect of transient creep on the behaviour of reinforced concrete columns in fire

Concrete experiences transient creep when subjected to elevated temperatures, which is believed to be the result of thermo-mechanical interactions within the cement paste microstructure. Transient creep occurs in compression under first time heating. Although it is particularly relevant to the behaviour of columns, which most of the time are under a state of compression, its systematic effects on their performance and stability under fire have not been well elucidated. Indeed, current design of reinforced concrete columns is based at worst on tabulated data, which bear no resemblance to real fires, or at best, on codes of practice that consider transient creep through the deformation properties of concrete. Using a previously developed finite element code, which is capable of considering transient creep either explicitly as an additional strain rate component, or implicitly through the deformation properties of concrete, a systematic study of its effects on the behaviour of an unrestrained column is presented. It was found that transient creep gives rise to additional compressive stresses in the column magnifying any bending moments, and therefore precipitating its failure.     

型钢混凝土柱的耐火设计方法

型钢混凝土(SRC)柱已经较多地应用于我国的高层和超高层建筑中,但我国防火规范尚未有SRC柱的耐火设计规定。在分析SRC柱在火灾下的温度场分布和耐火性能的基础上,给出了SRC柱的耐火极限表,并建议了相关防火保护措施,可为相关规范的修订提供参考。     

沥青混凝土路面施工方法

通过对新疆S223线石河子至151团改建工程中沥青混凝土路面施工经验的总结。阐述了沥青混凝土路面的施工技术，以对沥青路面从经验探索阶段向施工技术逐渐完善阶段的发展起到一定促进作用。     

FE modelling and fire resistance design of concrete filled double skin tubular columns

Concrete filled double skin tubular columns (CFDST) have excellent structural behaviour. They have been used as transmission towers and have potential to be used as building columns and bridge piers. Performance of the CFDST columns under ambient temperature has been well studied, whereas fire resistance of such columns is still a major concern. A summary of a series of fire tests on CFDST columns conducted by the authors is briefly presented in the paper. A finite element numerical model is developed to analyse the fire behaviour of CFDST columns, namely thermal and structural responses under fire exposure. The model is verified by the test results and then used to perform parametric analyses. Parameters which have significant effect on the fire behaviour of CFDST columns are identified. Based on the parametric studies, suggestions on the fire resistance design of such columns are made. Practical design tables are derived for the fire resistance design of some typical CFDST columns.     

钢筋混凝土梁与钢骨柱节点连接施工技术

以山西体育中心运动员训练A馆工程为例,对钢筋混凝土梁与钢骨柱节点连接技术进行了介绍,分别阐述了节点连接的工艺原理,关键技术及施工工艺等内容,以指导相关施工人员合理解决钢骨混凝土梁柱节点处钢筋的贯通问题。     

Realistic modelling of thermal and structural behaviour of unprotected concrete filled tubular columns in fire

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.     

钢筋混凝土底框架商住楼耐火设计审核与火灾扑救

钢筋混凝土底框架商住楼建筑的下部火灾荷载和上部实际重力荷载均较大，在火灾中可能会引起倒塌。以某商住楼火灾倒塌事故为例，依据室内火灾发展规律和结构耐火理论，对此类建筑的耐火设计审核与火灾扑救战术提出建议。     

某体育场预应力钢管砼斜拉柱施工

本文介绍了某体育场斜拉柱预应力钢-混凝土组合结构的施工技术,积累了宝贵的施工经验,为今后类似工程提供借鉴.     

火灾后钢骨超高强混凝土柱抗震性能的研究

从高温后钢材及混凝土力学性能、高强混凝土材料力学性能、火灾后的钢骨混凝土柱力学性能3个方面进行了论述,介绍了目前国内外钢骨超高强混凝土结构抗火研究的主要进展及成果。     

混凝土异形柱抗震墙设计方法

针对组合结构的有限元分析方法虽然比较精确,但往往存在计算速度与计算精度之间的矛盾,尤其是计算包含不同构件的结构体系这一点,经过对模型进行模态分析和拟动力试验,提出了＂等效剪力墙＂的设计方法,实践证明：此法不但简单而且对异形柱组合结构抗震设计是偏于安全的。