碳纤维加固混凝土构件防火保护措施的试验研究

通过对10块分别采用厚型防火涂料、薄型防火涂料及普通水泥砂浆进行防火保护的混凝土板火灾试验,得出采用不同涂层厚度的3种防火保护措施后在标准火灾试验下混凝土板的温度场分布情况。结果表明:对于碳纤维加固混凝土构件,采用薄型防火涂料及普通水泥砂浆进行防火保护的作用不大,可以采用厚型防火涂料进行保护,同时得出了厚型防火涂料厚度的计算公式。     

粘贴法加固混凝土构件的防火试验研究

试验研究分析了涂不同厚度防火涂料的粘贴法加固混凝土试件在火灾下的耐火极限。试验结果表明,碳纤维布和钢板对试件温度场的影响是相同的,厚涂型钢结构防火涂料对混凝土结构的防火作用明显,防火涂料厚度与防火性能并不成正比。试验确定粘贴法加固混凝土构件防火涂层厚度的最佳取值为40mm。     

CFRP加固钢筋混凝土板耐火性能的试验研究

对3块CFRP加固钢筋混凝土板进行火灾试验,分析了破坏形态、截面温度场和挠度。结果表明:(1)无机胶粘贴CFRP加固混凝土板的耐火极限约为22min;(2)涂有防火涂料加固板的截面温度比无防火涂料的小;(3)同等防火保护下无机胶粘贴CFRP加固混凝土板的截面温度比有机胶的小很多;(4)火灾下CFRP的失效有一定突然性;(5)有防火保护的无机胶粘贴CFRP加固混凝土板耐火性能良好,暴露火灾中90min仍有良好的加固性能。     

碳纤维布加固钢筋混凝土板的耐火极限分析

编制了碳纤维布加固钢筋混凝土板的高温全过程分析程序,程序的有效性得到了试验结果的初步验证。针对不同构件尺寸、防火涂料厚度、受拉纵筋配筋率、碳纤维布加固量、混凝土保护层厚度、荷载比等共计6400种工况,进行了碳纤维布加固钢筋混凝土板的高温反应分析,考察了各主要参数对该类加固构件耐火极限的影响规律。在此基础上,建立了该类加固构件耐火极限的实用计算方法。研究结果表明：高温下碳纤维布加固钢筋混凝土板的耐火极限随板的厚度、防火涂料厚度和混凝土保护层厚度的增加逐渐增大,而随碳纤维布加固量和荷载比的增加逐渐减小;其中荷载比的影响最为显著,受拉纵筋配筋率对该类加固构件的耐火极限影响较小。     

碳纤维布抗弯加固钢筋混凝土梁的耐火极限分析

编制了碳纤维布抗弯加固钢筋混凝土梁的温度场计算程序和耐火极限分析程序,通过数值分析结果与试验结果的对比,初步验证了程序的有效性。利用上述程序,针对高温下加固梁的受弯破坏形态,就不同构件跨高比、防火涂料厚度、受拉纵筋配筋率、碳纤维布加固量、混凝土保护层厚度、荷载比等共计1728种工况进行了大量计算分析,同时考察了各参数对加固梁耐火极限的影响规律。在此基础上,建立了加固梁的耐火极限简化预测方法。研究结果表明,加固梁的耐火极限随防火涂料厚度、混凝土保护层厚度和受拉纵筋配筋率的增加而逐渐增大,同时随荷载比、碳纤维布加固量和跨高比的增加而逐渐减小,其中荷载比的影响最为显著。     

碳纤维布加固混凝土梁的温度场实用计算方法

编制了三面受火且设有防火保护层的碳纤维布加固混凝土梁的截面温度场计算程序,通过算例验证了程序的正确性。利用该程序,分析了防火材料类型及厚度、保护方式、截面尺寸对加固梁截面温度分布的影响。基于数值分析结果,提出了加固梁截面温度场的实用计算方法。研究结果表明：①除梁侧防火材料末端附近产生温度突变外,小U型防火保护方式下加固梁的截面温度分布总体上与底面防火保护方式下类似;②随着受火时间增加,梁底温度在底面防火材料的保护下虽然上升相对较缓,但也很快达到环氧类胶粘剂的失效温度;③与厚度相同的厚型钢结构防火涂料相比,水泥砂浆的防火保护效果明显偏弱。     

第六章 钢管混凝土的防火

简要地介绍了钢管混凝土的耐火性能,分析了影响耐火度的因素以及用有限差分法计算火灾时的构件截面的温度场、构件的临界温度和临界时间、防火涂层厚度的结果。     

某化纤厂房火灾后的鉴定及加固处理

介绍某化纤厂火灾后检测的方法和内容,包括构件的截面几何尺寸、混凝土强度、钢筋强度、混凝土碳化深度等。根据检测结果和计算分析,对火灾后受损结构进行了安全性鉴定。并根据具体构件的鉴定结果,提出与之相适应的加固维修方案。对受损柱,分别采用增大截面、外包钢和外贴碳纤维的方法加固处理;对受损梁,分别采用拆除置换、外包钢和外贴碳纤维的处理方法;对受损板,分别采用拆除置换、板底植筋外加喷射混凝土和外贴碳纤维的处理方法。按照该方案加固后的厂房结构完全能够满足正常使用要求。     

混凝土组合构件耐火性能试验研究

利用自行设计的火灾燃烧炉对混凝土T型组合构件的耐火性能进行试验研究。试验持续120 min,观察火灾后构件表观现象并测量火灾过程中组合构件内部温度变化,得到火灾下混凝土板、墙组合构件的内部温度场分布规律及其高温损伤情况。结果表明：火灾下组合构件墙体受火面位置处更容易出现混凝土剥落现象,应在该位置处采取施作防火涂料等防火措施来减轻火灾高温的影响;组合构件节点核心区的混凝土温度低于其他受火区域的温度,墙板对节点核心区有一定的保护作用;火灾作用下距离混凝土组合构件受火表面越远,其内部温度越低,且其温度开始上升的反应时间越长;组合构件在非受火区域温度整体较低,温度升高的反应时间较长且速度较慢,火灾高温对非受火区域的结构影响较小。     

碳纤维在火灾后混凝土构件加固中的应用

碳纤维加固技术是火灾后混凝土构件加固的有效措施之一。介绍了碳纤维加固技术的优点、施工方法,并结合工程实例说明该方法的有效性。     

Experimental evaluation of the fire behaviour of insulated fibre-reinforced-polymer-strengthened reinforced concrete columns

In recent years, there has been an increase in the use of fibre reinforced polymer (FRP) materials for strengthening of concrete structures. However, since FRP materials are combustible, and because they are typically applied to the exterior of structural members in these strengthening applications, concerns exist regarding the behaviour of such FRP strengthening systems in fire. There is currently little information available on the fire endurance of FRP-strengthened concrete systems. This paper presents results from full-scale fire resistance experiments on three insulated FRP-strengthened reinforced concrete (RC) columns. A comparison is made between the fire performances of FRP-strengthened RC columns and conventional unstrengthened RC columns tested previously. Data obtained during the experiments is used to show that the fire behaviour of FRP-wrapped concrete columns incorporating appropriate fire protection systems is as good as that of unstrengthened RC columns. Thus, satisfactory fire resistance ratings for FRP-wrapped concrete columns can be obtained by properly incorporating appropriate fire protection measures into the overall FRP-strengthened structural system. Fire endurance criteria and preliminary design recommendations for fire safety of FRP-strengthened RC columns are briefly discussed.     

FRP加强R/C梁防火性能调查研究

对纤维加强聚合物(FRP)材料加强钢筋混凝土梁在火灾中的防火性能进行了研究。试验结果显示,防火材料能够帮助构件达到标准防火性能,同时对不断增长的FRP应用也很重要。介绍了不同文献对FRP在高温下的性能所做的研究以及目前标准对建筑构件的耐火极限要求。对两个大型试验进行了介绍。试验材料为混凝土梁构件,外部用FRP板加强,并且三分之二用专利耐火隔热材料保护。给出了试验结果,并重点强调了曝火状态下所测得的构件温度。试验数据验证了热传导数值模型,该模型可用于预测加强并绝缘钢筋混凝土梁构件内的温度。试验结果和模型数据显示,正确设计和进行绝缘保护的FRP加强梁构件耐火极限能够达到4h或者以上。     

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.     

混凝土骨料种类和边界条件对截面温度场的影响

为了正确分析钢筋混凝土构件截面温度场,以矩形柱为对象,以标准火作用为受火条件,采用数值计算方法,研究混凝土骨料种类和边界条件对截面温度场的影响。研究结果表明:因热参数差别较大,硅骨料构件截面温度明显高于碳骨料,而法国规范推荐混凝土的温度接近硅骨料混凝土的温度,温度值越高其间差别越小;是否考虑边界单元格热储存对温度场影响不大。     

Performance of insulated FRP-strengthened concrete flexural members under fire conditions

This paper presents the results of fire resistance tests on carbon fiber-reinforced polymer (CFRP) strengthened concrete flexural members, i.e., T-beams and slabs. The strengthened members were protected with fire insulation and tested under the combined effects of thermal and structural loading. The variables considered in the tests include the applied load level, extent of strengthening, and thickness of the fire insulation applied to the beams and slabs. Furthermore, a previously developed numerical model was validated against the data generated from the fire tests; subsequently, it was utilized to undertake a case study. Results from fire tests and numerical studies indicate that owing to the protection provided by the fire insulation, the insulated CFRP-strengthened beams and slabs can withstand four and three hours of standard fire exposure, respectively, under service load conditions. The insulation layer impedes the temperature rise in the member; therefore, the CFRP–concrete composite action remains active for a longer duration and the steel reinforcement temperature remains below 400°C, which in turn enhances the capacity of the beams and slabs.     

A simplified approach for predicting temperatures in insulated RC members exposed to standard fire

Fire resistance of concrete structural members can be enhanced through the application of external fire insulation on the surfaces of concrete member. For evaluating fire resistance of such insulated RC members, temperatures in concrete and steel reinforcement are to be known. This paper develops a simplified approach for predicting cross-sectional temperatures in an insulated RC structural member exposed to standard fire. The approach is derived by replacing the insulation layer into an equivalent concrete thickness layer and then undertaking statistical regression analysis on temperature data of modified concrete section. The effect of critical parameters, including geometry of concrete member and insulation, thermal properties of concrete and fire insulation, and duration of fire exposure is accounted for in temperature equations. The validity of the approach is established by comparing predictions from the proposed equation with data generated from fire tests and finite element analysis. These comparisons show the proposed equation gives reasonable prediction of temperatures, within a range of ±10%, in insulated concrete members. The applicability of the proposed approach in design situations is illustrated though a numerical example. The simplicity of the proposed method makes it attractive for use in design situations and for incorporation in design manuals.     

约束混凝土柱性能研究与进展

FRP约束混凝土柱和钢管混凝土柱是两种不同的约束混凝土应用形式。研究表明,对混凝土进行约束,可以明显提高其承载力和延性。钢管混凝土柱破坏前有较大的变形,属延性破坏;FRP约束混凝土柱的破坏具有突然性,但其强度提高的幅度较大。本文对这两种约束混凝土柱的受力性能进行了简要的比较,并总结了FRP约束混凝土柱和钢管混凝土柱研究现状,同时对今后的发展应用进行展望。     

火灾后混凝土结构损伤检测与分析

文章对遭受火灾的混凝土结构建筑物的火场温度、火灾影响区域的划分、火灾时钢筋力学性能的影响、混凝土构件火灾后外观、裂缝、烧伤深度判定及受损程度进行综合评定,为科学合理地确定火灾后混凝土结构的修复加固方案提供可靠的技术资料.