钢结构防火涂料等效热传导系数的确定

针对厚型钢结构防火涂料的热工参数确定问题和膨胀型钢结构防火涂料隔热性能无合适方法评价的现状，提出了根据耐火试验检测测定构件升温过程确定防火涂料等效热传导系数的方法。并分别利用厚型防火涂料和膨胀型防火涂料的检测结果进行试算，取得了较满意的结果。该方法还解决了有膨胀型防火涂料保护层钢构件的温度计算问题，为该类钢构件的抗火计算奠定了基础，并对防火抗火性能试验检测的内容及应提交的结果提出了建议。     

钢结构防火涂料应用的若干前沿问题

简要介绍钢结构防火涂料的工作原理及分类,并对钢结构防火涂料应用的若干前沿问题进行探讨,包括非膨胀型防火涂料的破损问题、膨胀型防火涂料的老化问题和膨胀型防火涂料隔热参数的确定问题。     

非膨胀型防火涂料等效热传导系数研究

基于防火涂料标准耐火试验方法,对涂覆非膨胀型防火涂料的钢板试件和工字型钢试件进行了耐火试验,用所得的试件升温曲线计算非膨胀型防火涂料的热传导系数随涂层温度变化曲线.提出将涂层温度为400~800℃时的热传导系数平均值作为涂层等效热传导系数,并用以进行被保护钢构件火灾下升温计算,所得钢构件的升温曲线与试验测得的升温曲线符合良好.参数分析表明,等效热传导系数与试件截面形状系数无关,与涂层厚度相关,表明用小尺寸钢板试件耐火试验结果计算所得的等效热传导系数可用于预测其他被保护钢构件在火灾下的升温.对不同涂层厚度热传导系数进行线性拟合,提出以涂层厚度20mm时的等效热传导系数作为非膨胀型防火涂料等效热传导系数特征值.     

钢结构防火涂料等效热传导系数的确定

针对目前钢结构防火涂料热工性能评价参数中存在的问题,给出了一种确定防火涂料综合热传导系数的方法.对几种防火涂料产品的抗火检测试验结果进行了试算,指出该方法为有膨胀型防火涂料钢构件的抗火设计与验算奠定了基础.     

膨胀型钢结构防火涂层湿热老化规律研究

膨胀型钢结构防火涂层隔热性能的退化程度受涂料类型、环境条件、使用时间、涂层厚度等因素的影响.为考察上述因素对膨胀型防火涂层耐老化性能的影响,进行了3种工况(变化参数为老化环境及涂料类型)共计78个试件的湿热老化试验及隔热性能试验.结果表明:单组分溶剂型防火涂料在高温高湿环境下更易发生老化;增加涂层厚度可以延缓老化进程;随使用时间延长,涂层防火隔热性能下降,等效导热系数增大,涂层等效导热系数随使用时间变化的规律与涂料类型和环境条件有关.工况1中涂层在老化后期的等效导热系数变化很小,此时涂层与环境所构成的体系已达到一个稳定的平衡状态;工况2和工况3中涂层等效导热系数随时间呈现出递增趋势.     

一种膨胀型饰面防火涂料防火性能的简易检测方法

为经济便捷地对膨胀型饰面防火涂料进行防火性能检测,设计了1种简易的防火性能测试装置.在一些简化假设的基础上,针对该测试方法,提出了1个包含6个关键变量的传热数学模型.研究发现:6个关键变量中,反映外炭化层隔热能力以及热源综合影响的参数i值对防火涂料防火保护时间的影响最为关键.利用曲线拟合,获得i值的计算公式,并通过测试起始涂覆厚度不同的1组透明饰面型防火涂料样品,估算出了该防火涂料的i值.     

面漆对膨胀型防火涂层隔热性能的影响

分别对有无面漆的膨胀型防火涂层保护的钢板试件进行了火灾试验,并对有无面漆的膨胀型防火涂层的膨胀率和等效导热系数进行了对比分析.将钢构件温度为400~600℃时涂层导热系数的平均值作为等效导热系数,并用之来评价有无面漆的膨胀型防火涂层的隔热性能.结果表明:面漆使膨胀型防火涂层的膨胀率降低了30%左右;无论有无面漆,膨胀型防火涂层的等效导热系数都与涂层干膜厚度呈线性关系,有面漆的膨胀型防火涂层等效导热系数比相同厚度的无面漆膨胀型防火涂层等效导热系数增大了30%~70%.     

CFRP加固RC梁防火保护措施优化分析

利用ABAQUS有限元软件对3根采用不同方法进行防火保护的CFRP加固钢筋混凝土梁的耐火试验进行了温度场模拟和热力耦合分析,并将模拟结果与试验结果进行对比,显示有限元模拟结果和试验结果吻合良好,并在此基础上通过改变防火保护层厚度进行了参数分析。模拟结果表明,采用8mm厚的厚型防火涂料或者15 mm厚水泥砂浆与0.5 mm厚超薄涂料组合防火保护就能保证试件在一定试验条件下满足耐火极限要求,是较经济、安全、实用性较强的防火保护方法。     

膨胀型防火涂料应用性能研究

针对几种典型的高聚物乳液进行试验,分析膨胀性能,得出最佳配比。试验研究膨胀型防火涂料粘接剂、主要材料等对涂料耐水性能、耐火性能、耐候性能的影响。从提高防火涂料本身的性能、应用防水涂层方面对防火涂料室外应用进行探讨,建议提高防火涂料粘接剂的含量,水性膨胀防火涂料选用Ⅱ型APP。     

反射隔热涂料热工计算方法研究

反射隔热涂料在夏热冬冷和夏热冬暖地区已有很多应用。试验证明,在屋面和外墙表面使用隔热涂料可以在夏季有效降低内表面温度,提高室内舒适度,降低空调耗电量。将有效传热系数法应用于反射隔热涂料的热工计算,该方法不仅考虑了太阳辐射吸收系数、半球发射率等重要参数,还充分考虑了当地气候状况的影响。针对武汉地区某实际项目,采用有效传热系数法对反射隔热涂料的传热性能进行了计算分析,结果表明该方法可以体现反射隔热涂料对墙体传热性能的影响,是较为科学合理的隔热涂料热工计算解决方案。     

轻型竹木复合墙体的热工性能试验研究

为研究轻型竹墙的热工性能,促进推广此类新型轻质墙材在节能建筑中的应用,设计并制作了2片轻型竹墙、1片轻型木墙以及1片轻型竹木复合墙,并进行了墙体的防护热箱试验,实测获取了墙体的热阻和传热系数。结合已有文献中轻钢龙骨墙体的热工性能的试验研究结果,对轻型竹墙、轻型木墙以及竹木复合墙体等的热工性能进行了比较研究。根据ISO 6946:2007的平均传热系数计算方法对轻型竹墙、轻型木墙以及轻型竹木复合墙体的稳态传热性能进行了计算和有限元分析,验证了有限元分析的可行性。基于有限元模型分别以材料的导热系数、龙骨间距、龙骨厚度及墙内钉间距为参数对3种轻型竹木墙体的热工性能进行了模拟分析。结果表明：轻钢龙骨墙体的传热系数最大,轻型竹墙与木墙的传热系数相近,说明以竹代木的设计理念是可行的;龙骨材料的导热系数垂直积层方向变化对墙体的热工性能影响较大;增加龙骨间距可适当减小墙体的传热系数,而增大龙骨厚度则可大幅减小墙体的传热系数;墙体热工性能受墙内钉间距影响较小,钉间距超过150mm时可忽略其影响。     

膨胀型防火涂层膨胀尺寸非线性传热模型

膨胀型防火涂层在膨胀过程中孔隙存在的对流传热和辐射传热会降低涂层的防火性能。考虑到孔隙之间存在涂层分解产生的气体,因此通过理想气体状态方程,描述了涂层在不同升温条件下的膨胀行为。建立了以膨胀尺寸为输出项,并考虑孔隙对有效导热系数增强作用的有限元传热模型,探究不同厚度的涂层在不同升温环境下的防火性能。结果表明：膨胀尺寸模型能够较为准确地预测涂层在不同温度场下的膨胀行为,涂层最大膨胀率随干膜厚度增大而减小;基于膨胀尺寸和多孔有效导热系数的有限元传热模型模拟的钢管温度变化与试验结果吻合较好;膨胀型防火涂层在高升温速率环境中能够明显延缓钢管升温,并降低其最大受火温度;不同升温环境中,涂层的防火能力和厚度呈非线性变化。     

彩钢复合门窗的热工性能分析

提升节能门窗的热工性能,降低其热能损耗,已经成为建筑节能领域重点关注的内容。该文拟采用二维有限元计算方法,将彩钢复合门窗与目前市场上运用较多的断桥铝合金门窗和多腔塑钢门窗的热工性能进行比较分析,阐述彩钢复合门窗的保温隔热原理,以便于进行新技术的推广应用。     

基于ANSYS的一型剪力墙热桥的位移场和应力场研究

该文运用稳态传热理论,采用有限元软件ANSYS模拟分析一型剪力墙热桥在3种结构形式(不保温、内保温及外保温)下的位移场、应力场,并量化分析对比热桥沿墙厚方向的应力变化。分析结果发现,外保温结构是一种良好的结构体系,能有效降低热桥由于温差作用产生的温度应力,改善结构受力性能,增强建筑物的耐久性,提高建筑结构使用寿命。因此具有重要的经济和社会效益。     

Thermal Performance of Composite Panels Under Fire Conditions Using Numerical Studies: Plasterboards, Rockwool, Glass Fibre and Cellulose Insulations

In recent times, light gauge steel frame (LSF) wall systems are increasingly used in the building industry. They are usually made of cold-formed and thin-walled steel studs that are fire-protected by two layers of plasterboard on both sides. A composite LSF wall panel system was developed recently, where an insulation layer was used externally between the two plasterboards to improve the fire performance of LSF wall panels. In this research, finite element thermal models of the new composite panels were developed using a finite element program, SAFIR, to simulate their thermal performance under both standard and Eurocode design fire curves. Suitable apparent thermal properties of both the gypsum plasterboard and insulation materials were proposed and used in the numerical models. The developed models were then validated by comparing their results with available standard fire test results of composite panels. This paper presents the details of the finite element models of composite panels, the thermal analysis results in the form of time–temperature profiles under standard and Eurocode design fire curves and their comparisons with fire test results. Effects of using rockwool, glass fibre and cellulose fibre insulations with varying thickness and density were also investigated, and the results are presented in this paper. The results show that the use of composite panels in LSF wall systems will improve their fire rating, and that Eurocode design fires are likely to cause severe damage to LSF walls than standard fires.     

Fire performance of cold-formed steel wall panels and prediction of their fire resistance rating

Recent research at the Queensland University of Technology has investigated the structural and thermal behaviour of load bearing Light gauge Steel Frame (LSF) wall systems made of 1.15 mm G500 steel studs and varying plasterboard and insulation configurations (cavity and external insulation) using full scale fire tests. Suitable finite element models of LSF walls were then developed and validated by comparing with test results. In this study, the validated finite element models of LSF wall panels subject to standard fire conditions were used in a detailed parametric study to investigate the effects of important parameters such as steel grade and thickness, plasterboard screw spacing, plasterboard lateral restraint, insulation materials and load ratio on their performance under standard fire conditions. Suitable equations were proposed to predict the time–temperature profiles of LSF wall studs with eight different plasterboard-insulation configurations, and used in the finite element analyses. Finite element parametric studies produced extensive fire performance data for the LSF wall panels in the form of load ratio versus time and critical hot flange (failure) temperature curves for eight wall configurations. This data demonstrated the superior fire performance of externally insulated LSF wall panels made of different steel grades and thicknesses. It also led to the development of a set of equations to predict the important relationship between the load ratio and the critical hot flange temperature of LSF wall studs. Finally this paper proposes a simplified method to predict the fire resistance rating of LSF walls based on the two proposed set of equations for the load ratio–hot flange temperature and the time–temperature relationships.     

三种复合墙体构造的热工性能分析

鉴于夏热冬冷地区的气候特点．针对外保温、内保温和复合墙板的保温三种不同的保温形式,计算墙体构造特性,建立ANSYS有限元模型对比分析不同构造墙体的热工性能。模拟结果表明：外保温墙体的温度波衰减度大,延迟时间更长,抵抗室外温度波变化能力强,热稳定性更好。     

Experimental study of hydrothermal aging effects on insulative properties of intumescent coating for steel elements

This paper reports the results of an experimental study of degradation in fire protection performance of two types of intumescent coating after different cycles of accelerated hydrothermal aging tests. Intumescent coating (without top coating) was applied to steel plate to make a test specimen. After subjecting the specimen to the aging test, fire test was carried out to obtain the steel plate temperature. In order to help understand the aging mechanism of intumescent coating, TGA tests, XPS tests and FTIR tests were also conducted on the intumescent coating after the accelerated aging test. In total, tests were performed on 56 intumescent coating protected steel specimens, of which 16 specimens were applied with type-U intumescent coating and the other 40 with type-A intumescent coating. Results of the degradation mechanism study reveal that the hydrophilic components of intumescent coating move to the surface of the coating and can be dissolved by moisture in the air, which can destroy the intended chemical reactions of these components with others and deter formation of the desired effective intumescent char. The consequence of this is reduced expansion of the intumescent coating and increased effective thermal conductivity. Compared to specimens without hydrothermal aging, after 42 cycles of hydrothermal aging (to simulate 20 years of exposure to an assumed exposure environment), the effective thermal conductivity of type-U intumescent coating was 50% higher and that of type-A intumescent coating 100% higher than that of the fresh coating. These increases in effective thermal conductivities resulted in increases in steel temperatures of up to 150 °C and 220 °C higher than the steel temperatures of the specimens without hydrothermal aging for the type-U intumescent coating and type-A intumescent coating specimens, respectively.