不同边界约束条件的混凝土双向板抗火性能研究

发布时间：2018-04-01 11:36

本文选题：足尺试验　切入点：钢筋混凝土双向板　出处：《哈尔滨工业大学》2013年博士论文

【摘要】：火灾下，钢筋混凝土双向板受力复杂，且影响因素多，目前相关的试验及理论研究尚不完善。单个构件抗火试验可以为结构抗火设计提供初步的数据支持和理论指导，但是单个构件与真实整体结构中构件的受力情况、边界条件并不相同，整体结构中相邻构件间的相互作用以及其它部分对构件的约束作用可以对构件的火灾行为产生不同的影响。基于上述原因，本文开展了对足尺四边简支双向板、四边固支双向板以及足尺钢框架整体结构中钢筋混凝土双向板的抗火性能研究，主要研究内容如下：（1）开展了足尺四边简支双向板和足尺四边固支双向板在恒载升温条件下的抗火性能试验。试验测量了火灾作用下板的竖向挠度和平面内位移、沿板厚度混凝土温度场的分布及钢筋温度的变化、考察了固支板板边处约束反力的变化，分析了火灾下板的裂缝开展规律以及破坏特征。结果表明：火灾下四边简支双向板分别在板顶的长跨跨中和1/4跨度处出现三条与短跨方向平行的主裂缝，四边固支双向板在板顶沿板边形成椭圆型塑性铰线；四边固支双向板的抗火性能优于四边简支双向板。（2）利用传统塑性铰线理论对板的极限承载力计算时无法考虑受拉薄膜效应的影响，计算值偏保守。本文在传统塑性铰线理论的基础上，根据板块平衡法和能量法的计算原理，认为受拉薄膜效应是由塑性铰线截面处钢筋合力的竖向分量或钢筋伸长做功所引起，提出了考虑受拉薄膜效应的火灾下钢筋混凝土双向板极限承载力计算方法；基于试验结果，利用改进的板块平衡法和能量法对无水平约束的四边简支双向板和四边固支双向板在火灾下的极限承载力进行了计算，结果表明：本文所提出方法的计算结果与试验结果吻合很好。（3）利用自行研制的火灾试验炉，开展了1栋3层3×3跨足尺钢框架整体结构中的角区格板和中区格板的火灾试验，并对其火灾行为进行了研究。结果表明：火灾下整体结构中相邻构件间的相互作用以及周边相邻构件的约束对板的火灾行为影响显著；角区格板在板顶靠近内板边的1/4跨度处（板顶负弯矩钢筋截断处）出现对板的力学行为有较大影响的主裂缝，中区格板在板顶沿板边形成圆型塑性铰线；由于结构连续性及相邻构件间的互相约束，与受火板相邻的未受火板顶也出现了规则裂缝；整体结构中钢筋混凝土双向板具有较好的抗火性能。（4）开展了将声发射技术用于火灾下整体结构中钢筋混凝土双向板的破坏监测研究。考察了火灾作用下板的声发射事件数、能量率和b值的变化，，分析了各参数与板的裂缝开展、炉温及竖向位移等的关系。结果表明：利用事件数、能量率、b值等参数可以准确区分火灾下钢筋混凝土双向板的裂缝早期开展阶段、裂缝集中出现阶段以及裂缝缓慢扩展阶段；火灾下板的声发射参数产生突变时，如能量率突然升高、b值突然下降等，表征结构可能出现破坏，应给予足够关注。（5）开展了火灾下整体结构中钢筋混凝土双向板的振动特性研究。通过快速Fourier转换，分析了火灾作用下板的频率变化。结果表明：火灾下整体结构中相邻构件对受火板的约束作用对板频率的影响较为显著；火灾下整体结构中中区格板的频率明显高于角区格板；火灾中角区格板和中区格板的频率均有不同程度下降，角区格板的频率下降幅度高于中区格板。
[Abstract]:Fire, reinforced concrete two-way slabs with complex and affected by many factors, the current test and the relevant theoretical research is still not perfect. The test can provide the fire resistance design of preliminary data support and theoretical guidance for structural fire resistance of single component, but individual components and overall structure of real component stress, boundary condition is not the same, the constraint interaction between adjacent components in the whole structure and other parts of the component can have different effects on the fire behavior of components. Based on the above reasons, this paper carried on the full-scale two-way slab simply supported on fire resistance of reinforced concrete slabs with clamped slabs and full-scale steel frame integral in the structure, the main research contents are as follows:
(1) carried out a full-scale two-way slab simply supported and clamped full-scale two-way slab heating under constant load fire resistance test conditions. Test the fire under the action of the vertical deflection and in-plane displacement, distribution and changes of temperature along the thickness of reinforced concrete temperature field, the effect of solid support plate plate edge constraint force changes, analysis of cracks under fire plate development and failure characteristics. The results showed that: under fire simplysupported two-way slabs were at the top of the board of the long span and 1/4 span at three and the short span direction parallel to the main crack, four clamped edges and two boards in board the top is formed along the edge of the board for the plastic hinge line; clamped two-way slab fire resistance is better than that of simply supported two-way slabs.
(2) affected by the tensile membrane effect can not be considered when calculating the ultimate bearing capacity by using the traditional theory of plastic hinge line on board, the calculated value is conservative. Based on the traditional plastic hinge line theory, according to the calculation principle of the plate balance method and energy method, that the tensile membrane effects are caused by the plastic hinge line section of the vertical component of force steel or reinforced elongation work, puts forward the calculation method of ultimate bearing capacity of reinforced concrete two-way slab tensile membrane effects under fire; based on the test results, using the improved plate equilibrium method and energy method of horizontal restraint two-way slab four edges simply supported and clamped two-way plate limit under fire carrying capacity is calculated, and the results show that the proposed method and the calculation results agree well with the test results.
(3) using the self-made fire test furnace, carry out the fire test corner grid plate and the central board of 1 Building 3 layer 3 * 3 span full-scale steel frame of the whole structure, and the fire behavior were studied. The results showed that the fire behavior of fire under the interaction of adjacent structure components and the adjacent component constraint on the plate effect; corner grid plate in 1/4 span at the top plate near the inner edge of the plate (top plate of negative moment reinforcement cutoff) of cracks appeared on the mechanical behavior of the plate has great influence on the central grid plate at the top of the board is formed along the edge of circular plastic hinge line; mutual restraint due to structural continuity and adjacent components, and the fire plate adjacent unfired top plate also appeared crack; reinforced concrete slab structure has good fire resistance.
(4) to carry out the acoustic emission technology is used to study damage monitoring of reinforced concrete slab structure under fire in the fire. The influences of plates subjected to acoustic emission events, the energy change rate and b value, the analysis of fracture parameters and the relationship between the board, temperature and vertical displacement. The results show that by the number of events, energy rate, b value and other parameters can accurately distinguish fire early cracks in reinforced concrete slab crack development stage, concentrated phase and slow crack growth stage; fire plate parameters of acoustic emission generated mutation, such as energy rate suddenly increased, b value decreased abruptly, characterization of possible structure failure, should be given adequate attention.
(5) to carry out the research on the vibration characteristics of reinforced concrete slabs under fire in the whole structure. Through the fast Fourier transformation, analysis of the frequency changes under fire board. The results show that the whole structure of the component under fire adjacent constraint on fire board to board the frequency influence is obvious; the whole structure under fire in the central grid plate was significantly higher than the frequency of grid plate corner; frequencies have corner grid plate and the central board of the fire in different degrees of decline, grid plate corner frequency decrease than the central grid plate.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU375.2

【相似文献】