火灾后钢筋混凝土异形柱结构损伤评估的基础研究

The beam, column and beam-column joint in reinforced concrete structure with special-shaped column after fire, due to larger surface area and thinner thickness, are generally damaged more serious than those in structure with non-special-shaped column. Up to now, researches on damage assessment of reinforced concrete structure with special-shaped column after fire are few. Through the experiments and numerical simulation, the compression performance, the shear performance and the seismic performance of concrete special-shaped column, will be studied systematically. Then, the bending performance, shear performance and internal force distribution of the concrete simple-supported T-shaped beam and continuous T-shaped beam with a high depth-to-width ratio of cross-section after fire will be carried out. Subsequently, the seismic performance of beam-column interior-joint and exterior joint with slab and orthogonal beam in the special-shaped column structure after fire will be conducted. And the seismic performance of single layer space frame with special-shaped column will be further performed. The quantitative evaluation method for the residual capacity of the special-shaped column structure will also be put forward. A new parameter index named "fire exposure time ratio" is proposed, and the experimental and numerical methods to quantitatively determine the post-fire compression performance influenced by the sustained axial load under high temperature will be constructed. The mechanical analysis model for the shear behavior of the special-shaped column, the concrete beam with compression zone directly exposed to fire and the beam-column joints after fire will be established. The influence laws of the directional anisotropy on shear capacity after fire will also be revealed. The fire damage regularity and characteristics of the members in frame with special-shaped column will be further clarified. The project aims to lay a foundation for damage assessment and seismic strengthening of the concrete structure with special-shaped column after fire.

异形柱结构的梁、柱和节点区由于表面积较大、肢厚较薄等原因，其火灾后损伤程度通常比非异形柱结构的更为严重，但目前有关火灾后混凝土异形柱结构损伤评估方面的研究成果较少。通过试验和数值模拟，对受火后混凝土异形柱的受压、受剪和抗震性能，受火后截面高宽比较大的混凝土简支T形梁和连续T形梁的受弯、受剪、内力分布等承载性能，受火后异形柱结构中带正交梁和楼板翼缘的中节点和边节点的抗震性能，受火后单层异形柱空间框架的抗震性能等进行较系统的研究，并提出其灾后承载力的定量评定方法；提出“受火时间比”这一新的参数指标，建立能定量考察高温下持荷对灾后柱式构件受压性能影响的试验方法和数值模拟方法；建立异形柱、压区高温梁、梁柱节点受火后受剪性能的力学分析模型，揭示灾后受剪的方向异性对其受剪承载力的影响规律；阐明异形柱空间框架中构件的火灾损伤特性和规律。项目研究成果可为火灾后混凝土异形柱结构的损伤评定和抗震修复奠定基础。

火灾后混凝土异形柱结构的梁、柱和节点因肢厚较薄等特点导致其损伤程度较非异形柱结构的更为严重，而且实际工程中火灾下荷载、梁上开设圆孔等情况也会对混凝土结构受火后性能产生不利影响，但目前有关异形柱结构火灾后性能损伤方面的成果偏少。本项目从试验研究、计算分析、实用计算和规范编制等方面开展了系列的研究，主要研究内容和结果：(1) 开展了10根混凝土异形柱、13根混凝土异形短柱的抗震性能试验和计算分析，较系统考察了柱截面形状、受火时间、受火方式、水平力加载方向和加载模式对异形柱承载性能的影响规律。(2) 进行了11根较大截面高宽比的简支T形梁承载性能的试验研究和计算分析，考察了受火时间、剪跨比、受火工况等影响；完成了1根未受火、3根单跨受火后混凝土两跨连续梁承载性能的试验研究，考察受火时间和配筋率对连续梁内力重分布的影响情况。(3) 进行了8根常温下、4根火灾下、15根高温后圆孔混凝土梁承载性能的试验研究，考察了圆孔位置、圆孔处是否切断箍筋、过火温度和圆孔直径对混凝土梁受弯和受剪承载性能的影响情况，并建立了承载力简化计算方法。(4) 进行了10根考虑火灾下“受火时间比”、持荷情况影响的混凝土梁灾后受弯性能的试验研究，并通过试验揭示了初应力对高温后钢筋屈服强度的影响规律。(5) 进行了8个异形柱梁柱中节点、8个方形柱梁柱中节点、7个方形柱梁柱边节点的抗震性能试验，较系统考察了柱截面形状、受火时间、受火方式、正交梁和楼板翼缘、轴压比等因素对梁柱节点的破坏形态、滞回曲线、承载力和耗能等影响情况。(6) 分别进行了8片、6片地聚物混凝土三明治墙受压、抗震性能的试验研究，提出了该类墙体轴压承载力、面内偏压承载力和稳定性验算的简化方法。(7) 进一步发展火灾后混凝土结构的鉴定标准，包括检测火灾后受力引起的裂缝宽度、火灾后混凝土结构内力和构件承载力的简化分析原则和方法等。项目研究成果可供火灾后混凝土结构鉴定参考。