两长边简支和两短边固支钢筋混凝土双向矩形板的火灾行为试验

进行两对边简支、两对边固支钢筋混凝土双向板在恒载-升温工况下火灾试验,研究板内混凝土和钢筋的温度场变化、板平面内的竖向变形、板平面外的水平位移,以及板边绕支承轴线转角变化的情况.描述和分析双向板在火灾下的宏观现象和破坏特征,并与同轴线尺寸的其他3种边界条件双向板进行对比.试验结果表明:板面裂缝整体成椭圆裂缝,板中区域沿长跨、短跨方向均存在多条较大裂缝,板面裂缝由固支边中部区域横向裂缝与固支边角部密集的环形斜裂缝组成;板内存在明显的温度梯度,形成非线性温度场;在升温过程中,板平面外位移整体呈现非线性趋势、板中部位移较大;而在降温过程中,板中位移回弹明显,板中竖向位移与炉温快速下降的变化趋势不一致,出现较长的水平段;整个升温过程中,混凝土板边持续向外膨胀,固支边位移较简支边位移变化小;简支边转角随着受火时间不断增大、整体较大.

Fire Behaviorresearch of Rectangular Reinforced Concrete Two-Way Slabs Simply Supported on Two Long Sides and Fixed on Two Short Sides

The fire tests of reinforced concrete two-way slabs with simple supports, fixed supports on two opposite sides under dead load and temperature rise conditions were carried out. The variations of temperature field of concrete and reinforcement in the slab, the vertical deformation in the slab plane, horizontal displacement out of the slab plane and rotation angle of the slab side around the support axis were studied. The macroscopic phenomena and failure characteristics of two-way slabs under fire were described and analyzed, and compared with other three boundary conditions of the two-way slab with the same axial line size. The test results show that the slab surface cracks are elliptical as a whole, and there are many large cracks in the middle area of the slab along the long-span and short-span directions. On the slab surface, there exist transverse cracks in the middle area of the fixed support side and dense annular oblique cracks in the corners of the fixed support side; there is an obvious temperature gradient in the slab, forming a nonlinear temperature field; in the process of heating up, the out of plane displacement of the slab shows a nonlinear trend as a whole, and the displacement in the middle of the slab is large; and during the cooling process, the rebound of displacement in the slab is obvious, and the change trend of vertical displacement in the slab is inconsistent with the rapid decline of furnace temperature, and a long horizontal section appears; during the whole heating process, the concrete slab side continues to expand outward, and the displacement of fixed support side is smaller than that of simple support side; the rotation angle of simply supported side increases with the fire time, and the whole value is large.