As a common type of joint used in spatial grid structures, the tensile performance of bolt-sphere joints directly affects the safety of the spatial grid structure under fire. To study the tensile properties of the bolts in sphere joints under fire, the four sets of 36 bolt-sphere joints consist of M20, M24, M30, and M36 high-strength bolts were conducted in elevated temperature by steady-state test. Therefore, the tensile bearing capacity of the bolt-sphere joint was obtained under different elevated temperatures. Experimental results show the destroyed section of the bolt-sphere joint that occurs in the thread of the high-strength bolt at the intersection of the sphere because of the maximum concentration of stresses that occurred in areas of destruction. The brittle fracture of bolt-sphere joints happened when the temperature is below 400 ℃. As the temperature increased, the neck shrinkage of the damaged section of the bolt becomes more apparent, and the ductile failure of the bolt-sphere joint occurred. The stiffness and the bearing capacity of bolt-sphere joints decreased gradually as the temperature rose. Conversely, the ductility was gradually increasing. When the temperature was greater than 300 ℃, the stiffness and the bearing capacity of the bolts in sphere joint decreased rapidly. The bearing capacity reduction coefficient of the high-strength bolts with different diameters were next to the same at elevated temperatures. According to the experimental data, the formulas of the tensile bearing capacity reduction coefficient of bolt-sphere joints were obtained.

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火灾下球形接头螺栓拉伸性能的实验研究

作为空间网格结构中常用的一种接头，螺栓-球形接头的抗拉性能直接影响着火条件下空间网格结构的安全性。为了研究火灾下球形接头中螺栓的抗拉性能，通过稳态试验在高温下进行了四组共36个由M20，M24，M30和M36高强度螺栓组成的球形接头。因此，在不同的高温下获得了螺栓-球形接头的拉伸承载力。实验结果表明，由于破坏区域中应力的最大集中，螺栓-球形接头的破坏部分出现在球体相交处的高强度螺栓的螺纹中。温度低于400℃时，发生了螺栓-球形接头的脆性断裂。随着温度升高，螺栓损坏部位的颈缩变得更加明显，并且发生了螺栓-球形接头的延性破坏。随着温度的升高，螺栓-球形接头的刚度和承载力逐渐降低。相反，延展性逐渐提高。当温度高于300℃时，球形接头中螺栓的刚度和承载能力迅速下降。在高温下，不同直径的高强度螺栓的承载力降低系数几乎相同。根据实验数据，得出了螺栓-球形接头抗拉承载力减小系数的公式。并且发生了螺栓-球形接头的延性破坏。随着温度的升高，螺栓-球形接头的刚度和承载力逐渐降低。相反，延展性逐渐提高。当温度高于300℃时，球形接头中螺栓的刚度和承载能力迅速下降。在高温下，不同直径的高强度螺栓的承载力降低系数几乎相同。根据实验数据，得出了螺栓-球形接头抗拉承载力减小系数的公式。并且发生了螺栓-球形接头的延性破坏。随着温度的升高，螺栓-球形接头的刚度和承载力逐渐降低。相反，延展性逐渐提高。当温度高于300℃时，球形接头中螺栓的刚度和承载能力迅速下降。在高温下，不同直径的高强度螺栓的承载力降低系数几乎相同。根据实验数据，得出了螺栓-球形接头抗拉承载力减小系数的公式。当温度高于300℃时，球形接头中螺栓的刚度和承载能力迅速下降。在高温下，不同直径的高强度螺栓的承载力降低系数几乎相同。根据实验数据，得出了螺栓-球形接头抗拉承载力减小系数的公式。当温度高于300℃时，球形接头中螺栓的刚度和承载能力迅速下降。在高温下，不同直径的高强度螺栓的承载力降低系数几乎相同。根据实验数据，得出了螺栓-球形接头抗拉承载力减小系数的公式。