Experimental Investigation And Nonlinear Finite Element Analysis Of The Performance Of H-Section Steel Frame In Fire

In this paper, the performance of full-scale H-section steel beams, steel columns, steel joints and steel frames in fire is investigated. The whole tests were made use of the self-made fire-test furnaces.The performance of 14 H-section steel beams in fire is investigated. The main factors including boundary condition, span and applied load ratio which may have influence on the performance of H-section steel beams in fire are examined. From the test results, the regularities of temperature field, deflection, axial restraining force and connection moment are presented. The test results show that local buckling and lateral torsional buckling takes place for H-section steel beams in fire. The performance of H-section steel beams in fire is influenced by boundary condition. When steel beams (semi-rigid connection and flexible connection) undergo a large deflection, compression force then quickly changes into tension force, which supports steel beams and reduces further deflection, that is to say, catenary action takes place.The performance of 10 H-section steel columns in fire is investigated. The main factors including boundary condition, loading level, axial restraining deflection and eccentrical loading which may have influence on the performance of H-section steel columns in fire are examined. From the test results, the regularities of lateral deflection, axial deflection and axial restraining force are presented. The test results show that flexural-torsional buckling takes place for H-section steel columns in fire. Increasing the loading level causes a drop for the limit temperature of steel columns. The performance of H-section steel columns in fire is influenced by boundary condition. Limittemperature of axially restrained columns is lower than that of free expansive columns. Limit temperature decreases if steel columns are subject to fire again. Axial deflection of free expansive steel columns is divided into two stages in fire: expansive stage and compress stage. The compress stage is very short and steel columns quickly happen to destroy in compress stage.The performance of seven middle joints and eight exterior joints for H-section steel frames in fire is investigated. The main factors including joint form, stiffening rib and end-plate thickness which may have influence on the performance of joints in fire are examined. From the test results, the regularities of rotation-temperature are presented. The test results show that the failure models of joints in fire are influenced by joint position, connection method and stiffening rib. Stiffening rib of web can enhance limit temperature of end-plate connections.The performance of four one-story one-bay H-section steel frames and six two-story two-bay H-section steel frames in fire is investigated. The main factors including structure form between steel beam and reinforced concrete slab and fire condition which may have influence on the performance of H-section steel frames in fire, are examined. From the test results, the regularities of temperature field and deflection are presented. The test results show that compressive buckling takes place at the H-section steel columns of H-section steel frames in fire. The deflection of bay in fire has no significant influence on the deflection of bay without fire for two-story two-bay H-section steel frames.Programs are developed to analyze the deflection of one-story one-bay H-section steel frames in fire by Updated Lagrange Formulation. Effect of semi-rigid connection on the performance of one-story one-bay steel frames in fire is analyzed too. The computing results show in good agreement with the test results. It demonstrates that the method and the computer program are reliable.