Experiment on Post-fire Mechanical Properties of Q355qNH Bridge Weathering Steel
ZHANG Xin1,2, YIN Hang2, ZHAO Ernian1,2,*, LIU Jinhui2
1 Key Laboratory of Building Structural Retrofitting and Underground Space Engineering (Shandong Jianzhu University), Ministry of Education, Jinan 250101, China 2 School of Civil Engineering, Shandong Jianzhu University, Jinan 250101, China
Abstract: To investigate the post-fire mechanical properties of bridge weathering steel (WS) after expose to high temperature, the tensile test of Q355qNH steel considering eight socking temperatures from 300 ℃ to 1 000 ℃ and two cooling methods, which were cooling in air (CA) and cooling in water (CW), was carried out. The microscopic fracture morphology under the two cooling methods was studied. The effect of high temperature treatment and cooling method on the stress-strain relationship and mechanical parameters of Q355qNH steel was analyzed, and the results were compared with that of building steels after expose to high temperature. Results show that high temperature treatment and cooling methods have little influence on the elastic modulus of Q355qNH steel. The plastic plateau of the stress-strain curve disappears when the WS specimens cooling in water after expose to 800 ℃ high temperature or above. Besides, there are obvious plastic plateau in other cases. When the socking temperature reaches 700 ℃ or above, the effect of cooling methods on the strength of Q355qNH steel is gradually appears, and the yield strength and ultimate strength with CA condition begin to decrease, however, the elongation after fracture increases. For the CW condition, the ultimate strength increases and the elongation after fracture decreases with the increases of socking temperature, and the variation of yield strength greatly fluctuates. Compared with results of building steels in exciting literatures, Q355qNH weathering steel shows a better fire resistance from the perspective of post-fire strength.
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2023, Vol. 37 
