Abstract：In order to rapidly detect and evaluate the bearing capacity of existing concrete bridges with different damage states, the 16m-span prestressed concrete single-piece simply supported hollow slab beam demolished in an actual expressway reconstruction and expansion project was taken as the research object.The applicability and accuracy of the measured modal deflection and modal stiffness in evaluating the bearing capacity of existing bridges in practical engineering are discussed by combining modal test technology with static loading and unloading test.The static load test loading and unloading conditions and environmental excitation modal test conditions of 14 different damage degrees of simply supported single beams were designed. The static load deflection of the simply supported test beam and the experimental modal parameters of the beam body with different damage degrees were measured. The modal deflection of the simply supported beam under step-by-step static load was predicted. The tangent stiffness and modal stiffness of the load-displacement curve of the test beam under different damage conditions were compared and analyzed.The results show that the measured loading and unloading static deflection of the test beam before cracking is roughly linear with the load. After cracking, with the increase of the damage degree of the beam, the linear elastic stage of the load-displacement curve gradually decreases, and the nonlinear stage gradually increases, showing a significant stiffness degradation trend.When the test beam is in the light damage state before cracking and the large damage state in the initial loading stage after cracking, the relative error between the modal deflection predicted by the first two modes and the static load deflection is basically less than 10 %. The relative error between the modal stiffness and the initial stiffness of the load-displacement curve of the static load test is basically within 10 %. The modal stiffness of the test beam with a damage degree lower than the large damage is approximately equal to the initial tangent stiffness of the beam.The relative error between the modal stiffness of the lightly damaged simply supported beam before cracking and the tangent stiffness of the design bending moment is less than 10 %, indicating that the measured modal stiffness of the structure can accurately evaluate the initial stiffness state of the prestressed concrete simply supported beam that has been subjected to 4 times the design load and has been greatly damaged. It can also accurately evaluate the design structural stiffness of the lightly damaged uncracked simply supported beam bridge that has been subjected to 2 times the design load.This has important reference and guiding significance for the practical engineering application of measured modal deflection and modal stiffness, and also expands the application scope of modal testing in the technical evaluation of bridge health conditions.
亓兴军1，孙绪法1，周广利2，王珊珊3. 损伤状态下预应力混凝土简支梁的模态挠度和模态刚度试验研究[J]. 振动与冲击, 2023, 42(21): 227-236.
QI Xingjun1, SUN Xufa1, ZHOU Guangli2, WANG Shanshan3. Test study on modal deflection and modal stiffness of prestressed concrete simply supported beams under damage state. JOURNAL OF VIBRATION AND SHOCK, 2023, 42(21): 227-236.
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