Abstract
In order to obtain the law of the fatigue damage development of reinforced concrete hollow beams that has been in service for 24 years, its solid hollow beams were removed and transported to the laboratory for loading test. Two beams were selected for static loading to obtain the ultimate flexural bearing capacity, and three beams were, respectively, subjected to constant-amplitude fatigue loading with different load amplitudes. The static and dynamic behaviors of the beams were monitored in the fatigue test. The fatigue failure of the beams showed that the outermost rebar at the butt weld fractured at first, and the crack width at the fracture position of the steel bar was about 0.3 mm, which was largest in all cracks. After a rebar was broken, midspan deflection and flexibility increased by approximately 20% and 10%, respectively, relative to the initial state. The damage developed rapidly in the following range: (1) the first 10,000 fatigue cycles; (2) after fatigue fracture of the rebar; and in the intermediate stage of fatigue test, the damage development was relatively stable. As the loading amplitude increased, the stiffness degradation and the cumulative damage that occured under the same loading cycle were more significant.
Highlights
In the last 40 years, most of the bridges in China have been built using reinforced concrete
A large number of fatigue test studies on reinforced concrete beams showed that its failure characteristics were generally fatigue fracture of one or part of tensile rebars. e fracture process of rebar can be divided into crack initiation stage, stable crack growth stage and brittle fracture stage [8,9,10,11]
After the fracture of longitudinal tensile reinforcement, the firstand second-order frequencies were reduced by 3.5% and 2.5%, respectively, compared with those of the initial state
Summary
In the last 40 years, most of the bridges in China have been built using reinforced concrete. A large number of fatigue test studies on reinforced concrete beams showed that its failure characteristics were generally fatigue fracture of one or part of tensile rebars. Chang et al studied the relationship between crack development, midspan deflection, steel strain, and fatigue load through the fatigue performance test of 11 reinforced concrete specimens and obtained the S−N curve of the reinforced concrete beams [12]. Wang et al conducted fatigue tests of reinforced concrete beams in air, fresh water, and salt water environments and studied the deformation development process and fatigue life of the beams in three environments under repeated loads [14]. Yu et al conducted fatigue tests on 12 pieces of 1 : 6 scale model beams to study the fatigue failure form, amplitude, stiffness, steel strain, and concrete strain of heavy-haul railway bridge with the number of repeated loads [16]. Deflection, strain of concrete and rebars, and vibration mode changes were recorded during loading, and the development of fatigue damage was summarized
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