Fatigue Behavior Of Beams Research Articles

Effects of the reinforcement ratio and chloride corrosion on the fatigue behavior of RC beams

Effects of reinforcement ratio (1.06%, 1.59% and 2.91%), and combined actions of initial fatigue damage and chloride corrosion (0.4 million cycles’ fatigue loading followed by 6 months’ NaCl solution wet-dry cycles) on the fatigue behavior of beams were experimental investigated. Results show: (1) directly fatigue loaded beams with reinforcement ratio of 2.91%, presented nonlinear developments of concrete tensile strains, deflections, amplitudes and stiffness; (2) these combined actions accelerated beams’ degradation, reflecting by the increased deflections, and nonlinear developments at reinforcement ratios of 1.59% and 2.91%; (3) total fatigue life of beams with these combined actions were >66% shorter than without.

Fatigue behavior of concrete beams reinforced with glass- and carbon-fiber reinforced polymer (GFRP/CFRP) bars after exposure to elevated temperatures

This paper deals with fatigue performance of concrete beams reinforced with fiber reinforced polymer (FRP) bars after exposure to elevated temperatures. A total of 13 concrete beams reinforced with glass- and carbon-fiber reinforced polymer (GFRP/CFRP) bars were tested under static and fatigue loading after exposure to different levels of elevated temperatures. The influences of elevated temperature, holding time, fatigue load level and FRP bar type on the fatigue behavior of beams were investigated. The results showed that the elevated temperature exposure reduced more severely the fatigue life of GFRP-reinforced concrete beam than that of CFRP-reinforced beam below 400 °C, and GFRP- and CFRP-reinforced beams both lost their bearing capacities when the exposure temperature reached 600 °C. The elevated temperature accelerated the development of concrete strain, crack width and deflection of FRP-reinforced concrete beams with the number of fatigue cycles. The mid-span deflection was predicted using some existing models, and the CEB-FIP model showed the best accuracy with the coefficient of variation of 2.8–7.0%. The fatigue strength of GFRP- or CFRP-reinforced concrete beams is not affected by elevated temperatures up to 400 °C for 2 h.

Fatigue Assessment Model of Corroded RC Beams Strengthened with Prestressed CFRP Sheets

This paper presents a fatigue assessment model that was developed for corroded reinforced concrete (RC) beams strengthened using prestressed carbon fiber-reinforced polymer (CFRP) sheets. The proposed model considers the fatigue properties of the constituent materials as well as the section equilibrium. The model provides a rational approach that can be used to explicitly assess the failure mode, fatigue life, fatigue strength, stiffness, and post-fatigue ultimate capacity of corroded beams strengthened with prestressed CFRP. A parametric analysis demonstrated that the controlling factor for the fatigue behavior of the beams is the fatigue behavior of the corroded steel bars. Strengthening with one layer of non-prestressed CFRP sheets restored the fatigue behavior of beams with rebar at a low corrosion degree to the level of the uncorroded beams, while strengthening with 20- and 30%-prestressed CFRP sheets restored the fatigue behavior of the beams with medium and high corrosion degrees, respectively, to the values of the uncorroded beams. Under cyclic fatigue loading, the factors for the strengthening design of corroded RC beams fall in the order of stiffness, fatigue life, fatigue strength, and ultimate capacity.

Fatigue and post-fatigue monotonic behaviour of partially prestressed concrete beams

The objective of this work was to study the fatigue and post-fatigue monotonic behaviour of partially prestressed concrete (PPC) beams with a high degree of prestress. Eleven large PPC beams were tested under fatigue and monotonic loading. The effects of applied load level and severity of fatigue damage on the beams' fatigue and post-fatigue monotonic behaviour were studied and analysed. The results indicated that the fatigue behaviour of beams with a high degree of prestress was dependent on the applied load level. For an optimum and safe design, the applied load level should be less than 1·28 times the cracking load, the maximum crack width should be limited to 0·20 mm and the initial maximum stress range of non-prestressed reinforcing bars before repeated loading should be less than 170 MPa. The post-fatigue monotonic behaviour of beams was related to the severity of fatigue damage prior to the monotonic test. Low fatigue damage was found to have only a slight impact on the monotonic behaviour of the beams, whereas medium and high fatigue damage respectively reduced the ultimate strength by up to 15·2% and 18·0% and increased the deformability ductility index by up to 18·6% and 41·0%.

Research on Fatigue Behavior of Beam with Corrugated Steel Webs

This paper present that experimental research on the fatigue behavior of beam with Q345c steel corrugated webs. There are four test specimens with different structural feature will be tested in three-point bending to load by Shinmadzu 4890 fatigue testing machine. Moreover, the finite-element analysis will be used to simulate the fatigue behavior of common beam with corrugated steel web. Weld will be our focus on importance object.