WIND-INDUCED FAILURE PROCESS OF RC HYPERBOLIC COOLING TOWERS CONSIDERING THE MATERIAL NONLINEARITY

To investigate the ultimate wind load and wind-induced failure process of cooling towers, a hyperbolic cooling tower was taken as an example in ABAQUS. The tower shell was modelled by layered shell elements, including the concrete and reinforcement. Based on linear and nonlinear verification calculation, the smeared crack model and bilinear model were used to represent the nonlinear behavior of the concrete and reinforcement, respectively. The failure process under the load combination of gravity and wind loads (Load Case Ⅰ) and the load combination of gravity, winter temperature and wind loads (Load Case Ⅱ) were analyzed. It was shown that when the wind load factor λ was 1.384 for Load Case Ⅰ, the circumferential cracks caused by meridian forces were initiated at h_s/H_s=0.37 of the windward meridian and went through the shell. Then they continuously expanded along the circumferential direction and the meridian cracks inside the windward and outside the sideward were also caused by circumferential moment. In this process, the stress of steel at the cracks increased quickly, the load displacement curves exhibited nonlinearity, and the displacement at the windward and sideward quickly increased. There was also significant redistribution of the internal forces at these areas. The cooling tower failed as the successive concrete cracking and the yielding of the double reinforcement in the throat region when the ultimate wind load λ was 2.007. For Load Case Ⅱ, the meridian cracks first appeared at the upper area of the sideward at λ=1.0 because of the temperature effect, with a slightly greater degree than that of Load Case Ⅰ. However, the load displacement curves were almost the same for the two load cases because the effect of temperature was limited. The most significant cracking was still circumferential cracking in the windward. The failure of the structure was also controlled by the wind load, with an ultimate load factor λ of 1.842.