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Title |
The Effect of Mild Tensile Reinforcement and Effective Prestress on the Flexural Performance of the Prestressed Lightweight Concrete Beams with Unbonded Tendons
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Keywords |
포스트텐션 보 ; 경량 콘크리트 ; ACI 318-08 ; 휨 내력 ; 비부착 긴장재의 응력 post-tensioned beams ; lightweight concrete ; ACI 318-08 ; flexural capacity ; stress of unbonded tendons |
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Abstract |
Seven post-tensioned lightweight concrete (LWC) beam specimens were tested under a symmetrical two-point top loading system. The parameters investigated were the amounts of mild longitudinal reinforcement and effective prestressing. The design compressive strength and dry density of the LWC tested were 30 MPa and 1,770 kg/m3, respectively. Similar to post-tensioned normal weight concrete (NWC) beams, the crack propagation and stress increase of the unbonded tendons were significantly affected by the amounts of mild longitudinal reinforcement and effective prestressing. With the increase in the amounts of mild longitudinal reinforcement and effective prestressing, the serviceability and flexural capacity of the beams were enhanced whereas the stress increase in the unbonded tendons decreased. To control the crack width in post-tensioned LWC beams, a minimum amount of mild longitudinal reinforcement specified in ACI 318-08 provision is required. The flexural behavior of post-tensioned LWC beams and stress increase of the unbonded tendons could be rationally predicted by the proposed non-linear two-dimensional analysis. On the other hand, ACI 318-08 flexure provision was too conservative about the post-tensioned LWC beams.
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