Structural Engineering and Mechanics

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Flexural tests on two-span unbonded post-tensioned lightweight concrete beams

  • Yang, Keun-Hyeok (Department of Architectural Engineering, Kyonggi University) ;
  • Lee, Kyung-Ho (Department of Architectural Engineering, Kyonggi University Graduate School) ;
  • Yoon, Hyun-Sub (Department of Architectural Engineering, Kyonggi University Graduate School)
  • Received : 2018.07.21
  • Accepted : 2019.07.30
  • Published : 2019.12.10
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Abstract

The objective of the present study is to examine the flexural behavior of two-span post-tensioned lightweight aggregate concrete (LWAC) beams using unbonded tendons and the reliability of the design provisions of ACI 318-14 for such beams. The parameters investigated were the effective prestress and loading type, including the symmetrical top one-point, two third-point, and analogous uniform loading systems. The unbonded prestressing three-wire strands were arranged with a harped profile of variable eccentricity. The total length of the beam, measured between both strand anchorages, was 11000 mm. The test results were compared with those compiled from simply supported LWAC one-way members, wherever possible. The ultimate load capacity of the present beam specimens was evaluated by the collapse mechanism of the plasticity theorem and the nominal section moment strength calculated following the provision of the ACI 318-14. The test results showed that the two-span post-tensioned LWAC beams had lower stress increase (Δfps) in the unbonded tendons than the simply supported LWAC beams with a similar reinforcement index. The effect of the loading type on Δfps and displacement ductility was less significant for two-span beams than for the comparable simply supported beams. The design equations for Δfps and Δfps proposed by ACI 318-14 and Harajli are conservative for the present two-span post-tensioned LWAC beams, although the safety decreases for the two-span beam, compared to the ratios between experiments and predictions obtained from simply supported beams.

Keywords

Acknowledgement

Supported by : National Research Foundation of Korea (NRF)

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (No. NRF-2017R1A2B3008463) and Basic Science Research Program through NRF funded by the Ministry of Science, ICT & Future Planning (No. 2015R1A5A1037548).

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