Impact Behavior of Unbonded Post Tensioned Concrete Beams under Drop Weight Loading

Abstract

This research investigates the impact behavior of unbonded post-tensioned concrete members (PT-RC). Both an experimental and numerical study was carried out to examine the effect that the post-tensioning force, Ppt, has on the member capacity and observed failure mechanisms. First, a thorough literature review was done to highlight both the state of the art of experimental studies and also substantiate the use of nonlinear finite element dynamic analysis (NLFEDA) methods for modeling of concrete members under impact. The findings of literature review were then used to develop an applicable testing matrix to highlight the analysis of PT-RC members under varying degrees of shear and flexural strength. A total of fifteen specimens were cast; thirteen PT-RC members in addition to two conventional reinforced (RC) members. All specimens had identical longitudinal reinforcement, but varying shear reinforcement ratios designed to be both flexural- and shear-deficient in static conditions according to the ACI code (318-19). A drop weight testing apparatus was used for all impact tests, in which a weight of considerable mass was dropped at the midspan in simply supported conditions and compared with. The main variables investigated include: the designation of shear and flexural specimens, as previously noted; increasing levels of effective prestress; and the application of two different impact energies per each specimen type, shear- or flexural-deficient. The test results showed that the levels of PT force and shear reinforcements of the specimens played an important role in their overall behavior and impact capacity. Lastly, the use of NLFEDA methods has been established to provide agreeable results with that of the experimental for unbonded PT-RC members impacted at varying levels of impact energy.

이 연구는 비부착 포스트텐션 콘크리트의 내충격 거동에 관한 연구이다. 포스트텐션 인장력이 거동에 끼치는 영향과 파괴 양상을 분석하기 위해, 실험 및 해석적 연구가 수행되었다. 총 15개의 실험체를 제작하였으며, 그 중 13개는 비부착 포스트텐션 보 실험체, 나머지 2개는 일반 철근콘크리트 보 실험체이다. 모든 실험체는 동일한 종방향 철근이 배근되었으나, 다양한 전단철근비를 가지도록 설계하였다. 최종적으로 자유낙하실험 및 비선형유한요소 동적해석, 그리고 다양한 변수해석을 통하여 비부착 포스트텐션 콘크리트 보의 내충격 관련 제안식을 제안하였다.