Techno Press
Techno Press

Steel and Composite Structures   Volume 29, Number 1, October10 2018, pages 125-138
Simplified stress-strain model for circular steel tube confined UHPC and UHPFRC columns
An H. Le, Fehling Ekkehard, Duc-Kien Thai and Chau V. Nguyen

Abstract     [Full Text]
    The research on the confinement behavior of ultra high performance concrete without and with the use of steel fibers (UHPC and UHPFRC) has been extremely limited. In previous studies, authors experimentally investigated the axially compressive behavior of circular steel tube confined concrete (STCC) short and intermediate columns with the employment of UHPC and UHPFRC. Under loading on only the concrete core, the confinement effect induced by the steel tube was shown to significantly enhance the utimate stress and its corresponding strain of the concrete core. Therefore, this paper develops a simplified stress – strain model for circular STCC columns using UHPC and UHPFRC with compressive strength ranging between 150 MPa and 200 MPa. Based on the regression analysis of previous test results, formulae for predicting peak confined stress and its corresponding strain are proposed. These proposed formulae are subsequently compared against some previous empirical formulae available in the literature to assess their accuracy. Finally, the simplified stress . strain model is verified by comparison with the test results.
Key Words
    UHPC; UHPFRC; steel tube; STCC columns; confinement effect; stress-strain model
(1) An H. Le:
Division of Construction Computation, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
(2) An H. Le:
Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam;
(3) Fehling Ekkehard:
Faculty of Civil and Environmental Engineering, Institute of Structural Engineering, University of Kassel, Germany;
(4) Duc-Kien Thai:
Department of Civil and Environmental Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul, 143-747, South Korea;
(5) Chau V. Nguyen:
Institute of Research and Development, Duy Tan University, 03 Quang Trung, Danang, Vietnam.

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