Author: Weng, Kefan
Title: Flexural behavior of ECC-Steel Plate-UHPC hybrid member
Advisors: Dai, Jian-guo (CEE)
Degree: M.Sc.
Year: 2019
Subject: Composite construction
Steel, Structural
Concrete construction
Tunnels -- Design and construction
Hong Kong Polytechnic University -- Dissertations
Department: Department of Civil and Environmental Engineering
Pages: xi, 75 pages : color illustrations
Language: English
Abstract: Comprehensive utility tunnel is becoming more and more important in China's urban construction, but there are few researches on the mechanical properties of comprehensive utility tunnel. This paper proposes a new concrete composite utility tunnel concrete structure system, which combines open-hole steel and ultra-high-performance green concrete to develop a new prefabricated underground utility tunnel. The use of the open-hole steel plate as the force-receiving rib of the underground utility tunnel can avoid the difficulties in the production process of the steel mesh in the conventional prefabricated reinforced concrete underground utility tunnel and gives the structure better strength and ductility. At the same time, ultra-high-performance green concrete (UHPC and ECC) with different functions are used as the internal fireproof and external durability protection materials for the open-hole steel. The easy-opening characteristics of the steel plate are used to realize the integration of the inner and outer high-performance concrete and reduce the structural weight. Focusing on the research content of the prefabricated composite utility tunnel structure, this topic carries out two main aspects of research. (1) preparation and research mechanical properties of ultra-high performance green concrete materials for comprehensive utility tunnel; (2) design, analysis and construction and construction of curved parts and overall structures of comprehensive utility tunnel. From the research, some conclusion could be drawn. (1) All the four flexural specimens underwent three stages of cracking, stiffness degradation and specimen failure in the whole process of loading. With the increase of vertical load, the crack occurs at the middle bottom of the span. With the increase of cracks, the deflection of the middle and bottom of the span increases, and the cracks develop in the area between distributed beams. The ultimate failure mode is the interface separation caused by the crack expansion along the middle span of the shear steel plate, which makes the concrete and steel plate cannot work together and lose the structural bearing capacity. (2) Due to the poor ductility and tensile strength of concrete, the bearing capacity of plain concrete specimens is significantly lower than that of the other three groups of specimens using fiber concrete. The use of ECC and UHPC improves the flexural capacity of the structure and significantly increases its ductility. Therefore, the control of crack width in the current code is not applicable to this new hybrid structure. (3) It can be found that the concrete shear bolt can significantly improve the ductility of the members by comparing the specimens with 12% steel plate opening ratio and 25% steel plate opening ratio when fiber concrete is added. (4) By comparing the two groups of specimens with 25% opening ratio of steel plate added with fiber concrete, which conducted positive bending test and negative bending test respectively, it can be found that the use of UHPC can meet the bearing capacity requirements of bearing area with negative bending moment, but it is smaller than ECC in terms of bearing capacity. Therefore, it is reasonable for the structure to adopt UHPC in the compression zone and ECC in the bending zone to conform to the idea of functional gradient design.
Rights: All rights reserved
Access: restricted access

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