Experimental study of the Cyclic behavior of semi-precast connection in concrete frames with coupler and high strength reinforcement

Document Type : Original Research

Authors
R. Vahdani 1
A. Kheyroddin 2
M. Heravi 3
1 Assistant Professor, Faculty of Civil Engineering, Semnan University
2 Professor, Faculty of Civil Engineering, Semnan University
3 PhD student in civil engineering, Semnan University
10.22034/24.1.39
Abstract
The four experimental samples of middle beam-column connection of the reinforced concrete moment resisting frame were made. In the stage of making the experimental specimens, the two main differences between the specimens were included the strength category of reinforcement and the semi-precast of connection. The two monolithic specimens (MO1 & MO2) were made using in-situ and continuous concreting in such a way that the reinforcement and concreting of the beam and column and the connection core were all done in one step; Two other specimens are semi-precast connection (SPC1 & SPC2). The semi-precast connection is built in such a way that coupler is used and does not require welding on the project site. In one of the monolithic specimens (MO1) is used S400 grade reinforcement, and in the other monolithic specimen (MO2) is used S500 grade reinforcement. In one of the semi-precast specimens (SPC1) are used S400 grade reinforcement, and in the other semi-precast specimen (SPC2) is used S500 grade reinforcement. In all of the four specimens, the cross-section of the column is square with dimensions of 30 cm; and the cross-section beams in all specimens is rectangular with a width of 30 cm and a height of 35 cm. In all specimens, 8 reinforcements with a diameter of 16 mm with uniform distribution in the column section are used for the longitudinal reinforcement of the column; The longitudinal reinforcement of the beams includes 4 reinforcements with a diameter of 16 mm at the bottom of beam and also 4 reinforcements with a diameter of 16 mm at the top of beam; reinforcements with a diameter of 10 mm have used for shear reinforcement in beams and columns; The shear reinforcements of column continue in the connection core. In the monolithic specimens, the bottom longitudinal reinforcements of the beam have continuously passed through the beam-column connection core, while in the two semi-precast specimens, the bottom longitudinal reinforcements of the beam have coupler in the connection core. Tests to determine the compressive strength of used concrete as well as tests to determine the tensile strength of used reinforcements have been done. After making and curing of specimens, cyclic load was applied according to ACI T1.1R-01; then parameters such as yield strength, ultimate strength, ductility and absorbed energy have been studied. In the range of variable parameters and materials used in this research, it is concluded that increasing in the strength of reinforcements has resulted in increasing the yield strength and ultimate strength of specimens; In such a way that the strength of monolithic specimens is increased by +8% and the strength of semi-precast specimens are increased by +32%. Increasing the strength of reinforcements has reduced the ductility of monolithic specimens by -36%. Increasing strength of reinforcements has resulted in decreasing the absorbed energy -18% of monolithic specimens and -15% of semi-precast specimens. The yield strength and ultimate strength of semi-precast specimens are smaller than monolithic specimens. When the S400 reinforcement is used on the specimens, the yield strength and ultimate strength of the semi-precast specimen is 23% smaller than and the ductility ratio is 28% smaller than the monolithic specimen. The energy absorbed in the semi-precast specimen is 28% smaller than it in monolithic specimen.

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Modares Civil Engineering journal
Volume 24, Issue 1
March and April 2024
Pages 39-52