| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 107 === Abstract
Compared with the traditional reinforcement, the cost per unit strength of the seven-wire strand commonly found in the prestressed system is relatively low.If the unstressed seven-wire strand is used instead of the traditional reinforcement, the material cost of the overall reinforced concrete structure is expected to be reduced. Due to the lack of relevant test results at home and abroad, this study plans to understand the mechanical behavior of reinforced concrete columns with prestressed steel strands as the longitudinal reinforcement through test and analysis of the subsequent results.
In order to simulate the situation when column subjected to real seismic load, this study conducted a fixed axial force cyclic loading test in the Multi-Axial Test System (MATS) of the National Center for Research on Earthquake Engineering (NCREE). The design of the specimen can be divided into two parts: the flexural failure specimen and the shear failure specimen. A total of 14 large-scale specimens were subjected to the cyclic loading test. The design strength of the strand as longitudinal reinforcement is 1860 MPa,and the nominal yield strength of traditional longitudinal and horizontal reinforcement is 420 MPa. The experimental variables include the types of longitudinal reinforcement, the types of transverse reinforcement, the concrete strength, the axial force, and the limit state failure mode.
The experimental results showed that the ultimate flexural strength developed by the strand-flexure specimen during the cyclic loading exceeded the strength calculated according to the current code, and the strand-shear specimen also developed the shear strength lager than that calculated according to the current code.Whether the failure mode of the specimen is flexural failure or shear failure, the ultimate drift ratio and ductility of the strand column are close to those of the columns with traditional reinforcement.
Compared with the rectilinear hoop, the five-spiral can be used to increase the strength and the ultimate drift ratio of the strand column. Comparing the longitudinal reinforcement of all specimens at critical section with the same drift ratio of 1.5%, the strain of the steel strand is lower than the strain of the traditional reinforcement. Different concrete strength or different horizontal reinforcement types have little effect on the strain of the steel strand.Overall, the strand column had fewer cracks in the test than the traditional reinforced columns, and the energy dissipation capacity was lower than that of the traditional reinforced columns.
Considering that the unit strength cost of the Unstressed steel strand is lower than that of the traditional bar, and the seismic performance of the steel strand column is close to that of the traditional reinforcement column, it has potential for application. Therefore, this study also proposes the design method of steel-strand column according to the experimental results and with reference to the current codes.
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