Research on Estimation Method of Deformation Capacity of Reinforced Concrete Encased Steel under Varying Axial Force and Bi-Axial Horizontal Force

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(1) PurposeIt aims at explaining the validity of a method to evaluate the deformation capacity of the steel framed reinforced concrete (abbreviated as SRC hereafter) beam-columns under varying axial force, on the basis of a method under constant axial force.(2) Research programThe static loading test of the SRC specimens were carried out under varying axial force or constant axial force. These specimens were subjected to the lateral force in the direction of the principal axis of the section or in the direction at 45 degrees. Furthermore, it was analyzed about the deformation capacity of the SRC beam-columns by the data including the experiment data from literature materials.(3) Result of researchFlexural yield occurred before shear failure in all specimens. The limit rotation angle^<*1)> in the case that N/Nu^<*2)> changed from 0.5 to -0.2 was about 7x10^<-2> radian, and a little poor in comparison with the case that N/Nu = 0.3 or N/Nu changed from 0.3 to -0.1. A lateral force condition didn't exert a great influence on the result of the experiment. The axial force ratio at the maximum strength under compressive axial force and the flexural strength ratio of the steel portion have a great influence to the limit rotation angle in the case of varying axial force. By modification of the appraisal method in the case of constant axial force, it could be mostly evaluated.Note:*1) The axial compressive strength superposing that of the steel portion and the RC portion.*2) The rotation angle of the member of which strength declines to 80% of the maximum strength.(4) SummaryIt has been shown that the deformation capacity of SRC beam-columns subjected to the varying axial force could be mostly evaluated by modifying the appraisal method in the case of the constant axial.