| There formed a new type of brace resistant steel frame called eccentrically braced semi-rigid steel frame, which combines eccentrically braces and steel frames with semi-rigid connections. On the one hand, this is an improvement and development of the existing structural system. Eccentrically braces can make up the deficiencies of semi-rigid steel frames, increase the elastic stiffness of semi-rigid steel frames, reduce the lateral, solve practical engineering problems and expand the use of semi-rigid steel frames. On the other hand, it should have a superior seismic performance by combining the two systems of strong energy dissipation capacity respectively. Meanwhile, this is also a useful attempt to explore the ideal seismic system. Dynamic characteristics of structural system, which include cycle, frequency, damping and so on, are the basic parameters of structural dynamic analysis and the basis for seismic design.This paper mainly analyzed the dynamic characteristics of eccentrically braced semi-rigid steel frames. Study included dynamic behavior tests and finite element analysis. The latter was the primary part. The former was adjunctive part, and was used to verify the reliability of the latter.The dynamic behavior tests are V-shaped eccentrically braced steel frames and V-shaped eccentrically braced semi-rigid steel frames. Results of the experiment shows that the first frames will complete the absorption of seismic energy quickly because of the big stiffess. In contrast, the semi-rigid frames have a lower stiffness and larger period. The calculation of vibration period for the frames with counterweight is in line with the empirical formula of standard.The finite element analysis was completed with ANSYS. Chevron eccentrically braced semi-rigid steel frames would be studied in this paper. The major factors, such as, rotation stiffness of frame connections, support types and layouts, energy-beam lengths, span and layer numbers, stiffener spacings were considered during analysis. More than 200 species of 4 series were computed. Calculation shows that:Increase the stiffness of frame connections caused that the the structure stiffness increased and the period reduced. Structural natural penod is increasing with the increases of energy-beam lengths, span and layer numbers of frames. The rotation stiffness of frame connections has less effect on smgle-span specimens and has significant effect on multi-span specimens. Cycle support types has no effect on the structure. It should choose the support of homogeneous symmetric layout.Based on the results of tests and analysis, it could sum up that multi-span chevron eccentrically braced semi-rigid steel frame was a good seismic system. Meanwhile, the formula for calculating the vibration period of the chevron eccentrically braced semi-rigid steel frame was proposed. It could be referenced for relative design and study. |
