| Framed tube and tube-in-tube structures are now widely accepted as economic solutions for tall building structures over a wide range of building heights. In this paper, three aspect research are done around the analysts of second-order effect and shear-lag effect on framed tube and tube-in-tube structures in highrise buildings by use of continuum method. The content as follows:Firstly, overall stability and second-order elastic analysis of framed tube structures in highrise buildings by use of the Rayleigh-Ritz energy method are presented in this paper. The basic equation of overall stability and second-order elastic analysis is set up by use of the Rayleigh-Ritz energy method. The influence of shear-lag effect on overall stability and second-order lateral deflections of framed tube structures are studied for the first time.Secondly, a method for the analysis of elastic seismic responses of framed tube structures in highrise buildings is presented in this paper. As an important task of elastic seismic response analysis for framed tube structures, the continuum analysis model is used to analyze the first-order and second-order elastic free vibration of framed tube structures for the first time. At first, the first-order elastic analytical differential equation for the transverse free vibration of framed tube structures is set up by use of the Hamilton's principle, and the method of separation of variables is employed to solve the problem, and the closed-form solutions of the first-order frequencies and mode shapes are given. The influence of shear-lag effect on the dynamic properties of framed tube structures is studied as well as. Then, the second-order equation of the free vibration of framed tube structures is set up by use of the Rayleigh-Ritz method, and the influence of second-order effect on the dynamic properties is studied also.Lastly, overall stability and second-order elastic analysis of tube-in-tube structures...
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