Based on the active variable stiffness, a new semi-active control method, whose principal content is using frequency control (FC), is presented. As a new semi-active algorithm, short time maximum entropy analysis is firstly proposed and the exact time and frequency signal at every control short time sequence also is given. The calculation results of a case of a 40-story building showed that the FC method is more effective than the results calculated by the method in the current structural design of tall buildings. The robustness of the algorithm is obtained and the displacement of the structure is reduced effectively.

Concrete filled tubular columns are widely used all over the world, due to their significant advantages, including attractive appearance, structural efficiency, reduced column footing, fast construction and high fire resistance without external fire protection. An experimental study has been carried out on the performance of joints between steel beams and concrete filled tubular columns in simple construction under fire conditions. The failure modes of the test specimens were always in the joint regions. Therefore, if the joints are appropriately designed and protected so that they possess sufficient strength, it is possible for the steel beam to develop catenary action and survive very high temperatures even without fire protection.

The physico-chemical characterization of two types of alkali lignin from different origin, namely L1 and L2, were studied by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectrometry (1H NMR) and gel permeation chromatography (GPC) analysis. FT-IR spectra show that they have the characteristics of absorption peaks of syringyl and guaiacyl. 1H NMR spectra indicate that acetylated L1 exhibits higher content of aromatic protons than L2, as the former is mainly composed by G units. L2 presents high quantities of methoxyl groups. GPC results show that L1 has much higher weight average than L2. They had similar functional groups, however, there were differences in the relative contents of functional groups.