In general, the bearing capability is strength capability for mirco-pile. The stability bearing capability for mirco-pile with concrete-filled steel tubular becomes important in reinforced building foundation. The theory of buckling stability is applied to study the bearing capability of mirco-pile. According to the character of concrete filled steel tubular, the Euler force and the friction between pile and soil are combined for the buckling bearing capability of mirco-pile with concrete-filled steel tubular. The equation of mirco-pile with concrete-filled steel tubular is confirmed by some test data and numerical simulation. The slenderness ratio and material strength took great effects on the bearing capability of mirco-pile with concrete filled steel tubular. The equation on bearing capability mirco-pile with concrete filled steel tubular is applied for reinforce building foundation and referred to other application of concrete filled steel tubular.

The effect of SiO2 methyl modification (CH3-NS) on various properties of the nondispersible underwater concrete (UWC) was evaluated. The fluidity and antiwashout resistance of the UWC mixture were evaluated by various tests. Concrete specimens were designed in the two different damage states, i.e., P-type and Z-type. The compressive strength test, contact angle test, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) techniques were performed to analyze them. The experimental results showed that adding CH3-NS increased the fluidity of the UWC. When too much CH3-NS was added, the antiwashout resistance was reduced The CH3-NS doping should not exceed 3.0%. For P-type specimens, adding uncalcined CH3-NS improved the strength of the reinforced specimens compared to calcined CH3-NS, the value was 17.9%. And the peak and ultimate stresses of the specimens were shifted forward by 18.1 and 4.8%, respectively. The polar force component magnitude of the surface tension of the specimen was the major factor affecting the surface free energy of P-type specimens. Different CH3-NS statuses and the properties of specimens were the major factors affecting the surface free energy of Z-type specimens. Contact angle measurements, FTIR, and SEM showed that uncalcined CH3-NS enhanced the hydrophobicity and reduced the surface free energy while increasing the density of UWC and thus enhancing its compressive strength.

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In order to improve the seismic performance of high-rise buildings, a friction damper installation scheme was proposed in the paper. Through numerical simulation and experimental testing, the vibration reduction effect was compared and verified. Herringbone structure was applied to install friction damper in the bearing wall. Based on this vibration reduction scheme, the finite element model of high-rise building was established, and the influence of damper on the modal characteristics of building frame was analyzed. It can be known that the damper has little influence on the natural frequency, but has a great influence on the amplitude range of the excitation response. In the finite element model, two kinds of seismic waves were applied, the strength and dynamic response was simulated and calculated, and the maximum deformation and stress results were obtained. Compared with the initial model, it can be known that the more intense the vibration is, the more obvious the damping effect of the damper is. A seismic excitation simulation system based on acceleration sensor detection is designed and applied to the wall vibration test. The results show that the maximum vibration acceleration of the measured point is reduced by 26.3 % by the damper, and the stable seismic effect can still be maintained during the impact of extension. Compared with the traditional hardness and volume reinforcement scheme, the friction damper can reduce the production cost and improve the adaptability to seismic wave excitation, which provides an important basis for seismic research in other fields.

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