SUMMARYAcross-wind aerodynamic damping ratios are determined from the wind-induced acceleration responses of 10 aeroelastic models of square super high-rise buildings in an urban flow condition (exposure category C in the Chinese code) using the random decrement technique. Moreover, the influences of amplitude-dependent structural damping ratio on the estimation of aerodynamic damping ratio are discussed. The validity of estimated damping is examined through a comparison with previous research achievements. On the basis of the estimated results, the characteristics of the across-wind aerodynamic damping ratios of modified square high-rise buildings are studied. The effects of aerodynamically modified cross-sections, such as chamfered, slotted and tapered cross-section, on the across-wind aerodynamic damping ratio are investigated. The results indicate that modifications of cross-sections are not always effective in suppressing the aeroelastic effects of super high-rise buildings. Low corner-cut ratios (chamfer ratios from 5% to 20% and slot ratios from 5% to 10%) and low taper ratio (1%) significantly decrease the magnitudes of absolute aerodynamic damping ratios. However, large modifications of cross-sections (slot ratio of 20% and taper ratios from 3% to 5%) increase wind-induced responses by changing the aerodynamic damping ratios. According to the database, empirical aerodynamic damping function parameters are fitted for high-rise buildings with aerodynamically modified square cross-sections.

According to the analysis of casing deformation events and the achieved micro-seismic data in four shale gas wells, the slip of the fault is treated as the main reason for casing deformation problems in shale gas wells in Changing. Analytical model for calculating fault slippage is established based on elastic mechanics and the slippage of faults around 4 shale gas wells is calculated. The calculated results show that both the height of fault reactivation area and the angle between the maximum in-situ stress and fault have significant effect on the fault slippage. The location of the intersection point where casing goes through the reactivation area of fault can significantly affect the casing deformation. The closer the intersection point is to the center of reactivation area, the larger fault slippage and the serious casing deformation occurs. Case study in well Ning201-H1 shows that the slippage of fault at total depth 3490 of this well is 30.5mm, and the corresponding casing deformation is 10.5mm which is in agreement with field data. The casing deformation in drilling platform H19 is much more serious due to the extremely complicated faults and the large reactivation area. The maximum casing deformation reaches 35mm in well H19-5. The results of this study have significant reference value for understanding the mechanism and controlling methods for casing deformation in shale gas wells during hydraulic fracturing treatment.

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Aeolian vibration of transmission conductors could cause triggering off shares and broken due to fatigue damage and thus of concern. To ensure the safety of electrical transmission systems, mitigation devices are usually installed on the conductors to suppress the aeolian vibration. This paper investigates effects of three types of such devices on bundled conductors experimentally, including spacer dampers, damping lines and stockbridge dampers. For this purpose, vibration tests of twin and four bundled conductors were designed and carried out according to IEEE standards. Firstly, the vibration characteristic of the twin bundled conductors equipped with the spacer damper and stockbridge damper were tested with different installation configuration of wire damper sets. The vibration tests of four bundled conductors were also carried out, and the energy dissipation power calculation of spacer damper has been given. The calculation method of energy dissipation power calculation of spacer damper can reflect the properties of the energy dissipation and the method is proven to be reasonable according to the test.