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Wang Y.,Tsinghua University | Zhou H.,Tsinghua University | Shi Y.,Tsinghua University | Wu Y.,Capital Engineering and Research Incorporation Ltd.
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2013

An evaluation approach based on crack extension resistance curves was developed to accurately predict fractures of steel structural components. The crack extension resistance curve parameters for structural steels were calibrated using data regression and theoretical analyses based on crack tip opening displacement (CTOD) tests at low temperature carried out earlier by the authors. The crack extension resistance curves are then related to the fracture modes of steel components with cracks. The results indicate that steel components with crack lengths longer than the critical size having a positively sloped crack extension resistance curve in steel material toughness will fracture in the ductile mode while those with crack lengths shorter than the critical size having a positively sloped resistance curve or having a horizontal resistance curve will fracture in the brittle mode. The crack extension length corresponding to the maximum load calculated by this theoretical model agrees well with the test results, validating that the theoretical analysis is accurate and can be applied in fracture resistant designs of steel structural components. Source

Cao H.,Tongji University | Cao H.,Capital Engineering and Research Incorporation Ltd. | Quan Y.,Tongji University | Gu M.,Tongji University
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2014

The mechanism of aerodynamic damping in cross-wind is very complicated. No widely adopted theory and sophisticated method are available up to date, with no relevant guidelines in the load standards and codes in most countries. In order to investigate the effects of roughness exposure, aspect ratio and side ratio on across-wind aerodynamic damping ratio, the random decrement technique is used to evaluate across-wind aerodynamic damping ratios from wind-induced acceleration responses of 15 aeroelastic models. The evaluated results are compared with previous research achievements. The characteristics of across-wind aerodynamic damping ratio of rectangular high-rise buildings are studied. Results indicate turbulence intensity and side ratio are the most important factors affecting across-wind aerodynamic damping ratio. Aspect ratio indirectly affects aerodynamic damping ratio through making change of response amplitude. For the variation rule of aerodynamic damping ratio with reduced wind velocity, both of the magnitudes of positive and negative peaks decrease as turbulence intensity increases. Meanwhile, reduced wind velocity, from which aerodynamic positive damping ratio changes to negative damping, increases as turbulence intensity increases. Side ratio has significant influence on across-wind aerodynamic damping ratio, and completely different tendency are observed for B/D<1, B/D=1 and B/D>1. According to the database, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low reduced velocities for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and lateral turbulence intensity varying from 0.67% to 17.06%. Source

Cao H.-L.,Tongji University | Cao H.-L.,Capital Engineering and Research Incorporation Ltd. | Quan Y.,Tongji University | Gu M.,Tongji University
Gongcheng Lixue/Engineering Mechanics | Year: 2013

In order to study the effects of chamfered, slotted, and tapered cross-sections on across-wind aerodynamic damping ratio of super-high-rise building, 10 aeroelastic model tests were conducted in the TJ-1 wind tunnel at Tongji University. The random decrement technique was used to evaluate across-wind aerodynamic damping ratios. The accuracy of the evaluated results was verified through comparison with previous research achievements. Results indicated that modifications of cross-sections are not always effective in suppressing the aerodynamic effects of tall buildings. Chamfer ratios from 5% to 20%, slot ratios from 5% to 10%, and taper ratio of 1% significantly decrease the magnitudes of absolute aerodynamic damping ratios. Slot ratio of 20%, and taper ratios from 3% to 5% increase wind-induced responses through changing the aerodynamic damping ratios. Based on the findings, empirical aerodynamic damping function parameters are fitted for aerodynamic damping ratios of high-rise buildings with aerodynamically modified square cross-sections at low reduced wind velocities. Source

Peng Q.,China Electric Power Research Institute | Li J.,China Electric Power Research Institute | Bian P.,China Electric Power Research Institute | Kang D.,China Electric Power Research Institute | Shan Z.,Capital Engineering and Research Incorporation Ltd.
Dianwang Jishu/Power System Technology | Year: 2010

Advantages and disadvantages of three existing methods to calculate lightning shielding failure are analyzed. The electrical geometry model method is improved to solve the coordinates of intersection point of striking distance curves while the incident direction of is perpendicular to ground; according to the change of incidence angle of lightning current, then the intersection point is mapped to different geometric spaces; and then based on actual striking distance curves the coordinates of intersection point are modified to solve the trip-out rate due to lightning shielding failure. Calculation results show that the improved electrical geometry model method is more accurate than traditional methods. Finally, applying the improved method the influences of ground wire protection angle, tower height, cross arm length of middle phase and layer space on lightning shielding failure-caused trip-out rate of 1000 kV power transmission line are analyzed. Source

Wenyu D.,Capital Engineering and Research Incorporation Ltd. | Haibo Y.,The MCC Group
2015 International Conference on Logistics, Informatics and Service Science, LISS 2015 | Year: 2015

Based on geological predictions of 21 tunnels on the Baise-Jingxi Freeway, this paper systematically analyzes and summarizes the performance of a combined use of three geophysical techniques (tunnel seismic prospecting (TSP), geological radar, and infrared exploration of water). Furthermore, two successful prediction examples were used to elucidate the application of the integrated geological prediction. The results indicated that, based on geophysical analysis, rational combinations of different geophysical techniques are more effective and accurate because each of them utilizes different principles and has its own merits. The statistical data of the geological predictions of the Bai-Jing Freeway verified the superior performance of the proposed approach. The prediction of faults and joint zones has an accuracy of approximately 72-90%. For karst caves, underground rivers and karst conduits, the accuracies are mostly in the range of 60-80%. The interpretation of surrounding rock classification can reach an accuracy of 80%. © 2015 IEEE. Source

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