The wind pressure characteristics on a saddle roof at wind direction along the connection of the low points are systematically studied by the wind tunnel test. First, the distributions of the mean and the fluctuating ...The wind pressure characteristics on a saddle roof at wind direction along the connection of the low points are systematically studied by the wind tunnel test. First, the distributions of the mean and the fluctuating pressures on the saddle roof are provided. Through the wind pressure spectra, the process of generation, growth and break down of the vortex on the leading edge is presented from a microscopic aspect and then the distribution mechanism of the mean and fluctuating pressures along the vulnerable leading edge is explained. By analysis of the wind pressure spectra near the high points, it can be inferred that the body induced turbulence reflects itself as a high-frequency pressure fluctuation. Secondly, the third-and fourth-order statistical moments of the wind pressure are employed to identify the non-Gaussian nature of the pressure time history and to construct an easy tool to localize regions with a non-Gaussian feature. The cause of the non-Gaussian feature is discussed by virtue of the wind pressure spectra. It is concluded that the non-Gaussian feature of the wind pressure originates from the effects of flow separation and body-induced turbulence, and the former effect plays an obvious role.展开更多
The proliferation of Hoek-Brown nonlinear failure criterion and upper bound theorem makes it possible to evaluate the stability of circular tunnels with an original curved collapsing mechanism. The arch effect of shal...The proliferation of Hoek-Brown nonlinear failure criterion and upper bound theorem makes it possible to evaluate the stability of circular tunnels with an original curved collapsing mechanism. The arch effect of shallow circle tunnel is not taken into consideration so that the mechanical characteristics can be easily described. Based on the mechanism, the upper bound solution of supporting pressure of tunnels under the condition of surface settlements and overloads on the ground surface is derived. The objective function is formed from virtual work equations under the variational principle, and solutions are presented by the optimum theory. Comparisons with previous works are made. The numerical results of the present method show great agreement with those of existing ones. With regard to the surface settlement and overloads, the influence of different rock parameters on the collapsing shape is analyzed.展开更多
基金The National Natural Science Foundation of China (No.50678036)Jiangsu Civil Engineering Graduate Center for Innovation and Academic Communication Foundation
文摘The wind pressure characteristics on a saddle roof at wind direction along the connection of the low points are systematically studied by the wind tunnel test. First, the distributions of the mean and the fluctuating pressures on the saddle roof are provided. Through the wind pressure spectra, the process of generation, growth and break down of the vortex on the leading edge is presented from a microscopic aspect and then the distribution mechanism of the mean and fluctuating pressures along the vulnerable leading edge is explained. By analysis of the wind pressure spectra near the high points, it can be inferred that the body induced turbulence reflects itself as a high-frequency pressure fluctuation. Secondly, the third-and fourth-order statistical moments of the wind pressure are employed to identify the non-Gaussian nature of the pressure time history and to construct an easy tool to localize regions with a non-Gaussian feature. The cause of the non-Gaussian feature is discussed by virtue of the wind pressure spectra. It is concluded that the non-Gaussian feature of the wind pressure originates from the effects of flow separation and body-induced turbulence, and the former effect plays an obvious role.
基金Project(2013CB036004)supported by the National Basic Research Program of ChinaProjects(51178468,51378510)supported by the National Natural Science Foundation of China
文摘The proliferation of Hoek-Brown nonlinear failure criterion and upper bound theorem makes it possible to evaluate the stability of circular tunnels with an original curved collapsing mechanism. The arch effect of shallow circle tunnel is not taken into consideration so that the mechanical characteristics can be easily described. Based on the mechanism, the upper bound solution of supporting pressure of tunnels under the condition of surface settlements and overloads on the ground surface is derived. The objective function is formed from virtual work equations under the variational principle, and solutions are presented by the optimum theory. Comparisons with previous works are made. The numerical results of the present method show great agreement with those of existing ones. With regard to the surface settlement and overloads, the influence of different rock parameters on the collapsing shape is analyzed.
