In this study, aerodynamic coefficients of single and 4 bundled ice-accreted conductors are investigated using LES turbulence model and compared with the results of the wind tunnel test. Single conductors with span length L=1D and 10D are simulated, and predicted aerodynamic coefficients with span length L=10D show favorable good agreement with the experiment within the estimated error range of the wind tunnel test. A systematic error estimation using the models with L=2D, 3D, and 6D is conducted and shows that the span length L=10D is long enough to predict aerodynamic coefficients. The effect of the accreted ice height, H, on aerodynamic coefficients is investigated. It is found that negative pressure at lower face near the leading edge significantly affects CL and CM and causes maximum absolute value of CL and CM at 12° for the conductor with H=1D and at 16° for the conductor with H=0.5D. The wake effect of 4 bundled conductors is also investigated by the analysis of aerodynamic coefficients and pressure distribution for each conductor. The wake of windward conductors gives significant impact on CL and CM. Correction coefficients for leeward conductors are proposed to account for the wake effect, and the result shows favorable good agreement with predicted aerodynamic coefficients of 4 bundled conductors.
This paper describes investigation results on damage to building structures in/around Tacloban, Leyte, Philippines due to Typhoon Haiyan which occurred off the eastern coast of Leyte on 4/November/2013. Wind speeds at the investigated area are estimated from several damage samples, because the peak gust released by Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) seemed to be lower because of damage to meteorological instruments. Consequently, the wind speed estimated at Tanauan, Leyte attained to about 70 m/s. Moreover, typical constructions and damage observed at the investigated area are summarized to suggest a strategy to mitigate future disasters. Damage to structures might become more severe due to existences of jalousie window and/or ventilating louver which were commonly implemented in buildings in Philippines. Progressive collapses also seemed to happen in several damaged structures.
Downburst produces strong winds near ground and causes severe damage to buildings and people. However, few studies have focused on the downburst flow field and downburst-induced loads on buildings. Thus, the present study attempts to understand the characteristics of downburst and its effects on buildings, based on experiment and numerical simulation. An experimental facility generating a pulsed wall jet has been developed. Large eddy simulation (LES) has also been conducted. First, the unsteady downburst flow field was simulated and compared with the experimental results to validate the Computational Fluid Dynamics (CFD) modeling. Then, a simulation of non-isothermal flow was conducted to understand the characteristics of practical downbursts. Based on the results of experiment and CFD simulation, the characteristics of downburst-induced wind loading on a square building were investigated. Finally, a discussion was made of the evaluation of the design wind loads for downbursts.