Study On Wind Carrier Coefficient Of Irregular Grille-type Engineering Structure

Because China's current code for load of building structures(GB50009-2012)does not provide a clear calculation method for the wind carrier type coefficient of "hollowed-out" grille structure,engineering designers often have to rely on wind tunnel tests or reduce the wind carrier type coefficient of non-porous structure when encountering such structures.On the one hand,the cost of wind tunnel test is high and the period is long.On the other hand,there is a lack of necessary theoretical basis for the use of reduction,and risks may exist.Therefore,based on CFD theory,this paper uses hydrodynamics analysis software to carry out systematic research on wind carrier type coefficient of grille-type structure.First,in order to verify the effectiveness of the numerical simulation method,the wind carrier type coefficients of the Texas tech university TTU model and high-rise building hole-opening model were numerically simulated and compared with the corresponding wind tunnel test results.On this basis,through a large number of multi-working condition simulation analysis,explore the porosity,pore shape,pore migration,pore thickness and other factors on the grid structure shape coefficient influence rule.Finally,a numerical wind tunnel simulation is carried out for the surface wind carrier coefficient of a large irregular statue structure against the background of practical engineering.Aiming at the backlight part of irregular curved surface,the difference between the estimated body shape coefficient and the numerical simulation result is compared and analyzed,and the design proposal is put forward for the reasonable value of wind carrier type coefficient of this kind of irregular grille structure.Through the above analysis and research,the main conclusions of this paper are as follows:(1)The shape coefficient of grille-structure can be calculated by net area or gross area,which can be converted by porosity.The variation range of shape coefficient calculated by net area is small,but the fluctuation is large.On the contrary,the shape coefficient calculated by the gross area can better reflect the "reduction" effect of porosity on the overall force.The relationship between the body type coefficient calculated by the gross area and porosity can be approximately expressed by a function,and it is better in the fitting of the hair type coefficient when using on the windward surface.(2)In general,the shape coefficient distribution on the windward surface does not change significantly with respect to the leeward surface under the influence of such factors as pore type,pore diameter and pore deviation.The most affected areas on the windward surface are the middle part of the plate,the bottom part of the plate and the edge of the hole.Under different parameters,the shape coefficients of the horizontal and vertical central axes of the windward surface do not change much.By contrast,the areas most affected by the leeward side are the perimeter of the plate and the location of the holes edge.(3)As the leading factor affecting the body shape coefficient,the downwind hair shape coefficient decreases by about 13% for every 10% increase in porosity.Under the same porosity,the extreme values of the strip holes are larger on the windward and leeward sides,but the overall shape coefficient of the round holes on the leeward side is larger,and the shape coefficient of the square holes in the downwind direction is larger.When the holes position and spacing are changed,the variation rule of shape coefficient is strong.As the thickness increases,the body shape coefficient on the windward side will increase slightly while that on the leeward side will decrease greatly.If the porosity remains unchanged,the overall reduction of the pore diameter will cause a sharp increase in the shape coefficient near the hole on the lower left side of the windward side,and the negative wind pressure on the middle part of the hole along the vertical axis of the leeward side will all increase.(4)The method of calculating the standard shape coefficient by using the dominant porosity,supplemented by the correction of pore shape,pore diameter,pore deviation and other factors,is also applicable to the irregular grille-type structure.Compared with the results of numerical simulation,the results agree well with each other.The influence factors of important buildings and complex structures in engineering are recommended to be appropriately adjusted to increase the safety of structures.