Hi Heng,

(1) Is this beam standing in the wind or is it inside a building? Because the aspect ratio is so high, 6 to 0.275 is about 22 to 1, what you have is more like a wing than a building. A small change in the angle of the wind will create large sideways forces. Also the sideways flexibility combined with the vortex shedding that may develop can set up an oscillation that will create large dynamic forces.

(2) How did you come up with the value of Pressure load due to wind.  Here is a Cornell University webpage.  Using such high aspect ratio might take this calculator out of its valid range, but anyway...150 mph is 241 km per hour.

Convert the maximum pressure of 62 psf and you get about 3,000 Pa, not 111,000 Pa.  How did you derive the value of pressure?