Q4. Now you wish to investigate whether the timber glulam portal frame option sized in assignment 4 would be stiff enough. As such, use the equation above to check whether a 765mm x 120mm wide glulam beam section would be stiff enough to limit the lateral drift of the building (lateral displacement at top of columns divided by the column height) to H/500 for an SLS lateral wind load of W = 15kN (per portal frame)? Assume that the glulam section will be made with GL12 timber and you can assume that the same glulam section will be used for both the columns and beams (i.e. I_b = I_c).  Note that glulam material properties from AS NZS1720.1 are shown below. Note also, if required, that the load duration deformation modification factors (j₂ and j₃) for glulam are the same as those for sawn timber (reported in Table 2.3 of reader). Report the ratio of the displacement demand to the displacement limit in %.