For the warehouse shown below: 1- Design a typical one foot strip spanning verti
ID: 1844787 • Letter: F
Question
For the warehouse shown below:
1- Design a typical one foot strip spanning vertically between the window openings of the South wall to resist wind loads in the N-S direction in addition to gravity load from the roof plus its own self-weight. Assume wall is simply supported at top and bottom. Consider both external pressure and internal suction. Also, consider roof uplift.
2- Design the pier of the East wall to carry lateral wind loads in the N-S direction plus wall self-weight. Consider cantilever piers and ignore axial load from the roof. Note : For calculating lateral wind loads, consider external pressure on windward walls and external suction on leeward walls. No internal pressure.
Data:
-Building is located in suburban Philadelphia and is partially enclosed. Exposure B. V=90 mph
-Fully grouted construction. 8” concrete blocks with 3000 psi compressive strength, Type S mortar and Grade 60 steel
-Steel joist roof spanning N-S and bearing on North and South walls. Roof dead load = 60 psf
?Problem from -- Introduction to Structural Design Assignment # 5 : Design of Reinforced Masonry Structures?
Explanation / Answer
Velocity we have, V = 90mph
Compressive stregnth = 3000psi
type S grade 60 steel
Roof dead load = 60psi
1. external wind pressure on warehouse from N-S direction,(psf) =.00256 x V2
wind pressure = .00256 x (90)2
= .00256 x 8100
external wind pressure = 20.73 psi
internal suction Cpi = Cpl+a2Cpw /1+a2
=> a Aw/Al Aw = wall porosity x windward area / Al = wall porosity x leeward area
as given
= (0.7 x 0.8) / (0.7 x 0.1)
= 0.56 / 0.07 = 8
a = 8
Cpl = external pressure on leeward side
= 20.73x0.1 = 2.07psf
Cpw =external pressur on windward side
20.73 x 0.8 =16.58psf
Cpi = Cpl + a2Cpw / 1+a2
= 2.07+(8)2(16.58) / 1+(8)2
= 2.07+64 x 16.58 / 1+64
2.07 + 1061.1 / 65
1063.1/65 = 16..35
internal pressure = 16.35psi
roof uplift pressure = 0.00256(Kh)(Kzt)(Kd)(v)2 I
= 0.00256 (20.73)(16.58)(10)(90)2 x18
= (0.00256x3437) x (8100x18)
= 8.79x145800
=1281582psf =8899.8psi
roof uplift = 8899.8psi
2. lateral wind load =
F= a x P x cd x Kz x Gh (a = area , P = pressure , cd = drag cofficient Kz = velocity exposure cofficient , Gh = gust response factor)
area of rectangular warehouse = Lw
= area ,a = 16x42= 672'
Gh = 65+60 / (h/33)1/7
= 125 / (18 /33)1/7
= 125/(0.54)1/7
= 125 /0.07 = 1785.7
F= 672 x 20.73 x 0.7 x 0.55 x 1785.7 (Kz is given)
lateral wind load ,F = 9577183.3kn/m2 => 1389053psi
wind load = 1389053psi