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ARCH5023/ARCH4333 - ARCHITECTURAL STRUCTURES I

][ STEEL STRUCTURES ][
THE UNIVERSITY OF OKLAHOMA - COLLEGE OF ARCHITECTURE
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STEELL BEAMS DEFLECTION

OVERVIEW

						Beam Design
						   Deflection
					              P&A 278 - 285

Live load deflection max. = L/360

greater deflection may cause:	
				floor cracks
				ceiling cracks
				cracked windows
  
Deflection often governs over
				bending
				shear

Total deflection = sum of individual deflections

Methods:					  
		1. D = 5/384 * W*L*L*L / E* I	Formula
		2. Graph figure 9.1 P&A 280
		3. Safe Load table 9.2 P&A 282-284

METHODS

1. Formula:

D = 5/384  x  [W x L x L x L  /  (E x I)]
D = maximum deflection in inches
W = total uniformly distributed load in pounds or kips
L = Length of the span in inches
E = modulus of elasticity of the beam in psi or ksi
       (for structural steel E= 29,000,000 psi)
I = moment of inertia of the cross section of the beam in inches to the fourth power

2. Graph:

Figure 9.1 P&A 280

graph can be used for:
1. uniformly loaded simple span beam
2. with fixed value for maximum bending stress
3. A 36 steel
4. 24 ksi maximum bending stress

D = (0.02483 x L x L ) / d

D = maximum deflection in inches
L = span length in feet
d = beam depth in inches