List of Sizes, Spans, Spacings, and Ratios (SS)

– Wood joists: 2×8, 2×10, 2×12 spaced 12, 14 or 16 inches apart
– Maximum slenderness ratio for column (l/r) is 50

– Deflection limit for steel members= L/360 for live load only
– General steel beam depth= 1/22 x span
– Depth to span ratio of joists is limited to 1/24
– For composite beam to be efficient= slab thickness of 4 to 5 1/2 inches
– Preferable maximum allowed radius of gyration(Kl/r) = 200

– Code specifies width b of T beam may not exceed 1/4 of span
– For T beam, in general d should be about 1.5 times b
– Net strain reinforcement must be greater than or equal to 0.004
– For Tensile reinforcements, code requires a maximum spacing between bars on the main reinforcement for bending to be 3 times slab thickness or 18 inches, whichever is smaller
– For compressive reinforcements, ties must be at least #3 in size, at spacing less than 16 times the diameter of the longitudinal bars or 48 times the diameter of the tie bars
– Minimum size of spiral reinforcement is 3/8 inch
– Clear spacing between spirals must be between 1 to 3 inches
– Reinforcing bars with strengths of 40, 60 and 75psi are common

– Common 2×4 studs places 16 inches on center

– Bar spacing about 18 to 36 inches

– Wind tunnel test: for buildings with height to width ratio > 5:1, or taller than 400′
– Staggered truss is good for buildings at least 8-10 stories tall, with spans larger than 45′
– Optimum depth to span ratio for truss is 1:10
– Span to depth ratio for diaphragms: 4:1
– For wind force, drift should be limited to 1/500 of building’s height, and drift between adjacent stories should be limited to 0.0025 times story height
– Removal and compaction of fill for foundation is usually economical up to 6 feet
– Base isolation is most effective for buildings 4 stories tall
– Depth of 2 way systems varies between 1/12 to 1/20 of span
– Cable structure: economical up to 150 feet


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