# Tag Archives: ARE

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

**[WOOD]
**– Wood joists: 2×8, 2×10, 2×12 spaced 12, 14 or 16 inches apart

– Maximum slenderness ratio for column (l/r) is 50

**[STEEL]**

– 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

**[CONCRETE]**

– 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

**[STUD WALLS]**

– Common 2×4 studs places 16 inches on center

**[REINFORCED BRICK MASONRY]**

– Bar spacing about 18 to 36 inches

**[SYSTEMS]**

– 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

# Lateral Load Resisting Systems (SS)

# Interior Column Load (SS)

Common question:

Building *n* stories tall, with columns on *a by a* grid, live load *L* and dead load *D*.

Approximate total axial load on a typical first-floor interior column=

Ultimate Load * Tributary Area of the Column * no. of stories=

(1.6L + 1.2D ) * a * a * n

# Stiffeners (SS)

image source: http://www.civilengineeringterms.com/steel-structures/stiffener/

Stiffeners:

– consist of steel/ wood plates fitted between flanges

– help prevent the buckling of flanges

– are used in various locations, including at the crown and points of change in direction.

# Home Insurance Building (SS)

image source: http://www.allaboutskyscrapers.com/construction/introduction

Considered the world’s first skyscraper.