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Problems: supplemental problems (7A, etc.) and from Onouye Chapters 4 & 5
Notes: Problems marked with a * have been altered with respect to the problem stated in the text.
7A) A reinforced concrete slab is 6 in. thick. If the density is 150 lb/ft3, determine the weight per
unit area in lb/ft2 and in kN/m2. (un-dimensioned figure). (dimensional analysis & conversions)
Partial answer to check with: 3.59 kN/m2
7B) The compressive force in a column to each service (unfactored) load are: D = 465 kN,
L = 290 kN, Lr = 65 kN, W = 110 kN, E = 245 kN. The wind load can also result in a tensile
force. Determine the design load for the column based on LRFD using ASCE-7 load
combinations (see Note Set 13.6) (load factors)
Partial answer to check with: max{651, 1054.5, (952 or 717, 607), (990.5 or 770.5),
1093, (528.5 or 308.5), 663.5} kN.
7C) Roof beams that weigh 50 lb/ft and are spaced at 10’ center to center support an
additional dead load of 30 lb/ft2. Code specified roof loads are 35 lb/ft2 downward (due to roof
live load, snow or rain) and 25 lb/ft2 upward or downward (due to wind). Determine the
critical loading for LRFD using ASCE-7 load combinations (see Note Set 13.6).
(load tracing and load factors)
Partial answer to check with: max {490, 595, (1105 or 855), (845 or 345), 490.
(565 or 65), 315} lb/ft.
*
Partial answer to check with: SFover= 1.43, SFslide = 1.77,
pmax = 2000 lb/ft2 (under footing)
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(6%)
(12%)
(12%)
(20%)
Assume the
allowable bearing pressure is 3000 psf. Also check for factor
of safety against sliding if the friction coefficient is 0.62.
(retaining wall behavior)
force due to pressure
