To account for the effect of accidental moments, the ACI Code specifies that the maximum load on a column must not exceed 0.85 times the axial-load capacity of tied columns and 0.8 times the axial-load capacity of spiral columns.

Compression-controlled tied columns have a strength-reduction factor of _____.

Determine the maximum axial strength φPn,max for the following circular tie column.Column diameter, h = 28 in.Number of longitudinal bars = 8Size of longitudinal bars = No. 6Size of ties = No. 4Concrete strength = 2,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 60,000 psi

In a typical construction cycle, the reinforcement and concrete for the beams and slabs in a floor system are placed before the reinforcement and concrete for the columns below it.

Determine the maximum axial strength φPn,max for the following circular spiral column.Column diameter, h = 26 in.Number of longitudinal bars = 8Size of longitudinal bars = No. 10Size of spirals = No. 4Concrete strength = 6,000 psiYield strength of longitudinal bars = 60,000 psiYield strength of spirals = 60,000 psi

In nonseismic areas, spiral columns are used more extensively.

A wall footing has the following conditions. Determine the shear capacity, φVn, of the footing. Assume the footing is 4 ft wide, the pressure that acts on the bottom of the footing is 6,500 psf, and the reinforcement is a #4 bar spaced every 12 inches.The bottom of the footing is at a depth of 3 ft below grade.The service dead load is 11 kips/ft, and the service live load is 8 kips/ft.The wall is 12 in. thick.The footing is 13 in. thick.The allowable soil pressure, qa, is 5,700 psf.The soil has a density of 110 lb/ft3.The concrete has a density of 150 lb/ft3.The concrete cover has a thickness of 3 in.f’c = 3,900 psi and fy = 60,000 psi.

Determine the location of the neutral axis, c, for the following tied column when the largest strain in the concrete is 0.003 and the strain in the tension reinforcement is 0.003.b = 14 in.h = 20 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 6Size of longitudinal bars = No. 6Size of ties = No. 3Concrete strength = 5,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 60,000 psi

Generally, columns are built with the same reinforcement in the two faces parallel to the axis of bending.

Misalignment of a load on a column will produce a moment.