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Almost universally, an odd number of bars is used in rectangular columns, so that the column is symmetrical about the axis of bending.

Determine the maximum axial strength φPn,max for the following tied column.Column width, b = 28 in.Column thickness, h = 26 in.Number of longitudinal bars = 4Size of longitudinal bars = No. 10Size of ties = No. 4Concrete strength = 8,000 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 60,000 psi

Designers should compute the interaction diagram for the most favorable bar orientation in a circular column because they have little to no control over how the bars are actually installed.

Determine the maximum pitch, s, for the spirals in the following circular column.Column diameter, h = 24 in.Clear cover to spirals = 1.5 in.Number of longitudinal bars = 8Size of longitudinal bars = No. 6Size of spiral = No. 3Concrete strength = 6,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of spiral = 60,000 psi

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

Determine the maximum axial strength φPn,max for the following tied column.Column width, b = 22 in.Column thickness, h = 16 in.Number of longitudinal bars = 4Size of longitudinal bars = No. 6Size of ties = No. 3Concrete strength = 4,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 60,000 psi

Determine the maximum pitch, s, for the spirals in the following circular column.Column diameter, h = 24 in.Clear cover to spirals = 1.5 in.Number of longitudinal bars = 6Size of longitudinal bars = No. 8Size of spiral = No. 4Concrete strength = 4,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of spiral = 60,000 psi

Compute the axial compressive strength Pn and moment capacity Mn of the following tied column when the largest strain in the concrete is 0.003 and the strain in the tension reinforcement is 0.003. Note that you should not include φ in the answer and that you should not consider Pn,max.b = 12 in.h = 24 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 6Size of longitudinal bars = No. 9Size of ties = No. 3Concrete strength = 8,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

Spiral reinforced columns are less ductile than tied columns, giving spiral columns a lower strength-reduction factor.

_______ columns are those which are not appreciably weakened by moments induced by slenderness effects.