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

When a column is under compression, the column shortens and expands laterally.

Determine the required splice length for the galvanized longitudinal bars in the following tied column made of normal-weight concrete. Assume that some of the longitudinal bars are in tension and that the connection should be designed as a Class B contact lap splice. Use ACI 318-14 Table 25.4.2.2 to calculate the development length, and assume that the ties satisfy the Code minimum.Column width, b = 20 in.Column thickness, h = 28 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 10Size of longitudinal bars = No. 10Size of ties = No. 3Concrete strength = 8,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

Determine the required splice length for the galvanized longitudinal bars in the following tied column made of lightweight concrete. Assume that some of the longitudinal bars are in tension and that the connection should be designed as a Class B contact lap splice. Use ACI 318-14 Table 25.4.2.2 to calculate the development length, and assume that the ties satisfy the Code minimum.Column width, b = 28 in.Column thickness, h = 26 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 12Size of longitudinal bars = No. 6Size of ties = No. 3Concrete strength = 5,000 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

Determine the maximum axial strength φPn,max for the following tied column.Column width, b = 24 in.Column thickness, h = 12 in.Number of longitudinal bars = 14Size of longitudinal bars = No. 8Size of ties = No. 3Concrete strength = 2,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

Determine the required splice length for the epoxy-coated longitudinal bars in the following tied column made of lightweight concrete. Assume that some of the longitudinal bars are in tension and that the connection should be designed as a Class B contact lap splice. Use ACI 318-14 Table 25.4.2.2 to calculate the development length, and assume that the ties satisfy the Code minimum.Column width, b = 22 in.Column thickness, h = 14 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 6Size of longitudinal bars = No. 10Size of ties = No. 3Concrete strength = 5,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

The minimum number of longitudinal bars in a spiral column is six.

Determine the maximum axial strength φPn,max for the following circular spiral column.Column diameter, h = 22 in.Number of longitudinal bars = 10Size of longitudinal bars = No. 6Size of spirals = No. 4Concrete strength = 5,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of spirals = 60,000 psi

Less than 5% of columns in buildings in nonseismic regions are _______ columns.

Spiral columns are used when ductility is important or where high loads make it economical to utilize the extra strength from the higher φ factor.