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.

Spiral reinforcement acts to restrain the lateral expansion of the column core under high axial loads and delays the failure of the core, making the column less ductile.

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 = 12 in.h = 22 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 6Size of longitudinal bars = No. 9Size of ties = No. 4Concrete strength = 2,500 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 60,000 psi

Determine the required splice length for the longitudinal bars in the following tied column. Assume that all of the longitudinal bars are in compression and that you will use a contact lap splice. Do not incorporate a reduction in length due to ACI 318-14 Section 10.7.5.2.1.Column width, b = 28 in.Column thickness, h = 18 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 4Size of longitudinal bars = No. 10Size of ties = No. 4Concrete strength = 8,500 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 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 = 22 in.Column thickness, h = 24 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 12Size of longitudinal bars = No. 9Size of ties = No. 3Concrete strength = 3,000 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi

Use the interaction diagrams found in Appendix A of the textbook to determine whether the following circular spiral column can safely support a load of Pu = 1,539 kip and Mu = 431.0 kip-ft.h = 28 in.fc’ = 4 ksify = 60 ksiγ = 0.9ρg = 0.04

Reinforced concrete is not elastic and has a tensile strength that is much higher than its compressive strength.

When designing columns, it is often more desirable to use symmetrical reinforcement.

Reinforced concrete is elastic and has a compressive strength that is much higher than its tensile strength.

Determine the required splice length for the epoxy-coated 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 = 26 in.Column thickness, h = 24 in.Clear cover to ties = 1.5 in.Number of longitudinal bars = 14Size of longitudinal bars = No. 10Size of ties = No. 3Concrete strength = 7,000 psiYield strength of longitudinal bars = 60,000 psiYield strength of ties = 40,000 psi