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D. SP52-101-03 Column Design Principles

For additional information, se D. SP52-101-03 Beam Design Principles

Eccentrically Loaded Columns

The strength of the section and the layout of the longitudinal reinforcing steel bars are interrelated through the effective depth of the section. The program evaluates all selected load combinations in the envelope to determine the worst case interaction of the axial force and bending moment.

Strength verification is performed for the section with maximum axial force eccentricity. The critical load combination is defined by the maximum value of the required steel area. All admissible bar diameters are tried during design of critical section. The diameter resulting in minimum steel area is adopted as optimal one. The transverse reinforcement is determined using maximum shear force value.

Eccentric compression of RC section

where
Rb
=
design strength of concrete
Rs
=
design strength of steel
x
=
depth of neutral axis, constrained by the limiting quantity, depending on steel strength

Design Procedure

The design process is summarized by the following steps:

  1. For each load combination, find the critical section of the column, according to the maximum axial force eccentricity.
  2. Design the reinforcing steel for the critical section.
  3. Compute the required stirrup spacing for the column.
  4. Perform the final strength check for the obtained longitudinal and transverse reinforcement.

The assumptions adopted for the column design procedure, can be summarized as follows:

  1. The longitudinal reinforcement of the column is symmetrical.
  2. Diameter of the intermediate longitudinal bars in the section can be less than that of the corner bars.