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Design and analysis of reinforced concrete column calculator

Jonathan Ochshorn

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Directions: First, select method A, B, or C at the top of the calculator: method "A" analyzes rectangular (tied) or circular (spiral) reinforced concrete columns — that is, calculates capacity or safe design (factored) load — given dimensions, number and size of rebars, concrete strength and steel yield stress; method "B" calculates rebar size and number given gross dimensions and design (factored) load; and method "C" calculates approximate gross area given design (factored) load and steel ratio. The area determined in method "C" can then be inserted into method "B" in order to calculate number and size of rebars. This calculator is based on the strength design method of ACI 318-08. Reinforcement ratio (steel area / gross column area) must be between 1% and 8%; column analysis (method "A") also checks bar fit based on assumptions about aggregate size and tie or spiral diameter, and assuming 1-1/2 in. cover.

All methods assume that columns are axially loaded, and are not slender enough for buckling to reduce the axial load capacity.

Press "update" button.

More detailed explanations and examples can be found in my text.

rectangular and circular column cross sections
Fig. 1. Rectangular (left) and circular (right) column cross sections.

Selecct method A, B, or C:
f'c (ksi) fy (ksi) shape
Reinforcement: Number of bars Bar size
Maximum allowable design (factored) load or capacity, Pu:
Design (factored) load, Pu:
Required steel area:
Rebar choices:
Design (factored) load, Pu:
Assumed steel ratio:  
Gross area corresponding to steel ratio:  
A. Analysis of column  
width or diameter must be > 0
length must be > 0
steel area must be < gross area
minimum 6 bars for spiral
minimum 4 bars for tied column
reinf ratio must be >= 0.01
reinf ratio must <= 0.08
no. bars in line must be <= total/2
total bars in rect. col. must be even
column too small - bar fit check no good
B. Col design with dimensions assumed  
width or diameter must be > 0
length must be > 0
design load must be > 0
C. Col design with steel ratio assumed  
design load must be > 0