Sajidalikhan/3D_surfaces_generator

Biaxial RC Column Interaction Surface — ACI 318-19

A structural engineering design tool for reinforced concrete columns under biaxial bending, built in accordance with ACI 318-19.

Features

• —True 3D rotatable interaction surface — drag to rotate, scroll to zoom, hover for exact values
• —8 ρg contour surfaces from 1% to 8% steel ratio, colour-coded and translucent
• —Set 1 — Section definition: f'c, fy, b, h, cover d', tied/spiral, bar configuration (4 to 20 bars, symmetric)
• —Set 2 — Demand check: Enter Pu, Mux, Muy → tool computes Kn, Rnx, Rny, required ρg, and plots the demand point (red marker) on the surface
• —γx and γy computed automatically from geometry
• —Bresler load contour method for biaxial capacity

How to use

1. 1.Set 1: Choose material strengths, column dimensions, cover, column type, and bar count → click Generate 3D Interaction Surface
2. 2.Rotate the 3D surface to inspect from any angle
3. 3.Set 2 (optional): Enter factored demands Pu, Mux, Muy → click Check Demand Point to find required ρg and see the point highlighted on the surface

Theory

• —Uniaxial P-M curves generated per ACI 318-19 using strain compatibility (ε_u = 0.003)
• —ϕ varies linearly from 0.65/0.75 (compression-controlled) to 0.90 (tension-controlled) per ACI Table 21.2.2
• —Biaxial surface constructed using the Bresler load-contour approximation: (Rnx/Rnx0)^α + (Rny/Rny0)^α ≤ 1.0

References

• —ACI 318-19: Building Code Requirements for Structural Concrete
• —Nilson, Darwin & Dolan: Design of Concrete Structures, 15th Ed.