Same engineering check.Three codes.

Side-by-side reference for IS, ACI, and Eurocode provisions. Skim the takeaway, dive into the formulas when you need to defend a design.

foundation

Two-way (punching) shear capacity

ISIS 456 Cl. 31.6.3

k_s × τ_c = (0.5 + β_c) × 0.25√f_ck

Capped at 0.25√f_ck. β_c = short side / long side of column.

ACIACI 318-22 §22.6.5

v_c = min{ 0.33√f'_c , 0.17(1+2/β)√f'_c , 0.083(α_s d/b_o + 2)√f'_c }

Three formulas, smallest governs. α_s = 40/30/20 for interior/edge/corner.

ECEC 2 §6.4

v_Rd,c = C_Rd,c × k × (100ρ_l × f_ck)^(1/3)

Critical perimeter at 2d from column face. C_Rd,c = 0.18/γ_c.

Takeaway: IS uses √f_ck plus a column-aspect factor. ACI takes the smallest of three. EC2 cubes the steel ratio explicitly. Identical concrete strength gives different capacities — typically EC2 < ACI < IS for high-strength concrete.

concrete

Minimum flexural reinforcement (beams)

ISIS 456 Cl. 26.5.1.1

A_s,min = 0.85 / f_y × b × d

0.205% for Fe 415, 0.17% for Fe 500. Independent of concrete grade.

ACIACI 318-22 §9.6.1.2

A_s,min = max{ 3√f'_c × b_w × d / f_y , 200 b_w d / f_y }

In psi units. Increases with f'_c — higher-strength concrete needs more steel to prevent brittle first-cracking.

ECEC 2 §9.2.1.1

A_s,min = 0.26 × (f_ctm / f_yk) × b_t × d ≥ 0.0013 × b_t × d

Tied to mean tensile strength f_ctm = 0.30 × f_ck^(2/3). Floor of 0.13%.

Takeaway: IS uses a flat 0.85/f_y. ACI scales with √f'_c. EC2 scales with f_ck^(2/3). For M30 / 4000 psi, results are within ~15% — so the design intent matches even though the formulas look different.

steel

Lateral-torsional buckling (LTB) of beams

ISIS 800 Cl. 8.2.2

M_d = β_b × Z_p × f_bd

f_bd is design bending compressive stress; depends on slenderness λ_LT = √(β_b Z_p f_y / M_cr).

ACIAISC 360 §F2

M_n = C_b × M_p (for L_b ≤ L_p) or interpolation between L_p and L_r.

Three regimes: plastic, inelastic LTB, elastic LTB. C_b accounts for moment gradient.

ECEC 3 §6.3.2

M_b,Rd = χ_LT × W_y × f_y / γ_M1

χ_LT depends on slenderness λ̄_LT and an imperfection factor α_LT (curve a/b/c/d by section type).

Takeaway: IS computes elastic-critical M_cr first then maps to f_bd. AISC has a piecewise-linear capacity curve. EC3 is the closest to a closed-form reduction factor χ_LT. All three agree within ~10% for compact sections at typical Cb=1 conditions.

concrete

Minimum concrete grade by exposure

ISIS 456 Table 5

Mild M20 · Moderate M25 · Severe M30 · Very Severe M35 · Extreme M40 (RCC).

ACIACI 318-22 §19.3.2

F0 / F1 / F2 / F3 freeze-thaw + S0 / S1 / S2 / S3 sulfate + W0 / W1 / W2 wet-dry classes set min f'_c.

ECEN 206 Table F.1

Exposure XC / XD / XS / XF / XA classes each map to a min strength class C20/25 to C35/45.

Takeaway: IS exposure is a single 5-tier scale. ACI and EN 206 split exposure into multiple chemistry-specific classes. Cross-mapping is non-trivial — for a marine project, "extreme" (IS) ≈ "S3" (ACI) ≈ "XS3" (EN 206).

serviceability

Crack-width control (water-retaining structures)

ISIS 3370 Part 2 §3.3

0.2 mm severe exposure; 0.1 mm in direct contact with potable water.

ACIACI 350-20

Crack-width via Z = f_s × ³√(d_c × A) ≤ environmental limit

Severe environmental exposure: w_max ≈ 0.18 mm.

ECEC 2 §7.3 + EN 1992-3

w_k ≤ 0.2 mm (XC class) or 0.1 mm (tightness class 1).

EN 1992-3 (water retaining annex) tightens limits for liquid-retaining work.

Takeaway: All three converge on ~0.1–0.2 mm permissible crack width for water-retaining work. The IS limit is the simplest to apply; EN 1992-3 has the most granular tightness-class system.

seismic

Liquefaction screening

ISIS 1893 Part 1 Cl. 7.6

CSR = 0.65 × (a_max/g) × (σ_v/σ'_v) × r_d

NCEER simplified procedure with FoS_liq = CRR/CSR ≥ 1.0.

ACIASCE 7-22 §11.8.3

Same NCEER simplified procedure

US practice mirrors NCEER with site-specific PGA from USGS hazard maps.

ECEC 8 Part 5 Annex B

Same simplified CSR/CRR approach

CRR derived from N₆₀,1 with magnitude scaling factor for non-Mw 7.5 events.

Takeaway: All three codes adopt the NCEER simplified procedure. Differences are in regional PGA maps and magnitude scaling — the engineering math is essentially identical.

Editorial paraphrases for educational reference. The official code text is always authoritative.