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} \times τ_{c} = (0.5 + β_{c}) \times 0.25 f_{c k}

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_{R d, c} = C_{R d, c} \times k \times (100 ρ_{l} \times f_{c k})^{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} \times b \times 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}^{'} \times b_{w} \times 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 \times (f_{c t m} / f_{y k}) \times b_{t} \times d \geq 0.0013 \times b_{t} \times 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} \times Z_{p} \times f_{b d}

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} \times M_{p} (f or L_{b} \leq L_{p}) or in t er p o l a t i o nb e tw ee n L_{p} an d L_{r .}

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

ECEC 3 §6.3.2

M_{b, R d} = χ_{L T} \times W_{y} \times f_{y} / γ_{M 1}

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

C r a c k - w i d t h v ia Z = f_{s} \times^{3} d_{c} \times A \leq e n v i r o nm e n t a l l imi t

Severe environmental exposure: w_max ≈ 0.18 mm.

ECEC 2 §7.3 + EN 1992-3

w_{k} \leq 0.2 mm (X C c l a ss) or 0.1 mm (t i g h t n essc l a ss 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

C S R = 0.65 \times (a_{ma x} / g) \times (σ_{v} / σ_{v}^{'}) \times r_{d}

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

ACIASCE 7-22 §11.8.3

S am e N C E E R s im pl i f i e d p r oce d u r e

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

ECEC 8 Part 5 Annex B

S am es im pl i f i e d C S R / C R R a pp r o a c h

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.

concrete

Development (anchorage) length

ISIS 456 Cl. 26.2.1

L_{d} = (ϕ \times σ_{s}) / (4 \times τ_{b d})

σ_s = 0.87 f_y. Bond τ_bd ×1.6 for deformed bars, +25% in compression. Often ~47φ for Fe500/M25.

ACIACI 318-22 §25.4.2

ℓ_{d} = (f_{y} ψ_{t} ψ_{e} ψ_{s}) / (1.1 λ f_{c}^{'} \times (c_{b} + K_{t r}) / d_{b}) \times d_{b}

Explicit modification factors for bar location, coating, size and confinement (c_b + K_tr).

ECEC 2 §8.4

l_{b d} = α_{1} α_{2} α_{3} α_{4} α_{5} \times l_{b, r q d}; l_{b, r q d} = (ϕ /4) (σ_{s d} / f_{b d})

Five α factors for shape, cover, confinement, transverse bars and pressure.

Takeaway: IS gives one clean formula with multiplier rules. ACI and EC2 expose the confinement/cover effects as explicit factors, so they reward good detailing with shorter anchorage.

concrete

One-way (beam) shear without stirrups

ISIS 456 Cl. 40 / Table 19

V_{c} = τ_{c} \times b \times d

τ_c tabulated from steel ratio p_t and f_ck. Empirical — no explicit size effect.

ACIACI 318-22 §22.5

V_{c} = 0.17 λ f_{c}^{'} \times b_{w} \times d

Simple √f'_c form (SI). 2019+ adds a size-effect factor λ_s for deep members.

ECEC 2 §6.2.2

V_{R d, c} = C_{R d, c} \times k \times (100 ρ_{l} f_{c k})^{1/3} \times b_{w} d

k = 1 + √(200/d) is an explicit size-effect term; cubes the steel ratio.

Takeaway: IS reads off a table; ACI uses a tidy √f'_c; EC2 builds in a size-effect term k that the others added later. For shallow members all three are close; for deep members EC2 is the most conservative.

serviceability

Deflection control (span/depth)

ISIS 456 Cl. 23.2

(L / d)_{ba s i c} = 20 (S S), 26 (co n t .), 7 (c an t i l e v er) \times M F

Basic ratios times modification factors for tension/compression steel and span.

ACIACI 318-22 Table 9.3.1.1

h_{min} = L /16 (S S), L /18.5, L /21, L /8 (c an t i l e v er)

Minimum thickness to skip a deflection calc; otherwise compute Δ ≤ L/240–L/480.

ECEC 2 §7.4

L / d l imi t f r o m ρ v s ρ_{0}; Δ \leq L /250

Span/depth limit is a function of the steel ratio; quasi-permanent Δ capped at L/250.

Takeaway: All three avoid an explicit deflection calc via a span/depth (or min-thickness) shortcut. IS modifies by steel ratio with factors, ACI gives flat fractions, EC2 ties the limit to ρ directly.

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

Compare Codes

Same engineering check.Three codes.