Materials

Configure concrete grade, reinforcement grade, cover, and stress-strain models for concrete section analysis.

Overview

Material properties drive every calculation in ACS — from section property transformations through to ultimate capacity and serviceability checks. The materials panel in the left sidebar lets you select the design code, concrete grade, reinforcement grade, cover, and concrete stress-strain model.

Design code

Select the governing design standard from the dropdown. This choice affects:

Strength reduction factors ( $\phi$ )
Ductility limits and checks
Serviceability stress limits and crack width formulas
Available concrete grades and rebar grades
Fire design methods

Code	Label	Jurisdiction
AS 3600:2018	AS_3600	Australia / New Zealand
ACI 318-19	ACI_318	United States
EN 1992-1-1:2004	EN_1992_1_1	Europe

Concrete grade

Each design code provides a set of standard concrete grades. The grade defines the characteristic compressive strength $f'_c$ (or $f_{ck}$ in Eurocode notation).

Australian grades (AS 3600)

Grade	$f'_c$ (MPa)
N20	20
N25	25
N32	32
N40	40
N50	50
N65	65
N80	80
N100	100

American grades (ACI 318)

Grades are specified by $f'_c$ in psi, displayed in MPa:

Grade	$f'_c$ (MPa)
3000 psi	20.7
4000 psi	27.6
5000 psi	34.5
6000 psi	41.4
8000 psi	55.2

Eurocode grades (EN 1992)

Grade	$f_{ck}$ (MPa)
C20/25	20
C25/30	25
C30/37	30
C35/45	35
C40/50	40
C50/60	50

Reinforcement grade

Rebar grades define the yield strength $f_y$ , ultimate strength $f_{su}$ , and elastic modulus $E_s$ .

Australian grades (AS/NZS 4671)

Grade	$f_y$ (MPa)	$f_{su}$ (MPa)	$E_s$ (MPa)	Ductility class
D500N	500	600	200,000	Normal
D500L	500	540	200,000	Low
D250N	250	300	200,000	Normal

Bar sizes

Standard bar diameters and areas are available per jurisdiction. For Australian reinforcement:

Bar	Diameter (mm)	Area (mm $^2$ )
N10	10	78.5
N12	12	113
N16	16	201
N20	20	314
N24	24	452
N28	28	616
N32	32	804
N36	36	1018
N40	40	1257

Cover

Cover is the clear distance from the nearest concrete surface to the outer surface of the outermost reinforcement (including stirrups).

Manual cover

Enter cover values directly for each face:

Face	Description	Typical range
Top	Cover to top reinforcement	25—60 mm
Bottom	Cover to bottom reinforcement	25—60 mm
Left	Cover to side reinforcement	25—60 mm
Right	Cover to side reinforcement	25—60 mm

Code-based cover

Select an exposure class and fire rating, and ACS computes the minimum required cover per the selected design code. The computed value accounts for:

Durability requirements — minimum cover for corrosion protection based on exposure class (AS 3600 Table 4.10.3.2; ACI 318 Table 20.6.1.3.1; EN 1992-1-1 Table 4.4N)
Fire requirements — minimum cover for fire resistance based on member type and required FRL
Construction tolerances — $\Delta c_{dev}$ added per code (typically 5—10 mm)

The governing (largest) value from durability and fire is adopted.

Concrete stress-strain model

ACS supports multiple concrete compressive stress-strain models for flexural and moment-curvature analysis. The model affects the shape of the stress block and hence the calculated capacity and ductility.

Model	Description	Best suited for
Rectangular	Uniform stress of $\alpha_2 f'_c$ over depth $\gamma k_u d$	Code-aligned design checks
Hognestad	Parabolic ascending, linear descending	General analysis, academic work
Mander	Confined concrete model with enhanced ductility	Confined columns, seismic design
Parabolic-rectangular	Parabolic to peak, constant to ultimate strain	EN 1992-1-1 aligned
Bilinear	Elastic then perfectly plastic	Quick estimates
FIB Model Code 2010	Smooth curve with post-peak softening	Advanced nonlinear analysis

The rectangular stress block is the default and matches the simplified method used in all three design codes for routine design. Use the more advanced models for moment-curvature analysis or when investigating post-peak behaviour.

Section geometry — defining the concrete outline
Reinforcement — placing bars within the section
Section analysis — running design checks
Design standards reference — detailed code comparison