3.1.1 General
1) The properties most frequently required for design calculations are summarised hereafter. For lightweight concretes they are given as functions of their oven-dry unit mass, @, which is in kg/m3 in the formulae in this Chapter.
2) Concrete strength classes higher than C50/60 should not be used unless their use is appropriately justified. No Application Rules are given for this case.
3.1.2 Concrete strength classes
This Eurocode is based on the characteristic cylinder strength, fck, measured at age 28 days in accordance with clause 3.1.2.2 of EC2. The strength fck shall be at least equal to 20 N/mm2 (MPa).
2) The design should be based on a strength class of concrete which corresponds to a specified value of fck. Table 3.1 gives for the different strength classes the characteristic strength fck and the corresponding values of the associated cube strength (e.g. the classification of concrete C 20/25 refers to cylinder/cube strengths) and, for normal-weight concrete, of the mean tensile strength fctm and characteristic tensile
strengths fctk 0.05 and fctk 0.95. The columns of this Table associated with fck equal to 12 and 16 are intended only to provide information on the properties of concretes of higher class, being less than 28 days old.
Table 3.1 — Concrete strength classes, characteristic compressive strength fck (cylinders) and characteristic tensile strength fct of the concrete (in N/mm2)
[ENV Note: Pending a rule applicable to both EC2 and EC4, on the variation in time of fc and fct, guidance may be found in existing national codes or standards.]
3) For lightweight concretes, tensile strengths can be obtained by multiplying the values obtained from the Table by the factor
) = 0.30 + 0.70 (@/2400).
3.1.3 Shrinkage of concrete
1) Where accurate control of the profile during execution is essential, or where shrinkage is expected to take exceptional values because of the composition of concrete or because of its environment (e.g. very frequently wet concrete), or when shrinkage has to be assessed at intermediate times, reference should be made to clause 3.1.2.5.5 and Appendix I of EC2.
2) In the most common cases generally and unless differently specified or justified for the particular project, the total long-term free shrinkage strain from setting of the concrete, &cs, may be given the following values as an acceptable approximation:
Strength Class of Concrete C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60
fck 12 16 20 25 30 35 40 45 50
fctm 1.6 1.9 2.2 2.6 2.9 3.2 3.5 3.8 4.1
fctk 0.05 1.1 1.3 1.5 1.8 2.0 2.2 2.5 2.7 2.9
fctk 0.95 2.0 2.5 2.9 3.3 3.8 4.2 4.6 4.9 5.3
— in dry environments (whether outside or within buildings, concrete-filled members excluded) 325 × 10–6 for normal-weight concrete
500 × 10–6 for lightweight concrete
— in other environments and in filled members 200 × 10–6 for normal-weight concrete 300 × 10–6 for lightweight concrete.
3.1.4 Deformability of concrete — elastic theory
3.1.4.1 Secant modulus of elasticity for short-term loading
1) Nominal values of the mean secant modulus Ecm for short-term loading for normal-weight concrete of a given strength class or of characteristic compressive strength fck are given in Table 3.2.
Table 3.2 — Values of the secant modulus of elasticity Ecm (in kN/mm2)
2) For an age t less than 28 days, Ecm should be obtained from Table 3.2 taking into account the actual compressive strength at age t.
3) For lightweight concretes, secant moduli can be obtained by multiplying the values obtained from the Table by (@/2400)2.
3.1.4.2 Modular ratios
[ENV Note: Possibly to be revised for lightweight concrete when the corresponding clause of Eurocode 2 have been drafted].
1) The deformation of the concrete due to creep shall be taken into account.
2) If it is specified for the particular project that the rules for application given below are not accepted, the nominal values given in clauses 3.1.2.5.5 of EC2 should be adopted.
3) For the design of buildings, global analyses of sway frames excepted, it is accurate enough to take account of creep by replacing in analyses concrete areas Ac by effective equivalent steel areas equal to Ac/n, where n is the nominal modular ratio, defined by n = Ea/E½c, where
Ea is the elastic modulus of structural steel, given in 3.3.3 below, and
E½c is an “effective” modulus of concrete, taking in the various cases the values given below.
4) If specified for the particular project and in any case for buildings mainly intended for storage, two nominal values E½c should be used: one equal to Ecm for short term effects, the other equal to Ecm/3 for long term effects. In other cases E½c may be taken equal to Ecm/2, Ecm having the value defined in 3.1.4.1.
3.1.4.3 Poisson’s ratio
If needed for design purposes, the nominal value of Poisson’s ratio for elastic strains should be assumed to be 0.2. It may be assumed to be zero when concrete in tension is assumed to be cracked.
3.1.5 Deformability of concrete — other theories
1) If a rigid-plastic theory, as defined in Chapter 4, is used, a “stress-block” starting from the neutral axis is assumed; the value of the design stress is defined in the corresponding clauses of Chapter 4 and Annex C, Annex D, and Annex E.
[Note: In Sections 4.4 and 4.8 of EC4, for verifications relating to ultimate limit states a degree of plastification similar to that admitted in EC3 may be considered. This is the reason why in these cases the stress block is defined differently from EC2.]
2) If an elastic-plastic theory is used, whether for global analysis or for cross-section analysis or for both, reference should be made to clause 4.2.1.3.3 of EC2.
3.1.6 Thermal expansion
The nominal value of the coefficient of linear thermal expansion !T should be taken as 10 × 10–6/°C for normal-weight concrete. [ENV Note: subject to the final version of Part 1C of EC2, the value 7 × 10–4 is suggested for lightweight concrete.]
3.2 Reinforcing steel
3.2.1 General
The properties most frequently required for design calculations and summarised hereafter. If relevant, reference shall be made to Section 3.2 of EC2.
[ENV Note: Section3.2 may have to be revised after completion of EN 10080 and subsequent European standards].
Strength Class C (or fck) (12) (16) C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60
Ecm 26 27.5 29 30.5 32 33.5 35 36 37
3.2.2 Types of steels
1) The steels covered by EC4 shall be distinguished as follows:
— according to surface characteristics:
a) plain smooth bars or wires (including welded mesh) and
b) ribbed bars or wires (including welded mesh), resulting in high bond action (as specified in EN 10080). ENV Note: clause 3.2.5.1 of EC2 characterizes high bond bars as having a rib factor, denoted fR, not less than in EN 10080, which is in preparation and whose Table 5 in clause 5.7.2 give values ranging from 0.036 (for d = 4 mm) to 0.056 (for d U 11 mm)
— according to ductility characteristics: high or normal, as defined in 3.2.4.2 2) of EC2.
ENV Note: clauses 3.2.1 6) and3.2.4.2 of EC2 define &uk as the characteristic value of the elongation at maximum load, to be specified in “relevant standards”.][
— according to weldability, clauses 3.2.5.2 and 4.2.2.4.2 of EC2 are applicable.
3.2.3 Steel grades
1) A grade denotes the value of the specified characteristic yield strength fsk in N/mm2 (MPa).
2) Standardized grades are defined in EN 10080 (in preparation) or in national documents for material not covered by EN 10080. In addition to fsk, the following shall be defined: tensile strength ft, minimum ratio ft/fsk, elongation at maximum load &u, all of them as characteristic values; and also the projected rib factor fR.
3.2.4 Modulus of longitudinal deformation
For the design of composite structures, the nominal value of the modus of longitudinal deformation Es may for simplicity be taken as equal to the value specified in EC3 for structural steel, i.e. 210 kN/mm2 (GPa).
3.2.5 Stress-strain diagram
For design of composite structures, the stress-strain diagram may for simplicity consist of two branches:
— a first branch, starting from the origin with a slope equal to Es, up to fsk (or fsk/*s according to the corresponding clauses of Chapter 4); and
— a second branch which is horizontal or, for practical use of computers, is assumed to have a very small slope such as 10–4 Es and in this last case is limited to the strain .
3.2.6 Thermal expansion
The nominal value of the coefficient of linear thermal expansion !T may for simplicity be taken as 10 × 10–4/°C.
Figure 3.1 — Design stress-strain diagram for reinforcement
3.3 Structural steel
3.3.1 General and scope
1) This Part 1.1 of Eurocode 4 covers the design of composite structures fabricated from steel material conforming to Chapter 3 of EC3. No application rules are given for the use of high-strength steel to Annex D of EC3. For this steel, clause 3.2.1 2) of EC3 is applicable.
2) Section 3.2 of EC3 is applicable to composite structures.
3) The properties most frequently required for design calculations are summarized hereafter.
3.3.2 Yield strength
1) The nominal values of the yield strength fy and the ultimate tensile strength fu for hot rolled steel/members are given in Table 3.3 for steel grades Fe 360, Fe 430 and Fe 510, in accordance with EN 10025.
Table 3.3 — Nominal values of yield strength fy and ultimate tensile strength fu for structural steel to EN 10025
2) The nominal values in Table 3.3 may be adopted as characteristic values in calculations.
3) As an alternative, the nominal values specified in EN 10025 for a larger range of thicknesses may be used.
3.3.3 Design values of other material coefficients
1) The material coefficients to be adopted in calculations for the steels covered by this Eurocode shall be taken as follows:
2) For simplification in design calculations for composite structures, the value of the coefficient of linear thermal expansion !T may be taken as 10 × 10–4 per °C, which is the value given in EC2 for reinforcing steel and normal weight concrete.
3.3.4 Stress-strain relationship
1) In accordance with clause 5.2.1.4 of EC3, for design calculations the relation between stress and strain of structural steel may be idealised as elastic-perfectly plastic, as shown in Figure 3.2.
2) To avoid possible computational difficulties when using a computer the alternative bilinear stress-strain relationship indicated in Figure 3.3 may be used.
Nominal steel grade
Thickness tmma
t k 40 mm 40 mm < t k 100 mm
fy(N/mm2) fu(N/mm2) fy(N/mm2) fu(N/mm2)
Fe 360 235 360 215 340
Fe 430 275 430 255 410
Fe 510 355 510 335 490
a t is the nominal thickness of the element
— modulus of elasticity Ea = 210 000 N/mm2
— shear modulus Ga = E/2(1 + 5a)
— Poisson’s ratio 5a = 0.3
— unit mass @a = 7 850 kg/m3
3.3.5 Dimensions, mass and tolerances
The dimensions and mass per unit length of all rolled steel sections, plates and structural hollow sections, and their dimensional and mass tolerances, shall conform with Reference Standard 2 of EC3.
3.4 Profiled steel sheeting for composite slabs
3.4.1 General and scope
1) This Part 1 of Eurocode 4 covers the design of composite slabs with profiled steel sheets manufactured from mild steel in accordance with EN 10025, high strength steel in accordance with prEN 10113, cold reduced steel sheet in accordance with ISO 4997:1978 or galvanised steel sheet in accordance with prEN 10147.
[ENV Note: Reference to ISO-standards to be replaced by reference to EN-standards, if available]
2) It is recommended that the bare metal thickness should not be less than 0.75 mm except where the steel sheeting is used only as permanent shuttering. The use of thinner sheets is not precluded, provided that adequate theoretical evidence and test data are available.
3) Part 1.3 of Eurocode 3 is applicable to steel sheeting used for composite slabs.
[ENV Note Reference standards should be prepared for profiled steel sheeting, including tolerances on embossments [see also10.3.1.32)]. In their absence, reference should be made to European Technical Approvals or national documents.
3.4.2 Yield strength
1) The nominal values of the yield strength of the basic martial fyb are given in Table 3.4, for the steel grades given in the standards referred to in 3.4.1.
2) The nominal values of fyb in Table 3.4 may be adopted as characteristic values fyp in calculations.
Figure 3.2 — Bilinear stress-strain relationship
Figure 3.3 — Idealisation for computer calculations
Table 3.4 — Yield strength of basic material fyb
3.4.3 Nominal values of other material coefficients
The material coefficients given in 3.3.3 for hot rolled structural steel are applicable to profiled steel sheets.
3.4.4 Stress-strain relationship
The idealisations of the relation between stress and strain given in 3.3.4 for hot rolled structural steel are applicable to profiled steel sheet.
3.4.5 Coating
1) The exposed surfaces of the steel sheeting shall be adequately protected to resist the particular atmospheric conditions.
2) A zinc coating of specified, should be in accordance with ISO standard, “Continuous hot-dip coated carbon steel sheet of structural quality, ISO 4998:1977”, or with relevant standards in force.
3) A zinc coating of total mass 275 g/m2 (including both sides) is normally sufficient for internal floors in a non-aggressive environment, but the specification may be varied depending on service conditions.
4) Coating other than by galvanizing should not be used unless sufficient testing has demonstrated that the sheeting satisfies the requirements of this Eurocode.
3.5 Connecting devices
3.5.1 General
1) Connecting devices shall be suitable for their specified use.
2) For connecting devices other than shear connectors, Section 3.3 of EC3 is applicable.
3.5.2 Shear connectors
1) The resistance of a connector is the maximum load in the direction considered (in most cases parallel to the interface between concrete flange and steel beam) that can be carried by the connector before failure.
The resistance of a connector may be different for reversal in the direction of thrust. Due account shall be taken of this.
prEN 10113-3 Fe E 275 TM 275 Fe E 355 TM 355
2) The characteristic resistance PRk shall be the specified resistance below which not more than 5 % of results of tests on samples of a homogeneous population may be expected to fall. When a guaranteed minimum resistance is specified this may be considered as the characteristic resistance.
3) The design resistance PRd shall be the characteristic resistance divided by the appropriate partial safety factor *v.
For the determination of the design resistance by testing, refer to Chapter 10.
4) The material of the connector shall be of a quality which takes into account its required, performance and the methods of fixing to the structural steelwork. Where fixing is by means of welding, the quality of material shall take account of the welding technique to be used. Where anchors or hoops act as shear connectors, special care shall be taken that the material is of an appropriate weldable quality.
5) The specified mechanical properties of the connector material shall comply with the following requirements:
— the ratio of the specified ultimate tensile strength fu to the specified minimum yield strength fy is not less than 1.2;
— the elongation at failure on a gauge length of 5.65ÆAo (where A, is the original cross section area) is not less than 12 %.
For studs, these material properties relate to the finished product.
[ENV Note: Testing of shear connector material is under consideration. Final proposals will be given after consultation with stud manufacturers.]
6) Depending on the type of shear connector, reference should be made to European Standards or European Technical Approvals or, in their absence, to national documents.
7) The head of stud connectors should have a diameter of not less than 1.5d and a depth of not less than 0.4d, Where d is the shank diameter of the stud.