Reinforced Concrete Beam & Slab Design
to Eurocode 2 (EN 1992-1-1)

Introduction to Eurocode 2 Concrete Design

Eurocode 2 (EN 1992-1-1) defines the principles for the design of concrete structures across Europe and many international jurisdictions. Unlike older prescriptive codes such as BS 8110, Eurocode 2 adopts a rigorous limit state philosophy based on characteristic material properties, partial safety factors (γ_c = 1.5 for concrete, γ_s = 1.15 for steel), and stress-block models that maximize structural efficiency while ensuring robust reliability.

This guide breaks down the core ultimate limit state (ULS) and serviceability limit state (SLS) design procedures for rectangular RC beams and solid one-way slabs.

1. Ultimate Limit State (ULS) Flexural Design

For a rectangular section of width b and effective depth d subjected to design bending moment M_Ed, the normalized bending moment factor K is evaluated:

The limiting value K' (typically 0.168 without redistribution, or adjusted for moment redistribution factor δ) governs whether single or double reinforcement is required:

• If K ≤ K': Singly reinforced section (tension steel only). Lever arm z = d · [0.5 + √(0.25 - K / 1.134)] ≤ 0.95d.
• If K > K': Doubly reinforced section (compression steel required). Compression steel area A_s2 = (K - K') · f_ck · b · d² / [f_sc,d · (d - d')].

The required tension reinforcement area A_s,req is calculated as:

2. Shear Verification (EN 1992-1-1 §6.2)

Eurocode 2 utilizes the variable pitch truss model for shear design. First, check if shear reinforcement is required by comparing applied shear force V_Ed against unreinforced concrete shear resistance V_Rd,c:

Where scale factor k = 1 + √(200/d) ≤ 2.0 and reinforcement ratio ρ_l = A_sl / (b_w · d) ≤ 0.02.

If V_Ed > V_Rd,c, shear links (stirrups) must be designed using strut angle θ (21.8° ≤ θ ≤ 45° or 1.0 ≤ cot θ ≤ 2.5). The maximum crushing capacity of concrete struts V_Rd,max must also satisfy V_Ed ≤ V_Rd,max.

3. Serviceability Limit States (SLS): Deflection & Cracking

Deflection is normally verified via the simplified span-to-effective-depth ratio (l / d) per EN 1992-1-1 §7.4.2:

Crack widths (ω_max) are limited to 0.3 mm for normal exposure classes (XC2–XC4). They are controlled either by direct calculation or by limiting maximum bar spacing and diameters per EN 1992-1-1 Table 7.2N/7.3N under quasi-permanent load combinations.

Summary Checklist for Eurocode 2 Concrete Design

1. 1

   Load Combination

   Calculate 1.35G_k + 1.5Q_k (or 1.25G_k + 1.5Q_k depending on NA).

2. 2

   Flexural Verification

   Check K ≤ K', determine A_s,req and select bar diameters.

3. 3

   Shear Verification

   Check V_Ed against V_Rd,c and V_Rd,max; provide link spacing s_max.

4. 4

   Serviceability Checks

   Confirm span-to-depth (l/d) and crack control detailing.