# V. EC3 Belgian NA - I Section with Conc Load

Calculate the bending capacity of a beam subject to a concentrated load per the Belgian NA to EC3.

## Details

The section is a HD320X127, Grade S275 steel. The member is a 5 m, simply-supported span subject to a 30 kN concentrated load at midpsan.

## Validation

Moment capacity:

The critical moment is given by:

$M c r = C 1 π 2 E I ( k L ) 2 { ( k k w ) 2 I w I + ( k L ) 2 G I t π 2 E I + ( C 2 Z g ) 2 − C 2 Z g }$
where
 C1 = 1.35 C2 = 0.59 $π 2 E I y k L 2$ = 7,477,200 $k k w 2 I w I y$ = 22,394 $k L 2 G I t π 2 E I y$ = 23,737 C2Zg = 0.59×160 = 94.4

Therefore, Mcr = 1,416 kN·m

From the Belgian NA, λLT, 0 = 0.4, β = 0.75

So, $λ L T = w y f y M c r = 2,149 × ( 10 ) 3 × 275 1,416 × ( 10 ) 6 = 0.646$

H/b = 320/300 = 1.067 < 2. So, from Table 6.5 of Eurocode 3, αLT = 0.34.

From Cl. 6.3.2.3 of Eurocode3:

ФLT = 0.5[1+αLTLT- λLT, 0) + β× λLT2] = 0.5[1 + 0.34×(0.646 - 0.4) +1 × 0.6462] = 0.698

So, $χ L T = Ф L T + Ф L T 2 - β λ L T 2 - 1 = 0.896$

From Table 6.6 of the Eurocode 3, kc = 0.9

Modification factor: $f = 1.0$

$χ LT,mod = χ L T f = 0.896 < 1 λ L T 2 = 2.396$, OK

## Results

Table 1.
Result Type Reference STAAD.Pro Difference Comments
Moment capacity, Mckd (kN·m) 591.0 591.0 none
Critical moment, Mcr (kN·m) 1,416 1,416 none
Bending capacity, MB (kN·m) 529.4 529.4 none

## STAAD.Pro Input

The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\09 Steel Design\Europe\EC3 National Annex\Belgian NA\EC3 Belgian NA - I Section with Conc Load.std is typically installed with the program.

The following design parameters are used:

• The Belgian NA is specified using NA 8
• Simply-supported span: CMN 1
• Simply-supported span with concentrated load at midspan: CMM 3
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 17-Apr-20
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 5 0 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-005
DAMP 0.03
END DEFINE MATERIAL
MEMBER PROPERTY EUROPEAN
1 TABLE ST HD320X127
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 2 PINNED
LOAD 1 LOADTYPE None  TITLE LOAD CASE 1
MEMBER LOAD
1 CON GY -30
PERFORM ANALYSIS
PARAMETER 2
CODE EN 1993-1-1:2005
NA 8 ALL
CMM 3 ALL
CMN 1 ALL
FU 295000 ALL
PY 275000 ALL
TRACK 2 ALL
CHECK CODE ALL
FINISH


## STAAD.Pro Output

                         STAAD.PRO CODE CHECKING - NBN EN 1993-1-1:2005
********************************************
NATIONAL ANNEX - NBN EN 1993-1-1 ANB : 2018
PROGRAM CODE REVISION V1.13 BS_EC3_2005/1
STAAD SPACE                                              -- PAGE NO.    3
ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
FX            MY             MZ       LOCATION
=======================================================================
1 ST   HD320X127   (EUROPEAN SECTIONS)
PASS     EC-6.3.2 LTB       0.071         1
0.00            0.00         -37.50        2.50
=======================================================================
MATERIAL DATA
Grade of steel           =  USER
Modulus of elasticity    =  205 kN/mm2
Design Strength  (py)    =  275  N/mm2
SECTION PROPERTIES (units - cm)
Member Length =    500.00
Gross Area =  161.30          Net Area =  161.30
z-axis          y-axis
Moment of inertia        :    30820.004        9239.001
Plastic modulus          :     2149.000         939.100
Elastic modulus          :     1926.250         615.933
Shear Area               :       81.998          51.728
Radius of gyration       :       13.823           7.568
Effective Length         :      500.000         500.000
DESIGN DATA (units - kN,m)   EUROCODE NO.3 /2005
Section Class            :   CLASS 1
Squash Load              :   4435.75
Axial force/Squash load  :     0.000
GM0 :  1.00          GM1 :  1.00          GM2 :  1.25
z-axis          y-axis
Slenderness ratio (KL/r) :         36.2           66.1
Compression Capacity     :       4078.2         3045.5
Tension Capacity         :       3426.0         3426.0
Moment Capacity          :        591.0          258.3
Reduced Moment Capacity  :        591.0          258.3
Shear Capacity           :       1301.9          821.3
BUCKLING CALCULATIONS (units - kN,m)
Lateral Torsional Buckling Moment       MB =  529.4
co-efficients C1 & K : C1 =1.350 K =1.0, Effective Length= 5.000
Lateral Torsional Buckling Curve : Curve b
Elastic Critical Moment for LTB,               Mcr   =  1416.0
Compression buckling curves:     z-z:  Curve b   y-y:  Curve c
Critical Load For Torsional Buckling,          NcrT  = 13898.0
Critical Load For Torsional-Flexural Buckling, NcrTF = 13898.0
STAAD SPACE                                              -- PAGE NO.    4
ALL UNITS ARE - KN   METE (UNLESS OTHERWISE Noted)
MEMBER     TABLE       RESULT/   CRITICAL COND/     RATIO/     LOADING/
FX            MY             MZ       LOCATION
=======================================================================
CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m):
CLAUSE        RATIO  LOAD     FX       VY      VZ      MZ      MY
EC-6.2.5       0.063     1     0.0     15.0     0.0   -37.5     0.0
EC-6.2.6-(Y)   0.018     1     0.0     15.0     0.0     0.0     0.0
EC-6.3.2 LTB   0.071     1     0.0     15.0     0.0   -37.5     0.0
Torsion and deflections have not been considered in the design.
_________________________