Deep beams

Deep beams assumptions

Deep beams are registered in the Code as - NEN-EN1992-1-1#5.3.1(3).

The requirements for minimum reinforcement according to the NEN EN1992-1-1#9.2.1.1 article are applied.

The design requirements described in article Cement'93 Nr.3 (77) are also implemented.

 

Lov definition

Lov definition - complex situation:

 

 

In this picture one structural member is shown. There are two points in which MEd = 0 (0.588; 18.21).

To decide which calculations rule (deep beam or ordinary beam) must be applied we need parameter Lov.

It is the distance between the M0 points in which MEd = 0. In a standard situation this distance will be found somewhere between the defined supports (in field). In this example spring supports are defined so we don't have M0 points between two defined supports (in field). So, for this situation, Lov = M0_right – M0_left = 18.21 – 0.588 = 17.622 (m).

 

Height of decisive section for deep beams calculations

Height of decisive section for deep beam calculations - complex situation:

In the picture above you can see that two different section types for this structural member are assigned: R240x3000 and R240x15600. Deep beam recognition depends on the ratio Lov/h. In this case we have one Lov value and two values for h.

For deep beam recognition in this situation a procedure will be performed for each type of section separately. It is possible that a part of the member located  between the Mo points will be recognized as deep beam and the other part as a standard beam.

 

Calculation rules

Calculation of deep beams:

• NEN-EN1992 and EN1992

  • Lov/h ≤ 3.0 than deep beam

  • Lov = distance between moment zero points in the field

  • For  haunches Lov = 2a according to the CB4#3.1.1 page 59.

If there are no zero points of the field moment that is calculated,  than  the Lov points on the left and right side of the other fields will be detected. This means  that Lov>L of the field.

See example CB4#4.4 page 98.

 

• NEN6720
  • Lov/h ≤ 2.0 than deep beam
  • Lov = distance between moment zero points in the field

  For haunches Lov = 2a according to the NEN6720#8.1.4.

 

Calculation of "z" for static definite beams:

• NEN_EN1992 and EN1992

  • z = 0.2 l + 0.4 h ≤ 0.6 l

  • z ≤ 0.8 h

  • l is the distance between the supports

For haunches z = 0.2 l + 0.4 h ≤ 0.8 l

l = 2a according to the CB4#3.1.1 page 59

h = hc

 

• NEN6720

  • z = 0.2 l + 0.4 h ≤ 0.6 l

  • l is the distance between the supports

For haunches z = 0.2 l + 0.4 h ≤ 0.8 l

l = 2a according to the NEN6720#8.1.4

h = hc

 

Calculation of "z" for static indefinite beams:

• NEN_EN1992 and EN1992

  • z = 0.3 lo + 0.3 h ≤ 0.75 lo

  • z ≤ 0.8 h

  • Lo = Lov for fields.

  • Lov = distance between moment zero points in the field

If there are no moment zero points in the field that is calculated, the Lov points on the left and right side of the other fields  will be detected. This means that Lov is >L of the field.

See example CB4#4.4 page 98.

• Lo = 1.5 Los  for the supports

  • Los is the distance between the moment zero points of the supports moment

 

• NEN6720

  • z = 0.3 lo + 0.3 h ≤ 0.75 lo

  • Lo = Lov for fields

  • Lov = distance between the moments zero point in the field

  • Lo = 1.5 Los for supports

  • Los is the distance between moments zero points of the support moment

 

Calculation of shear force for static definite and static indefinite beams:

• NEN-EN1992 and EN1992

  • The same formulas as for standard beam see also CB4#2.2 page 77

  • vEd = Ved/(b d)

  • d = h – 0.5*x

  • x = minimum value of 0.2*l and 0.2*h

  • In VRd,s formula you should use z = 0.9 d

 

Calculation of side and vertical reinforcement for deep beams:

• NEN-EN1992 and EN1992

  • NEN-EN 1992-1-1 art. 9.7

  • Distance horizontal and vertical  ≤ 300 or 2 b

  • Amount of reinforcement horizontal and vertical  ≥ 0.1%

  • See also CB4#2.3 page 77-78 Fig. 8.