the stirrups calculated by Robot does not seem correct- Two Problems # and #2

[GabrieleNovembri1027]

Trying to use the Country kit just released I found two problems that seem to me critical.

Problem # 1 – the stirrup disposition don’t seem correct in engaging longitudinal bars in the cross sections;

Problem # 2 – In cases with q°>2 Robot gives an error message (I think) not pertinent

I will try to explain the situation.

Problem # 1

If you design a column using DM 14/01/2008 in the real reinforcement module in the stirrup shape definition probably something goes wrong. With the real reinforcement criteria you can switch on or off the “all tied longitudinal bars” option. If you don’t want all longitudinal bar tied, the program gives you the error message shown in the picture:

In this case, I suppose, there is an error in stirrup design. The stirrups calculated by the program don’t seems correct according to DM 14/01/2008 or Eurocode #8. The regulation selected is DM14/01/2008 and I don’t understand, in this case, why the program refers to Eurocodes. The stirrup arrangement is clearly incorrect for the Eurocode #8 (cited by the program) an the DM 14/01/2008 too (see figure).

The DM 14/01/2008 and the EC require respectively:

7.4.6.2.2 - “le barre non fissate devono trovarsi ameno di 15 cm e 20 cm da una barra fissata, rispettivamente per CD”A” e CD”B”.

5.4.3.2.2  - “b) The distance between consecutive longitudinal bars engaged by hoops or cross-ties does not exceed 200 mm”

The rules above don’t require that all longitudinal bar must be tied.

The only way I found to fulfill the requirements of the DM 14/01/2008 is to flag the “all Tied”option in the Reinforcement Patterns command as shown in figure.  The cross-ties highlighted in the figure however seem not required and may represent, I think, an unnecessary expense for the contractor.

In support of the above, I tried to manually delete some stirrups as shown in the figure. Robot, in this case, doesn’t report any error. It seems, in conclusion, that Robot is not able to correctly determine the connections that the regulations require for longitudinal bars.

Problem #2

If you use the a value of q°> 2 in the seismic disposition with “class B” of ductility the program always give you the following error (see also the  very simple model enclosed in the post):

I made some test.  The number and disposition of stirrups seem to be correct (even the number of stirrup is higher than actually required See problem #1). The massage itself seems not pertinent !!.

If I well understand the message: “L'armatura trasversale non è conforme alle disposizioni sismiche (EN 1998-1:2004, 5.4.3.2.2 (12)P)” refers to conditions in which the value of q is greater than 2. In this situation due the cited rule i cannot use the Eurocode #2 geometric rules for the stirrup disposition. Is the above a correct interpretation of the message ? is it pertinent in this case ?

Moreover, In this case I am asking for a “B” level of the ductility of the cross sections. Following the rules reported in the “Circolare n. 617 2 febbraio 2009” the local ductility of cross sections required in order to achieve a structure in the class B of ductility is guaranteed if the reinforcement disposition follow the geometric rules given for that level of global ductility and no ductility calculation is necessary.

In any case why Robot cannot calculate the correct disposition of stirrup in situations where q  is greater than 2 ?

Any Suggestion ?

Thanks

[Artur.Kosakowski]

Gabriele,

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