topic Long term deflection inconsistency in Robot Structural Analysis Forum

Long term deflection inconsistency

Anonymous — Mon, 30 Apr 2018 10:08:05 GMT

Hi all,

I am a designing a RC 400mm Slab at the roof level of my building and I am encountering some issues (Story 3 = 75.3m). When I enter the Slab required reinforcement module and run for my ULS Case (Case 10 - 1.35Gk + 1.5Qk) and SLS Cases (Case 11- 1.0Gk + 1.0Qk, Case 12: 1.0Gk + 1.0Qk SLS:QPR), the maximum area of steel required to meet the ULS requirements and to achieve 0.3mm crack width are:

X- = 1961

Y- = 8066

X+ = 2653

Y+ = 12694

There is one specific region in the slab where the cracked long term deflection is greater than the limit of 30mm I have set as shown in the first image above. So when I adjust the reinforcement to meet the deflection criteria, rather than having just that area where the deflection is higher than the limit adjusted, the reinforcement is also adjusted in regions where the long term deflection is already < 30mm. This does not make sense to me. I would appreciate any input as to why this is happening. I have attached my model for your reference. Thanks

https://wetransfer.com/downloads/3489e3537d9bd01d1d99aa235c154e9620180430093354/da401c

Re: Long term deflection inconsistency

Artur.Kosakowski — Mon, 30 Apr 2018 15:31:23 GMT

Hi @Anonymous

I'm not able to look at your model but in general adding reinforcement in one location is not as effective as adding (less) steel over the whole slab. Please watch the recording of the 5th Robot webinar.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: Long term deflection inconsistency

Anonymous — Tue, 01 May 2018 09:41:44 GMT

Hi Artur,

Thanks for your quick response. I will watch the webinar again and if you get a chance it would be great if you could have a scan through it. Thanks.