EC-2 lapping bars 1

[Roma123]

Hello,
I have a question about tension laping bars described in EC2.
EC 2 states:
The arrangement of lapped bars should comply with Figure 8.7:
- the longitudinal distance between two adjacent laps should not be less than 0,3 times the lap length, l0;
And in the other parapraph states that if the percentage of lapped bars relative to the total cross-section area is more than 50perc. than α6 is 1.5 (coefficient increasing anchorage length).
So if i fulfill in above noted first statement (longitudinal distance between two adjacent laps....) i never get the second statement (percentage of lapped bars relative to the total cross-section area is more than 50perc....)? So why is it mentioned in EC2? Maybe i can use second statment and ignore first?

 

[ukengineer58]

From memory They are two separate conditions. The 0.3 is distance between two bars considered to provide continuity. So if the lap length is x then the max distance is 0.3 times x. The 50 percentage relates to how many bars are lapped in a section. So if you stagger laps you could have less than 50 percent, although unless its a large area and small laps that may be difficult.
If the distance between bars lapped is greater than 0.3 you need to increase the lap accordingly.

 

[Roma123]

Thanks ukengineer58 but i'm not sure i understand you right. EC-2 states that longitudinal distance between 2 adjacent laps should not be less than 0,3, it can see from previous attached "1.png" picture. So in that condition i never get the percentage of lapped bars relative to the total cross-section area is more than 50perc. But if there is mentioned condition what the percentage of lapped bars relative to the total cross-section area is more than 50perc. than α6 is 1.5 i can lap my bars like in attached picture below (with no stagger) simply taking coefficient α6 is 1.5 ?

 

[ukengineer58]

Sorry just picked up code and yes I was mixing the clause up with point 1 under (3). I'm not sure now to be honest are you uk based? We never detail to that as it would be very difficult in a lot of structures and certainly on site they don't want to be measuring that out every lap in you have a slab for instance and stagger the laps everywhere. personally I am uk based and rather than work out the lap every time using the equations I use the table in 'how to design concrete to euro code 2'. That gives you basis lap calculated and allows you to reduce it allowing for concrete and stress in bars. Yes I am also confused how you can have 100 percent lap if you have them staggered in that manner. As I said I use the table in the how to publication, the lap lengths are already a lot more generous than in the old British standard and as far as I know nothing collapsed that was designed to British standards due to to short laps. Unless the rebar concrete rebar bond knows somehow it is designed to eurocode and says 'that's it I'm failing'

 

[Roma123]

Thanks ukengineer58, with this question i'm just wanted to know does EC2 allow laping bars without staggering, and if it's possible how it increase laping length. I saw that table in 'how to design concrete to euro code 2' and there is shown in final line - 100% lapped in one location. So if i understand right according to this table i can lap bars without staggering and use laping length indicate with line - 100% lapped in one location.

 

[ukengineer58]

Thats what i do. For right or wrong