lap length of 460 grade rebars

[sag04]

What is the minimum lap length of 460 grade rebars in a grade beam with concrete strength 45 N/sqmm. the BS 8110 gives the different values based on the concrete strength but only for 25 to 40 concrete strength.What is the maximum allowable size of rebars together at lap section in a layer in terms of percentage of beam section
thanking you all in advance

 

[Zambo]

I also want to know the answer to the first part of your question. We have grade 80N/mm2 concrete and T32 rebar. I am hoping that the lap length is less than 1000mm, but I cannot find a reference.

Zambo

 

[3dboy]

what are all those numbers in english units?

 

[Zambo]

3dboy,

they are English (UK) units. Are you asking for US units? The thing is the question relates to British Standards so no advantage in using data from US publications.

Zambo

 

[3dboy]

They are SI units, not english. did not know it was british standards. If its not ACI 318 I'm no good to you.

 

[EndEng]

It's a good question and I'm not sure there's an answer, but, given that as your concrete grade stress inceases, your lap lengths reduce. So if you go off the recommendation for grade 40 you pretty much can't go wrong.

Without stating the obvious, your final lap length will depend upon Bar diameter and type (deformed?) as well as the 2 cover cases(1.4 and 2.0 factors).

I have a handy "Allied reinforcements" leaflet that has all bar data tabulated and makes it real easy, no calcs.

 

[pappyirl]

BS 5400-4:1990 Table 15 gives a value of 3.3 N/mm2 as the ultimate anchorage bond stress for a concrete grade of "40 or more".

Given that a lap length should at least equal the anchorage length the code seems to suggest using the lap lengths for C40.

Having said that S.S Ray in "Reinforced Concrete Analysis and Design" shows a table listing tens/comp lap lenghts of 27 x Bar Dia. for C50 concrete. No reference is given but the draft EC4 does give bond stresses for grades up to C50.

Prudence as per EndEng is probably the best course of action.

 

[MRP999]

use 3.12.8.3 this is where the table3.29 derived from

 

[uyare]

Question:

What is Class A and B Splice? Where are they used? Can also someone clarify the top bar ? For some reason I cannot comprehend with its standard description of " .... 300 mm below.....

Is there a top bar at the column? Thanx

 

[apsix]

I'm not sure that the questions relate to BS8110, I couldn't find any reference to splice classes and the top bar definition.

Some codes recognise that bars with more than 300mm of concrete below them are subject to a reduction in bond strength due to settlement of the fresh concrete and an accumulation of bleed water along the underside of the bar.