Development length schedules

[slickdeals]

How do your firms show development length and lap splice schedules on construction drawings?

Do you have the most conservative value calculated prior to the modifiers applied and spell out how the modifiers apply? For example, a #5 bar in 5000 psi concrete has a hook development length of 15" but if spaced > 6db and adequate side cover, this value can be reduced to 7.5". So, what value would your tables show?

As a firm, we have opted to show the most conservative length and apply the modifiers to check if hooks develop in a member, but the table values look stupid at first blush for 318-19 (i.e., longer than the member thickness). It does look like sanity will return when 318-25 gets adopted.

 

[phamENG]

Not doing much concrete, but my schedule has a class a and class b length for each bar for the weakest concrete being used on the building. So if I miss one, it's going to be conservative.

Then, if I have a situation that can be modified and should be modified, I'll call out that length in a detail.

 

[BridgeSmith]

We have a lap table in our spec book, which uses the worst case lap lengths. That is only used if they're adding a lap that's not planned. All of the planned laps are called out on the details or provided by default, based on the bar lengths and clearance specified.

 

[cliff234]

"It does look like sanity will return when 318-25 gets adopted."

slickdeals - What is changing in 2025?

 

[Celt83]

@cliff234:
Several changes have been put forward for consideration the LA Tall Buildings Structural Design Council has a summary of some of the proposals in Appendix D of their "An Alternative Procedure For Seismic Analysis And Design Of Tall Buildings" document: Link

 

[slickdeals]

Cliff - the public comment ACI 318-25 had the hook development lengths returning to ACI 318-14 or close to it. In addition, like Celt83 mentioned, a lot of the crazy seismic amplification is getting scaled back. It will still be worse than before, but much better than 318-19. Hopefully they'll issue an errata to ACI 318-19.

 

[bugbus]

We usually combine development and lap lengths into one set of values, based on the latter. I wouldn't trust builders to choose the right number in the right situation. There are plenty of situations I think where it is not really clear whether a development length or lap length should be used.