Lapping splice of reinforcement in tension in seismic beam

[HuynhKeshley]

I have a continuous RC beam which is part of the Intermediate Moment Resisting Frame.
Lapping splice is being used.
Normally, the top bars are lapped at the mid-span, and bottom bars are lapped at the support. I understand that this is due to the spalling/cracking of concrete during seismic event.

However, is it possible to use lapping splice of top bars at the support where there is negative moment?
What will be the condition to make it happen?

Thank you.

 

[r13]

I consider this is a "best practice" issue. Did you consider the problems the congestion at the highest stressed areas may bring, especially the reduced steel surface area for good bonding. I used to avoid splice at mid-span and end support for both top and bottom main reinforcement.

 

[HTURKAK]

The lap splicing of top bars at the support shall be avoided.. The splices SHALL BE away from the hinge locations. The lap splice will not be effective and unreliable when the cover spalls as you said.

Provide Continuous bars in the top and bottom at hinge locations due to reversal of seismic effects..

 

[Agent666]

Normally, the top bars are lapped at the mid-span, and bottom bars are lapped at the support. I understand that this is due to the spalling/cracking of concrete during seismic event.

This practice is more to do with what has traditionally been accepted/implemented for gravity loading. It has nothing to do with seismic.

As Hturkak noted, the splices need to be located away from hinge regions under seismic loading, so you need to evaluate where the hinges form and the lengths and detail to the rules set out accordingly. Typically this will be documented in whatever standard you are designing to.

The idea is that you place the splices away from the areas where your beams may be stressed into the inelastic range under cyclic loading which can affect the bond between the bars and the concrete leading to bar slip and a loss of stiffness.