Concrete Column in seismic zone 4 (AASHTO LRFD 2012, Bridge Design Specifications 6th) 1

[YunJW]

Hi all,

In "AASHTO LRFD 2012, Bridge Design Specifications 6th", there is rule for splice in column of seismic zone 4 as below.

'clause 5.10.11.4.1f - Splices
The spacing of the transverse reinforcement over the length of the splice shall not exceed 4.0 in. or one-quarter of the minimum member dimension.'

In connection with the 5.10.11.4.1e - spacing of transverse reinforcement for confinement, I understood that it is applied inside the plastic hinge region. However someone talked to me, it should be applied all region of columns.

Could you please help me?
what is more precise interpretation?
or where do this rule come from?

Thanks in advance.

 

[BridgeSmith]

You only have to meet that requirement in the plastic hinge zones, but many times it's easier to detail, and I feel better, just keeping the same reinforcement through the entire column, just in case someone reads the plans upside down or something.

The rule exists to maintain the integrity of the column after the concrete is all broken up by the plastic hinging. We usually find we meet that requirement anyway by the time we meet the other requirements (EQ. 5.6.4.6-1 & Eq. 5.11.4.1.4-1). The sometimes trickier requirements to meet are for the spiral laps per 5.11.4.1.6 (welded, mechanical or no laps) and the extension of the spirals into the adjoining members (5.11.4.3). We usually specify the spirals be continuous, which apparently is easily accomplished using deformed bar coils.