Extreme event on temporary barrier traffic control
Extreme event on temporary barrier traffic control
(OP)
I have been analyzing a reinforced concrete t-beam bridge to be replaced. Half of superstructure will be removed and other half will remain for 6 months while first half is replaced. Then this half will be replaced. This bridge was completed in 1951 with concrete strength 3 ksi and rebar Fy= 40 ksi. I have modelled this entire half and added the barrier at cut section of deck. The consultant is requiring me to put the HL93 truck on it plus the 10 feet wide lane load of 640 kips/ft plus an extreme event lateral load of TL-1 on the temporary barrier that is approved by the DOT and is bolted down to existing reinforced concrete deck. These are new rules for AASHTO LRFD design of new bridges not for a temporary 1/2 existing bridge to be removed 6 months from now. Are these new rules to be applied for old temporary bridges?
RE: Extreme event on temporary barrier traffic control
RE: Extreme event on temporary barrier traffic control
RE: Extreme event on temporary barrier traffic control
I had a phased deck replacement a couple years ago on a bridge built in the early 70s. I think I did check the effect of running a single lane of traffic on 2 girders, but I checked it according to the Standard Spec and HS-20 loading as that is what it was designed for and how it was Load Rated.
RE: Extreme event on temporary barrier traffic control
RE: Extreme event on temporary barrier traffic control
RE: Extreme event on temporary barrier traffic control
A traffic impact load is not quite like a seismic or wind lateral load -- even if you argue that there is less probability of it occurring in 6 months (which may not be valid in a construction zone scenario), the optics of a structural failure are very, very bad. That translates to high risk for the DOT.
Whether you check LRFD, LFD or ASD for the existing structure shouldn't make much difference for a concrete T-beam structure. I'd expect you might actually get some benefit from LRFD (although it will be a longer calculation).
Like OSU mentions, if the current bridge was rated at less than HL-93 before replacement began, you could probably use that to argue for a reduction of the HL-93 requirement, which would decrease the deck slab demand some.
I agree with the DOT -- most barrier details would have to transmit moment to the deck slab to be effective.
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The name is a long story -- just call me Lo.
RE: Extreme event on temporary barrier traffic control