Impact the same as dynamic allowance?

Is the dynamic allowance the same as impact? The reason I ask is because it appears that the SE Practice problems refer to a problem that asks for impact negative moment of a slab at a support. It appears that this is an error.

Answering my own question here. The answer is that the DLA replaces the impact factor.

McEngr said:

Is the dynamic allowance the same as impact? The reason I ask is because it appears that the SE Practice problems refer to a problem that asks for impact negative moment of a slab at a support. It appears that this is an error.

Click to expand...

I don't use dynamic allowance for anything, I use impact factor for LL. They are different animals. I think chap 3 of AASHTO talks about this.

ipswitch said:

McEngr said:

Is the dynamic allowance the same as impact? The reason I ask is because it appears that the SE Practice problems refer to a problem that asks for impact negative moment of a slab at a support. It appears that this is an error.

Click to expand...

I don't use dynamic allowance for anything, I use impact factor for LL. They are different animals. I think chap 3 of AASHTO talks about this.

Click to expand...

Depending on what design standard you use. ASSHTO LRFD calls the impact factor "dynamic allowance" Other bridge specs call it impact factor. I just call it impact factor.

ipswitch, you forced me to double check myself yet again. I'm glad you posted again as I was going to be scratching my head for a few days trying to figure out the difference again.

I think the word allowance is a big problem from an interpretation standpoint. The implied meaning is that it is optional, but it clearly is a requirement.

AASHTO just changed terminology and the way it is computed. AASHTO Std. Specs used a different formula that was dependent upon the span length. LRFD uses 1.33.

Thank you ADB. It helps to have forums like these to get clarification. I hope to pay it forward during this study process...

ipswitch said:

ipswitch said:

McEngr said:

Is the dynamic allowance the same as impact? The reason I ask is because it appears that the SE Practice problems refer to a problem that asks for impact negative moment of a slab at a support. It appears that this is an error.

Click to expand...

I don't use dynamic allowance for anything, I use impact factor for LL. They are different animals. I think chap 3 of AASHTO talks about this.

Click to expand...

Depending on what design standard you use. ASSHTO LRFD calls the impact factor "dynamic allowance" Other bridge specs call it impact factor. I just call it impact factor.

Click to expand...

I was shooting at the hip the first post until I checked the AASHTO this morning when I arrived at the office.