My reply as the followings
>> our office generally specifies an all thread rod with a nut-washer-nut at the bottom as opposed to a headed bolt.
The anchor rod shall NOT be all threaded and this will create a big problem. The correct way is to thread both end tip as needed, see Page-1 of attached PDF files.
Ideally you shall allow the anchor rod free to stretch in between and only two ends get engaged. If you thread the rod full length, it will increase the bond between rod and concrete and this bond is not desirable as it will relax with time, and gradually your anchor bolt will lose the pretension. The correct way is allow the anchor rod free to stretch in between and only two ends get engaged. We normally use sleeve or tape wrapped to debond the center part. See Page-2 of attached PDF file. This is also the ductility requirement as per ACI 318-11 D.3.3.4.3 (a). We call it stretch length or gauge length in ASCE 7-10, see Page-3 & 4 of attached PDF file.
>>Portland Bolt has an article on their website stating that their testing indicates that an all thread rod with a nut is >>not as strong as a headed bolt.
I would say that mostly applies to steel connection case, not anchor bolt. Anchor bolt is different as it’s fully contact with concrete in cast-in-place anchor bolt. The rod, head and nut are fully contact with the surrounding concrete. There would be no reduction, on the contrary, it gets local stress hardening and the concrete bearing get 8 times more, see the anchor rod head pullout resistance formula ACI 318-11 D.5.3.4 Np=8*Abrg*fc'
Plus, when we design anchor rod material capacity, we consider thread reduction up to 30% and use effective shank area Ase, so there is no point for you top worry about this, right ?
>> I was wondering what other engineers think about this and how others specify these types of attachments.
Just go for the detail of Heavy Hex Jam Nut – Head Plate- Heavy Hex Jam Nut as shown on Page-1 of attached PDF files. In this way we have the flexibility to use Hex, Heavy Hex, Square, Hardened Washer and Custom Head Plate to create different Abrg to suit our design needs.
anchor bolt design per ACI 318-11 crane beam design