Rock anchor in pier footing

[SayGoodDay]

Hi everyone

I am a new engineer in Australia, sometimes I see the bridge drawings shows there are some rock anchors in the spread footing of the pier, and would like to ask what is the purpose for this? In my understand, the pier only resist axial loading, and in the model, the base of the pier is set as pin. (all horizontal loads are transfer to abutment).
So what is the reason for the anchors in the pier footing? (is it used to control the min. column design bending moment?)

Also, any good book/papers talk about the rock anchor design? (bond between grout and rock face).

Thanks.

SayGoodDay

 

[Dinosaur]

Bridge pier columns are usually considered fixed at the base and therefore transmit moment to the footing. Most pier footings are proportioned so that this moment would not cause uplift in any part of the footing. However, because bridge engineers are getting more ambitious and because seismic or other requirements are getting a bit more study in the codes and by designers, a method of resisting uplift has become necessary. Rock anchors are used to prevent uplift and to increase the shear resistence at the base of the footing.

Regarding the particular design procedures and such, I would check the foundation engineering forum and also contact some suppliers of rock anchors.

You will find that many engineers are moving to drilled shaft foundations as a more economical solution to several problems. - Good Luck