Jhinnie2
Structural
- Sep 28, 2021
- 9
Hi all, we're looking at designing a wheel bump-stop for a hefty mining truck. Originally there was a concrete stop connected to a reinforced slab (see image), but the stop was damaged and reo pulled out on the bump stop. We encouraged a concrete fix, but they want to replace it with a pre-fab steel solution because it cuts down shutdown time on the site. We proposed a stiffened box beam with 2x900WB wings welded to the ends (forms a 'U' shape).
We were hoping to secure it to the existing slab with shear key plates - but they didn't want to do that and they suggested Hilti anchors along the bottom flanges which we're looking at. We wanted to avoid bolting the edge closest to the back of the box beam because there's a ledge with rock mesh wall(dump pit where trucks dump material over) and we didn't want to shear the edge off and have mesh fail. The shear load is quite significant from the impact force (V=2500 kN / 34 bolts @ 200 spacing and gauge =75 kN - worst case truck hitting one side of the bump stop). It's obviously a lot of bolts we've shown. But the main problem we're having with Hilti check is concrete shear break-out and this is to AS 5216:2021. I think from memory in the ACI code you can get aditional capacity of around 40% by considering supplementary reinforcement perpendicular to the shear force.
As you can see in the image theres layers of N24 bars and some which are lapped from the original concrete bump stop before it was damaged. We looked it if we could consider the bolts as rebar to transfer the load back through the slab via tensile reinforcement (slab is about 14.5 m back to a buried wall which provides lateral support, and it's about 17.2m wide in plan view, with 8.5 m between the two 900 WB wings so truck can fit between wings and land wheels on the steel box section). We did a check considering from bolt group centroid to edge of slab as a deep beam and also another check with a strut and tie fanning out from the wings and checking reo in the tie direction and also back through the slab which it appeared okay (AS3600).
However, I'm not entirely sure how to confirm the anchors will act like reo and transfer load this way according to AS5216? Does anyone have any recommendations for this type of arrangement or any other ideas of how to get this shear resolved? We seriously think shear key would be the best option and less coring holes, but we've been asked to present this option regardless. We also thought about shifting bolts further away from edge to avoid the check requirement altogether, based on the 10 x Hef or 60 x d in the code, however this may prove to make the wings too long and affect the pullout check.
[Edit] Hoping to talk to Hilti as well to get their opinion.
Thanks in advance
We were hoping to secure it to the existing slab with shear key plates - but they didn't want to do that and they suggested Hilti anchors along the bottom flanges which we're looking at. We wanted to avoid bolting the edge closest to the back of the box beam because there's a ledge with rock mesh wall(dump pit where trucks dump material over) and we didn't want to shear the edge off and have mesh fail. The shear load is quite significant from the impact force (V=2500 kN / 34 bolts @ 200 spacing and gauge =75 kN - worst case truck hitting one side of the bump stop). It's obviously a lot of bolts we've shown. But the main problem we're having with Hilti check is concrete shear break-out and this is to AS 5216:2021. I think from memory in the ACI code you can get aditional capacity of around 40% by considering supplementary reinforcement perpendicular to the shear force.
As you can see in the image theres layers of N24 bars and some which are lapped from the original concrete bump stop before it was damaged. We looked it if we could consider the bolts as rebar to transfer the load back through the slab via tensile reinforcement (slab is about 14.5 m back to a buried wall which provides lateral support, and it's about 17.2m wide in plan view, with 8.5 m between the two 900 WB wings so truck can fit between wings and land wheels on the steel box section). We did a check considering from bolt group centroid to edge of slab as a deep beam and also another check with a strut and tie fanning out from the wings and checking reo in the tie direction and also back through the slab which it appeared okay (AS3600).
However, I'm not entirely sure how to confirm the anchors will act like reo and transfer load this way according to AS5216? Does anyone have any recommendations for this type of arrangement or any other ideas of how to get this shear resolved? We seriously think shear key would be the best option and less coring holes, but we've been asked to present this option regardless. We also thought about shifting bolts further away from edge to avoid the check requirement altogether, based on the 10 x Hef or 60 x d in the code, however this may prove to make the wings too long and affect the pullout check.
[Edit] Hoping to talk to Hilti as well to get their opinion.
Thanks in advance
