Post installed anchor/plate drilling 6

[Pixy]

Who among you have tried drilling concrete pedestal with already base plate on top. That is. You will drill through the baseplate and concrete and even cut through any rebar inside (that is redundant anyway just believe me).

What is the cheapest rotary hammer wattage you could get for this? Let's assume there still space above to position the drill tool. That is why I need just compact and cheap one. The base plate has thickness of about 0.6". The rebars have either 0.78" or 0.39". Don't suggest extremely expensive gigantic drilling for oil exploration. It's just for rare one time use. I couldn't hire any tool.

Also the above anchors can be inserted into the baseplate, concrete base, right? or is there no anchor bolt that can be used with baseplate already in place?

 

[dik]

From my notes:

FASTENER (HILTI)
-CONTRACTOR SHALL CONFIRM ALL MINIMUM EDGE DISTANCES AND SPACING FOR FASTENERS CAN BE ACHIEVED.
-REINFORCING TO BE LOCATED PRIOR TO INSTALLATION. DO NOT CUT REBAR.
-MINIMUM ANCHOR EMBED LENGTH SHALL BE IN ACCORDANCE WITH MANUFACTURER’S RECOMMENDATIONS OR AS SPEC’D.
-ANCHORS TO BE SECURED TO BACKING CAPABLE OF DEVELOPING STRENGTH OF ANCHOR. DESIGN ANCHOR CAPACITY HAS NOT BEEN VERIFIED. CONC STRENGTH TO BE 20MPA OR GREATER. CONCRETE SHALL BE SOUND AND CRACK FREE WITHIN A RADIUS OF 8” FROM THE FASTENER.

-ADHESIVE ANCHORS FOR CONCRETE TO BE HDG AND CONFORM TO ASTM F1554, GRADE 55 S1 OR HILTI HAS-E-55. SIZE AND EMBED AS SPEC’D. SECURE USING HILTI HIT-HY 200 ADHESIVE.
...

-DRILL AND CLEAN HOLES IN ACCORDANCE WITH MANUFACTURER’S RECOMMENDATIONS.
-INSTALLATION TORQUE SHALL NOT EXCEED THE TORQUE RECOMMENDED BY THE SUPPLIER.

I address other Hilti fasteners, but the first one is the HAS. I always spec Hilti or an app'd alternative. The baseplate should already be pre-drilled and the hole location should be checked for rebar interference. I can imagine it being difficult drilling down through a length of #11 bar.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Tomfh]

The cheapest rotary hammer at my local hardware store could do it.

You will struggle if you hit rebar, and will likely need to try again in a different spot.

 

[Pixy]

Any rotary hammer drill tool at hardware can do it? Can you give any wattage? Because once I buy it and it can't penetrate the plate. I can't return it anymore.

How long would it take to drill one hole that is 0.7" diameter with baseplate thickness of 0.6" right on top of the concrete base already installed? One hour? Two hour? So I can estimate. It's just to add more anchor bolts to existing ones with sufficient required distances met.

 

[Tomfh]

Provided it also has drill function it will be able to do it. You need a cutting bit for the plate, and then a hammer bit for the concrete.

My rotary hammer came with an adaptor to allow it to take regular drill bits, Eg for drilling steel plate.

 

[Pixy]

Adaptor like above?

I wonder if a drill tool with fixed dedicated three-jaw chuck is better for steel? what you think?

What is the wattage of your rotary hammer drill set? 500w? 2000w? 4000w?

 

[dik]

You may have difficulty drilling through 1/2" plate with even a 1/2" drill bit with a cheap hand drill. The holes should be pre-drilled.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[XR250]

The cheapest Bosch Bulldog rotary drill will be fine for the concrete. I have used mine for years on all sorts of projects. You will need a a bit that is designed to cut rebar. For drilling the plate, it will take a while. Start with a 1/4" bit and then work up pregressively from there. You will want to drill the plate before it is on the concrete or you will trash your bits.
If you have access to a drill press, it will be easier. Better yet - a mag drill with coring bits.
Might be cheaper to hire someone to do this for you.

 

[Pixy]

The baseplate is already on top of the concrete base with insufficient anchors. Can't remove the baseplates from concrete as it has loads already. Why do you say it will trash the bits? Are you saying it is no longer possible to drill 0.6" baseplates and then another 5 inches concrete to anchor the additional Hilti epoxy or chemical bolts?

It is just to get additional shear resistances. if drilling is totally impossible. Would welding the 4 sides of the concrete pedestal with baseplates (imagine steel cap) give competent horizontal shear resistance? Has this steel shear cap ever been done before?

 

[MJCronin]

Pixxie,

Instead of posting pictures from your local Home Depot, can you post pictures of the offending baseplate and the concrete pedestal ?

This would probably help you get better answers to your questions about steel detailing and steel plate design

My opinion only ...

MJCronin
Sr. Process Engineer

 

[Pixy]

The baseplate loads are rafters with thin metal and walls at sides. The anchors are near the edge of the baseplate. It has sufficient tension capacity but lacking shear strength. What would happen if we put 4 baseplates welded like a cap put on each concrete top welded to existing baseplate at top (the concrete base or actually column is 9 foot long and size 19" x 19" with 12 pcs of 0.78" longitudinal bars inside). It was supposed to support 2 more story but the client has no more budget and decided to just put thin roof on it. The contractor incorrectly put anchors near edge and shear capacity is lacking). Would the steel cap have sufficient shear capacity? Has anyone seen a steel cap put before?

 

[Pixy]

It is the masonry walls that will be put in the building perimeter that require additional shear resistances in the baseplates.

We are discussing what kind of grout to put at the 4 side baseplates welded to the top baseplate (imagine a steel cap). But if the Sika grout were to crack at the sides and fell off decades later. The steel cap would become loose. This is even if one has to put HAS-U 0.6" bolt per side of the steel cap. This is due to the bolts being able to bend when grout was gone contributing to less shear resistance (same case when your top baseplate has grout partially gone bending your anchors during shear).

We would like to see guidelines for steel cap design. Have you seen anything like it before? There is minimal moment but we are simulating moments putting stress on the steel cap. The welding at the sides would be engaged for certain moment of the whole steel cap. But then, is it not the weld itself in 4 sided baseplate cap in any concrete base would create more shear resistance than the shear resistances of the anchor bolts?

If full welding of the 4 side plates to top plate is competent. Would the side baseplate just crack the top concrete or break it off? But then shear resistance of the concrete at side is like Vc of a beam. And Vc is huge. What can you guys comment about this all? Would a steel cap give reasonable shear resistance in this unique setup? It's a one time problem only that is why asking for tips, guys. Thank you!

 

[NewbieInSE]

What if you cut the baseplate at the middle where there is no bolt. After cutting you drill post-installed anchor one on each side. Then you make a 0.6" thick short piece of the baseplate (which you already cut)keeping a hole so that you can insert it from the top of the post-installed anchors. Then weld the short piece baseplate with the one existing.

Is this technically acceptable and doable?

 

[Pixy]

This was top of the column with 0.63" thick baseplate. Long side is 19.68", short side is 15.75". There was no longer space to put post instaleld anchor bolts. In fact, there was a hole in the middle before supposedly to insert post installed anchor but it hit the top rebars and so not used.

The existing anchors are too near the edge. Imagine shear coming from left side, only the left anchors would be engaged. The anchors used were Grade 36 and 0.63" in diameter and 7 inches long put about 3" from edge. They should be at least 6 inches inside but contractor years ago inserted them just to cover the top of the column.

The I-beam takes up the middle space, so we can't put post installed anchors on top.

What would be the problem by welding 4 side plates to it all fully welded together like a steel cap? And Hilti HAS-U Gr. 55 0.63" diameter anchors would be put at least 2 pcs each side? The shear capacity of the shear cap would be much more than any post installed anchors. Is it not? They will just be used to support top of masonry walls to be raised at perimeter. Masonry walls were designed but only hardiflex put because then client couldn't wait for long time for masonry then.

 

[NewbieInSE]

Yeah, wrapping the column top and anchoring it to the RC column would solve it, I believe. In that case, the RC column should be adequate, which it is.
But when axial load comes, won't your post installed bolts be loaded in shear? Or is it ok to say that only the cast in istu anchor bolts will carry this tension?

 

[Pixy]

Assume the above is the steel cap on top of the column.. If there is eccentricity or axial load on the right. Then the steel cap can rotate clockwise (esp if there is grout at sides that has broken) causing the cast in anchor bolt at left to be in tension, and the anchor bolts at sides to be under shear. That's a good analysis. But won't the side post anchor bolt have elastic range under shear too? Remember in normal bolt or steel, rebar. Load below the yield strength has elastic characteristic and return to original shape, until it reaches the yiield strength. How do you characterize the elasticity in shear in the bolt?

Can't you make the cap so rigid it can't rotate at all? In your experience, what thickness of baseplate when baseplate can't deform anymore?

 

[NewbieInSE]

 

[Pixy]

Uplift huh.

The side post installed anchors will be below the failure cones of the cast in situ top anchors so the cones won't intersect.

Another idea. What if side shear lugs would be used on all 4 sides. There are 12 pcs of 0.787" rebar inside to intersect any shear lug failure plane. The column was supposed to support 2 more story but client didn't proceed and instead just thin roofed it.

I think side shear lugs would resist any uplift. What have you heard about side shear lugs?

 

[Ingenuity]

Is the shear only parallel to the roof rafter moment frame beams, with no significant shear perpendicular to the moment frame?

 

[Pixy]

The shear is from seismic story shear. So it's all directions, parallel, perdendicular, up and down. Currently there is only very light cladding wall (even though it's designed for masonry wall). All will be replaced with masonry wall for fire protection. So the post installed anchors will be to resist the lateral movement of the masonry walls.

Problem with shear lug is it's welded. And putting HSS in side baseplate with epoxy grout inside may be problematic. How to insert the epoxy grout (from a hole in the side baseplate). So anchor bolts will still be more dependable. 2 pcs of 5/8" anchor bolts per side of the column will give resistance of 17 kips. So by bolting all sides, it would give sesismic resistance of about 17 x 4 = 68 kips. This may prevent the wall from falling over.