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Anchoring a steel frame to a concrete base

Anchoring a steel frame to a concrete base

Anchoring a steel frame to a concrete base

(OP)
Hi,

A project calls for fixing a steel frame to a concrete platform. It is a student design prototype and is planned to be placed outside of a building in a lawn area for exhibition (approximately for 1 year). The frame weighs 300 kg. I have some ideas about fixing it but I am curious to know the opinions of more experienced engineers. Any suggestion would be appreciated. some photos are attached showing the dimensions of the frame, as well as it's schematic placement on the platform.

Thanks!
Kam





RE: Anchoring a steel frame to a concrete base

The most straightforward solution I can think of is to bolt it down using common concrete sleeve anchors, either with small clip angles bolted through the frame or a saddle that fits over the bottom frame pieces.

This might be beyond the scope of your question, but for loading, I suggest using at least the 200 lb load at 5ft up specified for the point load on a pedestrian safety fence (that's the loading in the AASHTO Bridge Design spec, anyhow). If it's in a public park or on a college campus, personally I would probably design for at least twice that loading - I've seen what young bucks with too much testosterone do to things like that when only their friends are watching.

RE: Anchoring a steel frame to a concrete base

Developing fixity requires that there is enough ballast created by the size of the concrete platform to resist the moment applied, Enough reinforcing or cracking strength in the concrete platform to resist the moment applied, enough strength in the connection of the steel to the concrete to resist the force couple - from the diagram, 2 of the vertical members would be in tension, and the other two in compression from the moment loading, make sure that the anchorage to concrete doesn't fail in tension/shear combination.

Your lateral loadings that would create the moment and shear load would be the governing load combination to include an impact load described by HotRod10, the wind load, and the seismic load.

RE: Anchoring a steel frame to a concrete base

Seconding calc junkie's point about the ballast. In the sketch, the pad looks pretty small compared to the tower. You need to make sure it will not overturn due to lateral loading. I started college the year the movie "Animal House" came out so maybe I am overly paranoid, but can picture 5 or 6 exuberant students purposely trying to tip it over. Someone could get hurt badly in that situation. An overturning evaluation with conservative loading and assumptions is in order. Unless the pad is several feet deep, I would neglect passive soil pressure in the analysis.

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