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# Re: Foundations for a 3-pinned arch stadium

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Foundations for a 3-pinned arch stadium
• From: "Jordan Truesdell, PE" <seaint1(--nospam--at)truesdellengineering.com>
• Date: Mon, 08 Oct 2007 08:41:06 -0400

In typical metal buildings, larger thrust magnitudes are handled by subgrade tie rods. I'm not too comfortable using passive soil pressure unless the magnitude is very low (less than the at-rest pressure). You should get pretty significant movement to activate the passive pressure. Though you'll get noticeable elongation in the tie bars as well, at least that can be calculated and - in theory - will not be permanent for transient loads. For example snow load taken by passive pressure is a permanent deformation of the soil, whereas is should be elastic with a tie rod. Now, that won't be perfectly true, as friction will prevent the tie rods from returning to zero deformation, but that friction will also provide a certain measure of safety.
```
Jordan

Kevin Below wrote:
```
For an indoor sports stadium with 200-ft span, I have seen several examples using huge curved glu-lam beam sections about 6 ft high, at about 30 ft spacing. These beams are assembled on-site into a 3-pinned arch configuration (a pin at each support, and a pin at mid-span.) The horizontal reaction at the base pins is enormous, and exceeds the vertical reaction. For example, 470 kips horizontal, and 405 kips vertical. The horizontal reaction is provided mostly by passive soil reaction on the perimeter wall.
```Is this good enough ?  Any thoughts on that ?
```
Is the passive reaction going to allow movement before it mobilizes ? Enough to be noticeable ? What about seismic effects on the soil behind the wall ? Will it cause the soil to move under the pressure from the arches ? What about a tie-rod (it would need to be big) under the sports surface, tying the 2 sides together ?
```
Kevin

kbofoz

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