Cracked Beam Tube Enclosure

Following our influx of bees, M. Landry ordered an interior inspection of each beam tube enclosure (BTE) interior to document potential areas of ingress. R. Thompson with Apollo Mech is presently tasked with this inspection. During inspection of the X1 enclosure, roughly 5 sections -X of the X arm overpass, Randy observed cracking at the base of the interior of the enclosure. After further investigation he found 4-5 cracks running parallel of one another across the entire section at roughly the 10 & 2 o'clock positions. I was called to come give this section a second look. The cracks were also immediately concerning to me. The first thing I wanted to better understand was the interior width to assess if the section was shifting.

With Randy's help, I measured the interior spans of each end of the neighboring tube sections (4 measurements) as well as an additional 4 of the same spans of the tube sections on display outside of the LExC. On average, these spans measure 151" +/- .25". The section in question measures 154" at each end. Moreover, during installation Fred Raab has informed us that grouting was done on the BTE interiors to mitigate a "walking" effect that was causing misalignment between sections. This grouting has clearly separated from the BTE interior which confirms that there is in fact splaying of this section.

The current short term "fix" implemented by FAC and VAC has been the erection of scaffolding topped with planking across the 10' area of beam tube at risk of falling debris. This should act as makeshift roof. For the long term, R. McCarthy is currently consulting with structural engineers whom we hope can help us work up a solution to prevent further splaying.

Contained in the photos attached are measurements with appropriate labeling of each section (number counted from second door on X1 traveling -X), as well as a "+X" or "-X" which simply denotes if the measurement is on the +X or -X end of the tube section, photos illustrating the separation of the BTE interior from the as-installed BTE grouting, the scaffolding presently in place, the cracking at the footing/mid sections, and a LIGO Yelp review written in welders soapstone (circa ~96') near the splayed tube section.

C. Soike, E. Otterman, T. Guidry, G. Moreno, T. Sadecki, J. Vanosky, R. McCarthy