This graph (Hulsey, page 71) shows the Load Capacity of Column 79. That's basically how much weight (in kips, where 1 kip = 1,000 pounds) a given unbraced length of column can hold up before it fails. It's actually lots of different graphs for different temperatures. The top one 68°F being room temperature. Higher temperature and longer lengths of column have reduced load capacities.

Hulsey has marked off two lengths, 12'9" and 25'6". These represent the column when it either spans a single floor or two floors (for example if one floor had collapsed, or had been removed).

He then has added a short blue line on the 212°F curve marked "Nist Col 79 temp (392°F) All floors". Presumably this was intended to be on the lower 392°F curve, not the 212°F curve, but it makes little practical difference. This line is showing the difference in carrying capacity between a single floor and a double floor section of unbraced column. You can see it's not that different to the room temperature (68°F) curve, which shows (assuming the graph is correct) that heating of the column to 392°F is not going to make it fail.

Two slides earlier he shows this:

So this is showing column 79's Dead Load (the static load, i.e. the weight of the building held up by that column) of 5142 kips.

We can add this value to Hulsey's graph, as a thick blue horizontal line.

Now we can see where it intersects a floor marker (the red vertical lines) to see what temperature it would fail at for a given number of floors (1 floor being the normal case, nothing removed). So we can see that for 392°F (or 212°F) the column exceeds its load bearing capacity at 5 floors in length, which would be the same as the collapse of 4 floors.

In the NIST model, 9 floors collapse away from C79, as seen in Hulsey's slide 18. This is an effective length of 10 floors, or 127.5 feet, which is

*off the chart, *reducing the load capacity to less than half the dead load, hence causing collapse.

However on Hulsey's slide 82:

He says "

**UAF:Based on NIST Column Temperatures; col 79 did not buckle under gravity loading.**"

This is presented as a comparison with NIST's results. We have already seen how the other comparison in red text is meaningless (5.5" is a local differential movement, 2" is a global structural expansion). But is this a valid point?

The problem here is that the temperature is irrelevant. NIST has never claimed that the column buckled due to temperature, and specifically said that the heating of the column was not a factor.

(NCSTAR 1A, Page 53, Pdf page 95)
What they said, and Hulsey's graph confirms, is that removal of lateral bracing causes the column's load bearing capacity to be reduced to less than the dead load, and so it would fail. Here Hulsey and NIST seem to be in rough agreement. Since they agree on this point it

*cannot be used as a comparative point*.

The point should read something like "UAF: Col 79 did not lose lateral support, and hence did not fail" which is the actual substantive difference between Hulsey's study and the NIST report.

Hence the comparison is invalid and misleading.

It has also changed over time, for no apparent reason.

It seems that from his reading of the slide in the 2017 version of the presentation he intended it as a single point, not two:

Sept 2017, @1:03:54
However it's different from the previous version of his talk 11 months ago, where he lists it as a point of AGREEMENT, and not a consequence of the previous comparision:

References: