#82 S.J @ 20ö oc.-1950
#82 S.J @ 20ö oc.-1950
(OP)
I am assuming that these are 8" bar joists. I'll need to field verify but the site visit is a couple weeks away. Also the section shows a 2.5" plain concrete (no mention of rebar or mesh) over "steel forming" on top of these SJs with asphalt tiles on top. Did they actually used to use unreinforced concrete for floors






RE: #82 S.J @ 20ö oc.-1950
RE: #82 S.J @ 20ö oc.-1950
Design chart used was dated 1929, updated to 1948 (the chart updated to 1952 is the same except the 14' span goes up to 179 plf and the 15' span goes to 156 plf)
SJ82
8" deep Mr = 52,500"# Allowable End Reaction 1,900#
Approximate weight 4 plf
Span (ft) 10 11 12 13 14 15 16
All. Load (plf) 350 289 243 207 178 155 137
RE: #82 S.J @ 20ö oc.-1950
RE: #82 S.J @ 20ö oc.-1950
If the "form deck" is 1.5" or greater, then it is a permanent structural item, and perhaps composite with the concrete, depending on the design. There will probably be no shear studs present.
Mike McCann
MMC Engineering
RE: #82 S.J @ 20ö oc.-1950
Most of these 2 1/2" or 3" slabs included the 1/2" to 3/4" corrugated form in the total depth. I think the only way they work is by composite action, based on bond between the concrete and steel. These slabs were, as far as I know, never designed per ACI provisions, but rather were based just on experience. How do you design slabs on bar joists these days?
RE: #82 S.J @ 20ö oc.-1950
Probably similar down under?
Mike McCann
MMC Engineering
RE: #82 S.J @ 20ö oc.-1950
RE: #82 S.J @ 20ö oc.-1950
As far as form deck is concerned, the contractor sent over a pic this morning and indeed there is a form deck. See attached.
RE: #82 S.J @ 20ö oc.-1950
Thanks!
RE: #82 S.J @ 20ö oc.-1950
Starting with the 1946 (until 1949) spec, it changed to A7 (the allowable stress stayed at 18 ksi) and says "except that joists or parts of joists formed of strip or sheet steel shall conform to Grade C of ASTM. Tentative Specifications for Light Gage Structural Quality, Flat Rolled Carbon Steel (ASTM A245-44T or A246-44T)"
Starting with the 1949 (until 1951) spec, it stayed with A7 and says "except that joists or parts of joists formed of strip or sheet steel shall conform to Grade C of ASTM A245-48T "Tentative Specification for Heavy Gage Structural Quality, Flat Hot-Rolled Carbon Steel Sheets" or Grade C of ASTM A246-48T, "Tentative Specification for Light Gage Structural Quality, Flat Hot-Rolled Carbon Steel Sheets" or Grade C of ASTM A303-48T "Tentative Specification for Hot-Rolled Carbon Steel Strip of Structural Quality"
Starting with the 1951 (until 1955) spec, it stayed with A7 and says "except that joists or parts of joists formed of strip or sheet steel shall conform to Grade C of ASTM A245 "Specification for Heavy Gage Structural Quality, Flat Hot-Rolled Carbon Steel Sheets" or Grade C of ASTM A246, "Specification for Light Gage Structural Quality, Flat Hot-Rolled Carbon Steel Sheets" or Grade C of ASTM A303 "Specification for Hot-Rolled Carbon Steel Strip of Structural Quality"