Flexure Capacity of Compression Chord

Two joist thicknesses were considered in this study, 0.046 in and 0.035 in. Table 1 summarizes the mechanical properties of the sheet steels used to fabricate the joists. To preclude failure of the

Fig. 5. Typical clinch failure.

Table 3. Flexure test results.

Test

No.

Joist

Thickness

(in)

Joist

Depth

(in)

Joist

Span

(ft)

wtest

(lb/ft)

wcomp

(lb/ft)

wtest/wcomp

2-5

0.035

12

20

176.8

178.5

0.991

2-6

0.035

12

20

203.0

178.5

1.137

3-8

0.035

12

18

202.0

221.0

0.914

3-9

0.035

12

18

216.0

221.0

0.977

3-5

0.046

12

20

249.0

239.0

1.042

3-7

0.046

12

20

249.0

239.0

1.042

compression web, as occurred in the clinch study, the web was reinforced or embossed as shown by Figure 3. Clinches were of type “R” spaced three inches on center.

A total of six tests were performed in this study as summarized in Table 3. Figure 6 shows a typical joist failure. The tested capacity, wtest, was compared with the computed capacity, wcomp, where the computed capacity was based on the AISI specification (North, 2001). On the average, the flexure capacity of the joist was achieved for both thicknesses of joist. Also, the tests verified that the joist behavior is best modeled as a beam and not a truss.