Solution to Problem 130 Bearing Stress

Problem 130
Figure P-130 shows a roof truss and the detail of the riveted connection at joint B. Using allowable stresses of τ = 70 MPa and σb= 140 MPa, how many 19-mm-diameter rivets are required to fasten member BC to the gusset plate? Member BE? What is the largest average tensile or compressive stress in BC and BE?





Solution 130


Good day. I would like to ask a clarification max tensile/compressive stress on the members.
Why did we use A=Area-dt for member BC, but for member BE, we just used the given area of 1780?
Maraming salamat po.

In reply to by Mang Johnny (not verified)

The member BE is in compression, thus the whole cross-section is effective. The load transfers through the main area + bearing area, as the fastener is pressed against the hole area. Imagine as if the fastener was "clenched" between two semicircles representing a hole halves. The compression load transfers through the fastener further.

The member BC is in tension. In static analysis this check is commonly referred as "Net Area Tension stress" and accounts for the holes area (and usually stress concentration, but it's omitted here), that needs to be excluded from a gross (total) area. In this scenario, the fastener is pressed against either side, but the opposite hole side extends away from it and deforms in oval shape (it is in tension, remember?). Thus this hole area doesn't contribute into the total strength (imagine if there were no fasteners at all, but only holes), so we exclude it. It acts as a perforated toilet paper :D