Civil Engineering Mechanics of Materials Lab (Test of Builtup Beams)

1 California State University, Fresno Civil Engineering CE121L Mechanics of Materials Laboratory Lab10. Test of Builtup Beams 1. PRELIMINARY READING Section 7.3 in Hibbeler’s Mechanics of Materials textbook or section in builtup members in any Mechanics of Materials textbook. 2. OBJECTIVE To construct various wooden builtup beams with different shear strengths at the buildup interface, and test them to failure under flexure/shear conditions. 3. MATERIALS TO BE TESTED Several builtup beams are constructed by connecting two, 2 in. by 4 in. by 4 ft longitudinal members as flanges, to a 2 in. by 6 in. by 4 ft web as illustrated in the following picture. FIG. 1 Picture of builtup beam Several builtup beams will be constructed each with different strength at the shear interface. The strength will be varied by using nails at different spacing. 2 4. EQUIPMENT REQUIRED  The equipment required for this experiment is a Universal Testing Machine (UTM) with a capacity of applying 120,000 lb of force.  Hammer  8d (8 penny) nails  Tape measure 5. PROCEDURE After fabricating the specimens mark them at distances of 2 inches from each end and at 4.5 inches from the center on both sides as shown in the following figure.

FIG. 2 Marks on the specimens for test set up. Place the specimens (FIG. 3) in the testing frame and zero the deflection and load readings.

Gradually increase the applied load and collect electronically the magnitude of the applied load and the deflection as the load is increased. FIG. 3 Test set-up. 3 6. ASSIGNMENT Submit an individual memo report prepared with the standard format, including the following results: a) Make a graph of max load vs nail spacing. b) Develop a table showing the maximum shear in the beam for each case. c) Expand the table of part 6-b and calculate the shear flow occurring at the interface between the flange and web segments at failure. Estimate the shear force in each nail for each spacing. 7. SUGGESTED ITEMS FOR DISCUSSION  Discuss the failures observed.  Compare the calculated shear force per nail for different beams. Are those the same or different?