Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...

44Along with rectangular tensile coupons taken from eyebars of the Bell FordBridge, round tensile coupons were also tested from the Adams Mill Covered bridge.The members from this bridge consisted of round diagonal tension rods. Similar to theeyebars, these rods were measured and sectioned into pieces. The pieces where thenlabeled and test specimens were removed and machined from these pieces. Thedimensions of these specimens can be seen in Figure 3.9. The tensile coupon specimensused in testing were considered to be non-treated standard specimens. Figure 3.13 is aphotograph of a typical round tension testing coupon.3.5.2 Testing Procedure for Tensile Coupon TestingAfter the tension coupon specimens had been machined, the coupons were thenprepared for testing. To begin, a gauge length was marked at the center eight inchesalong the coupon sample with a ruler and some scribes, so the markings were permanent.The center point of the sample was also scribed along with the two-inch placement of theextensometer along the edge of the sample. These scribe indentations were thenintensified with a black marker for ease of viewing. Once the sample was scribed, thewidth and thickness of the sample was measured using a micrometer at nine differentpoints along the gage length. These values were then averaged and multiplied together toobtain the average area along the gage length of the sample to nearest thousandth of asquare inch.Measurements Group CEA-06-250UN-350 type strain gages were applied to bothfaces in the center of the testing coupons. These strain gages were used to measure verysmall changes in length while testing the tensile testing coupons. They were appliedusing the appropriate methods described by Measurements Group, Inc. Themanufacturer’s specifications were followed when installing these gages to ensure that anadequate bond of the gage to the metal was obtained.