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

86wrought iron bars were investigated, because this material was commonly used for bridgeconstruction.The tensile strengths from the testing and historical data can be seen in the plot inFigure 4.12. In the plot, the results from the tensile testing conducted for this study fallbelow the mean found for the historical data and mostly are near the lower standarddeviation of this data. All of the testing results except for one, were above the secondstandard deviation from the mean of the historical data. For a set of data, sixty-eightpercent of the data falls within one standard deviation of the mean and ninety-five percentfalls within the second standard deviation. This second standard deviation of 40,000 psicould be used as a conservative estimate of the tensile strength of historic wrought iron.The percent elongation values collected from historic data were also compared tothe percent elongation values found in this study. Figure 4.13 is a plot of these two datasets. In this plot, the data collected from the round test specimens taken from the AdamsMill Bridge were plotted separate from the rectangular eyebar test specimens taken fromthe Bell Ford Bridge. The percent elongations from the round specimens were generallygreater than the average percent elongation of the historical data. All of the percentelongations of the round samples, except one, were greater than one standard deviationless than then mean of the percent elongations for the historical data.The percent elongation results for the rectangular specimens were considerablylower than for the round specimens. Most of the rectangular specimen percent elongationresults were less than one standard deviation lower than the mean of the historical data,and a few were less than the second standard deviation. As previously mentioned, it isbelieved that these low percent elongations are the result of damage that these specimensendured during the collapse of the Bell Ford Bridge. Since many bridge members enduredamage and are repaired and reused, the second standard deviation could be used as apossible minimum value of percent elongation for historic wrought iron.