Highway bridge construction production rates for time estimation
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Both the importance and process of estimating project construction time have increased in significance as roadway user costs themselves have become more significant. In estimating project construction times, beyond the process of synthesizing activity durations, few parameters are more significant than work item crew production rates. This research was initiated in order to collect reliable field data of crew production rates and to identify factors driving the rates, which will help TxDOT better estimate construction contract time. A data collection tool was developed incorporating many different factors affecting production rates for consistent data collection. A guideline was also established to ensure the accuracy and efficiency of the data collection process. Five critical work items of highway bridge construction, namely Footing, Column(Rectangle/Round), Cap, Beam Erection, and Bridge Deck, have targeted and efforts have been made to collect field data by means of observation from a large number of Texas ongoing projects. For the five work items, a total of 137 vii data points were acquired on 25 ongoing highway projects between February 2002 and January 2004. Production rates were compared with previously CTDS established rates. Rates of ‘Column-Rectangle’ and ‘Beam Erection’ in CTDS are much lower than the ones collected from this research. However, differences in the scope of each work item used for the production rates computation must be taken into consideration when the results are interpreted. Various hypothesized drivers of the crew production rates have been also analyzed. First, several candidate drivers were identified by visually inspecting on scatter plots as well as correlation coefficients tables. Then, Simple Regression and Analysis of Variance (ANOVA) were employed in order to test statistical significance. It was found that some of the drivers have statistically significant relationships with the production rates.