Achieving Sustainable Structural Steel Design by Estimating Fabrication Labor Cost Based on BIM Data

Abstract

Structural steel is heavily utilized in the construction industry from residential and commercial buildings to oil and gas projects. For steel fabrication companies as suppliers of steel structures, submitting competitive project bids requires substantial knowledge of the company's practices on the shop floor and extensive experience to interpret that into credible cost estimations. Being able to make reliable estimates would contribute to the company's competitiveness in the long run. In this study, the total quantity of worker-hours or man-hours required for each major subdivision of a project is considered as the variable of interest in estimating a steel fabrication project, mainly because of the labor-intensive nature of steel fabrication. In collaboration with a partner company, three years of project data, were collected by matching the company's building information modeling (BIM) system with their labor costing system resulting in over 3,000 records, each representing the quantity takeoff for 46 design features and the worker-hours expended in shop fabrication. Stepwise regression and error analysis are used to recognize the most crucial design features in estimating project worker-hours, allowing discovery of the minimized set of inputs for estimating worker-hours and characterization of the estimation uncertainties. This labor cost estimation benefits estimators and shop production planners in that they can configure labor resources to deploy, schedule shop floor production, and recognize estimates’ associated errors, based on the company's historical data. This study is an example of using BIM data and providing tools for structural engineers to consider steel fabrication and possibly achieve more sustainable designs.