Construction monitoring, laboratory testing, and finite element analysis to evaluate reuse potential of structural steel
Date
2019
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Publisher
University of Delaware
Abstract
Iron and steel production is responsible for a significant environmental impact, contributing the third highest CO2 emissions in the United States in 2016. To show one option of shifting towards a more sustainable built environment, this research explores the reuse of structural steel. Reuse of structural steel as primary load members in new buildings is presently rare, despite reduction in CO2 emissions and other environmental advantages that could be achieved via this practice. The main concern preventing this is the lack of information about the stress history of a steel member during the member’s service life. These concerns are most significant during construction, when fit-up issues, temporary loadings, and variable support conditions throughout the construction process may cause force effects to differ from designers’ expectations, and in connection areas where localized stress concentrations occur. ☐ To evaluate if a steel member can be reused after its service life, construction-induced strains in three typical steel-framed buildings were recorded. The field data were recorded using strain gauges connected to a wireless sensor network and a novel carbon nanotube (CNT) based sensor. The analysis revealed high variations in temperature throughout the structures and consequently significant temperature-induced stresses as well as greater magnitudes of flexural stress in columns than expected. The maximum measured stress (160 MPa, 23.2 ksi) was only 46% of the nominal yield strength (of 345 MPa, 50 ksi). ☐ A validated FEM was used to extrapolate field stress data to more locations than feasible to physically instrument. This allowed for prediction and assessment of the maximum stresses in a connection during construction. The FEM was validated using results of a full-scale laboratory test setup. The maximum absolute principal stress in the FEM was 216 MPa (31.4 ksi), 63% of the nominal yield strength. Therefore, collected strain gauge data and extrapolated connection area data indicate no yielding occurred during the construction phase of the instrumented buildings. These field and analytical results indicate that reuse of structural steel members is feasible given that all data collected in this work indicates that the material remains linear elastic during construction, including in connection areas.