Date of Award

12-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Civil Engineering

Advisor

Ross, Brandon

Committee Member

Klotz , Leidy

Committee Member

Pang , Weichiang

Abstract

Concrete has a large environmental footprint so it is desirable to find ways to efficiently design structural members. Engineers can exercise their abilities early on in the design phase of construction projects to reduce the environmental footprint by minimizing the amount of materials required. One way to achieve these results is to optimize the design of structural concrete. In this study, simple-span rectangular reinforced concrete (RC) beams with a range of different bending moments were analyzed. The primary goal was to combine life cycle analysis (LCA), numerical optimization, and reinforced concrete mechanics to create a framework for designing efficient RC beams. In particular, the method was developed to quantitatively compare the environmental preferability of RC materials with different properties, such as high-strength reinforcement, high-strength concrete, and lightweight (LW) concrete. The method utilizes ratios of unit cost and/or unit embodied energy. This approach makes the method more general, and facilitates application of the method to a wide variety of circumstances. In addition to guiding material selection, the method also provides designers a means for quickly selecting near optimum cross-section properties. Trade-offs between optimum economic cost and optimum environmental footprint were also evaluated through multiobjective optimization. The results showed that cost-optimized beams have up to 10% more embodied energy than do energy-optimized beams but are up to 5% cheaper than energy-optimized beams. The products of this thesis will be useful in rationally selecting materials and designing efficient beams in terms of cost and energy.

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