Minimizing embodied energy of reinforced concrete floor systems in developing countries through shape optimization.

• Structural efficiency enables affordable construction in developing countries. • Efficient concrete floors and beams reduce tall building costs and embodied energy. • Constrained optimization minimizes concrete and steel and meets structural demands. • Shape optimization accounts for fabrication constraints in affordable construction. Less Economically Developed Countries (LEDCs) are struggling to meet the demand for affordable housing in their growing cities. There are several reasons for this, but a major constraint is the high cost of construction materials. In India, which needs over 20 million urban housing units by 2022, material costs can constitute 60 to 80% of the total cost of residential construction. Nonetheless, their construction mimics the materially inefficient practices of the More Economically Developed Countries (MEDCs), which were developed to reduce labor over material costs. As a result, prismatic beams and flat slabs are often used despite their structural inefficiency. The mounting use of steel-reinforced concrete structures in LEDC cities also raises concern for the environmental costs of construction; for example, construction accounts for 22% of India's carbon emissions. At the building scale, at least 50% of the structural mass and embodied energy is just in the horizontal spanning elements. This research addresses these challenges with a flexible methodology for the design and engineering of materially efficient structural floor systems that can reduce the economic and environmental costs of urban construction. Construction costs and embodied energy are direct products of material choice and quantity. In response, this paper presents a strategy for the numerical shape optimization of ribbed one-way concrete floor slabs. Designed for the constraints of India, the elements are optimized to reduce the embodied energy associated with the slab's concrete and reinforcing steel while resisting the same loads of an equivalent solid flat slab. The optimization method includes a novel approach to 3D shape parameterization, as well as a decoupled analytical engineering analysis method that accounts for the key failure modes and constraints of reinforced concrete design. The result of this work is a shaped slab design method that can reduce the embodied energy of one-way concrete floors by 48–64%. [ABSTRACT FROM AUTHOR]