CO2-optimization of reinforced concrete frames by simulated annealing

This paper describes a methodology to design reinforced concrete (RC) building frames based on minimum embedded CO2 emissions. The design involves optimization by a simulated annealing (SA) algorithm applied to two objective functions, namely the embedded CO2 emissions and the economic cost of RC framed structures. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to six typical building frames with 2, 3 and 4 bays and up to 8 floors. The largest example has 153 design variables and a combinatorial solution space of 10232. Results from the SA algorithm application indicate that embedded emissions and cost are closely related and that more environmentally-friendly solutions than the lowest cost solution are available at a cost increment which is quite acceptable in practice. Further, the best solutions for the environment are only at the most 2.77% more expensive than the best cost solutions. Alternatively, the best cost solutions increase CO2 emissions by 3.8%. Finally, the methodology described will enable structural engineers to mitigate CO2 emissions in their RC structural designs.