Special Issue on Sustainable Building Structures

This month’s Journal of Structural Engineering contains a collection of 10 papers focused on sustainable building structures. Topics covered include energy-efficient wood and bamboo structures, sustainable design of reinforced concrete (RC) through ${\mathrm{CO}}_2$ emission optimization, replacement of portland cement with industrial byproducts, and replacement of natural aggregates in concrete with recycled materials. A series of papers investigate the sustainable use of concrete in structural systems. While concrete is one of the most versatile building materials and has enabled industrial growth, it is also one of the biggest in terms of environmental impact. In a paper entitled “Sustainable design of reinforced concrete structures through ${\mathrm{CO}}_2$ emission optimization,” Yeo and Potra present an optimization approach to balance economic objectives with sustainability objectives that consider the energy embodied within a structure. The approach is illustrated using a RC frame under gravity and lateral loads, showing that the ${\mathrm{CO}}_2$ footprint of the structure may be lower if the objective function used in the design optimization is the carbon footprint rather than the cost.

Concrete structures with increased sustainability can be achieved by partial or full replacement of portland cement with industrial byproducts (e.g., fly ash, ground granulated blast furnace slag, and silica fume) as well as the replacement of natural aggregates (e.g., gravel and crushed stone) with recycled materials (e.g., recycled glass and concrete). In a paper entitled “Shear behavior of high-volume fly ash concrete versus conventional concrete–Experimental study,” Arezoumandi, Volz, Ortega, and Myers investigate the shear strength of full-scale beams constructed using high-volume fly ash concrete. While the use of fly ash in concrete construction is common, the current state-of-the-practice is limited to low replacement ratios of the portland cement. Arezoumandi, Volz, Ortega, and Myers show that beams with up to 70% of portland cement replaced using a Class A fly ash can develop comparable shear strengths as conventional RC beams. In a related contribution, Roskos, White, and Berry experimentally investigate the “Structural performance of self-cementitious fly ash concretes with glass aggregates.” This paper reports on reinforced concrete beams with self-cementitious fly ash as the sole binder and reused glass as the aggregate. For tension-controlled failure, fly ash/glass concrete beams perform similarly to conventional reinforced concrete beams. However, conventional concrete outperforms fly ash/glass concrete for compression-controlled and shear-controlled beams, which may be attributed to the reduced strength and reduced aggregate interlock of fly ash/glass concrete.

In the years to come, the renovation and replacement of the nation’s aging infrastructure will not only increase the demand for new concrete but also the supply of demolished concrete. Thus, it may be possible to further improve the sustainability of RC structures by recycling old concrete as partial or full replacement to natural coarse aggregates in new construction. An investigation into the “Behavior of reinforced concrete beams with recycled concrete coarse aggregates” is presented by Knaack and Kurama, specifically focusing on beams made using locally available, prequalified recycled concrete aggregates with minimal processing and constructed in a manner that is consistent with current U.S. practice for conventional concrete. It is found that the full replacement of natural coarse aggregates with recycled concrete aggregates does not cause an observable change in the progression of damage or ultimate failure in flexure-critical and shear-critical beams. However, there is a considerable reduction in the initial stiffness of the beams, indicating that immediate and long-term deflections under service-level loads may be a bigger limitation than strength. Development of reliable bond between the reinforcing steel and concrete is another essential requirement for the use of supplementary materials in structural RC applications. In an experimental study, Butler, West, and Tighe examine the “Bond of reinforcement in concrete incorporating recycled concrete aggregates.” In these tests, 48 beam-end specimens incorporating several bonded lengths show that the use of recycled concrete aggregates can result in a significant reduction of the bond strength of reinforcement, and that there may be a strong correlation between the bond strength and the crushing strength of the coarse aggregate. These results demonstrate the need for future research and potential code changes for the use of recycled materials in RC structures.

The use of supplementary materials in concrete compression members, such as columns, may also create critical conditions because of the greater reliance on the concrete performance. This is investigated by Niang, Roy, and Tagnit-Hamou in a paper entitled “Structural behavior of concrete incorporating glass powder used in reinforced concrete columns.” Concrete made with glass powder has a very low permeability to chloride ions, which is beneficial for use in corroding conditions, such as the presence of deicing products or a salty environment. Through axial load testing of RC columns, Niang, Roy, and Tagnit-Hamou show that columns with 20% glass powder as cement replacement have similar structural behavior (e.g., concrete spalling and peak load) as columns made with conventional concrete. As investigated in “Circular concrete filled tubes for improved sustainability and seismic resilience,” concrete-filled tubes (CFTs) provide another opportunity for the sustainable use of concrete structures with large amounts of supplementary materials to replace portland cement or natural aggregates in compression members. In this paper, Lehman, Kuder, Gunnarrson, Roeder, and Berman study the effects of high volumes of fly ash and slag in circular concrete-filled tubes under conditions ranging from the early age response of the concrete, to sustained (long term) creep and shrinkage effects, and extreme loading from earthquakes.

The current issue of the Journal also includes three papers on energy-efficient wood and bamboo structures. In their contribution, Korde, West, Gupta, and Sudhakar investigate “Laterally restrained bamboo concrete composite arch under uniformly distributed loading.” Compared with timber, bamboo requires only a few years of growth to achieve strength suitable for load-bearing applications. Experimental results combined with analytical simulations show the potential for the use of bamboo-concrete composite arches as a sustainable and renewable structural member. An investigation on the “Seismic laboratory testing of energy-efficient, staggered-stud, wood-framed shear walls” is discussed by Rodriguez-Nikl, Gupta, Kramer, and Sinha. This paper focuses on reducing residential energy use in wood-framed houses by reducing thermal bridging through a staggered stud shear wall system. Monotonic and cyclic lateral load tests show that the staggered stud wall system can perform similarly to conventional walls, thus supporting their use as an energy efficient option in areas of seismic hazard. In a related study entitled “Lateral loading behaviors of lightweight woodframe shear walls with ply-bamboo sheathing panels,” Xiao, Li, and Wang present monotonic and cyclic lateral load test results of environment-friendly lightweight wood frame shear walls with ply-bamboo sheathing panels. The results show that ply-bamboo sheathing panels can satisfy the structural load-bearing requirements for shear walls in seismic regions.

Overall, these 10 papers demonstrate some of the recent advances, challenges, and opportunities related to the design, analysis, and construction of sustainable buildings. As infrastructure ages and the population grows, engineers have no other choice but deliver more efficient and durable structures including renewable materials as well as recycled resource utilization to minimize environmental impact.