Performance-based specifications (PBS) may increase concrete quality and sustainability by facilitating innovations in material selection and proportioning. This is particularly relevant now with increased interest in a broader set of minimally processed minerals for use as supplementary cementitious materials (SCMs) or fillers; these are often industrial and agricultural byproducts and with limited performance history in concrete. This study compares traditional largely prescriptive concrete design, following practices currently allowed by the Georgia Department of Transportation, with three new concrete designs which do not comply with current specifications but offer increased sustainability. Three metrics are assessed for each mixture: the associated cradle-to-gate CO₂ emissions, a metric that incorporates the environmental burden of concrete, compressive strength at 28 days, and surface resistivity measurements taken weekly from 28 to 56 days. A framework is proposed to statistically analyze compressive strength data to pre-qualify mix designs, which can be broadly applied to reduce time-consuming iterative testing and to help meet sustainable development goals. The aim is to foster innovation in material use and mixture design towards an increased durability and performance, while reducing environmental impact and minimizing risk.

Fibre reinforced concrete (FRC) is becoming widely utilized in segmental linings due to the improved mechanical performance, robustness and durability of the segments. Further, significant cost savings can be achieved in segment production and by reduced repair rates during temporary loading conditions. The replacement of traditional rebar cages with fibres further allows changing a crack control governed design to a purely structural design with more freedom in detailing. Macro synthetic fibres (MSF) are non-corrosive and thus ideal for segmental linings in critical environments. Although fibre reinforcement for segments is relatively new, recent publications such as the ITAtech “Guidance for precast FRC segments – Volume 1: Design aspects” or the British PAS 8810 “Tunnel design – Design of concrete segmental tunnel linings – Code of practice” have now given more credibility to this reinforcement type and the basis for design. This paper presents and discusses the design methodology for precast tunnel segments and in particular the tasks associated with the use of MSF reinforcement. Temporary loadings as well as long term load behaviour will be addressed. A case history from the Santoña–Laredo General Interceptor Collector, currently under construction in northern Spain, will illustrate the specific benefits of MSF reinforcement for segmental linings.

With over 80 years of history, it is only in the last 20 years that the use of fiber reinforced polymer (FRP) materials has become feasible for bridge applications in part due to the ever increasing requirement to make structures last longer, with the current American Association of State Highway Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications requiring that structures be designed for a 75 year design life; but also in the development of cost effective production techniques, and the introduction of FRP materials, which bring the cost and strength of FRP materials closer to traditional steel reinforcement. Published documents provide comprehensive recommendations on design methodology, predictive equations, and recommendations for strength and service limits states. In this paper, the background of FRP-prestressed concrete bridges is discussed and trial bridges are designed. Research needs to advance the state of the art are identified and delineated.

The distribution of forces through floor diaphragms is critical to the overall behavior and performance of buildings during both wind and seismic events. Simplified methods commonly employed by design engineers establish approximate magnitudes and distributions of inertial and transfer forces within floor diaphragms. Such methods can be appropriate for regular low-rise buildings without significant transfer forces. However, for design of complex structures with large stiffness discontinuities in vertical or horizontal directions, a more detailed investigation and modeling of diaphragm behavior is usually required. Common situations in high-rise projects include a tower stack meeting a podium base with supplemental shear walls and a tower stack meeting a grade-level slab enclosed by basement walls. Large diaphragm transfer forces typically occur at these levels of abrupt stiffness changes. Using examples from recent projects and parametric studies following performance-based seismic design (PBSD) principles, this paper describes the use of strut-and-tie models in commercially available software (PERFORM-3D) to provide a better understanding of complex diaphragm behavior. Results can aid the designer in making decisions regarding floor thickness and reinforcing layout, including at chords and collectors. While the need for enhanced modeling techniques and understanding of diaphragm behavior has been highlighted by the increased use of PBSD, the findings presented in this paper may be applicable to projects based on traditional (code-based) approaches as well.

The new Terminal 2 at the Tocumen International Airport in Panama, currently essentially completed, will increase the airport’s capacity to 25 million passengers per year. It has a doubly curved steel roof supported on reinforced concrete columns. The gravity force-resisting systems in the superstructure include long span precast and prestressed double tee decks, topped with cast-in-place concrete diaphragms and supported on a combination of unbonded post-tensioned girders and special reinforced concrete moment frame beams. The seismic force-resisting system includes special reinforced concrete moment frames and perimeter columns, special reinforced concrete shear walls and diaphragms, all detailed in accordance with ACI 318. Located in a region of moderately high seismic hazard, the building is classified as an essential facility and requires a non-conventional seismic design approach to maintain operational continuity and to protect life. Adopting the performance-based seismic design methodology and the capacity design principle, the structural engineering team designed an innovative reinforcement detail for developing ductile hinges at the top of the reinforced concrete columns to protect the structural steel roof which is designed to remain essentially elastic under MCE shaking. The structural engineering team’s design has been reviewed by internationally recognized experts and three independent peer review teams.