Performance-Based Seismic Design (PBSD) of reinforced concrete buildings has rapidly become a widely used alternative to the prescriptive requirements of building code requirements for seismic design. The use of PBSD for new construction is expanding, as evidenced by the design guidelines that are available and the stock of building projects completed using this approach. In support of this, the mission of ACI Committee 374, Performance-Based Seismic Design of Concrete Buildings, is to “Develop and report information on performance-based seismic analysis and design of concrete buildings.” During the ACI Concrete Convention, October 15-19, 2017, in Anaheim, CA, Committee 374 sponsored three technical sessions titled “Performance-Based Seismic Design of Concrete Buildings: State of the Practice.” The sessions presented the state of practice for the PBSD of reinforced concrete buildings. These presentations brought together the implementation of PBSD through state-of-the-art project examples, analysis observations, design guidelines, and research that supports PBSD. This special publication reflects the presentations in Anaheim. Consistent with the presentation order at the special sessions in Anaheim, the papers in this special publication are ordered in four broad categories: state-of-the-art project examples (papers 1-5), lateral system demands (papers 6-8), design guidelines (papers 9-10), and research and observed behavior (papers 11-13). On behalf of Committee 374, we wish to thank each of the authors for sharing their experience and expertise with the session attendees and for their contributions to this special publication.

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.

This paper summarizes the benefits and challenges of implementing performance-based seismic design (PBSD) for two concrete buildings of the Lower Sproul Plaza Redevelopment Project in one of the busiest areas of the UC Berkeley campus. The project included new construction of Eshleman Hall and the additions to Martin Luther King (MLK) Hall, and the seismic retrofit of the existing MLK Student Union as a result of the expansion. The peer-reviewed PBSD implemented three-dimensional nonlinear response history analyses at two levels of seismic hazard. The analytical simulations using pairs of near-fault ground motions, scaled to match the site-specific spectrum, were intended to establish the expected seismic behavior of the buildings under rare and frequent earthquakes. The choice of PBSD over code-prescriptive procedures was prompted by multiple layers of complexity of the project. Several challenges including those related to the horizontal and vertical irregularities, or connecting new and existing concrete buildings with different lateral force-resisting systems would have made a code-prescriptive design a cumbersome analytical endeavor without providing reliable insight about the expected seismic behavior of the buildings. The PBSD, however, proved a powerful framework to design for a reliably predictable seismic behavior with sufficient ductility, and a designated ductile hinge zones with sufficient confinement and shear capacity. The PBSD methodology also enabled the designers to avoid unnecessary conservatism to deal with the complexities, when designing drift- and acceleration-sensitive elements including the cladding system. Finally, the PBSD methodology allowed the design to consider all potential modes of failure of concrete elements retrofitted by FRP material including the debonding failure between FRP material and substrate.

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.

Performance based seismic design (PBSD) has created new opportunities for enhanced performance, improved cost efficiencies, and increased reliability of tall buildings. More specifically, flexibility with initial design methods and the utilization of response history results for design, not just verification, have emerged. This paper explores four refined design methods made available by the employment PBSD to influence seismic performance and identify areas of importance. First is the initial proportioning of reinforcement to encourage plastic hinge behavior at specific locations. Second is the initial proportioning of wall thicknesses and reinforcements to encourage a capacity-based design approach for force-controlled actions. Third is the mapping of observed strain demands in shear walls to specific detailing types such as ordinary and special boundary zones. Fourth is an efficient envelope method for the design of foundations. Through these design methods, initial proportioning can be conducted in a more refined way and targeted detailing can result in cost savings. A case study of a recently designed high-rise residential building demonstrates that cost savings can be achieved with these methods.