Quantifying Material Uncertainty in Seismic Evaluations of Reinforced Concrete Bridge Column Structures.

In seismic performance evaluations, the force-deformation response of a structure is typically assessed using a deterministic analytical model, and inherent uncertainty is often neglected. For reinforced concrete structures, a source of uncertainty is variability in the mechanical properties of reinforcing steel and concrete (that is, material uncertainty). This paper presents an analytical investigation to quantify the impact of the statistical variability in mechanical properties of ASTM A706 Grade 60, 80, and 100 reinforcing steel and normalweight concrete on the seismic response of reinforced concrete bridge columns. The effects on the drift response, expressed by the coefficient of variation (COV), range between COV values of 0.1 for low-to-moderate ductility demands (that is, drift ratio < 5%), and 0.3 for larger ductility demands. The COV of the force demand is lower, ranging between 0.05 and 0.1. Overall, the study shows that material uncertainty can be incorporated in seismic performance assessments through a few additional analyses.

Social and Economic Components of Resilient Multi-Hazard Building Design.

In 2017, U.S. damages from natural hazard events exceeded $300B, suggesting that current targets for building performance do not sufficiently mitigate loss. The significant costs borne by individuals, insurers, and government do not include impacts from social disruption, displacement, and subsequent economic and livelihood effects. In 2016, Congress mandated the National Institute of Standards and Technology (NIST) develop a report (NIST SP 1224) describing the research needs, implementation activities, and engineering principles necessary to improve the performance of residential and commercial buildings subjected to natural hazards. An Immediate Occupancy Performance Objective (IOPO) could help preserve building and social functions post event, minimizing physical, social, and economic disaster. The stakeholder-informed NIST report sets forth items needed for multi-hazard building design that can support enhanced resilience decision-making. This paper highlights the social and economic considerations that require additional research, particularly with regard to feasibility and potential impacts from an IOPO. These topics must be considered prior to and throughout the IOPO technical development and community implementation processes to ensure better outcomes after natural hazard events.