Reduced order modelling of hysteretic structural response in seismic risk assessment

Modern seismic risk/loss estimation practices require simulation of structural behavior for different levels of earthquake shaking through time-history analysis. This behavior can be strongly inelastic/hysteretic and evaluating it through high-fidelity finite element models introduces a significant computational burden. A reduced order modeling approach is discussed here to alleviate this burden. The reduced order model is developed using data from the original high-fidelity finite element model (FEM). Static condensation is first used to obtain the stiffness matrix and linear equations of motion for the dynamic degrees of freedom. The restoring forces prescribed by the linear stiffness matrix are then substituted with hysteretic ones, calibrated by comparing the reduced order model time-history to the time-history of the initial FEM for a range of different excitations. This is posed as a least squares optimization problem and its efficient solution is facilitated through a sequential approach. The accuracy and the computational savings of the reduced order model are then examined for seismic risk assessment applications by comparing to the FEM predictions. A stochastic ground motion model is used to describe the seismic hazard and the accuracy for different levels of intensity is separately examined.Authors would like to thank Dr. Papakonstantinou for prodiving the codes for generation of synthetic acceleration time-histories using the (Vlachos, et al. 2018) model

A New Normative Workflow for Integrated Life-Cycle Assessment

In order to curtail energy use by the building sector, consideration of how a sustainable building is constructed is paramount, in many respects, to how efficiently it operates over its lifetime. A typical building must be in use for decades before the energy expended in its daily operations surpasses the energy embodied within its initial construction, as a result of the materials used. More vitally: every building has specific vulnerabilities, particularly to hazards (e.g., earthquakes, wind, flooding) whose effects on sustainability are not explicitly considered alongside other aspects of sustainability in the design process – despite the significant environmental impact of damage and repairs after a disaster. Unfortunately, the joint consideration of resilience and sustainability in design is far from trivial, requiring various interdisciplinary perspectives involved in the delivery of building projects. These perspectives each contribute the models and data necessary for integrated evaluation, leading to the notorious challenges of BIM and data interoperability. In response, this paper presents a new end-to-end workflow for life-cycle assessment (LCA) of buildings that captures the dependencies between multi-hazard resilience and sustainability, across multiple dimensions of environmental impact. An illustrative example reveals how consideration of hazards during design and material selection influence embodied energy, ultimately revealing design choices that best achieve joint resiliency and sustainability

Integrated workflow for evaluating sustainability and resiliency of building systems

This study describes the development of a workflow for integrated life-cycle assessment (iLCA) of buildings that is capable of capturing the dependencies between multi-hazard resilience and sustainability using tools native to professional practice. Modules dedicated to hazard characterization, structural response, damage, repair/loss, and environmental impact (embodied and operating energy) are developed using Application Programming Interfaces (APIs) and semantic data perspectives from computer science. A unifying probabilistic framework is utilized to quantify life-cycle performance and a common, versatile, simulation-based approach is adopted for estimation of performance. This approach supports various resilience/sustainability metrics, including monetary losses, downtime, total embodied energy (initial construction and repairs), and operating energy. A case study executed in the Revit environment evaluates the performance of a special reinforced concrete frame located near Los Angeles International Airport (LAX). Two design alternatives are considered to illustrate the impact of design and material decisions, ultimately revealing design choices which best achieve joint resiliency and sustainability.The authors gratefully acknowledge the support of NSF (CMMI-1537652). The first author also recognizes the support of her NSF Graduate Research Fellowship (DGE-1313583) and Deans Fellowship from the University of Notre Dame. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF