Browsing by Author "Zaker Esteghamati, Mohsen"

Now showing 1 - 7 of 7
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    Application of surrogate models for performance-based evaluation of multi-story concrete buildings at early design
    Zaker Esteghamati, Mohsen; Flint, Madeleine M.; Rodriguez-Marek, Adrian (2022)
    Data incompleteness and uncertainty impede the application of performance-based design of structures at early design, which relies on data- and time-intensive numerical simulations. Early design is the most influential stage in a buildings' life cycle performance, hence neglecting quantitative methods to evaluate the design in preliminary stages can lead to missing on opportunities to improve building resiliency. This study presents a framework to implement surrogate models for supporting performance-based early design of concrete multi-story buildings. Five different surrogate models including multiple linear regression, random forest, extreme gradient boosting, support vector regression machines, and k-nearest neighbors are developed and compared to represent the seismic-induced structural loss of 720 generic concrete office buildings using early design parameters. Additionally, variance-based sensitivity is used to determine influential parameters for the best-performing model. The results show that extreme gradient boosting and support vector regression machines can be used to relate crude topology and design parameters to building seismic performance with reasonable accuracy.
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    A data-driven framework to support resilient and sustainable early design
    Zaker Esteghamati, Mohsen (Virginia Tech, 2021-08-05)
    Early design is the most critical stage to improve the resiliency and sustainability of buildings. An unaided early design follows the designer's accustomed domain of knowledge and cognitive biases. Given the inherent limitations of human decision-making, such a design process will only explore a small set of alternatives using limited criteria, and most likely, miss high-performing alternatives. Performance-based engineering (PBE) is a probabilistic approach to quantify buildings performance against natural hazards in terms of decision metrics such as repair cost and functionality loss. Therefore, PBE can remarkably improve early design by informing the designer regarding the possible consequences of different decisions. Incorporating PBE in early design is obstructed by several challenges such as time- and effort-intensiveness of performing rigorous PBE assessments, a specific skillset that might not be available, and accrual of aleatoric (associated with innate randomness of physical systems properties and surrounding environment conditions) and epistemic (associated with the incomplete state of knowledge) uncertainties. In addition, a successful early design requires exploring a large number of alternatives, which, when compounded by PBE assessments, will significantly exhaust computational resources and pressure the project timeline. This dissertation proposes a framework to integrate prior knowledge and PBE assessments in early design. The primary workflow in the proposed framework develops a performance inventory to train statistical surrogate models using supervised learning algorithms. This performance inventory comprises PBE assessments consistent with building taxonomy and site, and is supported by a knowledge-based module. The knowledge-based module organizes prior published PBE assessments as a relational database to supplement the performance inventory and aid early design exploration through knowledge-based surrogate models. Lastly, the developed knowledge-based and data-driven surrogate models are implemented in a sequential design exploration scheme to estimate the performance range for a given topology and building system. The proposed framework is then applied for mid-rise concrete office buildings in Charleston, South Carolina, where seismic vulnerability and environmental performance are linked to topology and design parameters.
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    The impact of hazard-consistent ground motion scenarios selection on structural seismic risk estimation
    Zaker Esteghamati, Mohsen; Bahrampouri, Mahdi; Rodriguez-Marek, Adrian (The Geo-Institute of ASCE, 2021)
    Structural risk-based evaluation requires a large number of time-history analyses at different ground motion (GM) intensity levels, where the scenarios (e.g. magnitude and distance) of the GMs used in the time-history analyses should be consistent with the site's hazard. The current practice of GM selection typically simplifies the choice of scenario to either an average scenario or the modal scenarios based on the site's hazard deaggregation results. This paper investigates the impact of hazard deaggregation and scenario selection on estimating structural seismic risk. For a hypothetical site in the Eastern US, a Monte Carlo seismic hazard analysis is performed to derive a site-consistent GM suite that captures 1,000,000 years of the site's seismic activity. The complete GM suite consisting of 99,917 records is then used to perform nonlinear dynamic analyses on a mid-rise concrete office building to derive a benchmark seismic demand curve. Subsequently, four GM sets are selected based on average and modal scenarios from two different hazard deaggregation formulation, and the resulting demand curves are compared to the benchmark. The results show that the hazard deaggregation method and scenario choice impacts the demand curve estimation. When deaggregation is performed on IM exceedance, GMs that were selected based on both methods agree well with the benchmark up to higher damage states where mode-based records outperform average-based records. On the other hand, when deaggregation is formulated based on IM occurrence, average scenario-based GMs better match the benchmark, except for higher damage states where again modal scenario-based GMs are in better agreement with the benchmark.
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    Inventory of Seismic Structural Evaluations, Performance Functions and Taxonomies for Buildings (INSSEPT)
    Zaker Esteghamati, Mohsen; Lee, Jeonghyun; Musetich, Matthew; Flint, Madeleine M.; Sharifi Mood, Mahyar (DesignSafe-CI, 2019-11-25)
    Relational database of published performance-based earthquake engineering and probabilistic seismic demand analysis results for mid-rise buildings. The database schema is organized based on building taxonomy information and prioritizes structural engineering use cases including comparison of alternative structural systems in early building design and regional seismic portfolio risk analysis. Data provenance, use cases, and sample queries are available in the accompanying manual, as well as two interactive Jupyter notebooks. A full description of the data provenance and schema design is provided in a related manuscript: Zaker Esteghamati, M., Lee J., Musetich M., Flint M. M., `INSSEPT: An open-source relational database of seismic performance estimation to aid with early design of buildings.'
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    Life Cycle Assessment Data & Energy Models of Archetype Commercial Buildings Located in the Central and Eastern United States
    Zaker Esteghamati, Mohsen; Sharifnia, Houri; Ton, Diep; Asiatco, Patricia; Reichard, Georg; Flint, Madeleine M. (Virginia Tech, 2021-10)
    This repository contains life cycle assessment data and energy models of six professionally-designed alternatives for a hypothetical 4-story office building in Charleston, South Carolina, USA. The VT-RSB archetypes have identical external and similar internal layouts to support well-controlled comparative assessment of soil-foundation-structure-envelope (SFSE) systems. The six archetype buildings include concrete (frame, wall), steel (frame, braced), masonry, and wood designs. This repository is provided to serve as a possible benchmark environmental data for commercial buildings located in the Central and Eastern United States.
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    Probabilistic seismic assessment of a mid-rise eccentrically braced steel frame equipped with butterfly-shaped dampers
    Zaker Esteghamati, Mohsen; Farzampour, Alireza (2020-09)
    While modern code-conforming steel buildings can withstand seismic events without collapse through substantial inelastic action, the damages to structural members limit the building’s post-earthquake functionality and safety. An efficient approach to minimize structural damage is to implement elements with large ductility and energy dissipation capability as shear fuses. Shear fuses are designed to protect the surrounding members from damages by yielding and are then easily replaced after the event imposing significant lateral forces. The butterfly-shaped dampers are a novel type of structural fuse with varying width that has been shown to improve structural energy dissipation and eliminate the high strain concentration in critical areas. However, a detailed risk-based assessment is needed to investigate their implementation and effectiveness in seismic retrofitting of mid-rise buildings. In this study, the seismic performance of a six-story steel braced frame with supplemental butterfly-shaped dampers is investigated and compared with a conventional eccentrically-braced system using a probabilistic approach. Nonlinear finite element models are constructed using OpenSees simulation framework. Incremental dynamic analysis is then performed to derive seismic fragility and demand hazard curves in terms of the structure’s global responses. The results show that butterfly-shaped dampers tangibly improve the structural seismic performance of the braced frame system compared to conventional systems at all considered performance levels. In addition, the improvement is more pronounced at larger drift demand levels associated with higher damage states. In particular, butterfly-shaped dampers reduces the mean annual frequency of exceeding the complete damage of the original building by a factor of 4 for the studied building.
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    The role of early design decisions on sustainability of mid-rise office buildings from a comparative LCA perspective
    Zaker Esteghamati, Mohsen; Asiatco, Patricia; Diep Ton, Thea; Zhukuva, Natalia; Flint, Madeleine M. (2019)
    This study compares the environmental impacts of four professionally-designed archetypes building with different combinations of foundation, structure, and envelopes (FSE) assemblies. In addition, detailed operational energy modeling using the EnergyPlus framework is performed. The result shows that early decisions regarding structural and foundation systems significantly affect the production and construction phases, whereas the choice of envelope system is the primary driver of the operational phase. furthermore, the operational phase dominates the life-cycle of the archetypes and therefore, early decisions associated with the operational phase, such as envelope system and expected service life, should be prioritized.