[Paper Review] Energy-based seismic design: Needs of energy damage index values for serviceability and ultimate limit states for gravity design buildings?

Caterina Negulescu, K. K. Wijesundara|arXiv (Cornell University)|Apr 24, 2019

Structural Health Monitoring Techniques4 citations

TL;DR

This study proposes an energy-based damage assessment framework for gravity-designed buildings, using wavelet-based energy estimation to evaluate seismic demand and capacity without relying on hysteretic models. It finds that energy-based damage indices correlate well with inelastic period and drift, with inelastic cycle count significantly affecting medium/high-ductile structures but not low-ductile ones.

ABSTRACT

During the past earthquakes, different low ductile failure modes are observed in the gravity design structures and thus, the most of existing damage indices may fail to assess the damage of gravity design structures accurately in referring to the two main performance levels: immediate occupancy and ultimate limit state. Therefore, this study investigates the energy dissipated by the brittle structures and the possible damage indices based on energy for the damage assessment of gravity design frames. In the framework of an Energy-Based Seismic Design Approach, we need the assessment of the Demand and on the Capacity, both expressed in Energy. A methodology for the assessment of the seismic energy demands imposed on structures is already proposed, but not such methodology that makes consensus is proposed for the calculation of the Energy dissipation Capacity avoiding the Hysteretic models. The estimation of the energy expended by the building during an earthquake excitation is a tricky issue. For this purpose, this study considers the wavelet based energy estimation and compares it with different approaches for measuring the damages of a structure: the dominant inelastic period of a building and the more classical measure, the inter-story drift. IDA analysis are performed in energy, drift and inelastic period. Furthermore, the damage assessment results based on the expended energy for three gravity design buildings are compared and discussed relatively to the results expressed in inelastic period and drift. Finally, this study concludes that no significant effects of number of inelastic cycles to the damage assessment results for low ductile structures. However, this study also highlights the effects of number of inelastic cycles to the damage for medium and high ductile structures.

Motivation & Objective

• Address the inadequacy of existing damage indices in assessing seismic performance of low-ductile gravity-designed buildings.
• Investigate the applicability of energy-based damage indices for serviceability (immediate occupancy) and ultimate limit states.
• Develop a methodology for estimating seismic energy demand and dissipation capacity without relying on hysteretic models.
• Compare energy-based damage assessment with conventional metrics: inelastic period and inter-story drift.
• Assess the influence of inelastic cycle count on damage evaluation for structures of varying ductility.

Proposed method

• Employ wavelet-based energy estimation to compute energy dissipation during seismic excitation.
• Perform Incremental Dynamic Analysis (IDA) in three domains: energy, inter-story drift, and inelastic period.
• Use energy-based damage indices derived from the ratio of dissipated energy to capacity.
• Compare damage states across three gravity-designed buildings using energy, drift, and inelastic period metrics.
• Avoid reliance on hysteretic models by directly estimating energy from structural response time histories.
• Validate results through comparative assessment of damage levels across performance levels.

Experimental results

Research questions

• RQ1 Can energy-based damage indices accurately assess damage in low-ductile gravity-designed buildings for immediate occupancy and ultimate limit states?
• RQ2 How does wavelet-based energy estimation compare to traditional metrics like inter-story drift and inelastic period in damage assessment?
• RQ3 What is the influence of the number of inelastic cycles on damage evaluation for low-ductile versus medium/high-ductile structures?
• RQ4 To what extent can energy dissipation capacity be estimated without using hysteretic models?
• RQ5 How consistent are damage assessments when using energy, drift, and inelastic period as metrics?

Key findings

• Energy-based damage indices show strong correlation with damage states assessed via inter-story drift and inelastic period.
• The number of inelastic cycles has no significant effect on damage assessment results for low-ductile structures.
• For medium and high-ductile structures, the number of inelastic cycles significantly influences damage assessment outcomes.
• Wavelet-based energy estimation provides a viable alternative to hysteretic models for energy capacity assessment.
• Energy-based methods effectively capture damage progression across performance levels without requiring complex material models.
• IDA results in energy, drift, and inelastic period domains yield consistent damage state classifications for the studied gravity-designed frames.