Thanks for visiting the website for our NEES (Network for Earthquake Engineering Simulation) Project that aims to develop and implement fundamental models for predicting fracture and Ultra-Low Cycle Fatigue in steel structures. Through this website, we will hope to provide updated status on our project, share data and materials, as well receive feedback.

This project began in November 2004, as part of the first round of NEESR awards. It is an individual investigator (II) project, which is the smallest type of NEESR projects. The project is led by Amit Kanvinde, UC Davis, and Greg Deierlein, Stanford, is a co-PI. Two doctoral students at Davis, and one at Stanford are contributing to this effort.

Different sections of this website will be updated frequently as the testing and simulation plan progresses over the coming months and years. Here’s a brief summary of the project.

NEESR-II: Large Scale Tests and Micromechanics-based simulation of Ultra-Low Cycle Fatigue (ULCF) and Fracture in Steel Structures

Cyclic inelastic deformations are the primary mode of seismic energy dissipation in steel structures. During earthquakes, structural elements such as bracing members undergo a phenomena called Ultra-Low Cycle Fatigue (ULCF), which is characterized by very few (<10-20) large strain cycles. ULCF is quite distinct from low cycle fatigue, which has been more widely studied but does not address the conditions prevalent in seismic design. Relatively little attention has been given to characterizing the fundamental failure mechanisms associated with ULCF, due to the lack of suitable micro-scale models to simulate ULCF and the computational requirements necessary implement the models for studying large structural components. Existing research on ULCF of steel structures in earthquakes relies almost exclusively on semi-empirical methods, which cannot be transferred to varied structural configurations. Moreover, most of the existing empirical research is based on quasi-static testing, which does not account for earthquake loading rate effects. Such knowledge gaps represent serious issues for seismic hazard mitigation. The proposed research aims to (1) identify and quantify the underlying failure mechanisms of earthquake-induced ULCF, (2) develop and implement models to simulate ULCF in steel structures (3) conduct large scale subassembly tests at earthquake loading rates to verify and demonstrate the models (4) apply the ULCF models to develop practical guidelines and recommendations for earthquake resistant design. This project is being conducted in collaboration with Stanford University, and large scale testing will be conducted at the NEES facility at Berkeley.