Dr. Alex Sixie Cao (currently Postdoc at Empa and ETH Zurich) will join as an Assistant Professor in the School of Civil and Environmental Engineering, Nanyang Technological University (NTU), Singapore - from July 2026. We are currently recruiting multiple PhD students & Postdocs. NTU CEE ↗
Reliability and robustness
From components to systems: reliability and robustness across spatial scales.
We study how local damage, degradation, and rare events affect the performance of structural and infrastructure systems. Our focus is on quantifying reliability and robustness across materials, components, compartments, structures, and networks, and on understanding how system properties such as redundancy and segmentation prevent or limit progressive collapse.
Key questions
- How do local failures and damage scenarios propagate to system-level response and collapse?
- How can we quantify reliability and robustness in a way that is consistent across spatial and temporal scales?
- How much redundancy, segmentation, and ductility are needed to limit disproportionate consequences?
- How should system-level insights inform target reliabilities, design formats, and code provisions?
Research themes
From local damage to global response
We analyse how the loss and degradation of individual or multiple components, connections, or compartments affect the overall system behaviour. This includes studying progressive collapse and initial damage scenarios in structural and infrastructure systems.
Probabilistic system modelling
We develop probabilistic models of systems that move beyond individual components to capture interactions across spatial scales. This is based on a hierarchical abstraction of structural and infrastructure systems that reflect damage propagation and damage scenarios.
Robustness
We quantify robustness in terms of how a system responds to damage, including low-probability high-consequence events. This involves robustness quantification, developing acceptance criteria and thresholds, and exploring how design choices influence the system performance.
Time-variant reliability
We investigate how time-dependent effects affect the reliability and robustness of systems. This includes studying how degradation phenomena, accidental actions, malicious actions, and normal loading interact and affect the system performance and potential mitigation strategies.
Methods and tools
Our work combines mechanics-based modelling with probabilistic and computational methods:
- Analytical models for impact, dynamic amplification, and collapse mechanisms.
- Nonlinear dynamic simulations of structural systems subjected to damage and extreme loading.
- Hierarchical probabilistic abstractions of structural and infrastructure systems that include both redundancy and segmentation.