Concrete Mechanics for Performance Based Design

Example Steel fibres bridging a crack in a 3D periodic lattice
What does 1% of steel fibres actually buy you? Run the same concrete cube twice — same lattice, same random strength field, same crack — once plain and once with fibres. The plain matrix softens toward zero; the fibres crossing the crack hold a bridging plateau. A periodic cell keeps both the crack and the fibre placement free of boundary artefacts.

Example Corrosion-induced cracking — a constrained-expansion problem on a 3D lattice
Most durability problems are a constrained-expansion story: something inside wants to grow, the surrounding material resists, and cracks form. Corrosion of a steel bar inside concrete is one of the most studied cases. A 3D lattice slice reproduces the textbook two-phase failure — axisymmetric multi-crack expansion, then a single crack reaching the surface — and the pressure jump that goes with it.

Example CFRP-confined concrete cylinder — hardening past the unconfined peak
Wrap a plain concrete cylinder in a CFRP jacket and its load–displacement curve no longer softens — it keeps hardening past the unconfined peak. Inside the wrap, though, the concrete is damaging. CDPM2 in OOFEM reproduces both stories from one input change.

Paper 3D frame element for large rotations based on the rigid-body-spring concept for analysing the failure of structures
Gumaa Abdelrhim, Peter Grassl, International Journal of Solids and Structures, vol. 327, pp. 113812, 2026.
DOI (Open access)

Paper RAAC panels can suddenly collapse before any warning of corrosion-induced surface cracking
Evžen Korec, Peter Grassl, Milan Jirásek, Hong S. Wong, Emilio Martínez-Pañeda, npj Materials Degradation, vol. 9, pp. 44, 2025.
DOI (Open access)

The Grassl Group, based at the James Watt School of Engineering at the University of Glasgow, aims to understand, predict and improve the response of concrete and concrete structures. Our work is focused on deterioration processes, development of new materials, optimisation of material use, repair and strengthening techniques, and response of structures subjected to accidental loading. Currently, our methodologies comprise the following areas: Meso/Micro scale modelling, Constitutive modelling and Structural modelling. We contribute to the development of the finite element program OOFEM. You can find all our models implemented in our github fork of OOFEM. Our results are described in our publications.