MINT: Masonry in-situ testing and material identification

The UK has one of the oldest building stocks in Europe. In England, around a quarter of this stock is of solid brickwork construction. Every year, thousands of such buildings experience structural distress due to seasonal and excavation-induced ground movements. To understand and manage the impact of ground movements on these historic assets, an in-depth knowledge of their materials is necessary. Therefore, the primary motivation for MINT is to estimate mechanical properties of existing masonry assets and the opportunity to challenge the limited availability of data on material properties with new in-situ tests, using improved measurement and interpretation techniques.

Standard techniques for characterising the mechanical properties of brick masonry materials require extensive sampling and destructive testing. As a result, these techniques are rarely applied to existing buildings. In-situ testing and characterisation of materials is a promising alternative. However, in their current form, standard in-situ tests provide limited information on material properties. The MINT project aims to develop a minor-destructive in-situ testing method to identify the key macro-scale deformability and strength parameters of historic brick masonry materials. This method will combine unconventional flat jack testing with unambiguous Digital Image Correlation (DIC) strain measurements and rapid Virtual Fields Method (VFM) algorithms to overcome the limitations of standard material characterisation techniques. It will deliver a step change in our ability to collect detailed mechanical information on brick masonry materials and unlock the potential of numerical simulations to reliably assess structural response. It is envisioned that this new capability will also enable more informed decisions on retrofit and repair. In the longer term, the developments from MINT will contribute to improve productivity in the construction sector, and the welfare of the general public.

The objectives of the MINT project are listed below:
1. Numerically explore different flat jack and slot arrangements to determine suitable testing procedures for a range of brick masonry walls (Work Package WP1).
2. Understand how DIC parameters impact strain measurements in masonry and develop suitable measurement procedures for in-situ tests (WP2).
3. Develop the theory to identify masonry macro-scale deformability and strength parameters in-situ based on DIC data and VFM algorithms (WP3).
4. Quantify the influence of in-situ test uncertainties (e.g. jack loading distribution), measurement noise and modelling bias on material identification (WP3).
5. Construct brick masonry walls in the laboratory from well-characterised materials. Apply in- situ material identification techniques to these walls and evaluate the consistency of identified parameters with the expected values (WP4-5)
6. Conduct further loading experiments on walls and evaluate the ability of numerical models with the identified parameter properties to blindly predict the response (WP5).

This project falls within the EPSRC Structural Engineering research area. Project partners include the materials testing and technology company MatchID, company DIANA FEA which have developed state of the art masonry constitutive models in commercial FE software, leading consultants Buro Happold as well as the material development and testing company Lucideon.