Optimising the geometry of 3D printed steel structures against local and global instability.

The overarching goal of the research is to study how the buckling strength of steel sections can be improved by changing the form of their surfaces to resemble buckling modes of equivalent prismatic columns. Previous research on this matter has already been carried out by the author, with numerical tests done on modified RHS stub columns under pure compression (Chater & Wang, 2019), and lab tests carried out on EAS sections. This PhD seeks to expand on that work as follows:
1) Testing under a wide variety of loading conditions to achieve TRL 4. This would take the form of several simulations of the technology used within situations comparable to actual conditions found in existing structures. This would probably consist of 4 parts:
Testing of identical stub columns under bending, shear, axial and combined loads. Further research needs to be done to identify best practices for these varied loads in order to best capture the behaviour of the stubs; this would be a part of the literature review.
Tests of a longer length of column (and/or beam) under a variety of loading conditions to establish the relationship between known local failure mechanisms and global failures. Again, exactly what this constitutes will be dependent on a review of existing literature.
Tests of these sections within larger structural systems taken directly from existing building designs. Collaboration may be undertaken with external consultants to identify suitable systems in which to test this.
Fatigue tests and lifecycle analysis, to ensure no unexpected long-term issues from use of these parts.
2) Testing of modified versions of the same columns, which fully utilise the capabilities of additive manufacturing to vary the thickness of material throughout the section. Optimisation of these sections will likely be driven by an artificial neural network (ANN), as these are widely used in optimisation for non-linear behaviours in the present day. The goal of this section would be to find the greatest buckling capacity achievable by a single, fully connected continuous element with a given amount of material.
3) Testing of sections cold-pressed into the previously defined topology after being rolled traditionally. The aim of this is to make the technology more accessible, extending it to a greater audience by separating it from the limits on production rate, cost and environmental impacts associated with additive manufacturing.
In all of these cases, testing will be carried out both via numerical analysis in ABAQUS, with lab tests following after wherever possible to ensure the validity of these tests. Prior to all of the above would be an extensive literature review, aiming to find best practices and precedents for how best to approach the outlined research goals.