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

该研究的总体目标是研究如何通过改变其表面的形式来提高钢截面的屈曲强度，使其类似于等效柱的屈曲模式。作者之前已经对这一问题进行了研究，在纯压缩下对改进的RHS短柱进行了数值试验（Chater & Wang, 2019），并在EAS截面上进行了实验室试验。本博士旨在扩展该工作如下：1)在各种负载条件下进行测试，以达到TRL 4。这将采取在与现有结构的实际条件相当的情况下对所使用的技术进行若干次模拟的形式。这可能包括4部分：同一短柱在弯曲、剪切、轴向和组合荷载下的测试。需要做进一步的研究，以确定这些不同负载的最佳做法，以便最好地捕捉存根的行为；这是文献综述的一部分。在各种荷载条件下对较长长度的柱（和/或梁）进行试验，以建立已知的局部破坏机制与整体破坏之间的关系。同样，这究竟构成什么将取决于对现有文献的回顾。这些部分在更大的结构系统中直接从现有的建筑设计中进行测试。可以与外部顾问进行合作，以确定用于测试的合适系统。疲劳测试和生命周期分析，以确保这些部件的使用没有意外的长期问题。2)测试相同柱的修改版本，充分利用增材制造的能力来改变整个截面的材料厚度。这些部分的优化可能由人工神经网络（ANN）驱动，因为这些被广泛用于优化当今的非线性行为。本部分的目标是找到在给定材料量的情况下，单个完全连接的连续元件所能达到的最大屈曲能力。3)传统轧制后冷压成预先定义的拓扑结构的截面测试。这样做的目的是使这项技术更容易获得，通过将其与与增材制造相关的生产率、成本和环境影响的限制分离开来，将其扩展到更多的受众。在所有这些情况下，测试都将通过ABAQUS中的数值分析进行，并在可能的情况下进行实验室测试，以确保这些测试的有效性。在上述所有内容之前，将进行广泛的文献综述，旨在找到最佳实践和先例，以最佳地接近概述的研究目标。

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.