Renjie Liu was a joint PhD in Vrije Universiteit Brussel. He became a PhD student at Beijing University of Technology in 2013. His supervisor in Beijing University of Technology was Prof. Suduo Xue. He won the opportunity to study oversea based on the support of the China Scholarship Council. He was accepted by Prof. Marijke Mollaert in 2015 and he became a Joint PhD in Department of Architectural Engineering at Vrije Universiteit Brussel.
His PhD research was in the field of lightweight structures. He proposed a new pre-stressed spatial structures in view of preventing disproportionate collapse and made it closer to its realisation. The ability to resist disproportionate collapse is an important aspect and should be considered in applications of pre-stressed spatial structures. In the thesis, a new type of pre-stressed spatial structures was proposed in view of resisting the disproportionate collaspe and named as the Annular Crossed Cable-Truss Structure (ACCTS). The research presented in the thesis focuses on the numerical and experimental verification of the ACCTS, and study on the ACCTS in aspects of mathematical modelling of the geometry, form-finding analysis, design of the connections, construction method, structural behavior, the ability to resist disproportionate collapse and membrane roof covering effect on the static behavior and the ability to resist disproportionate collapse. The method of mathematical modelling of the geometry, the method of designing the connections, the construction method, and the simulation method of the lifting operation for the ACCTS were propsed. The reasonability of static behavior, the feasibility of the construction method, the promising ability to resist disproportionate collapse and the possilibility to be covered by a tensile membrane for the ACCTS were proved. The membrane roof covering effect on the static behavior and the ability to resist disproportionate collapse was also illustrated.
He finished his PhD research and passed his public doctoral defense on 23 May 2017 with Greatest Distinction.