Gary Marquis conducts research in mechanics of materials with special focus on fatigue of materials and welded structures. His research activity has focussed on the role of complex multiaxial loading and service loading on the fatigue strength of welded structures and on the development of reduced weight steel structures by incorporating higher strength steel in conjunction with improved welding processes and post-weld improvement technologies. 

In 2006 Professor Marquis was elected as Chairman of Commission XIII: Fatigue of Welded Structures and Components of the International Institute of Welding (IIW). He was re-elected in 2009 and 2012. In 2008 he joined the Technical Management Board (TMB) of the IIW which oversees all scientific, technical and standardization activities of the organisation’s 23 technical working units. In 2011 he was elected as TMB Chairman. In 2011 Prof Marquis was elected as a member of the IIW Board of Directors and became President of the IIW for a three-year term in 2014.

Since 2013, Prof Marquis has served as the Dean of the School of Engineering at Aalto University. Previously he has been an affiliated Professor of Lightweight Structures at the Royal Institute of Technology in Stockholm, Sweden and visiting professor at Kyushu University in Fukuoka, Japan and EPFL in Lausanne, Switzerland.