|Wai-Meng QUACH, 郭偉明 (Stephen)|
Associate Professor (email@example.com)
Impactio Academic Ranking: Top 0.01% in Structural Engineering, Top 0.03% in Materials Science, & Composite Material
Bio | Profile | Research | PhD-PostDoc Opportunities
No longer a Dream for predicting geometric imperfection, residual stresses and strength enhancement in cold-formed steel structures realistically ! A deterministic approach with advanced numerical modeling of manufacturing processes is now a solution.
Million tons of cold-formed metal building products are used in construction industry around the world each year. This trend is kept increasing due to their construction efficiency in Modular integrated Construction (MiC). The structural performance of cold-formed thin-walled metal structures is known to be sensitive to initial imperfections which include both geometrical imperfection and cold work due to forming. Traditionally, this cold work effect has been taken into account by using separate specifications of mechanical properties for the flat portions and the corner regions in conjunction with idealized residual stresses models which are based on inappropriate assumptions disregarding the effect of the manufacturing process. Indeed, various cold-formed sections are fabricated by different manufacturing processes (Figs. 1 & 2). Hence, a research has been being carried out to seek for the solution to overcome this shortcoming.
Dr. Quach’s research has been focused on the development of various scientific tools (i.e. analytical models, empirical models, and hybrid analytical-finite element approaches) to accurately model manufacturing processes and quantify initial imperfections and the cold work effect (i.e., residual stresses and plastic strains) and in various types of cold-formed members (e.g. channels and hollow sections). The main contribution from this research is to correct the major deficiencies in existing knowledge and existing design approaches by using these proposed tools. The findings confirm the effect of the manufacturing process on the mechanical and structural performance of cold-formed metal members. The proposed methods/tools can be used to predict geometric imperfections, residual stresses and strength enhancement in cold-formed metal structures realistically.
An integration of these proposed scientific tools forms a novel and unified approach for the analysis and design of cold-formed thin-walled structures. This new approach can be used for optimizing the forming parameters of cold-formed steel sections and will greatly reduce the need for laboratory testing in the development of design rules. This research is being developed at three main directions:
(a) Stress-strain models of thin sheet metals;
(b) Simulations and predictions for enhanced strengths of cold-worked materials;
(c) Simulations and predictions for initial imperfections (including geometrical imperfections, residual stresses, plastic strains) in cold-formed members and their effect on structural performance (Figs. 3~9).
2. Metal 3D printing in Construction
Additive manufacturing, commonly known as 3D printing, is an evolutional technology which has already been embraced by different industries, such as manufacturing, aerospace and biomedical engineering. Despite the exciting prospect of its application in civil engineering, additive manufacturing technology is still at a perceived stage for construction industry. The benefits and potential in construction industry are rarely known in the field at this stage. This multi-disciplinary research is under collaboration between University of Macau (UM) and Southern University of Science and Technology (SUSTech). It aims to investigate the mechanical properties and structural performance of additively manufactured metal tubular sections (see Figs. 10 and 11). So far, high strength steel tubular stub columns additively manufactured by selective laser melting (SLM) with different scanning patterns, have been tested. The anisotropy on mechanical properties has been examined through tensile coupon tests in both longitudinal and transverse directions. The influences of scanning patterns on mechanical properties and structural behavior of as-printed high strength steel tubular sections stub columns were also investigated. The test results have been used to assess the applicability of existing design provisions that originally developed for conventionally produced hot-rolled and cold-formed steel tubular sections to the additively manufactured high strength steel tubular sections.
Journal Papers (*Corresponding author; ^ UM student or UM Post-Doc.)