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Advances in Cold-Formed Steel Research 

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 a solution.

Million tons of cold-formed metal building products are used in construction industry around the world each year, and this trend is kept increasing due to their construction efficiency. 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 such cold work effect 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 (Figs. 3~13). The findings confirm the effect of the manufacturing process on the structural behavior of cold-formed members, and explain why there is a significant scatter in test load capacities of members with the identical cross-section. Some of research outcomes have been published in journals, conferences and public lectures. Some more publications about the findings are still under preparation.

The aforementioned research is a large study involving various parts of research and is conducted through various projects funded by the university and the Fundo para o Desenvolvimento das Ciências e da Tecnologia (FDCT) of Macao S.A.R. This research is being developed at three main fronts:

(a) Stress-strain models of thin sheet metals (Fig. 9);

(b) Simulations and Predictions for enhanced strengths of cold-worked materials (Figs. 10 & 11);

(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. 3~8, 12 & 13).

Some parts have been completed, some are still in progress, and some will be commenced within next few years. Upon the completion of all the parts, a novel and unified approach for the analysis and design of cold-formed thin-walled structures will be resulted. This new approach will provide a useful tool in optimizing the forming parameters of cold-formed steel sections and will greatly reduce the need for laboratory testing in the development of design rules.

Fig 1.  Manufacturing process of roll-formed tubes

Fig 2.  Manufacturing process of press-braked sections

Fig 3.  Finite element-based method: Numerical tube forming of EHS tubes	Fig 4.  Advanced finite element approach: Numerical stub column test of EHS

Fig 5.  Finite element-based method: Numerical press braking	Fig 6.  Advanced finite element approach: Nonlinear buckling analysis

Fig 7. Numerically predicted local imperfections in an EHS	Fig 8.  FE predicted stub-column behavior of an EHS

Fig 9.  Stress-strain model for stainless steels

Fig 10.  Finite element mesh of a tensile corner coupon	Fig 11.  Numerical coupon tests for determining the strength and ductility of cold-worked materials

Fig 12.  Theoretical predictions of residual stresses and equivalent plastic strains in cold-formed steel channel sections	Fig 13.  Hybrid analytical-finite element approach

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Research Interests 

Cold-formed metal structures, Additive manufactured (3D printed) metal structures, Stainless steel structures, Residual stresses and cold-work effect, Mechanical behavior of sheet metals, Structural stability, Applied mechanics, and Numerical modeling.

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Recent Research Projects and Grants

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Collaboration 

Prof. Ben Young, Professor, University of Hong Kong

Prof. Ming Yan, Professor, SUSTech

Prof. J. G. Teng, Chair Professor, HKPolyU

Prof. K. F. Chung, Professor, HKPolyU

Postdocs: Dr. M.T. Chen, Dr. Z.Y. Kong, Dr. Y.C. Cai.

PhD and Master research assistants: Y. Yao, J.J. Yan, Q. Zhang, K. Yang*, J.F. Huang*, P. Qiu*, C. Cai*.

Undergraduate research assistants: J. Cao*, S. Luo*, L.C. Kong*, Kit Leong*, W.P. Chao*, P. Qiu*

* Graduated

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Selected Publications

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Invited Lectures/Presentations

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