|Principal Investigator: ||Rigoberto Burgueño, Ph.D.|
|Research Assistant: ||Jun Wu|
|Funding Agency: ||Office of the Vice President for Research and Graduate Studies, Michigan State University|
|Period: ||August 2000 – Present|
With outstanding mechanical characteristics, such as high strength-to-weight and high stiffness-to-weight ratio, and high chemical and environmental endurance compared to conventional materials, FRP laminated composites have become of great interest for civil infrastructure applications. The nature of FRP laminated composites makes them strong and stiff in plane along the fiber orientations but rather weak through their thickness. Thus, they are most efficient when used under global in-plane stress demands. Due to their high material costs, a way to employ the high directional efficiency use of FRP laminates in civil structures with limited material is to use them in suitable shapes such as membrane, or tension systems, or shape resistant structures. The objective of the research is to develop and implement an analytical process that integrates shape and material optimization for FRP laminated composites structures. The specific tasks include: a) development of a design optimization approach for shape and material properties; b) development of a material design optimization approach for laminated FRP composites; c) integration of a multi-objective decoupled approach for both shape and FRP material optimization; and d) implementation of the developed multi-objective approach for the design of two types of FRP membrane-based bridge systems.
a) FRP Membrane Beam (CMB) Bridge
b) FRP Membrane Suspension (CMS) Bridge
c) Optimized FRP Shell Structure
Figure 1. FRP Composite Membrane/Shell Structures
An integrated approach for shape and material optimization has been implemented in a two-level uncoupled optimization procedure: 1) Shape and material-property optimization that achieves an optimal shape with an optimal stiffness properties; and 2) Material design optimization that designs an FRP laminate that has the same stiffness properties as those obtained in the first step. The two-level optimization approach combines shape optimization of the membrane geometry with material optimization for the FRP laminate design. The proposed approach takes advantage of decoupling the two different optimization processes and corresponding optimization objectives with respect to their own set of design variables.
a) FRP CMB Bridge Optimum Design
b) FRP Shell Optimum Design
|Figure 2. Shape and Material Optimization of FRP Membrane/Shell Structures|
The developed optimization process is being implemented and evaluated through analytical studies on FRP laminated shell structures and two types of FRP membrane-based bridges. The research work shows that FRPs can be used with higher efficiency in new structural systems as long as their advantageous properties of directional strength, light weight, and tailored properties are properly considered in the design process.
The integrated optimization approach developed in this research provides: 1) a procedure for simultaneously finding the optimal shape and optimal laminate material properties of free-form FRP membranes; 2) an efficient tool to determine maximum stiffness designs by optimizing not only the geometry of the membrane but also the material properties and the laminate design; 3) analytical studies required for the initial development of innovative FRP/Concrete systems that use FRP and concrete in their inherent behavioral characteristics for new bridge superstructures; and 4) analytical tools to aid the rational implementation of FRP laminated composite in structural engineering by developing innovative design concepts.
- Wu, J., "Shape and Material Optimization of FRP Membrane and Shell Systems", Ph.D. Dissertation, Michigan State University, East Lansing, MI, in progress.
- Burgueño, R., and Wu, J., "Development of an FRP Membrane Bridge System", IABSE Symposium: Towards a Better Built Environment – Innovation, Sustainability, Information Technology, Melbourne, Australia, September 2002.