CAREER: Structural Stability and Thin-walled Structures

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Abstract for: CAREER: STRUCTURAL STABILITY AND THIN-WALLED STRUCTURES, CMS proposal 0448707 PI: Ben Schafer, Johns HopkinsThin-walled structures form the backbone of the nation's industrial infrastructure and enjoy wideapplication in civil and mechanical systems. While stability is a fundamental requirement for anysuccessful structure, for thin-walled structures, cross-section stability is the primary constraint. Complex to analyze and difficult to design, thin-walled structures are nevertheless highly efficient. Material is minimized in thin-walled members, a must when embracing costly new materials for use in our high volume, low-cost, physical infrastructure. This proposal advances an integrated plan of theoretical,computational, and experimental work to (1) implement new techniques in computational stability of particular need for thin-walled members; (2) develop and verify new methods that provide more efficient, robust, and reliable designs; and (3) create new resources that increase the breadth and depth of the PI's efforts in structural stability education while strengthening partnerships at Hopkins and in the community. Cross-section instability greatly complicates the behavior of thin-walled members; and current computational stability techniques do little to add clarity. Proposed here is a new modal decomposition technique that provides (i) model reduction, the ability to isolate the strain fields consistent with specific classes of cross-section instability, and then perform meaningful analysis with as little as one degree of freedom, and (ii) modal identification, a means to classify a general member deformation field into the basic modes of cross-section instability which make up that field, and thus quantify modal interactions. Development of modal decomposition provides a unique means to investigate a variety of open questions in structural stability, particularly related to coupled and mixed modes. Empiricism and an over-reliance on classical plate buckling solutions complicates the design of thin walled structures and hinders efficiency as designers are tied to the solutions of the past. A new design method, developed by the PI for thin-walled steel structures, seeks to provide flexibility and reliability by attacking cross-section instability computationally and integrating the results into a comprehensive design process. New developments to extend this design methodology to beam-columns and members with perforations are proposed. Large changes in design such as those proposed here require careful experimentation and computation to understand the ramifications and provide a valid and verified methodology. Further, a specific plan is provided for extending the new design method to thin-walled members made of materials other than steel, including aluminum and thermoplastics.Intellectual Merit: this proposal provides for (i) the development of a novel modal decompositiontechnique of use in model reduction and modal identification in computational structural stabilityproblems and its application to a variety of important stability issues, and (ii) the practical extension and verification of computational structural stability into everyday design of thin-walled steel members, including the unique role of cross-sectional stability under complex loading as in beam-columns, and members with perforations. The proposed modal decomposition technique and the developed design methodologies represent significant advances for both the theory and design of thin-walled members and have the potential to spur new discoveries and innovation. A plan is proposed for extending the design methods to a variety of other important thin-walled materials including aluminum and thermoplastics. The proposed activity relies extensively on the PI's experience in experimental and computational structural stability for thin-walled members and provides a needed platform for continued development.Broader impact: The PI's involvement in development of design specifications and technical committees ensures that both the practicing engineering community and the research community will benefit in the findings. Additionally, the education plan detailed herein insures that high school, undergraduate, and graduate students will also all benefit from the proposed work. The high school outreach efforts focus on enriching the PI's ongoing collaboration with Baltimore Polytechnical High School (Poly), a school with predominately minority student enrollment. Strengthening the relationship with Poly provides an important venue for science and engineering activism with underrepresented groups. The undergraduate education efforts are teamed with the Hopkins Center for Educational Resources and will enable the development of pedagogically sound online teaching guides in structural stability. Research findings, including the educational efforts, will be disseminated by journal papers, conference talks, and by the PI's ongoing efforts with several technical committees.