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Structural Engineering and Structural Mechanics Research
The following four faculty members perform research predominantly in the areas of structural engineering and/or structural mechanics. Please click on a project title to read a detailed description of the exciting work they perform in collaboration with their students. Other useful information is only a click away, including selected publications by faculty and their students.
General Areas of Research Interest:
- Structural Analysis and Design Methodologies
- Applications of Object-Oriented Evolutionary Computation in Structural Engineering
- Inelastic Analysis of Structural Steel and Reinforced Concrete Structures
- Automated Performance-Based Design of Structures
- Fatigue Life Prediction of Sign and High-Mast Luminaire Support Structures
Selected Project Descriptions:
Technical reports for the projects listed below are available at www.eng.mu.edu/foleyc
Structural Analysis of Sign Bridge Structures and Luminaire Supports
This project was funded through the Wisconsin Highway Research Program of the Wisconsin Department of Transportation (Proj. No. 0092-00-0016). The study included detailed finite element analysis (FEA) of full-span overhead structures supporting both aluminum and variable message signs. FEA was also used to study the stress field at the base of high-mast-luminaire (HML) support structures. The FE models, wind speed statistics for the metro-Milwaukee area, and simulated turbulent wind models were used to generate fatigue-life estimates for the structures studied. The impact of truck-induced gust pressures on the overhead sign supports was evaluated and the susceptibility of sign support and HML supports to aeroelastic phenomena was evaluated.
Optimal Design of Steel Frames Using Advanced Analysis and Genetic Algorithms
This project was funded through the National Science Foundation (Proj. No. 9813216) and it resulted in the development of methodologies for automating and optimizing the design of structural steel frames with fully- and partially-restrained connections. An object-oriented evolutionary algorithm was developed to select optimized steel members and connections using distributed plasticity as the design evaluation basis. The advanced analysis methodology allowed the design to be conducted in the absence of specifications/codes and is a first step to true automated and optimized performance-based design of structures.
Selected Graduate Student Theses Directed by Dr. Foley (complete vitae available at www.eng.mu.edu/foleyc):
Ginal, S. (2003) "Fatigue Performance of Full-Span Sign Support Structures Considering Truck-Induced Gust and Natural Wind Pressures," M.S. Thesis.
Peronto, J.L. (2003) "High-Cycle Constant Amplitude Fatigue Life Variability of Welded Round HSS Y-Joints," M.S. Thesis.
Shock, B.T. (2003) "Automated Design of Steel Wide-Flanged Beam Floor Framing Systems Using a Genetic Algorithm," M.S. Thesis.
Schinler, D. (2001) "Design of Partially Restrained Steel Frames Using Advanced Analysis and an Object-Oriented Evolutionary Algorithm," M.S. Thesis.
Buckhouse, E.R. (1997) "External Flexural Reinforcement of Existing Reinforced Concrete Beams Using Bolted Steel Channels," M.S. Thesis.
Selected Publications by Dr. Foley and his Students (complete vitae available at www.eng.mu.edu/foleyc):
Foley, C.M. and Schinler, D. (2003) "Automated Design of Steel Frames Using Advanced Analysis and Object-Oriented Evolutionary Computation," Journal of Structural Engineering, Vol. 129, No. 5, pp. 648-660.
Foley, C.M. (2002) "Optimized Performance-Based Design for Buildings," Chapter 8 in Recent Advances in Optimal Structural Design, Burns, S.A., Ed., ASCE/SEI Technical Committee on Optimal Structural Design, American Society of Civil Engineers, Reston, VA (169-240).
Foley, C.M. and Ginal, S.J. (2002) "Fatigue Evaluation of Full-Span VMS/CMS Support Structures Subjected to Simulated Truck-Induced Gusts and Natural Wind Turbulence," Proceedings of the 2002 Structures Congress and Exposition, Denver, CO, April 4-6, CD-ROM (abstract).
Foley, C.M. (2001) "Advanced Analysis of Steel Frames Using Parallel Processing and Vectorization," Computer-Aided Civil & Infrastructure Engineering, Blackwell Publishers, Vol. 16, No. 5, pp. 305-325.
Foley, C.M. and Buckhouse, E. (1999) "Method to Increase the Capacity and Stiffness of Reinforced Concrete Beams," Practice Periodical on Structural Design and Construction, ASCE, Vol. 4, No. 1, February, pp. 36-42.
Dr. Foley's Personal Homepage: www.eng.mu.edu/foleyc
General Areas of Research Interest:
- Elasticity
- Structural Mechanics
- Mechanics of Electronic Assemblies
- Microcantilever Sensors
Selected Project Descriptions:
Modeling of Microcantilever Beam Sensors
Microcantilever beam sensors are beams of very small scale (~0.1-mm length) used to measure the presence and concentration of particular biological or chemical agents in a gas or liquid. Such devices operate on the principle that a beam's vibrational characteristics are dependent on the mass properties of the beam. A microcantilever sensor is coated with a special layer (e.g., polymer) that is designed to absorb only a particular analyte (i.e., the target substance that one wishes to detect). Because the beam mass is so small, the additional mass of the absorbed analyte is sufficient to alter the vibrational frequency and possibly other dynamic characteristics of the system. By understanding the dynamics of the system, it is possible to correlate the frequency shift to the concentration of the analyte in the environment.
The specific goals of this project are to (1) develop analytical models to understand the interplay among the geometric, material, and load parameters of the system, (2) perform numerical simulations to confirm the analytical models, (3) use the analytical models to perform parametric studies for the purpose of optimizing microcantilever designs, and (4) perform experimental studies to confirm theoretical results and to explore feasibility of practical implementation. This project is an interdisciplinary study involving collaboration with Dr. Isabelle Dufour of the Université Bordeaux, Bordeaux, France, and Dr. Fabien Josse of Marquette’s Department of Electrical & Computer Engineering).
Analytical Formulae for Solder Joint Strains in Microelectronic Structures
When an electronic assembly is subjected to thermal loading, significant axial and shear strains may develop in the solder joints that connect various electronic components to their supporting substrate structures. Because these loads and the resulting strains tend to be of a cyclic nature (e.g., on/off power cycles in a computer or natural daily thermal excursions for outdoor structures), the strains in the joints may eventually result in low-cycle fatigue failure of one or more joints and, hence, electrical failure of the device.
In this study, analytical expressions are derived for calculating the axial and shear deformations that occur in an area-array of solder joints that connect a component to a substrate. The strains develop because of the mismatch in CTE (coefficient of thermal expansion) between the component and substrate materials. Results are conveniently expressed in terms of correction factors that are applied to the easily calculated free-expansion estimate for shear deformation. The analytical results clearly indicate the relationship between the correction factors and the physical parameters of the problem: (a) the dimensions and material properties (elastic and thermal) of the component and substrate; (b) the material properties of the interconnect material (effective Young's modulus and Poisson's ratio); (c) the array size and population; and (d) the geometric parameters of the individual joints. The solution is based on a theoretical model of two circular elastic disks connected by an elastic layer whose distributed axial and shear stiffnesses are related to the joint/array characteristics by means of the authors' previously derived stiffnesses for a single joint.
Selected Graduate Student Theses and Dissertations Directed by Dr. Heinrich (click here for complete vitae):
Fischer, Mark, (expected 2007), “Analytical Modeling of Microcantilever-Based Dynamic Microsensors in Lateral Vibrational Mode,” M.S. Thesis.
Sampath, Uttara, (2005), “Analytical Modeling of Polymer-Coated Microcantilever Dynamic Microsensors,” M.S. Thesis; co-advisor with Dr. F. Josse).
Shakya, S. (2000), "Stress Analysis of Bonded Axisymmetric Assemblies under Thermal Loading: Applications in Microelectronics," Ph.D. Dissertation.
Saad, H. (2000), "Calculation of Solder Joint Stiffness Using Three-Dimensional Finite Element Analysis: Comparison with Short-Beam Analytical Estimates," M.S. Thesis.
Shakya, S. (1995), "Simplified Stress Analysis of Axisymmetric Solder Joint under Thermal Loading," M.S. Thesis.
Swanson, J. (1995), "Elasto-Plastic Analysis of Column-Grid-Array Solder Joints," M.S. Thesis.
Selected Publications by Dr. Heinrich and his Students (click here for complete vitae):
Lochon, F., Dufour, I., Heinrich, S.M., Josse, F., Rebière, D. (2006) “Effect of Partial Sensitive Coating Coverage on the Limit of Detection of Microcantilever Chemical Gas Sensors,” to appear in Proceedings, 11th International Meeting on Chemical Sensors, Brescia, Italy, July 2006.
Sampath, U., Heinrich, S.M., Josse, F., Lochon, F., Dufour, I, and Rebière, D. (2005) “Study of Viscoelastic Effect on the Frequency Shift of Microcantilever Chemical Sensors,” Proceedings, 2005 IEEE International Frequency Control Symposium, Vancouver, BC, Canada, Aug. 29-31, pp. 455-462.
Dufour, I., Heinrich, S.M., and Josse, F. (2004) “Strong-Axis Bending Mode Vibrations for Resonant Microcantilever (Bio)Chemical Sensors in Gas or Liquid Phase,” Proceedings, 2004 IEEE International Ultrasonics, Ferroelectrics, and Frequency Control 50th Anniversary Joint Conference, 6 pp., Montreal, Canada, August 24-27, 2004.
Heinrich, S.M., Shakya, S., Lee, P.S., and Liang, J. (2002) "Analytical Expressions for Shear and Axial Joint Deformations in Area-Array Assemblies Due to CTE Mismatch," Proceedings, 2002 ASME International Mechanical Engineering Congress and Exposition, Vol. 2, Paper No. IMECE2002-39636, 13 pp., New Orleans, LA, November 17-22.
Swanson, J.A., Heinrich, S.M., and Lee, P.S. (1999) "An Elastoplastic Beam Model for Column-Grid-Array Solder Interconnects," Journal of Electronic Packaging, ASME, Vol. 121, No. 4, pp. 303-311.
Heinrich, S.M., Shakya, S., and Lee, P.S. (1997) "Improved Analytical Estimate of Global CTE Mismatch Displacement in Areal-Array Solder Joints," Journal of Electronic Packaging, ASME, Vol. 119, No. 4, pp. 218-227.
Heinrich, S.M. (1996) "Membrane Analogy for Saint Venant Torsion: New Results," Journal of Engineering Mechanics, ASCE, Vol. 122, No. 11, November, pp. 1110-1112.
Dr. Heinrich's Personal Homepage: click here
General Areas of Research Interest:
- Inelastic Stability
- Plastic Analysis
- Fire Resistance of Steel Structure
Selected Project Descriptions:
Not available at present.
Selected Graduate Student Theses and Dissertations Directed by Dr. Vinnakota:
Foley, C. M. (1996) "Inelastic Behavior of Partially Restrained Steel Frames Using Parallel Processing and Supercomputers," Ph.D. Dissertation.
Li, Zenglin (1996) "Stability of Single Story Steel Frames with Leaning Columns," M.S. Thesis.
Klein, D. M. (1996) "Investigation of Lateral Load Sharing in Rectangular Framed Mill Buildings with Overhead Crane Systems," M.S. Thesis.
Schleusner, G. (1990) "Investigation of Rotational Restraint Provided by Double-Angle Section Bolted to a Gusset Plate," M.S. Thesis.
Foley, C. M. (1989) "The Use of K-factors in Unbraced Frames - A Critical Study," M.S. Thesis.
Selected Publications by Dr. Vinnakota and his Students:
Vinnakota, S. (2005) Behavior and LRFD of Steel Structures,McGraw-Hill Book Co., NY.
Foley, C.M., and Vinnakota, S. (1999) "Inelastic Behavior of Multi-Story Partially Restrained Steel Frames: Part II," Journal of Structural Engineering, ASCE, 125(8), pp. 862-869.
Foley, C.M., and Vinnakota, S. (1999) "Inelastic Behavior of Multi-Story Partially Restrained Steel Frames: Part I," Journal of Structural Engineering, ASCE, 125 (8), pp. 854-861.
Vinnakota, S., and Foley, C.M. (1998) "Second-Order Elasto-Plastic Analysis of Steel Frames - Review and Comments," Proceedings Annual Technical Session, Structural Stability Research Council.
Foley, C.M., and Vinnakota, S. (1997) "Inelastic Analysis of Partially Restrained Steel Frames," Engineering Structures, Vol. 19, No. 11, pp. 891-902.
Dr. Vinnakota's Personal Homepage: click here
General Areas of Research Interest:
- Repair and Retrofit of Structures
- Fiber-Reinforced Polymer (FRP) Materials
- High Performance Concrete
- Prestressed Concrete
- Numerical and Experimental Modeling
Selected Project Descriptions:
Durability of Bond between FRP and Concrete in Moisture Environment
The use of fiber reinforced polymer (FRP) composite materials for infrastructure rehabilitation and retrofit applications has been widely studied and is now making its way into regular commercial applications. However, the performance of the FRP retrofitted structures depends on and is limited to the bond between FRP and concrete. The debonding failure in the concrete structures with externally bonded FRP has two major modes: cohesive failure in the concrete surface layer and adhesive failure in the interface between concrete and adhesive layer. This study experimentally investigates the mechanism of deterioration for the bond between CFRP plate and concrete due to moisture attack. A simple experimental approach was developed in this study to directly measure the moisture condition in the interface between concrete and adhesive layer with function of immersion duration in water. This method can be used as a direct and uniform criterion for the deterioration of the bond between concrete and FRP composites in moisture environment. Modified Double Cantilever Beam (MDCB) test was used to measure the interfacial fracture energy for the CFRP plate debonding from concrete substrate under Mode I loading. The MDCB specimens were submerged for different periods before they were tested. When the value of interface region relative humidity (IRRH) increased, fracture load and fracture energy decreased and failure mode was also changed from cohesive failure to adhesive failure.
Design Model for FRP-Strengthened Reinforced Concrete Beam
A common failure mode of FRP-strengthened reinforced concrete beams is delamination of the FRP material from the concrete surface. This kind of failure is characteristically sudden and catastrophic. Therefore, a design methodology is required that provides adequate safety against this failure mode. The objective of this project is to establish a design method to prevent delamination failure in FRP retrofitted reinforced concrete beams. Theoretical analysis and finite element analysis are used to establish the initial design model. Experimental tests are used to verify and modify the model.
Selected Publications by Dr. Wan:
Wan, B., Harries, K.A., and Petrou, M.F. (2002) “Transfer Length of Strands in Prestressed Concrete Piles,” ACI Structural Journal, Vol. 99, No. 5, September-October, pp 577-585.
Sutton, M.A., Wan, B., Petrou, M.F., and Harries, K.A. (2002) “Two-Dimensional Computer Vision to Investigate FRP-Concrete Bond Toughness,” Advanced Measurement Methods, Vol. 1, May,
Wan, B., Petrou, P., Harries, K.A. and Hussein, A.A. (2002) ""Top Bar” Effect in Prestressed Concrete Piles,” ACI Structural Journal, Vol. 99, No. 2, March-April, pp 208-214.
Petrou, M.F., Wan, B., Joiner, W. S., Trezos, C.G. and Harries, K.A. (2000) “Excessive Strand End Slip in Prestressed Piles,” ACI Structural Journal, Vol. 97, No.5, September-October, pp 774-782.
Petrou, M.F., Wan, B., Gadala-Maria, F., Kolli, V.G., and Harries, K.A. (2000) “The Influence of Mortar Rheology on Aggregate Settlement,” ACI Materials Journal, Vol. 97, No. 4, July-August, pp 479-485.
Dr. Wan's Personal Homepage: click here
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