Steel connections play important roles in the integrity of a structure, and many structural failures are attributed to connection failures. Connections are the glue that holds a structure together. The failures of the Hartford Civic Center in 1977, the Hyatt Regency Hotel in Kansas City in 1980, and the I-35W Bridge in Minneapolis in 2007 are all attributed to connection failures. A good connection design requires engineer to have a good understanding of the mechanics and steel behavior. The engineer also should know the fabricator's limitations and experience. In the past 20 years, in order to help students better understand various connection types; many schools have acquired steel sculptures. A steel sculpture is a physical system that shows forty-eight types of connections found in standard construction practices. Unfortunately, because of its size and location (eight feet tall, weighs nearly 2500 pounds and usually erected outdoor), students do not always have easy access to it. Moreover, today's students who belong to the Google generation are more comfortable with web-based learning tools. Through a NSF grant we have created an interactive version of the steel sculpture to provide not only an effective learning opportunity but also a 24-7 access to students and educators in the United States and abroad. This work is the result of a collaborative effort among universities and students from different engineering programs. The virtual sculpture gives the user the freedom to rotate or pan the sculpture to view it from any direction. The user may also isolate any one of the 48 connections for a closer view and learn more about that given connection including: description of the connection, potential failure modes (limit states), sample calculations of each limit state to determine the load carrying capacity of the connection, field examples, and a 3-D finite element model of that connection. The 3-D model provides a visual display of stress distribution in the connection area. The solid model of the steel sculpture was developed using Creo and converted to a 3-D interactive PDF file. This was done to avoid the need for purchasing the Creo software. A web page was also developed where users can download the virtual sculpture and the linked documents. Three survey forms were also developed with a slightly different focus to seek feedback from students, educators, and recent engineering graduates. The user may complete the online survey form after s/he has had an opportunity to explore the virtual sculpture. The capabilities of the virtual steel sculpture will be demonstrated during the presentation.
The main purpose of this study was to develop a mathematical model that could be used to determine the changes in the structural characteristics -such as changes that could occur due to corrosion in the cross-sectional area-momentof-inertia of a bridge -from the knowledge of its loading and deflection. Reconstruction of the cross-sectional area-moment-of-inertia of a bridge from the knowledge of its loading and deflection is an inverse problem. In this investigation, the cross-sectional area-moment-of-inertias of a scaled model of simply supported steel bridge (with simulated corrosion) are reconstructed using the deflection and load data. The deflection data used in this inverse problem were numerically generated using the finite element method and the ANSYS software. The deflection data for each model were then used in the inverse problem to reconstruct the cross-sectional area-moment-of-inertias for the model. To solve the inverse problem, the solution domain was discretized into finite number of elements and nodes. The nodal deflections and slopes were represented by Hermite shape functions. For each element, the strain energy and the work done by the external forces were formulated. The minimum total potential energy principle was then used to create the stiffness matrices and reconstruct the area-moment-of-inertia for each element. The inverse model creates a set of linear equations that must be solved simultaneously. Moreover, since the formulation led to more equations than unknowns, the least squared method was used to minimize the errors associated with the solutions, and to match the number of equations with unknowns. Comparison of the inverse solutions with the direct solutions confirms that the variations in the area-moment-of-inertia for a bridge cross-section can be reconstructed, with good accuracy, from the knowledge of its loading and deflection.
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