- Elastic Buckling Database for Thin-Walled Metal Columns with Perforation PatternsSmith, Frank H. (2013-09-17)Presented is the data set used in the development and validation of approximate finite strip methods for use in predicting elastic buckling strength of cold-formed steel columns including perforation patterns. The influence of perforations is accounted by reduced thicknesses related to the plate buckling coefficient and transverse web rotational stiffness in the prediction of local and distortional buckling respectively. Global buckling prediction including the influence of perforations uses critical elastic loads of an unperforated section multiplied by the ratio of weighted to gross cross-sectional moment of inertia for flexural buckling and the ratios of weighted to gross cross-sectional warping torsion constant and weighted to gross St. Venant torsional constant for flexural-torsional buckling. Concern for end-user was given and methods are presented in a way for incorporation into governing design standards in Smith's Master's Thesis entitled "Finite strip elastic buckling solutions for thin-walled metal columns with perforation patterns" available at http://hdl.handle.net/10919/23680.
- Segmentation and Recognition of Highway Assets using Image-based 3D Point Clouds and Semantic Texton ForestsGolparvar-Fard, Mani; Balali, Vahid; de la Garza, Jesus M. (2013-02-18)Efficient data collection of high-quantity and low-cost highway assets such as road signs, traffic signals, light poles, and guardrails is a critical element to the operation, maintenance, and preservation of transportation infrastructure systems. Despite the importance, current practice of highway asset data collection is time-consuming, subjective, and potentially unsafe. The high volume of the data that needs to be collected can also negatively impact the quality of the analysis. To address these limitations, this paper proposes a new algorithm for semantic segmentation and recognition of highway assets using video frames collected from a car-mounted camera. The proposed set of algorithms (1) takes the captured frames and using a pipeline of Structure from Motion and Multi View Stereo reconstructs a 3D point cloud model of the highway and surrounding assets; (2) using a Semantic Texton Forest classifier, each geo-registered 2D video frame at the pixel-level is segmented based on shape, texture, and color of the highway assets; and finally (3) based on the results of the 2D segmentation and a new voting scheme, each reconstructed 3D point in the cloud is also categorized for one type of asset and is color coded accordingly. The resulting augmented reality environment which integrates the color coded point clouds with the geo-registered video frames enables a user to conduct visual walk through and query different categories of assets. Experiments were performed on a challenging video dataset containing sequences filmed from a moving car on a 2.2-mile-long, two-lane highway research facility. Experimental results with an average accuracy of 76.50% and 86.75% in segmentation and pixel-level recognition of 12 types of asset categories reflect the promise of the applicability of this approach for segmentation and recognition of highway assets from image-based 3D point clouds. It also enables future algorithmic developments for 3D localization of traffic signs and other assets that are detected using the state-of-the-art vision-based methods.
- Comparison of Bridge Deck Damage Condition Evaluated by GPR and Impact EchoZou, Tao; Moen, Cristopher D. (2013-07-31)
- Comparison of Bridge Deck Damage Condition Evaluated by GPR and Chain DragZou, Tao; Moen, Cristopher D. (2013)
- Test Videos - Compression-Tension Hysteretic Response of Cold-Formed Steel C-Section Framing MembersPadilla-Llano, David A.; Moen, Cristopher D.; Eatherton, Matthew R. (2012-06-19)This paper summarizes results from an experimental program designed to evaluate the tension-compression cyclic axial response of cold-formed steel Csection structural framing members. A new cyclic loading protocol for coldformed steel members is presented that defines the target axial displacement based on elastic buckling parameters. The protocol is used to explore the cyclic response of members experiencing local buckling, distortional buckling, and global buckling deformation. In the experiments, post-bucking energy dissipation was observed along with tension stretching and softening. The quantity of dissipated energy per cycle increased as cross-section and global slenderness decreased. Specimens experiencing local and distortional buckling dissipated more energy per half-wavelength than those experiencing global buckling.
- Test Videos- Flexural Strength Experiments on Exterior Metal Building Wall Assemblies with Rigid InsulationGao, Tian (2012-06-12)This research program evaluated the flexural capacity of a metal building wall system with rigid board foam insulation sandwiched between C- and Z-section girts and through-fastened steel panels. Vacuum box tests were conducted to simulate wind suction on the wall system, and distinct failure modes were observed. The metal panel pulled over the screw heads for wall systems without insulation, however when rigid board insulation was added, the insulation acted as a washer and girt failure or screw fracture was observed. Screw bending and fracture were common in the specimens with the thickest rigid board insulation and for locally stocky cross-sections because a concentrated moment could be developed in the fastener. In these cases wall system capacity was decreased by the presence of rigid board insulation. For wall system specimens with locally slender girts, rigid board insulation did not influence girt capacity because girt deformation under load was primarily in the cross-section and not at the through-fastened connections.