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  • Literature on the Load Distributions for Effects on Hydraulic Steel Structures: Notes on Existing Literature for Establishing LRFD Load Factors

    Abstract: Previous to 1993 Hydraulic Steel Structures (HSS) were designed using Allowable Stress Design (ASD); modern design, has transitioned to Load and Resistance Factor Design (LRFD) method, which targets a probability of a limit state. To implement LRFD, an understanding of the probability distributions of the loads applied to the structure, the resistances of the components of the structure, and the approximate durations and overlapping of these loads must be determined. The loads applied to HSS are dissimilar to loads applied to buildings or roads, so existing distributions cannot be applied to this problem. Any attempts to implement LRFD without these distributions will result in designs that do not target the probability of reaching a limit state. The USACE has adapted LRFD load combinations and factors to encompass the different geometry, force and displacement conditions, and environments present in HSS. This work collects literature for load effects on HSS to determine either probabilistic distributions or what loads sufficiently unknown to necessitate new research. Because the loads the HSS are subject to are dissimilar to other designed structures, these load distributions cannot be taken from them directly. Loads considered are hydrodynamic, barge impacts, debris impacts, ice expansion, seismic, wind, and waves.
  • Army Corps to collect Christmas trees at Tionesta Lake

    The U.S. Army Corps of Engineers Pittsburgh District will begin accepting live evergreen Christmas trees at Tionesta Lake, which will be used for aquatic habitat-improvement projects, beginning Dec. 27.
  • Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members

    Abstract: Many concrete structures contain internal post-tensioned steel structural members that are subject to fracturing and corrosion. The major problem with conventional tension measurement techniques is that they use indirect and non-quantitative methods to determine whether there has been a loss of tension. We have developed an acoustics-based technology and method for making quantitative tension measurements of an embedded, tensioned steel member. The theory and model were verified in the laboratory using a variety of steel rods as test specimens. Field tests of the method were conducted at three Corps of Engineers dams, located in Oklahoma, Georgia, and Illinois. Measurements of the longitudinal and shear velocity were able to be made on rods up to 50 ft long. Not all rods of this length were able to be measured and the quality and consistency of the signal varied. There were fewer problems measuring the longitudinal velocity than shear velocity. While the tension predictions worked in the laboratory tests, the tension could not be accurately calculated for any of the field sites. This is because we were not able to obtain the longitudinal or shear velocities in an unstressed state or precise measurements of the longitudinal and shear velocities due to the lack of knowledge of the precise length of the rods in the tensioned state.
  • Engineers assess integrity of Fort Bragg infrastructure following Hurricane Matthew

    Flooding and wind damage brought on by the late season Hurricane Matthew tested not only the resilience of the Fort Bragg community but the integrity of its sprawling and aging infrastructure.
  • Conducting an assessment for Kirwan Dam

    A periodic assessment was conducted for Michael J. Kirwan Dam, Feb. 18-28, as part the USACE Dam