Blast-Resistant Highway Bridges: Design and Detailing Guidelines (2010) / Chapter Skim
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Pages 100-107
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From page 100... ...
100 7.1 Overview The advantages, capabilities, limitations, and uses of several levels of load and response analysis techniques have been outlined in previous sections of this report. In the sections below, application of both simplified analysis techniques and detailed finite element modeling for the case of blast-loaded bridge columns are illustrated.
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From page 101... ...
101 scenarios include load factors that conservatively account for uncertainties in the assumed loads, these factors should not be used when designing bridge columns to resist blast loads. Regardless of the load prediction technique selected, the result should be a distributed load that varies only with time and approximates the predicted load as it varies in both time and position.
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From page 102... ...
102 factors with each time step, most analyses should not include this additional complexity because the uncertainty in the loads does not justify this effort, and to the knowledge of the authors, no currently available SDOF software has this capability. Additionally, as mentioned above, the current procedure for building components has shown good correlation to experimental results with the selection of appropriate assumed load distributions.
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From page 103... ...
While some finite element implementations of high-explosive modeling have user-friendly graphical user interfaces (GUIs) , many general-purpose finite element codes require a user to manually specify a wide range of parameters, including the geometry, material properties, and mesh characteristics.
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From page 104... ...
104 appropriate for a spherical burst, and likewise, a cylindrical mesh is most appropriate for a cylindrical burst. A non-uniform mesh may not allow the pressure to equilibrate perpendicular to the shock front, and a pressure differential can occur between elements as shown in Figures 88 and 89.
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From page 105... ...
relative to a model with a uniform mesh. At the very least, a model with elements of varying sizes will contain relative inaccuracies from one location of interest to another, and in some cases, the entire model will give deficient results.
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From page 106... ...
106 concrete, and three-invariant formulations are preferable when available to correctly model volumetric expansion (Magallanes, 2008)
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From page 107... ...
factor too high, the coupled surface can be too "stiff," and the shock front will bounce off the Lagrangian surface with too much momentum (Knight et al., 2004)
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