Blast-Resistant Highway Bridges: Design and Detailing Guidelines (2010) / Chapter Skim
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Pages 88-99
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From page 88... ...
88 6.1 Overview The Phase I test program included eight small-scale blast tests at four sets of standoff. The experimental observations and analytical models indicate how cross-sectional shape, standoff, and geometry between the charge and column positions influence blast pressures on the front, side, and back faces of bridge columns.
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From page 89... ...
89 6.3 Blast-Load Guidelines After the completion of a risk and vulnerability assessment, a bridge component should be designed for the appropriate blast load. The following section defines important blast load variables.
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From page 90... ...
90 2.6.4.4.2 Bridge Scour As required by Article 3.7.5, scour at bridge foundations is investigated for two conditions .
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91 5.10.11.4.1d and 5.10.11.4.1e and as modified by Article 5.10.12.3. The provisions of Article 5.10.2.3 shall also apply.
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From page 92... ...
92 5.10.12.2 Blast Design Category A Blast loads should not be considered in the design and detailing of substructure columns designed for Blast Design Category A, as specified in Article 4.7.6.2. C5.10.12.2 Due to the low intensity of the blast loading on substructure columns classified as Blast Design Category A, such columns are expected to perform satisfactorily when designed and detailed for other applicable loads without direct consideration of blast effects.
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From page 93... ...
93 use of a circular column is an effective way of decreasing the blast pressure and impulse on a column relative to a square or rectangular column of the same size, and the decrease in impulse can be up to 34% for small scaled standoffs (see Chapter 5)
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From page 94... ...
94 6.4.3.3 Detailing and Design If the standoff distance cannot be increased to decrease the effects of blast loads on columns sufficiently, the following design and detailing provisions are recommended: increasing the amount of transverse reinforcement, requiring continuous spiral reinforcement or discrete hoops with sufficient anchorage, and avoiding splices. Additional details for these design provisions are given below.
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From page 95... ...
95 specified by Article 5.10.12.3 should be placed throughout the entire height of the column. The minimum amount of confinement reinforcement is increased to improve ductility and energy dissipation capacity of potential plastic hinges.
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From page 96... ...
96 loads are both dynamic loads that induce dynamic structural responses and inelastic behavior. To allow the formation of plastic hinges and achieve a favorable mode of failure (flexure)
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From page 97... ...
97 At the time of this writing (winter 2008) , experimental data to determine the column load resistance in the damaged state are not available.
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From page 98... ...
98 where: θ = Rotation (degrees) μ = Flexural Ductility These limits ensure that column damage is limited to allow continued service following an extreme event.
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From page 99... ...
99 The time varying load should be a triangular load with a magnitude equal to the peak pressure calculated in step 3) , and the triangular load curve should preserve the total impulse.
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