Design Code and installation Conditions
- Becca Alford (Unlicensed)
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Design Code
The user can choose which design code they are using, the AASHTO Standard Specifications for Highway Bridges, the AASHTO LRFD Bridge Design Specifications (4th or 7th Editions, along with a proposed “8th Edition”), or the Canadian Highway Bridge Design Code. Upon choosing a Design Code, the load factors, load modifiers (if applicable), strength reduction factors, and highway live load data default to the values relevant to that specific code.
Load Factors and Modifiers
These factors are used in ultimate strength design equations for reinforced concrete. Note that the effects of thrust are generally beneficial to the design and therefore, the load factor for thrust should be carefully selected.
Strength Reduction Factors
The capacity reduction factors are also used in ultimate strength design, along with a factor for modifying the limiting maximum crack width criteria.
Process Factors
Radial Tension Process Factor
Factor for modifying the radial tension strength of plant produced pipe when justified by tests.
Shear Process Factor
Factor for modifying the shear strength of plant produced pipe when justified by tests.
Note: the input inside the Installation Conditions box changes based on the type of installation selected by the user, and will be one of the following:
Installation Conditions – SIDD (Heger) Load System
Installation Type
See LRFD Table 12.10.2.1-1 and Table 12.10.2.1-2 for descriptions of installation types.
Height of Earth Fill
Height of earth fill above the crown of the pipe. The height of fill is measured from the base of the tie if railroad loads are used.
Vertical Arching Factor
Ratio of vertical earth load on the pipe (as measured by the total axial thrust at the springline) to the weight of the soil prism load (VAF, see Figure 3-1).
Horizontal Arching Factor
Ratio of the total horizontal earth load on the pipe (as measured by the total axial thrust at the crown and invert of the pipe) to the weight of the vertical soil prism load (HAF, see Figure 3-1).
Installation Conditions – Radial Load System
Depth of Fill
Depth of the earth fill above the crown of the pipe. The depth of the of fill is measured from the base of the tie if railroad loads are used.
Soil-Structure Interaction Coefficient
Ratio of the actual soil load on the culvert to the soil prism load.
Load Angle
Angle over which soil load is applied to the pipe.
Bedding Angle (Soil, Water, Live Load)
Angle over which soil, water and live loads are resisted at the invert of the pipe. This angle should be greater than or equal to the bedding angle for pipe weight.
Bedding Angle (Pipe Weight)
Angle over which pipe self-weight is resisted at the invert. If set equal to zero, a concentrated line load reaction is assumed by the program.
Installation Conditions – Uniform/Automatic Load System
Depth of Fill
Depth of the earth fill above the crown of the pipe. The depth of the fill is measured from the base of the tie if railroad loads are used.
Soil-Structure Interaction Coefficient
Ratio of the actual soil load on the culvert to the soil prism load.
Lateral Pressure Coefficient
Fraction of vertical earth pressure acting as lateral pressure on the pipe.
Bottom Reaction Width(Soil, Water, Live Load)
Horizontal length at bottom of pipe over which soil, water and live load is resisted, (percent of outside diameter or span of pipe). Must be greater than or equal to the bottom reaction width for pipe weight.
Bottom Reaction Width (Pipe Weight)
Horizontal length at bottom of pipe over which pipe weight is resisted, (percent of outside diameter or span of pipe).
Installation Conditions – Uniform/Manual Load System
Top Load Width
Horizontal length at top of pipe over which user-defined soil pressure is applied, (percent of outside diameter or span of pipe)
Bottom Reaction Width(Soil, Water, Live Load)
Horizontal length at bottom of pipe over which soil, water and live load is resisted, (percent of outside diameter or span of pipe). Must be greater than or equal to the bottom reaction width for pipe weight.
Bottom Reaction Width (Pipe Weight)
Horizontal length at bottom of pipe over which pipe weight is resisted, (percent of outside diameter or span of pipe).
Lateral Pressure Distances
Depth of Fill
Depth of the earth fill above the crown of the pipe. The depth of the fill is measured from the base of the tie if railroad loads are used.