Live Loads
- Becca Alford (Unlicensed)
Analytics
Live Load Data Types
Eriksson Pipe gives the user an option of four live load data types, HIGHWAY, COOPER SERIES,
AIRCRAFT OR OTHER, and NONE.
The highway live loads default to the values relevant to the Design Code previously specified. Any of these default values can be changed by the user. The governing live load used for design is based on the worst case of the single or double axle loads specified. Live load on the pipe is dependent upon the depth of the pipe, the impact factor, the spread of the loads, and the appropriate multiple presence factor for one, two, three, or four lanes. The user can also select whether or not to include the lane load in the pipe design.
If you choose "HIGHWAY" as the Live Load Data type, you will have access to an additional input window for the live load parameters.
The Cooper series is used by the railway industry to represent the live loads from the locomotive and track above the pipe. If you choose "COOPER SERIES" as the Live Load Data type, you may also need to input the locomotive axle weight as defined by AREMA specifications (72, 80, etc.)
Aircraft or Other allows the user to input his/her own concentrated load or loads. This method is often used for the concentrated loads applied by wheel configurations of aircrafts. The loads can be applied to the surface of a rigid pavement (concrete) or to the flexible pavement/soil surface. If you choose "AIRCRAFT OR OTHER" as the Live Load Data type, you will have access to an additional input window for the live load parameters.
Soil Load Data: Density of the fill material above the top of the pipe.
Fluid Load Data
Depth of Fluid: Depth of fluid inside the pipe.
Fluid Density: Density of the fluid inside the pipe.
Pressure Head: Internal pressure in feet of head (limited to 50 feet).
HIGHWAY Live Load Parameters
Single Axle Load
Use the weight of the largest axle of the Design Vehicle here.
Load Per Axle of Double Axle Load
Use this input for the axle load from the tandem truck.
Tire Footprint Length
Input the length of the tire contact area. Length is defined as the direction perpendicular to the centerline of the axle.
Tire Footprint Width
Input the width of the tire contact area. Width is defined as the direction parallel to the centerline of the axles.
Lane Load
Enter the magnitude of the uniformly-distributed load (area load) to be considered in the lane load portion of the analysis.
Live Load Distribution Factor
Factor for distribution of live load through earth fills. This is specific to the Design Code that you select, but it will not be changed when you change the design code. AASHTO LRFD uses 1.15, while all other codes use 1.75.
Direction of Traffic
Select either ACROSS PIPE, when the traffic is perpendicular to the pipe length, or ALONG PIPE AXIS, when the traffic is parallel to the pipe length.
Impact Factor
The impact factor (also referred to as the dynamic load allowance) typically varies by soil depth. If you select DESIGN CODE, this calculation is done for you. You may also override this value by selecting USER INPUT.
AIRCRAFT OR OTHER Live Load Parameters
Pavement Type
Select either ‘Rigid’ or ‘Flexible or None’. Rigid pavement is assumed to help in the distribution of the load through the soil. Flexible pavement is treated as if you did not have any pavement to help distribute the truck load through the soil.
Rigid Pavement
Number of Loads: Select either 1 or 2 loads (essentially axles).
Wheel Load: The weight of one wheel (1/2 of an axle).
Spacing Between Loads: Input the spacing between the axles.
Pavement Thickness: Pavement thickness or depth is assigned here.
Compressive Strength of Pavement: The 28 day compressive strength of the pavement.
Poisson’s Ratio for Pavement: Typical Poisson’s ratio is between 0.15 and 0.20.
Soil Modulus of Subgrade Reaction: Used to calculate the reaction of the soil to the pavement deflection.
Flexible Pavement or None
Load Magnitude: Weight of a single wheel.
Load Width: Equivalent to the tire width.
Load Length: Equivalent to the tire length.
Spread Through Soil: Basically the slope of the soil prism, and should be the same value as assigned to the LLDF.