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In Calcs.com there is a designated table for Distributed Loads under the Loads section. This table is accompanied by a diagram of the structural component that is being analysed, which updates in real-time and indicates the loads you have entered. This article will discuss the input parameters in the Distributed Loads table and gives some worked examples on how to input distributed loads into Calcs.com for structural design applications.

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Input Parameters

Pro Tip: You can enter conversion formulas directly into the cell (similar to Excel) for both Start and End locations.
Shortcut: If the end location is the right end of the beam, you can input ‘L’ instead of the actual length value.

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Understanding Tributary Width

Every structural element has an area from which it obtains its load. As with any other area, this can also be expressed as a product of length and width. The length of this area is usually either the length of the element itself or the length of the distributed load (B-A from the table). Tributary width is simply the width of this area. To better illustrate this concept, consider a floor that is supported by members spaced ‘s’ mm apart.
Key Concept: For most cases, the tributary width is the same as member spacing.
Consider beam X, where its tributary area has the same length as the beam and the tributary width is ‘s’. Notice that the tributary area is not always a rectangle and can instead take on a triangular shape. In such instances:
  • The starting and ending tributary widths will be different
  • You’ll need to enter different values for Total Start Tributary Width and Total End Tributary Width
Both tributary width values are measured in millimetres and refer to the width of the tributary area at the starting and ending points of the distributed load, respectively.

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Load Magnitudes

When you click on the Load Magnitudes cell, a new table will appear (see below).
  • First Column: A drop-down menu from which you can choose your load type.
  • Second Column: You can input the magnitude of the load in kilopascals (kPa).

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Examples

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Example 1

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Task

Input a live load of 1.5kPa on a floor joist with a member spacing of 450mm.

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Method

1

Set the Range

Enter 0 for Start Location and L for End Location to apply the load to the full beam.
2

Define Tributary Width

Input the member spacing (450mm) into both the Start and End Tributary Width cells.
3

Apply Load Magnitude

Click the Load Magnitudes cell, select Live Load from the dropdown, and enter 1.5 in the magnitude field.

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Example 2

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Task

Input a dead load of 0.12kPa on a ceiling joist with a member spacing of 600mm.

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Method

1

Set the Range

Enter 0 for Start Location and L for End Location to apply the load to the full beam.
2

Define Tributary Width

Input the member spacing (600mm) into both the Start and End Tributary Width cells.
3

Apply Load Magnitude

Click the Load Magnitudes cell, select Dead Load from the dropdown, and enter 0.12 in the magnitude field.

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Example 3

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Task

Input a live load of 0.25kPa and a dead load of 0.9kPa on a rafter with 600mm member spacing.

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Method

1

Set the Range

Enter 0 for Start Location and L for End Location to apply the load to the full beam.
2

Define Tributary Width

Input the member spacing (600mm) into both the Start and End Tributary Width cells.
3

Apply Multiple Load Magnitudes

Click the Load Magnitudes cell to open the load table. Add two rows:
  • Select Live Load and enter 0.25 in the magnitude field
  • Select Dead Load and enter 0.9 in the magnitude field