Frequently Asked Questions

Introduction

The Wood Beam (ASD/LRFD) Basic Guide outlines the key properties, loads, and capacities calculated in the summary. You can learn how each of the properties are calculated within your calculation by opening your project in detailed view, or by selecting the arrow on the side of the widget to view the equations, references and descriptions in debug mode.

Project default values can also be used to link code standards, defined default loads, properties, or design criteria so that defined values are automatically pulled to your beam design.

Key Properties

Size and Grade

Our wood beam calculator provides the option of choosing a material size and grade from our extensive database or by creating a custom section. In the member selector you can see which species, size, and grade produces a passing design for your existing inputs.

Alternatively, if your design has a more unique size that is not in ClearCalcs, you can set the Section Type to “Custom Section”. Here you can select the member species and grade and specify your beam’s custom properties.

Beam Plan Length

The beam plan length is the total horizontal plan length of the beam, including any overhang over the supports. This value does not account for any slope.

Supports and Braces

You can design for fixed, pinned, roller, or hinge supports, as well as top or bottom braces. Each support is defined as a distance x away from the leftmost edge of the beam, with bearing length being considered as well.

If you are designing a beam with a cantilever or an overhang, you can place your support at any location along the beam. The support does not have to be placed at a length of 0 or directly at the end of the beam.

The bearing length input represents the length of the beam that comes into direct physical contact with the support, such as the column. If you wish to ignore bearing calculations for your project, enter your bearing length as 0.

Loads

ClearCalcs has a variety of options available for your loading conditions. Distributed loads, line loads, or point and moment loads can be defined in your design.The load type (such as dead load or live load) can be specified for each load as well.

The load locations are measured from the leftmost edge of the beam. Further, self weight can be determined from your member selection by selecting “Yes” under “Include Self-Weight”. Each of the loading conditions are shown through the following diagrams:

Distributed Loads

A line load is a continuous length of the beam which is loaded. This load may start and end at any location. A partially distributed load (PDL), for example, would start and/or end at a location within the beam.

Note also that the start and end magnitudes may differ. A variable distributed load (VDL) is a triangular load, in which the start magnitude does not equal the end magnitude. Note that all distributed loads entered in this table are applied perpendicular to the beam. Each row of this table represents a single pair of start and end locations, but as many rows as desired may be created.

Line Loads

A line load is a continuous length of the beam which is loaded. This load may start and end at any location. Similar to the distributed load inputs a partially distributed load or a variable distrusted load can be designed.

Repeating joists and rafters may be linked into this table by clicking on the chain link icon on the right side of the table, in which the reaction will be approximated as a constant distributed line load. Further, members which have continuous supports and varying reactions, such as is possible in wall analysis modules, may be linked into this table. These continuous support load links are a special case, as they contain detailed data that is not normally possible to enter manually in this table.

Point & Moment Loads

A point load acts over a relatively small area. For example, a weight that has been hung from a ceiling or a column that is supported by a beam. This load may be of any magnitude, and may be located at any point along the beam. Note that all point loads entered in this table are applied perpendicular to the beam.

A moment load causes the rotation of a member about an axis. There are few examples of pure moment loads applied in a typical structure, though the most common occurs if there is a fixed connection between a beam and column. Moment loads are also often used to idealize the effect of horizontal loads on cantilevered attachments on a beam (e.g. a satellite antenna attached to a roof rafter subjected to wind loads).

Another individual beam or column bearing on or connected to this one may be linked into this table by clicking on the chain link icon on the right side of the table. Note that if you wish to connect a repeating joist or rafter, it may be easier to link these as a Line Load instead.

Each row of this table represents a single location, but as many rows as desired may be created. Usually, an ‘Alternative Minimum Live Load’ will appear here by default. This Alternative Minimum Live Load, with load type ‘L2’, is NOT applied at the same time as the normal live load. For some types of surfaces, the building codes require that beams be able to support at least a minimum concentrated live load, regardless of the normal live load, and that is this value. If it is blank (zero), then the default surface type you have selected in your Project Defaults does not require an alternative minimum live load.

Summary

Moment Utilization

The governing moment utilization indicates the ratio of governing moment acting on the member to the fully adjusted bending moment capacity of the beam. The governing moment is shown on the bending moment diagram as shown below for a simply supported beam with a UDL acting along the entire length of the beam.

Shear Utilization

Similar to moment utilization, shear utilization is the ratio of governing shear acting on the member to the factored shear capacity of the beam.

Bearing Utilization

Bearing utilization is the ratio of governing bearing load acting on the member to the bearing capacity at the most critical support. The minimum bearing length is also determined as the minimum length required to support bearing at the end supports.

Deflections

Both the governing live/short term deflection and governing long term deflection is calculated, identifying the maximum deflection anywhere along the beam. Negative deflections indicate downward deflections and do not take into account second order effects. The total deflection is shown in the deflection diagram, due to the selected load combination.