Defining the Applied Loads

The Load Control Toolbar

Sub-menus are also available to define or modify various nodal and member loadings. These sub-menus appear along the side of the screen. The types of loads available are the following: concentrated loads at nodes, moments applied at nodes, moments applied at the ends of members, uniformly or linearly distributed loads along members, variations of temperature applied to members, and global load-trains (live load for bridges).

The Load case and Load combination menu buttons are only active in the Advanced Edition (see Advanced Edition).

General Information

Nodal Loads

This sub-menu allows the user to define the concentrated loads on structure nodes. It uses the global coordinate system.

Moments Acting on Member Ends

This sub-menu allows the user to define concentrated moments at the ends of members. Moments applied in a counterclockwise orientation are positive. "Ma" denotes the moment applied at the "initial" node of the member, while "Mb" is the moment applied at the "ending" node of the member.

Linear and Uniform Distributed Loads

This sub-menu allows the user to define linearly varying or uniformly distributed loads over a member. The user can specify the global or local member coordinate system for the loading direction.

Thermal Loads (Temperature Changes)

This sub-menu allows the user to define a linear temperature gradient over the member depth. The user specifies the temperature on the sectionís top edge (i.e., on the positive side of local y-axis) and on the bottom edge (i.e., on negative side of local y-axis). Ftool must have access to the section depth to impose this loading Ė even for "generic" sections.

Load-Trains (Vehicle Live Loads for Bridges)

This sub-menu allows the creation of live loads (on bridges, for example) that are used to calculate envelopes of internal forces (see Results - Load-train Envelopes Toolbar). A load-train is composed of concentrated forces, uniformly distributed forces and live loads (representing the population of small vehicles on a bridge). Concentrated and distributed loads are assumed in the vertical top-bottom direction. Therefore, according to the sign convention of Ftool, all load values are negative. In case the user does not enter a negative sign for a load value, the program automatically changes the sign of this value.

The concentrated and distributed load matrices resize themselves automatically: once the user begins to fill out the last row of each matrix, a new row is created below it. Loads can be deleted by either setting the load values to zero or by selecting the desired rows and pressing the Delete key on the keyboard. The matrix will then also resize itself accordingly.

The currently selected load train may be defined with the dropdown list on the top-right corner of the programís window. This dropdown list is only enabled when in either Influence Line or Load Train Envelope result modes and/or if in the load train definition menu.