Patterned load

Several tools are available to assist in defining patterned floor loading. These tools are focused on the method described in the GSA theory manual. There are three tools, grouped under the Model > Building modelling menu item.

Create load panels on storeys – Examines the storey grid planes and creates load panel elements

Create patterned loads – Allows specification of adverse and beneficial load factors and creates elements loads for mean and difference loads.

Create patterned load combinations – allows analysis cases to be selected and sets up the combinations of mean and difference analysis cases to give maximum and minimum envelope cases.

Pattered load: Typical workflow

Build a GSA modal as normal. In order to simplify the loading use storey grid planes to define the floor levels. The Create load panels on storeys tool can then be used to create load panel elements where the floor loading is to be applied.

Define the dead and imposed loads as normal, then use the Create patterned loads tool to create a new set of loads on the model. At this stage adverse/beneficial factors can be specified for the loads and there is the option to include any of beam loads, face loads and gravity loads. These are then used to create a mean load case and a set of difference load cases.

$$\begin{aligned} f_{mean} &= \frac{(\gamma_{G,sup}+\gamma_{G,inf})}{2}f_G+\frac{(\gamma_{Q,sup}+\gamma_{Q,inf})}{2}f_Q\\ \Delta{f}_i &= \frac{(\gamma_{G,sup}+\gamma_{G,inf})}{2}f_{Gi}+\frac{(\gamma_{Q,sup}+\gamma_{Q,inf})}{2}f_{Qi}\end{aligned}$$

Where subscripts $G$ and $Q$ relate to permanent (dead) load and variable (imposed) load respectively, and sup and inf relate to unfavourable (adverse) and favourable (beneficial) effects respectively.

These are then used in a linear static analysis as normal.

The final stage is to use the Create patterned load combinations tool which then uses the mean load case and difference load cases to set up combination cases that will give an envelope of the results for the patterned loading.