Working Stress Design (WSD)

Load combinations and load factors

When designing with the WSD method, the analyzes are base on the same load combinations than the ones used for the LSD method with all load factors \(\alpha\) equal to 1. Clause 6.4.2.

Testing

The allowable capacities of the formwork and falsework equipment in North America are mainly determined by destructive testing of the components. Testing are design to identify the ultimate capacities of the component, the allowable capacities are a faction of the measured ultimate capacities. The ultimate capacities are divided by the safety factors listed below. Note that the capacity published by different manufacturer should identify the safety factor of the equipment. This is important since some equipment are tested for the US market and the US have sometime different safety factor than the one used in Canada.

Safety factors (SF) for falsework components
ComponentMetalWood
Horizontal flexural members (joists, stringers)2.22.2
Systems (shoring towers, trusses)2.52.5
Tube and coupler2.5NA
Single post for falsework3.03.0
Single post for reshoring2.53.0
Table 7, Clause 9.2
Safety factors (SF) for formwork components
ComponentMetalWood
Panel and panel stiffeners2.02.5
Plumbing braces2.03.5
Form ties2.0NA
Form anchors2.0NA
Form hangers2.03.0
Table 7, Clause 9.2
Lifting equipment

Equipment and hardware used for lifting shall have a safety factor 5
Clause 9.3.8.3