CICA TECH CORNER
UPDATE TO CICA GUIDANCE NOTE ON GROUND PRESSURE The CICA technical committee has reviewed the CICA guidance note on crane stability and ground pressure, recommendations of safety factors for allowable ground pressure and allowable axle load calculation have been incorporated in the latest edition of the guidance note. THIS ARTICLE GIVES A PREVIEW OF THIS guidance note, it briefly discusses some key points on crane stability and ground pressure. For more details, refer to the full guidance note which provides guidance to assist on: • Clarifying responsibilities for ground capacity assessment. • Ultimate ground pressure vs allowable ground pressure. • Determining the loads and forces. exerted by mobile cranes to the ground. • Reading and interpreting manufacturer information. • Determining the suitability of the crane mats. • Interpretation of industry adopted rule of thumbs. Effective assessment of ground conditions is essential prior to the safe set up and operation of cranes. To reduce the risk of crane accidents, planning activities shall be carried out by a competent person(s) to assess the capability of the ground to withstand the loads and pressures imposed by the lifting equipment.
GROUND CONDITION Typically, a mobile crane will be supported via one of, or a combination of the following ways: • Natural ground, for example, existing natural ground or pavement. • Constructed crane pad, for example, hardstand. • Existing or purpose-built structure, for example, concrete slab or steel grillage. • Combination of above, for example, piles driven into natural ground that require the crane or a grillage platform to be positioned on it. Each of them will require a method of calculation in their capacity to provide
RESPONSIBILITIES All parties involved in the planning, set up and use of cranes on site must be aware of the fundamental criteria, planning issues and risk assessments that are needed to ensure lifting operations proceed in a safe and stable manner. All parties have shared responsibilities to ensure safe operation on site. Figure 1 – Outrigger Load Change due to Different Load Cases 24 / CAL September 2021
a suitable setup arrangement. Some will simply use industry adopted rules of thumb. Some will require key input from the site and the work of a design engineer with knowledge in the civil, structural and geotechnical area. CRANE LOADING How a crane transfers its load to the supporting surface will depend on the type of crane. There are usually three types of loads: • Axle loads, commonly from pick and carry cranes. To understand a correlation between axle load and ground pressure, further assessment
Figure 2 - Crawler Track Pressure Change due to Different Load Cases www.cranesandlifting.com.au
