Our first question looks at the necessity to use 100mm bolts when securing pallet racking into a floor. Our second asks about column guards and whether any guidance exists on what dimension these should be.
100mm bolts, the only way to go?
Q. We have a tenant who would like to install pallet racking in one of our buildings. The floor is a 40mm thick floating screed with a damp proof membrane underneath on top of a concrete slab. The racks are approx 5.5m to the top and 1.1m deep.
They say the only way to fix them is to use 100mm bolts into the floor but these will pierce the DPM which we want to avoid. Are there any other acceptable methods of fixing the racking?
A. Some suppliers do use bolts of this depth to get through the floating screed into solid concrete underneath and this may be why these have been specified in this instance. If the screed is of good quality it may be sufficient to take the uplift forces recommended in the SEMA code without the need to pierce the DPM. Unfortunately the only way to prove this would be to carry out a trial in situ by using one of the specialist fixing companies to help you carry out a test on an area of flooring where a degree of possible damage could be tolerated. They would in addition be able to recommend a shallow fixing which will of course in all likelihood prove to be more expensive.
Racks can be fixed back to the walls and most rack manufacturers supply wall ties for this purpose as long as the building supplier is happy to accept the forces from the rack into his building. Please note these are designed to be used in conjunction with floor fixings and not used as the sole source of stability. If the feet are not provided with some kind of solidity an accidental knock from an errant fork lift truck could push the base of the upright out of its vertical alignment by a considerable amount with predictable consequences.
Similar fixing problems can occur in cold stores where heater mats are often embedded into the concrete. There is a product available that is sometimes used in a situation where there is little or no alternative. The Tico pad is an anti vibration double sided adhesive pad that is usually used to secure vibrating machinery to a concrete floor to reduce movement. On rare occasions this may be the only option available, however you should seek advice from your racking supplier as this is a site specific problem and although differing solutions are available they are dependent on a detailed inspection and analysis of your site.
Column guard guidance
Q. Can you tell me if any guidance exists from SEMA that sets out dimensions for column guards? We have a lot of guards to install and have been asked what the standards are.
A. In short each manufacturer offers different recommendations relating to their column guards so there is no standard guidance.
The purpose of the guard is to absorb kinetic energy from a moving truck and stop it before it hits a rack upright. This is generally done by the steel in the guard distorting and absorbing the energy in the process. As a rule of thumb the amount of steel being used and the distance away from the upright are taken as the governing factors in design, if the effect of floor fixings is ignored. A cheap column guard may therefore be made out of thin, low tensile steel and will perform adequately if it is located a substantial distance from the upright while a more robust thicker design of high tensile steel can be located closer to the upright. Unfortunately only the supplier, who should have carried out performance tests, will be able to confirm the effectiveness of his particular guard, and inform you of what the recommended clearance should be for a particular design.
Usually from a practical point of view I would expect to find this figure to be about 20 to 25mm, as anything much larger than this takes up too much aisle width and ends up creating more problems than it solves. Anything less than this tends not to be as effective as the guard is distorted and will hit the upright anyway.
SEMA is delighted to be working with WLN on the storage Question and Answer Column which is published in WLN on a monthly basis. On the WLN website is a list of previously published columns which we hope you find useful.
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SEMA Annual Safety Conference 2012 – a date for your diary
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