The first question we have for this month is how best to calculate the load capacity of a mezzanine floor. Our second question also involves calculation, this time the SWL of bespoke racking that has been installed by a “friend of a friend”.
Load capacity of a mezzanine floor Q. I have been tasked with finding out the loading capacity of an area of Mezzanine flooring which was already installed within our premises. I need to understand the loading capacity and rating for the installation in line with best practice and whether there is a different rated capacity for Mezzanine flooring (industrial A. First of all at initial construction a Mezzanine should have been fitted with a safe load notice advising as well as the name and contact details of the builder, also first of all the maximum uniform distributed load that the floor has been designed to take, and secondly the maximum point load which might be imposed perhaps by a wheel from a hand truck being used to move items around or even from the footplate of a bay of shelving located on the Mezzanine.
From what you say this is not present so we would suggest enquiring of employees that perhaps were working in the unit at the time the mezzanine was installed or perhaps were working in the unit next door and given how inquisitive people are, might well recall the name of the company from the vans that were parked outside during the build. If you can find out who built it this company should be able to sift through their archives to find the file and hence the information we referred to above.
If this is not successful, we would remark that the installation of mezzanines are subject to building control to ensure that safe escape is possible in the case of fire and to ensure that load carrying capacity is adequate for the purpose and for the numbers of people working on the Mezzanine.
In such circumstances the Local Authority might have something in their files that would give you the information you need including the name of the builder. It may be necessary to pay them for the time that they spend in searching for this information however this is likely to be cheaper than the final option which is the following:
On occasions there are situations where for whatever reason a construction is made without local authority knowledge and approval and if this is the case or even if the local authority were aware of the mezzanine however have no longer the detailed application files you might have to get a company of structural engineers specialist in such structures to measure up what you have, check it to ensure it is in good condition and then to redesign the structure from first principles. Plainly this is the most expensive option and is generally only carried out if no success was achieved in any of the other options. Should you eventually go this route SEMA may be able to suggest some engineering consultants who carry out this type of work or you may have some local contacts in this field yourself.
Home made racking
Q. I have recently started with a company and have noticed that they are using some racking to store metal bars on. These have been manufactured by a “friend of a friend” and I was wondering if there was any way to get these tested to ensure that they meet with any regulations / guidelines and that the correct SWL information is put on to them.
A. As you say these have probably been manufactured by a “friend of a friend” and have probably not been supplied by a SEMA member.
The photos that you sent show two different types of rack – one has back-bracing (the “cross” at the back) and the other does not. I suspect that both should have the back-bracing and it has been omitted on the rack in photo 3 – this back bracing is important as it stabilises the rack in one direction so you should investigate this. The racks are made from hotrolled profile and appear to be welded together. You have two options with respect to SWL information; • Testing • Calculation There are a number of test labs around the country who could carry out a load test for you – most Universities offer this service.
Depending upon the magnitude of load that you want to apply to the rack there are a couple of options 1. Test to destruction. The test lab would load the structure to destruction and would probably do 3 such tests (in order to get a statistically reliable result). This sort of test is best done in a controlled environment using hydraulic rams to apply the load. This will give the highest value of SWL
2. Proof load test. The test lab will load the rack to a specified multiple of the load that you want to carry (say twice the required SWL). Again this is best done in a test lab using hydraulic rams but it can also be done in-situ with dead weights (although this is more hazardous)
As the rack is made from hot rolled profile and appears to be conventionally jointed (welds and bolts) it may well be possible for a structural engineer to do some calculations to get the SWL – This will involve assessing what material has been used and the quality of welding so does carry some risk. SEMA could advise a suitable consultant or you could try a local structural engineer. This will probably be cheaper than testing and it would certainly be less disruptive.
Whichever course you choose you should ensure that SWL information or SWL notice is provided as part of the test/calculation.
SEMA has a code of practice on load notices http://www.sema.org.uk/page.asp? node=2 which gives recommendation on the information that should be on a load notice.
The HSE publication HSG76 also gives some guidance http://www.hse.gov.uk/pubns/book s/hsg76.htm.
Comments are closed.