For most companies, there comes a time when a decision is made: we are building a new warehouse. The first step is the technological design of the warehouse, which defines the storage technologies, equipment, and machinery necessary for its operation. Later comes the construction design, the selection of a contractor, and finally, the implementation of the investment.
Flooring in warehouses, especially in those where goods are stored at height – several or even a dozen or more meters up, has a very significant impact on the quality of work in such a facility. We can imagine what racks mounted on a floor that is not flat and level would look like. Of course, in the case of racks, a solution that allows for partial leveling of the effects of unevenness is the use of shims under the rack feet. Unfortunately, in the case of a forklift, such a solution is not possible; a deviation of a few millimeters in the forklift wheel will turn into centimeters of deviation for a pallet lifted to a height of several meters. Method for calculating lateral deviation:
point x = h [mm/m] x Hx [m] = … [mm]
For a floor height difference of 1.5 mm over a length of 1 m, the lateral deviation of the forks at a height of 10 m will be 15 mm (1.5 mm/m x 10 m = 15 mm). The deviation does not take into account mast deflection. Consequently, the efficiency and safety of work in the warehouse deteriorate. Many elements contribute to ensuring that our floor, on which racks will be placed and on which our forklifts will move, is of appropriate quality. The basic elements influencing the future functional characteristics of the floor are:
– The stage of the warehouse technological design and architectural design
– The stage of preparing the sub-base for the floor and pouring the first layer of concrete
– The stage of executing the final floor
– Seasoning and expansion joint execution
– Floor operating conditions.
Already at the technological design stage, data should be determined which will later be converted in the construction design into the load to which our floor will be subjected. Of course, errors made in these stages, detected during the design review phase, will cost the least, while those detected after construction is completed will be more difficult to repair. Avoiding errors in the design phase does not guarantee that we will obtain the appropriate quality of flooring in our warehouse. The next stage that may cause serious problems in the future is the preparation of the ground for the foundations and the first pour, the so-called “lean concrete,” i.e., concrete of a class such as C 8/10. The most common sub-base structure is: 30 cm of compacted sand-gravel mix or crushed stone, followed by 10 cm or more of C 8/10 class concrete. Insufficient compaction of the sub-base under the slab can cause the ground under our floor to be unstable, which will cause the floor to be subjected to stress during use, and consequently, it may crack. The compaction index IS is specified in the design and for high-bay warehouses is usually around 0.7 – 0.8 (the maximum value of this index is 1).
The next stage of construction that poses a threat to the future functional values of the floor is pouring the floor. Here, the devil is in the details: the first is the appropriate quality of the concrete delivered to the construction site. The concrete specified in the design (e.g., C 20/25 class concrete) must have the appropriate parameters. Their values and testing methods are described by the standard: PN-EN 206-1:2000.
The article comes from the magazine “Logistyka” 2/2008.