Design & Engineering

Problem & facts

Due to the complexity and the high number of possible combinations, a complete design check of different load cases at joints have rarely been provided. Manufacturers of joint profiles have dealt only with the capacity/resistance of their products, without considering the ultimate limit design in-situ. The interaction of subgrade-reaction, concrete and loading combinations has not been taken into account.

Traditional load transfer calculations have been based on the bending and shear of steel bars or plates connecting adjacent concrete panels. The results inevitably show that the joint has a lower load capacity (often less than 50%) compared to the interior load capacity of the concrete slab.

The industrial floor itself is always based on a load transfer at joints (usually around 40% when using load transfer systems), whereby the actual design values for the load cases “edge” of the floor slab are significantly reduced. However, this applied percentage is an assumption and up to now, this assumption was mostly neither checked nor confirmed.

Solution & design

N.V. Hengelhoef Concrete Joints in collaboration with International Joint Tech Engineering s.a. is now able to measure the exact load transfer of the Cosinus Slide® joint and provide a complete calculation at ultimate limit state for all relevant loads and combinations. This calculation does not replace the design of industrial floor slab itself, but completes the part required for joint profiles, providing an accurate assessment of load transfer at the joint used in the floor design.

The calculation is primarily based on the theory published in Concrete Society Technical Report 34 (4th edition), and has been independently tested and confirmed using finite element method (FEM).

The material capacities were determined in a nonlinear simulation and with laboratory experiments, and statistically analysed in accordance with EN 1990 Euro code (EC 0). This has provided ultimate capacity values that can be adapted to the required design level in accordance to the various norms and guidelines of different countries by using appropriate safety factors.

Practice & outcome

Cosinus Slide® joint will permit a recommended joint opening of 15 mm, while still ensuring shock and vibration-free passage of trucks or forklifts (see certificates of conformity 020238-14-2 to 4). Due to the shape/geometry of the profile, there is virtually no impact witnessed on the concrete edge when trafficked by pneumatic and hard plastic wheels. As the concrete “fingers” rest directly on each other, fatigue effects and failures at the transition between joint “fingers” and full-depth concrete floor are very unlikely. The Cosinus Slide® joint profile is therefore compliant with the European directive 2002/44/EC concerning exposure of workers to whole body vibrations. Furthermore the possibility of free movement of the Cosinus Slide® joint in horizontal directions and the low friction between slab and ground reduces restraint stresses to a minimum. Due to the above described facts, the serviceability of the Cosinus Slide® joint is proven and maintenance costs for the floor slab, the joint and the forklift wheels are significantly reduced.

However, as with all joint systems, to obtain all the benefits outlined above, it is crucial to install Cosinus Slide® joint in a professional manner, following the guidance procedures provided.