The strength and design criteria for a lift guiding system revisited

Lift guides are subjected to variable loading conditions under loading, normal operation / running, and stopping (under the operation of the safety gear). Safety codes demand that under these conditions the guiding system must be designed with adequate strength to withstand bending and buckling and impose limits on the permissible stresses and deflections. Furthermore, maintaining special ride quality requirements of a lift system might impose additional limits on guide deflections. There have been extensive studies carried out to develop models that can provide adequately accurate results for stresses and deflections that must satisfy these conditions. For example, BS EN81-50 / 20:2020 specifications for guide rail bending deflections are based on a three-span beam model. On the other hand, the model for evaluation of the maximum bending moments is a single span beam with one end simply supported and the other end constrained as built-in (fixed). The influence of various boundary conditions and the issue of selecting and providing accurate, practical models for pragmatic strength evaluation of a lift guiding system are discussed and appraised in the paper. These models can then be used as a starting point for evaluation of special ride quality requirements.