Zur bemessung von kopf- und fußspindeln in traggerüsten

The structural design of working and access scaffolds as well as of falsework constructions is in the majority of all relevant cases significantly influenced by the stiffness properties and the load bearing capacity of the used head- and base-jacks. Up to now the national system of rules defined a conservative approach for modelling these node-points. These assumptions were developed further by establishing stiffness parameters for the contact surface between the footplate of the base-jack and the supporting plane during the European standardization process in recent years. Within the presented paper, the actual specifications of the European standards for modelling the bearing point of scaffolds and falsework will be discussed. A comparison between these information and available test data as well as the results of numerical simulations for the node-point under consideration will be performed. It can be shown that the stiffness characteristic for the elastic restraint of base-jacks with an outer diameter of 38 mm imparted in DIN EN 12811-1:2003 [3] is sufficiently conservative. As there is no verification scheme for moulded footplates of basejacks in the actual standards - only lump-sum figures for stiffness and geometric properties can be found -, a proposal adressing this matter will be explained. The actual valid system of regulations gives no information concerning the quality of the restraint for the head-jacks by the formwork-construction placed above. Crucial parameters are the load-application eccentricity and the type of the stringer used. This paper presents a structural model for the detailed analysis of this node-point. By varying the input-parameters, criterias for judging the wide-spread used construction-types based on prefabricated timber formwork beams according to DIN EN 13377:2002 [23] are developed.