Applicability Of Superposition To Bolted Joints Under Combined Loading

Abstract

Experimental investigations were developed to allow modelling of the force deformation characteristics of two member bolted joints subjected to pure shear, pure rotational am combined lateral am rotational forces loaded at various angles to grain. Wood-to-wood and wood-to-metal member combinations were studied. the pure shear joint force-deformations using metal side members were modeled using non-linear, vector am secant models. Similar types of models were developed for pure rotational am combined loading joint force deformations with metal side members. Joints under combined loading were analyzed by superposition of the models used for the pure shear am pure rotational joints. Using wood as the side member,each of the three types of joints was modeled using the non-linear, vector am secant models and by the respective super-positioning of the individual non-linear, vector am secant models for each of the two wood members in the joint. '!he actual number of grain angle combinations for different wood-to-metal am wood-to-wood joints used for pure shear, pure rotational am combined loading were 6: 6, 4: I am 4: I respectively, with three replications for each grain angle. Analysis of deformation errors at NDS load level by statistical methods and up to NDS load level by an averaging technique showed the secant model as the best representative for the pure shear joints. The non-linear model was shown to be the next best model. The vector and superposed models were ranked behind these two with no clearly defined order. A similar model ranking was obtained for the rotational joints and the joints under combined loading. However for all the joint types, the vector/superimposed vector. models yielded the next best results behind the non-linear models. In all cases, the superimposed models gave results that were poorer than the secant or non-linear models without a clearly defined order of ranking. Only one set of wood-to-wood.joints was used for pure rotational and combined loading and hence the results from the analysis of these joints were inconclusive. The secant model described the experimental data well at the NDS load level unlike the other models which were chosen to describe the experimental data up to and including the NDS load levels.