Frictional joint constitutes a constructional connection and have decisive influence on the basic operational parameters of the steel frames and props, i.e. their loading capacity and yielding capacity. Currently applied constructions of frictional joints characterize with low loading capacity and unstable operation. In order to improve their operational parameters a new constructional solution of frictional joint, consisting on the application of resistance wedge assembled between the cooperating sections, was developed. In the paper results of stand tests of frictional joints with the resistance wedge, subjected to the static axial compression, were presented. In order to determine the influence of the resistance wedge on the operational parameters of the frictional joint, obtained results were compared with the results of studies of the frictional joints without the resistance wedge. On the basis of conducted tests and analysis one can state, that application of the resistance wedge influences on the enhancement of loading capacity, improves the state of loading the bolts in stirrups, and creates possibility of regulation of operational characteristics of the frictional joints.

The article presents the results of stand tests and numerical analyses conducted in order to determine the working characteristic of a friction joint used in yielding supports and in friction props. A functional model was used to determine analytically the working of the friction joint. A stick-slip model of intermittent motion and a dry friction model were used to model the joint's yield capacity. The friction joint's working characteristic at axial compression and its yield capacity (i.e. joint tensile force) was determined as a result of the analysis. The results of friction joint stand tests at axial compression have also been presented in the paper and compared to the results of numerical analysis. The results obtained in stand tests and numerical analyses reveal high quantitative and qualitative consistency.

On the operational parameters of frictional joints being applied in the yielding support of dog headings a very significant influence have the initial values of axial forces in the bolts of stirrups, since they decide on load capacity and yield capacity. Value of displacement of a section sliding down (value of the yield in the joint) is a measure of the yield capacity of the frictional joint. In the paper results of stand tests are presented. They were carried out in order to determine the influence of initial values of axial forces in the bolts of stirrups on the value of the yield in the frictional joint. The tests were performed for the straight frictional joints loaded with an impact of freely falling mass. Obtained results should be used practically, at the selection of yielding support for dog headings threatened by dynamic loadings.

Stirrups are a significant component of a yielding support in dog headings. Apart from the constructional linking of the interworking shaped sections, their task is also to ensure their appropriate pressing force and appropriately stable and optimum work of a friction joint and the entire support, both, at rest and when its elements are displaced (yield). The subject presented in the paper relates to an important aspect, therefore, such as a performance analysis of stirrups which, as the key component of a friction joint, have a major impact on the working performance of a yielding support in dog headings. Considering the importance of stirrups in the work of a yielding support in mining headings and their functional problems, operational tests and analyses of such stirrups have been undertaken. This paper presents the results of stand tests of stirrups and their parts (yokes). Working characteristics of stirrups and their yokes were determined according to the tests, and load values were subsequently identified at which permanent deformation or damage occurs. The results obtained and conclusions presented should provide to users, designers and manufacturers of supports a precious source of information on how stirrups and friction joints used in a yielding support of dog headings operate.

In the article there is presented analysis of the state of stress and deformation of the arch frictional joint, which was carried out on the model of these joints using finite element method. Joints were loaded dynamically with the impact of freely falling mass. Arch joints with and without passive pressure were submitted to an axial compression. Physical model of the frictional joint was developed on the basis of system applied during the stand tests. To solve mathematical model an explicit integration method was used. In result of analyses carried out, temporal courses of force transmitted through the frictional joint, and displacements of section sliding down were determined. Distributions of reduced stresses in elements of frictional joint were also determined and the state of deformation was described.