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Dynamics of large diameter hydraulic legs under applied test methods

Stoiński Kazimierz, Płonka Marek, Świątek Janina

Archives of Mining Sciences

2022

Vol. 67, no. 2

259--273

The dynamic characteristics of the hydraulic leg are essential for determining the safe working range of roof supports operating in seams threatened by rock mass tremors. The systematic increase in the support of the hydraulic legs due to deteriorating geological-mining conditions has increased their diameters, which currently exceed 0.32 m for the 1st hydraulic stage. Evaluation of the dynamic properties of the roof support and the hydraulic legs are carried out by the Central Mining Institute through calculation methods as an implementation of the Regulation of the Minister of Energy on occupational safety and health. However, the issue of validating the calculations concerning natural scale studies still needs to be addressed. There are significant limitations in this area due to the technical and metrological capabilities of the testing stations. This paper presents an attempt to evaluate bench testing of a hydraulic leg with 0.32 m of the 1st hydraulic stage diameter for the validation of computational and test methods. Results of previous studies affecting the evaluation of the research methods used are also cited. According to the authors, the optimal and economically justifiable direction is to undertake model tests using numerical analyses and to validate these results, based on the study of models of hydraulic legs that are in use at a reduced scale. The construction of testing stations to ensure adequate dynamic loading for the support of the largest diameter hydraulic legs is currently not economically viable. The problem presented, however, is important given the constantly deteriorating geological-mining conditions and the associated threat of rock mass tremors.

Sztywność i nośność śrubowych połączeń kołnierzowych rur dużych średnic

Wojnar A., Kozłowski A.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

2008

z. 50 [256]

299-311

Połączenia kołnierzowe są najczęściej stosowanym typem połączeń w konstrukcjach stalowych wykonanych z rur o dużych średnicach. Dotychczas opracowane metody obliczeniowe pozwalają na określenie jedynie nośności tych połączeń. Pomijają one zagadnienia związane z wyznaczaniem ich sztywności. Sztywność połączeń kołnierzowych można wyznaczyć za pomocą modelu mechanicznego, opracowanego przy zastosowaniu metody składnikowej. Są to jednak dość pracochłonne obliczenia, wymagające zastosowania odpowiednich algorytmów i programów komputerowych. W referacie przedstawiono uproszczone metody obliczeń pozwalające na wyznaczenie charakterystyk podatnościowych połączeń kołnierzowych.

Flange bolted joints are the most popular types of connections in steel elements with circular hollow cross section. This kind of joints is used in steel structures such as chimneys, supports of elevated tanks, wind power plants, etc. The design codes and the analytical methods applied nowadays to calculate their bearing capacity do not cover the methods of calculation of their stiffness. Stiffness of flange bolted joints has an influence on the behaviour of structures with such connections (the natural period of the structures, the horizontal displacements of the structures, etc.) This paper presents the mechanical model of flange bolted joint permitting to assessment the initial stiffness and resistance of joints of this type. To create this model a component method was used. Based on the mechanical model of flange bolted joint, the computer software permitting to calculate the initial stiffness and resistance of flange bolted joint was made. The formulas permitting to calculate the initial stiffness and resistance of joints were made based on results of numerical calculations.