Ocena zachowania się górotworu wokół wyrobisk i skuteczności ich wzmacniania w podziemnych kopalniach rud jest uzależniona od efektywności współpracy obudowy kotwowej z górotworem, którą można oceniać na podstawie odpowiednio zaprojektowanych pomiarów. Na tle opisanych w literaturze kilku rozwiązań dotyczących sposobów monitorowania obciążenia obudów kotwowych autorzy zaproponowali nowe, oryginalne urządzenie umożliwiające masowe pomiary w warunkach kopalnianych. Po przeanalizowaniu zalet i wad istniejących konstrukcji w artykule przedstawiono istotę, zasadę działania oraz metodę pomiaru obciążenia kotwy w wyrobisku podziemnym za pomocą nowego przyrządu. Wykonany prototyp WK-2/8 został wycechowany oraz przetestowany z powodzeniem w warunkach laboratoryjnych w pełnym zakresie pomiarowym. Przyrząd ten, nazwany również wskaźnikiem lub podkładką dynamometryczną, nie wymaga zasilania elektrycznego i umożliwia, stosunkowo precyzyjne (z rozdzielczością 10–14 kN, w zakresie do około 90 kN) i zdalne odczytanie wartości siły osiowej obciążającej kotew (patent AGH) przez każdą osobę znajdującą się w określonym rejonie. Przyrząd może być instalowany w wyrobiskach górniczych w warunkach istniejących obciążeń. Stosunkowo niski koszt wykonania przyrządu pomiarowego, stanowiącego dodatkową podkładkę, jak również łatwy sposób montażu, umożliwiają jego powszechne zastosowanie w kopalniach, gdzie stosuje się kotwienie jako sposób wzmacniania górotworu.
The research paper presents the results of the dynamic analysis of an existing bar dome subjected to wind loads. The calculation model of the structure was constructed using the finite element method. The dome was subjected to the standard wind pressure, assuming that it is operates in a harmonic manner. The numerical analyses were performed with the application of Autodesk Robot and MES3D. The analysis focused on the impact of selected factors such as the frequency of forcing, wind gustiness coefficient and structural damping on the behaviour of structures.
The authors studied the fracture mechanical properties under half-symmetric loading in this paper. The stress distribution around the crack tip and the stress intensity factor of three kinds of notched specimens under half symmetric loading were compared. The maximum tensile stress σmax of double notch specimens was much greater than that of single notch specimens and the maximum shear stress τmax was almost equal, which means that the single notch specimens were more prone to Mode II fractures. The intensity factors KII of central notch specimens were very small compared with other specimens and they induced Mode I fractures. For both double notch and single notch specimens, KII was kept at a constant level and did not change with the change of a/h, and KII was much larger than KI. KII has the potential to reach its fracture toughness KIIC before KI and Mode II fractures occurred. Rock-like materials were introduced to produce single notch specimens. Test results show that the crack had been initiated at the crack tip and propagated along the original notch face, and a Mode II fracture occurred. There was no relationship between the peak load and the original notch length. The average value of KIIC was about 0.602 MPa×m1/2, and KIIC was about 3.8 times KIC. The half symmetric loading test of single notch specimens was one of the most effective methods to obtain a true Mode II fracture and determine Mode fracture toughness.
The objective of this paper is to present a probabilistic method of analyzing the combinations of snow and wind loads using meteorological data and to determine their combination factors. Calculations are based on data measured at twelve Polish meteorological stations operated by the Institute for Meteorology and Water Management. Data provided are from the years 1966 - 2010. Five combinations of snow load and 10-minute mean wind velocity pressure have been considered. Gumbel probability distribution has been used to fit the empirical distributions of the data. As a result, the interdependence between wind velocity pressure and snow load on the ground for a return period of 50 years has been provided, and the values of the combination factors for snow loads and wind actions are proposed.
This paper presents the capabilities of ABAQUS finite-element program [1] in modelling sandwich beams and plates resting on deformable foundations. Specific systems of sandwich beams and plates separated by an elastic core layer were subjected to the action of point and distributed moving loads. A few theoretical examples are provided to present different techniques of modelling the foundations and the moving loads. The effects of the boundary conditions and of the foundation parameters on the deflections of the analysed structures are also presented.
The aim of this study is to find the cost design of RC tension with varying conditions using the Artificial Neural Network. Design constraints were used to cover all reliable design parameters, such as limiting cross sectional dimensions and; their reinforcement ratio and even the beahviour of optimally designed sections. The design of the RC tension members were made using Indian and European standard specifications which were discussed. The designed tension members according to both codes satisfy the strength and serviceability criteria. While no literature is available on the optimal design of RC tension members, the cross-sectional dimensions of the tension membersfor different grades of concrete and steel, and area of formwork are considered as the variables in the present optimum design model. A design example is explained and the results are presented. It is concluded that the proposed optimum design model yields rational, reliable, and practical designs.