Experimental study on an overhead crane passing a rail track joint

Purpose. To confirm the theoretical conclusions that determining the load from the wheel impact with the joint of rails in the metal structures of overhead cranes used in the technological processes at ore mining and processing mills and integrated works and moving along the rail tracks requires that the dynamic magnification factor should take into account the trolley position. Methodology. To assess the load to which the crane metal structures are exposed the electric strain measurement method using direct bridge circuit was chosen. To calibrate the strain measurement system, the direct method was used, under which calibration is performed directly on the structure on which experimental studies will be carried out in the future. Findings. It was established that the dynamic magnification factor in the metal structure of the overhead crane had the following values when passing the last rail joints: 1.54 (with the trolley in the middle of the bridge), 2.46 (with the trolley at 0.25 of the crane span from the end beam), 3.33 (with the trolley in the extreme position). So, with the trolley being at a distance of 0.25 of the crane span from the end beam, the dynamic magnification factor is 74%, and with the trolley in the middle of the bridge, it is 46% of the dynamic magnification factor if the trolley is in its extreme position. Originality. The scientific novelty consists in the first experimental confirmation of the results obtained in the theoretical studies on the overhead crane passing the joints of the rail track with regard to the crane trolley position, which leads to changes in the stiffness of the main beam in the interval between the trolley and the final beam. Practical value. The results obtained enable calculations on the crane bridge metal structure during the design and repair of the main and end beams taking into account the value of the dynamic magnification factor, which allows increasing the reliability and durability of the crane metal structure as a whole.

Numerical simulation of transient processes in propeller shaft straining under ice loads

Object and purpose of research. The object of the research is the shaftline of an icebreaker and ice-going vessels, the purpose is to develop an algorithm for determining the loads for calculating the strength of the shafts of icebreakers and icegoing vessels under ice loads in a nonlinear dynamic setting and determining the dynamic magnification factor. Materials and methods. The study is based on finite element method (FEM). Main results. As a result of numerical analysis, the magnification factors of ice loads acting on the propeller shaft when vessel moves in an ice field up to 4 m thick are investigated. Conclusion. The research results can be used to calculate the fatigue strength of the icebreakers and ice-going vessels shaftlines.

Shaking Table Test Study on Seismic Performance of Hollow Rectangular Piers

To study the seismic performance of hollow reinforced concrete piers under dynamic loads, nine hollow pier specimens with different stirrup ratios, reinforcement ratios, and axial compression ratios are designed and manufactured. The El Centro wave, Taft wave, and artificial Lanzhou wave are selected as seismic excitation for the shaking table test. The effects of the reinforcement ratio, stirrup ratio, and axial compression ratio on the failure mode, period, damping, acceleration and displacement response, dynamic magnification factor, ductility, and energy dissipation of specimens under different working conditions are studied. The results show that all the nine reinforced concrete piers have good seismic performance. Subjected to ground motion excitation, horizontal through cracks appeared on the pier surface. With the increase of ground motion excitation, the period of piers increases but the maximum period does not exceed 0.62 s, and the damping ratio increases as well and ranges from 0.02 to 0.064. With the increase of the ground motion excitation, the acceleration response of pier specimens increases, the dynamic magnification factor decreases, the displacement ductility coefficient decreases, and the energy dissipation of the specimens increases. The reinforcement ratio, stirrup ratio, and axial compression ratio have different effects on the above parameters. The test results can provide reference for seismic design of hollow rectangular piers and have certain engineering significance and value.

Research of Seismic Effect for Light Steel Structure with Added Stories

Light steel structure with added stories is a economic and effective method of strengthening design for existing buildings, and it is promoted and applied widely. But it still has some problems about computing of seismic action effect. The computing is not simply in accordance with the base shear method. The value of dynamic magnification factor which was counted as ß needs further research. In this paper, the value of is 2 on the basis of theoretical analysis and calculation example. The safety factor of the value is higher, and the design with the ß is more economic and reasonable.

Study on the Characters of Seismic Response Spectra Based on China Financial Information Mansion

Rare study is done on floor response spectrum of super-high rise building, but it is an important condition for the seismic response analysis of floor subsidiary structure. Therefore, based on the early calculation model of China Financial Information Mansion, the floor response spectrum is calculated under different input ground motion. The floor and ground response spectrum is compared with each other from the seismic coefficient, dynamic amplification coefficient, characteristic period and the form of response spectrum. The results shows that: the floor seismic coefficient and the magnification coefficient are greater or smaller than the ground ones, the biggest difference of which is nearly 1 times; all the floor character period are greater than the ground ones, the biggest difference of which is over 60%; there are obvious differences between the floor and ground dynamic magnification factor spectra form under some conditions, of which the second peak of the former one is probably very large, even near to the peak of the first one, while the latter has no such phenomenon. Therefore, during the process of calculating the seismic response of floor subsidiary structure, it is necessary to consider the change of floor seismic coefficient, dynamic magnification factor, characteristic period and spectra form based on the main structure.

Study on Dynamic Behavior of Ancient Timber Structures Roof

The roof model of the palace timber buildings was established according to the construction technology of the Ying-tsao fa-shih. Based on its analysis of dynamic behavior with shaking table test and ANSYS finite element software, the dynamic behavior of structure and its maximal response under different conditions were gotten, and also the dynamic magnification factor of the beams layer and the whole structure were gotten, at last the results got by shaking table test was compared with the numerical simulation. Research shows that the nature frequency of the model is 1.486 Hz which is much bigger than that of the whole structure; the maximal displacement of beam layer gradually increases with the increase of ground motion intensity and the height of structure; the vibration isolation performance of semi-rigid tenon-mortise joints in rare earthquake (400gal) is better than that in moderate earthquake (220gal) and frequent earthquake (110gal); the dynamic magnification factor between layers was about 1, and roof 0.9 or so.

Building Up Suitable Contact Forces in Integrally Shrouded Blade Rows for Reducing Vibration Amplitudes

The beneficial effects of the contact between shrouds are described extensively in recent literature: natural blade frequencies are increased and additional damping is available. Different models are proposed for analyzing its linear and nonlinear behavior, selection of optimum contact forces are proposed for reducing vibration amplitudes to a minimum. Results from different non linear analyses that use different models all based generally on a reduced modal model of the blade row and on the harmonic balance approach for modeling the non linear contact forces, are sometimes contradictory: some claim e.g. that increasing excitation amplitude leads to a reduction of the dynamic magnification factor (due to friction damping increase) some other claim the opposite. The contribution to this topic of the present paper is the analysis of the effect of a “contact shim” which can be inserted in a cavity between adjacent shrouds. The shim generates suitable contact forces between the shrouds of the blades of a row, which without shim would vibrate as free standing blades.