The article includes the method of simulating of seismic impact to structures by system of vibration directional machines. Essence of the method concludes in reproducing of powerful vibrating machines in the different stores of the structure where oscillation characteristics are selected based on the spectrum of acceleration of the earthquake and so that the values of the inertial forces arising in the structure during their operation are equal to the true values of seismic forces which arise during the same earthquake. The offered method gives an opportunity for modeling of the stress-strain stain of the structure is taking place during the earthquakes without moving its foundation.

Abstract. The experimental research of the form of behavior of structures and constructions under the effect of seismic load is of big practical interest. The most reliable way of experimental research of seismic effect is the instrumental observation of the form of behavior of an actual structure, construction or their model during a major earthquake. The result of experimental research of the possibility of simulating two-component seismic load with the utilization of systems of directional vibration machines is given in this work. The principle of the method of simulating the seismic load is that for vibration excitation in two mutualperpendicular directions on the floors of the 9,6 and 3 floors of the model ( in the places of onset of maximal shifting for the according mode) 6 directional oscillating machines were installed. The first three oscillating machines were exciting vibrations in the transverse direction and the other three in the longitudinal direction of the building (since the first three modes of vibrations are quintessential for multistory buildings). Each of the vibrators excited oscillations in a specific mode. It is demonstrated that with simultaneous effect of machines in two mutual-perpendicular directions, the duty cycle of the vibrations does not change. This allows for simulating the seismic load on the building in each direction separately.

The article presents a method to reproduce seismic impacts on structures according to an accelerogram of an earthquake. Three powerful vibrating machines have to be installed on different floors of the structure, where oscillation characteristics are selected based on the spectrum of acceleration of the earthquake and so that the values of the inertial forces arising in the structure during their operation are equal to the true values of seismic forces which arise during the same earthquake. Key words: vibrating machine, eccentric, accelerogram, structure, model.

The urgent task which is addressed in this work is the development of methods for determining the frequencies and forms of vibrations, as well as dynamic reactions of thin slabs with various support systems, including those supported on point supports. The aim of the work is to develop experimental methods for determining the frequencies and forms of natural oscillations of slabs with holes and thin point-supported square solid ones. In this work, the frequencies of square slabs with free edges resting on point supports are determined; the dependences of the vibration frequencies of slabs from the coordinates of point supports and the dimensions of symmetrically placed holes; the arrangement of point supports, wherein the basic frequency of free vibrations of the slab is maximum; the frequencies, shapes, and decrements of vibrations of square slabs supported on four point supports were determined experimentally, as well as the influence of the presence of holes and the degree of pinching of the supports on the dynamic characteristics of these slabs. The article deals with the method and analysis of results of experimental investigations of dynamic characteristics of square solid slabs with holes. Comparison of experimental and theoretical values of frequencies of natural oscillations of slabs showed their good similarity. The results of this work can be applied to dynamic and seismic calculations of point-supported square slabs.