The problem of seismic protection of the bridge for the conditions of Uzbekistan is considered. The bridge is located in an area with estimated seismicity of 9 points. It has massive high supports on a natural foundation and relatively small and light spans. When selecting seismic isolation, this made it possible to use the span structures as a dynamic damper for the support vibrations in the direction along the bridge. Due to the damping effect, it was possible to achieve that the seismic forces in the support in the presence of the superstructure were less than in the free support without the superstructure. At the same time, the rigidity of fastening the superstructure to the support increased in comparison with the rigidity of classical seismic isolation, which facilitated the design of the supporting elements.
Analyzes existing known solutions for dynamic damping oscillations of bridges in earthquakes. Substantiates the impact of errors settings the two-mass systems on the efficiency of dynamic dampers of different masses (small, large and commensurate). Based on the obtained of optimal parameters were built isolines depending reduce the displacement of the main mass of the setting on the stiffness and damping for different masses. The estimates obtained allow to simplify essentially the task of designing seismic devices for bridges.
The paper presents the results of experimental studies on the strength and deformations of lightweight concrete, mortar matrix and hardened cement paste under triaxial compression. Tests on samples were carried out using short-term triaxial proportional σ1 > σ2 = σ3 loading (i.e. axial compression + lateral hydrostatic pressure). During the loading, the ratio of the main stresses (both axial and lateral) was kept constant up to the end of tests. The experimental studies were carried out for different low ratios of σ2/σ1. A theoretical estimation has been discussed to approximate experimental results and prediction of triaxial strength values for different types of lightweight concrete. An estimation of the confining pressure parameter K has been done for the used mode of loading.
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