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Vol. 4 Issue 2

Archives Journal Construction Materials and Products Vol. 4 Issue 2

DRUCKER-PRAGER MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

https://doi.org/10.34031/2618-7183-2021-4-2-5-11
 5-11 p.
Abstract
Problem of developing methods for protecting buildings and structures from the vibrations transmitted to them from the soil under the action of seismic effects is extremely important to date. One of these modern methods is seismic pads. The purpose of this work was to study the effectiveness of adding a pad of granular metamaterials under the foundation of the building to decrease influence of seismic shear waves. The Finite Element Analysis of Mohr-Coulomb models was used to achieve this goal. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamaterials. The values of five variables that affect the mechanical properties of these metamaterials were analyzed (density – cohesion – internal friction angle – Young's modulus – Poisson's ratio) for two different pad thicknesses. The dynamic analysis performed using the software package Abaqus/CAE showed the effectiveness of the granular metamaterials in their ability to significantly reduce magnitudes of displacements, velocities and accelerations in the building compared to the same values in the absence of these metamaterials. The analysis also revealed that among the studied variables, the cohesion is the parameter most influencing the effectiveness of metamaterials in their ability to dissipate seismic waves, while no significant effect was observed for the other parameters.
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AN EFFECTIVE WAY TO RECYCLE 3D PRINTING CONCRETE SCRAP

https://doi.org/10.34031/2618-7183-2021-4-2-12-18
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 12-18 p.
Abstract
The article proposes a rational method for processing 3D printing concrete scrap using vibration equipment, which allows obtaining a multicomponent building material with minimal electricity consumption. As a criterion for the degree of grinding of concrete scrap, it is proposed to use the specific surface area of the finely dispersed part of concrete scrap, which should correspond to 400-500 m2/kg. The possibility of reusing the resulting product instead of the traditional fine aggregate of quartz sand is shown. It was found that the concrete scrap without the addition of Portland cement hardens, reaching up to 48% of the compressive strength of the control samples by 28 days. When 10% of the binder CEM I 42.5 N was added to the concrete scrap processing product, the compressive strength of fine-grained concrete increased by 106.6%, and 20% of Portland cement - by 112.2 %, compared to the strength of control samples of a similar composition on traditional quartz sand after 28 days of hardening. It is noted that this is primarily due to the weak contact zone of quartz sand and the cement matrix of concrete. The use of the product of processing concrete scrap allows obtaining building composites based on it with the complete exclusion of natural raw materials.
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WORLD EXPERIENCE IN THE CONSTRUCTION OF GRAVITY DAMS FROM A PARTICULARLY LEAN CONCRETE MIX

https://doi.org/10.34031/2618-7183-2021-4-2-19-28
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 19-28 p.
Abstract
The article discusses the main aspects of the construction of dams with a symmetrical profile from the material "solid embankment" or other names ("lean" concrete, cemented "sand and gravel mixture" CSG). The design of typical profiles of dams of implemented projects is considered, and information regarding the characteristics and methods of production of this material is provided. The main properties of this material and the principle of its preparation are considered. The work in this area of engineers from Russia, Japan, Iran, Korea, China, and Turkey is analyzed. These dam structures are characterized by high reliability and efficiency, but also, most importantly, by a much higher adaptability or high speed of construction, which is little dependent on local natural factors than traditional rolled concrete dams.
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NONLINEAR TRANSVERSE VIBRATIONS OF COMPOSITE RODS UNDER THE ACTION OF A STATICALLY APPLIED TRANSVERSE LOAD

https://doi.org/10.34031/2618-7183-2021-4-2-29-37
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 29-37 p.
Abstract
Nonlinear transverse vibrations of composite rods pre-loaded with lagging arranged symmetrically on both sides of the axis of the composite rod under the action of a statically applied transverse load are investigated. The cases of attaching the lagging only to the ends of the composite rod, as well as when the laggings are continuously attached to the composite rod along its entire length, are considered. The results of the study of nonlinear transverse vibrations of composite rods under the action of a statically applied transverse load are presented. When conducting studies of transverse vibrations of composite rods, solutions of differential equations of vibration of prestressed through beams and stiffening cores of high-rise buildings are obtained. The obtained differential equations of vibration of composite rods allow us to determine the dynamic characteristics of prestressed through beams under various linear and boundary conditions. A method for composing differential equations of free and forced oscillations of prestressed through beams and stiffening cores of high-rise buildings and solving differential equations under various linear and nonlinear boundary conditions is developed.
Expressions are given for determining the longitudinal forces and torques at the ends of the rod at any location of the lagging from the axis and at any different stiffness of the lagging.
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