scholarly journals STUDY OF SPATIAL PROBLEMS OF DYNAMIC STABILITY OF REINFORCED CONCRETE FRAMES

2021 ◽  
pp. 62-70
Author(s):  
V.М. Fomin ◽  
◽  
І.P. Fomina ◽  
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Stability ◽  
Degrees Of Freedom ◽  
Dynamic Instability ◽  
Practical Importance ◽  
Harmful Effect ◽  
Spatial Problem ◽  
Concrete Frames ◽  
Destructive Effect ◽  
Reinforced Concrete Frames

Abstract. The article proposes a method for constructing areas of dynamic instability of reinforced concrete frames in the space of parameters (frequency and amplitude) of seismic and operational dynamic impacts that cause the appearance of longitudinal forces in the bars of structures, which periodically change in time and lead to an unlimited increase in amplitudes of transverse vibrations when the values of these parameters are in the areas of instability. The proposed method is demonstrated by a specific example, which considers the spatial problem of dynamic stability of a П-shaped frame with two concentrated masses located on it, which are under the action of vertical periodic forces. These forces create periodic longitudinal forces in the vertical rods of the frame. Areas of dynamic instability of the frame are constructed. From the point of view of human activity, fluctuations can be both beneficial and harmful. We can observe vibrations of various buildings, structures, bridges, which cause additional stresses and deformations of these structures, have a harmful effect on their safe functioning. Too intense fluctuations lead to serious consequences. This leads to the destruction of individual elements of the structure and, as a result, to accidents. The most destructive effect of vibrations is observed during earthquakes and explosions. The study of vibrations is of great practical importance. This avoids the unwanted effects of fluctuations by limiting their level. Only on the basis of a deep study of various types of vibrations can important practical problems of the dynamics of structures be solved. Solving dynamics problems is a complex problem. In contrast to static calculation, when studying oscillations, one has to take into account an additional factor – time. The dynamic design of structures provides them with bearing capacity under the combined action of static and dynamic loads. A construction will be considered as a system with an infinite number of elementary masses distributed over it with an infinitely large number of dynamic degrees of freedom.

scholarly journals SPATIAL PROBLEMS OF DYNAMIC STABILITY OF FRAME STRUCTURES

2021 ◽  
Vol 3 (2) ◽  
pp. 40-51
Author(s):  
V. Fomin ◽  
◽  
I. Fomina ◽  
Keyword(s):  
Dynamic Stability ◽  
Dynamic Instability ◽  
Difficult Problem ◽  
Frame Structures ◽  
Spatial Problem ◽  
Deformation Method ◽  
Destructive Effect ◽  
Modified Method ◽  
Unlimited Growth ◽  
Transverse Oscillations

Periodic longitudinal forces in structural elements caused by operational or seismic influences, at certain values of the parameters of these forces can cause the occurrence and growing of transverse oscillations of these elements. This phenomenon is called parametric resonance or loss of dynamic stability. In the works of N. M. Belyaev, N. M. Krylov, М. М. Bogolyubov, E. Mettler, V. N. Chelomey, V. V. Bolotin flat problems of dynamic stability of frame structures were investigated. In this paper the modified Bolotin’s method, proposed to solve flat problems of dynamic stability of frames, is used. Instead of the deformation method used by V. V. Bolotin to construct analytical expressions of deflections of frame rods, in the modified method the numerical-analytical method of boundary elements is used. The article proposes a method for constructing domains of dynamic instability of frames in the space of parameters (frequency and amplitude) of seismic and operational dynamic influences that cause longitudinal forces in the rods, which periodically change over time and lead to unlimited growth of transverse oscillations amplitudes in the domains of instability. The proposed method is demonstrated in example, which considers the spatial problem of dynamic stability of a П-shaped frame with two concentrated masses located on it, which are under the action of vertical periodic forces. These forces create periodic longitudinal forces in the vertical rods of the frame. Areas of dynamic instability of the frame were constructed. Taking into account the destructive effect of oscillations is important for practical application. The most dangerous destructive effect of oscillations is observed in earthquakes and explosions. The study of this action makes it possible to avoid undesirable consequences of oscillations by limiting their level and to solve important practical problems of the dynamics of structures. Solving dynamics problems is a difficult problem. Dynamic calculation of structures provides their bearing capacity under the combined action of static and dynamic loads.

EXPERIMENTAL LIFE STUDIES OF REINFORCED CONCRETE FRAMES WITH GIRDERS REINFORCED BY INDIRECT REINFORCEMENT

2020 ◽  
Vol 87 (1) ◽  
pp. 92-100 ◽  
Author(s):  
N.V. FEDOROVA ◽  
◽  
FAN DINH GUOK ◽  
NGUYEN THI CHANG ◽  
◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Concrete Frames ◽  
Reinforced Concrete Frames

scholarly journals Investigation of Diagonal Strut Actions in Masonry-Infilled Reinforced Concrete Frames

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Seung-Jae Lee ◽  
Tae-Sung Eom ◽  
Eunjong Yu
Keyword(s):  
Reinforced Concrete ◽  
Failure Mode ◽  
Yield Criterion ◽  
Friction Angle ◽  
Concrete Frames ◽  
Element Analysis ◽  
Reinforced Concrete Frames ◽  
Infilled Frames ◽  
Masonry Infills ◽  
Push Down

AbstractThis study analytically investigated the behavior of reinforced concrete frames with masonry infills. For the analysis, VecTor2, a nonlinear finite element analysis program that implements the Modified Compression Field Theory and Disturbed Stress Field Model, was used. To account for the slip behavior at the mortar joints in the masonry element, the hyperbolic Mohr–Coulomb yield criterion, defined as a function of cohesion and friction angle, was used. The analysis results showed that the lateral resistance and failure mode of the infilled frames were significantly affected by the thickness of the masonry infill, cohesion on the mortar joint–brick interface, and poor mortar filling (or gap) on the masonry boundary under the beam. Diagonal strut actions developed along two or three load paths on the mortar infill, including the backstay actions near the tension column and push-down actions near the compression columns. Such backstay and push-down actions increased the axial and shear forces of columns, and ultimately affect the strength, ductility, and failure mode of the infilled frames.

scholarly journals Experimental testing of medium scale GFRP reinforced concrete frames

2019 ◽  
Vol 289 ◽  
pp. 04004
Author(s):  
George Hopartean ◽  
Ted Donchev ◽  
Diana Petkova ◽  
Costas Georgopoulos ◽  
Mukesh Limbachiya ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Testing ◽  
Control Sample ◽  
Concrete Frames ◽  
Reinforced Concrete Frames ◽  
Reinforced Polymers ◽  
Rc Structures ◽  
Gfrp Bars ◽  
Glass Frp ◽  
Reversed Cyclic

Fibre reinforced polymers (FRP) have been used as strengthening for existing RC structures for many decades. Lately, there has been a lot of interest in using FRP as internal reinforcement in beams, slabs and columns. One potential area of application could be reinforced concrete frames internally reinforced with GFRP bars. With limited research in this direction, the objective of this publication is to assess the behaviour of glass FRP (GFRP) reinforced concrete frames under reversed cyclic lateral in plane loading and to analyse the seismic performances of such elements. For the purpose of this paper, experimental testing of two 1/3 scaled down frames is conducted in displacement-controlled mode with the loading history according to ACI 374.1-05. The control sample is reinforced with conventional steel reinforcement and the results obtained are compared with the sample reinforced with GFRP bars. In summary, observations on the sample behaviour at specified drift ratio such as load-displacement behaviour, envelope curves and energy dissipation are presented.

Sign in / Sign up

Export Citation Format

Share Document