Visnyk LNAU: Architecture and Farm Building 2017 №18: 19-28
MODELING OF THE STRESSED-DEFORMED CONDITION OF REINFORCED CONCRETE BEAMS IN SIMULTANEOUS INFLUENCE OF AGGRESSIVE ENVIRONMENT AND LOADING
R. Shmyh, candidate of technical sciences, associate professor
Lviv National Agrarian University
The reinforced concrete constructions of buildings and structures are often used in complex production conditions (under high positive or low negative temperatures, high humidity, under a complex aggressive environment, etc.).
The intense action of the aggressive environment contributes to the emergence and development of the process of corrosion of concrete and reinforcing steel reinforced concrete structures. And this, in turn, affects the reduction of the bearing capacity of the reinforced concrete structure, the increase of deflections, operational suitability.
Corrosive processes actively change the shape of the cross section of the reinforced concrete element, affect the physical and mechanical characteristics of the corrosive outer layers of the reinforced concrete element.
The development of a numerical computer model for calculating reinforced concrete beams subject to aggressive corrosion effects will provide sufficiently complete information on the stress-strain state of reinforced concrete beam construction at all stages of operation, from the beginning of the application of external load, the emergence and development of normal and inclined cracks, prior to the deteriorating state of the construction and on the very stage of building structure destruction.
At the basis of the proposed calculation model for determining the stress-strain state of reinforced concrete beams with corrosion damage lies the hypothesis of plane cross sections and a sequential approximation algorithm that allows taking into account the physical nonlinearity of concrete and reinforcement.
The reinforced concrete beam in the calculation model is presented in a discrete form. Concrete is described by rectangular flat elements, reinforcing rods by linear core elements. The beam is divided into sections by length and layers at a section height.
Thus, it has been previously stipulated that the stress-strain state formed in the elementary regions is the same. The number of elementary sections and elementary layers affects the accuracy of the calculation, but is always limited to the available RAM of the PC.
At considerable intensity of loading, and consequently high level of stresses on the side faces of the beam there is an increase in the intensity of corrosion of the concrete, which causes more intensive reduction in the size of the cross-section. Moreover, it has been experimentally discovered that the further we are from the neutral axis of the beam at the height of the cross section, the more this effect occurs. Numerous experimental studies have shown that the cross sections of the reinforced concrete beams took the oval shape.
According to the proposed method for determining the stress-strain state of reinforced concrete beams at the time of the external load and aggressive effects of the environment, the work of the prototypes was simulated at all stages of loading, including destruction. As a result, the distribution of deformations, strains, determining the bearing capacity and deformability of the prototype samples, the day of possible destruction of the structures are established.
reinforced concrete beam, stress-deformed state, hypothesis of plane sections, aggressive environment, corrosion
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