Improvement of the method of probability evaluation of the failure-free operation of reinforced concrete beams strengthened under load

Pavliv

2021

EEJET

This paper reports the development and verification of a new procedure for formation of a complete stress-strain curve of concrete with a downward region of strain by using a digital image correlation method. A new technique to build spectle patterns on the surface of concrete is described. That makes it possible to accurately enough reproduce the spectle patterns on the surface of concrete and perform a high-quality analysis of strains involving digital image correlation. The advantages of this research technique have been established when predicting the formation of internal cracks in concrete followed by their propagation. In addition, using the digital image correlation methodology makes it possible to obtain strains of the entire studied plane of the sample at each stage of loading. This procedure provides an opportunity to investigate a change in strains and the movement of individual points or areas when studying concrete surfaces. That is a relevant issue as it enables more detailed diagnostics of existing reinforced concrete structures. To check the accuracy of this procedure application, a mechanical gauge with an accuracy of 0.001 mm was additionally installed. 2 high-speed monochrome CCD cameras with different lenses were used in determining concrete strains involving the digital image correlation technique. The deformations were controlled with a period of time every 250 ms. The load was controlled by an additional third camera with a speed of 50 frames/second. The result of the experimental study is the formed full concrete destruction diagram with a downward region of strain. The deviation of the results of strains based on the mechanical gauge with an accuracy of 0.001 mm with a base of 200 mm from those acquired by the digital image correlation procedure was mainly up to 10 %, which confirms the reliability of the results. The results of this work allow a more accurate calculation of reinforced concrete structures in the practice of design, inspection, or reinforcement of existing structures

Section: Introductionsupporting

confidence: 57%

Formation of a complete stress-strain curve of concrete using digital image corellation

Pavliv

2021

EEJET

“…Therefore, the number of controlled random parameters were included in the theory of calculations, namely: strength of materials, geometric cross-sectional parameters, as well as the level of load in the case of structural strengthening. The presence of the load level simulates the real operating conditions of the structure during its strengthening (Khmil et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Mathematical modelling of stress-strain state of steel-concrete beams with combined reinforcement

Selejdak

Bobalo

Production Engineering Archives

et al. 2023

Most of the modern computer software for the building structures‘ calculation is based on mathematical dependencies which make it possible to analyse rather complex stress-strain state of structures subjected to loading. As a rule, the calculation is based on the finite element method and is reduced to the calculation of deformations arising in structures due to the action of external forces with the use of real strain diagrams of materials, σ-ε diagrams for concrete and reinforcement. Modern normative regulations for reinforced concrete structures‘ calculation are also based on the deformation model using material deformation diagrams, which are as close to the real ones, as possible. Therefore, this study was aimed to investigate in more detail the stress-strain state and the physical essence of the processes occurring in reinforced concrete structures with combined reinforcement according to mathematical approaches and regulations of DBN B.2.6-98:2009 and DSTU B. In 2.6-156:2010. Namely, in the research is analysed the combined reinforcement of S245 steel tapes and A1000 rebar, which is used in the production of reinforced concrete elements. The results of mathematical modelling were compared with the calculation results, according to DBN B.2.6-98: 2009 and DSTU B. B 2.6-156:2010, as well as with field experimental data. Therefore, the conclusion could be made, whether it is possible to use this technique with sufficient accuracy to calculate reinforced concrete structures with combined reinforcement.

“…Based on the test results, it is necessary to provide a procedure of theoretical estimationto test the existing one, to provide recommendations for its changes, or to devise a new methodology [5]. In some cases, a new procedure for determining bearing capacity [6] is suggested, while in others -changes or clarifications to acting norms are proposed [7]. Improvement of existing procedures for calculating building structures is the most common practice since this verifies a given technique and introduces the necessary changes [8].…”

Section: Introductionmentioning

confidence: 99%

Development methodology of determinating residual carrying capacity of reinforced concrete beams with damages tensile reinforcement which occurred during loading

Vegera

Vashkevych

et al. 2021

EEJET

This paper reports the improved and verified procedure for calculating reinforced concrete beams affected by damage to stretched reinforcement when loaded. The main results from testing the reinforced concrete beams with damage in the stretched zone in the form of one hole in the reinforcement in the middle of the beam are given. The variable parameter of the study was the level of load resulting in the damage. It acquired values of 0, 30 %, 50 %, 70 % of the bearing capacity of control undamaged samples. Overall, the results of testing 12 samples are given. A new procedure has been proposed for taking into consideration changes in the mechanical characteristics of stretched reinforcement arising from its damage. This makes it possible to more accurately establish the bearing capacity of reinforced concrete bended elements affected by damage to their reinforcement during operation. The analysis of the calculation, compared with experimental quantities, led to a conclusion that the strain model could determine when the bearing capacity of reinforced concrete beams without damage and with damage to working reinforcement is exhausted. Based on the improved algorithm, the principle of using a strain model was proposed to establish when the bearing capacity of damaged samples, taking into consideration the effect of the load level, is exhausted. The theoretical estimation, considering when the bearing capacity is exhausted, showed results that are 3...21 % less than the experimental values, which ensures reliability of calculation of such structures. The proposed calculation provides a new approach to determining the bearing capacity of reinforced concrete beams damaged during operation. That, in turn, makes it possible to more accurately determine the residual bearing capacity of structures and increases the safety of their operation.