Evaluation of the security of the calculation resultsof the load-bearing capacity for the normal cross-section of eccentrically compressed reinforced concrete elements using a nonlinear deformation model under the action of freezing and thawing cycles

As a result of numerical modeling using the probabilistic method, there has been estimated the security of the results of calculating the load-bearing capacity of eccentrically compressed reinforced concrete elements with symmetrical reinforcement along the normal cross-section, taking into account the effects of freezing and thawing cycles (FTC). The distributions of the strength and deformation concrete characteristics used in the probabilistic calculation are formed on the basis of the results of experimental studies. It is shown that the security of the results of calculations of the load-bearing capacity under eccentrical compression according to the nonlinear deformation model in accordance with the current norms depends on the eccentricity of the longitudinal force and the reinforcement center. The author has substantiated that the decrease in the load-bearing capacity for the normal cross-section regarding the studied elements under the action of the FTC is maximal at small eccentricities and not significant at large eccentricities of the longitudinal force, and it depends on the percentage of longitudinal reinforcement.

Investigation of the bearing capacity of reinforced concrete beams strengthened with reinforced concrete ring under load

Bearing capacity of normal cross section of bending concrete elements reinforced with reinforced concrete ring under load was investigated. Experimental researches of 4 sets of beams with the total number of 16 units were carried out. The results of changes of stress-strain state settings depending on the load level, additional reinforcement, influence of limit level load were analyzed. The three characteristic stages of stress-strain state of reinforced concrete beams strengthened with reinforced concrete ring were defined. Results of experimental investigations of bearing capacity of normal cross section of strengthened beams with reinforced concrete ring under load were presented. Enhancing effect was calculated. According to the results of researches of strengthened beams plots of strain of working armature depending on current bending moment were constructed.

Thermal Quenching of Photoconductivity and the Sign of Photocarriers in Doped a-Si:H

ABSTRACTThermal quenching (TQ) of photoconductivity σp occurs when the demarkation level of minority carriers passes through recombination centers having small capture cross section for majority carriers compared to other centers present but normal cross section for minority carriers. The photoconductivity becomes superlinear with light intensity at the temperature of maximum TQ. We discovered TQ not only in n-type but also p-type a-Si:H. This cannot happen with the same centers unless the sign of the majority carriers changes. We present evidence that in p-type and undoped films majority carriers are electrons at T below TQ and holes above TQ. The nature of these special centers will be discussed.