Effect of the Reinforced Plastic Clamp Fitting on the Bending Strength of the Spruce T-Type Loose Tenon Joints

This article presents the bending strength and flexural properties of the glued T-type spruce loose tenon construction joints with and without reinforced plastic clamp fitting. Construction joints are designed according to Eurocode 5. The samples are made from European spruce (Picea abies Karst.) C24 class construction material with relative wood moisture 18% and relative wood density 410 kg/m3. Samples are assembled with water/high temperature resistant polyurethane adhesive and polyvinyl acetate dispersion adhesive. The total number of samples is 48. The sample width is 95mm and thickness is 45mm. Samples were subjected to moisture, weight controls and 48h stored in the climate chamber before practical bending load test. T-type loose tenon joint construction samples with reinforced plastic clamp fittings glued with polyurethane adhesive under bending load are 2.6% stronger and 13.8% less flexural then without reinforced plastic clamp fittings. T-type loose tenon joint construction samples with reinforced plastic clamp fittings glued with polyvinyl acetate dispersion adhesive under bending load are 9.7% weaker and 20% less flexural then without reinforced plastic clamp fittings. The accuracy of the developed bending strength, deformability and elasticity modulus of the examined construction joints was verified positively by experimental studies.

Experimental studies of the stress-strain state of reinforced concrete structures strengthened by prestressed basalt-composite rebar

Relevance. In recent years, composite materials have become widespread in the construction of reinforced concrete structures for industrial, civil and transport structures. It is proposed to strengthen the reinforced concrete structures of hydraulic structures with prestressed basalt composite rebar. It took an experimental and theoretical substantiation of technical solutions to strengthen the reinforced concrete structures of hydraulic structures with prestressed basalt composite reinforcement. The aim of the work was to carry out a set of experimental and theoretical studies of the stress-strain state and internal forces in low-reinforced concrete structures of hydraulic structures reinforced with prestressed basalt composite rebar. Methods. Experimental studies of the stress-strain state and internal forces were carried out on the basis of low-reinforced concrete beam-type models with interblock construction joints, harden with prestressed basalt composite reinforcement in the stretched (compressed) zones of the models. Theoretical studies of the stress-strain state and internal forces were carried out on the basis of the theory of reinforced concrete and structural mechanics. Results. As a result of the research carried out on typical low-reinforced concrete structures of hydraulic structures with interblock construction joints, the main stages of the stress-strain state of hydraulic reinforced concrete structures were formulated. Based on the data of experimental and theoretical studies, taking into account the reinforcement with prestressed basalt composite rebar, as well as with prestressed clamps in the shear zone, a method was developed for calculating the strength of low-reinforced hydrotechnical reinforced concrete structures with interblock construction joints.

Comparison of Stress Fields near Longitudinal Construction Joints of Tied and Doweled Sections in Portland Cement Concrete Pavements

In Portland cement concrete (PCC) pavements, tie bars are commonly used at longitudinal construction joints (LCJs) to prevent the lanes from separating. Meanwhile, the increase in multiple lanes due to greater traffic volumes has raised concerns about potential longitudinal cracking; this has led to the use of dowel bars instead of tie bars at LCJs. However, there is a paucity of studies focused on the comparison between the behaviors of concrete pavement based on the restrained conditions provided by tie and dowel bars at LCJs. In this study, we investigated the effects of the placement of tie and dowel bars at LCJs on the potential for longitudinal cracking in response to the increase in concrete stress that may occur when the lanes are tied together in PCC pavements. Field testing verified that the variation in concrete strain was more restrained in the case of a tie bar than a dowel bar, whereas it resulted in higher stress in the concrete element in the tie bar section. However, the use of dowel bars caused more movement in the transverse direction at LCJs as compared with tie bars. Thus, our results indicate that using dowel bars reduces the potential for longitudinal cracking; however, it may increase the potential for lane separation.

Experimental Study on the Influence of Second-Order Effect on Shear Bearing Capacity of Frame Columns with Cracks under Different Axial Compression Ratios

The construction joint is the weak part of the structure, and the P-δ effect is mostly ignored when considering the second-order effect, so it is necessary to study the influence of second-order effect on frame columns. Based on the above considerations, under different axial compression ratios, the mechanical properties of the construction joints of the frame columns with construction joints and the cast-in-situ frame columns were studied by low cycle repeated load testsand analyzed the influence of the second-order effect on the shear capacity of frame columns with joints. The test results indicate that the existence of construction joints reduces the shear-bearing capacity of the specimens, and the second-order effect has a greater impact on the columns with joints under the same axial compression ratio, and the shear capacity decreases more. With the increase of the axial compression ratio, the second-order effect will be weakened on the frame column with seam, but when the axial compression ratio exceeds a certain limit, the second-order effect will be increased.

Analysis of the Influence of Different Construction Joints on the Ductility of Cast-in-Place Frame Structure

This article through to the two common cast-in-situ frame structure (casting of a whole, with a construction joint) and 6 root not construction joints under axial pressure ratio through concrete columns of different processing low reversed cyclic loading experiment, study their experimental phenomena, hysteresis curves, displacement ductility, stiffness degradation, thus draw the conclusion: 1, the existence of the construction joint can lead to the decline of ductility of frame structure. 2. When the test axial pressure is relatively low, the presence or absence of construction joints and different treatment methods will obviously affect the ductility of the cast-in-place frame structure. 3. When the test axial pressure is relatively high, the presence or absence of construction joints and different treatment methods will not have a significant impact on the ductility of the cast-in-place frame structure.

STRENGTH OF LOW-REINFORCED CONCRETE STRUCTURES WITH THE INTERBLOCK CONSTRUCTION JOINTS REINFORCED BY PRESTRESSED BASALT-COMPOSITE BARS

Many slightly reinforced concrete structures of operating hydraulic structures need strengthening. Traditional methods of strengthening (by reinforced concrete, metal structures, etc.) have significant disadvantages. A method of strengthening by external reinforcement systems based on carbon fiber which is effective in cases where there is an access to the tension zone of the reinforced structures begins to spread. The authors propose to strengthen slightly reinforced concrete structures of the operated hydraulic structures with pre-stressed basalt composite reinforcement placed in the pre-drilled holes in the concrete of the reinforced structures. To substantiate the proposed technical solutions there was carried out a set of experimental studies of characteristic slightly reinforced concrete structures of hydraulic facilities (including those with inter-block construction joints) reinforced with pre-stressed basalt composite reinforcement. The results of experimental studies have shown the effectiveness of strengthening low-reinforced concrete structures of operating hydraulic facilities with inter block construction joints by means of pre-stressed: longitudinal basalt composite reinforcement and transverse reinforcement.

Experimental studies of reinforced concrete structures of hydraulic structures strengthened with prestressed transverse reinforcement

Relevance. When repairing hydraulic structures, it is often necessary to face the task of strengthening them. Among the methods of strengthening retaining structures, the most interesting are those that allow to immediately include reinforcement elements in joint work with the structure and carry out work without removing the backfill soil from the rear edge. When choosing repair materials, attention should be paid to corrosion-resistant composite materials, the use of which in hydraulic engineering is not yet standardized, but the scope of their application is expanding every year. The main aim of experimental research is to strengthen the reinforced concrete structures of hydraulic structures, including those with interblock construction joints and transverse cracks, using prestressed transverse reinforcement. Methods. The investigations were carried out on a reinforced concrete model of a beam type reinforced with prestressed transverse reinforcement in the zone of inclined cracks formation. The model was made taking into account the typical tasks encountered during the repair of long-term operating retaining hydraulic structures with open seams and cracks, insufficient transverse reinforcement, low reinforcement coefficient, and initial deflection. Results. The task of strengthening a special reinforced concrete model using prestressed transverse reinforcement was realized. Experimental data were obtained on the nature of deformation and destruction, the opening of interblock construction joints and cracks, and the stresses in the reinforcement. Recommendations are given for strengthening the operated low-reinforced concrete structures of hydraulic structures with interblock construction joints with prestressed reinforcement.