Experimental Investigation on Strength and Behavior of PSC Fiber Reinforced Beams with GGBS

The Concrete is one of the most important products which are efficiently and effectively used in the field of construction. The usage of natural aggregates in the process of production of concrete was high which lead to huge deficiency of availability of the natural aggregates. At the same time production of cements leads to more environmental pollution. Therefore, the production of concrete was altered by vast usage of admixtures and replacements for natural aggregates. In this paper M60 grade concrete is prepared by using GGBS as a partial replacement of cement which is a good strength building mineral admixture, the steel fibers were also introduced in the concrete to improve the strength parameter and for ease of work with concrete and addition of AUROMIX – 400 which is provided by FOSROC chemicals Bengaluru as super plasticizers. The concrete specimens like Cubes and Cylinders were casted and allowed to curing over a nominal curing period of 7, 14 and 28 days to know the basic mechanical properties of the concrete with the above replacements and at the same time RCC beams were also casted and cured, then post tensioned to know the flexural details of this special concrete.

Rheological Relaxation of OSB Beams Reinforced with CFRP Composites

An experimental and analytical approach to the relaxation problem of wood-based materials—OSB (Oriented Strand Boards—pressed wood-based composite panels) beams, including beams with CFRP (Carbon fiber reinforced polymer) tape composite reinforcement, is presented. It is a relevant engineering and scientific problem due to the fact that wood and wood-based materials, as well as composite reinforcements, are widely used in building constructions. Their rheological properties are very important and complicated to estimate. A 10 day long relaxation test of thick OSB beams without reinforcement and with CFRP tape was performed. A four-point bending test with five different bending levels was performed, during which the reduction of the loading force was measured. A five-parameter rheological model was used to describe the rheology of the beams. The equations of this model were calculated with the use of Laplace transform, whereas the values of the parameters were calculated based on the experimental relaxation curves. A high correlation between experimental and theoretical results was obtained. A beam reinforced with CFRP tape was treated as a system with a viscoelastic element (OSB) and an elastic element (CFRP), joined together without the possibility of slipping. The equations of the mathematical model were calculated based on the assumptions of the linear theory of viscoelasticity and the convolution integral. A good correlation between experimental and theoretical results was obtained. A significant redistribution of stresses was observed during the relaxation of the reinforced beam. The reinforced beams show a higher stiffness of approximately 63% and carry proportionally higher loads than unreinforced beams at the same deflection values.

Behavior of Non-Shear-Strengthened UHPC Beams under Flexural Loading: Influence of Reinforcement Percentage

In the present work, the structural responses of 12 UHPC beams to four-point loading conditions were experimentally and analytically studied. The inclusion of a fibrous system in the UHPC material increased its compressive and flexural strengths by 31.5% and 237.8%, respectively. Improved safety could be obtained by optimizing the tensile reinforcement ratio (ρ) for a UHPC beam. The slope of the moment–curvature before and after steel yielding was almost typical for all beams due to the inclusion of a hybrid fibrous system in the UHPC. Moreover, we concluded that as ρ increases, the deflection ductility exponentially increases. The cracking response of the UHPC beams demonstrated that increasing ρ notably decreases the crack opening width of the UHPC beams at the same service loading. The cracking pattern the beams showed that increasing the bar reinforcement percentages notably enhanced their initial stiffness and deformability. Moreover, the flexural cracks were the main cause of failure for all beams; however, flexure shear cracks were observed in moderately reinforced beams. The prediction efficiency of the proposed analytical model was established by performing a comparative study on the experimental and analytical ultimate moment capacity of the UHPC beams. For all beams, the percentage of the mean calculated moment capacity to the experimentally observed capacity approached 100%.

Methods of Calculation the Increased Reinforced Concrete Elements by Carrying Capacity of Slope Sections

Reinforcement bending reinforced concrete structures by increasing the cross section and assessing the load-bearing capacity of the inclined section such elements is an urgent problem, as not yet accumulated adequate research data on the stress-strain state such structures in the span, which works on shear and shear bending moment and transverse force. Analyzing the development theories calculation reinforced concrete elements inclined to the longitudinal axis, we can identify many areas, the main approach of which was based on the calculation using the bases of material resistance, and the use of empirical dependencies. Theoretical approaches calculation the European construction magazine RILEM TC, SNiP 2.03.01.-84* are considered, DBN B.2.6-98 2009 (Eurocode 2), US ACI 318-19. Experimental studies reinforced concrete elements to determine the load-bearing capacity inclined sections were performed on the basis of 5 samples reinforced concrete beams, 14 reinforced samples of reinforced concrete and shotcrete a total of 19 pieces in four series. Beams were made of concrete in each series fck = 19.08 MPa; fck = 27.74 MPa; fck = 20.48 MPa; fck = 20.48 MPa, respectively, reinforced samples with concrete fck = 17.95 MPa; fck = 19.5 MPa (shotcrete fck = 31.00 MPa); shotcrete fck = 19.9 MPa; fck = 19.9 MPa. Also for the manufacture and reinforcement beams used flat and U-shaped frames with working longitudinal reinforcement Ø22, Ø16, Ø12, Ø10, Ø6 A400C, and transverse reinforcement Ø6 A240C (step 120 mm). Reinforcement inclined sections of the experimental beams was performed on one, two or three sides, depending on the variant of the sample and the type of frame flat or U-shaped. Investigations of beams were performed according to the static scheme - a beam on two supports, span L=2100 mm. Deformations of concrete and reinforcement in the samples when determining the bearing capacity of inclined sections were measured using microindicators of the clock type, strain gauges. According to the results theoretical and experimental studies the bearing capacity inclined sections to the longitudinal axis, we can see a significant reassessment between the theoretical values inclined sections according to the new DBN B.2.6.-98: 2009 (Eurocode 2) over the actual results obtained during testing samples 53-67% for conventional beams, and 27-50% for reinforced beams. The results US regulations ACI 318-19 showed convergence of results in the range of 2-9% for samples without reinforcement and 1-7% for samples with reinforcement, but the values show the excess of experimental data over theoretical, indicating the impossibility of accurately determining the actual final bearing capacity. The results the calculation obtained by the method of SNiP 2.03.01-84*, both unreinforced and reinforced beams has a satisfactory agreement with the experimental values in the range of 6-10%.

Flexural Strength Design of Hybrid FRP-Steel Reinforced Concrete Beams

Through proper arranging of a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and steel bars in the tensile region of the beam, the advantages of both FRP and steel materials can be sufficiently exploited to enhance the flexural capacity and ductility of a concrete beam. In this paper, a methodology for the flexural strength design of hybrid FRP-steel reinforced concrete (RC) beams is proposed. Firstly, based on the mechanical features of reinforcement and concrete and according to the latest codified provisions of longitudinal reinforcement conditions to ensure ductility level, the design-oriented allowable ranges of reinforcement ratio corresponding to three common flexural failure modes are specified. Subsequently, the calculation approach of nominal flexural strength of hybrid FRP-steel RC beams is established following the fundamental principles of equilibrium and compatibility. In addition to the common moderately-reinforced beams, the proposed general calculation approach is also applicable to lightly-reinforced beams and heavily-reinforced beams, which are widely used but rarely studied. Furthermore, the calculation process is properly simplified and the calculation accuracy is validated by the experimental results of hybrid FRP-steel RC beams in the literature. Finally, with the ductility analysis, a novel strength reduction factor represented by net tensile steel strain and reinforcement ratio is proposed for hybrid FRP-steel RC beams.

Evaluation of Effective Polymer Fiber Length on Energy Absorption Capacity of Reinforced Beams by EBR and NSM Methods

This study presents a comparison of two methods used for retrofitting Reinforced Concrete (RC) beams, namely, the Externally Bonded Reinforcement (EBR) and the Near-Surface Mounting (NSM) methods. A parametric analysis was carried out using variables such as the retrofitted, the retrofitting method (EBR and NSM), and the thickness of the Carbon Fiber-Reinforced Polymer (CFRP) sheets. To achieve this goal, the finite element method and ABAQUS software were employed. An un-retrofitted beam was also simulated as the control specimen for comparison. Beam responses were compared through load–displacement and energy absorption capacity diagrams. Results show that the higher energy absorption capacity in all CFRP-retrofitted RC beams, which was 1.69–5.54 times higher than in un-retrofitted beams. In the case where half of the beam was reinforced using CFRP sheets, the entire beam assembly and the CFRP sheet contributed to load-bearing, thus delaying crack nucleation in the beam and increasing its energy absorption capacity. As a result, the energy absorption capacity of the beam, in this case, was less than that obtained in the previous one where half the span of the beam was retrofitted.