Deformability Of Beams Research Articles

Investigation of the strength and deformability of glued wooden beams with lamellas made of thermally damaged (Pinus sylvestris L.) wood based on experimental planning

Investigation of the strength and deformability of glued wooden beams with lamellas made of thermally damaged (Pinus sylvestris L.) wood based on experimental planning

Enhancement of cantilevered RC beams exhibiting inadequate lap spliced reinforcement using sustainable reinforced ECC layers

Designguidelines require an adequate overlap length for reinforcing bars, especially in extended spans of elements constructed from Reinforced Concrete (RC). Insufficient overlap can have adverse effects on key characteristics like bending strength and deformability of RC beams. The potential danger of failure in such elements is a significant concern as is considered a potential threat, and this study addresses it through experimental identification and numerical analysis to be mitigated carefully in this study to enhance the safety and sustainability of buildings to mitigate the risk of failure. The current investigation is centered on investigating the structural behavior of cantilevered RC beams exhibiting inadequate overlap between reinforcing bars in the hogging moment region. These beams have been strengthened through the application of ferrocement layers of Engineered Cementitious Composite (ECC). The experimental study consisted of eleven beams, which were categorized into four groups and subjected to bending loads until they reached failure. The research assessed various factors, such as the casting method (whether cast-in-situ or precast), the installation technique (involving the use of epoxy, or epoxy with anchors), and the length of the ECC layer. This layer was configured to have a length of 30Ø, 40Ø, and 50Ø, with Ø representing the diameter of the reinforcing bars along the zone subjected to hogging moments. According to findings, strengthening of specimens exhibiting insufficient steel overlap through an ferrocement ECC layer exhibited an improved overall structural behavior compared to the defective control beam. The most significant enhancement in both failure mode and load-deflection behavior was observed in beams strengthened through the incorporation of a cast-in-situ ECC layer with anchor bolts. Additionally, augmenting the strengthening length not only increased the initial stiffness of the reinforced beams but also enhanced their energy absorption capacity. Furthermore, the study involved the construction of a numerical simulation employing the Finite Element Method (FEM) simulating the observed behavior in experimentally tested beams. The model's precision was validated through a comparison of its results with the experimental data, revealing a satisfactory level of accuracy.

Influence of Fiber Type on the Performance of Reinforced Concrete Beams Made of Waste Aggregates: Experimental, Numerical, and Cost Analyses

The structural performance of concrete structures requires swelling the bending and shear characteristics of reinforced concrete (RC) beams. The bending characteristics of RC beams consisting of waste granite aggregate (WGA), steel fibers (SF), polypropylene fibers (PF), and glass fibers (GF) are assessed in this research. Twenty-one 2,000 mm×200 mm×250 mm RC beams were cast and tested. WGA was sorted and utilized instead of natural coarse aggregates (NA), with three mass replacement fractions: 0%, 50%, and 100%. Besides, SF, PF, and GF were utilized separately at three fractions of 0%, 0.5%, and 1%. Beams were loaded under a four-point bending arrangement, and the ultimate bending resistance, deformability, stiffness and crack development were recorded and assessed. Also, an evaluation of experimental results and existing design standards in terms of maximum crack width has been carried out. Moreover, a cost-sensitivity examination has been made to analyze the effectiveness of using various fibers in terms of cost. Experiments revealed that the impact of PF on enhancing the load-bearing capability of beams with WGA was greater than that of strengthened with SF and GF. However, the impact of GF on the ultimate deformability of WGA RC beam samples was superior to that of PF and SF. PF has a greater influence on enhancing the flexural capacity of RC beams than SF; nevertheless, SF has a greater influence on deformation. The ductility and deformability of RC beams were substantially enhanced when GF was introduced in specimens made with WGA.

Regression based evaluation of High-Grade RC beams with hybrid confinement

The regression equations developed for projecting the effective factors of high-grade RC beams with hybrid confinement are presented in this study (cellular stirrups and externally bonded GFRP wraps). Six 150 × 250 × 3000 mm RC beams were constructed and tested to see how hybrid confinement affected the strength, deformability, and ductility of high-grade RC beams. To identify the final failure point, the beams were put through a four-point flexure test. Load application has been made easier thanks to a jack and pump setup, and deflections have been measured with 0.01 mm dial gauges. The suggested regression equations accurately predicted the effective components to a respectable degree.

Деформативність та тріщиностійкість пошкоджених балок з базальтопластиковою арматурою, підсилених вуглепластиковим полотном

The aim of this article is to introduce the results of experimental and theoretical studies on the deformability and crack resistance of damaged concrete beams reinforced with basalt-plastic reinforcement and strengthened with carbon-fiber jackets in the support regions. The paper presents the results of studies of the deformability and crack resistance of basalt-concrete beams, brought to the boundary state (ULS) in previous tests, reinforced with external fiber-reinforced plastic (CFRP). These data are presented in the form of experimental statistical relationships of the main parameters of the performance of the prototypes from design factors and levels of low-cycle repeated load. The greatest influence on the deformability of materials and test samples - damaged basalt concrete beams, reinforced with carbon fiber, have: the value of the relative span of the cut (а/h0), then - the class of concrete (C) and, finally, the coefficient of transverse reinforcement ( ) of their supporting areas. The conducted experimental and theoretical studies confirmed the expediency and possibility of using fiber-reinforced plastics (CFRP) for strengthening external structures damaged by force cracks and brought to limit states according to the first (ULS) and second (SLS) groups of reinforced structures according to the established technology.

Порівняльний аналіз несучої здатності дослідних пошкоджених залізобетонних елементів, підсилених металевими обоймами

The paper presents research results and a comparative analysis of the load-bearing deformability and crack resistance of basalt concrete beams brought to the limit state (ULS) in previous tests. The beams were reinforced with prestressed metal clips under high-level static and low-cycle alternating loads. The work performed comparative calculations of reinforced building structures using proprietary methods and existing regulatory methods. A comparison of the experimental and calculated values of the bearing capacity of damaged experimental beam samples showed their unsatisfactory convergence because the well-known regulatory and proprietary methods provide for the calculation of the bearing capacity of damaged reinforced concrete structures along a dangerous inclined crack under the predominant action of transverse force, i.e. the top of a dangerous inclined crack and clamps and vertical elements of external reinforcement. However, experimental and theoretical studies have shown that the destruction of prototype beams with large and medium shear spans under a variable low-cycle load occurs along dangerous inclined through cracks, from the overwhelming action of bending moments, in the longitudinal reinforcement elements of the frame, in the longitudinal tensile reinforcement, as well as transverse beam beams and yield stress cages. That is, the real physical picture of the operation of the system “damaged reinforced concrete beam – prestressed metal reinforcement cage” under alternating transverse load at high levels differs significantly from the physical model of previously existing regulatory and proprietary methods. All existing regulatory and proprietary methods provide for the calculation of the bearing capacity of damaged reinforced concrete structures along a dangerous inclined crack under the predominant action of transverse force, that is, the components of the bearing capacity of inclined sections on concrete above the top of a dangerous inclined crack and clamps and external elements are taken into account. Experimental and theoretical studies have shown that the destruction of prototype beams with large and medium shear spans, under alternating low-cycle loads, occurs along dangerous inclined through cracks from the overwhelming action of bending moments in the longitudinal tensile reinforcement, as well as in the transverse rods of the beam and the cage yield strength.

EFFECTIVENESS OF STRENGTHENING OF REINFORCED CONCRETE BEAMS WITH THE USE OF COMPOSITE MATERIALS

Wide spread of RC structures in construction projects indicates the necessity of their service life prolongation. Perspective possibility to increase strength of RC structures is use of external composite tapes. The article presents theoretical research on the effectiveness of strengthening of RC bended elements with the use of composite tapes. Work also includes comparative analysis on the basis of calculations, according to normative regulations. With the use of developed algorithm parameters of stress-strain state and deformability of RC beams, strengthened with composite tapes were obtained. Study identified, that the most critical parameter was the steel bars` strain and yield point. Interesting finding of the study is the no-linearity of the strength growth of the studied elements with the increase of additional reinforcement amount. Consistent literature review was conducted, which identified the necessity to take into account different external factors and failure mode.

Local use of ECC to simultaneously enhance the shear strength and deformability of RC beams

• A new method that can simultaneously enhance the shear strength and deformability of RC beams was proposed. • The effects of compression-zone material on the variation of V c and v s were evaluated. • Shear deflection and flexural deflection were decoupled. • The mechanisms of how compression-zone material affects the shear strength and deformability were investigated. Existing studies have substantiated that the stress (or strain) states of compression-zone concrete exert significant influence on the performance of shear-critical reinforced concrete (RC) beams. Based on this understanding, the current paper presents a tentative work by replacing the compression-zone concrete with engineered cementitious composite (ECC) to simultaneously enhance the shear strength and deformability of a RC beam. To uncover the reasons behind the enhancements due to the inclusion of ECC, the shear strength contributions from concrete ( V c ) and stirrups ( V s ) were obtained with reasonable accuracy using an innovative methodology. Shear and flexural deformations were decoupled utilizing two methods with the help of the imaging technique. The cracking process, crack width, strain fields, and principal direction evolutions were monitored by a digital image correlation (DIC) system. The test results clearly show that the inclusion of ECC in the compression zone significantly increased both the shear strength and deformability of RC beams. More specifically, the inclusion of ECC changed the crack width and pattern, the variation trends of V c and v s and the deformation proportion. Finally, existing shear deformation models were evaluated, and none of them could predict the shear deformation of beams incorporating ECC due to the high nonlinear feature.

Расчет составных изгибаемых деревянных элементов по деформациям с учетом нелинейной работы связей сдвига

The mathematical model for the calculation of component elements with non-linear-flexible shear connections by deformations is presented. The algorithm is based on the theory of calculation of component rods by A. R. Rzhanitsyn, however, the rigidity of the shear connections is refined at each step for each connection, depending on shear force. It has been established that neglecting the actual nature of the connections deformation introduces a significant error in the assessment of the deformability of component beams with mechanical connections.

Numerical analysis on collapse performance of post-tensioned concrete frames with post-tensioning BFRP bars under an interior-column-removal scenario

Basalt fiber reinforced polymer (BFRP) bars are ideal substitutes for steel reinforcement due to their excellent mechanical performance, which could avoid energy consumption and carbon dioxide emission during the production of construction steel. Concrete structures reinforced with BFRP bars encounter the collapse risk under an occasional accident, such as losing one or several load-bearing members. To date, little research has been performed on the collapse behavior of post-tensioned concrete frames with bonded post-tensioning BFRP bars. This paper developed finite element (FE) models of frame substructures with post-tensioning BFRP bars to investigate their collapse behavior under an interior-column-removal scenario. Parametric analyses show that arranging post-tensioning BFRP bars at the top and bottom of the frame beams or increasing the post-tensioning BFRP bars at the beam bottom could effectively improve the collapse resistance and deformability of the substructures, with the 96.6% and 51.9% improvement at the most, respectively. Reducing initial effective prestress is helpful to the deformability of the frame beams, resulting in a 56.9% increase in ultimate vertical deformation. A mixed reinforcement of BFRP bars and steel reinforcing rebars in the beams is beneficial in preventing collapse. In most cases, the beams’ flexural mechanism and catenary action are essential in resisting the collapse load. The ratio of the maximum vertical displacement at the failed interior column to the net span of the frame beam varies between 0.051 and 0.1. The calculation model for equivalent dynamic increase factors (DIFs) of collapse load was proposed, which could provide a reference for determining DIFs when static collapse analysis is conducted. The DIFs of collapse load for the substructure models were discussed in the proposed method based on the analytical results, indicating that DIFs approached 2.0 at the initial collapse stage and varied between 1.26 and 1.70 at the final collapse failure.

Deformability of non-prismatic prestressed concrete beams with multiple openings of different configurations

Abstract This work presents experimental research using draped prestressed steel strands to improve the load-carrying capacity of prestressed concrete non-prismatic beams with multiple openings of various designs. The short-term deflection of non-prismatic prestressed concrete beams (NPCBs) flexural members under static loading were used to evaluate this improvement. Six simply supported (NPCBs) beams, five beams with openings, and one solid specimen used as a reference beam were all tested as part of the experiment. All of the beams were subjected to a monotonic midpoint load test. The configuration of the opening (quadrilateral or circular), as well as the depth of the chords, were the variables studied in this study. In comparison to a solid beam, experimental results show that beams with openings have a lower load-carrying capacity not exceeding (2.3–10.6%) and higher mid-span deflection through all loading stages of elastic, service, and ultimate loads (14–73%), (19–44%), and (31–55%), respectively. Furthermore, specimens with circular openings had stiffer behaviour under load than those with quadrilateral openings. Beams with quadrilateral openings and inclined posts, on the other hand, were stiffer than beams with quadrilateral openings and vertical posts.

50. IDENTIFICATION OF MOLECULAR RELATIONSHIPS BETWEEN LIVING AND POST-MORTEM BRAIN TISSUE

The regression equations developed for projecting the effective factors of high-grade RC beams with hybrid confinement are presented in this study (cellular stirrups and externally bonded GFRP wraps). Six 150 × 250 × 3000 mm RC beams were constructed and tested to see how hybrid confinement affected the strength, deformability, and ductility of high-grade RC beams. To identify the final failure point, the beams were put through a four-point flexure test. Load application has been made easier thanks to a jack and pump setup, and deflections have been measured with 0.01 mm dial gauges. The suggested regression equations accurately predicted the effective components to a respectable degree.

Influence of the percentage of reinforcement by unstressed rebar on the deformability of pre-stressed RC beams

Abstract This article presents the materials of deformability studies of pre-stressed steel-concrete beams reinforced with a package of reinforcement with different ratio of tape and rebar in the pure bending moment zone. The aim of the research was determination of the reinforcement percentage influence, for pre-stressed reinforced concrete beams reinforced with a package of reinforcement on their deformability. Also, the aim was to evaluate the effectiveness of using pre-stressed rebar in combined reinforcement. The practical significance of the experimental research is to study the deformability in pre-stressed bending elements with external tape and rebar reinforcement, taking into account the influence of different ratios of reinforcement areas within the combined reinforcement and development of proposals for such structures` calculation and design. The scientific novelty of the research is in obtaining the deformability characteristics of reinforced concrete beams reinforced with a package of reinforcement (tape and steel bars with periodic profile) with different ratios in the case of static loads` action.

Study of the strength, deformability and crack resistance of beams reinforced with basalt-plastic reinforcement

Study of the strength, deformability and crack resistance of beams reinforced with basalt-plastic reinforcement

АНАЛІЗ УШКОДЖЕНОСТІ МАТЕРІАЛУ КОНСТРУКЦІЙ

The ability of materials to retain the required set of properties under the action of operational loads on the structure is determined by the structural changes that occur under such loads. From the first days of operation, under the influence of force factors, the environment and time, the strength and deformation properties of structures of buildings and structures change. The solution to the main task of construction science - reducing material consumption in construction, is inextricably linked with the need for constant study and refinement of the strength and deformation characteristics of building materials and structures, as well as a change in their bearing capacity over time and an assessment of the working capacity (resource) reserve when setting an external power load. Based on the fundamental position that under the action of a load, a deformation process occurs in the construction material, which is accompanied by irreversible processes of their appearance, development and accumulation of damage to the structure of the material, and, as a result, leads to destruction, we come to the conclusion that it is necessary to carefully study the strength of wooden designs taking into account this phenomenon. There is a need to comprehensively study the issues of damage accumulation in wooden structures under the action of loads and the related processes of changing the cross-sectional area and bearing capacity, to use the research results when calculating structures. This makes it possible to reduce material consumption and make the sections of wooden structures more economical and avoid excessive safety margins. Therefore, an important manifestation is the fixation of cracks and internal interfaces, which allows one to quantify the integral damage of the structure material to predict their safe functioning. The authors considered analytical dependences for the description of disseminated injuries that follow from physical considerations or are constructed from some mechanical models of the process of long-term damage. Three main types of models have been identified: force, deformation and energy. Experimental studies of normal stress diagrams make it possible to visually record the formation of folds in the compressed zone, as well as calculate the value of the instantaneous elastic and viscoelastic components of total deformation. A measure of the accumulation of damage in a material is damage. In this work, the damage was calculated based on the known specific parameters of the material: deflections, relative deformations and changes in the number of acoustic emission signals. The graphs of the dependence of damage on the load were built: - on the development of deflections; - on the development of fibrous deformations; - on the development of deflections and acoustic emission (relative load); - on the development of fibrous deformations (relative load); This scientific work is a logical continuation of previous studies of damage to wooden structures. The article presents the results of experimental studies of the strength, deformability of wooden beams under the influence of a static load. The direction of improving the methodology for designing wooden structures and determining the residual resource has not been reflected in the technical literature. Therefore, it is necessary to conduct a comprehensive study of them.

Deformability of Steel-Fiber Beams with External Tape Reinforcement

In 2013, the Lviv National Agrarian University patented the construction of a steel-fiber concrete beam, additionally reinforced with an external steel ribbon armature with end anchors. This technical solution allows reducing the cost of the structure by reducing the complexity of its manufacture, due to the absence of a reinforcing frame in the structure. The purpose of this work is to develop proposals for a refined calculation method of deflections of steel-fiber concrete beams with tape reinforcement on the basis of our experimental studies. 3 beams with dimensions 1500x150x60 mm were manufactured. Beam B-1, reinforced with steel tape 1500x60x3 mm with end stops, did not contain fiber. Beams BF-2 and BF-3 in addition to the specified reinforcement contained fiber, corresponding the coefficient of fiber reinforcement by volume, ρfν = 1,5% i 2% respectively. Compressed prisms of 400x100x100 mm and stretched samples of 700x100x60 mm were also tested to determine the mechanical characteristics of concrete and steel-fiber concrete. Loose beams with a working run of 1400 mm were tested with concentrated force applied along the middle of the length. Mass production fiber produced both in Ukraine and abroad with bent ends HE 1050 1 mm in diameter and 50 mm in length was used for reinforcement. The percentage of fiber reinforcement by volume of concrete beams was taken ρfν = 1.5% and 2% to provide enough bearing capacity of the inclined sections. The cement of grade 400 (activity 42.3 MPa) of the Ivano-Frankivsk plant was used to obtain C20 /25 concrete. The test samples were made of fine-grained concrete containing sand from the Yasinets quarry with a fineness modulus of not more than 2.5. Mixtures for beams were made in a forced mixer. The composition of the mixture was chosen so that the settling of the cone did not exceed 4-6 cm and that the fiber did not settle to the bottom of the form. The composition of the mixture per 1 m3 of the mixture was as follows: cement - 549 kg, sand - 1647 kg, water - 285,5 l. The deflections of the steel-concrete beams were smaller than the steel-concrete beams at equal moments. For example, at the moment of 210 kN·cm the experimental deflection values of beams B-1, BF-2 and BF-3 were equal to 0.116; 0.081 and 0.064 cm, and at the moment 420 kN·cm - 0.380; 0.213 and 0.140 cm, respectively. In this paper, it is proposed to determine deflections using the Mora integral and taking into account the results of the calculation of beams by deformation method. The ratio of theoretical and experimental values of deflections was equal to 0.93 … 1.14.

Effect of macro-synthetic structural fibers on the flexural behavior of concrete beams reinforced with different ratios of GFRP bars

Fiber reinforced polymer (FRP) bars are increasingly used as internal reinforcement in concrete structures for mitigating the corrosion problems associated with steel reinforcement. However, its wide spread use in construction is limited by the parameters such as lack of awareness/usage, brittle failure mode, high initial cost, availability of comprehensive guidelines and test data on its long term effectiveness. The use of macro-synthetic structural fibers is explored in this study for improving the post-cracking, and deformability characteristics of glass FRP (GFRP) reinforced concrete beams. In total, eighteen full-scale RC beams with and without structural synthetic fibers are tested under flexure. The test specimens include: (i) control beams with steel reinforcement, (ii) GFRP bar RC beams without macro-synthetic fibers, and (iii) GFRP RC beams with 0.35%, 0.7%, and 1.0% volume of macro-synthetic fibers. The effect of fiber addition on cracking, stiffness and deformability characteristics of GFRP RC beams with different longitudinal reinforcement ratios (0.7% and 2.0%) is investigated. Experimental results reveal that the addition of fibers significantly improved the post-cracking response. Moreover, the crack widths reduced significantly at service loads with the increase in fiber dosage. Addition of 1% fibers helps in enhancing the deformability of GFRP RC beams and converts the failure from brittle flexure-shear to ductile flexure mode with higher pseudo-ductility. Analytical calculations of deflections showed a close correlation with the test results.

Strength compensation of deep beams with large web openings using carbon fiber–reinforced polymer sheets

This article presents the results of an experimental investigation of using carbon fiber–reinforced polymer sheets to enhance the behavior of reinforced concrete deep beams with large web openings in shear spans. A set of 18 specimens were fabricated and tested up to a failure to evaluate the structural performance in terms of cracking, deformation, and load-carrying capacity. All tested specimens were with 1500-mm length, 500-mm cross-sectional deep, and 150-mm wide. Parameters that studied were opening size, opening location, and the strengthening factor. Two deep beams were implemented as control specimens without opening and without strengthening. Eight deep beams were fabricated with openings but without strengthening, while the other eight deep beams were with openings in shear spans and with carbon fiber–reinforced polymer sheet strengthening around opening zones. The opening size was adopted to be 200 × 200 mm dimensions in eight deep beams, while it was considered to be 230 × 230 mm dimensions in the other eight specimens. In eight specimens the opening was located at the center of the shear span, while in the other eight beams the opening was attached to the interior edge of the shear span. Carbon fiber–reinforced polymer sheets were installed around openings to compensate for the cutout area of concrete. Results gained from the experimental test showed that the creation of openings in shear spans affect the load-carrying capacity, where the reduction of the failure load for specimens with the opening but without strengthening may attain 66% compared to deep beams without openings. On the other hand, the strengthening by carbon fiber–reinforced polymer sheets for beams with openings increased the failure load by 20%–47% compared with the identical deep beam without strengthening. A significant contribution of carbon fiber–reinforced polymer sheets in restricting the deformability of deep beams was observed.

Stress-strain state of wooden beams with external reinforcement

The stress-strain state of wood-composite beams was studied numerically. Numerical studies were performed on wood-composite floor beams with a cross-section size of 100×240 mm and a length of 4.8 m. it was Experimentally proved that the deformability of wood-glued beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. For wooden beams in the elastic design stage, the limiter is the calculation of the 2nd group of limit States (for stiffness), for composite beams, the calculation of the 1st group of limit States (for strength. The calculation proved that the deformability of wood composite beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. The high efficiency of the finite element method calculation for evaluating the criteria of load-bearing capacity of wood-composite beams up to their destruction is proved.

Pilot Studies of Concrete Beams Deformability Reinforced with Composite Reinforcement

Purpose of research. Analysis is done on the basis of experimental data of loading level impact on deformability of beams with steel and composite fiberglass reinforcement at prolonged loads.Methods. Experimental studies of concrete bending elements of two series were carried out: the first is reinforced with composite fiberglass reinforcement of ASK class, the second is reinforced with steel reinforcement of А400 class. Studies of experimental samples were carried out under long-term loads. The structures were under different loads during the experiment: at design load, at 1.2 level from design load and at 1.5 from the design load. Concrete deformations and deflections of experimental beams of two series were fixed.Results. Dependence on time of concrete deformations of experimental samples of two series at different loading levels, dependence of deflection growth on load application level, influence dependence of loading level of elements on speed and intensity of creep deformation growth of beams with fiberglass and steel reinforcement are stated on the basis of experimental data. In particular, the bends of all samples with fiberglass reinforcement exceeded the maximum permissible value, while the maximum deflection of reinforced concrete beams in the middle of the section did not exceed maximum permissible value.Conclusion. On the basis of the obtained data, conclusions are drawn on the nature and magnitude of long-term deformations of beams with fiberglass and steel reinforcement at different levels of long-term loads. This conclusion is significant in practical sense when using concrete structures with composite reinforcement taking into account a small number of research data.