Deformability Of Beams Research Articles

Numerical analysis on displacements of steel-fiber-reinforced concrete beams

abstract: This work deals with parametric analyses of the structural behaviour of steel-fiber-reinforced concrete using a Damage Constitutive Model and homogenization technique. This approach is contemporary once Brazil has not a standard procedure for the design of this type of material. The present study performs a parametric analysis of rectangular beams subjected to flexion at four points, with height variations (h), reinforcement area (As) and span (L) are used to verify the influence of each parameter on the numerical study of the deformability of beams composed by this material. Fiber volume concentrations of 2.00% and 2.50% have been used on the modelling. It is observed that the obtained results were mainly affected by height and span. It is noticeable that the inclusion of steel fibers leads to an increase in the maximum load and ductility of the analyzed beams in this work.

Post-cracking shear behaviour of concrete beams strengthened with externally prestressed tendons

External prestressing technology has been successfully adopted for enhancing the load-carrying capacity of beams in bridge engineering. Previous studies on the shear behaviour of externally prestressed concrete (EPC) beams mainly focused on the ultimate shear strength. The post-cracking shear behaviour of EPC beams remains unclear. This study aims to investigate the post-cracking shear behaviour of EPC beams. To this end, nine EPC beams with different design parameters were tested to failure. The investigated parameters included the prestressing condition, shear span to depth ratio, shear reinforcement ratio, and bend angle of external tendons. In contrast to reinforced concrete beams, the EPC beams demonstrated shear tension sliding with concrete spalling failure. The applied prestressing increased the concrete shear contribution by 68%. The percentage of the concrete shear contribution out of the total shear strength of the test beams ranged from 45% to 79%. The post-cracking shear strength reserve ability index, defined as the ratio of the shear strength and shear cracking strength, ranged from 1.72 to 2.96 in the EPC beams. A new ductility index, defined as the ratio of the ultimate deflection and the deflection corresponding to first shear cracking, was used to evaluate the post-cracking deformability of EPC beams. The ductility index of the EPC beams ranged from 3.0 to 7.6, indicating considerable post-cracking deformability. The beam’s stiffness at first shear cracking was 39–81% of the beam’s initial stiffness; the beam’s stiffness at the ultimate state was 18–41% of the beam’s initial stiffness. Finally, the current shear provisions were evaluated by the test results.

EXPERIMENTAL RESEARCH ON ASEISMIC BEHAVIOR OF HIGH DUCTILE CONCRETE FILLED STEEL PLATE COMPOSITE COUPLING BEAMS

To improve the aseismic behavior of coupling beams with a small span-to-depth ratio, high ductile concrete (HDC) is used to replace the concrete. Two HDC filled steel plate composite coupling beams, one concrete filled steel plate composite coupling beam and one HDC steel plate composite coupling beam, were designed. The failure pattern, deformation capacity and energy dissipation capacity of composite coupling beams were studied by the quasi-static tests. The experimental results show that the deformability and damage-tolerance of the steel plate composite coupling beams can be improved by replacing concrete with HDC. The synergistic performance of HDC and steel webs is good, which is beneficial to the shear effect of steel webs. The energy dissipation of the HDC filled steel plate composite coupling beams is significantly higher than those of the concrete filled steel plate composite coupling beam and of the HDC steel plate composite coupling beam. The design values of shear-compression ratio of the HDC filled steel plate composite coupling beams is 0.65-0.70, which is obviously higher than that of the HDC steel plate composite coupling beam. Therefore, the shear-compression ratio limitation of the coupling beams can be improved by using the HDC filled steel plate composite coupling beams, and the problem of shear-pressure ratio ultra-limit of coupling beam in design can be solved.

Effective fiber type investigation on the shear behavior of ultrahigh-performance fiber-reinforced concrete beams

In this study, the effects of different fiber types on shear behavior (cracking pattern, shear cracking strength, ultimate shear strength, and post-cracking deformability) of ultrahigh-performance fiber-reinforced concrete beams were investigated experimentally. For this purpose, 15 ultrahigh-performance fiber-reinforced concrete beams including different steel fiber types (two straight, two hooked, and one double hooked) with three volume fractions (0.5%, 1.0%, and 1.5%) were casted without shear reinforcement and tested under four-point loading until the failure. In addition to the experimental program, three existing numerical models proposed for the shear capacity of fiber-reinforced concrete beams were investigated to show the applicability of these models to the ultrahigh-performance fiber-reinforced concrete beams. The experimental results demonstrated that the straight fiber of 13 mm is the most effective fiber type in terms of the considered parameters. However, the addition of 13-mm straight fiber with 1.5% by volume into the ultrahigh-performance fiber-reinforced concrete beam changed the failure mode from the shear to flexure without shear reinforcement.

Flexural strengthening of preloaded reinforced concrete continuous beams: An experimental investigation

This paper investigates experimentally the preloading effect on the flexural behavior of reinforced concrete strengthened continuous beams. Five continuous reinforced concrete beams were tested; they all had the same dimensions and the same reinforcement detailing. Two types of strengthening were used; strengthening with RC jackets and strengthening with CFRP sheets. The five specimens were tested before and after applying the strengthening techniques, but under different preloading levels. For all specimens, deflections and reinforcement strains were recorded throughout the test duration before and after strengthening.The results demonstrated that in case of strengthening with RC jackets, preloading level had an essential role in increasing the flexural load-carrying capacity and the deformability of RC continuous beams, while in case of strengthening with CFRP sheets it didn’t influence either the flexural load-carrying capacity or the deformability of beams. Also comparing the two methods of strengthening showed that strengthening with CFRP sheets improved strength, ductility and dissipated energy and decreased the mid-span deflection at ultimate load of RC continuous beams. On the other side, strengthening with RC layers improved strength, dissipated energy, deflection at ultimate load and ductility of RC continuous beams.

Дослідження несучої здатності та деформативності згинаних деревобетонних балок

Дослідження несучої здатності та деформативності згинаних деревобетонних балок

Seismic performance of steel plate reinforced high toughness concrete coupling beams with different steel plate ratios

Embedded steel plate reinforced concrete (PRC) coupling beams are newly introduced into the family of coupling beams to improve the seismic behavior of reinforced concrete (RC) coupling beams. However, the brittle crush and spalling of concrete in these composite members noticeably reduce their deformation performance and energy-dissipating capacity which largely deteriorate the efficiency of this combination. Considering this noteworthy shortcoming, in this paper the authors propose a novel type of composite coupling beams, which is entitled steel plate reinforced high toughness concrete (PRHTC) coupling beam. This novel member replaces the conventional reinforced concrete with the high toughness concrete (HTC) which is a sort of pseudo strain-hardening cementitious composites exhibiting quasi-ductile behaviors. This study mainly investigates the seismic performance of PRHTC deep coupling beams (span-to-depth ratio, l/h = 1.5) with various steel plate reinforcement ratios. The test results indicate that the PRHTC coupling beams exhibit a ductile flexural failure mechanism with excellent energy dissipation capability. The high toughness concrete in this composite member displays multiple cracking pattern and maintains desirable integrity. All specimens attained high-level ductility factors exceeding 5.5, survived large rotations ranging from 0.064 to 0.078 rad, manifested superior stiffness retention capacity and strength retention capacity. The steel plate ratio ranging from 4.31% to 6.47% is proven to be appropriate and effective for maintaining high ductility and rotation deformability of the PRHTC coupling beams in this paper.

The Experimental Assessment of the Deformability of Cement and Cement-asphalt Matrices with Rubber Powder Additive by Application of DIC System

The paper presents an experimental study of deformability of beams made of cement and asphalt-cement matrices with addition of rubber powder 25÷40% in relation to binders. 4-Point Bending (4-PB) tests were performed with series of specimens after 28 days of hardening. Tests were done at various temperatures, i.e. 5°C, 23°C and 50°C. Monitoring of deformation process was fully recorded by Digital Image Correlation (DIC) system ARAMIS up to the final failure.The cracks in the asphalt-cement matrices with rubber powder initiate when stress state exceeded about 50% of their flexural strength (fct,flex2). The obtained experimental results lead to the general conclusion that addition of rubber powder to different matrices causes increase of deformability, from 2 to 3 times in relation to the pure cement matrix. Moreover, it can be stated that composite materials such as asphalt-cement concrete (ACC), mineral-cement-emulsion mixes (MCEM) with rubber powder additive are more flexible in comparison to the pure cement concrete (CC),

Experimental Study on Concrete Beams Strengthened with Embedded Smart Carbon Fiber Reinforced Plates

Carbon Fiber Reinforced Polymer (CFRP) has been widely used in the field of structural reinforcement and rehabilitation. It would be incorporated with the Optical Fiber Bragg Grating (OFBG) sensing feature, developing the smart carbon fiber reinforced plates (CFRP-OFBG). And then, embedded experiment on five rectangular section beams strengthened with the smart carbon fiber plates were carried out and detected wavelength variation by OFBG to calculate the strain value of carbon fiber plates. Measured center wavelength variation of CFRP-OFBGs and measured strain of CFRPs from strain gauges at the same location were analyzed and plotted by computer. The results demonstrated that: on the one hand, both wavelength and strain showed a better linear relationship, and the slope was about 1.2pm/ . It was in good agreement with the CFRP-OFBG strain sensing degrees, which was 1.281pm/ . On the other hand, using CFRPs to strengthen concrete beams could improve the yield load and ultimate load and reduce deformability of concrete beams. In summary, there are the widely application prospect and value on structural health monitoring and structural reliability analysis in the future.

Study of flexural response of engineered cementitious composite faced masonry structures

This study aims to develop and demonstrate the effectiveness of precast engineered cementitious composite (ECC) plates for strengthening of masonry beams by bonding them on tension face as well as both on tension and compression faces like sandwich beam. Two types of bonding materials have been used, i.e., epoxy and cement mortar for bonding the ECC plates with masonry beam. Experimental flexural response has been predicted for tension strengthened as well as sandwich beams. Detailed parametric study has been performed using ABAQUS commercial software package. The parametric study incorporates the effect of various parameters such as ECC thickness in compression and tension, epoxy and cement mortar as bonding agents, and bonding agent thickness on the flexural response of strengthened beams. All beams were tested under four-point loading systems. The numerical results obtained using ABAQUS are validated with experimental results. The present study results reveal that the application of precast ECC increases the strength and deformability of masonry beams and hence demonstrate its effectiveness as strengthening element for masonry structures. Furthermore, recommendations regarding optimum thickness of ECC strips/plates and bonding agents have been made for external strengthening of masonry beams with precast ECC strips.

Flexural behavior and a modified prediction of deflection of concrete beam reinforced with a ribbed GFRP bars

This study experimentally investigated the flexural capacity of a concrete beam reinforced with a newly developed GFRP bar that overcomes the lower modulus of elasticity and bond strength compared to a steel bar. The GFRP bar was fabricated by thermosetting a braided pultrusion process to form the outer fiber ribs. The mechanical properties of the modulus of elasticity and bond strength were enhanced compared with those of commercial GFRP bars. In the four-point bending test results, all specimens failed according to the intended failure mode due to flexural design in compliance with ACI 440.1R-15. The effects of the reinforcement ratio and concrete compressive strength were investigated. Equations from the code were used to predict the deflection, and they overestimated the deflection compared with the experimental results. A modified model using two coefficients was developed to provide much better predictive ability, even when the effective moment of inertia was less than the theoretical Icr. The deformability of the test beams satisfied the specified value of 4.0 in compliance with CSA S6-10. A modified effective moment of inertia with two correction factors was proposed and it could provide much better predictability in prediction even at the effective moment of inertia less than that of theoretical cracked moment of inertia.

STIFFNESS GLULAM WOOD BEAMS IN TERMS OF SLANTING BEND

The article presents the results of experimental studies of strength and deformability of wooden beams in terms of slanting bend.

Post‐cracking shear strength and deformability of HSS‐UHPFRC beams

AbstractEleven T‐beams, reinforced with high strength steel, were tested to failure to investigate the effect of shear span to depth ratio, fibre ratio, fibre type, concrete strength and stirrup ratio on the shear behaviour, especially post‐cracking shear strength and deformability, of ultra‐high performance fibre reinforced concrete (UHPFRC) beams. Test results indicated that fibres were efficient not only in enhancing the post‐cracking shear strength, but also in improving the post‐cracking deformability of UHPFRC beams. In addition, fibres could bridge the cracks and help in redistributing and homogenizing the concrete stress beside the cracks, allowing more short fine diagonal shear cracks with small spacing to develop around the existing cracks. A moderate amount of stirrups can effectively restrain shear cracks and allow more parallel diagonal shear cracks to develop and propagate thoroughly within the shear span. The stiffness of the UHPFRC beams at ultimate state was about 50 % of initial beam stiffness, which was considerable in strength calculations and ductility analysis, especially in seismic performance evaluation. Lastly, the current shear provisions were evaluated using the experimental results.

Structural performance and serviceability of concrete beams reinforced with hybrid (GFRP and steel) bars

This paper reports on the structural performance of concrete beams reinforced with hybrid reinforcement. Six concrete beams reinforced with a combination of steel and glass fiber-reinforced polymer (GFRP) bars and three other beams reinforced with only GFRP bars were tested in flexure. Over-reinforced hybrid beams showed higher strength and ductility than their GFRP-reinforced counterparts. The CSA-S806-12 equation accurately predicted the deflections of the hybrid-reinforced beams with high effective reinforcement ratios. Based on the test results, a bond coefficient was proposed to predict the crack width of the hybrid-reinforced beams using the ACI-440.1R-06 equation. A modified deformability factor was also utilized to assess the deformability of the hybrid-reinforced beams. Comparison between the experimental and predicted results showed the adequacy of the models used in predicting the load-carrying capacity, deflection, crack widths, and deformability of hybrid-reinforced concrete beams.

Strength and deformability of concrete beams reinforced by non-metallic fiber and composite rebar

Production of durable and high-strength concrete structures with unique properties has always been crucial. Therefore special attention has been paid to non-metallic composite and fiber reinforcement. This article describes the experimental research of strength and deformability of concrete beams with dispersed and core fiber-based reinforcement. As composite reinforcement fiberglass reinforced plastic rods with diameters 6 mm and 10 mm are used. Carbon and basalt fibers are used as dispersed reinforcement. The developed experimental program includes designing and production of flexural structures with different parameters of dispersed fiber and composite rebar reinforcement. The preliminary testing of mechanical properties of these materials has shown their effectiveness. Structures underwent bending testing on a special bench by applying flexural static load up to complete destruction. During the tests vertical displacements were recorded, as well as value of actual load, slippage of rebars in concrete, crack formation. As a result of research were obtained structural failure and crack formation graphs, value of fracture load and maximum displacements of the beams at midspan. Analysis of experimental data showed the effectiveness of using dispersed reinforcement of concrete and the need for prestressing of fiberglass composite rebar.

Analysis and Evaluation of Loading Test for Simple Supported Beams and Cantilever Beams in the Nanxi Bridge of Lechangxia Water Complex

Nowadays, safety evaluation before bridge opening is increasingly emphasized in China. Bridge inspection is important to guarantee the safe operation of the bridge. In order to comprehensively assess the bearing capability and working conditions of Nanxi bridge of Lechangxia water complex, through static loading test and dynamic loading test, we measured the deformability and mechanical properties of bridge beams with different span-ratios and different forms. Basing on the results of dynamic/static loading test as well as the analysis of structure calculation, we conclude that the bearing capability and working state of the bridge are excellent. The knowledge gained from this study can be used as an evaluation reference in the quality evaluation of the same type of projects.

Research on Monotonic and Fatigue Properties of Functionally Graded Composite Beams Crack-Controlled by UHTCC in Bending

This research focuses on mechanical performances of UHTCC-FGC beams under monotonic and fatigue loading. Three UHTCC-FGC beams are tested, including two monotonic beams and one fatigue beam. The stress level of fatigue beam is set as 0.85. The constant ratio of minimum stress to maximum stress is set to 0.2 to avoid any impact and slip between the loading machine and the specimens during testing. The specimen is subjected to sinusoidal cyclic loading at 1 frequency. During the experiments, the fatigue life, deformability and loading capacity of UHTCC-FGC beams are measured and recorded. Meanwhile，the development of cracks and the failure pattern of UHTCC-FGC beams during the test are observed at the same time.

Flexural ductility and deformability of concrete beams incorporating high‐performance materials

AbstractHigh‐performance materials, such as high‐strength concrete (HSC) and high‐strength steel (HSS), are often adopted in tall buildings to reduce member size and save space. The use of HSC and/or HSS can significantly increase the flexural strength of concrete members but may also adversely affect the flexural ductility and deformability. Herein, the pros and cons of using HSC and HSS in concrete beams are investigated in terms of the limits of flexural strength, ductility and deformability that can be simultaneously achieved using nonlinear moment‐curvature analysis with stress‐path dependence of the reinforcement taken into account. The results reveal that the use of HSC or both HSC and HSS in concrete beams can at the same strength increase the ductility and deformability, or increase the strength without depleting the ductility and deformability. However, the use of HSS has no such benefit, albeit it can reduce the steel area required. Copyright © 2010 John Wiley & Sons, Ltd.

Concurrent flexural strength and deformability design of high-performance concrete beams

In the design of earthquake resistant reinforced concrete (RC) structures, both flexural strength and deformability need to be considered. However, in almost all existing RC design codes, the design of flexural strength and deformability of RC beams are separated and independent on each other. Therefore, the pros and cons of using high-performance materials on the flexural performance of RC beams are not revealed. From the theoretical results obtained in a previous study on flexural deformability of RC beams, it is seen that the critical design factors such as degree of reinforcement, concrete/steel yield strength and confining pressure would simultaneously affect the flexural strength and deformability. To study the effects of these factors, the previous theoretical results are presented in various charts plotting flexural strength against deformability. Using these charts, a "concurrent flexural strength and deformability design" that would allow structural engineers to consider simultaneously both strength and deformability requirements is developed. For application in real construction practice where concrete strength is usually prescribed, a simpler method of determining the maximum and minimum limits of degree of reinforcement for a particular pair of strength and deformability demand is proposed. Numerical examples are presented to illustrate the application of both design methods.

Deformability design of high‐performance concrete beams

SUMMARYThe use of high‐performance materials (HPMs) such as high‐strength concrete (HSC) and high‐strength steel (HSS) is becoming more popular in the construction of beams and columns of tall buildings. These HPMs not only increase the stiffness and decrease the strength‐to‐weight ratio, but also provide a more sustainable construction method by minimising the construction materials needed. However, HSC and HSS are more brittle than normal‐strength concrete and steel, respectively. Therefore, it will adversely affect the deformability of concrete beams. To evaluate the pros and cons of adopting HPM in beam design, the author will investigate the flexural strength and deformability of concrete beams made of HPMs. The deformability in this study is expressed in normalised rotation capacity and investigated by a parametric study using nonlinear moment–curvature analysis taking into account the degree of reinforcement, confining pressure, concrete and steel yield strength. From the results, it is evident that the deformability of concrete beams increases as the degree of reinforcement decreases or confining pressure increases. However, the effects of concrete and steel yield strength depend on other factors. For practical design purpose, charts and formulas are produced for designing high‐performance concrete beams to meet with specified flexural strength and deformability requirement. Copyright © 2011 John Wiley & Sons, Ltd.