Deflection Of Concrete Beams Research Articles

Control of long-term deflections of RC beams using reinforcements and low-shrinkage concrete

An experimentally based programme was conducted to assess the influence of heterogeneity on the long-term deflection of reinforced concrete (RC) elements with compression reinforcement and low-shrinkage concrete. These two structural measures are usually employed by designers to mitigate deflection of concrete beams, slabs and bridge decks due to creep and shrinkage effects. Control of creep and shrinkage deflections is important for successful design of concrete elements as the deflections influence their sizing and thus the associated costs. A 5 year experimental study was undertaken to address the most common alternative design approaches to alleviate long-term deflections of concrete. These included variable reinforcement ratios within the compressive zone, variable tensile reinforcement ratios, low-shrinkage concrete within the compressive zone and a combination of these measures. In total, 12 cantilever beam specimens were tested in the laboratory under controlled environmental conditions, supported by a time-dependent finite-element model. Both numerical and experimental results showed RC beam deflection reductions of up to 85% could be achieved when both compressive reinforcement and low-shrinkage concrete were employed.

Impact of low-cycle loads on deflections and width of crack opening of concrete beams with different types of reinforcement

The article presents the studies of the impact of low-cycle loads on experimental samples of concrete beams with different types of reinforcement – unstressed steel bars; steel pre-stressed reinforcement and unstressed reinforcement (mixed reinforcement); basalt-plastic reinforcement. Influence of low-cycle loads on the width of cracks opening and deflections of concrete beams were established. The research results of beams with steel reinforcement without pre-stressing, with pre-stressing and the beams with basalt-plastic reinforcement have shown interrelated proportional relative increase of the width of cracks opening and increase of deflections. Suggestions for consideration of the impact of low-cycle loads during the calculation of bending concrete beams reinforced with steel or basalt-plastic reinforcement by the second group of limit states were proposed. Coefficients determined experimentally for calculating the deflections and the width of cracks opening of the beams were introduced into the equation. Taking into account the impact of low-cycle loads during the calculation of bending concrete structures reinforced with steel or basalt-plastic reinforcement will provide higher reliability of such structures performance.

Finite Element Analysis and Influence Factors of Flexural Behavior of HFRP Reinforced Concrete Beams

HFRP (Hybrid Fiber Reinforced Plastics) ribs are a new type of composite rib made of a mixture of two or more continuous reinforcing fibers. Since the HFRP ribs have a "pseudo-yield" phase similar to that of steel bars, the mechanical properties of HFRP reinforced concrete structures are quite different from those of single FRP reinforced concrete, and should be studied in depth. In this paper, the finite element analysis of the hybrid effect of HFRP bars and the flexural behaviour of HFRP reinforced concrete beams is carried out. The ANSYS finite element analysis software is used to simulate the bending test of carbon/glass HFRP reinforced concrete beams with three different hybrid ratios. The calculation results are compared with the experimental results, and the rationality of the finite element model is verified. On this basis, the influence of mixing ratio, reinforcement ratio and concrete strength on the deflection of concrete beams is further analysed.

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.

Analysis of Steel Fiber Randomly Distributed Concrete Beams Based on ABAQUS

In this paper, the stochastic distribution of steel fiber in concrete beam is realized by using MATLAB modeling software. Firstly, MATLAB software is used to establish random distribution of steel fibers of different number, length and position, and the steel fiber model is assembled in an embedded way with the concrete model. Then the ABAQUS software is used to carry out the three point bending monotonic loading test on the model, and the stress curves and deflection curves of different steel fiber concrete are obtained. The effect of steel fiber on tensile and crack resistance in concrete is analyzed. The effect of volume, length and location of steel fiber on stress, strain and deflection of concrete beam is studied. The results show that the increase of the volume fraction can decrease the deflection and increase the tensile strength of the material, while the length has no significant effect. The distribution can significantly affect the efficiency of the fiber.

Influence of Filler Materials (Limestone Powder and Marble Powder) on the Flexural Strength of Self Compacting Concrete (SCC) Beams, Experimental and Analytical Approaches

Self-Compacting Concrete (SCC) is a highly-workable concrete which fills the formwork without any vibration or impact under its own weight, and it also passes easily through small spaces between rebars. In the present investigation, Self-compacting concrete is achieved by partially replacing cement (40%) using Fly Ash (FA), Silica Fume (SF), Limestone Powder (LP) and Marble Powder (MP) at different percentages by mass of cement. Experimental investigations were carried out for twenty beams to validate the analytical results. To carry out the analysis, totally twenty beams with different mix ID is built using comprehensive computer software ANSYS 14.5. The static nonlinear analysis is done to find out the maximum deflection of the beam. This study assimilate the analysis of RC rectangular beams subjected to two point loading using Non-linear Finite element method (ANSYS 14.5 software) and to validate it experimentally. Using ANSYS software, ultimate load, crack pattern and deflections were determined at span of the beam. The comparison between ANSYS results and experimental results were made in terms of deflection of concrete beams. From the analytical results, it is found that the mix containing 15% silica fume (15SF) is optimum. It is found that the results of the finite element analysis by ANSYS 14.5 package have a close agreement with the experimental results.

Modelling of load–deflection of concrete beams internally prestressed with unbonded CFRP tendons

A theoretical model was developed for predicting the flexural load–deflection of simply supported concrete beams internally prestressed with unbonded carbon fibre reinforced polymer (CFRP) tendons under four-point loading. At each state in the load–deflection curve (initial cracking state, initial yielding state (if any) and ultimate load state), three equivalent rectangular curvature blocks, which can closely simulate the beam rotations at the supports and the midspan beam deflection, were determined by iteratively correcting the strain value of the unbonded tendon. The validity of the model was demonstrated by comparing its predictions with the test results of four rectangular beams and two T-beams with different prestressing reinforcement ratios, initial prestressing and type of auxiliary bar. The developed model was used to examine the effects of different parameters on the first cracking and ultimate strengths of the beam and the additional strain of the unbonded tendon to the effective strain.

Study on the Deflection Behavior of HRBF RC Beams under Serviceability Limit States

In order to investigate the deflection behavior of concrete beam reinforced with high strength hot rolled bars of fine grains (HRBF) under deflection control condition, four concrete beams reinforced with HRBF400 and HRBF500 rectangle cross-section concrete beam static bending test were made. The results show that Mid-span deflection of concrete beams reinforced with HRBF400 under normal conditions still meets the requirement of current code while concrete beams reinforced with HRBF500 could not meets the requirement. Mid-span deflection was calculated by current code and compared with experimental value, the results show that calculate value was a little bigger than experimental value and tend to be safe, deflection could still calculated by the current code. Bearing capacity calculates formula under the conditions of deflection control was proposed, conception of component’s bearing capacity utilization coefficient (BCUC) was put forward. Effects of reinforcement strength, concrete grade, reinforcement ratio and depth-span ratio on BCUC were analyzed.

Study on Shear Behaviour of Concrete Beams Prestressed with External CFRP Tendons

Based on independent research and development of a CFRP tendons wedge-type anchorage, the shear tests of six CFRP external prestressing concrete beams were done. Among them, CFRP external tendons of three pieces were installed in straight line while other pieces were installed in curved line. The results of experimental research show that shear behaviour of concrete beams prestressed with CFRP external tendons are the similar process to the traditional prestressed reinforced concrete beams. They go through the elastic stage, the stage of crack extension, the yield stage of internal hoop reinforcements at the intersection of inclined cracks and the failure stage. When external CFRP tendons are arranged in the same situation, the cracking load and the shear capacity of concrete beams prestressed with CFRP external tendons reduce gradually along with the increase of shear-span ratio,.When shear-span ratio is equal, the cracking load and the shear capacity of concrete beams prestressed with curved arrangement of CFRP external tendons are larger than those of concrete beams prestressed with straight arrangement of CFRP external tendons. Compared with traditional concrete beams prestressed with external steel bars, due to elasticity modulus and shear modulus of CFRP tendons are both smaller than those of steel bars, the mid-span deflection of concrete beams prestressed with CFRP external tendons at the time of shear failure is bigger than that of traditional concrete beams prestressed with external steel bars under the same circumstance.

Research on the Short-Time Deflection of Concrete Beams Reinforced with 500MPa Steel Bars

Fourteen concrete beams reinforced with 500MPa longitudinal steel bars were tested under two-point symmetrical concentrated static loading to investigate their deflection characteristics. And the formula for short-time stiffness specified in the code for design of concrete (GB50010-2010)were evaluated using the experimental results and available test data of 74concrete beams reinforced with 500MPa longitudinal steel bars. The results show that the deflection behavior of beams with 500MPa longitudinal steel bars is essentially similar to that of beams reinforced with conventional steel reinforcements. It is also shown that the formula for short-time stiffness under service loads specified in GB50010-2010 is applicable for flexural members reinforced with 500MPa longitudinal steel bars. Comparisons of the test results with the calculated values for the short-time deflection according to GB50010-2010 show that the code method can be used to estimate the short-time deflection for beams reinforced with 500MPa longitudinal steel bars, but that the method is somewhat less accurate for beams with light reinforcement ratio and low-strength concrete.

Structural Deflection Measurement with a Range Camera

AbstractRange cameras offer great potential for the measurement of structural deformations because of their ability to directly measure video sequences of three-dimensional coordinates of entire surfaces, their compactness, and their relatively low cost compared with other active imaging technologies such as terrestrial laser scanners. Identified limitations of range cameras for high-precision metrology applications such as deformation measurement include the high (centimeter level) noise level and scene-dependent errors. This paper proposes models and methodologies to overcome these limitations and reports on the use of a SwissRanger SR4000 range camera for the measurement of deflections in concrete beams subjected to flexural load-testing. Results from three separate tests show that submillimeter precision and accuracy—assessed by comparison with estimates derived from terrestrial laser scanner data—can be achieved. The high-accuracy range camera results were realized by eliminating the systematic, scen...

Comparative Study on Deflection Calculation for Concrete Flexural Members with Fiber Reinforced Polymer Reinforcement

The application and development of FRP bars for reinforce concrete structures necessitates the need for either adopt the current code method or exploiting a new design one to account for the properties of FRP materials. The method for predicting deflection of concrete beams with FRP bars in ACI440 is based on the method for that with steel bars in ACI318. Similarly, a modified method based on GB50010 is proposed in this paper to estimate deflection of concrete beams with FRP bars. Furthermore, the new method, together with ACI318, ACI440 and GB50010 ones, are verified by nine test beams in three existing experiment and show a good agreement with the experimental data. Simultaneously, the new method is also proved to be of the most precise and accurate one and indicates the potential of the method to estimate deflection in Chinese code system.

New Approach for Estimating the Deflection of Beams Reinforced with FRP Reinforcement

Due to concerns with corrosion, the use of fiber-reinforced polymer (FRP) as a replacement to conventional steel reinforcement has greatly increased over the last decade. Researchers have identified the distinctive mechanical and bond properties of FRP reinforcement that prevent the use of existing relationships to establish serviceability of concrete structures reinforced with such products. Although studies have modified these empirical relationships to describe the behavior of structures reinforced with FRP reinforcement, this paper will provide a new approach to estimate deflection of concrete beams by considering material properties of the reinforcement and incorporating the effects of tension stiffening. Accuracy and precision of the approach was established by performing a statistical analysis on a database containing 171 FRP-reinforced concrete beams. Results were compared to those from existing proposed relationships and indicate the potential of the method to estimate deflection at various service conditions.

Deflection and crack-width prediction of concrete beams reinforced with glass FRP rods

Concrete beams reinforced with fiber reinforced polymer (FRP) bars exhibit large deflections and crack widths as compared to concrete beams reinforced with steel due to the low modulus of elasticity of FRP. Current design methods for predicting deflections at service load and crack widths developed in concrete structures reinforced with steel bars may not be used for concrete structures reinforced with FRP bars. Thus, the ACI 440 Committee has provided design guidelines for concrete beams reinforced with FRP bars. Verification of the ACI 440 methods for predicting deflections and crack widths for glass fiber reinforced polymer reinforced concrete beams are presented in this paper. In addition, improvement to the crack width equation was suggested to account for 2 layers of reinforcement. This study shows that ACI 440.1R-01 can be effectively used to predict deflections in concrete beams reinforced with FRP bars and crack width in beams with one-layer FRP bars. However, when FRP bars are placed in two layers, ACI 440.1R-01 can be used after some parameters are modified. Six full concrete beams reinforced with different GFRP reinforcement ratios were load tested and the measured deflections and crack widths were analyzed and compared with those predicted by the proposed models. The experimental results compared well with those proposed by the model.