•A framework integrating the moment-rotation approach into a nonlinear analysis of concrete beams is introduced.•The proposed partial interaction model accounts for the effect of cracking on beam ...behavior, capturing lost stiffness due to crack formation.•The model accurately simulates the load–deflection, crack opening-moment and moment–curvature for concrete beams with and without fibers.•Partial interaction approach exhibits greater accuracy in predicting the behavior of beams under ultimate loads.•The study evaluates the impact of GFRP reinforcement stiffness loss on the global responses of structural elements.
The moment-rotation approach is a promising methodology aimed to predict the rotational capacity of reinforced concrete members. Recently, several authors have applied this method to evaluate the bending behavior of beams, replacing the moment–curvature approach. Considering the partial interaction phenomena, the moment-rotation approach can be used to develop parametric analyses and to assist in the formulation of rational equations for different material combinations. However, the techniques to integrate the moment-rotation approach into a nonlinear structural analysis have not been deeply explored, and the wider use of this methodology requires a rigorous validation. This study proposes and validates a modeling framework that integrates the moment-rotation approach into a reinforced concrete beam analysis based on the conjugate beam method. This model simulates the global stiffness decrease of beams as the cracking progresses. The numerical results were compared with experimental tests from literature performed on fiber-reinforced and plain concrete beams with glass‐fiber reinforced polymer (GFRP) bars. The experimental behavior of deflection, the crack-opening moment, and the moment–curvature were accurately simulated, especially for fiber-reinforced concrete beams. This accuracy indicates that the strategy adopted to integrate the moment-rotation approach into a structural analysis is definitely promising when modeling beams made of new materials.
•Novel approach to assessing buckling behaviour of reinforced concrete columns.•Tension-stiffening included in assessing sectional behaviour under axial loads.•Sectional behaviour combined with ...bar-spring approach to model column deflections.•Two experimentally-obtained slender RC datasets used to assess model validity.•Approach accurate in assessing RC column failure modes, loads and deflections.
Geometric and material nonlinearities inherent in slender reinforced concrete (RC) columns have often limited the accuracy of stability models in determining the deformational response under axial and lateral loading. Design codes for slender RC columns in code provisions employ a factor of safety to compensate for the complex interactions associated with the nonlinearities which results in large discrepancies and magnified for increasing column slenderness. The present study introduces a novel approach in quantifying the moment- rotation relationship of RC column sections parallel to a partial-interaction tension-stiffening model. The moment-rotation model is used to determine axial and lateral load–deflection relationships in addition to stability curves to assess buckling capacities of RC columns for various loading conditions. Extensive experimental studies on the structural behaviour of slender RC columns are used to validate models developed in the study. Results show the effectiveness of the moment-rotation model in predicting column behaviour, and the accuracy of the stability model in determining failure behaviour.
•An experimental and numerical study was presented for strengthened composite beams.•Four composite beams under a static load were tested to validate the numerical model.•It was found that the tendon ...force increased by 18–23% due to the beam bending.•Increasing the DOSC from 40% to 100% led to an increase in the mean maximum load by 46%.•Increasing the DOSC decreased the deflection by 22.5%.
In this paper, an experimental and numerical study was presented for strengthened composite steel–concrete beams using externally post-tensioning tendons with a partial shear connection. Four composite steel–concrete beams under a static monotonic load were tested to validate the numerical model and investigate the different failure mechanisms. The cracking behaviors of the composite beams and overall moment of resistance have been experimentally and numerically studied. The validated numerical model was used to perform a parametric study. It was found that the initial tendon force increased by 18–23% due to the beam bending, which led to an enhancement in the performance of the beam. Moreover, increasing the degree of shear connection (DOSC) from 40% to 100% led to an increase in the mean maximum load by 46% and to decrease the mean maximum deflection by 22.5%. In addition, there was an improvement in the slippage by achieving 28% decrease. Also, there was a decrease in steel flange micro-strain by about 51%.
Buckling loads of partial composite columns under distributed axial loads is investigated in this paper for the first time. The interlayer interaction corresponding to the level of interfacial ...bonding imperfection in the layered heavy composite columns is formulated in the model by a shear slip/stiffness modulus. Governing differential equations and boundary equations are derived and represented in a general dimensionless form. A semi-analytical solution is applied to the governing buckling equations of the presented model using power-series technique to extract critical loads of partial composite columns. Five different classical end types are considered namely clamped–clamped (C-C), clamped-pinned (C-P), clamped-sliding (C-S), clamped-free (C-F) and pinned–pinned (P-P). Also, for two extreme cases of non-composite/zero-interaction and full-composite/perfectly-bonded layered columns, exact closed-form characteristic buckling equations are introduced. A convergence study is conducted to ensure stability of the applied power-series solution. It is demonstrated that the obtained buckling loads for partial composite columns with different end conditions approach those obtained from the exact closed-from solution for the full-composite extreme case when the interfacial shear modulus approaches infinity. Effect of imperfect bonding between the column layers and slip on critical buckling loads is investigated. It is shown that a more realistic model based on the partial composite interaction hypothesis predicts critical loads that are less than those based on idealized composite columns with perfect interfacial bonding.
•A closed-form SE formulation for metamaterial beams with the host PICB is proposed.•An approach combined the SE with WFE method is applied to metamaterial beams.•A benchmark test validates the ...accuracy and efficient of this approach.•Discussing bandgap behaviors covering the position, width and attenuation capacity.•Parameters cover absorber arguments, lattice constant and shear connector stiffness.
Elastic metamaterials with local resonant components exhibit unique bandgap behavior that can be utilized to control the vibration and noise of mechanical structures. This study aims to introduce the bandgap characteristics into the vibroacoustic control of partial-interaction composite beams (PICBs) widely adopted in civil engineering, aviation, and marine fields. Vibration absorbers are arranged periodically on the beam to generate a bandgap in PICBs, thereby transforming a conventional PICB into a metamaterial beam. An analytical approach is proposed to establish the spectral element (SE) matrix of a metamaterial beam based on the Timoshenko–Ehrenfest beam theory. Specifically, the governing equations of motion for PICBs follow Hamilton's principle. This model considers the effects of shear slip between two-layer sub-beams, shear deformations, and rotary inertia. The SE matrix of PICBs is then constructed and applied to obtain the SE matrix of the metamaterial beam by assembling the SE matrix of the vibration absorbers. Subsequently, the wave finite element (WFE) method is employed to predict the dispersion curve of the infinite metamaterial beam and the dynamic response of the finite metamaterial beam. In a benchmark example, the complex band structure and transmission indicated by the proposed approach are validated compared to those calculated by evaluation formulas of the literature and the finite element method. Lastly, the bandgap behavior for the vibration absorber parameters, lattice constants, and shear connector stiffness is investigated based on the defined dimensionless parameters. These results are valuable for optimizing vibration and noise reduction in PICBs equipped with attached vibration absorbers.
Display omitted
Tension‐stiffening controls the serviceability behavior of concrete structures as it is responsible for crack formation and, consequently, the deflection of beams. In fiber reinforced concrete, such ...as ultra‐high performance fiber reinforced concrete (UHPFRC), fibers bridge cracks and thereby transfer tensile stresses across the cracked region, allowing for tensile stresses to be carried by the concrete within the cracked region. Due to structures being designed for longer design lives, the consideration of long‐term effects such as fatigue is required. Much research has examined tension‐stiffening under fatigue when subjected to low cyclic loading, but very little has considered the effects of high‐cycle fatigue, especially for UHPFRC. This paper presents the results of nine UHPFRC tension‐stiffening tests under high‐cycle fatigue in which the crack formation and development under varying cyclic ranges were studied. Specimens were subjected to as many as 5.7 million cycles, and crack readings were taken during each test. The experimental results demonstrate the random nature of cracking on UHPFRC as well as the increase in the crack width under cyclic loads. Finally, this research described the extension of an existing partial‐interaction mechanics model to allow for the stress in the fibers and the increase in crack width due to high cycle fatigue.
Most design codes available today for predicting the deflection of adhesively plated RC beams use a full-interaction moment-curvature approach that requires the flexural rigidity to be quantified ...empirically. Due to their empirical nature, these design rules can only be applied within the bounds of the tests from which they were derived. Furthermore, as these design rules follow a full-interaction analysis, the slip between the reinforcement and adjacent concrete was not considered and the method does not cope with the discrete rotation of the cracks; that is, the deflection associated with crack widening was not directly considered. As an alternative, partial-interaction mechanics-based methods can be used. In this study, a mechanics-based approach for quantifying the deflection of adhesively plated RC beams was presented. The approach took into account the slip between the reinforcement and adjacent concrete, the formation and widening of flexural cracks, and the intermediate crack debonding mechanism of the externally bonded plate. The deflection from the mechanics-based approach was determined by considering the discrete rotation of individual cracks and the curvature of uncracked regions of the beam. The deflection results derived from the mechanics-based approach were compared with the experimental results of seven adhesively plated CFRP RC beams bonded to their tension face and a significant correlation between the results was observed. The mechanics-based approach does not require any components on the member level to be quantified empirically; thus, it could be useful in predicting the deflection of adhesively plated RC beams with new types of reinforcement material.
Bondstress-slip models of externally bonded FRP plates have long been quantified using push/pull shear tests in which the bonded joint is slightly greater than the effective length of the plate. This ...inhibits the formation of a frictional component that may arise in long bonded joints. Moreover, previous researchers have used several factors to represent the bondstress-slip model parameters which gave a rise to a number of models. With that in mind, the first aim of this study was to assess the factors that affect the bondstress-slip parameters (τmax, δ1 and δmax), and to propose a simplified bilinear bondstress-slip model that correlates well with experimental data. The second objective was to predict the frictional component in the bondstress-slip model that develops in FRP plated flexural members using a partial-interaction displacement-based approach, assess the factors that affect the frictional component and investigate the debonding mechanism of FRP plated members with a frictional component. As such, a database consisting of 98 pull/push shear tests available in the open literature was assembled and used to assess the factors that influence the bilinear bondstress-slip model parameters. Subsequently, a simplified bilinear bondstress-slip model was proposed and validated against 288 pull/push shear test results. Next, 8 FRP plated beams were investigated using a displacement-based analysis where it was seen that the frictional component depended largely on the length of the plated members. Also, it was seen that poor correlation with experimental results was observed when a bilinear model without a frictional component was used in the analysis, where the predicted ultimate strength was 66 – 78% of the experimental value. The findings of this study illustrate the importance of considering the frictional component in the bondstress-slip model, and how this may affect the strength, deformation and ductility of the plated member.
This paper presents the formulation of strain-based finite elements for modelling composite beams with finger joints considering slip between the layers. The finite elements are derived according to ...Reissner beam theory based on the modified principle of virtual work where the displacements and rotations are eliminated from the problem and the axial deformation, shear deformation and curvature of the layers remain only functions to be approximated within the finite element. Lagrange polynomials are used as shape functions to approximate the deformations and various interpolation methods are applied to numerical examples, with the Lobatto integration scheme giving slightly better results than Equidistant. The experimentally measured mechanical properties needed as input data for the numerical model are given for the four glued laminated beech beams. The numerical model is thoroughly verified and validated. The results show that the presented finite element formulation is an efficient tool for practical and accurate calculations.
•New finite elements for composite beams with slip and finger joints are proposed.•Numerical model is validated and verified with experimental results.•The finite elements exhibit no slip and shear locking.
•A new perspective is offered to address the RAC-steel bond issue.•The local and global bond characteristics are clearly differentiated.•A generic bond modelling approach is developed for RAC.
It is ...essential, for promoting the structural use of recycled aggregate concrete (RAC), to understand the impact of the incorporation of recycled aggregate (RA) on the bond between steel reinforcement and RAC. However, conflicting findings in existing literature indicate a need for re-evaluating the RAC-steel bond, as well as establishing a unified bond characterization and modelling method. This study provides a critical assessment to address this pivotal issue, in light of a large experimental database built from an extensive survey of the up-to-date literature. Following this, a partial-interaction mechanics-based model is developed to simulate the bond-slip response between steel bars and RAC, covering scenarios from a steel bar pulled out from RAC to the tension stiffening in reinforced RAC members. A parametric study is then undertaken to look into the actual impacts of RA on the global bond behaviour. It turns out that the effects of the attributes of RAC and steel on the bond vary markedly at different scales and these effects further alter with the specimen failure mode. For a RAC specimen with a short anchorage experiencing bar pull-out failure, there appears no clear correlation between the local bond characteristic and the RA replacement level; nonetheless, for a similar specimen yet suffering splitting failure, a higher content of RA or lower strength of RAC tends to impair the local bond capacity. Furthermore, the RA incorporation has a real impact on the global bond behaviour when the bar embedment length is well over five times the bar diameter. The model developed is capable of producing results in good agreement with the experimental measurements, approving that the RA substitution does weaken the global bond characteristic of RAC, due primarily to its lower modulus compared to that of natural aggregate concrete.
PDF
