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Adelino V Lopes - One of the best experts on this subject based on the ideXlab platform.
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Moment Redistribution in two span prestressed nsc and hsc beams
Materials and Structures, 2017Co-Authors: Sergio M R Lopes, Tiejiong Lou, Muyu Liu, Adelino V LopesAbstract:This paper presents a numerical investigation into two-span continuous prestressed normal-strength concrete (NSC) and high-strength concrete (HSC) beams, focusing on aspects of behavior related to Moment Redistribution. A comparative study is performed by using an experimentally validated computer model. The concrete cylinder compressive strength of investigated beams covers from 40 to 90 MPa, while the prestressing reinforcement ratio (ρ p) ranges from 0.15 to 1.29%. The results show that the tendon tensile strength can be better exploited by HSC than by NSC at moderate to high ρ p levels. At a given level of ρ p, HSC generally mobilizes smaller neutral axis depth, higher strain in nonprestressed steel and a bit larger Moment Redistribution at ultimate than NSC. Typical code recommendations (ACI, CSA and EC2) for permissible Moment Redistribution are examined. The effect of concrete strength on Moment Redistribution in prestressed beams is well reflected in ACI but inadequately reflected in CSA and EC2. A simplified equation for calculating Moment Redistribution in continuous prestressed beams is proposed.
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effect of relative stiffness on Moment Redistribution in reinforced high strength concrete beams
Magazine of Concrete Research, 2017Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Moment Redistribution in continuous concrete beams is primarily a structural aspect of behaviour, since it is a consequence of structural redundancy. However, the current design codes do not take this structural characteristic into consideration and therefore may not be reasonable when predicting the permissible Moment Redistribution. In this paper, Moment Redistribution in reinforced high-strength concrete (HSC) beams is analysed, focusing on the effect of relative stiffness represented by the structure-related parameter ρs2/ρs1 (where ρs1 and ρs2 are the tensile steel ratios over positive and negative Moment regions, respectively). A numerical evaluation was conducted on two-span continuous beams made of HSC having a cylinder compressive strength of 90 MPa. A wide range of ρs2/ρs1 was produced by varying either ρs1 or ρs2 from 0·81% to 6·06%. The results show that the ρs2/ρs1 ratio is a critical parameter influencing the global Moment Redistribution behaviour. Modifications to the Canadian Standards Ass...
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neutral axis depth and Moment Redistribution in frp and steel reinforced concrete continuous beams
Composites Part B-engineering, 2015Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Abstract The neutral axis depth is considered the best parameter for quantifying the Moment Redistribution in continuous concrete beams, as exemplified in various design codes worldwide. It is therefore important to well understand the variation of neutral axis depth against Moment Redistribution. This paper describes a theoretical investigation into the neutral axis depth and Moment Redistribution in concrete beams reinforced with fibre reinforced polymer (FRP) and steel bars. A finite element model has been developed. The model predictions are in favourable agreement with experimental results. Three types of reinforcement are considered, namely, glass fibre, carbon fibre and steel. Various levels of reinforcement ratio are used for a parametric evaluation. The results indicate that FRP reinforced concrete continuous beams exhibit significantly different response characteristics regarding the Moment Redistribution and variation of neutral axis depth from those of steel reinforced ones. In addition, it is found that the code recommendations are generally unsafe for calculating the permissible Moment Redistribution in FRP reinforced concrete beams, but the neglect of Redistribution in such beams may be overconservative.
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factors affecting Moment Redistribution at ultimate in continuous beams prestressed with external cfrp tendons
Composites Part B-engineering, 2014Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:A numerical investigation of Redistribution of Moments in continuous concrete beams prestressed with external carbon fiber reinforced polymer (CFRP) tendons at failure loads is described. A finite element analysis (FEA) model is introduced, and an extensive parametric study is carried out on two-span continuous beams. The factors examined in this study include the content of non-prestressed steel, tendon eccentricities, tendon area, effective prestress, span-to-height ratio, concrete strength, CFRP modulus of elasticity and load type. The results obtained from FEA are compared with those obtained from various codes. The study shows that the importance of some factors is not reflected in the codes. When used to calculate the degree of Moment Redistribution in these beams, the parameter et (net strain in extreme tension steel) seems to be more reasonable than the parameter c/d (ratio of neutral axis depth to section effective depth). A simplified equation for calculating the degree of Moment Redistribution at ultimate is proposed.
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evaluation of Moment Redistribution in normal strength and high strength reinforced concrete beams
Journal of Structural Engineering-asce, 2014Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:AbstractThis article presents an investigation of Redistribution of Moments in normal-strength concrete (NSC) and high-strength concrete (HSC) continuous beams. A nonlinear computer model is introduced and validated by experimental results of HSC continuous specimens. A numerical test is performed on two-span continuous beams where the concrete strength varies between 30 and 90 MPa so as to cover both NSC and HSC beams. Various tensile steel ratios over the center support ρs2 and midspan ρs1 are used. Some rules related to Moment Redistribution are examined. The study confirms that the Moment Redistribution is dependent on the stiffness of the critical sections. The analysis also indicates that full Redistribution of Moments is more likely to be developed in HSC beams than in NSC beams. The results of a parametric study, where the ratio ρs2/ρs1 is fixed at 0.8, show that at a given steel ratio, a higher concrete strength registers higher Redistribution of Moments except when ρs2<1.55 precent. The effect ...
Tiejiong Lou - One of the best experts on this subject based on the ideXlab platform.
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Moment Redistribution in continuous externally cfrp prestressed beams with steel and frp rebars
Polymers, 2021Co-Authors: Tiejiong Lou, Miao PangAbstract:This paper assesses the impact of adopting carbon- or glass-fiber-reinforced polymer (CFRP or GFRP) instead of steel rebars on the Redistribution of Moments in prestressed concrete beams (PCBs) with external CFRP tendons. A numerical program is introduced, and numerical simulations are performed on two-span continuous beams with steel, CFRP or GFRP rebars of various areas, i.e., Ar2 = 360–3560 mm2, and Ar1/Ar2 = 1.5, where Ar1 and Ar2 are areas of tensile rebars over the positive and negative Moment zones, respectively. The results show the Moment Redistribution is contributed by concrete cracking only for the beams with fiber-reinforced polymer (FRP) rebars, and by concrete cracking and steel yielding for the beams with steel rebars. As a result, the use of FRP rebars leads to a substantially lower Moment Redistribution than in steel rebars. It is also demonstrated that Eurocode 2, CSA A23.3-04 and ACI 318-19 fail to reflect the rebar influence on Moment Redistribution in PCBs with external tendons. A simplified equation for the quantification of Moment Redistribution in externally PCBs with steel and FRP rebars is recommended, which yields accurate and conservative predictions.
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Moment Redistribution versus neutral axis depth in continuous psc beams with external cfrp tendons
Engineering Structures, 2020Co-Authors: Tiejiong Lou, Chengming Peng, Theodore L Karavasilis, Di Min, Wei SunAbstract:Abstract The neutral axis depth is adopted by many codes of practice as an indicator of flexural ductility to quantify Moment Redistribution in continuous prestressed concrete (PSC) beams. Moment Redistribution, however, does not only depend on ductility but also on differences in stiffness along the length of the beam. Therefore, the effectiveness of using solely the neutral axis depth for Redistribution quantification needs to be further evaluated. This study examines Moment Redistribution against neutral axis depth in two-span PSC beams with external CFRP tendons by applying a validated finite element model. The main variable is the content of non-prestressed reinforcement either at the positive or negative Moment zone to generate varying stiffness differences between critical sections. The study shows that the use of neutral axis depth as a key parameter is inadequate when quantifying Moment Redistribution in these beams. Modifications of CSA, BSI and EC2 equations are proposed by introducing a parameter reflecting the impact of stiffness difference. The proposed equations show much better fit to the actual Redistribution than that provided by equations in current design codes.
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Moment Redistribution in two span prestressed nsc and hsc beams
Materials and Structures, 2017Co-Authors: Sergio M R Lopes, Tiejiong Lou, Muyu Liu, Adelino V LopesAbstract:This paper presents a numerical investigation into two-span continuous prestressed normal-strength concrete (NSC) and high-strength concrete (HSC) beams, focusing on aspects of behavior related to Moment Redistribution. A comparative study is performed by using an experimentally validated computer model. The concrete cylinder compressive strength of investigated beams covers from 40 to 90 MPa, while the prestressing reinforcement ratio (ρ p) ranges from 0.15 to 1.29%. The results show that the tendon tensile strength can be better exploited by HSC than by NSC at moderate to high ρ p levels. At a given level of ρ p, HSC generally mobilizes smaller neutral axis depth, higher strain in nonprestressed steel and a bit larger Moment Redistribution at ultimate than NSC. Typical code recommendations (ACI, CSA and EC2) for permissible Moment Redistribution are examined. The effect of concrete strength on Moment Redistribution in prestressed beams is well reflected in ACI but inadequately reflected in CSA and EC2. A simplified equation for calculating Moment Redistribution in continuous prestressed beams is proposed.
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effect of relative stiffness on Moment Redistribution in reinforced high strength concrete beams
Magazine of Concrete Research, 2017Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Moment Redistribution in continuous concrete beams is primarily a structural aspect of behaviour, since it is a consequence of structural redundancy. However, the current design codes do not take this structural characteristic into consideration and therefore may not be reasonable when predicting the permissible Moment Redistribution. In this paper, Moment Redistribution in reinforced high-strength concrete (HSC) beams is analysed, focusing on the effect of relative stiffness represented by the structure-related parameter ρs2/ρs1 (where ρs1 and ρs2 are the tensile steel ratios over positive and negative Moment regions, respectively). A numerical evaluation was conducted on two-span continuous beams made of HSC having a cylinder compressive strength of 90 MPa. A wide range of ρs2/ρs1 was produced by varying either ρs1 or ρs2 from 0·81% to 6·06%. The results show that the ρs2/ρs1 ratio is a critical parameter influencing the global Moment Redistribution behaviour. Modifications to the Canadian Standards Ass...
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neutral axis depth and Moment Redistribution in frp and steel reinforced concrete continuous beams
Composites Part B-engineering, 2015Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Abstract The neutral axis depth is considered the best parameter for quantifying the Moment Redistribution in continuous concrete beams, as exemplified in various design codes worldwide. It is therefore important to well understand the variation of neutral axis depth against Moment Redistribution. This paper describes a theoretical investigation into the neutral axis depth and Moment Redistribution in concrete beams reinforced with fibre reinforced polymer (FRP) and steel bars. A finite element model has been developed. The model predictions are in favourable agreement with experimental results. Three types of reinforcement are considered, namely, glass fibre, carbon fibre and steel. Various levels of reinforcement ratio are used for a parametric evaluation. The results indicate that FRP reinforced concrete continuous beams exhibit significantly different response characteristics regarding the Moment Redistribution and variation of neutral axis depth from those of steel reinforced ones. In addition, it is found that the code recommendations are generally unsafe for calculating the permissible Moment Redistribution in FRP reinforced concrete beams, but the neglect of Redistribution in such beams may be overconservative.
Sergio M R Lopes - One of the best experts on this subject based on the ideXlab platform.
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Moment Redistribution in two span prestressed nsc and hsc beams
Materials and Structures, 2017Co-Authors: Sergio M R Lopes, Tiejiong Lou, Muyu Liu, Adelino V LopesAbstract:This paper presents a numerical investigation into two-span continuous prestressed normal-strength concrete (NSC) and high-strength concrete (HSC) beams, focusing on aspects of behavior related to Moment Redistribution. A comparative study is performed by using an experimentally validated computer model. The concrete cylinder compressive strength of investigated beams covers from 40 to 90 MPa, while the prestressing reinforcement ratio (ρ p) ranges from 0.15 to 1.29%. The results show that the tendon tensile strength can be better exploited by HSC than by NSC at moderate to high ρ p levels. At a given level of ρ p, HSC generally mobilizes smaller neutral axis depth, higher strain in nonprestressed steel and a bit larger Moment Redistribution at ultimate than NSC. Typical code recommendations (ACI, CSA and EC2) for permissible Moment Redistribution are examined. The effect of concrete strength on Moment Redistribution in prestressed beams is well reflected in ACI but inadequately reflected in CSA and EC2. A simplified equation for calculating Moment Redistribution in continuous prestressed beams is proposed.
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effect of relative stiffness on Moment Redistribution in reinforced high strength concrete beams
Magazine of Concrete Research, 2017Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Moment Redistribution in continuous concrete beams is primarily a structural aspect of behaviour, since it is a consequence of structural redundancy. However, the current design codes do not take this structural characteristic into consideration and therefore may not be reasonable when predicting the permissible Moment Redistribution. In this paper, Moment Redistribution in reinforced high-strength concrete (HSC) beams is analysed, focusing on the effect of relative stiffness represented by the structure-related parameter ρs2/ρs1 (where ρs1 and ρs2 are the tensile steel ratios over positive and negative Moment regions, respectively). A numerical evaluation was conducted on two-span continuous beams made of HSC having a cylinder compressive strength of 90 MPa. A wide range of ρs2/ρs1 was produced by varying either ρs1 or ρs2 from 0·81% to 6·06%. The results show that the ρs2/ρs1 ratio is a critical parameter influencing the global Moment Redistribution behaviour. Modifications to the Canadian Standards Ass...
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neutral axis depth and Moment Redistribution in frp and steel reinforced concrete continuous beams
Composites Part B-engineering, 2015Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:Abstract The neutral axis depth is considered the best parameter for quantifying the Moment Redistribution in continuous concrete beams, as exemplified in various design codes worldwide. It is therefore important to well understand the variation of neutral axis depth against Moment Redistribution. This paper describes a theoretical investigation into the neutral axis depth and Moment Redistribution in concrete beams reinforced with fibre reinforced polymer (FRP) and steel bars. A finite element model has been developed. The model predictions are in favourable agreement with experimental results. Three types of reinforcement are considered, namely, glass fibre, carbon fibre and steel. Various levels of reinforcement ratio are used for a parametric evaluation. The results indicate that FRP reinforced concrete continuous beams exhibit significantly different response characteristics regarding the Moment Redistribution and variation of neutral axis depth from those of steel reinforced ones. In addition, it is found that the code recommendations are generally unsafe for calculating the permissible Moment Redistribution in FRP reinforced concrete beams, but the neglect of Redistribution in such beams may be overconservative.
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factors affecting Moment Redistribution at ultimate in continuous beams prestressed with external cfrp tendons
Composites Part B-engineering, 2014Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:A numerical investigation of Redistribution of Moments in continuous concrete beams prestressed with external carbon fiber reinforced polymer (CFRP) tendons at failure loads is described. A finite element analysis (FEA) model is introduced, and an extensive parametric study is carried out on two-span continuous beams. The factors examined in this study include the content of non-prestressed steel, tendon eccentricities, tendon area, effective prestress, span-to-height ratio, concrete strength, CFRP modulus of elasticity and load type. The results obtained from FEA are compared with those obtained from various codes. The study shows that the importance of some factors is not reflected in the codes. When used to calculate the degree of Moment Redistribution in these beams, the parameter et (net strain in extreme tension steel) seems to be more reasonable than the parameter c/d (ratio of neutral axis depth to section effective depth). A simplified equation for calculating the degree of Moment Redistribution at ultimate is proposed.
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evaluation of Moment Redistribution in normal strength and high strength reinforced concrete beams
Journal of Structural Engineering-asce, 2014Co-Authors: Tiejiong Lou, Sergio M R Lopes, Adelino V LopesAbstract:AbstractThis article presents an investigation of Redistribution of Moments in normal-strength concrete (NSC) and high-strength concrete (HSC) continuous beams. A nonlinear computer model is introduced and validated by experimental results of HSC continuous specimens. A numerical test is performed on two-span continuous beams where the concrete strength varies between 30 and 90 MPa so as to cover both NSC and HSC beams. Various tensile steel ratios over the center support ρs2 and midspan ρs1 are used. Some rules related to Moment Redistribution are examined. The study confirms that the Moment Redistribution is dependent on the stiffness of the critical sections. The analysis also indicates that full Redistribution of Moments is more likely to be developed in HSC beams than in NSC beams. The results of a parametric study, where the ratio ρs2/ρs1 is fixed at 0.8, show that at a given steel ratio, a higher concrete strength registers higher Redistribution of Moments except when ρs2<1.55 precent. The effect ...
Abbas Tajaddini - One of the best experts on this subject based on the ideXlab platform.
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prediction of capacity for Moment Redistribution in frp strengthened continuous rc t beams
Journal of Composites for Construction, 2017Co-Authors: Abbas Tajaddini, Timothy Ibell, Antony Darby, Mark Evernden, Pedro F SilvaAbstract:AbstractBecause of the premature debonding of fiber-reinforced polymer (FRP) materials that results in a reduction in ductility, the problem of how to exploit Moment Redistribution (MR) in FRP-strengthened continuous reinforced concrete (RC) structures is unresolved. To date, limited research has been conducted into MR in such structures; a reliable and rigorous solution for quantifying MR throughout the loading cycle remains elusive. This paper aims to quantify MR and predict the capacity at reasonable accuracy, to encourage the use of FRP for the strengthening of existing continuous RC structures. Experiments conducted on 12 continuous T-beams are reported, and the findings are discussed. Strengthening configuration and anchorage scheme are the main variables. A new analytical strategy is described for quantifying MR, and the analytical results are then validated against the experimental results. Both experimental and analytical results confirm that there is no reason to restrict MR into strengthened zo...
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quantifying Moment Redistribution in frp strengthened rc beams
Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2016Co-Authors: Abbas Tajaddini, Timothy Ibell, Antony Darby, Mark Evernden, Pedro F SilvaAbstract:Consideration of Moment Redistribution (MR) in the design of continuous reinforced concrete (RC) beams results in an efficient and economical design. Adding fibre-reinforced polymer (FRP) materials to reinforced structures to enhance flexural capacity leads to a reduction in ductility, such that design standards severely limit use of the MR in their design. This has forced engineers to use elastic analyses for strengthening design, which can lead to FRP wastage. To overcome this, complicated or empirical solutions have been applied to solve the problem of MR in strengthened concrete members, with limited success. This paper presents a novel theoretical strategy for quantifying and tracking MR in such members by employing basic structural mechanics without any need for estimating rotation capacity or ductility. Fully non-linear flexural behaviour of continuous strengthened members can be predicted and any geometry, loading arrangement and strengthening technique or configuration can be considered. The nume...
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Moment Redistribution in cfrp strengthened concrete t beams an experimental study
The 12th International Symposium on Fiber Reinforced Polymers for Reinforced Concrete Structures (FRPRCS-12) & The 5th Asia-Pacific Conference on Fibe, 2015Co-Authors: Abbas Tajaddini, Timothy Ibell, Antony Darby, Mark EverndenAbstract:Moment Redistribution in FRP flexurally strengthened continuous reinforced concrete structures is often not allowed (or is limited) in design guidance documents. This is due to the elastic-brittle nature of CFRP composite materials and their propensity to prematurely debond from the concrete surface, resulting in a reduction in the associated ductility of the strengthened concrete section. However, there is still a possibility that some Redistribution can occur if sufficient rotation capacity can develop. In this study, the Moment Redistribution capacity of FRP strengthened RC T-beams was examined by testing 6 two-span continuous specimens. The specimens were designed to have 30% Redistribution capacity before FRP strengthening. Different internal steel arrangements as well as various FRP strengthening configurations and anchoring schemes were investigated for each specimen. The experimental results demonstrated that a high amount of Moment Redistribution could be achieved into FRP-strengthened zones, with little restriction, while the degree of Moment Redistribution out of FRP-strengthened zones is highly dependent on the quantity and anchorage of the CFRP composite materials, although some limited but significant Moment Redistribution is generally still possible.
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investigation of Moment Redistribution in frp strengthened continuous rc beams and slabs
2015Co-Authors: Abbas TajaddiniAbstract:Most reinforced concrete (RC) structures are continuous in some way, and many of these structures are strengthened using fibre-reinforced polymer (FRP) materials as a routine basis. The problem of how to exploit Moment Redistribution in FRP-strengthened continuous RC structures is still unresolved. Reduction in ductility has been recognised in such structures. However, FRP-strengthening is introduced as an effective method to enhance the strength and load bearing capacity of RC structures. As a result, design guidelines worldwide employ conservative guidance for design, such that they limit the potential exploitation of Moment Redistribution in FRP-strengthened members. To date, limited research has been conducted into the Redistribution of bending Moment in such structures. Previous theoretical studies have not yet led to a reliable and rigorous solution for quantifying Moment Redistribution throughout the loading cycle. In addition, a wide scatter of Moment Redistribution percentage findings, from zero to 56%, has been reported in previous experimental studies. This demonstrates the need for further research to effectively characterise the circumstances under which Moment Redistribution can be relied on, both into and out of FRP-strengthened zones in continuous RC flexural members. This research aims to encourage the use of FRP for strengthening existing RC structures in a more efficient manner. The findings help to better understand restrictions on Moment Redistribution into and out of FRP-strengthened zones, effect of mechanical anchorage of the FRP on the degree of Moment Redistribution, and the extent to which Moment Redistribution can be relied on. A new analytical model, only based on structural mechanics, is developed in this research. A comprehensive set of large-scale structural testing is undertaken to validate the analytical model under various strengthening circumstances. The analytical and experimental results show that Moment Redistribution can occur into FRP-strengthened zones to full capacity without any limitation, even if the FRP is unanchored. Further, bending Moment can also be redistributed out of strengthened zones to a considerable extent (up to 20%), depending on the quantity and stiffness of the FRP, and provided that the FRP is fully anchored. A set of parametric studies is conducted to investigate the effectiveness of different parameters on the level of Moment Redistribution. The major parameters include compressive strength of concrete, steel reinforcement proportion, steel yield strength, FRP quantity and stiffness, ultimate strain of the FRP, strengthening configuration, load position, beam shape, and curvature ductility. The outcomes demonstrate that it is not only the curvature ductility of FRP-strengthened sections that is important to the capacity for Moment Redistribution (out of such zones), but also the mode of failure, strength of the other critical zones, the ratio of stiffness between the critical zones, and the loading arrangement. It is concluded that Moment Redistribution in continuous FRP-strengthened concrete structures should be permitted both into and out of strengthened zones, provided that the criteria for such Redistribution are met.
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experimental study of Moment Redistribution in reinforced concrete slabs strengthened with cfrp sheets
Advanced Composites in Construction (ACIC 2015), 2015Co-Authors: Abbas Tajaddini, Timothy Ibell, Antony Darby, Mark EverndenAbstract:© 2015, NetComposites Limited. Due to the elastic behaviour and brittle nature of CFRP composite materials, and also their tendency to debond from the surface of Reinforced Concrete (RC) members before their tensile capacity is reached, Moment Redistribution is often not permitted in design codes for FRP-strengthened RC flexural structures. In this study, the Moment Redistribution capacity of RC slabs is examined by testing seven two-span slabs with externally bonded CFRP sheets. The specimens were designed to have an upper-bound original 30% Redistribution capacity before FRP strengthening. Various strengthening configurations and anchoring schemes for the CFRP fabric were used in the specimens. The experimental results showed that it is feasible to redistribute a high proportion of bending Moment into FRP-strengthened zones. It was also found that the level of Moment Redistribution exhibited out of these FRP-strengthened zones can be significant, depending on the quantity and anchorage of the CFRP composite material used.
Deric John Oehlers - One of the best experts on this subject based on the ideXlab platform.
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design for Moment Redistribution in frp plated rc beams
Structural Engineering and Mechanics, 2011Co-Authors: Deric John Oehlers, Matthew Hasketta, M Mohamed S AliAbstract:Assessing the ductility of reinforced concrete sections and members has been a complex and intractable problem for many years. Given the complexity in estimating ductility, members are often designed specifically for strength whilst ductility is provided implicitly through the use of ductile steel reinforcing bars and by ensuring that concrete crushing provides the ultimate limit state. As such, the empirical hinge length and neutral axis depth approaches have been sufficient to estimate ductility and Moment Redistribution within the bounds of the test regimes from which they were derived. However, being empirical, these methods do not have a sound structural mechanics background and consequently have severe limitations when brittle materials are used and when concrete crushing may not occur. Structural mechanics based approaches to estimating rotational capacities and rotation requirements for given amounts of Moment Redistribution have shown that FRP plated reinforced concrete (RC) sections can have significant Moment Redistribution capacities. In this paper, the concept of Moment Redistribution in beams is explained and it is shown specifically how an existing RC member can be retrofitted with FRP plates for both strength and ductility requirements. Furthermore, it is also shown how ductility through Moment Redistribution can be used to maximise the increase in strength of a member. The concept of primary and secondary hinges is also introduced and it is shown how the response of the non-hinge region influences the Redistribution capacity of the primary hinges, and that for maximum Moment Redistribution to occur the non-hinge region needs to remain elastic.
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analysis of Moment Redistribution in fiber reinforced polymer plated rc beams
Journal of Composites for Construction, 2010Co-Authors: Martin Haskett, Deric John Oehlers, Mohamed R AliAbstract:Ductility of RC structures has always been a classical area of concrete research. Given the complexity of the problem, the great mass of research investigating ductility, and specifically, Moment Redistribution and rotational capacities, has used empirical approaches to quantify Moment Redistribution and invariably assumed that concrete crushing is the singular mode of failure. With the advent of new reinforcement materials such as fiber reinforced polymers, these empirical approaches are not necessarily appropriate as failure modes other than concrete crushing can occur. In this paper, the empirical approaches to Moment Redistribution are replaced by a structural mechanics approach that incorporates Moment rotation directly into Moment Redistribution. A structural mechanics method for determining Moment and rotation at failure for any RC section with any material properties is first presented and this is followed by a structural mechanics model for Moment Redistribution; these enable the Moment Redistribution capacities of any RC section to be quantified. Moment Redistribution capacities of various sections are analyzed and it is shown that plated sections can have significant Moment Redistribution capacities much of which can be used in design.
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Moment Redistribution in reinforced concrete beams
Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2010Co-Authors: Deric John Oehlers, Martin Haskett, M Mohamed S Ali, M C GriffithAbstract:Structural engineers have long recognised the importance of ductility in the design of reinforced concrete structures and, as a consequence, the importance of the ability of a reinforced concrete member to redistribute Moment to give prior warning of failure, adjust the structural response to allow for variations in applied load and column drift, and to absorb energy during earthquake, blast and other dynamic loadings. Quantifying the ability of a member to redistribute Moment, which at first sight appears to be a relatively simple problem, has been difficult and the problem is still unresolved as can be seen by the very wide range of permissible Moment Redistribution values in national standards. In this paper, established techniques of shear friction, partial interaction and rigid body displacement are combined to develop a novel structural mechanics based mathematical model for Moment Redistribution that can be applied to any member with any material property such as the use of brittle reinforcement.
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Design for Moment Redistribution in RC Beams Retrofitted with Steel Plates
Advances in Structural Engineering, 2010Co-Authors: Martin Haskett, Deric John Oehlers, M.s. Mohamed AliAbstract:It is now common practice to retrofit reinforced concrete members by adhesively bonding steel or fibre reinforced polymer plates to their surfaces. However, tests have shown that these plated RC structures tend to have less member ductility, or rotational capacity, than the unplated structure because of premature plate debonding. In this paper, structural mechanics approaches are described for both: quantifying the Moment rotation capacity, or member ductility, of steel plated RC flexural members; and quantifying the Moment Redistribution capacity from the Moment rotation capacity. It is shown how the Moment Redistribution structural mechanics model can be used to design for member ductility directly and, furthermore, it is applied to both externally bonded and near surface mounted steel plates. As would be expected, it is shown that steel plating produces more ductile members than fibre reinforced polymer plating.
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Moment Redistribution in RC Beams Retrofitted by Longitudinal Plating
Advances in Structural Engineering, 2006Co-Authors: Deric John Oehlers, Martin Haskett, P. Antram, L Campbell, R. ByrneAbstract:The ability to redistribute Moment within a reinforced concrete frame or structure is an intrinsic requirement in design. This is generally dealt with using the established neutral axis depth factor, the ku approach, with fixed hinge lengths, which require the flexural member to fail by concrete crushing and which, in turn, requires large strains in the tension reinforcement. As longitudinally plated flexural members tend to fail by plate debonding or plate fracture before the concrete crushes, an alternative approach is presented which is based on variable hinge lengths, which can cope with beam failure at any tension reinforcement strain, and which can be applied to both longitudinally plated and unplated structures.