China
Africa
Explore chapters and articles related to this topic
Design in reinforced concrete to EN 1992
Published in Chanakya Arya, Design of Structural Elements, 2022
Moment distribution analysis assumes that reinforced concrete is an elastic material. However, the coefficients in Table 3.21 make due allowance for its plastic behaviour at ultimate loads and result in lower support moments, leading to improvements in economy and buildability. This process of adjusting the results of an elastic analysis is referred to as moment redistribution. Provided the amount of redistribution is limited to 15%, which is the case with the moments evaluated using Table 3.21, then δ (defined as the moment at section after redistribution/moment at section before redistribution) = 0.85, and Equation 3.11 used to calculate the ultimate moment of resistance, MRd, remains valid. However, if the amount of redistribution exceeds 15%, δ < 0.85 and EC 2 recommends lower limits for x/d (≤ δ − 0.4) in order to ensure plasticity, which in turn result in lower values of K′ in Equation 3.11, as shown in Table 3.22. This aspect is particularly relevant to one-way spanning continuous slabs which are routinely designed for 20% redistribution (see Section 3.10.3).
Beam-and-slab construction: one-way slabs
Published in Charles E. Reynolds, James C. Steedman, Examples of the Design of Reinforced Concrete Buildings to BS8110, 2017
Charles E. Reynolds, James C. Steedman
If the bending moments are determined by using the so-called exact methods of structural analysis discussed in Chapter 3, it is often possible to undertake sufficient moment redistribution to obtain equal bending moments at midspan and over the supports; this simplifies the arrangement of the reinforcement. This has not been done on Calculation Sheets 1 because of the assumptions involved in considering the outer supports to be fully fixed and assuming an infinite number of spans (instead of the true number of six). The actual percentage of redistribution required in the case considered would be about 16%, giving equal span and support moments of 6.63 kN/m per metre, i.e. requiring an area of steel of 428 mm2. This moment is obtained simply by finding the mean value of the maximum span and support moments; this is a simple and safe approximation. However, it is possible to reduce the moments still further by making up to the maximum permissible redistribution of 30%. As explained in detail in section 3.3, since the maximum moments at midspan and support caused by the imposed loads are due to different arrangements of loading it is normally possible to reduce both simultaneously. In the example considered both span and support moments can simultaneously be reduced to 5.38 kN/m per metre, which would require an area of 348 mm2 per metre width. When making such a redistribution, however, the corresponding restriction on the maximum value of x/d must be borne in mind.
Fatigue of steel bridge infrastructure
Published in Hyun-Moo Koh, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Health Monitoring and Informatics, 2008
Hyun-Moo Koh, Dan M. Frangopol
Moment redistribution in beams has traditionally been considered as an Ultimate Limit State (ULS) phenomenon closely associated with considerations of reinforced ductility and it reveals the realistic strength of reinforced concrete beams. The evaluation of the ductility of reinforced concrete beams is very important, since it is essential to avoid a fragile collapse of the structure by ensuring adequate deformation at the ultimate limit state. One of the procedures used to quantify ductility is based on deformations, namely, the plastic rotation capacity. From the many researches, the coefficient of redistribution is depends on the relation between the stiffness and the plastic rotation capacity at the critical regions. Significant differences exist among various design codes on the previous for moment redistribution bases on the approximate ductility of structures and provide empirical rules for moment redistribution. A nonlinear finite element analysis program named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used to evaluate the ultimate strength and degree of moment redistribution.
An experimental and analytical research on moment redistribution in reinforced concrete continuous beams
Published in European Journal of Environmental and Civil Engineering, 2023
Mehmet Safa Aydogan, Cem Aydemir, Guray Arslan
RC continuous beams are one of the most frequently used structural forms among the statically indeterminate systems. RC continuous beams, whose usage areas are quite wide, can offer different advantages in many respects. They make it possible to increase the structural rigidity and integrity with their existing potential. Additionally, because of the structural redundancy, they can provide moment redistribution, allowing for the use of the available reserve strength (Abdallah et al., 2020). The moment redistribution is defined as the migration of bending moments from the sections that have reached flexural capacity to the sections that have not yet reached flexural capacity in statically indeterminate systems. Moment redistribution allows for flexibility in the reinforcement arrangement of an RC system, and this phenomena is particularly helpful for practical design (Scott & Whittle, 2005). Another advantage of the moment redistribution is that it permits economical design due to the reinforcement savings it provides. Considering the moment redistribution, the reinforcement bars in the sections that will reach their bending capacity early are reduced and the reinforcements are saved. By reducing the reinforcement concentration, it is ensured that the compaction of concrete becomes better and the bond performance between the reinforcement and the concrete increases. Especially, this is important in the beam–column joints. Considering the moment redistribution, as well as executing an economical design, since the reserve capacity of the material is fully utilized, a more accurate and realistic design in terms of engineering is performed. In addition, the economic design conception may be important if the ratio of live load to dead load is larger (Celep, 2015).
Review of near-surface mounted FRP plates in the strengthening of continuous flexural members and bond behaviour
Published in Australian Journal of Civil Engineering, 2018
Rebecca Gravina, Hasret Aydin, Phillip Visintin
In reinforced concrete flexural members, moment redistribution refers to the ability to redistribute moment with the onset of plastic deformations, at flexural cracking and particularly after steel yielding as load is increased. The commonly tested symmetrical two span flexural members, as shown in Figure 4(b), can be simplified as a propped cantilever, isolating the member to a single centrally loaded span of a single hogging region at the internal support, and a single sagging region at midspan.