Factors affecting moment redistribution at ultimate in continuous beams prestressed with external CFRP tendons

Abstract

Please cite this article as: Lou, T., Lopes, S.M.R., Lopes, A.V., Factors affecting moment redistribution at ultimate in continuous beams prestressed with external CFRP tendons, Composites: Part B (2014), doi: http://dx. Abstract: A numerical investigation of redistribution of moments in continuousconcrete 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 ε t (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.

Moment redistribution versus neutral axis depth in continuous PSC beams with external CFRP tendons

“…As FRP composites are brittle material, the ability of FRP reinforced or strengthened concrete beams to redistribute moments is often limited [17][18][19]. Such limitation can be effectively overcome by providing longitudinal non-prestressed steel in PSC beams with external FRP tendons [20,21].…”

“…The effect of prestress level (15%-75% of the tensile failure strength of FRP tendons) and load pattern (symmetrical and unsymmetrical loads) on global redistribution behaviour of these beams was revealed [20]. More factors influencing moment redistribution in continuous PSC beams with external CFRP tendons were also examined [21]. Of various parameters investigated, the difference between the non-prestressed steel areas at the critical sections was found to be the most critical [21].…”

“…More factors influencing moment redistribution in continuous PSC beams with external CFRP tendons were also examined [21]. Of various parameters investigated, the difference between the non-prestressed steel areas at the critical sections was found to be the most critical [21]. However, the impact of this parameter on the global redistribution during loading has not been analysed.…”

Neutral axis depth and moment redistribution in FRP and steel reinforced concrete continuous beams

“…The moment redistribution behaviour of other typologies of members may be quite different from that of reinforced concrete beams as examined in this study. For example, in externally posttensioned members, the moment redistribution by FRP tendons can be considerable and comparable to that by steel tendons [24,25].…”

Time-dependent assessment and deflection prediction of prestressed concrete beams with unbonded CFRP tendons

“…Bonded FRP tendons may lead to rupture failure of the beams [3,4], while the use of unbonded tendons is an effective and economical solution to prevent FRP rupture [5]. Extensive studies have been conducted to assess the short-term behavior of concrete beams with internal [5][6][7][8] or external [9][10][11][12][13] unbonded FRP tendons.…”