Experimental tests of two span continuous concrete beams reinforced with hybrid GFRP-Steel bars

Bending moments redistribution in two‐span reinforced concrete beams reinforced with FRP bars based on collected data research

“…Statistical analysis of the degree of redistribution was finally limited to publications, 3,6,8,10,11,14,[16][17][18][19][20][21] in which redistribution of moments from the support to the span was most common (Figure 5a). The degree of bending moments redistribution β for Figure 5a is calculated in span, therefore, β > 0 means redistribution to span.…”

“…One way to reduce beam deflections and increase stiffness while maintaining increased resistance to environmental conditions was to use the additional steel reinforcement in the second layer of reinforcement. This concept was the basis of research programs, 14–17,21 which confirmed a significant reduction in deflections and a beneficial effect on the occurrence of bending moment redistribution.…”

“…; first capital letter "G"-GFPR type reinforcement, second number stands for serries of experimental program, last number ("0", "15", "25") means designed moment redistribution in percentage 15 ; first letter in the notation corresponds to the type of supporting "C"-continuously supported, second letter indicates the type of reinforcement "G"-GFRP, "H"-hybrid, the last digit is a sequential number 14 ; specimens of groups "A" are BFRP over reinforced "B", were reinforced with BFRP but under reinforced, "C" are hybrid over reinforced and "D" are hybrid under reinforced, the last digit is a sequential number 16 ; first capital letter represents type of element "B"-beam, second capital letters stands for type of reinforcement "G"-GFRP, "H"-hybrid, the last digit is a sequential number 17 ; first letter in the notation corresponds to the type of the element "B"-beam, symbols "H" represents hybrid reinforcement at the sagging and hogging region, "CH" stands for CFRP reinforcement at the hogging region and hybrid reinforcement at the sagging region 19 ; first capital letter represents type of reinforcement "B"-BFRP, the second part stands for the stirrups spacing; d/2 and d/3 stand for 120 and 80 mm stirrups spacing, the third part represents the sagging-to-hogging reinforcement ratio and the last part corresponds to the volume fractions of basalt macro fibers 20 ; the first letter indicates that the specimens are beams (B), the next number refers to the top longitudinal reinforcement ratio and the final number describes the bottom longitudinal reinforcement ratio 21 ; first capital letter "B"-beam type element, the last digit is a sequential number.…”

“…In publications, [14][15][16][17]21 the effect of FRP-steel hybrid reinforcement was investigated, depending on the reduced FRP reinforcement degree to the steel reinforcement degree at the bending moment redistribution point (Figure 15). As the lower is ρ f E f /E s /ρ s , the higher is the percentage of steel reinforcement in a given cross-section.…”

“…This is the reason for the significant effect of the bending moments redistribution in the multi-span beams and slabs reinforced with FRP bars. The issue of redistribution in beams reinforced with FRP bars or hybrid steel-FRP reinforcement has already been described in publications, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] but there are still many inaccuracies regarding the adhesion of reinforcement to concrete, degree of reinforcement, modulus of elasticity, concrete compressive strength, shear reinforcement and interaction of all those parameters combined.…”