Behavior of composite Girders Strengthened with CERP products
ماجد عذاب جابر, نمير عبد الامير علوش
كلية الهندسة-جامعة بابل · العراق
Composite girders consisted of concrete deck slab connected with two steel I-beams by steel headed studs connectors is the scope of the present investigation. This type of construction is widely used in civil engineering projects especially in bridges. The present study aimed to investigate the structural behavior of such constructions. For this purpose the study was conducted by both experimental and theoretical parts.In the experimental part, nine models of composite section were constructed as test samples. The concrete deck slab was connected to the steel I-beams by headed steel studs welded to the top flanges of the steel I-beams. The test samples were designed to test and failed in flexure. The dimensions of the deck slab are (1000×2000×70mm: width×length×thickness), while the type of each I-beam is (IPE 140) with length of (2000 mm). Each test sample contains two steel I-beam; they were positioned at distance of (250 mm) from the width edges of the concrete slab.Eight of the nine samples were loaded monotically and one sample was tested with repeated load.The test samples were classified depending on the variable parameters into the following groups: (1) Control sample. (2) Distribution of shear connectors (two samples). (3) Number of shear connectors (one sample). (4) Type of loading (repeated load), (one sample). (5) Type of concrete reinforcements (CFRP bars), (one sample). (6) Strengthening by CFRP sheets (three samples).Three Push-out samples were constructed and tested to determine the properties and behavior of the studs. The behavior of the studs was conducted by getting load-slip curves. v In the theoretical part, the tested samples were numerically modeled and then analyzed using the finite elements method. The numerical models were carried out in three dimensions by software package (ANSYS 12.1, 2009).Verification for the numerical results was done by comparing them with the experimental results.A parametric study was done using verified numerical models to investigate the effect of the following: (1) Grade of concrete of the deck slab(35, 45, 55 (control sample), 65, 75) MPa. (2) Grade of steel of the I-beam(A36, A500/Gr.B, A529/Gr.50 (control sample), A913/70). (3) Number of shear connectors (9, 13, 19 (control sample), 37, 74) and case of full-bond between steel and concrete components. (4) Level of repeated load (46% (control sample), 65%, 80%) from the ultimate load.The results of the study indicate that the general trend in ultimate load is to increase with (increasing of shear connectors, strengthening with CFRP sheets, increasing compressive strength of concrete, increasing grade of the steel beams). However, the most effective parameter is the number of shear connectors.Strengthening bottom face of concrete slab and bottom face of the bottom flanges of the steel beams by CFRP sheets slightly increases the ultimate load values by without considerable enhancement in the deflection and slip values. The percentage difference of the ultimate load for the samples strengthened with CFRP sheets is (4-9) %.In addition to that the adopted finite element modeling in general overestimates the ultimate load in comparison with the experimental results. The deviation is only in the range from (0%) to (5.6%)