Punching shear resistance of lightweight concrete two way slabs strengthened with CFRP strips

Muthanna Journal of Engineering and Technology

Volume (3), Issue (2), Year (30 December 2015), Pages (58-68)


Research Article By:

Mazen D.Abdulah

Corresponding author E-mail: mazend_81@yahoo.com


The aim of this study is to investigate the experimental behavior of reinforced concrete light weight concrete two-way slabs stiffened by CFRP strips to punching load and compare the results with the finite element model results. The experimental program includes testing a total of 14 slabs (800 x 800 x 70) and (800 x 800 x 90) mm. The slabs are divided into two groups; each group consists of seven slabs. In each group of seven slabs, one slab was left without strengthening as a reference slab, while each slab of the remaining six slabs has a different CFRP distribution. The effect thickness of slabs and shape of the CFRP distribution on the punching shear strength of slabs are studied. All slabs in this study are designed to fail in punching shear. During the test, the slabs are simply supported on all four edges and loaded centrally by a (75 x 75) mm column. Load deflection curves, cracking patterns and effect of variables on the test results are discussed. Experimental results showed that, the CFRP strengthening increased the ultimate punching load of the slabs by (9-26) %, also the first cracking load increased by (38-141) %. The strengthened slabs showed less deflection during loading by about 24% compared to the non- strengthened slabs. Increasing the slab depth gives changes to the slabs punching strength. The slabs are modeled by three dimension finite elements and non-linearly analyzed by the ANSYS program where the concrete is represented by the eight nodes solid element (solid 65) and the CFRP strips are represented by (3D shell 41) with a perfect bond between the CFRP and concrete slabs. Finite elements results showed a comparable results to laboratory tested slabs and the difference is not more 12% in ultimate load.

Keywords: CFRP, solid 65.

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