The experience of retrofit design in using CFRP of building case study of the ramp structure of palm oil mill in South Sumatera

Abstract

This paper was aimed to share our experience in using CFRP in the case of retrofit of the ramp structure in palm oil mill in South Sumatera with a total length of 104 m and a width of 20 m, which consists of the primary beams (30 cm 70 cm) span 8 m, the secondary beams (25 cm 40 cm), and the slabs (thickness 20 cm). This ramp was cracked in the beams and the slabs after the five-year operation. In the first-year operation, no crack was found. However, from the second year until the fifth year, the cracks increased. After investigating in the field, we found a flexure crack in the primary beams, the secondary beams, and the slabs. In the drawing, we found that the bar was a plane bar and the quality of the concrete average was fc' 20 MPa. The Imposed loads for the vehicular traffic were designed with 12 tons. In the next step, we made a static calculation to check all designs. The results from the static calculation were that the capacity of the bar was sufficient, and the deflection was still under the allowed limit. The cracks mostly occurred in the Ramp structure. In the parking area in another building, there was no crack found. Thus the solution for this ramp was repaired the concrete from the cracks then strengthen it using CFRP. Strengthening of the primary beams used two strips of a fiber-reinforced composite or plastic material type with a thickness of 1.2 mm and a width of 10 cm. The capacity of the positive moment and the negative moment would increase the capacity about 64%. For the strengthening of the secondary beams using two strips of CFRP with a thickness of 1.2 mm and a width of 10 cm, the capacity of the positive moment and the negative moment would increase the capacity about 145%. For the strengthening of the thickness of the slabs 20 cm using one strip with a thickness of 1.2 mm and a width of 10 cm, the capacity of the positive moment and the negative moment would increase the capacity about 186%. The use of CFRP as the strengthening of the beams and the slabs was significant in increasing the moment capacity for the beams and the slabs due to the increasing load acting on the structure, thus the structure was still safe to use.