Performance of polypropylene fiber reinforced concrete-filled UPVC tube columns under axial compression

摘要

This paper aims to study the behavior of UPVC-confined columns reinforced with polypropylene fibers under axial compression. A sum of 42 column specimens has been tested, including 18 Unconfined Concrete Cylinders (UCC) and 24 confined Concrete-Filled UPVC Tube (CFUT) specimens. To investigate the sensitivity of these columns to various parameters, different levels of material volumes have been used, which include two concrete strengths of 40 and 50 MPa, two tube grades of PN6 and PN10, and three polypropylene fiber content of 0, 1 and 3 kg/m(3) of the concrete mixture. The influence of each variable on the ultimate strength, ductility and confinement effectiveness of the specimens have been examined. Similar test data on the PVC-confined specimens have been collected from the literature, and along with the test data of the current study, are used to determine the influence of various parameters on the response of composite columns. Finally, a model for the prediction of ultimate strength of PVC composite columns is proposed using two different coefficients: one for UPVC tube and one for confined concrete. The confined concrete coefficient is calculated from the database by considering numerous regression models that showed strong dependency to column diameter to pipe thickness ratio (D/t), UPVC pipe tensile yield stress to concrete compressive strength ratio (f(y)/f(c)') and the fiber content. It was found that polypropylene fibers slightly increase the column strength up to a certain volume fraction, after which strength usually experiences a decline. Ductility, on the other hand, increases considerably with fiber volume fraction. UPVC tubes have a positive effect on both ultimate load-bearing capacity and especially ductility of the column. Though not as strong as their steel counterparts, they present certain benefits such as low cost and environmental resistance that can be a determining factor in certain practices. (C) 2019 Elsevier Ltd. All rights reserved.