Concrete Filled Unplasticized Poly-Vinyl Chloride (UPVC) Tubes as Column

In present study, a stress–strain model for concrete subjected to compression and confined with unplasticised poly vinyl chloride (UPVC) tube is proposed. To develop this model, total eighteen specimens of concrete filled UPVC tubes (CFUT) having different geometrical properties were tested. To obtain the specimens, UPVC pipes of class 3, 4 and 5 (IS: IS: 4985-2000 (Reaffirmed 2005) “Unplasticized PVC pipes for potable water supplies- specification. Bureau of Indian Standard, New Delhi, India-2000 IS: 4985-2000 (Reaffirmed 2005) “Unplasticized PVC pipes for potable water supplies- specification. Bureau of Indian Standard, New Delhi, India) with nominal/working pressure of 0.6, 0.8 and 1.0 MPa (87, 116 and 145 psi) having diameters of 160, 200 and 225 mm (6.3, 7.87 and 8.86 in.) were taken and cut into 800 mm (31.5 in.) length. Internal hydrostatic pressure test were conducted to obtain the confining pressure of UPVC tubes. M30 and M40 grades of concrete were designed as per IS: 10262-2009 (IS: 10262-2009. Concrete mix proportioning-guidelines. Bureau of Indian Standard. New Delhi, India) to fill the tubes. All the specimens were compressed by application of load on concrete core only, to obtain load–displacement variations and associated mode of deformation. All the specimens were failed by development of shear cracks and macrocracks with slight bulging. A finite element model is developed using proposed stress–strain variation of concrete confined with UPVC tubes to simulate the axial compression of CFUT specimens. On the basis of obtained results, effect of variation of diameter to thickness ratio (D/t) on the failure stress of confined concrete is obtained and discussed with an empirical relationship. Load capacities of different specimens obtained using the proposed Finite Element model and some models available in literature are presented, compared and discussed. It may be concluded that the proposed model is capable to estimate the load capacity and mode of deformation of concrete filled UPVC tubes (CFUT) subjected to axial compression.