Loading...

Compressive Performance of Concrete Confined with UPVC Pipes

Mohammad Askari, Shahram | 2020

168 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 54998 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khaloo, Alireza
  7. Abstract:
  8. This study presents an experimental and numerical investigation on the compressive behavior of a new type of composite column which consists of both solid and hollow concrete-filled UPVC tube with and without GFRP wraps.Composite construction has been often more economical than traditional concrete construction, because this system realizes the most effective use of concrete, and composite members in the structural system.The enormous potential of using plastic tubes in composite systems will be illustrated by this research. It is an economical type of column in construction.This research aims to study the behavior of UPVC-confined columns under axial compression. A sum of 132 specimens are categorized into 4 groups in addition to the ordinary concrete specimens which have been cast and tested under the action of monotonic compressive loading. The tests include Unconfined Concrete Cylinders (UCC) and confined Concrete-Filled UPVC Tube (CFUT) specimens with extra replicates. To investigate the sensitivity of these columns to various parameters, different levels of material volumes and sizes have been used, which include two concrete strengths of (strength class) 40 and 50 MPa, three tube grades of PN6 and PN10 and PN16, and three polypropylene fibers contents of 0,1 and 3 kg/m3 of the concrete mixture, and three expansive material contents of 0,%1 and %2 of the cement mass , and four cases of height to diameter (H/D) 2, 3 , 4 and 6 by pipe diameter 110 mm , with or without hole in column and two layers of GFRP.The influence of each variable on the ultimate strength, ductility and confinement effectiveness of the specimens have been examined.It was demonstrated that adding expansive agents enhanced the load-carrying capacity and the ductility of columns through providing a better tri-axial state of stress in the concrete core. Moreover, by an increase in the values of aspect ratio both peak load and its corresponding axial strain were decreased. This reduction was lower in GFRP-confined specimens, which is attributed to the confinement effects of GFRP wraps. Furthermore, an approximately 40 percent increase was observed in the values of peak load for specimens confined with GFRP wraps. Generally, concrete core removal in the hollow specimens results in slightly higher average compressive stress. This observation can be attributed to the variation of stress values across the section of solid columns, which was higher in outer parts in comparison with central regions.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 (fy/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.Also, a finite element (FE) simulation was performed using ABAQUS software and the numerical results were validated with experimental tests conducted in the current study. At the end, a parametric study was carried out in order to examine the effects of parameters including the number of GFRP layers as well as the hole diameter size on the performance of these composite columns
  9. Keywords:
  10. Confinement ; Finite Element Analysis ; Analytical Modeling ; Expansive Concrete ; Concrete-Filled UPVC tube ; Ploypropylene Fiber Reinforcement ; Composite Column Strength

 Digital Object List

 Bookmark

No TOC