| Author: | Guo, Jiachen |
| Title: | Structural behaviour of high-strength ring strengthened dowel connections and demountable pavement connections |
| Advisors: | Chan, Tak-ming (CEE) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Pavements -- Design and construction -- Environmental aspects Pavements, Concrete -- Joints -- Maintenance and repair Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxvii, 306 pages : color illustrations |
| Language: | English |
| Abstract: | There is an urgent need for the construction sector to provide innovative solutions to minimise carbon emissions and achieve carbon neutrality. In concrete pavement industry, there are two primary strategies to fulfil this aim including (I) extending the service life of cast-in-situ jointed pavements and (II) promoting the reusability of precast concrete pavement (PCP) systems. As main load transfer devices, epoxy-coated steel dowel bars have been used in pavement load transfer for nearly a century. However, after millions of load repetitions, severe localised crushing failure may happen at the pavement joint surface, thereby shortening the pavement service life. As a result, to improve the durability of jointed concrete pavement systems, one of the main aims of the current research is to optimise the conventional dowel bar connection. Firstly, the existing Friberg's theoretical analysis to describe the compressive stress distribution within the dowel slot was improved by taking into account the elastic deformation of the concrete support and the non-uniform contact stress distribution between the dowel bar and concrete. Through a comparison with the stress data generated from finite element analysis (FEA), the modified analytical method offered a precise prediction in computing the maximum compressive stress at the joint surface and determining the range of compression zone within the dowel slot. The joint-width independent moduli of dowel support were also proposed considering different types of concrete and dowel bar diameters. Then to improve the bearing resistance of the dowel connection embedded into concrete and mitigate concrete crushing failure, a novel high-strength ring strengthened dowel connection was proposed and then assessed through experimental tests and FEA. According to the test data, after incorporating high-strength rings, the dowel connection embedded into concrete exhibited a higher ultimate load and more excellent compressive resistance in contrast to that without the ring part. In terms of FEA, after being validated against test results in terms of failure modes and load-deflection curves, the extended parametric analysis was implemented. By using the data collected from the experimental tests and FEA, under the service limit state (SLS), the relationship between the maximum compressive stresses induced in the high-strength ring and in the normal strength concrete (NSC) block was derived. Then under the ultimate limit state (ULS), analytical solutions to predict the ultimate load of the high-strength ring strengthened dowel connection embedded into concrete were also proposed. Apart from analysing and strengthening the mechanical behaviour of the dowel connection embedded into concrete, to promote the reusability of precast pavement panels, two different demountable pavement connections were also proposed in this research. Based on the load transfer mechanism of the traditional dowel bar connection, an innovative removable dowel bar connection was proposed. To relieve compressive stress concentration, an additional stainless steel ring was employed at the pavement joint surface to expand the contact area between concrete and steel. Test data indicated that the application of the stainless steel ring significantly improved the ultimate load and relieved the strain localisation around the dowel bar. After conducting a comprehensive parametric analysis through FEA, a close linear relationship was found between the ultimate load and the stainless steel ring length, by which empirical equations were derived to predict the ultimate load. Besides, the effect of the stainless steel ring on the compressive stress reduction was also studied by proposing an exponential relationship to link the maximum compressive stress of concrete to the thickness of the stainless steel ring. Another demountable stainless steel bar connection system was also proposed and tested. Owing to a limited contact area between the stainless steel bar connection and concrete, localised crushing failure was observed at the joint surface under vertical load. Therefore, a stainless steel plate was adopted to replace the stainless steel tube and expand the contact surface. According to test data, high ultimate loads and low compressive stress concentration could be achieved. Apart from experimental tests, as the updated stainless steel bar connection system exhibited superior performances in load transfer and mitigating compressive stress concentration, an additional FEA was also carried out to further evaluate its mechanical behaviour. To improve demountability, the design load of the model was defined at the initiation of the bolt shank necking. Based on observed failure mechanisms, analytical methods to predict the design load of each model were finally derived and validated. |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/12296