Shear Behaviour of Keyed Joints in Precast Concrete Segmental Girder Bridges
Speaker: Dr Xiangming Zhou (周向明)
Senior Lecturer in Civil Engineering Design
Brunel University London
Abstract: Precast concrete segmental box girder bridges (PCSB) have become more and more popular in construction resulted from the demand of an economical and safe design, fast, versatile and practical construction, and excellent serviceability of concrete bridges. The structural behaviours of PCSBs are largely dependent on the behaviour of the joints between segments. The current practice is to use small keys that are usually unreinforced, distributed over the height of the web and the flange of concrete segments and these keys can be dry or epoxied. A series of keyed joints, dry or epoxied, single- or multi-keyed, were tested under direct shear to investigate their shear behaviour for the purpose of assessing reliability of the relevant shear design formulae of current design code, namely the AASHTO (American Association of State Highway and Transport Officials code). In addition, numerical analysis models were established for both dry and epoxied keyed joints based on ABAQUS finite element code to investigate their structural behaviour under direct shear. The concrete damage plasticity model along with the pseudo-damping scheme were incorporated to analyse the system for microcracks and to stabilize the solution, respectively. The numerical model is calibrated by full-scale experimental results from a range of sources. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agree reasonably well with experiment results. The validated numerical model was then employed for parametric study on factors affecting shear behaviour of keyed dry joints, in this case confining pressure, thickness of epoxy layer, modulus of elasticity of epoxy, tensile strength of concrete etc. It has been found that AASHTO’s shear design formula underestimate shear capacity of single-keyed dry joints but tends to overestimate shear capacity of multiple-keyed dry joints due to accumulated imperfections between the male and female parts of the joints which increases with the increases in the number of keys. In addition, for dry joints shear capacity predicted by AASHTO diverges from that predicted by numerical analysis at high confining pressure because the contribution of friction in the total shear capacity reduces with the increase in confining pressure. Hence, it is recommended to reduce the friction coefficient used in AASHTO code when high confining pressure is applied. Moreover, the propagation of inclined crack is arrested at high confining pressure due to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate. For epoxied joints, thickness of epoxy layer and modulus of elasticity have little effects on their shear behaviour while tensile strength of concrete does significantly affect their ultimate shear capacity. Therefore a better prediction of concrete tensile strength will result in a better estimation of shear capacity of epoxied joints in PCSB.
Bio： Dr Zhou is a Senior Lecturer in Civil Engineering Design at Department of Mechanical, Aerospace and Civil Engineering, College of Engineering, Design and Physical Sciences at Brunel University London, the United Kingdom. Prior to joining Brunel in October 2008, he was a lecturer and then senior lecturer at University of Greenwich, UK. Before moving to the UK, he did post-doctoral research at Hong Kong Polytechnic University and Hong Kong University of Science and Technology, respectively. He received his BEng in Civil & Structural Engineering and MEng in Structural Engineering both from Tongji University, and his PhD in Civil Engineering from Hong Kong University of Science and Technology. His research interests include low carbon and energy efficient cementitious materials, advanced concrete technology such as extrusion, testing and modelling restrained shrinkage cracking of concrete, application of nanotechnology for concrete, seismic testing, analysis and design of steel-concrete composite high-rise building, performance-based multi-hazards mitigation of building structures under extreme loadings, precast concrete segmental bridges etc. He has been Principal Investigator of research projects funded by UK Engineering and Physical Science Research Council, European Commission 7th Framework Programme, European Commission Horizon2020, UK Royal Academy of Engineering etc. He has authored/co-authored 90 technical papers in conferences and journals such as Journal of Materials in Civil Engineering ASCE, Journal of Engineering Mechanics, ASCE, Journal of Bridge Engineering ASCE, ACI Structural Journal, ACI Materials Journal, Cement & Concrete Research, Cement & Concrete Composites, Construction and Building Materials, Engineering Structures, Engineering Fracture Mechanics, RILEM Materials and Structures, Journal of Earthquake Engineering, Smart Materials and Structures etc. He received the 1st class Natural Sciences Award by Ministry of Education, China in 2006.
报告时间及地点： 12月17日下午3:00，综合3号实验楼3楼会议室
大连理工大学国际化基金项目资助
