Infrastructure Engineering - Research Publications

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Author: Mendis, Priyan × Author: Ngo, Duc × Author: Sofi, Massoud × End date: 2019 × Start date: 2010 ×

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    Ductility Design of Reinforced Very-High Strength Concrete Columns (100–150 MPa) Using Curvature and Energy-Based Ductility Indices
    Kristombu Baduge, S ; Mendis, P ; Ngo, TD ; Sofi, M (Springer Science and Business Media LLC, 2019-12-01)
    The paper aims to develop theoretical expressions for the ductility design of very-high strength concrete (VHSC) (> 100 MPa) columns using curvature and a new flexural energy-based ductility approach. Eventually, the study aims to evaluates the feasibility of VHSC columns for different ductility classes, considering the limitation of providing a higher volume of transverse reinforcement due to possible steel congestion in the construction phase. An analytical program based on the experimental stress–strain relationship of confined VHSC, which is validated using experimental programs on VHSC columns, is used to evaluate the ductility of VHSC columns for different parameters such as axial load ratio, confinement pressure, longitudinal steel ratio, yield strength of transverse steel, cover area and compressive strength of concrete. The theoretical curvature ductility and flexural rotation-based energy ductility of 3200 rectangular columns were evaluated using the analytical program. Using curvature ductility and the new flexural rotation-based energy ductility for different parameters, a regression analysis is carried out to develop expressions for the ductility design of VHSC columns up to 150 MPa. Using the new definition of energy-based ductility, a new expression is developed for limited ductility design of VHSC; and it is concluded that the new approach reduces the required amount of steel confinement due to an increase in the energy ductility of VHSC at higher axial load ratios and higher strengths. The studies show that reinforced VHSC can be used for structures with nominal ductility demands.
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    Behaviour of Pre-Stressed High Strength Concrete Sleepers Subjected To Dynamic Loads
    Javad, T ; Mendis, P ; NGO, T ; Sofi, M ; Fernando, D ; Teng, J-G ; Torero, JL (University of Queensland, 2015)
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    Strain Rates in Pre-stressed Concrete Sleepers and Effects on Cracking Loads
    Taherinezhad, J ; Sofi, M ; Mendis, P ; Ngo, T (RMIT, 2014)
    Pre-stressed concrete sleepers (PCSs) play an essential role in railway track response, performance and safety. Depending on track condition and train speed, PCSs are subjected to high magnitude dynamic loads. These loads can generate cracks, which influence the stiffness, load bearing capability and durability of sleepers. The cracking of PCSs has been reported to be a major problem on a worldwide scale and imposes a costly replacement. This paper presents an investigation on the effects of calculating strain rates on the strength of PCS. By using available measurements, the strain rates are calculated at the rail seat and midspan, locations with a high concentration of stress. The cracking loads are calculated based on the dynamic increase factor (DIF) of concrete and comparison is made with commonly occurring dynamic loads. Results show that the maximum strain rates at both rail seat and midspan are about 0.08 and 0.016 1/s, respectively. The increase of cracking wheel load due to the strain rate effects is about 5 to 26 percent Further, the results are shown to be able to demonstrate the level of concrete damage in the form of cracks due to dynamic loads with very short return periods.