土木与环境工程学报

The length to diameter ratio (L/D), loading rate, size and specimen geometry are significant factors that affect the compressive strength of high performance concrete (HPC) under dynamic loading conditions. A numerical study is carried out on selected conventional laboratory size prismatic specimen between the slenderness ratio 0.5 to 3.5 to evaluate the variation of stress-strain by performing finite element (FE) solving procedure. The results show that the maximum stress is found in specimen with slenderness ratio one. The stresses gradually decreased with the increase of the value of slenderness ratio (from one and above). The HPC dynamic strength dependency on strain rate and L/D is correlated using multiple regression equation. The accuracy of the predicted regression equation is verified with published experimental data and the result is 3% and 25% deviation under the applied strain rate 100 and 300 s -1 respectively. The regression equation yields significant result within the limited stain rate 150 s -1 . The size effect analyses also satisfy existing published experimental data of concrete.

Ships, ship-shaped offshore structures, land-based structures and aerospace structures typically consist of various curved beam and plate components. An important issue is how to manufacture and construct systems correctly and accurately when their variously shaped curved beams and plates display structural nonlinear behaviour. Multi-point forming is a general process that can be used to form variously shaped curved plates and beams. It has been difficult to apply the integrated systems to thin and/or thick metal plates and beams that have the characteristic of non-linear structural mechanics, such as nonlinear behaviour when loading is applied to the plates. The aim of this study was to derive a simplified numerical calculation based on the formulation of a nonlinear integral equation and a mathematical solution, to predict the nonlinear elastic deflection, load profile and elastic foundation of curved plates or/and beams during the early stages of the advanced manufacturing process of plate and beam formation. The validity of the method is demonstrated through simulations of the proposed numerical approach with experimental results.

The increasing contamination of soil by used motor oil is very common and of great concern to our society because of the possible harm that it can cause the environment. Remediation of contaminated soil is the application of suitable techniques in the removal of contaminants present in soil. Contaminants like heavy metals and aromatic hydrocarbons are found in used motor oil as a result of reactions in motor engines occurring during use of motor oil. The study determined the effect of soil washing using detergent as a remediation technique for soils contaminated with used motor oil. Detergent solution was added to soil contaminated by used motor oil. After twenty four (24) hours, the concentration of heavy metals (Cr, Zn, Cd, Pb, Ar, and Cu) and Polyaromatic Hydrocarbons (PAHs) in the soil residue were determined. A control experiment was carried out for a soil sample with no used motor oil added to it. The control experiment indicated that PAHs were not present in the soil before introduction of used motor oil. The removal rate of contaminants for this technique was 63.8% for Zn, 100% for Ar, 52.9% for Cd, 67.3% for Cr, 89.2% for Pb, 43.4% for Cu and 95.6% for PAHs. Soil washing was found to be effective in remediation of soils contaminated by low concentrations of used motor oil.