Analysis and enhancements to bollard designs

• Main Author: Yip, Kangli.
• Other Authors: Zhao Zhiye
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Transportation
• Online Access: http://hdl.handle.net/10356/15875
• Institution: Nanyang Technological University

This final year project studied the vehicle and bollard collision process using finite element simulations. The type of bollard used in the simulations was the Land Transport Authority Type B concrete bollard on pavements in the civic district. The passenger car was modelled as a block of hollow high strength steel. When any of the finite elements in the bollard had a tensile stress of -25 x 106 Pa, failure in the form of element deletion would occur. For the finite elements of the passenger car, failure in the form of element deletion would occur when any of the elements had a strain of 0.12. The passenger car, which was set to travel at 15 km/hr, 50 km/hr and 95 km/hr, had full frontal collisions with two different models of bollard, one modelled with a fixed base and another modelled with a slab cast beneath. Ansys LS-Dyna was used to build up all the models required for the simulations and LS-Dyna Version 970 was used as the solver to yield results. LS-PREPOST was used to display the results of the simulations, and the total simulation time for each collision was 0.1 s. From the three impact speeds, the values obtained for analysis were the maximum x displacement, maximum effective strain and maximum von Mises stress. These maximum values were then grouped into two sets of data, each belonging to one of the two bollard models. For every one of the three impact speeds, a comparison was done to compare the differences between the two bollard models’ maximum x displacement, maximum effective strain and maximum von Mises stress. The bollard model in the fixed position showed greater x displacement when the collision speeds were high, 50 km/hr and 95 km/hr. But in the low speed collision of 15 km/hr, the x displacement for the bollard model in the fixed position had a lower value. The effective strain and von Mises stress for the bollard model in the fixed position were greater than the bollard model cast with a slab beneath for the collision speeds of 15 km/hr and 50 km/hr. But for the collision speed of 95 km/hr, the effective strain and von Mises stress for the bollard model in the fixed position was less than the bollard model cast with a slab beneath. The results of this project can aid traffic planners in designing roads and pavements more effectively; it also serves as a preliminary study for future finite element analysis in vehicle and bollard collision.