Oblique and Multi-Directional Random Wave Loads on Vertical Breakwaters

Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.

Quantitative analysis of the protective performance of bicycle helmet with multidirection impact protection system in oblique impact tests

Purpose:The current study aimed to assess the protective performance of helmets equipped with multidirectional impact protection system(MIPS)under various oblique impact loads.Methods:Initially,a finite element model of a bicycle helmet with MIPS was developed based on thescanned geometric parameters of an actual bicycle helmet.Subsequently,the validity of model wasconfirmed using the KASK WG11 oblique impact test method.Three different impact angles(30°,45°,and 60°)and 2 varying impact speeds(5 m/s and 8 m/s)were employed in oblique tests to evaluateprotective performance of MIPS in helmets,focusing on injury assessment parameters such as peaklinear acceleration(PLA)and peak angular acceleration(PAA)of the head.Results:The results demonstrated that in all impact simulations,both assessment parameters werelower during impact for helmets equipped with MIPS compared to those without.The PAA wasconsistently lower in the MIPS helmet group,whereas the difference in PLA was not significant in the noMIPS helmet group.For instance,at an impact velocity of 8 m/s and a 30°inclined anvil,the MIPS helmetgroup exhibited a PAA of 3225 rad/s^(2) and a PLA of 281 g.In contrast,the no-MIPS helmet group displayeda PAA of 8243 rad/s^(2) and a PLA of 292 g.Generally,both PAA and PLA parameters decreased with theincrease of anvil angles.At a 60°anvil angles,PAA and PLA values were 664 rad/s^(2) and 20.7 g,respectively,reaching their minimum.Conclusion:The findings indicated that helmets incorporating MIPS offer enhanced protection againstvarious oblique impact loads.When assessing helmets for oblique impacts,the utilization of larger angleanvils and rear impacts might not adequately evaluate protective performance during an impact event.These findings will guide advancements in helmet design and the refinement of oblique impact testprotocols.