A methodology is developed for optimal structural topology design subject to several performance constraints. Eight-node solid elements are used to model the initial structure, which is a uniform solid block satisfying the boundary conditions and subjected to external loading. The Young modulus of each solid element or group of elements is used as redesign variable. A minimum change function is used as an optimality criterion. Performance constraints include static displacements, natural frequencies, forced response amplitudes, and static stresses. These constraints are treated by the large admissible perturbation methodology which makes it possible to achieve the performance objectives incrementally without trial and error or repetitive finite element analyses for changes in the order of 100-300%. Thus, the optimal topology is reached in about four to five iterations, where each iteration includes one finite element analysis and setting of an upper limit for the value of the modulus of elasticity to produce a manufacturable structure. Several numerical applications are presented using three different benchmark structures to demonstrate the methodology and the impact of performance constraints on the generated topology. Keywords Topology • Performance • Optimization • Structural redesign • Large admissible perturbations 1 Background The goal of structure optimization is to improve the performance of any given objective set in a structural environment

Similar to land-based facilities, marine and offshore assets can be exposed to outbreaks of infectious diseases. This is exemplified by the recent COVID-19 outbreak which has had a significant impact on both personnel health and normal operations of the assets. The occurrence and transmission of infectious diseases on marine and offshore assets can, however, be mitigated by appropriate physical arrangements on board and having operational procedures in place. This paper addresses the former. The effectiveness of operational measures can be significantly increased if infectious diseases are considered at the asset’s design stage. ABS has identified a lack of available technical guidance regarding physical arrangements that can help make marine and offshore assets safer for crews and reduce the spread of infectious diseases, such as COVID-19. This paper presents the best practices and recommendations for physical arrangements drawn mainly from the recognized standards for land-based medical facilities and applied to marine and offshore assets. The recommendations focus on specific spaces inside the accommodation block, their number, location, layout, ventilation, and interior surfaces. Isolation cabins with their associated anterooms are proposed as the most reliable way of isolating suspected or confirmed cases of an infectious disease from the rest of the personnel on board. Negative pressure, independent exhaust system, and easy to clean surfaces that are accessible and resistant to deterioration from frequent cleaning and disinfection are effective measures in containing the transmission of infectious diseases that are spread through the air or direct and indirect contact. The paper also emphasizes the need to promote segregation of the visitors from crew and passengers by providing designated spaces for the visitors and gives recommendations on the communication equipment needed for receiving medical advice from land-based medical specialists. If properly implemented and if augmented with robust operational measures, physical arrangement measures have the potential to significantly improve the safety of the crew, passengers, and visitors, as well as minimize the negative consequences of disruptions to normal asset operations.