Impact Proof Preliminary Design for the Marine Biology Station in Dichato

Abstract

To the North of the city of Concepción in the South-West of Chile, lies the town of Dichato. It is situated on the south-eastern side of Coliumo Bay. The Universidad de Concepción (UdeC) owns a marine concession in this bay, which includes a section of beach and sea for a Marine Biology Station (EBMD), belonging to the Faculty of Natural and Oceanographic Sciences. The objective of the EBMD is to provide research and educational support in the field of marine sciences. The EBMD concession consists of several onshore buildings with research and educational facilities, some of which are unfinished or damaged due to the Maule 2010 earthquake of magnitude Mw 8.8. Furthermore, there are remains of an old jetty for the docking of a Marine Biology vessel, which was also destroyed in 2010. Thus, UdeC is interested in redeveloping the EMBD, as there is no location for mooring of the vessel and transhipment of goods, as well as incomplete construction or use of several onshore facilities. To solve this problem, as well as to stimulate local authority interest in funding of the redevelopment of the EMBD, a design proposal is made. First the required functions, with as primary function mooring, and the in-situ conditions are investigated, leading to a Program of Requirements. Five design alternatives are established and weighed in a Multi- Criteria and Cost-Benefit Analysis, which leads to the conclusion that the Traditional option is most suitable, due to vast Chilean experience with the type of design and limited costs. From the Program of Requirements it is decided to focus on the offshore aspects of the design solution, in this case the jetty and the breakwater. The design of the jetty is carried out according to the Chilean design codes, and using the structural analysis and design program ETABS, which can incorporate seismic loading. The final design of the jetty includes a concrete deck on a steel frame, with steel piles embedded in the rock in a Marco Duplas (inclined) configuration to resist lateral loading. All elements are tested for structural soundness. The breakwater, on the other hand, is designed through a combination of wave modelling using statistical methods and DELFT3D; and a crest height and stone dimension analysis using BREAKWAT3.0. The upgrade of an existing unfinished building and the pavement are treated in lesser detail. For all elements of the EBMD upgrade, resilience is taken into account as a primary factor in extreme impact design, focussing on allowing structures to have a quick recover capacity, since it is not feasible to design coastal structures to resist impacts like large-scale earthquakes and tsunamis. The damage to the designed elements in the case of a repeat of the Maule 2010 earthquake and tsunami is analysed in an Extreme Impact Evaluation. A range of hazards, including several modes of structural failure of the jetty and breakwater, as well as relevant geohazards for the site, are classified according to level of risk. Mitigation measures are suggested as well. Finally, following a more detailed cost breakdown and a construction timeline, it is concluded that the proposed design solution is feasible within a construction time of 35 weeks and estimated costs of 450 mil CLP. The construction of the jetty and breakwater allows the EBMD to carry out its scientific and academic research safely and more efficiently, whilst also limiting damage and incorporating resilience in the event of large-scale earthquakes and tsunamis.