Structure Analysis on Artificial Reefs

Most of the artificial reefs that have been developed in the world are the concrete structure. Regarding economical and practical consideration of artificial reefs, Indonesian government - Ministry of Marine Affairs and Fisheries - has proposed a new material to make an artificial habitats including artificial reefs made from polypropylene plastics (PP). However, diminishing approximately 80% of the weight structure compare to concrete structure has created new challenges to maintain the underwater structure with similar function. Moreover, the use of less weight material for artificial reefs structure will have impact on the structure responses.The structure responses due to sea bottom current and tidal stream velocity have been evaluated at several conditions. Dynamic pressure calculation was applied gradually as external load from a simple part to whole complex structure. Stresses and strains occur at some nodes as the structure critical area, within the same time frame, displacement of its elements describe physical characteristic response. Boundary conditions was encastred the sinker- bottom structure (U1 = U2 = U3 = UR1 = UR2 = UR3 = 0). In conclusion, for input of sea bottom current velocity u = 0.2 m/s the results for maximum stress are below the material’s yield stress hence its elasticity is relatively adequate to prevent permanent deformation. The result also showed some critical part of the structure that has high value on stress should be consider as the current velocity increase. Moreover increasing input and frontal area will significantly affect the drag force which will add load on the structure.