In this paper, Object-Oriented SEA (OO-SEA) modeling approach is presented. OO-SEA is based on a new reusable, flexible and modular modeling approach, and it is an alternative to the traditional manual SEA model creation process. Common characteristics of components in engineering structures are represented in a standard object library to increase the modeling efficiency. Primitive objects are grouped together to create more complex objects. In comparison to manual subsystem-by-subsystem SEA model creation, which is analogous to old-fashioned line-by-line programming, this new approach exploits the object-oriented software design (OOD) concepts, which are well established in modern computer science and engineering. The OOD concepts such as objects, class, class hierarchy, abstraction, encapsulation, inheritance and modularity are directly applied. The end result is a fast SEA model building approach and an expert model creator which brings standardization and quality by using a collection of best practices in a library, and also increases the efficiency by recycling modules that are well-accepted by the experts. The information saved in the module library is targeted to match the resolution needed for SEA models, thus eliminating excessive geometric details. A major departure from current SEA geometric representations is the implementation of continuous parametric functional forms for the definition of curves, surfaces and volumes in the 3D modeling space. The objects are dropped into the model in their canonical forms and later modified dynamically through their attributes. Examples from applications are presented to clarify and demonstrate the implementation of the OO-SEA concepts.