| Building structures out of lattices of rigidly connected ribs has many advantages over traditional construction methods which use panels, sandwich cores and/or expensive frameworks. These lattices of rigidly connected ribs are commonly referred to as grid structures and have become an attractive building alternative due to the recent use of composite materials in their construction. Some advantages of grid structures over traditional structures are: high impact damage resistance, high damage tolerance, high bending stiffness, high strength and the potential for automated manufacture.; The introduction of grid structures into industry has been hampered by a lack of understanding of their behavior, especially their behavior in failure space. The focus of this research is to develop a practical working knowledge of how grid structure behave. Of particular interest is the change in grid structure behavior when irregularities are present in the grid structure lattice. Additionally, there is great interest in determining how grid structures can best be repaired and joined together.; In order to answer the above questions, a model of grid structure deformation and failure to general loading conditions was developed. The model includes failure criteria for rib material failure, material failure in areas where ribs intersect, and rib stability failure. The model was developed into a computer code called GridWorks. In the development of both the model and the computer code, attention was given to making solution time as fast as possible. The resulting short solution time makes possible the generation of failure envelopes in failure space for user-specified grid structures. Experimental verification of the model and computer code was performed through a variety of tests on dozens of different grid structure geometries.; Using GridWorks, parametric studies were run on a variety of grid structure types and geometries in order to characterize their behavior in failure space. Studies were performed to determine grid structure strengths, grid structure weaknesses, the effects of empty, soft, hard and rigid inclusions, the effects of missing ribs, the effects of nodal offset, the impact of soft and hard repairs to the grid structure lattice, and the impact of joining grid structures together. |
