Structural Evaluation of Coconut (Coir) Fiber Reinforced Gypsum Plaster Dome

The historic inner dome and the interior supporting walls of the West Virginia State Capitol Building were found to have structural deficiencies. Several cracks were observed on the interior of the dome structure, and an in-depth investigation revealed that the Capitol dome structure was constructed with gypsum plaster reinforced with coconut fibers, also known as coir fibers. The application of using coconut fiber in the building construction is very rare, and no literature was available about the material behavior as a building construction material when used as reinforcement for plaster. Therefore, due to this scarcity of information, various mechanical material tests and rigorous analysis of their results were performed to understand the structural behavior of the dome structure, the cracking behavior, and to further examine the extent of retrofitting desired. Material samples of coconut fiber reinforced gypsum plaster were directly obtained from the dome structure and tested to evaluate various mechanical properties such as tensile strength, flexural strength, and compressive strength. The results obtained from these tests were directly used to define the material properties of the analytical dome model and became the design basis of the repair.