Expanded polystyrene (EPS) blocks (geofoam blocks) used as lightweight fill over a parking structure adjacent to a hospital building to fill 0.6 – 1.5 m elevation gap between the top floor of the parking structure and hospital entrance. In addition, geofoam blocks created a flat roof for parking structure. Geofoam block lightweight flat roof system also contains reflecting pool, planted recreational areas for the patients and visitors and also a drive way for drop off traffic which is around 3500 vehicles a day. Various fill materials such as conventional earth and foam concrete were originally considered. Even though, both of these options were locally available these additional fill weights were not considered in the original design of the reinforced concrete parking structure. Structural system rehabilitation which required an increase of approximately 5% and 21% steel amount of the original design when foam concrete fill and conventional earth fill options were selected, respectively. Subsequently, both of these options were dismissed and geofoam blocks were selected as lightweight fill material which provided significant savings in the total cost of the project and also accelerated the completion time. To quantify the long term performance of the system, elevation survey was conducted after 36 months in operation and compared to that of immediate post construction recordings. The maximum vertical settlement was 0.6 cm that corresponds to 0.45% vertical strain of geofoam blocks which is less than allowable vertical elastic limit strain of 1%.
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