narrower concept U-plate Concept beam grillage Concept cantilever slab Concept continuous slab Concept diaphragm Concept flat slab Concept folded plate structure Concept hollow slab Concept masonry wall Concept orthotropic plate Concept plate Concept plate Concept plate effect Concept plate structure Concept rib strengthening Concept ribbed slab Concept ribbed slab floor Concept roof deck Concept roof slab Concept roof structure Concept shell Concept shell structure Concept spread foundation Concept wall structure Concept