Heerbrugg design is an extension of an already existing High School building in Heerbrugg, Switzerland. The new building is a B+G+3 story with a structural system consisting of Pre-stressed Ribbed slab, façade columns, and walls. The project involves the design of all structural elements except the foundation. This design includes 14 typical ribs where some are supported totally by walls while others are supported by beams connected to columns through steel connectors. The façade precast columns are also part of the assignment. The Pre-cast, Pre-tensioned ribs are of different of spans with the longest rib having a length of 19.25 m. Most of the ribs support their own weight with additional dead and live loads whereas some others are designed to support walls that support upper stories. The ribs are designed using the usual linear elastic analysis and the support detailing and beam sections are designed using strut-tie-model. The strut-tie-model has also been used for hand calculation checks of finite elements results from our computer modeling.