Abstract: An indirectly prestressed concrete roof-ceiling construction is a prefabricated element for constructing large-span industrial buildings. The construction includes a distinctly wide and thin concrete soffit plate and an upper concrete girder of an inverse “V”-shaped cross section, interconnected by slender steel pipe-rods that are used to stabilize the upper girder against lateral buckling and to prevent the plate and the girder from getting closer or further away from each other. Prestressing of the soffit plate causes compression in the upper girder which passively (indirectly) pushes the ends of the construction, acting on some eccentricity over the center of gravity of the cross section, causing rotation of its ends, bending in that way the soffit plate upwards. There are two efficient methods of prestressing these constructions.

Abstract: A doubly prestressed roof-ceiling construction with grid flat soffit for extremely large-span is a prefabricated element intended for assembling roofs of extremely large-span buildings with a flat soffit. The construction includes a grid soffit construction and an upper concrete girder of a modified “T” shape or of an inverse “V”-shaped cross section, interconnected by slender steel pipe-rods that stabilize the upper girder against lateral buckling. The empty openings within elements of the horizontal grid are fulfilled with plates wherewith a flat soffit is achieved. The construction is prestressed by the double prestressing. The grid-soffit is prestressed centrically and the upper girder is prestressed by a wedge at the midspan.

Abstract: A prestressed, roof-ceiling construction with flat-soffit for constructing an industrial large-span building with a bearing plane-space by assembling pre-fabricated elements. A problem of constructing flat-soffit, finished ceilings in large-span buildings is solved whereby besides an aesthetic ceiling look, the heating volume is reduced, ventilation is ensured and an isolated loft space is provided through which all kinds of installations can be guided. The construction includes a wide and thin concrete plate with a two-part upper, steel construction, interconnected by vertical elements. The construction is twice prestressed by two independent methods. The soffit concrete plate is prestressed centrally in the mould and after the plate concrete is hardened, the upper steel construction is prestressed by pushing apart, at the midspan, the steel separated halves which are then connected.