Thin-Walled Open-Section P/C Beams in Fire: A Case Study

The assessment of fire safety in a heavy-duty pre-tensioned simply-supported beam with an inverted V section is presented in this paper. Architecturally-valuable thin-walled beams have been used in Italy for the last forty years in the roofs of large industrial or office buildings. Typically, a series of girders (= secondary beams, with interposed concrete or polycarbonate panels) are supported by other girders resting on columns (= main beams), having different sections (double-tee/inverted-V/channel sections). After several decades since their design and construction based on past code provisions and technologies, a reuse of the building and/or more severe loads often require the beams to be rechecked in fire, even more since these members frequently exhibit severe symptoms of distress, often in the form of longitudinal cracking induced by transverse bending. Albeit rather peculiar for its unusual cross-section, the beam in question offers the opportunity to focus the attention on some general aspects concerning the safety verifications on thin-walled concrete members in fire conditions, and on some peculiarities of past design practice.