Shear capacity tests of PC crane beams in uncertain prestressing tendons anchorage conditions

Assessment of the shear capacity of existing concrete structures is a layered problem. Especially when it comes to prestressed concrete members with a low transverse reinforcement ratio. In addition, in the case of structures built many years ago, there is usually a lack of detailed information on the materials and technologies used, which makes it very difficult to assess their safety [1-4]. In many old prestressed concrete structures, the anchorage area has not been secured against corrosion at all or has been improperly protected, resulting in increasingly limited reliability of the cable anchorage over time [5]. Hence, the question of the behaviour of this type of structural elements in the extended lifetime is raised more and more frequently. Research on the post-tensioned, precast crane beams after more than 50 years of exploitation is presented in the paper. Such structural elements were common in Poland and neighbouring countries at the time, so evaluation of their durability and safety became an issue affecting thousands of industrial buildings [6]. The tests presented in this paper aimed to determine the shear capacity of the elements with a diversified shear span-to-depth ratio under conditions of loss of part of the prestressing force due to failure of the cable anchors. Previous research on the transmission lengths of grouted Freyssinet 12ø5 cables at the time of loss of anchorage-which are essential for computational shear analyses-has been reported in [7] and [8]. 2. EXPERIMENTAL PROGRAMME The subject of the research were precast, post-tensioned concrete crane beams that were disassembled from the industrial hall after almost 60 years of use [5,9]. The beams with an I-section of 800 mm in height and a modular span of 6.0 m were tested. They were prestressed with five rectilinear 12ø5 mm Abstract Research on the shear capacity of posttensioned, precast crane beams after more than 50 years of exploitation is presented in the paper. The tests simulated a