Mechanical Properties of Full-Scale Prestressed Concrete Beams with Thin Slab after Exposure to Actual Fire

Table 3

Loading process for hollow slab beams.

Step	Description
1	Deadweight (including distributing beam and jack deadweight). The load will last for 15 minutes to eliminate the inelastic deformation of the beam end support
2	Preload, load directly to 30% of the calculated ultimate load, last for 5 minutes, and then unload to zero. Force-control mode is adopted. The main purpose is to further eliminate the inelastic deformation of the loading system and verify the reliability of the loading system
3	Under formal loading, the ultimate load of hollow slab beams is calculated by 10 stages, and the ultimate load of hollow slab beams is calculated by 10% for each stage. Each step loading lasts for 5 minutes and force-control mode will be adopted.
4	After 100% ultimate load, unloading is carried out, and then four stages of secondary loading to 100%. Finally, the hollow slab beam is destroyed by intensive loading. The ultimate load of each stage is calculated by 5% ultimate load. Each step loading lasts for 5 minutes and force-control mode will be adopted
5	If the deformation of all hollow slab beams cannot converge with time, that is, the deformation cannot stop, it means that they have entered the ultimate load-bearing state, immediately stop loading, record the corresponding data and unload