Abstract
To provide an effective basis and reference for applications of prestressed concrete thin‐slab beams after a bridge fire, methods and principles of fire‐resistant design, repair, and reinforcement of such beams were discussed. Taking a simple supported and continuous girder bridge of an expressway in service as a sample, appearance testing and nondestructive testing of the internal structure were carried out. Four representative full‐scale prestressed concrete beams were selected. Through the comparative test of the ultimate bearing capacity of such beams, the laws of the deflection deformation, strain distribution, crack formation, and crack development were obtained. By combining with the finite element simulation and theoretical analysis, the ultimate bearing capacity, complex mechanical characteristics, and breakage feature and failure mechanism of such beams were studied. It was indicated by the results the following: (1) Prestress loss will cause height reduction of the concrete shear zone, which is one of the main reasons why the bending‐shearing failure of such beams happened before the pure bending failure. (2) Under certain operating loads, brittle fracture is more likely to occur on the bottom surface of such beams when directly exposed to fire. (3) The bursting and spalling depth of concrete after being exposed to fire can be used as the characteristic parameters for the rapid identification of the bottom surface of such after‐fire beams.
Highlights
With the vigorous development of highway traffic in China, more and more inflammable and explosive goods are transported by road and the number of bridge fires is increasing. e fire, which affects the bridges, causes economic losses for the country and brings potential safety hazards to the service of the bridge, affecting the normal operation of the highway
A precast 9 × 20 m prestressed concrete hollow bridge in-service on provincial expressway is designed in split width, and each width contains 16 hollow slab beams [15]. e minimum floor thickness of this bridge is 15 cm, the net protection layer thickness of steel strands is 3.6 cm, and the designed value of standard cube compressive strength of concrete is 50 MPa
The appearance inspection and classification of prestressed concrete thin slab beams removed after a fire in an operating expressway are carried out
Summary
With the vigorous development of highway traffic in China, more and more inflammable and explosive goods are transported by road and the number of bridge fires is increasing. e fire, which affects the bridges, causes economic losses for the country and brings potential safety hazards to the service of the bridge, affecting the normal operation of the highway. In China, prestressed concrete bridges account for a large proportion of the completed bridges in service [1]. Hollow slab beams are the most common form of medium- and small-span highway bridge superstructures, and about 35% of concrete girder bridges adopt hollow slab structures [2]. Its effective prestress will decrease, and the overall rigidity of the beam and slab will drop, affecting the normal service of the whole bridge. The failure of the complete bonding between steel strand and concrete will lead to structural failure along with the brittle damage of the beam and plate, which will seriously threaten the traffic safety and arouse pernicious social impact. It is necessary to examine and furtherly study the mechanical properties of those beams from fire-damaged bridges
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