Abstract
Prestressed concrete (PC) continuous girder-arch composite bridges, using concrete filled steel tubes (CFST) as the arch ribs to support the PC main girder, have gained their popularity in recently constructed large span bridges. The adoption of CFSTs brings many advantages, such as the concrete infill help to prevent the occurrence of local buckling in steel tubes, while the steel tubes can serve as framework for concrete core and strengthen the encased concrete. In order to achieve the above merits, the arch foots connecting the CFST arch ribs and PC girder are supposed to have sufficient strength and stiffness. However, the extensive use of CFST arch ribs showed that concrete cracking are commonly found at the arch foots. This paper studied the structural behavior of arch foot by employing a comprehensive numerical model. The influence of pumping pressure from concrete infill at construction stage on local stress of the arch foots was presented and discussed. The results indicated that the radial stress produced by pumping pressure at the joint zone squeezed the concrete around the arch foots, which resulted in significant hoop tensile stresses in the surrounding concrete. The outcomes of this study can provide technical support to improve the construction quality and structure stability, and optimize the construction procedures for this type of bridges.
Highlights
Prestressed concrete (PC) continuous girder-arch composite bridge, consisting of PC box-girder and concrete filled steel tube (CFST) arch ribs, are very popular in the construction of railway bridges
The cracking of CFST arch foot is a key problem to the structural safety of CFST arch bridge, and the influence of pumping pressure of concrete infill on the cracking of arch concrete is significant
This paper examined the structural behavior of arch foot during construction stage, the conclusions can be drawn: 1) In the first stage of pumping concrete, under the radial stress induced by the pumping pressure, the maximum tensile and compressive stress in steel tubes are 123.0 MPa and –95.0 MPa, respectively, which are under the material allowable stress
Summary
Prestressed concrete (PC) continuous girder-arch composite bridge, consisting of PC box-girder and concrete filled steel tube (CFST) arch ribs, are very popular in the construction of railway bridges. The arch foot connecting CFST arch ribs and PC girder is critical for load transition between the members. The arch foot should transfer axial, bending and shear forces from arch ribs to the supports, and carry loads from the lateral direction of the PC girder [2]. Concrete cracking at the arch foot harms the bearing capacity and durability of the girder-arch composite bridge. In order to prevent the occurrence of concrete cracking at the arch foots in service period, many suggestions for optimizing the design of the arch bridge have been reported during the past decades [3]. With the widely construction of girder-arch composite bridges using CFST arch ribs, it is found that cracking are commonly found on the surfaces of concrete at the arch foot joint zone [4]. Related studies revealed that despite the favorable capacity of the joint concrete in service period, the tensile stress
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