| CRTSⅢ slab track system is a part of China railway high-speed and is China’s independent research and development, with complete independent intellectual property. In the track structure, precast track slab and cast-in-place self compacting concrete(SCC) form a composite structure closely through interlayer bonding and U-type rebar. For slab track is the foundation of high-speed train operation, interlayer bonding is bound to destruction under long-term’s combined action of the weak interlayer bonding between the old and new concrete internal and post-operation environment external, which may cause seam between track slab and SCC eventually. For interlayer connection is the basic guarantee for the normal work of the track structure, different state of interlayer connection of CRTSⅢ slab track were taken into consideration in this paper. And the corresponding fine beam-body finite element model is established based on the platform of finite element software ABAQUS, including the constitutive model of concrete (CDP, concrete damage plastic). The main research contents and conclusions are as follows.(1) When the interlayer connection only contains U-type rebar connection, namely, without interlayer bonding, U-type rebar connection cannot make the track slab and SCC reach full synergism under different load conditions, compared with well bonded. Taking the action of train load case and common load case (including commonly used positive temperature load and common train load) for example, when load cases above are applied to the track structure respectively, synergy degree are 57% and 69%, the synergy degree is low.(2) U-type rebar makes the track slab and SCC partial synergy under the action of the external load, and the SCC around the U-type rebar is in the state of high stress. The function of SCC cam plate are horizontal displacement limitation and horizontal load transfer. The results show that, the place where U-type rebar are anchored, and both ends of cam plate longitudinally along the SCC are the weak parts, which are prone to damage under the action of external load.(3) Due to the large shrinkage rate of SCC, no matter the interlayer bonding is well bonded or not, SCC are severely damaged under the load case of shrinkage (equivalent simulation by lower the temperature). Although the results of calculation are quite different from the actual state of track structure, it also prove that early maintenance is very important since the completion of the SCC pouring.(4) Increase of U-type rebar diameter are conducive to the synergy degree improvement, but the space is limited. When U-type rebar diameter increases 1 times (increasing from 12 mm to 25 mm), the improvement of synergy degree are about 10%,6% and 8% respectively under the action of train load, the maximum temperature gradient and common load case. In addition, according to the changing trends of synergy degree, it can be predicted that increasing the diameter of U-type rebar cannot make the track slab and SCC reach full synergism.(5) When the interlayer connection only contains U-type rebar connection, the SCC around the U-type rebar is in the state of high stress. The synergy degree improves along with the growth of the U-type rebar diameter. However the SCC damage area gradually expanded at the same time. Damage area mainly appears at the end of the SCC, around the 2nd～5th rows of U-type rebar. The calculation results show that the damage occurs no matter how the diameter changes, which is not conducive to the anchorage of U-type rebar. Therefore, it is recommended that U-type rebar at the end of SCC should be improved and optimized, in order to guarantee the slab track work properly in the service life, especially without interlayer bonding. |
PDF Full Text Request