Laboratory Research On CRCP Approach Pavements Of Jointless Bridges

The jointless technique has been being used more frequently in some small and medium bridges, in recent years. Based on the sub project of the western traffic construction technology project named the Applied Research of Jointless Technique in Small or Medium Bridges, the paper proposes an innovative structural design for jointless bridges, which eliminates the expansion joint between the bridge slab and bridge by absorbing the deformation of temperature dropping through approach pavements of CRCP. The main bridge, approach slab and approach pavement will be integrated into a whole in this design, which not only realizes "jointless" design concept, but also simplifies the treatment of the approach slab.The stress state of CRCP approach pavements are very complicated, not only effected by vehicle load and temperature load, but also the shrinkage deformation of jointless bridges influenced by temperature. In this paper, the mechanism of inducting Bridges'deformation is analyzed, and the design theory of CRCP approach pavements is preliminary discussed.To ensure approach pavements working normally in complex force conditions, we proposed to set an isolated layer between the base and surface through the experiment. The friction coefficient of isolated layer should be controlled between 2-5, and should be capable to deform widely. The connection between base and surface should be in a half-combining state, which means neither too strong nor too weak.The space of transverse crack is discrete and develops desultorily in traditional CRCP. This paper proposes a method of active crack controlling to induce crack, which can change the development of crack from disorder to order to achieve the purpose of controlling the crack's development. Through a lot of experimental test, we make a preliminary analysis for several important indexes. The major achievements are summarized as following:(1) Cracks are all developed in the active crack section during experiment, which proved that the controlling capability of the active crack is outstanding during the temperature dropping.(2) After the active crack controlling in approach pavements, the cracks developmental regularities changes a lot. The development of crack width is associated with position of the predefined weak side. The crack width develops rapidly near the slab, and develops slowly far from the slab. There are no cracks in the end of the approach pavements.(3) The development of reinforced stress is similar in all of the sections.It has corresponding relationship with the development of the crack width, also the wider the crack section is the faster the reinforced stress develops. Besides, the reinforced stress has a tendency of decrease from near slab to far slab.(4) Experimental data analysis indicates that the approach pavements of CRCP have good load-transfered capacity. After the comparison of the load-transfered capacities in the same section with different crack width, it is found that the wider the crack is the poorer load-transferred capacity will be.