Akane UENO
Evaluation of cracking resistance on a three-layered buried joint by direct tensile tests
Osamu TAKAHASHI
A buried joint is constructed at an edge portion of bridge deck as a part of bridge pavements in order to disperse and absorb stress and strain caused by thermal displacement of the bridge edge. The dispersion type of buried joint has a grid panel in binder course as reinforcement and sliding sheets under the binder course.Major failure form of the buried joint is transverse cracking at the edge part. It is caused from contraction of the main girder toward bridge axial direction due to temperature changes.This study discusses the buried joint comprised of three layers of surface course, binder course and composite course containing the grid panel.The composite course doesn¡Çt split out cause of the grid panel even though forced severe tension.Therefore cracking resistance of the buried joint deeply depends on the contraction efficiencies of surface course and binder course.
This study evaluated cracking resistance efficiency of the three-layered buried joint based on two kinds of direct tensile test. One direct tensile test was conducted using two-layered specimens, namely surface course with binder course. The other direct tensile test was carried out separately using surface course and binder course. The results were compared with each other and cracking resistance efficiency was estimated.Furthermore, a stepwise tensile test was carried out to take a relaxation effect into account. The results of strain at failure were compared with those from the direct tensile test.Then the maximum strain caused from contraction of a girder in the buried joint was estimated using data of temperature change in Kanto Area. Cracking resistance was evaluated from the comparison of the maximum strain with the strain at failure of the buried joint.
The study confirmed the following findings. Strain at failure on the two¡¾layered asphalt concrete is lower than that on the surface course, but is higher than that on the binder course.The strain at failure on the two¡¾layered asphalt concrete is influenced mainly from that on the binder course.Relaxation in the asphalt concrete decreases the stress considerably and increases the strain at failure on the stepwise tensile test. It was estimate that the tensile strain at failure on the three layered buried joint is approximately 20,000?10-6.Stiffness of three-layered buried joint was estimated approximately 300 kgf/cm2. The maximum strain caused from contraction of a girder in the three-layered buried joint for one day was also estimated about 9,040?10-6.Therefore, the study concluded that cracking resistance of the three-layered buried joint was sufficient and applicability of that was also enough in Kanto Area.
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