基于行车振动的桥梁加固用混凝土体积变形性能研究

Study on Volume Deformation Performance of Concrete for Bridge Reinforcement Based on Driving Vibration

为了研究行车振动作用下桥梁加固维修过程所用的混杂纤维混凝土体积变形问题,设计了一个包含4因素和3水平的正交设计振动模拟试验,模拟了不同振动频率、振动幅度、起振时间和振动时长对混凝土体积变形性能的影响。通过测试不同振动条件下的干燥收缩与温度收缩系数反映了混凝土的体积变形性能。结果表明:在振动作用下,混凝土的干缩率增加,温缩系数降低;混凝土干燥收缩影响最大的因素为起振时间,其次是振动幅度与振动时长,振动频率对干燥收缩率影响相对较小,在较低振动频率与振动幅度、较早的起振时间与较长的振动时长下,混凝土28 d的干燥收缩率较大;值得注意的是,在混凝土成型后的前28 d内,试件的收缩率增长较快,而在28 d后收缩率变化较小;温度从50℃降到-30℃的过程中,温缩系数在50~20℃范围内减小,然后在20~0℃这个范围内增加,之后在0~-10℃范围内再次减小,最后又在-10~-30℃的范围内再次增大,且混凝土温缩系数受起振时间与振动时长的影响更大,而受振动频率与振动幅度的影响相对较小。因此,在现场桥梁维修加固时应避免早时间、高频率、长时间的振动组合的发生,建议在混凝土初凝和终凝时间段内采取控制交通的手段,以减小对混凝土体积变形性能的影响。

To explore the volume deformation of hybrid fiber concrete utilized in the process of bridge reinforcement and repair under the influence of traveling vibrations,an orthogonal design vibration simulation test including 4 factors and 3 levels is designed.The influences of different vibration frequencies,vibration amplitudes,vibration initiation time and vibration durations on the volume deformation performance of concrete are simulated.The volumetric deformation performance of concrete is reflected by testing the drying shrinkage and temperature shrinkage coefficients under different vibration conditions.The result shows that(1)The dry shrinkage rate of concrete increases while the temperature shrinkage coefficient decreases under the influence of vibration.(2)The vibration initiation time is the primary factor influencing the drying shrinkage of concrete,followed by the vibration amplitude and duration,whereas the vibration frequency has a relatively minor influence on the drying shrinkage rate.The drying shrinkage rate of concrete at 28 days is greater under lower vibration frequencies and amplitudes,earlier vibration initiation time and longer vibration duration.(3)It is worth noting that the shrinkage rate of the specimen increases rapidly during the first 28 days after concrete molding,while the shrinkage rate changes slightly after 28 days.(4)During the process of temperature decrease from 50℃to-30℃,the temperature shrinkage coefficient decreases in the range of 50-20℃,then increases in the range of 20-0℃,decreases again in the range of 0--10℃,and finally increases again in the range of-10--30 C.Moreover,the temperature shrinkage coefficient of concrete is more affected by the vibration initiation time and vibration duration,while the influence of vibration frequency and vibration amplitude is relatively small.Therefore,during on-site bridge maintenance and reinforcement,early time,high frequency,and long time vibration combination should be avoided.It is recommended to take measures to control traffic during the initial and final setting periods of concrete to reduce the influence on the volume deformation performance of concrete.