基于FBG自感知钢绞线对预应力混凝土梁抗弯性能监测

Based on FBG self-sensing steel wire for prestressed concrete beam bending performance monitoring

为解决预应力混凝土梁的抗弯性能难以实现实时监测的问题,设计制作了两根不同线型的预应力混凝土梁,利用串联式FBG传感器内嵌于钢绞线技术,对预应力混凝土梁的抗弯性能进行实时监测。对直线及曲线孔道预应力混凝土梁进行三分点对称集中力加载试验,分析FBG传感器对梁抗弯性能的监测效果。监测结果表明:FBG传感器存活率为100%,监测数据具有稳定性,相较于电阻应变片更适合预应力混凝土梁抗弯性能的监测;同一筋材各测点处FBG传感器的应变发展趋势基本一致,荷载-应变曲线所反映的实际受力状态与理论描述受力状态一致;混凝土开裂前,FBG监测梁中应变最大误差为9.77%,远小于电阻应变片的最大误差47.63%;混凝土开裂时,FBG自感知钢绞线能跟随裂缝开展而发生突变;受拉钢筋屈服后,FBG自感知钢绞线能准确识别外荷载,且在梁中承担的力与外荷载增加量的误差小于12%。该技术实现了对梁体内预应力钢绞线及梁受力过程的实时监测。

In order to solve the problem that the flexural performance of prestressed concrete beams is difficult to achieve real-time monitoring,it designs and fabricates two prestressed concrete beams with different line types,and uses the tandem FBG sensor embedded in steel strand technology to monitor the flexural performance of prestressed concrete beams in real-time.A three-point symmetric concentrated force loading test was conducted on the prestressed concrete beams with linear and curved apertures to analyze the monitoring effect of the FBG sensors on the flexural performance of the beams.The monitoring results show that the survival rate of FBG sensor is 100%,and the monitoring data are stable,which is more suitable for monitoring the flexural performance of prestressed concrete beams than resistance strain gauges.The strain development trend of FBG sensor at each measurement point of the same tendon is basically the same,and the actual stress state reflected by the load-strain curve is consistent with the theoretical description of the stress state.The maximum error of FBG monitoring the strain in the beam before concrete cracking is 9.77%,which is much smaller than the maximum error of 47.63%for resistive strain gauges.When concrete cracks,FBG self-sensing steel strand can mutate with the crack development.Afer the tensile steel bar yielding,FBG self-sensing steel strand can accurately identify the external load,and the error between the force borne in the beam and the increase of the external load is less than 12%.This technology realizes real-time monitoring of prestressing strands and beam stressing process in the beam.