Study On Mechanical Properties Of Steel-bar-type Energy Dissipator Used In Flexible Protection Structures

At present,energy dissipators for passive flexible protection systems have problems such as unstable working tension,poor energy consumption,low utilization rate,and inconvenient maintenance and replacement.It is urgent to find a stable working force,high energy consumption,and multiple times.Reuse a simple energy consuming device.Therefore,this paper proposes a reusable rod type energy dissipator.In order to study its mechanical properties,the quasi-static repeated tensile test,the weight drop free fall impact test,the passive flexible protection system full scale impact test and numerical simulation method were carried out.specific work and results are as follows:1)Nine groups of test specimens were designed to conduct the reversed quasi-static tensile test.According to the force-displacement curve obtained from the experiment,a simplified mechanical model of the energy damper is proposed,and the theoretical value of the quasi-static starting force of the rod damper is given.2)The heavy object free-fall impact test of 6 sets of bar type energy dampers was carried out.The effects of the diameter of the roller,the diameter of the steel bar and the number of steel bars on the starting force of the damper under dynamic impact are studied.3)The full-scale impact test of two 2000 kJ passive protective nets was carried out,and the working performance of the rod-type energy dampers in the actual flexible protective structure was studied.4)The numerical simulation analysis of the mechanical behavior of the energy consuming device was carried out.The effects of roller diameter,steel yield strength,impact velocity and weight quality on the mechanical properties of the rod damper were studied.5)The numerical simulation of the full-scale test of 2000 kJ was carried out.The speed of the supporting rope corresponding to the starting time of the rod-type dampers of two different mechanical models was studied,and the numerical simulation results were compared with the experimental results.Through the above work,this paper mainly got the following conclusions:1)The experimental results indicated that: both the activated load and energy dissipating capacity increase with the number and diameter of steel bars.Among them,the activated load and energy consumption of the 1?16mm test piece are the smallest,but the 3?20mm test piece are the largest,and the increase of the repeated stretching number i reduces the mechanical performance of the steel-bar-type energy dissipator;At the same time,the load-displacement curves obtained by the test show that the steel-bar-type energy dissipator has two typical working stages when working,so it is proposed to simplify its force-displacement curve into a double-fold line model,and build a rod-type energy damper accordingly.The theoretical formula of quasi-static activated load and energy dissipating capacity,which takes into account the influence of the diameter and number of steel bars and the number of repeated stretching,and the simulated values agree well with the experimental data;2)The results of the dynamic impact test of the rod type energy damper show that the starting force of the energy damper differs from the first trough value of the working tension by more than 60%,and has obvious pulse effect;the starting force is positively correlated with the diameter and number of steel rods;In addition,the diameter of the steel rod is reduced by 6% when it is single-stretched;3)Through the full-scale test,it is found that the activated load value of the rod energy dissipation device was greater than the average working tension,showing a slight pulse effect,and the elongation of the energy dissipation connected on the support main rope was close to the predetermined maximum stroke,while the tensile elongation of two energy-consuming converters on the upper pull anchor rope was the largest,On both sides of the pull anchor rope position energy dissipation device did not start;4)the research shows that: The activated load increases with the diameter of the roller and then decreases,and the maximum activated load is reached when the diameter of the roller is 40 mm.The greater the activated load,the greater the activated load of the steel strength and impact speed,and the heavy weight quality has little effect on the mechanical properties of the energy dissipation device.In addition,the greater the impact speed,the greater the pulse effect of the energy dissipation device.Based on the analysis of the numerical results of the activated load and the average working tension of the heavy weight free drop impact test at different impact speeds,it is found that the activated load of the quasi-static tensile test can be obtained by the product of the amplification coefficient and the reduction coefficient at different speeds,and the activated load and the average working tension of the three-fold line mechanical model of the the energy dissipation device under certain speed;5)In the engineering design,through the comparison and analysis with MEL test of the second 2000 kJ,it is found that the calculation results of the mechanical model of three-fold line of the energy dissipation device are more in agreement with the experimental values,and the design method of flexible protection system engineering using the rod energy dissipation device is put forward.