Development Of High-dissipative Viscoelastic Material And Analysis On Its Damping Structure

As a typical passive energy dissipation device,viscoelastic damper has the advantages of reliable performance,simple structure,convenient manufacture and low cost.It is widely used in structural damping control.At present,domestic and foreign scholars have carried out a large number of experimental and theoretical research on the viscoelastic damping technology of building structures and made many achievements,but there are still some problems that need to be further studied,especially the high dissipation viscoelastic dampers for low-frequency vibration such as earthquake and wind vibration are relatively few.Therefore,based on the micro energy dissipation mechanism of viscoelastic materials,this paper studies the development and performance test of viscoelastic materials,the dynamic mechanical performance test of viscoelastic dampers,the micro mechanical model of viscoelastic dampers,the dynamic analysis and optimization of viscoelastic damping structures,and the main research work is as follows:(1)From the three aspects of matrix rubber molecular chain energy consumption,filler network energy consumption and the interaction between filler and matrix rubber,the effects of rubber molecular chain length and tube constraint,molecular chain formation and chain breaking,and the strong and weak interface interaction between filler and matrix on the energy consumption capacity of viscoelastic materials are analyzed.Through the in-depth study of the energy dissipation mechanism of viscoelastic materials,it provides a theoretical basis and guiding ideology for the formulation and preparation of viscoelastic materials with low frequency and high dissipation,and lays a theoretical foundation for the micro molecular chain model of viscoelastic dampers.(2)Based on the research on the micro energy dissipation mechanism of viscoelastic materials,NBR and ACM were selected as rubber matrix.By changing the types and components of damping modifier,reinforcing filler and vulcanization system,more than 40 viscoelastic materials with different formulations were developed and the corresponding performance tests were carried out.The mechanical properties such as damping,tensile strength and elongation at break of different viscoelastic materials were compared and analyzed,The effects of ambient temperature,excitation frequency and loading amplitude on the dynamic mechanical properties of viscoelastic materials are studied;The optimized loss factor of viscoelastic material is up to 3.52 in the actual service temperature and main seismic frequency band.(3)The dynamic mechanical properties of the developed viscoelastic damper were tested under different ambient temperatures,different loading amplitudes and different excitation frequencies;The effects of ambient temperature,loading amplitude and excitation frequency on the dynamic mechanical properties of viscoelastic dampers under shear mode are analyzed.The test results show that the viscoelastic damper has strong energy dissipation capacity in low frequency,and its mechanical properties are greatly affected by temperature and frequency,but less affected by displacement amplitude.(4)Based on the assumption of micro spherical molecular configuration of viscoelastic materials,an equivalent fractional micro spherical molecular chain model of viscoelastic damper is proposed.In the model,the hyperelastic and viscoelastic properties of viscoelastic materials are characterized by network molecular chain and free molecular chain respectively,and the fractional derivative element and temperature frequency equivalence principle are introduced to consider the effects of frequency and temperature on the dynamic mechanical properties of the damper.The comparison between the proposed model and the experimental results shows that the numerical results of the model are in good agreement with the experimental results.The proposed model can accurately describe the effects of excitation frequency,ambient temperature and microstructure on the performance of the damper.(5)The damping project of a primary school in Yunnan is selected,and the dynamic analysis of viscoelastic damping structure is carried out by using OPENSEES to verify the control effect of the developed high dissipation viscoelastic damper.By comparing and analyzing the displacement,acceleration and inter story displacement angle of the structure under uncontrolled and controlled conditions,it is shown that the viscoelastic damper can significantly reduce the seismic catastrophe effect of the structure.Through MATLAB OPENSEES joint programming,the viscoelastic damping design scheme is optimized by genetic algorithm.The optimization objective considers the inter story displacement angle,acceleration index and torsional effect of the structure at the same time.Because the optimization scheme considers the structural dynamic characteristics,building use function and the universality of seismic excitation,it provides a design reference for the optimization analysis of other damping structures.The innovations of this paper are of the followings:(1)Considering the chain formation and breaking of filler network and the strong and weak interface effect of colloid filler,the formula of viscoelastic material with high dissipation capacity in the main frequency bands of actual use temperature and seismic excitation is optimized,and the damping performance of viscoelastic material is greatly improved.(2)Based on the micro spherical molecular configuration assumption of viscoelastic materials,the network molecular chain and free molecular chain are introduced,and with the help of the fractional mechanical model,the equivalent fractional micro spherical molecular chain model which can accurately describe the dynamic mechanical properties of viscoelastic dampers is proposed by considering the influence of temperature on the dynamic mechanical properties of dampers through the principle of temperature frequency equivalence.(3)Through the joint programming of Matlab-Opensees,the viscoelastic damping design scheme is optimized by genetic algorithm.The optimization objective takes into account the inter story displacement angle,acceleration index and torsional effect of the structure.Aiming at the actual three-dimensional engineering structure,a fast optimization method of viscoelastic damping considering the dynamic characteristics of the structure,the use function of the building and the universality of seismic excitation is proposed.