Shaking Table Tests Of A Steel Structure With SMA Cable Braces

SMA cables have superior self-centering behavior,high loading capacity,and excellent energy dissipation capacity,which satisfy the application of civil engineering.The SMA cable braces which are assembled based on SMA cables have significant research implications and broad application prospects.In recent years,researchers have conducted in-depth investigations on the seismic performance of SMA cable brace.However,there is a lack of experimental research on full-scale shaking table tests based on SMA cable brace,especially on the self-centering behavior and the failure mechanism of self-centering steel frame structures supported by SMA cable brace under rare to ultra-rare earthquakes.In this paper,the theoretical analysis and full-scale shaking table tests are implemented to systematically investigate the seismic performance of the steel frame structure supported by SMA cable braces.The main research contents are as follows:(1)Based on the test objectives and conditions of shaking table tests,a four-story semi-rigid steel frame structure model supported by 8 SMA cable braces was designed in accordance with the codes.Finite element models are established by OpenSees software.To conduct a dynamic time history analysis of the designed models,five natural waves and two artificial waves(i.e.,small,medium,large and extremely rare earthquakes)were selected according to Chinese codes.The results verify the feasibility of the models.(2)Based on the steel frame specimen of the shaking table test,8 SMA cable braces were designed and fabricated.A training experiment was conducted to definite the mechanical properties of eight SMA cable braces under differences in the number of training laps,training frequency,and pre-tension force.The results show that the SMA cable brace exhibits a flag-shaped hysteretic curve during cyclic loading,performs stable mechanical properties,outstanding energy dissipation capability,and self-centering capability;The mechanical properties of the SMA cable support are significantly affected by the number of training cycles,while the effects of frequency and pretension are negligible.It is recommended to pretension the SMA cable brace at 9kN and conduct 30 cycles of 6%strain cyclic training at a low frequency of 0.01Hz.(3)A shaking table test was conducted on a steel frame equipped with SMA cable supports based on the seismic fortification intensity of 8 degrees.Three far-source and three near-source seismic waves were selected as dynamic motivation to explore the impact of different types of seismic waves on the seismic response of the steel frame structure supported by SMA cables.The research results show that the steel frame structure is undamaged under minor-earthquake,and the SMA cable support mainly provides additional stiffness for the steel frame with negligible hysteretic energy dissipation.The response of the specimen under near-source seismic motivation is greater than that under far-source seismic motivation.(4)Shaking table tests were conducted on the steel frame supported by SMA cables using Borrego Mtn waves with peak accelerations of 0.07g(small),0.20g(medium),0.40g(large),0.60g(extremely rare),and 0.80g(ultra rare)to study the seismic resistance,self-centering performance,and damage of steel frame structures under different ground motion intensities,as well as the working mechanism of SMA cable braces.The experimental results show that the steel frame equipped with SMA cable braces maintains an elastic state under different peak accelerations,without significant damage.Under the peak acceleration of 0.80g,the steel frame with SMA cable braces achieve the maximum inter-story displacement of 1/79 and performed outstanding energy dissipation ability,self-centering performance,and no residual deformation.It indicates that SMA cable braces can effectively improve the seismic performance and resilience of the steel frame.