Seismic Analysis Of Viscoelastic Structure With Special-Shaped Cloumns In Mountainous Region

In China, Mountainous region account for more than two-thirds of the totalgeographical area. It’s especially important to study the seismic performance of themountainous structures on complex terrain. Former sdudies on Soil-StructureInteraction (SSI) have proved that site will change the dynamic property of structure.On the other hand, the control efficiency of damping device is closely related to thedynamic property of structure. Therefore, seismic analysis on viscoelastic structures inmountainous region has important practical significance. Only mastering the influencerules and considering it in the practice can get a better damping effect.In this paper, viscoelastic frame structure with special-shaped columns on twokinds of gound was analyzed with the ANSYS. These two kinds of ground included ofground with terrace scarp and ground with inclined base-rock. To the structure on theground with terrace scarp, seismic responses and damping effect of structure with SSIand without SSI were comparative analyzed, and the effect of soil stiffness, scarp height,and spans under the scarp to seismic responses of structure were discussed. To thestructure on the ground with inclined base-rock, the slope of base-rock effect onstructure was studied.Based on the analysis of structures with SSI and without SSI on terrace scarpground, these achievements are concluded:①The natural vibration frequencies of SSImodel is lower than N-SSI model, and controlled structure is greater than uncontrolledstructure.②SSI model is more sensitive to seismic wave. The seismic responses of SSImodel are greater than N-SSI model, so SSI model may not security enough. The scarpwould amplify seismic responses.③When analyze with N-SSI model, the shear forceof columns under the scarp is abnormal, so that the actual internal force of columns maybe ignored.④The control efficiency on structure with SSI model is closely related tothe inputting seismic wave and the site characteristic. The viscoelastic damp wouldcomsume energy more fully when considering SSI.After discussing the effect of soil stiffness, scarp height, and number of spansunder the scarp on structure, conclusions are as follows:①The natural vibrationfrequency of structure decreases with the soil stiffness decrease, increases with the scarpheight increase, and decreases with the spans under the scarp increase. But when thescarp height increases to a certain extent, the higher order frequency will be reduced. ②The soil stiffness effect on structure is related to the inputting. When the inputtingwave contains less high frequency, the seismic responses may increase with the soilstiffness decrease. When the inputting wave cantains more high frequency, the seismicresponses may be reduced on softer soil ground.③The effect of scarp height andnumber of spans under the scarp on uncontrolled structure is related to the inputting,while on controlled structure it has less relational to the inputting. And the responses offloors under the scarp have greater impact than floors above when the scarp height andnumber of spans under the scarp change.④The ground and inputting wave will bothaffect the control efficiency of viscoelastic structure on scarp. The ground condition andearthquake group of the site must be both taken account seriously when designing thedamping device.By studying the seismic responses and damping effect of structure on the groundwith inclined base-rock, three conclusions have obtained:①The natural vibrationfrequency of structure increases with the base-rock slop increases.②Inclined base-rockwill restrain the inputting amplification by soil. And the restraining will be moreobvious if the base-rock slop is greater. Therefore, all the responses of structure oninclined base-rock are lower than on flat ground.③Ground with different base-rockslop will lead to different control efficiency, it can be better or worse. Even though tothe same structure excited by the same seismic wave, as the base-rock slop is different,the control efficiency may be in great difference. So, only taking SSI into account anddesigning damping device with the realistic ground can obtain a better controlefficiency.