Study On The Temperature Effect Of Super-long Concrete Cross-layers Isolation Structure And Its Influence Mechanism

With the rapid development of China’s economy,there is an increasing demand for the application of seismic isolation technology for super-long concrete structures such as large public buildings and industrial plants.With this,the initial displacement of the seismic isolation layer bearing due to temperature and shrinkage of super-long concrete structures has become a common concern in engineering circles.The large temperature difference and low-temperature environmental conditions located in the western region make the bearing deformation of super-long concrete isolation structures more prominent.Some super-long concrete seismic isolation structures have a large number of electrical pipelines to be transmitted to the upper floors because the local basement is a down-hung elevator and equipment machine room,and if the seismic isolation layer is set below the bottom of the first floor,it will cause a large number of electrical pipelines to pass through the isolation layer,and if the isolation layer is set at the bottom of the first floor,the function of the structure cannot be realized,so the seismic isolation bearings are chosen to be set across the floors,forming a super-long concrete crosslayers isolation structure,which The structure has several seismic isolation layers with different elevations.Since the greatest temperature effect of the super-long concrete frame structure is in the bottom layer,which is more restrained,and the temperature effect decreases rapidly from the bottom layer to the top layer of the structure,only the internal forces and stresses in the bottom layer of the structure are analyzed.However,for the super-long concrete cross-layers isolation structure,due to the existence of the flexible isolation layer,the restraint of the bottom floor is released and there are several isolation layers with different elevations,so it is necessary to analyze not only the effect of the bottom floor temperature on the displacement of the seismic isolation bearing,but also the effect of the temperature of each other layer.Therefore,in this paper,we take the super-long concrete cross-layers isolation structure as the research object,and analyze the concrete members and the structure as a whole under the effect of temperature,respectively.The main research contents of this paper and the main conclusions drawn are as follows:(1)From the experiments,the strain of the reinforcement inside the concrete frame beam under the action of sunlight was collected based on the electrical measurement method,as well as the measurement of the internal temperature,surface temperature,and ambient temperature of the frame beam using thermometers to reveal the variation law of strain with temperature and the mechanism of displacement of the seismic isolation bearing due to the action of temperature.The results show that the strain of the reinforcement inside the concrete varies with the temperature inside the frame beam and varies periodically in terms of days,and the greater the temperature difference,the greater the strain;solar radiation has a large effect on the concrete temperature,and the maximum temperature difference between the surface of the concrete members exposed to the sun and those not exposed to the sun is more than 10°C.(2)The SAP2000 finite element software was used to establish the model of the super-long concrete cross-layer isolation structure with different number of spans at the bottom,and the model of the span isolation structure with the isolation bearing spanning one floor and the number of spans at the bottom being half of the overall span was selected to analyze the structural deformation,temperature stress and internal force under the unit negative temperature difference condition.Then,the effects of the number of bottom spans,the number of spans,the stiffness of the seismic isolation layer and the temperature of each layer on the maximum horizontal displacement of the seismic isolation bearing under the temperature action of the super-long concrete crosslayers isolation structure were analyzed.The results show that the deformation increases gradually from the center to the edge of the structure with the center of the building cover as the deformation immobile point,and the maximum deformation of the building cover increases from the F1 to F5 floors in order;the temperature action mainly affects the axial force of the frame beam,the shear force of the frame column and the bending moment of the frame column and frame beam,and the structural internal force appears abruptly at the span of the seismic isolation bearing;the temperature stress of the building cover of the F1,F3,F4 and F5 floors decreases gradually from the middle to the edge of the structure,while the maximum horizontal displacement of the F2 floor increases suddenly at the span of the seismic isolation bearing.The maximum horizontal displacement of seismic isolation bearing increases gradually with the increase of the number of spans at the bottom of the structure and the decrease of the stiffness of the seismic isolation layer,and the change of the number of spans at the bottom has more influence on the maximum horizontal displacement of seismic isolation bearing when the number of spans at the bottom increases,the stiffness of the seismic isolation layer increases,and the number of spans of the bearing increases.(3)Based on the measured temperature of each layer and the displacement of seismic isolation bearing in a western international airport renovation and expansion terminal building project with the span setting of seismic isolation bearing,the correctness of the proposed model is verified and the deformation law of seismic isolation bearing is analyzed;then,the influence law of the temperature of each layer on the displacement of seismic isolation bearing under the action of vertical temperature gradient and unit temperature is analyzed by the model,and finally,summarized the temperature effect control measures used in the project.The results show that the simulation results of the seismic isolation bearing displacement under the action of the measured vertical temperature gradient basically match with the measured data;the maximum displacement bearing of the seismic isolation structure is usually not the maximum shear deformation bearing after the bearing is set across the floors,and it should be reasonably designed and arranged according to the seismic isolation structure bearing control objectives;when the bearing is in the bottom seismic isolation layer,the bearing displacement influence coefficient tends to decrease exponentially with the increase of floors,and the bearing displacement is mainly influenced by the bottom two floors.The bearing displacement is mainly influenced by the temperature of the bottom two layers;when the bearing is in the upper part of a seismic isolation layer,the temperature of the layer has the greatest influence on the displacement of the bearing,and the bearing displacement is mainly influenced by the temperature of the layer and the two adjacent layers.