Experimental Study On Shear Behavior Of Assembled Steel Underpinning Joints With Log Columns Under Eccentric Compression

With the development of the times,the scale of new buildings has decreased significantly,and the translation and reconstruction of old buildings have become more and more.In a large number of ancient buildings,part of them will face the risk of demolition because of the requirements of urban development planning.For buildings with intact structure and function,or buildings with important memorial significance and historical heritage,demolition will obviously bring immeasurable losses to the economy,civilization and culture of the country and society,On the other hand,if these old buildings are promoted or protected by integral displacement,on the one hand,it can save a lot of construction funds,shorten the construction period,reduce environmental pollution and the impact on the surrounding environment,and achieve ideal economic and social benefits.Building displacement technology started in Europe and the United States(New Zealand)at the beginning of the 20 th century.Since then,many countries in the world have begun to study this technology.The so-called displacement technology is to change the position of the building in space through certain engineering and technical means on the premise of maintaining the overall safety of the building.Generally,climbing,turning,lifting,translation and rotation,or combined displacement of these kinds are seen.In this paper,the experimental research and Analysis on the non-destructive safety underpinning of round timber columns in wood structure buildings,especially in the transformation or displacement of ancient buildings,are carried out by using the assembled steel underpinning device when considering the eccentric load.The wood column in the wood structure building may have some eccentric load due to the upper load or processing and installation,or due to the installation deviation of the underpinning structure or temporary support components.Therefore,under the premise of axial compression test,this paper takes eccentric compression as the research direction,and adopts the assembled steel underpinning device to carry out the experimental research on two groups of round timber columns with and without painting,so as to simulate the actual underpinning situation of painted and unpainted wood columns.Three kinds of preload and three kinds of eccentricity were applied to each group.The test results show that with the increase of load eccentricity,the friction coefficient decreases and the bearing capacity of underpinning joint decreases;The test results of two groups of wood columns show that the friction coefficient of the joint surface of the wood column with painted surface is smaller than that of the wood column without painted surface,so it can be judged that the painted surface will affect the force of the underpinning joint.Through the analysis and calculation,the static friction coefficient between the underpinning steel beam and round wooden column and the influence of painting on the friction coefficient are obtained,and the reference value of the friction coefficient when the round wooden column is eccentrically loaded is put forward,which provides the calculation basis for the underpinning design of round wooden column.The test results show that the paint can reduce the friction coefficient of the components.In a certain range,even in the case of eccentricity,the round timber column assembled steel underpinning device has good stability and shear capacity,which provides a useful basis for the popularization and application of round timber column non-destructive steel underpinning technology.