| With rapid development of the transportation industry,freeway construction is increasingly extensive,the bridge plays an important role in freeways.In small span bridges which are small design discharge,grade seperation bridges and passages,pier and abutment of the thin wall type is more superior:The thin wall abutment suffers force reasonably of which the engineering quantity is less and can satisfy various requirements of bearing capacity of ground,cubic meter of earth of digging foundation less,the striding ability of the bridge is stronger,not being limited by side slope of subgrade,economizing the span,and making full use of the clearance under span;And the type of the bridge is agile and beautiful,easy to constructed .In this text,calculating the thin wall abutment mainly,the concrete example is a thin wall abutment enlarged foundation. The main characteristics of bearing force of the thin wall abutment enlarged foundation:In order to prevent the abutment moving towards the middle of the span,making use of the bearing beam of the superstructure and the supporting structure as the support of the abutment.The whole structure (the thin wall abutment of enlarged foundation) is the system of rigid frame construction of four hinges.According to the simple-supported beam of top and bottom hinged support,the abutment body bears the level and the perpendicular force. The thin wall abutment of enlarged foundation is proceeded the concrete calculation following the below a few aspects:With the side earth pressure,the girder of abutment is calculated sectional strength as perpendicular beam. When calculating the abutment as the perpendicular beam,first,the most disadvantageous way of arranging the load that is often used is: arranging the load on the embankment filling breaking pyramid of the back of the abutment,vehicular load and backfilling produce the earth pressure to the abutment body,with the earth pressure the abutment produces the bending moment,shear,and the bearing reaction produced by the self-gravitation of the abutment and the superstructure above the bridge checking section; under the most disadvantageous loading combinations,checking the section strength,including the strength calculation of eccentric compression and strength checking of bended section;secondly,checking the stability,the vertical stability of the curved plane with eccentric compression,the vertical stability of the in-curved plane with central compression;a second time, conducting the check of the disposition reinforcing bar,considering the abutment as the component bended,and the abutment bearing permanent load and live load of upper abutment body and the bending moment produced by the earth pressure of abutment back,under the most disadvantageous loading combinations,checking the section strength of the bottom of the abutment body. With the perpendicular load,the cross direction of abutment is checked to calculate as a short beam of elastic subsoil. L is the length of the thin wall abutment.when L is larger than 1.2/α and smaller than 4/α,the abutment is checked to calculate as a short beam of elastic subsoil.First,checking the short beam condition of subsoil,calculating the bending moment produced by all kinds of loads;secondly,combining the internal force;a second time,checking the cross section strength of abutment body.Checking the maxium pressure stress of the foundation bottom. The stress of the foundation bottom of the abutment is the sum of the stress that caused by the gravitation of the abutment and the bridge construction,vehicular load.The sum calculated can not exceed the allowable bearing pressure of the subsoil. In the actual subsoil the foundation is composed of many layers soil,if below the bearing stratum the bearing force of the subsoil is lower than the bearing force of the bearing stratum,the bearing force of the weak stratum must be checked;when the weak underlying stratum is composed of higher compressed and thicker soft gluing soil,or when the superstruction has some dema...
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