The Stress Analysis And Design Of Lightweight Aggregate Concrete Filled Steel Tube Enclosing Purlin In Deep Foundation PIT

With the rapid development of rail transportation in major cities, thedevelopment and utilization of underground space is expanding. In the subway pit ordeep foundation pit support, the steel enclosing purlin is not a coherent whole, on thecontrary, it is a separately and loosely system, which is not favorable to the structure.On the other hand, the steel purlin used presently is joint by two parallel beam, andthe riser of the enclosing steel purlin is vacant, this may decrease the carrying capacityof the enclosing purlin. Furthermore, the inner and outer of the enclosing purlin is fullof weld joint, which may easily rust, and these shortcomings made it hard to storagethe enclosing purlin for the long term, also made it difficult to reuse.This article designes a lightweight aggregate concrete filled steel tube enclosingpurlin in deep foundation pit for the first time,It has applied the national patent. patentnos:201110456550.0and201120569643.X.Analyzes and researches the stress againstfor the inadequate of the existing deep foundation pit enclosing purlin,Including thefollowing aspects:combining with the characteristics of the lightweight aggregateconcrete filled steel, designes structure program of the deep foundation pit lightweightaggregate concrete filled steel enclosing purlin;regarded enclosing purlin as thehorizontal elastic foundation beam,establishes a force calculation model of theenclosing purlin, calculates and analyzes the specific force of the deep foundation pitlightweight aggregate concrete filled steel enclosing purlin;analyzes the trend of theflexural capacity of concrete filled steel under the impact factors of the different steelratio,concrete strength and steel strength,obtaines peculiarities in designing andcalculating the flexural capacity of rectangular concrete filled steel tube using thedifferent design disciplines,selectes the appropriate procedures to lightweightaggregate concrete filled steel tube enclosing purlin;combining with specific projectexamples, designes the enclosing purlin conformed the engineering requirements,anddesignes the welds and bolts at its junction.This article obtaines the following achievements through analysis and research:(1)one kind lightweight aggregate concrete filled steel tube enclosing purlin is designedof high local carrying capacity,good integrity and high recycling rate;(2)the flexuralcapacity of concrete filled steel tube can maximize when calculate using structuretechnical specification of concrete filled steel DBJ13-51-2003;(3) the lightweightaggregate concrete filled steel enclosing purlin is calculated in specific project examples using the elastic foundation beam method,the accurate sectional dimensionof lightweight aggregate concrete filled steel tube enclosing purlin was designed;(4)the bolts and welds in the specific project examples were calculated,the designprograms were obtained which have certain reference value.