Research On Optimizing Design And Performance Of High Strength Lightweight Aggregate Concrete Member

Low density, good resistance to vibration and high durability are the characteristics of structural lightweight aggregate concretes (SLC) which are especially suitable for the construction of long-span structural projects such as high buildings, bridges and key projects with complicated geography or a special command for durability. The priorities of SLC are significant to different project construction and will show wide prosperity. Based on the research of prepared technology and properties of materials, the properties of reinforced and pre-stressed high strength lightweight aggregate concrete was studied deeply and systematically with the method of experiment,finite element simulating and project application. Relativity of material and concrete member was revealed. The design method of optimizing for lightweight aggregate concrete member was proposed. Research results provide references for the amending of Design Criterion of Structural Lightweight Aggregate Concrete and the edition of Design Criterion for Lightweight Aggregate Concrete Bridge, and is of significant importance for the application of these materials in bridgestructure.The main research work and compliments of this paper are as follows:Main factors influencing the mechanic properties of high strength lightweight aggregate concrete (HSLC) was found out. Key technical parameters for preparing HSLC with the strength range of LC40～LC60 were confirmed. Lightweight aggregate concretes of LC40～LC60 with high workability were prepared with raw materials of high strength lightweight aggregate of class 800 and 42.5# Portland cement. Formula of constitutive relations model of HSLC was revised, which established theoretic foundation for structural design and finite element analysis.Properties of reinforced lightweight aggregate concrete (RLC) bending members with strength in the range LC40～LC60 were systematically studied for the first time. Bearing capacity of normal cross section, ductility, cracking load and failure characteristics of RLC were studied. The study result suggest that it is applicable of structural design criterion formula of common concrete for HSLC and then calculate formula for crack bending moment of rectangle cross section was revised.With supported project and one piece pre-stressed HSLC girder of 20m long, relations among load,deflection and distortion of pre-stressed members were studied; As a result, a effective and applicable finite element analysis model of pre-stressed lightweight aggregate concrete (PLC) was established using computer technology and ANSYS finite element soft. With using of the model, mechanic behavior of members under the action of pre-stress and load were researched, and the stress distribution characteristics of anchorage zone of concrete end was studied. The cracking causation of anchorage zone of concrete end was found out. Then, structural grads designing method for effectively resolving the cracking of anchorage zone of PLC end was invested. As a result, optimized parameters for member end structure and material were confirmed.Long-term creep effect of PLC member was studied for the first time. Creep characteristics of lightweight aggregate concrete with strength class 40 was founded out, then creep coefficient formula of LC under tendon pre-stress 14d age was regressed and calculating formula for the value of ruling coefficient C₁ in the finite element analysis was deducted, which established bases for the finite element analysis of long-term creep effect of members; Laws of pre-stress loss and deflection changing of members under the state of load and unload was studied and compared LC...