Analyze Method Of RC Structures Under The Consideration Of Time Factor

Long span, high durability and strict serviceability requirements are all significant characteristics of modern RC structures. Accurate and comprehensive analyses should be done when designing a structure to guarantee its safety in its whole service life. Whatever the supplies on RC structures or RC structures themselves are all changing with the time goes by. Time factor must be taken into consideration for reasonable and accurate analyze and design of structures. This paper studies systemically the analyze and design methods of RC structures under the consideration of time factor. The contents and results of this paper can be concluded as:1) Time-dependent characteristics of materials are analyzed. Deformation characteristics and their calculation equations are especially introduced. Universally applicable material constitutive equation is set up using principle of variation.2) The evolvement of Calculation theory of Creep and shrinkage are Systemically presented, a new time-dependent-calculation-modulus method is introduced using the mean value theorem of integral and step-by-step calculation method is improved. At last creep FEM step-by -step method for simple structures and creep FEM step-by-step concealment method for complex structures are presented.3) Section σ—εanalyze method for RC structures is introduced under the consideration of time factor. Self stress causing by shrinkage, creep, temperature or relaxation can be calculated using this method. The new concept of section-time-dependent-calculation rigidity is introduced, a new method for calculating deformation of statically determinate structures is introduced and corresponding program is developed.4) Using the concept of time-dependent-calculation rigidity, a Finite Element Method considering time factor is set up for calculation of rod series statically indeterminate structures and corresponding program is developed. When using this method, non-linear analyze and analyze of time effect ofRC structures due to shrinkage, creep etc. can be conveniently carried out.5) Based on the fundamental principle of Heat Transfer, take advantage of Finite Element Theory, a time analyze method for analyzing temperature field and temperature effect is set up. A simplified calculation method is also developed for calculating temperature field and corresponding temperature effect for practical use .6) According to the constitutional characteristic of concrete materials, attacking model of CO₂ and Cl^-1 that can reflect the influence of the freeze-thaw cycling damage is developed, the traditional constant-carbonizing-factor-based calculation method is improved and prediction technology of service life of concrete structure in server environment also proposed in this paper. The computational simulation of the example indicates that service life of concrete structure underserver environment such as sea and cold zones will be obviously shortened, it is the effective measures to lengthen its service life by adopting high performance concrete and increasing concrete cover depth.7) The concept of time-dependent reliability and the calculating model are proposed in this paper .In addition, the durability optimum design method based on reliability analysis also is suggested. By the result of optimizing for standard design of 16m span railway concrete bridge (drawing number: 1023) are obtained following conclusions: l)climate, the property of concrete and the depth of cover have a great influence on durability;.2)the depth of cover should be chosen according to environmental condition and service life demand, adopt of the maxim allowable depth of cover is optimum economic alternative.8) With the researches on the first maglev train of our country and Metros construction projects in Shanghai, a series of tests have been carried out on temperature field and temperature effect of RC structures, shrinkage and creep fundamental factors of pumping concrete time-dependent deformation of RC beams. Tests' results tell that the analyze on the temperature field and temperature effect of model beams of maglev train track is reasonable, measured terminal shrinkagestrain of HFC is larger than the value which is specified in highway codes of China and the creep coefficient