Theoretical and Experimental Study on Long-Term Structural Characteristics of Steel-Concrete Composite Slabs, Prestressed in Both Directions

摘要

Today, the major concern for civil engineers and scientists in applied mechamics of steel-concrete composite structures, is the failure of the reinforced and prestressed steel-concrete composite to meet the design and service life of structures. This paper describes the present ongoing numerical and experimental analysis model used to evaluate the structural long duration flexural and nonlinear creep characteristics of reinforced steel-concrete composite slabs, prestressed in both directions. This present ongoing study is so actual, as it is recognised that little information is available on the time dependent factors like the matrix (concrete) creep, shrinkage and loss of stress, in relation to bi-directional prestressing of reinforced steel-concrete composite slabs, with high yield tendons, subjected to long-term service loads. This theoretical and experimental study relates to the details of a unified design and tests procedure for analytical prediction of various durability and quality structural characteristics of the said reinforced and prestressed composite slabs. This analytical procedure is aimed to predict the quality, stiffness, strength and durability at the planning phase, the nonlinear creep behaviour of these said members. This present study, according to applied mechanics of reinforced and prestressed steel-concrete composite structures, has been based on nonlinear differential equations of the matrix creep theory which reflects the correlation between the matrix stress and strain by its modulus of elasticity, using the nonlinear strain function and the well-known geometrical preconditions of the theory of elasticity concerning thin plates with small flexural deformations. For structural and crack predictions, the well-known virtual work principles have been used to estimate (a) transient bi-directional strains due to the matrix creep and shrinkage, (b) the resulting time-dependent bi-directional stress redistributions, as well as (c) bi-directional displacement variations in the slabs and finally (d) bi-directional prestressing losses in the prestressed high yield tendons. The concrete shear stresses have been evaluated by the well-known principle of Juravsky. The finite-difference method based on the displacement formulation has been successfully used to solve the systems of nonlinear equilibrium differential equations.