Constitutive Law of Concrete in early ages Including Semi-fluid State and Analysis on Initial Crack Problem after Casting

在这一年里，发展了混凝土的暂态本构关系，并尝试建立了数值问题的应用软件。重点研究了以下两个目标：一是用数学方法表示过渡混凝土的流动性；为了便于实际应用，流体介质的应力-应变关系被认为是以三维切线形式表示的，其中包括适当的均匀蠕变定律。这是因为即使是像瞬变混凝土这样的流体介质也有很小但不为零的剪切阻力。此外，为了使力平衡具有更好的数值收敛能力，减少计算时间，不用经典的塑性定理，而是用评价格子等效连续体方法(LECM)，给出了除时间相关部分以外的塑性行为的数值表达式。另一种是从塑性定理和各种实验两方面提出严格的本构模型。最后，通过对混凝土结构渗流收缩问题的数值分析，揭示了该软件的特点，发现与基于传统塑性理论的软件相比，该软件不仅能更明显地表达渗流收缩引起的应变局部化，而且具有更好的数值收敛能力，但由于对初应力问题的数值讨论不足，需要对各种情况下的初应力问题进行更多的数值分析和讨论。

In this year, constitutive law of concrete in transient state has been developed and application software to numerical problem has been tried to be created. Especially, following two targets are focused.One is to express fluidity of transient concrete mathematically. For the purpose of practical use, stress-strain relationship of fluid media is thought to be express in three dimensional tangential form including adequate homogeneous creep law. This is because even fluid media such as transient concrete has small but nonzero shear resistance. Moreover, numerical expression of plastic behavior except time dependent part is given by not classical plastic theorem but evaluating Lattice Equivalent Continuum Method (LECM) in order to have better numerical convergence of force equilibrium and to reduce computation time.The other is to present rigorous constitutive model in terms of both plastic theorem and various experiments.The aforementioned targets are almost completed. Finally, numerical analysis of transient concrete structure subjected to bleeding shrinkage is carried to reveal characteristics of software and it is found that the software can not only express strain localization induced by bleeding shrinkage more evidently but also have better numerical convergence of solution compared with the software based on conventional plastic theorem.However, as numerical discussion for initial stress problem is insufficient, much more numerical analysis of initial stress problem under various conditions should be carried and discussed.