Addition of High Performance and Multi-Functions to Fiber Reinforced Concrete

在本研究中，我们打算建立混凝土拉伸软化图的确定方法，然后讨论具有显著弯曲硬化区的高性能纤维增强混凝土的断裂行为。(1)张力软化图的确定方法基于试验荷载-位移曲线的多线性近似法，提出了一种精确确定混凝土张力软化图的方法。作为加载试验中测得的试件位移，裂缝张开位移优于加载点位移，因为裂缝张开位移不受试件支撑点沉降的影响，易于测量。(2)高性能纤维增强混凝土除具有高抗弯强度（20mpa）和显著硬化区的高性能芳纶纤维增强混凝土外，还开发了含有大量钢纤维或维纶纤维（按体积计可达6%）的高性能纤维增强混凝土，并报道了其性能。在混凝土梁试件的弯曲试验中，当峰值荷载大于起裂荷载时，梁侧表面出现多重裂缝。研究了基于虚拟裂缝模型的拉伸软化图在纤维混凝土中的适用性。对于钢纤维混凝土，当纤维含量小于2%时，由于其受弯断裂行为受单裂纹控制，故虚拟模型适用。然而，该模型不适用于钢纤维含量超过4%的混凝土，因此不能用拉伸软化图来评价混凝土的性能。

In this study, we intended to establish a determination method of tension softening diagrams of concrete and then discuss the fracture behavior of high performance fiber reinforced concrete which has a remarkable hardening region in bending.(1) Determination Method for Tension Softening DiagramsWe proposed a precise determination method of tension softening diagrams of concrete based on the poly-linear approximation method from experimental load-displacement curves.As a specimen displacement measured in loading tests, the crack opening displacement is superior than the loading point displacement, because the crack opening displacement is free from the settlement of the supporting points of specimens and can be easily measured.(2) High Performance Fiber Reinforced ConcreteIn addition to the high performance aramid fiber reinforced concrete with high flexural strength (20 MPa) and a remarkable hardening region, high performance fiber reinforced concrete having high amount of steel or vinylon fibers (up to 6% by volume) is developed and their properties are reported.In bending tests of concrete beam specimens, when the peak load is higher than the crack initiation load, plural cracks are observed on the beam side surfaces.The applicability of the tension softening diagrams based on the fictitious crack model to fiber reinforced concrete is investigated. In the case of steel fiber reinforced concrete, the fictitious model is applicable when the fiber content is less than 2 %, because the flexural fracture behavior is governed with a single crack. However, the model can not be applied for concrete with more than 4 % of steel fibers and therefore the properties can not be evaluated with the tension softening diagrams.