Modeling of Bridging Law for Bundled Aramid Fiber-Reinforced Cementitious Composite and its Adaptability in Crack Width Evaluation

Tensile performance of fiber-reinforced cementitious composite (FRCC) after first cracking is characterized by fiber-bridging stress–crack width relationships called bridging law. The bridging law can be calculated by an integral calculus of forces carried by individual fibers, considering the fiber orientation. The objective of this study was to propose a simplified model of bridging law for bundled aramid fiber, considering fiber orientation for the practical use. By using the pullout characteristic of bundled aramid fiber obtained in the previous study, the bridging laws were calculated for various cases of fiber orientation. The calculated results were expressed by a bilinear model, and each characteristic point is expressed by the function of fiber-orientation intensity. After that, uniaxial tension tests of steel reinforced aramid-FRCC prism specimens were conducted to obtain the crack-opening behavior and confirm the adaptability of the modeled bridging laws in crack-width evaluation. The experimental parameters are cross-sectional dimensions of specimens and volume fraction of fiber. The test results are compared with the theoretical curves calculated by using the modeled bridging law and show good agreements in each parameter.

Due diligence: the risky risk management tool in international law

As a standard bridging law and other spheres of normativity, due diligence is pervasive across numerous areas of international law. This paper defines the features and functions of due diligence, illustrating how the concept's development reflects structural changes in the international legal order. Concerning their content, due diligence obligations can be separated into two overlapping types: procedural obligations and obligations relating to States' institutional capacity. Thus, due diligence serves to manage risks, compensate for States' freedoms being circumscribed through legalisation, expand State accountability and possibly stabilise the international order through ‘proceduralisation’. However, it is argued that due diligence cannot be characterised as a general principle of international law due to its diverse content in different fields of international law and its dependence on accompanying primary rules. Finally, it is contended that due diligence introduces certain risks, particularly by diluting States' substantive obligations and contributing to the rise of ‘informal’ international law.

Pullout Behavior of Bundled Aramid Fiber in Fiber-Reinforced Cementitious Composite

The tensile performance of fiber-reinforced cementitious composite (FRCC) after first matrix cracking is characterized by a tensile stress–crack width relationship called the bridging law. The bridging law can be obtained by an integral calculus of forces carried by individual bridging fibers considering the effect of the fiber inclination angle. The main objective of this study is to investigate experimentally and evaluate the pullout behavior of a single aramid fiber, which is made with a bundling of original yarns of aramid fiber. The bundled aramid fiber has a nonsmooth surface, and it is expected to have good bond performance with the matrix. The test variables in the pullout test are the thickness of the matrix and the inclined angle of the fiber. From the test results, the pullout load–slip curves showed that the load increases lineally until maximum load, after which it decreases gradually. The maximum pullout load and slip at the maximum load increase as the embedded length of the fiber becomes larger. The pullout load–crack width relationship is modeled by a bilinear model, and the bridging law is calculated. The calculated result shows good agreement with the experimental curves obtained by the uniaxial tension test of aramid–FRCC.