Increase in treatment of retinopathy of prematurity in the Netherlands from 2010 to 2017

Purpose: Compare patients treated for Retinopathy of Prematurity (ROP) in two consecutive periods. Methods: Retrospective inventory of anonymized neonatal and ophthalmological data of all patients treated for ROP from 2010 to 2017 in the Netherlands, subdivided in period (P)1: 1-1-2010 to 31-3-2013 and P2: 1-4-2013 to 31-12-2016. Treatment characteristics, adherence to early treatment for ROP (ETROP) criteria, outco

Computational Aspects of Biaxial Stress in Plain and Reinforced Concrete

Civil Engineering and Geoscience

Plasticity and damage based smeared-crack models for finite element analysis of fracture in plain concrete and rock

Various models for describing smeared cracking in plain and reinforced concrete are discussed. A rigorous categorisation is made and some interrelations are shown. Differences and similarities between the formulations are illustrated by means of an elementary example subject to a non-proportional loading path and via a crack propagation problem in plain concrete

A composite plasticity model for concrete

A composite yield function is used to describe the behavior of plain and reinforced concrete in biaxial stress under monotonic loading conditions. A Rankine yield criterion is used to monitor the in-plane tensile stresses and a Drucker Prager yield function controls the compressive stresses. A good agreement with experimental data for biaxial stress conditions in concrete can thus be obtained. The approach is particularly powerful for the numerical analysis of concrete structures, either plain or reinforced, which are predominantly in tension compression biaxial stress states. Initiation of cracking in such areas frequently leads to brittle, uncontrollable failure (splitting cracks), which can often not be handled by existing approaches. The proposed Euler backward algorithm based on the composite yield function and enhanced by a consistent linearization of the integrated stress strain relation for use within a Newton Raphson method at the structural level, is extremely robust for this particular class of problems

Constitutive model for reinforced concrete

A numerical model is proposed for reinforced-concrete behavior that combines the commonly accepted ideas from modeling plain concrete, reinforcement, and interaction behavior in a consistent manner. The behavior of plain concrete is govern by fracture-energy-level-based formulation both in tension and in compression. In the presence of reinforcement, the fracture energy level is assumed to be distributed over a tributary area that belongs to a crack. The crack spacing is estimated using accepted CEB-FIB recommendations. The application of this model to reinforced-concrete panels and shear walls gives good simulations of the failure behavior. [23 Refs; In English

Plasticity and damage based smeared-crack models for finite element analysis of fracture in plain concrete and rock

Various models for describing smeared cracking in plain and reinforced concrete are discussed. A rigorous categorisation is made and some interrelations are shown. Differences and similarities between the formulations are illustrated by means of an elementary example subject to a non-proportional loading path and via a crack propagation problem in plain concrete