Efficient semiparametric estimation of time-censored intensity-reduction models for repairable systems

The rate reduction models have been widely used to model the recurrent failure data for their capabilities in quantifying the repair effects. Despite the widespread popularity, there have been limited studies on statistical inference of most failure rate reduction models. In view of this fact, this study proposes a semiparametric estimation...

External surface cracked offshore pipes reinforced with composite repair system: A numerical analysis

This paper conducts a numerical analysis on the external surface cracked steel pipes reinforced with Composite Repair System. A three-dimensional finite element (FE) model is developed to calculate the Stress Intensity Factor (SIF) of the surface crack, and the crack growth process is evaluated by the Paris’ law. The effect of FRP-to-steel...

External surface cracked offshore steel pipes reinforced with composite repair system subjected to cyclic bending: An experimental investigation

In this paper, we experimentally studied the external surface crack growth in steel pipes reinforced with Composite System Repaired (CRS). CRS reinforced surface cracked API 5L X65 pipes were tested, containing three initial notch sizes and four reinforcement schemes. During the tests, the crack growth results, as well as the strain on the...

Numerical analysis on the SIF of internal surface cracks in steel pipes reinforced with CRS subjected to bending

In this paper, Composite Repair System (CRS) is applied to repair the circumferential internal surface cracked steel pipes subjected to bending. The Stress Intensity Factor (SIF) is quantitatively analysed by means of numerical simulations, and the crack growth rate is predicted by using the Paris’ law. First, the three-dimensional finite...

Long-term availability modelling of water treatment plants

Water treatment plants (WTPs) are characterised as complex configurations of repairable and deteriorating components. Previous studies have mainly focused on the average or steady-state availability of such systems while ignoring inherent characteristics like degradation. The current research proposes a two-level hierarchical model for long-term...

Long-term Availability Analysis of Water Treatment Plants: Complex Repairable Systems with Deteriorating Characteristics

Water Treatment Plants (WTPs) play a key role in assuring water availability to citizens and businesses. Long term availability of these plants is the interest of the asset manager of a WTP and can be influenced by maintenance strategies and modifications of the system. A WTP is characterized by a complex configuration and repairable,...

Moisture movement in cement-based repair systems monitored by X-ray absorption

In concrete repair systems, material properties in the repair material and interface are greatly influenced by the initial moisture content of the concrete (or mortar) substrate. In order to quantify moisture profiles inside the repair system, X-ray absorption was used. Preliminary studies are performed first to determine the absorption rate of...

Influence of interface and strain hardening cementitious composite (SHCC) properties on the performance of concrete repairs

In the construction industry the demand for repair and maintenance of concrete structures constantly increases. Still, the performance of current concrete repairs is not satisfactory and there is an urgent need for improvement. Understanding the damage development in a repair system, and how to predict, model and prevent its failure is critical...

Effect of Moisture Exchange on Interface Formation in the Repair System Studied by X-ray Absorption

In concrete repair systems, material properties of the repair material and the interface are greatly influenced by the moisture exchange between the repair material and the substrate. If the substrate is dry, it can absorb water from the repair material and reduce its effective water-to-cement ratio (w/c). This further affects the hydration rate...

Injecting a liquid bacteria-based repair system to make porous network concrete healed

Bacteria induced calcite precipitation has been proven to be effective in making concrete structure self-healing. In Microlab TU Delft, the concept has been enhanced by developing a liquid bacteria-based concrete repair system. The solution contains calcite precipitating bacteria, nutrients and buffer compound which may demonstrate high...

Injecting a liquid bacteria-based repair system to make porous network conrete healed

Bacteria induced calcite precipitation has been proven to be effective in making concrete structure self-healing. In Microlab TU Delft, the concept has been enhanced by developing a liquid bacteria-based concrete repair system. The solution contains calcite precipitating bacteria, nutrients and buffer compound which may demonstrate high...

Renewal Processes and Repairable Systems

In this thesis we discuss the following topics: 1. Renewal reward processes The marginal distributions of renewal reward processes and its version, which we call in this thesis instantaneous reward processes, are derived. Our approach is based on the theory of point processes, especially Poisson point processes. The idea is to represent the...