Zenonas Kamaitis

Modelling of corrosion protection for reinforced concrete structures with surface coatings

Abstract Corrosion is a serious problem for the durability of reinforced concrete structures. These structures need to be protected from corrosion in a variety of exposure conditions ranging from atmospheric to continuous immersion in water or chemicals. One of the ways to protect reinforced concrete structures from corrosion is to use protective coatings. The surface barriers of non‐degradable materials are able to slow down considerably the rate of deterioration of concrete structures and to overcome most durability problems associated with external attack. Design of durability of concrete structures with protective coatings needs to be established. In this paper a general framework for service life prediction and reliability evaluation of anticorrosion protective system (CPS), which is represented by protective surface barrier, concrete cover, and steel reinforcement itself of reinforced concrete structures, is presented. This approach is based on a reasonable understanding of the main degradation proc...

Modelling of corrosion protection as standby system for coated reinforced concrete structures

Abstract Various protective barriers are used in practice to protect reinforced concrete structures in severely aggressive environments. In this paper, we consider a multi‐component corrosion protection system (CPS), taking into account the performance of protective surface barrier, concrete cover and steel reinforcement, which is modelled as a three‐unit of non‐identical components cold standby system. The system is non‐maintained. This is the case when the system is not easily accessible for repair, repair; is time‐consuming and costly. In this system it is assumed that degradation rates of all components are exponential and different. Under these assumptions, using the Markovian degradation process, some important reliability indices such as the system reliability and mean time to failure are defined. In addition, we present simulation results to substantiate the analytical model and to demonstrate the sensitivity analysis to estimate protection system reliability.

Structural design of polymer protective coatings for reinforced concrete structures. Part I: Theoretical considerations

Abstract In a number of situations reinforced concrete structures must be protected by barrier materials to prevent contact with aggressive agents. One of the ways to protect concrete structures from corrosion is to use protective polymer coatings. Polymers as coating materials are not totally resistant and impermeable to all aggressive agents. Gases, vapors and liquids penetrate into a polymer so that the polymer mass swells and eventually disintegrates. However, the penetration/disintegration progresses at a much lower rate than that in the concrete. Surface coatings are able to reduce considerably the penetration, to slow down the rate of deterioration of concrete cover and to overcome most durability problems associated with external attack. In this article the mechanism of degradation of polymer coatings are analyzed. Methodology and predictive models for the degradation over time caused by aggressive actions of polymer coatings are presented. Proposed models can be applied to design of polymer coati...

Structural design of polymer protective coatings for reinforced concrete structures. Part II: Experimental verification

Abstract The ingress of various gases, liquids and ions from the environment is responsible for the deterioration of concrete structures. A large number and variety of protective surface treatments and coatings on the base of polymers have been developed for application to concrete surfaces in those instances, where special protection against aggressive attack is necessary. At the same time, new protective systems are continually appearing, whose adaptability to specific environments must in every case be proved. Semi‐empirical predictive models for the deterioration over time are presented enabling design of coatings with required barrier properties. This paper describes the performance of a system based on inden‐coumarone resins over a wide variety of exposures and application conditions and presents recommendations for design of such protective coatings.

Static behaviour analysis of masts with combined guys

Abstract The purpose of this study was to develop a new type of guyed mast that incorporates a complex guy cable system with a particular focus on the effect of static loading on the response mast behaviour. The intension of such solution is to increase a number of elastic supports for the mast shaft that will impact on its stability under loading. The static analysis of a one‐level guyed mast has been undertaken. The effects of geometrical and physical design parameters on the displacements of the mast were determined. The analysis is illustrated with two‐guyed masts: the bending moments and lateral displacements were determined for a typical guyed mast and guyed mast with combined guys.

Numerical analysis of the effects of the bending stiffness of the cable and the mass of structural members on free vibrations of suspension bridges

AbstractThe article determines natural frequencies of vibration and the corresponding mode shapes of a suspension bridge with the varying bending stiffness of cables and examines variations that occur in these characteristics with respect to parametric changes in the bridge. A single span suspension steel footbridge with flexible cables has been selected as an initial model used for studying the dynamic characteristics of a suspension system. With the help of the finite elements (FE) method, parameter studies of the bridge model are presented in which vibration characteristics are studied as a function of structural and material parameters such as the flexural stiffness of the cable and the mass density of structural components. It has been generally found that the bending stiffness of the main cable contributes to a considerable effect on natural frequencies for this type of the suspension system. A simplified expression of predicting natural bending frequencies of the suspension bridge taking into accou...

Damage to concrete bridges due to reinforcement corrosion: Part II-Design considerations

Abstract The mechanisms of reinforcement corrosion in concrete are the subject of extensive research. Although reliable methods for predicting the corrosive deterioration of concrete structures do not yet exist. This paper describes the durability problem of reinforced concrete bridges based on the mechanisms of carbonation depth or chloride profile. The deterioration model considering concrete carbonation, chloride penetration and concrete cover cracking is adopted to describe the service life of concrete structures. The corrosion models include environmental conditions, concrete carbonation or chloride diffusion rates, quality of concrete cover, steel corrosion rates and many other factors that make the predicting of service life of structures extremely difficult. Finally, the author gives the details of the methods of durabilio/ verification and the proposals for its including in the national standards and practical guides.

Technical and economical effectiveness of the combined guys mast

Santrauka Straipsnyje aptariama nauja plieninio stiebo konstrukcija, kurioje taikomos kombinuotosios atotampos. Analizuojamas sios naujos konstrukcijos techninis ekonominis veiksmingumas pagal medžiagu sanaudu kriteriju. Pateikiamos analizines israiskos racionaliems stiebo kamieno lenkiamiesiems momentams apskaiciuoti ir rekomendacijos atotampu tvirtinimo koordinatems nustatyti. Atliktu skaitiniu eksperimentu parodyta, kad nauju kombinuotuju atotampu taikymas leidžia sumažinti bendrasias stiebo medžiagu (plieno) sanaudas.

Damage to concrete bridges due to reinforcement corrosion: Part I. Site investigations

Corrosion of reinforcement initiated by concrete carbonation and chloride contamination is the most common type of deterioration of concrete bridges. Based on the authors experience a number of cases is reported in which the corrosion of ordinary and prestressed reinforcement as well as the causes and consequences of deterioration observed are presented. Investigations have shown that the main reasons are: insufficient concrete cover, poor quality of concrete, and ingress of aggressive salts. The carbonation depth must be related to the histogram ofrebar cover depths and the probability of their coincidence can be predicted. The monitoring of tendon conditions in prestressed concrete precast post-tensioned segmental bridge decks shows that the voids and the water are often present in the ducts leading to the local rusting of tendons. The wires used in tendons are liable to fail in tension that was observed in some prestressed concrete bridges. Unfortunately, no reliable procedures of determining...