A sensor instrumentation method for dynamic monitoring of railway bridges

One of the most effective ways for investigating dynamic behaviour of mechanical and civil structures under service conditions is dynamic load testing. The outcomes of dynamic tests are vibration characteristics, and in particular modal parameters such as vibration mode shapes, frequencies, damping ratios. Dynamic diagnosis technique has been already used for many years in mechanical engineering. During the last decades a number of investigations have been performed introducing new dynamic monitoring techniques of civil infrastructures including bridges. Field experimental testing of new steel-concrete composite railway bridge was carried out to determine natural and forced vibration frequencies, corresponding mode shapes and damping ratios. The attention was focused on short-term dynamic monitoring of new innovative structure with the aim to investigate the implementation of sensor technique on real structures, to calibrate a FE model of the bridge that can be used for further simulations and as a result to give feedback to the design of similar structures. Field tests and numerical simulations were conducted using excitations induced by dropping a weight and by ambient traffic excitation loadings. Results of these investigations are presented in this paper

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

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. Gelžbetoninių konstrukcijų polimerinių apsauginių dangų projektavimas. II dalis. Eksperimentinė patikra Santrauka Gelžbetoninių konstrukcijų irimas dėl korozijos yra dažnas reiškinys. Konstrukcijos gali būti apsaugotos antikorozinėmis polimerinėmis dangomis. Norint efektyviai naudoti įvairias polimerines dangas, reikia nustatyti jų agresyviojoje aplinkoje ribinius būvius ir šių būvių patikrinimo metodiką. Straipsnyje pateikiami pusiau empiriniai dangoms projektuoti metodai, kurių naudojimas parodytas IKAS dangų, esančių skystojoje cheminėje aplinkoje, pavyzdžiu. Remiantis eksperimentiniais tyrimais ir jų duomenimis, nustatyti dangų irimo mechanizmai ir jų greitis, kurie panaudoti dangų parametrams apskaičiuoti deterministiniais ((5) ir (6) formulės ir 2 lentelė) ir tikimybiniais ((14), (15) ir (16) formulės) metodais. Parodyta įvairių projektavimo parametrų jautrumo įtaka. Svarbus dangoms reikalavimas yra jų atsparumas pleišėjimui ir sukibimas su betono paviršiumi. Pateikta formuojamų dangų traukumo įtempių ir išorės temperatūros pokyčių įtempių, įvertinant jų relaksacijos procesus, apskaičiavimo metodika ((19), (20), (22) ir (24) formulės). Pateikti polimerinių dangų tyrimai naudoti IKAS dangoms projektuoti, įvairių cheminių tirpalų gelžbetoniniams rezervuarams apsaugoti. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: gelžbetoninės konstrukcijos, polimerinės dangos, fizinis (cheminis) atsparumas, difuzija, traukumo ir temperatūriniai įtempiai, patikimumas

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

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. Santrauka Įvairios apsauginės dangos naudojamos gelžbetoninėms konstrukcijoms stipriai agresyvioje aplinkoje apsaugoti. Straipsnyje nagrinėjama daugiasluoksnė antikorozinė apsauga, susidedanti iš apsauginio barjero, betoninio apsauginio sluoksnio ir plieninės armatūros. Sistema modeliuojama kaip trijų nevienodų komponentų šaltai rezervinė sistema. Ši sistema yra neremontuojama. Tai atvejai, kai sistema sunkiai pasiekiama, remontas ilgai trunka arba brangus. Tariama, kad sistemos visų komponentų irimo intensyvumas yra eksponentinis ir skirtingas. Remiantis šiomis prielaidomis, naudojant Markovo suirties (atnaujinimo) teoriją, kai kurie svarbūs patikimumo rodikliai, tokie kaip sistemos patikimumas ir vidutinis laikas iki suirties, gali būti nustatyti. Skaitinis pavyzdys iliustruoja analitinio modelio taikymą ir jo jautrumą vertinant antikorozinės apsauginės sistemos patikimumą. First Published Online: 15 Oct 2010 Reikšminiai žodžiai: antikorozinė apsauga, neremontuojama sistema, rezervinė sistema, Markovo procesas, patikimumas, laikas iki suirties

A sensor instrumentation method for dynamic monitoring of railway bridges

One of the most effective ways for investigating dynamic behaviour of mechanical and civil structures under service conditions is dynamic load testing. The outcomes of dynamic tests are vibration characteristics, and in particular modal parameters such as vibration mode shapes, frequencies, damping ratios. Dynamic diagnosis technique has been already used for many years in mechanical engineering. During the last decades a number of investigations have been performed introducing new dynamic monitoring techniques of civil infrastructures including bridges. Field experimental testing of new steel-concrete composite railway bridge was carried out to determine natural and forced vibration frequencies, corresponding mode shapes and damping ratios. The attention was focused on short-term dynamic monitoring of new innovative structure with the aim to investigate the implementation of sensor technique on real structures, to calibrate a FE model of the bridge that can be used for further simulations and as a result to give feedback to the design of similar structures. Field tests and numerical simulations were conducted using excitations induced by dropping a weight and by ambient traffic excitation loadings. Results of these investigations are presented in this paper

Static analysis and simplified design of suspension bridges having various rigidity of cables

Increased deformability can be considered as the basic disadvantage of suspension bridges. One of the ways to increase the rigidity of a suspension bridge is to transfer a part of stiffening girder rigidity to a suspension main cable. To give the suspension bridge more stable appearance, the authors propose to use the cables of varying bending stiffness. The main cables can be made of standard section shapes or have a composite section. The object of this work was to study a method for analyzing and determining the internal forces in the main cables and stiffening girder under static loading to provide recommendations for designing suspension bridges with stiffened cables. Simple formulas are presented for determining displacements, internal forces and stresses in the main cable and stiffening girder. Finite element modeling was performed. The final part of the paper discusses design procedures for such suspension systems. An example of a pedestrian suspension bridge is appended. Santrauka Esminis kabamuju tiltu trūkumas ‐ didelis ju deformatyvumas. Deformatyvumui sumažinti autoriai siūlo dali standumo sijos lenkiamojo standžio perduoti kabamajam lynui. Baigtinio lenkiamojo standumo lynai gali būti daromi iš standartiniu valcuotuju profiliuočiu arba sudetinio skerspjūvio. Šio darbo tikslas ‐ pateikti supaprastinta metodika kabamojo tilto standaus lyno ir standumo sijos elgsenos analizei atlikti bei rekomendacijas tokiems statiškai apkrautiems tiltams projektuoti. Pateiktos paprastos formules lyno ir sijos poslinkiams, iražoms ir itempiams apskaičiuoti. Atliktas kabamosios tilto siste‐mos modeliavimas baigtiniais elementais. Aptartos tokiu kabamuju tiltu projektavimo procedūros. Pateiktas pesčiuju via‐duko kabamuju konstrukciju projektavimo pavyzdys. Reikšminiai žodžiai: kabamieji tiltai, standūs lynai, poslinkiai, iražos, BE modeliavimas, projektavimas, pesčiuju viaduka

Static behaviour analysis of masts with combined guys

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. Stiebų, turinčių mišriąsias atotampas, statinė elgsenos analizė Santrauka Aptariama originali plieninio stiebo konstrukcinė sandara, kurioje vietoje įprastinių vientisų atotampų taikomos mišriosios, turinčios atšakas, atotampos, sutelkiant dėmesį į statinės apkrovos įtaką stiebo elgsenai. Pagrindinis šio sprendinio privalumas – paslankiųjų atramų kiekio kamiene padidinimas, kas tiesiogiai daro įtaką stiebo stabilumui esant apkrovai. Statinės analizės metu buvo išnagrinėta pagrindinių komponuojamųjų geometrinių ir fizinių parametrų įtaka vieno atotampų lygio kamieno ruožo paslankiųjų atramų poslinkiams. Atlikta įprasto ir naujo tipo stiebo poslinkių ir įrąžų lyginamoji analizė. Reikšminiai žodžiai: stiebas, mišriosios atotampos, statinė apkrova, geometriniai ir fiziniai parametrai, elgsenos modeliavimas. First Published Online: 14 Oct 201

Influence of Functionally Obsolete Bridges on the Efficiency of Road Network. Part I: Obsolescence Characteristics and Assessment

Deterioration of road bridges is causing serious problems in many countries of the world. Extensive research is carried out on the structural deterioration and defects of bridges and considerably less attention is given for their functional obsolescence. Inadequate deck geometry and clearances of bridges due to the increasing traffic volumes lead to the traffic safety and economic problems and influence the efficiency of a whole road transportation system. Typical bridge obsolescence model is analysed. Classification of five obsolescence categories and the main factors showing the functional obsolescence of bridges is presented. They include the deck roadway geometry (width and alignment), safety measures (barriers and railings), vertical and horizontal clearances beneath the bridge, alignment of the approach roadway, and waterway adequacy. Parameters assessing the functional obsolescence of bridges and the additional owner’s and user’s costs are identified. Decision-making strategy for obsolete bridges is discussed

Influence of Functionally Obsolete Bridges on the Efficiency of Road Network. Part II: Case Studies

This study is the first practical step in Lithuania to identify the characteristics causing the bridges to be functionally obsolete. A bridge of which current deck geometric characteristics, safety barriers or railings, underclearances, and roadway approach alignment are deficient and not consistent with current design standards (or traffic demands) can be considered as functionally obsolete. In Part I of this paper the criteria of functionally obsolete bridges, deficiency categories and assessment of deficient structures are presented. The Part II reports experience in city bridge stock of 83 structures for a short period of 2–5 years on this subject. Surveying revealed that 58.5% of bridge stock shows minor or obvious signs of functional aging. Evaluation and rating of city bridge stock was undertaken. Illustrative examples of functionally obsolete bridges are presented. Recommendations for improvement of the geometrical characteristics of bridges in existing Lithuanian design codes are envisaged

Damage to concrete bridges due to reinforcement corrosion

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. First Published Online: 19 Dec 201

Deterioration of Bridge Deck Roadway Members. Part II: Condition Evaluation

One of the simplest ways of assessing existing structures is the use of rating marks, classes or grades for each bridge or its components. Different rating systems have been developed and used widely in many countries. Markovian models are often considered to represent the bridge deterioration process. In part I of this two-part paper results of experimental studies on the deterioration of bridge deck ancillary members are presented. This study was conducted to determine the condition assessment procedures and performance characteristics of bridge deck surfacing, expansion joints, and safety barriers. A simple rating system with a scale of 7 to 1 to diagnose the condition of bridge deck members in service is proposed. A Markovian process for physical deterioration of these members is used. Results from a simulation study using the real individual bridge components in City Vilnius are presented