Design Service Life Research Articles

МЕТОДИ НЕРУЙНІВНОЇ ДІАГНОСТИКИ РОЗТАШУВАННЯ МЕТАЛЕВОЇ АРМАТУРИ ШТИРОВИХ З’ЄДНАНЬ У ШВАХ ЖОРСТКИХ ДОРОЖНІХ ОДЯГІВ

Introduction. In the world-wide practice on construction of rigid road pavements significant attention has been given to jointed plain concrete pavements (JPCP) with transverse joints strengthened by dowel bars. Performance of JPCP is sufficiently affected by right alignment and location of dowel bars thereby the methods of non-destructive testing of dowel bar positioning have been gain in great importance. This paper represents analytical review of methods of non-destructive testing of dowel bar alignment and location emphasizing an attention on standard method using magnetic pulse induction which is applicable to testing of metallic bar position in concrete pavements. General Part. In the general part of this paper, several main aspects of reviewed test method were analyzed: the classification of dowel bars misalignment and their impact on pavement performance; the comparison of implemented methods of non-destructive testing of dowel bar positioning; possibilities of method of magnetic impulse induction and an approach to analytical evaluation of transverse joints dowel bar misalignment using magnetic image tomography; the usage of results of testing of transverse joints dowel bar position to eliminate dowel bars misalignment; examples of predictive estimation of results of testing of transverse joints dowel bar position and their impact on performance of JPCP. The reviewed method of testing and test results estimation concerns practice on application of two levels of performance (e.g. acceptable level and rejectable level) to evaluate the performance of each individual dowel bar or each doweled transverse joint and also a section of rigid road pavement with several consecutive transverse joints with restricted performance. Conclusions. 1. World-wide implemented standard method of non-destructive testing of dowel bar alignment and location allows to detect and to eliminate dowel bars misalignment thus ensuring required load transfer efficiency and international roughness index of rigid road pavements. The estimation of road pavement sections with several consecutive joints considering each joint performance allows to ensure the designed service life of road pavement. 2. Standard method of non-destructive testing of dowel bar alignment and location for transverse joints of rigid road pavement using magnetic pulse induction developed by American Society for Testing and Materials assures high precision of measurement of metallic bar position in doweled bar of concrete pavement joints and enables to detect five types of dowel bar misalignment. 3. In connection with the intensification of issues on construction of rigid road pavements in Ukraine as well as the high importance of the considering test method, an important task should be the development and implementation of an appropriate national standard.

Characterization of the Static, Creep, and Fatigue Tensile Behavior of Basalt Fiber/Polypropylene Composite Rods for Passive Concrete Reinforcement.

Fiber-reinforced polymer (FRP) composites are becoming more frequently adopted as so-called “corrosion-resistant” concrete reinforcement materials due to their excellent mechanical properties and formability. However, their long-term reliability must be thoroughly investigated in order to understand failure mechanisms and to develop service life models. This study is on the mechanical properties of a prototype basalt fiber-reinforced polypropylene (BFPP) rod under quasi-static and sustained loading. Static strength and modulus at elevated temperatures do not decrease significantly, but the variability in strength increases with temperature, as shown by a Weibull analysis. Creep behavior is typical of unidirectional FRP, where the creep rupture strength follows a power law. Fatigue at various stress ratios R reveals the sensitivity of composite strength to the matrix damage, which increases at lower values of R (i.e., higher stress amplitudes). These results are discussed in the context of service life and concrete structure design guidelines.

Assessment of technical condition of high-voltage overhead power transmission lines at the stage of their ageing

The organization of operation, maintenance and repair of the basic technological facilities of electric power systems (EPS), which are beyond their designed service life (hereinafter referred to as ageing facilities, or AFs) is one of the problems that determine the energy security of many countries, including economically developed nations. The principal cause of insufficient overall performance of AFs is the traditional focus of the EPS management on economic efficiency and the insufficient attention to reliability and safety of AFs. The tendency to nonlinear growth in the frequency of occurrence of unacceptable consequences in the EPS requires ensuring the operational reliability and safety of AFs. The averaged estimates of reliability and safety used at designing power facilities are not suitable for characterization of overall operational performance. Among the basic and the least investigated (in terms of operational reliability and safety) EPS facilities are overhead power transmission lines (OPL) with a voltage of 110 кV and above. This is for a reason. OPL are electric power facilities with elements distributed along a multi-kilometer line (supports, insulators, wires, accessories, etc.). That is what makes the organization of continuous monitoring of the technical condition of each of these elements, and, consequently, the assessment of operational reliability and safety, so problematic. A method is suggested for assessment of “weak links” among the operated OPL on operative intervals of time along with a method for assessment of the technical condition of OPL at examination of a representative sample.

Justifying the prolongation of the service life of the bearing structure of a tank car when using Y25 bogies

This paper substantiates the use of Y25 bogies under tank cars in order to prolong their service life. The reported study has been carried out for a tank car with rated parameters, as well as the actual ones, registered during full-scale research. Mathematical modeling was performed to determine the basic indicators of the tank car dynamics. The differential equations of motion were solved by a Runge-Kutta method using the Mathcad software package (USA). It was established that the use of Y25 bogies under a tank car with rated parameters could reduce the acceleration of its bearing structure by almost 39 % compared to the use of standard 18‒100 bogies. Applying the Y25 bogies under a tank car with the actual parameters reduces the acceleration of its load-bearing structure by almost 50 % compared to the use of standard 18‒100 bogies. The derived acceleration values were taken into consideration when calculating the bearing structure of a tank car for strength. The calculation was performed using the SolidWorks Simulation software package (France). The resulting stress values are 18 % lower than the stresses acting on the load-bearing structure of a tank car equipped with 18‒100 bogies. For the load-bearing structure of a tank car with the actual parameters, the maximum equivalent stresses are 16 % lower than the stresses when the 18‒100 bogies are used. The design service life of the load-bearing structure of a tank car was estimated taking into consideration the use of Y25 bogies. The calculations showed that the design service life of the bearing structure of a tank car equipped with Y25 bogies is more than twice as high as that obtained for 18‒100 bogies. The study reported here would contribute to compiling recommendations for prolonging the service life of the load-bearing structures of tank cars

Design Service Life of RC Structures with Self-Healing Behaviour to Increase Infrastructure Carbon Savings.

Corrosion of reinforced concrete (RC) structures costs the UK GBP 23b annually and is one of the main durability problems contributing to the development of rust, spalling, cracking, delamination, and structural deterioration. This paper intends to demonstrate the benefit of using tailored self-healing bacteria-based concrete for RC corrosion minimisation and service life increase. The purpose was to evaluate the enhancement in the lifespan of the structure exposed to a harsh marine microenvironment by utilising a probabilistic performance-based method. Comparison is made with the performance of a commercially available solution and in terms of embodied carbon impact. Three different concretes, using CEM I 52.5N, CEM II/A-D, and CEM III/A, were tested with and without an iron-respiring bioproduct (BIO) and an added admixture corrosion inhibitor (AACI). Results show that bioproduct significantly contributes to service life increase of RC structures with CEMIII/A. The repair solution with self-healing behaviour not only increases RC service life, but also enables us to decrease the required cover thickness from 60 mm to 50 mm in an XS2 chloride environment. In both XS2 and XS3 environments, a comparison of CEMIII/A+BIO and CEMII/A-D+AACI concrete shows the benefit of using bioproduct in corrosion inhibition context, besides contributing to an embodied carbon reduction of more than 20%.

Evaluation of Moisture and Decay Models for a New Design Framework for Decay Prediction of Wood

Performance-based, service-life design of wood has been the focus of much research in recent decades. Previous works have been synthesized in various factorized design frameworks presented in the form of technical reports. Factorization does not consider the non-linear dependency between decay-influencing effects, such as between detail design and climate variables. The CLICKdesign project is a joint European effort targeting digital, performance-based specification for service-life design (SLD) of wood. This study evaluates the feasibility of using a semi-empirical moisture model (SMM) as a basis for a digital SLD framework. The performance of the SMM is assessed by comparison against a finite element model (FEM). In addition, two different wood decay models (a logistic, LM, and simplified logistic model (SLM)) are compared. While discrepancies between the SMM and FEM were detected particularly at high wood moisture content, the overall performance of the SMM was deemed sufficient for the application. The main source of uncertainty instead stems from the choice of wood decay model. Based on the results, a new method based on pre-calculated time series, empirical equations, and interpolation is proposed for predicting the service life of wood. The method is fast and simple yet able to deal with non-linear effects between weather variables and the design of details. As such, it can easily be implemented as part of a digital design guideline to provide decision support for architects and engineers, with less uncertainty than existing factorized guidelines.

Service Life of Concrete Pedestal without Air Entrainment

Abstract Service life of nine wind power unit pedestals, which concrete grades between C45 and C55, were studied with four different service life models. The exact service life could be calculated only with two of them with the initial data. The service life models that were used in calculations: • Factor method • Deterioration and service life prediction of concrete subjected to freeze-thaw cycles in Na2SO4 Solution-method Service life models that were considered only at theoretical level: • FIB Bulletin 34 – Model Code for Service Life Design, and • An equation for determining freeze-thaw fatigue damage in concrete and a model for predicting the service life. The latter two methods are more theoretical, and they require laboratory tests to obtain more information before the calculations can be properly executed. This article concludes that damage to concrete due to freeze-thaw cracking is still poorly known and a sufficiently accurate service life model has not yet been developed for its computational modeling. Therefore, there is a need to develop a service life model suitable for Finnish climate and concrete grades, which could be used for estimating the damage rate of an existing concrete structure.

Service life and durability design of RC structures: general considerations and selected Southern African perspectives and experiences

ABSTRACT There is a growing trend to include service life (SL) and durability considerations in the design of reinforced concrete structures. This is partially a consequence of increasing deterioration of ageing concrete infrastructure worldwide and associated financial burdens and structural failures. Against this trend, this contribution critically explores the principles of SL and durability design and highlights the differences between SL modelling, SL prediction, SL design, and performance-based design, focussing on aspects related to reinforcement corrosion in concrete. Based on extensive research and practical experience, the Southern African perspective on concrete durability is then explored in more detail, in particular the South African performance-based design methods, associated SL modelling, and deterioration prevention methods. Based on chloride ingress measurements in-situ, a critique of design exposure classes for marine environments is presented, highlighting the need not only to consider chloride ingress, but also the various factors promoting reinforcement corrosion.

Comparison of Microbially Induced Healing Solutions for Crack Repairs of Cement-Based Infrastructure

Reinforced concrete crack repair and maintenance costs are around 84% to 125% higher than construction costs, which emphasises the need to increase the infrastructure service life. Prolongation of the designed service life of concrete structures can have significant economic and ecological benefits by minimising the maintenance actions and related increase of carbon and energy expenditure, making it more sustainable. Different mechanisms such as diffusion, permeation and capillary action are responsible for the transport of fluids inside the concrete, which can impact on the structure service life. This paper presents data on microbially induced repair and self-healing solutions for cementitious materials available in the contemporary literature and compares results of compressive strength test and capillary water absorption test, which are relevant to their sealing and mechanical characteristics. The results of the repair and self-healing solutions (relative to unassisted recovery processes) were “normalized.” Externally applied bacteria-based solutions can improve the compressive strength of cementitious materials from 13% to 27%. The internal solution based solely on bacterial suspension had 19% improvement efficacy. Results also show that “hybrid” solutions, based on both bio-based and non-bio-based components, whether externally or internally applied, have the potential for best repair results, synergistically combining their benefits.

Fatigue action on crane runway beams

The supporting structure of an overhead traveling crane is subject to cyclic loading. The crane runway beams are parts of this structure traveled over by the crane during each crane passage. Therefore, their fatigue resistance has to be verified according to structural Eurocode 3 in more than 30 countries that are members of European Committee for Standardization (CEN) and potentially more than 50 countriesaround the world. For the verification, the expected fatigue loading during the design service life has to be estimated. A new proposal is presented how to predict the fatigue loading of the crane runway beams based on the type of crane operation.

Reducing carbon dioxide emissions through structural health monitoring of bridges

Reducing greenhouse gas emissions including carbon dioxide (CO2) is central to minimizing the human contribution to global warming. Industrial activities and transportation are some of the main contributors to carbon dioxide emission. Bridges are the key element in the transportation system and many of them are reaching the end of their designed service life. Replacing bridges requires a significant amount of construction materials and equipment, which will lead to significant carbon dioxide emissions. In this work, we conclude that carbon dioxide emission can be reduced by applying structural health monitoring (SHM) instrumentation and techniques to bridge management. In this work, two medium span steel girder bridges have been used to study the impact of the application of SHM on the emitted carbon dioxide. From two monitored bridges traffic load strains were used to monitor the load distribution factor and neutral axis position of each girder. This data can be used to extend the service life of these bridges. By extending the service life of a bridge, the average annual carbon dioxide emission associated with the bridge is reduced. Considering the emission due to material production and construction, the carbon dioxide emission due to bridge reconstruction will decrease by 9–17% under the assumption that the application of SHM will extend the service life of a bridge by 5–10 years. Data from Federal Highway Administration (FHWA) for the state of Iowa, which includes the number of structurally deficient bridges, was used to estimate the short-term and long-term cumulative CO2 emission for a fleet of bridges. It was concluded that if all structurally deficient bridges (rating 3 or less) in Iowa were replaced for the 2000–2019 time period, the cumulative CO2 emission would have been 4,38,483 tonnes. However, if SHM were to be applied and extended the service life of 80% of these bridges by 5 or 10 years the total emission would have been reduced to 2,84,048 tonnes or 1,75,695 tonnes.

Justification of Safe Operation of Rolling Stock by the Lifetime of Its Bearing Structures

The problem of providing strength and reliability of rolling stock bearing structures which include welded and cast parts of bogie frames and bodies of cars and locomotives, as well as brackets and attachment points for their equipment and traction drive units, is one of the most important in the design, construction and operation. The development of high-speed and heavy-haul traffic, as well as the introduction of requirements for determining the design service life and life time of railway transport facilities, make the above task even more urgent. The influence of the operational loading characteristics of the object on the safety factor of fatigue strength and its depletion: amplitudes of cyclic stresses, frequencies of their change, parameters characterizing the intensity of the rolling stock operation (number of loading cycles, speed of movement, average daily mileage) is shown based on the results of computational and experimental studies carried out with running dynamic and strength tests of locomotives at all operating speeds of their movement in operation.

Best practice in the management and protection of concrete assets

While reinforced concrete construction has boomed over the past 70 years, forensic analysis of failures shows that many structures have not achieved the design service life due to poor durability. This can primarily be attributed to a lack of understanding about durability design, poor construction practices and poor life-cycle maintenance, resulting in unexpected deterioration and damage that requires intervention. Exposure to chloride ions continues to present the construction industry with the greatest challenges. In Europe, EN 206 sets durability performance criteria for reinforced concrete under normal exposure environments, supplemented by national recommendations. Increasingly, infrastructure is being built either in environments that are so hostile to reinforced concrete or with service design lives that are so long, that they are outside the scope of European standards. For design in hostile environments, both within Europe and around the world, performance-related durability methods have been adopted, using predictive ingress models over extended service lives. However, even then, the fundamental risk remains as to whether what the designer intended, through the various cement and cover combinations, will be achieved in practice by the contractor’s workforce and site practices. This paper explores the lessons from durability failures of reinforced concrete and examines how performance can be modelled and enhanced in extreme environments and assured by effective corrosion monitoring and management strategies.

Failure analysis of fractured motor bolts in high-speed train due to cardan shaft misalignment

Motor of high-speed train is normally connected with suspending devices through bolts. This paper presents an investigation of six motor connecting bolts, based on GB/T 3077 standard and strength grade of 8.8, which fractured at the thread close to the contact surface of motor and suspending device before the designed service life. The investigation includes macro examination, chemical compositions analysis, tensile tests, hardness tests, metallographic examinations were used to analyze the cause of fracture. The results revealed that the strength and material of bolts met the standard, no metallurgical defect was found in examination, and the bolts fractured were due to alternating load. According to the spectrum of acceleration signal measured by the sensor mounted on the motor housing and subsequent inspection of the cardan shaft and rotor of motor, revealed the alternating load is caused by misaligned cardan shaft. Further dynamic analysis shows that the rotation of misaligned cardan shaft resulted in huge unbalance force. To confirm the findings, finite element analysis on the bolts subjected to pre-tensile load reveals that the materials at the bottom surface of the first thread suffered high alternating stress and reaches the fatigue limit. From the above findings, this paper proposes an innovative strategy to avoid similar accidents of high-speed train suspending devices.

Experimental Investigation of Surface Preparation on Normal and Ultrahigh-Performance Concrete Interface Behavior

Abstract Many bridges in the United States are classified as structurally deficient and many others are nearing the end of their design service life, necessitating robust and durable bridge rehabil...

Influence of time-varying attenuation effect of damage index on seismic fragility of bridge

Fragility as one of the most effective methods to evaluate seismic performance, which is greatly affected by damage index. Taking a multi span continuous rigid frame offshore bridge as an example. Based on fragility and reliability theory, considering coupling effect of time-varying durability damage of materials and time-varying attenuation effect of damage index to analyze seismic performance of offshore bridges. Results show that IDA curve considering time-varying damage index is obviously below that without considering; area enclosed by IDA of 1# pier and X-axis under No.1 earthquake considering this effect is 96% of that without considering. Area enclosed by damage index of 1# pier and X-axis under serious damage with considering time-varying damage index is 90% of that without considering in service period. Time-varying damage index has a greater impact on short pier when ground motion intensity is small, while it has a great impact on high pier when the intensity is large. The area enclosed by fragility of bridge system and X-axis under complete destruction considering time-varying damage index is 165% of that without considering when reach designed service life. Therefore, time-varying attenuation effect of damage index has a great impact on seismic performance of bridge in service period.

Time-dependent load transfer behavior of grouted anchors in laterite

The load transfer behavior of grouted anchors is time-dependent under long-term (creep) load. This study aims at investigating the time-dependent behavior of grouted anchors in laterite by both physical model test and theoretical simulation. A laboratory creep pullout model test of full-length-bond grouted anchor in laterite was carried out using a special developed apparatus. The creep pullout load–displacement response at anchor head and time history curves of axial strain were tested and presented. The creep behavior on the grout - soil interface was simulated using Merchant rheological model in theoretical simulation. By comparing the experimental data with predictions, the applicability of the proposed theoretical method was validated, and the time-dependent load transfer behavior of grouted anchors was discussed. The impacts of five model parameters on the time-dependent pullout response were further analyzed by parametric studies. It revealed that the tensile force distribution tends to be linear, and the shear stress distribution towards uniformity as time elapsed. Additionally, the time-dependent load transfer behavior for grouted anchors is influenced by the above parameters in various levels. This work provides insights into understandings of time-dependent behavior, and facilitates the service life design practice for grouted anchors embedded in laterite.

Probabilistic Assessment of the Safety of Main Cables for Long‐Span Suspension Bridges considering Corrosion Effects

This paper presents a reliability analysis to assess the safety of corroded main cables of a long‐span suspension bridge. A multiscale probability model was established for the resistance of the main cables considering the length effect and the Daniels effect. Corrosion effects were considered in the wire scale by relating the test results from accelerated corrosion tests to the corrosion stages and in the cable scale by adopting a corrosion stage distribution of the main cable section in NCHRP Report 534. The load effects of temperature, wind load, and traffic load were obtained by solving a finite element model with inputs from in‐service monitoring data. The so‐obtained reliability index of the main cables reduces significantly after operation for over 50 years and falls below the design target value due to corrosion effects on the mechanical properties of the steel wire. Multiple measures should be taken to delay the corrosion effects and ensure the safety of the main cables in the design service life.

Research on Safety performance Evaluation method of Portal Crane based on Reliability Evaluation and Risk Assessment

In recent decades, with the vigorous development of shipping and transportation logistics industry, a large number of portal cranes have been installed in the ports of our country for production, and some of the equipment has approached or even exceeded its designed service life, and there is a great hidden danger of safety in the continued use of the equipment. This paper discusses a safety performance evaluation method of portal crane based on analytic hierarchy process (AHP). Through the determination and measurement of evaluation index, the safety condition of equipment can be obtained. according to the value of equipment safety condition, the safety performance can be classified, and the user and management organization can respond effectively according to the safety performance level of equipment, and the risk caused by long-term service of equipment can be effectively eliminated.

Research on Structural reliability and reliability sensitivity of EMU pantograph

Due to the uncertainty of the contact state between the pantograph and the power grid when the EMU is running at high speed, as well as the influence of road conditions and environment, the external load applied to the pantograph and the material properties of the pantograph have certain randomness, thus affecting the current collection quality of the pantograph and the service life of the carbon slide plate. Taking a certain type of EMU single arm pantograph as the research object, a three-dimensional model is established, ANSYS Workbench software is used to carry out the finite element analysis to determine the dangerous point and its stress response; the simulation samples of material properties and stress of dangerous points are obtained by using sampling method and test design method based on the principle of normal distribution; the reliability index and reliability of pantograph structure strength are analyzed, based on the random perturbation method and the first-order second- moment method, and using the simulation sample data extracted by Latin hypercube sampling, and the reliability accuracy is verified by Monte Carlo method. Based on the definition of reliability sensitivity, the influence degree of each input variable on the reliability change of pantograph structure is determined as follows: external load > Poisson’s ratio > material density > elastic modulus, which provides reference for improving the reliability, service life and structural optimization design of pantograph