Assessment Of Residual Strength Research Articles

Residual strength assessment of a heat straightened ASTM A 7 Steel I-section member exposed to a fire event

Heat straightening is an efficient and cost-effective method of repairing steel members that have experienced impact or fire-induced deformations. Postfire investigations have shown that fire exposure can cause considerable loss of residual mechanical properties. Beyond the fire event itself, additional heat applied to the member during the straightening process can, potentially, even further modify the mechanical properties of steels. This study aims to evaluate residual mechanical behavior at zones of maximum heat-induced distortion representative of both the fire event and the heat-straightening repair of a fire-damaged steel I-section. The study further aims to independently observe heating patterns, working temperatures, and external jacking forces during heat straightening. The fire-damaged member was restrained in three-point bending with fork boundary conditions simulating service conditions for a discretely braced bridge stringer. Results revealed that the cumulative effect of both the fire and the repair caused measurable differences in mechanical properties compared with an undamaged portion of the member, but mean properties still exceeded ASTM International’s ASTM A 7 product and the AASHTO nonfracture-critical toughness requirements. Supplemental metallographic analyses revealed no measurable alteration in metallurgical phase composition or grain size of the steel, indicating that heat straightening would have been a viable repair solution to keep the member in service.

Evaluating Residual Strength of RCC Tanks Affected by ASR Using NDT Methods

This case study focuses on the groundwater level tanks (GLR) located in Netra Village, 35 km from Jodhpur, on Nagour Road. The investigation revealed that people and livestock in the area were grappling with water scarcity issues. Non-Destructive Testing (NDT) methods were employed to assess the residual strength of three tanks in the region. The results showed that Tank-1 had a residual strength of 35.41%, Tank-2 had 63.08%, and Tank-3 had 53.8%. Alkali-silica reaction (ASR) poses a significant threat to the structural integrity of concrete tanks, necessitating accurate and non-destructive methods for residual strength assessment. This research paper delves into the effectiveness of NDT methods, specifically rebound hammer and Ultrasonic Pulse Velocity (UPV), in evaluating the residual strength of ASR-affected tanks. Through an extensive review of literature, case studies, and experimental data, this study aims to shed light on the practical application of rebound hammer and UPV for ASR assessment in tank structures. The paper discusses the principles, advantages, and limitations of each NDT method, emphasizing their ability to detect ASR-induced damage and predict the remaining structural capacity of tanks. Moreover, the research addresses the challenges associated with implementing rebound hammer and UPV techniques in ASR-affected environments, offering recommendations for enhancing their reliability and accuracy. By harnessing the combined capabilities of rebound hammer and UPV, engineers and asset managers can make well-informed decisions regarding the maintenance, repair, and retrofitting of ASR-affected tanks, ensuring their long-term safety and functionality in critical infrastructure applications.

A simple direct current model for residual bond strength assessment of embedded rebars in thermally damaged concrete

Fire events are highly fatal to human lives and properties, and should be considered at structural design phases. Concrete structures are essentially fire resistant up to certain level, beyond that structural components would degrade away from their design values. Residual capacities of fire exposed structures should be properly assessed before strengthening tasks can be carried out. Among those, the residual bond strengths between reinforcing bars and concrete are of particular importance because they determine the mechanical performance of all reinforced concrete components. This study focused on proposing novel nondestructive approaches to assess the residual bond strengths after thermal exposures. Specifically, a simple direct current (DC) model was implemented to yield electrical resistivity indices that can closely reflect the bond strength degradations up to 400 ℃. DC polarization measurements were split into three phases through which each index induced the degradations differently. Capability and efficiency of the DC indices to assess residual bond strengths of thermally damaged concrete were analyzed and discussed. Results presented have suggested that the proposed DC approach performed better than using residual compressive strengths to assess residual bond strengths, and was more advantageous for its nondestructive features.

Assessing critical fracture energy in mode I for bonded composite joints: A numerical–experimental approach with uncertainty analysis

The manufacturing process of composite structural components involves the assembly of composite parts using adhesives, which introduces variations in the geometrical and mechanical properties of bonded joints. The fracture energy under mode-I loading ( G I c) is a parameter used to predict crack propagation and evaluate the residual strength of the joint. This work proposes a numerical-experimental procedure to determine G I c in mode I, while considering the uncertainties inherent in the manufacturing process of bonded joints. The proposed procedure employs a three-dimensional finite element model to simulate a double cantilever beam test, using finite element commercial software. The cohesive zone model is applied to simulate the mechanical behavior of the adhesive, and experimental data are used to feed the computational model. A Plackett-Burman design is performed to reduce the number of experiments and evaluate the effect of the main influence parameters. Force-displacement curves are obtained, the compliance-based beam method is applied to determine G I c in mode I, employing both trapezoidal and triangular traction-separation laws. The results are thoroughly examined, taking into account the potential strengths and limitations of the proposed procedure, particularly in its application to predicting the behavior of bonded composite joints under mode I loading conditions. The proposed approach can help to understand the uncertainties effect related to the manufacturing process of bonded joints on G I c values, and improve the reliability of predicting crack propagation and residual strength assessment in bonded joints.

High-fidelity post-impact residual strength assessment for composite aircraft sustainment

AbstractHigh-fidelity simulation tools have significant potential to support composite aircraft sustainment, though further study is required on incorporating the complex impact damage field. In this paper, compressive residual strength assessment is investigated using the high-fidelity computational tool BSAMTM. The experimental impact damage was mapped and modelled at a high-fidelity level, which included ply-by-ply definition of the geometry of the impact indentation, fibre fracture in the plies and delamination in ply interfaces. It was shown that applying a small lateral displacement or ‘pseudo-impact’ step was highly effective in generating matrix cracks in the impact region, which provided a suitably realistic representation of the interconnected damage map through-the-thickness. It was found that inclusion of all damage modes in the post-image damage map at a high-fidelity definition was essential due to the strong degree of interaction between damage modes. The results support improved sustainment of defence platforms, through enhanced predictive capability and understanding.

Probabilistic residual strength assessment of smart composite aircraft panels using guided waves

Typical prognosis methods in Structural Health Monitoring (SHM) link the degradation mechanisms to the extracted health indicators. Such approaches however do not provide estimations on the current strength loss when a new damage is detected. This study presents a framework that enables the SHM-informed asset integrity management of composites. First, the integrated guided wave based SHM system is used to inform on the existence, location and size of the damage and subsequently, the residual strength of the structure is predicted. The framework combines physics-based and data-driven models to mitigate the incompleteness of the former and address issues relating to the representativeness in the training datasets of the later. Detailed finite element models are used to create a digital representation of the structure while a building-block program is initiated to quantify and propagate the uncertainties observed experimentally. A 1.6 m composite panel with a skin-stringer delamination, equipped with a network of 24 piezoelectric transducers, is used as a case study to demonstrate the prognostic capabilities of the framework. The framework estimated the damage size with a mean absolute percent error (MAPE) of approximately 10% while the residual strength of a destructively tested damaged panel was predicted with a MAPE of 5%.

Theoretical and numerical study on residual strength of worn casing considering wellbore curvature

Casing wear induced by frictional contact of rotating drill string with casing, will lead to casing structure integrity failure, casing strength degradation, well life shortening and huge economic loss. Logging practices and theoretical calculations have found that casing wear is mainly concentrated in the curved section with large wellbore curvature. The additional bending load in curved section will result in further reduction of casing strength along with wear defects. Therefore, it is of great significance to quantitatively evaluate the residual strength of worn casing, especially in curved section. To solve this problem, mechanical analysis is carried out for the cross section of both single size wear and compound wear. The expressions for residual burst strength, collapse strength and tensile strength are derived. Considering the axial stress generated by casing bending in curved section, the modified expressions of residual strength are obtained. Finite element verification indicates that the theoretical calculation model provides satisfactory prediction accuracy under different wellbore curvature. Using the established models, the effects of wear depth and wellbore curvature on stress distribution and bearing capacity are revealed systematically. Remaining burst strength and collapse strength steadily decline as casing wear depth increases, and the change law is in good agreement with a linear connection. When inner pressure and outer pressure are both constant, von Mises stress increases with increasing of wellbore curvature, indicating that the bearing capacity of casing will be greatly reduced under the combined effect of wear and wellbore curvature. Negligence of wellbore curvature will contribute to over-estimation of casing strength. Field application of a direction well is also carried out, which indicates that the existence of bending stress will lead to further reduction of casing strength. But the effect of wellbore curvature is obvious only if wellbore curvature is large enough. This research may serve as both a theoretical framework and a practical foundation for the assessment of worn casing residual strength in directional wells.

Inner damage identification and residual strength assessment of a 3D printed tunnel with marble-like cementitious materials using piezoelectric transducers

Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels. In this work, an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional (3D) printing technique and then loaded to simulate its failure mode in the laboratory. Lead zirconate titanate piezoelectric (PZT) transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing. A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading. Results show that as the load increased, main cracks firstly appeared above the tunnel roof and below the floor, and then they coalesced into the tunnel boundary. Finally, the tunnel model was broken into several parts. The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks, and then shifted backwards after new cracks appeared. An overall increase in the root-mean-square deviation (RMSD) calculated from conductance signatures of all the PZT transducers was observed as the load (damage) increased. Damage-dependent equivalent stiffness parameters (ESPs) were calculated from the real and imaginary signatures of each PZT at different damage states. Satisfactory agreement between equivalent and experimental ESP values was achieved. Also, the relationship between the change of the ESP and the residual strength was obtained. The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.

Assessing muscle strength of persons with transfemoral amputation with and without a prosthesis: A cross-sectional study.

There is a gap in the research about the influence of wearing or not wearing a prosthesis for muscle strength assessment in transfemoral amputees (TFA) and how it is associated with functional mobility. The aim of this study was to compare the muscle isometric strength of the residual limb with and without the prosthesis in people with TFA and to analyze associations between muscle strength and functional mobility. Cross-sectional study. 20 subjects with TFA were included. A handheld dynamometer was used for the assessment of residual limb muscle strength. Functional mobility was assessed with the Timed Up and Go test. The Wilcoxon rank sum test with the rank biserial correlation effect size were used. There were statistically significant differences when testing isometric strength of the residual limb with and without the prosthesis (flexion [ p = 0.007], extension [ p < 0.001], and abduction [ p = 0.003]). There was association between functional mobility and flexion and abduction strength with the prosthesis ( p = 0.005, p = 0.01). Measurements of muscle strength of the residual limb were different when assessed with and without the prosthesis. Isometric strength of the residual limb in abduction and flexion using the prosthesis were correlated with functional mobility.

Random corrosion characteristics of high strength steel wire after 18 years of service and the numerical reconstruction method

This work aims at studying the random corrosion characteristics and residual strength of high strength steel wire after 18 years of service. Salt-spray accelerated corrosion test was carried out on the aged specimen, the mass loss characteristic was determined, the corrosion morphology of steel wire was obtained and reconstructed by 3D optical scanning and the corrosion characteristics were quantified by statistical analysis. Comparing with the corrosion behavior of the steel wire without service, it indicated that the corrosion of aged steel wire is much severe, and the damaged zinc coating and the accumulated fatigue damage should be responsible for it. The ultimate breaking strength of the corroded steel wire was then determined by tensile test, and the fracture morphology was characterized by SEM. A numerical reconstruction method of random corroded wire was proposed, which can be used for the residual strength assessment of aged corroded wire, and systematic parametric studies was also carried out.

Residual ultimate strength assessment of submarine pressure hull under dynamic ship collision

This study aims to develop numerical simulations and empirical equations to predict the ultimate residual strength of dented submarine pressure hulls. The collision scenarios considered in this study include accidents between submarine pressure hulls and attendant vessels or floating objects. First, numerical approaches were developed for dynamic collision and collapse simulations. The accuracy of the developed numerical method was validated by comparing its results with existing test results. Then, the parametric studies were conducted with a series of numerical simulations on the actual submarine pressure hull dimensions with various collision loading scenarios using ABAQUS v6.14 tools. Finally, empirical equations were established using the results from Nonlinear Finite Element Analysis (NFEA) database. The reliability of the derived equations was assessed by comparing their results with the NFEA results and the available test data. These equations are simple to use for the initial design and serviceability limit state of submarine pressure hulls subjected to collision accidents in real cases.

Ultimate torsional strength assessment of large deck opening stiffened box girder subjected to pitting corrosion

The objective of current paper is to provide an approach for the residual ultimate strength assessment of a large deck opening stiffened box girder with pitting corrosion. Finite element method was used to analysis the bearing capacity of the pitted girder subjected to torsional moment. Nonlinearity of both material and geometry as well initial imperfection were taken into account in the research. A comparing investigation was firstly performed to examine the influences of pitting corrosion and uniform corrosion on the ultimate strength. It was found that the pitting is more detrimental for the same corrosion volume loss. Afterwards, effects of some studied variables including the depth, diameter, density, volume and position related to the pit located on both global and local areas of panel plate were discussed based on a series of numerical computations. According to the presented FE results, the corroded volume loss induced by the pit is an influential parameter leading to approximately linear decrease of the ultimate strength for different distributions. Another valuable finding is that the pit on the side shell which nears the 1/2 bay significantly influences the response characteristics of failure mode and strength. Considering regular/random and global/local distributions, four mathematical formulations were proposed for evaluating the residual strength of large deck opening stiffened pitted box girder.

Residual Strength Assessment and Residual Life Prediction of Corroded Pipelines: A Decade Review

Prediction of residual strength and residual life of corrosion pipelines is the key to ensuring pipeline safety. Accurate assessment and prediction make it possible to prevent unnecessary accidents and casualties, and avoid the waste of resources caused by the large-scale replacement of pipelines. However, due to many factors affecting pipeline corrosion, it is difficult to achieve accurate predictions. This paper reviews the research on residual strength and residual life of pipelines in the past decade. Through careful reading, this paper compared several traditional evaluation methods horizontally, extracted 71 intelligent models, discussed the publishing time, the evaluation accuracy of traditional models, and the prediction accuracy of intelligent models, input variables, and output value. This paper’s main contributions and findings are as follows: (1) Comparing several traditional evaluation methods, PCORRC and DNV-RP-F101 perform well in evaluating low-strength pipelines, and DNV-RP-F101 has a better performance in evaluating medium–high strength pipelines. (2) In intelligent models, the most frequently used error indicators are mean square error, goodness of fit, mean absolute percentage error, root mean square error, and mean absolute error. Among them, mean absolute percentage error was in the range of 0.0123–0.1499. Goodness of fit was in the range of 0.619–0.999. (3) The size of the data set of different models and the data division ratio was counted. The proportion of the test data set was between 0.015 and 0.4. (4) The input variables and output value of predictions were summarized.

Experimental tests for the assessment of residual strength of r.c. structures after fire – Case study

A fire in a ham factory in San Daniele del Friuli caused serious damage to the prefabricated reinforced concrete (r.c.) roof panels and smaller damages to beams, columns and walls. In this paper the data captured during preliminary inspection of the building structure are described. To determine the residual strength of steel reinforcements and concrete of r.c. structural elements, a test program with laboratory and in situ tests is presented. The program includes test methods that are able to catch the variability of concrete degradation with distance from the heated surface. Test results are presented and their acceptability in relation to Italian Code is discussed. It is found that the amount of transversal and longitudinal reinforcements strongly influences the deterioration of the concrete due to fire and, consequently, the strength of structural elements. On the basis of tests results, a discussion on the advantages and limitations of the adopted test methods useful for the designers is performed. To restore the load-bearing capacity of the structure, repairs of columns and beams in the first three bays of the central frame are proposed together with the substitution of the roof over the receiving area.

Automated Condition Monitoring with Remaining Lifetime Assessment for Wire Ropes in Ladle Cranes

The hazards and deterioration of operating wire ropes on overhead cranes, which articulate the ladle in the basic oxygen steelmaking process and are subjected to intensive periodic loads and exposure to high temperatures, are discussed. An automated condition monitoring system (ACMS) based on a magnetic flux leakage testing (MFL) flaw detector permanently installed on the rope under test is used. An algorithm of the rope’s residual tensile strength assessment is provided. A specially developed software that submits a decision on the rope’s condition to the crane operator is described. The practice of combining magnetic rope testing (MRT) and tensile strength analysis for the quantitative assessment of rope condition is reviewed. Practical issues are also discussed, such as how to establish the condition monitoring process, set loss thresholds for rope metallic cross-sectional area, and safely prolong the service life of rope.

A Review of Finite Element Analysis and Artificial Neural Networks as Failure Pressure Prediction Tools for Corroded Pipelines.

This paper discusses the capabilities of artificial neural networks (ANNs) when integrated with the finite element method (FEM) and utilized as prediction tools to predict the failure pressure of corroded pipelines. The use of conventional residual strength assessment methods has proven to produce predictions that are conservative, and this, in turn, costs companies by leading to premature maintenance and replacement. ANNs and FEM have proven to be strong failure pressure prediction tools, and they are being utilized to replace the time-consuming methods and conventional codes. FEM is widely used to evaluate the structural integrity of corroded pipelines, and the integration of ANNs into this process greatly reduces the time taken to obtain accurate results.

Probabilistic residual ultimate strength assessment of cracked unstiffened and stiffened plates under uniaxial compression

This paper proposes a reliable approach to evaluate the probabilistic residual ultimate strength of cracked unstiffened/stiffened plates by coupling nonlinear finite element analysis and Kriging-based reliability method. A numerical simulation scheme is established to evaluate the residual ultimate strength of cracked plates under uniaxial compression loading, considering the influence of uncertain initial imperfections, cracking damages and material parameters. To improve the efficiency of assessment, Kriging-based Monte Carlo simulation method combined with an active learning (AK-MCS) strategy is adopted to achieve the reliability analysis of ultimate strength. Firstly, a deterministic analysis is implemented to explore the influence of basic variables on the ultimate strength reduction characteristics of cracked plates. Then, probabilistic reliability analysis is performed to investigate the evolution of failure probability and reliability index of each uncertain parameter and to evaluate reliability index of design objective for ultimate strength. Sensitivity analysis of uncertain parameters on the reliability index and failure probability is studied, and the result reveals that its variation tendency is consistent with deterministic analysis. The reliability index is achieved by AK-MCS with a few of FEM calls, indicating the proposed probabilistic ultimate strength assessment method is accurate and efficient for structural reliability analysis of cracked plates.

Ultimate strength of ship hull girder with grounding damage

ABSTRACT The paper presents a method for the assessment of residual strength of a ship hull damaged in a grounding accident. The strength assessment is based on a coupled beam (CB) method that allows time-efficient analysis. As a case study the method is applied to a double hull tanker. Three grounding damages are defined based on IACS guidelines and with a dedicated grounding assessment tool. The CB method is based on an assumption that global bending response of a ship can be estimated with the help of beams coupled to each other by distributed springs. To include the damage opening in the residual strength assessment, the structural elements in the damaged region are excluded by reducing their elastic modulus. For the validation of the CB method, the residual strength is also evaluated with non-linear finite element method. Good correlation between the methods is reported.

Residual strength assessment of wind turbine rotor blade composites under combined effects of natural aging and fatigue loads

In this paper, the combined effects of natural aging and fatigue loads are considered to assess the residual strength of wind turbine rotor blade composites under actual service environments. Firstly, a comprehensive environmental factor (CEF) methodology is adopted to quantify the combined effects of environmental factors on residual strength. Meanwhile, the artificial accelerated aging test data are used to determine the weight coefficients of the CEF. Subsequently, a two-variable function is presented to characterize the relationship among residual strength, aging time and the CEF. The natural aging test data are utilized to estimate the unknown parameters of the two-variable function. Finally, the combined effects of natural aging and fatigue loads are considered, and a residual strength model is proposed to analyze the strength degradation behaviors of the wind turbine rotor blade composites. The results indicate that fatigue loads have negative effect on the residual strength, while natural aging has both positive and negative effects on the residual strength.

Ultrasonic Assessment of the Concrete Residual Strength after a Real Fire Exposure

After a fire, the assessment of concrete residual strength can be a challenge. Since the strength reduction depends on the distance from the heated surface examination based on destructive test, i.e., core samples, is not precise enough. Therefore, more detailed methods can establish the influence of the high temperature in the zone, which no longer has visible cracks. That method can be used to assess layer thickness to remove due to the fire damage. The Ultrasound Pulse Velocity (UPV) method with point heads was used in the paper to examine samples taken from a structure after the real fire. Moreover, to make the analysis more precise, an effect associated with the porosity in concrete was also considered to separate pure fire effect.