Damage Assessment of Reinforced Concrete Structures: A Review

Damage may be assessed using several damage indices with values associated with different structural damage states. The usefulness of a variety of current response-based damage indices in seismic damage assessment is addressed and critically assessed. A novel rational damage assessment method is provided, which measures the structure’s physical reaction characteristics. A practical method based on various analyses is given to evaluate the damaged structures in earthquakes of different intensities. This paper provides an overview of previous research works on the damage assessment of the reinforced concrete structures. This study may be helpful for easy understanding about the damage assessment of reinforced concrete structures and reduce the impacts of disaster and surrounding structures.

Damage Assessment of Reinforced Concrete Structures: A Review

Damage may be assessed using several damage indices with values associated with different structural damage states. The usefulness of a variety of current response-based damage indices in seismic damage assessment is addressed and critically assessed. A novel rational damage assessment method is provided, which measures the structure’s physical reaction characteristics. A practical method based on various analyses is given to evaluate the damaged structures in earthquakes of different intensities. This paper provides an overview of previous research works on the damage assessment of the reinforced concrete structures. This study may be helpful for easy understanding about the damage assessment of reinforced concrete structures and reduce the impacts of disaster and surrounding structures.

The short-term effect of vitamin D supplementation on the response to muscle and liver damages indices by exhaustive aerobic exercise in untrained men: a quasi-experimental study

Background Exercise-induced muscle damage typically caused by unaccustomed exercise results in pain, soreness, inflammation, and muscle and liver damages. Antioxidant supplementation might be a useful approach to reduce myocytes and hepatocytes damages. Therefore, the present study was conducted to investigate the effect of short-term vitamin D (Vit D) supplementation on the response to muscle and liver damages indices by Exhaustive Aerobic Exercise (EAE) in untrained men. Methods In this clinical trial, 24 untrained men were randomly divided into experimental (Exp; n = 12) and control (C; n = 12) groups. Exp received 2000 IU of Vit D daily for six weeks (42 days), while C daily received a lactose placebo with the same color, shape, and warmth percentage. Two bouts of EAE were performed on a treadmill before and after six weeks of supplementation. Anthropometric characteristics (Bodyweight (BW), height, Body Fat Percentage (BFP), Body Mass Index (BMI), waist to hip ratio (WHR)) were measured at the Pre 1 and Pre 2. Blood samples were taken to measure the Creatine Kinase (CK), Lactate Dehydrogenase (LDH), Aspartate Aminotransferase (AST), Alanine Aminotransferase (ALT), Gamma-Glutamyl Transferase (GGT), Alkaline Phosphatase (ALP), and Vit D levels at four stages: Pre 1 (before the first EE session), Post 1 (after the first EE session), Pre 2 (before the second EE session), and Post 2 (after the second EE session). The data were analyzed using repeated-measures ANOVA, Bonferroni's post hoc test, independent t test, and dependent t-test at the significant level of P < 0.05 using SPSS version 26. Results The results show significant differences between Exp and C in alterations of BW (P = 0.039), BMI (P = 0.025), BFP (P = 0.043), and WHR (P = 0.035). The results showed that EAE increased muscle and liver damage indices and Vit D (P < 0.05). Compared with C, the results of the independent t-test showed significantly lower ALT (P = 0.001; P = 0.001), AST (P = 0.011; P = 0.001), GGT (P = 0.018; P = 0.001), and ALP (P = 0.001; P = 0.001); while significantly higher Vit D (P = 0.001, P = 0.001) in the Exp in both Pre 2 and Post 2; receptivity. The independent t test showed significantly lower ALT (P = 0.001; P = 0.001), AST (P = 0.011; P = 0.001), GGT (P = 0.018; P = 0.001), and ALP (P = 0.001; P = 0.001) and considerably greater Vit D (P = 0.001, P = 0.001) in the Exp in both Pre 2 and Post 2 compared to C. The results of an independent t test showed that LDH and CK levels in the Exp were significantly lower than those in the Post 2 (P = 0.001). Conclusions Short-term Vit D supplementation could prevent myocytes and hepatocytes damage induced by EAE.

Retrofitting of Confined Brick Masonry with FRP

Brick masonry structures are commonly used in world because of its simplicity and economy. However, it is susceptible to failure in earthquakes because of the bricks weak interlocking bonds and brick masonry structures designed mainly against gravity load demand. Therefore, in recent years research work has been conducted to confine the unreinforced brick masonry with reinforced concrete tie beams and column, to improve its seismic performance. This enhances both the lateral resistance and stability of the entire structure, to perform as one mass unit against the lateral forces. However, the effect of confining brick masonry through reinforced concrete member has been evaluated in the past only on testing single cantilever walls or single room. Therefore, this research work aims to evaluate its influence on large structures i.e., highlight its limitation and afterward mitigate the damages by introducing external FRP strengthening techniques. The structures configuration is based on the observation made in Pakistan’s rural areas where mostly brick masonry structure. Confined brick masonry walls are subjected to quasi static lateral loading, afterwards retrofitted with FRP and tested again. The test result discussion includes load response behavior, stiffness degradation, energy dissipation and damage indices. Keywords: Confined brick masonry, RC tie beam column, FRP, Retrofitting, Seismic analysis, Quasi Static

Interpretable Machine Learning in Damage Detection Using Shapley Additive Explanations

In recent years, Machine Learning (ML) techniques have gained popularity in Structural Health Monitoring (SHM). These have been particularly used for damage detection in a wide range of engineering applications such as wind turbine blades. The outcomes of previous research studies in this area have demonstrated the capabilities of ML for robust damage detection. However, the primary challenge facing ML in SHM is the lack of interpretability of the prediction models hindering the broader implementation of these techniques. For this purpose, this study integrates the novel Shapley Additive exPlanations (SHAP) method into a ML-based damage detection process as a tool for introducing interpretability and, thus, build evidence for reliable decision-making in SHM applications. The SHAP method is based on coalitional game theory and adds global and local interpretability to ML-based models by computing the marginal contribution of each feature. The contribution is used to understand the nature of damage indices (DIs). The applicability of the SHAP method is first demonstrated on a simple lumped mass-spring-damper system with simulated temperature variabilities. Later, the SHAP method has been evaluated on data from an in-operation V27 wind turbine with artificially introduced damage in one of its blades. The results show the relationship between the environmental and operational variabilities (EOVs) and their direct influence on the damage indices. This ultimately helps to understand the difference between false positives caused by EOVs and true positives resulting from damage in the structure.

Numerical Simulation of Single-Point Mount PZT-Interface for Admittance-Based Anchor Force Monitoring

This study investigates the dynamic characteristics of a smart PZT interface mounted on a prestressed anchorage to verify the numerical feasibility of the admittance-based anchor force monitoring technique. Firstly, the admittance-based anchor force monitoring technique through a single-mount PZT interface is outlined. The admittance response of the PZT interface-anchorage system is theoretically derived to show the proof-of-concept of the technique for anchor force monitoring. Secondly, a finite element model corresponding to a well-established experimental model in the literature is constructed. The effect of anchor force is equivalently treated by the contact stiffness and damping parameters at the bottom surface of the anchorage. Thirdly, the admittance and the impedance responses are numerically analyzed and compared with the experimental data to evaluate the accuracy of the numerical modelling technique. Fourthly, the local dynamics of the PZT interface are analyzed by modal analysis to determine vibration modes that are sensitive to the change in the contact stiffness (i.e., representing the anchor force). Finally, the admittance responses corresponding to the sensitive vibration modes are numerically analyzed under the change in the contact stiffness. The frequency shift and the admittance change are quantified by statistical damage indices to verify the numerical feasibility of the anchor force monitoring technique via the smart PZT interface. The study is expected to provide a reference numerical model for the design of the single-point mount PZT interface.

Piezo impedance-based monitoring of loosening of bolts: Experimental and numerical study

The suspension strut mount plays a crucial role in any vehicular suspension system, where it acts as a connector (bolted) to the vehicular body and suspension strut. The mount’s purpose is to cushion the Vehicular impacts and reduce the jarring effect, noise, and vibration caused due to vehicle movement over the undulated roads. The self-loosening of bolts results because of the up and down impact of the spring cause the jounce bouncer to push and pull action at the mount interface, cause vibrations transmitted to the vehicle camber. Self-loosening leads to damage of mount followed by clunking noises, noisy steering, tire misalignment, and can cause discomfort to the passenger. Therefore, condition monitoring and assessment of an upper strut mount is necessary for vehicles. This paper studies the feasibility of the piezo Impedance-based Structural health monitoring (SHM) technique to monitor the self-loosening bolts in the upper strut mount of the suspension system (MacPherson strut suspension) of passenger car. The piezo coupled signatures were obtained experimentally by loosening all the three bolts (connected to strut bearing) through control torques through a digital torque wrench. All the experimental signatures were acquired with a single PZT patch bonded to the surface of the upper strut mount for loosening bolts with pre-tight loss. Progressive damage scenarios are simulated along with preload loss of either single bolt or all three bolts, respectively. Three different statistical damage indices were evaluated for damage quantification raised due to bolt loosening. A 3D numerical modeling of strut mount is done using ANSYS WORKBENCH, and piezo impedance signatures were acquired (hence converted to admittance) for validating the experimental signatures. In an overall, this study provides an insight into the loss of structural integrity due to the self-loosening of suspension bolts, which can be threatful to vehicular integrity.

Decay Assessment of Stone-Built Cultural Heritage: The Case Study of the Cosenza Cathedral Façade (South Calabria, Italy)

This study aims to assess the different decay phenomena affecting the Cosenza Cathedral façade (Calabria, South Italy) through the evaluation of the relative damage indices. For this goal, a multidisciplinary approach was applied exploiting both nondestructive and microdestructive techniques. Such a combination enabled proposing an intervention priority scale that can be helpful to institutions when planning a prompt restoration intervention. The results suggest the efficiency of this approach to obtain a multidisciplinary diagnostic and conservation system for the management and valorization of the Cultural Heritage also in terms of monitoring, maintenance, and selection of the most suitable restoration procedures over time.

Performance-Based Optimization of Reinforced Ductile Concrete Frames with Asymmetric Reinforcement in Columns Using the ISR Analogy

Aims/ Objectives: The present work exposes the design of optimization procedures both with the “Particle Swarm Optimization” (PSO) algorithm and the “Genetic Algorithm” (GA) for the design of reinforced concrete frames, making comparisons in cost, weight of the structure and predicted damage. The optimization procedures are built up using the “Idealized Smeared Reinforcement” (ISR) analogy for each element of the structural model frames considered for this work. Study Design: Descriptive Cross-sectional study. Place and Duration of Study: Graduate Engineering Department, Autonomous University of Queretaro, Santiago de Quertaro, Quertaro, Mxico, August 2021. Methodology: Two different numerical structural plane-frame models were created for the application and comparison of the performance of the optimization design procedures hereby proposed. The optimization procedures were mono-objective with a cost-objective function, taking on account steel reinforcement and concrete for the cost computation. Two different design approaches were carried on for this work, one proposing asymmetrical reinforcement for columns and the other with symmetrical reinforcement. In order to compute the damage indices considered for this study a non-linear Pushover structural analysis is performed. Results: Results show that asymmetrical reinforcement in columns may reduce concrete volumes, although such reduction in material might not be quite proportional with construction cost, given that asymmetric reinforcement in columns is more expensive than symmetrical, per unit-cost. The bigger the structure, the more likely is to obtain lighter structures by using asymmetrical reinforcement. Regarding damage of the structure, results show that when using asymmetrical reinforcement in columns, it is more likely to obtain smaller values for the expected damage with no great difference on the estimated collapse Safety Factors for the seismic loads. In general, the proposed methodology hereby proposed enhances quite good optima results, requiring only a few adjustments of clash-free and slap reinforcement after the optimization procedure terminates. Conclusion: When designing reinforced concrete frames with asymmetric reinforcement in columns, an increase in construction costs of as much as 25% as that obtained for symmetric reinforcement could be enhanced. In general, with the proposed methodology to optimally design reinforced concrete frames, savings of as much as 20% in construction costs from an initial structural proposal can be reached.

Seismic performance assessment of RC columns with interlocking hoops

The aim of this study is to analytically assess the seismic performance of reinforced concrete (RC) columns with interlocking hoops using a novel damage index, and to provide data for developing next generation seismic design criteria. Seismic performance of RC columns is controlled by the level of confinement provided by transverse steel. Interlocking hoops are commonly used in RC columns because they can provide more effective confinement than rectangular hoops. Three RC interlocking columns were tested under a constant axial load and a cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze RC structures. Novel damage indices aim to provide a means of quantifying numerically the performance level in RC columns with interlocking hoops sustained under earthquake loading. The proposed numerical method for the seismic performance assessment of interlocking columns is verified by comparison with the experimental results.