The Restoration of the Nymphaeum of Trajanus in Miletus between Formal Renovation and Structural Repair

The paper reviews the recent applications of piezoelectric materials in structural health monitoring and repair conducted by the authors. First, commonly used piezoelectric materials in structural health monitoring and structure repair are introduced. The analysis of plain piezoelectric sensors and actuators and interdigital transducer and their applications in beam, plate and pipe structures for damage detection are reviewed in detail. Second, an overview is presented on the recent advances in the applications of piezoelectric materials in structural repair. In addition, the basic principle and the current development of the technique are examined.

Innovative Solutions for the Construction and the Repair of Hydraulic Structures

Repair and reconstruction is an integral part of the life cycle of such structures as: bridges, overpasses, aqueducts. Timely maintenance and repair of bridge structures contributes to the continuous improvement of their technical level, as well as to the operational state with increasing load and intensity over time on constantly under construction highways.
 This article presents the results of a study of the need to repair structures over time. The article contains a description of the types of work, as well as the terms when these works need to be performed, graphs of the volume and cost of work are given. As materials and initial data, the data of approximate turnaround periods of elements of bridge structures were taken, as well as a table of the frequency of repairs by year was compiled.
 Based on the collected data, graphs of the cost and changes in the volume of work were built over time. In addition, graphs of the cost of repairing individual elements of the structure are given in relation to the total cost of the structure.
 Based on the results obtained, recommendations are formulated for planning the repair of expatriated bridge structures by bridge maintenance departments. A set of measures is also proposed to eliminate existing violations and further operation of the bridge structure. A set of works for the repair of individual units and structures is recommended. Arguments are given for the need to share responsibilities between bridge operation departments during the repair of the structure.

In the past the chemical industry developed and offered products and techniques based on the material properties and provided the market in this way with recipies for maintenance and repair of concrete structures. The very complex deterioration mechanisms of concrete and steel in concrete have not sufficiently been taken into account. This situation in the past could be called the trial and error period. The main technical advance in the field in the past 10 years is the fact, that the civil engineering society learned and accepted that maintenance and repair is a real engineering task needing a profound knowledge based design and execution. This starts with the clear understanding of the mechanisms leading to deterioration, followed by strategies, concepts and procedures for maintenance and repair based upon the mechanisms and ends with assessment and monitoring procedures and techniques again based upon the mechanisms. That means that we nowadays solve the problem on a sound technical basis, design the maintenance and repair work and on that basis define the needed material properties for every specific maintenance or repair case. In this way the best technical and economical solution can be found. This recent change of the situation is documented in the RILEM Recommendation 124 SRC "Strategies for Repair of Concrete Structures Damaged by Steel Corrosion" and in the series of drafts of CEN-standards on protection and repair of concrete structures.

Renewable energy sources such as wind energy—together with energy-efficient technologies—are essential to meet global energy demands and address climate change. Fiber-reinforced polymer composites, with their superior structural properties (e.g., high stiffness-to-weight) that allow lightweight and robust designs, play a significant part in the design and manufacture of modern wind turbines, especially turbine blades, for demanding service conditions. However, with the current global growth in onshore/offshore wind farm installations (with total global capacity of ∼282 GW by the end of 2012) and trend in wind turbine design (∼7–8 MW turbine capacity with ∼70–80 m blade length for offshore installations), one of the challenges that the wind energy industry faces with composite turbine blades is the aspect of structural maintenance and repair. Although wind turbines are typically designed for a service life of about 20 years, robust structural maintenance and repair procedures are essential to ensure the structural integrity of wind turbines and prevent catastrophic failures. Wind blades are damaged due to demanding mechanical loads (e.g., static and fatigue), environmental conditions (e.g., temperature and humidity) and also manufacturing defects. If material damage is not extensive, structural repair is the only viable option to restore strength since replacing the entire blade is not cost-effective, especially for larger blades. Composite repairs (e.g., external and scarf patches) can be used to restore damaged laminate/sandwich regions in wind blades. With composite materials in the spar (∼30–80 mm thick glass/carbon fiber laminates) and aerodynamic shells (sandwich sections with thin glass fiber skins and thick foam/wood as core), it is important to have reliable and cost-effective structural repair procedures to restore damaged wind blades. However, compared to aerospace bonded repairs, structural repair procedures in wind blades are not as well developed and thus face several challenges. In this regard, the area of composite repair in wind blades is broadly reviewed to provide an overview as well as identify associated challenges.

A series of 38 volar wrist lacerations is reviewed with regard to epidemiologic aspects and results. In general, return of tendon function was quite good, and return of nerve function in this series was also satisfying. We attribute the generally good results to immediate repair of all structures, microscopic repair of significant arterial injuries, microscopic grouped fascicular nerve repair, early mobilization (dynamic splinting and intensive occupational therapy), and a generally youthful group of patients. Review of this series has strengthened our opinion that aggressive primary repair of all injured structures is appropriate for these extensive lacerations.

Maintainability is a function of the durability, damage tolerance, and repairability of a structure. This article discusses the configurations of composite structures, such as sandwich, stiffened-skin, and monolithic structures, used in commercial aircraft composites. It describes the considerations for maintainability of the composite structures during the conceptual design phase. Sources of the defects and damage, such as manufacturing defects and in-service defects, are reviewed. The article describes the nondestructive inspection methods that are used in the repair of composite structures to locate damage, characterize the extent of damage, and ensure post-repair quality. It lists suggestions that can be used as design guidelines for adhesive bonding, general composite structure, sandwich structure, material selection, and lightning-strike protection. The article also provides the basic considerations for personnel, facilities, and equipment during maintenance.

For much of its early history, the U.S. Army Corps of Engineers concentrated on the design and construction of new facilities, but now the mission of the corps is shifting from construction to the maintenance of existing facilities. The corps has addressed its changing role by instituting a repair, evaluation, maintenance, and rehabilitation (REMR) program. As a part of this program, a research effort that focuses on the evaluation and repair of the steel sheet pile structures within the corps' civilian projects has been undertaken. The objectives of this work are: (1) To develop an inspection and rating system that uniformly and consistently describes the current condition of steel sheet pile structures; and (2) to develop guidelines for the maintenance and repair of these structures. The first objective is described in this paper. The project team at Iowa State University has conducted several site visits and field investigations. Experts from the Corps of Engineers were asked to rate several walls, and the results were compared to a preliminary version of the rating system. Modifications were made to reflect the expert's opinions more accurately. The inspection and rating system given here is now ready for wider distribution and additional feedback.

The aerospace industry relies heavily on the structural integrity and performance of aircraft to ensure safe and efficient operations. Over time, aircraft structures can experience wear, corrosion or damage due to various factors such as environmental conditions, fatigue or accidents. Structural repairs are necessary to maintain the airworthiness of aircraft and extend their operational life. These brief highlights the importance of coating solutions in structural repair for aerospace. Coatings play an important role in protecting aircraft structures from degradation, preventing further damage and restoring their mechanical properties. In addition, coatings can improve aerodynamic performance, improve fuel efficiency and reduce maintenance costs. The brief discusses the various types of coating solutions used in aeronautical structural repair. These include corrosion-resistant coatings, abrasion-resistant coatings, heat-resistant coatings, and composite bonding systems. Each type of coating serves a specific purpose in mitigating structural damage and restoring the structural integrity of aircraft components. Also, the brief explores the key properties and characteristics of effective coating solutions. These properties include adhesive strength, flexibility, durability, weight considerations, chemical resistance, and thermal stability. Understanding these properties is critical to selecting the appropriate coating solution for specific repair applications. Also summarizes the challenges and considerations associated with coating applications in aerospace structural repair. These challenges include surface preparation, application techniques, curing processes, compatibility with existing coatings and compliance with regulatory requirements. Overcoming these challenges is essential to ensure the successful implementation of coating solutions in structural repair operations. Finally, the abstract discusses emerging trends and developments in aeronautical structural repair coating technologies. These include eco-friendly coatings, self-healing coatings, nano-coatings and smart coatings with sensing capabilities. These developments hold promise for improving the effectiveness and efficiency of structural repair processes in the aerospace industry.

BackgroundCartilage damage and inflammation are clear characteristics of joint degeneration in OA. In human and animal in vivo and in vitro experimental models, the immunoregulatory cytokines IL-4 and IL-10, both...

Structural repair is a vital step in the direct recycling of spent LiNixCoyMnzO2 lithium‐ion batteries, yet its underlying mechanisms remain insufficiently clear. Herein, the thermal solid‐state structural repair of spent LiNi0.6Co0.2Mn0.2O2 (NCM622) layered cathode material is systematically investigated. Through multiscale techniques combining XRD, XAS, and 6Li solid‐state NMR, we identify the structural degradation in spent NCM622 and monitor both long‐ and short‐range structural evolution during repair. Our findings reveal that degradation predominantly occurs through Ni migration into Li octahedral sites, while Co and Mn demonstrate relatively lower occupancies in the Li layer. Such occupancies are primarily responsible for structural disorder and cubic‐symmetry domain formation within the spent material. The repair process is demonstrated to involve re‐lithiation, oxygen capture, increased transition metal (TM) oxidation states, and the migration of TM ions from the Li layer back to the TM layer, followed by cation diffusion. Both temperature and lithium compensation ratio are identified as critical factors promoting these processes. Capacity recovery studies show a strong correlation between reduced TM occupancy in the Li layer and improved electrochemical performances. These insights allow us to move beyond conventional phase‐transition perspectives, offering an atomic‐level understanding of structural degradation and repair mechanisms in spent layered cathode materials.

Structural repair is a vital step in the direct recycling of spent LiNixCoyMnzO2 lithium-ion batteries, yet its underlying mechanisms remain insufficiently clear. Herein, the thermal solid-state structural repair of spent LiNi0.6Co0.2Mn0.2O2 (NCM622) layered cathode material is systematically investigated. Through multiscale techniques combining XRD, XAS, and 6Li solid-state NMR, we identify the structural degradation in spent NCM622 and monitor both long- and short-range structural evolution during repair. Our findings reveal that degradation predominantly occurs through Ni migration into Li octahedral sites, while Co and Mn demonstrate relatively lower occupancies in the Li layer. Such occupancies are primarily responsible for structural disorder and cubic-symmetry domain formation within the spent material. The repair process is demonstrated to involve re-lithiation, oxygen capture, increased transition metal (TM) oxidation states, and the migration of TM ions from the Li layer back to the TM layer, followed by cation diffusion. Both temperature and lithium compensation ratio are identified as critical factors promoting these processes. Capacity recovery studies show a strong correlation between reduced TM occupancy in the Li layer and improved electrochemical performances. These insights allow us to move beyond conventional phase-transition perspectives, offering an atomic-level understanding of structural degradation and repair mechanisms in spent layered cathode materials.

The most important aspect of structural unibody repair is the correct application of Gas Metal Arc Welding, or G.M.A.W (formerly called Metallic Inert Gas, M.I.G) welding. It is the intent of the SAE Recommended Practice to inform the body repairman on how to evaluate his welds and check if the welder is properly adjusted. By doing this, he can improve the quality of his structural repairs and develop consistent welds.

ConspectusStructural metal components play a vital role in a broad range of industries, from aerospace and automotive to infrastructure and defense. In service, these components can experience substantial wear, thermal fatigue, erosion, corrosion, or chemical reactions, resulting in significant surface or even volumetric damages. Replacement of these components is often energy-intensive and economically impractical. Structural repair, which aims to restore the original geometry while enabling good mechanical performance postrepair, can offset the costs dramatically. Depending on the additive capabilities and bonding mechanisms, structural repair technologies can be divided into four categories: nonadditive, nonmelting-based; nonadditive, melting-based; additive, nonmelting-based; additive, melting-based. Although melting-based approaches can be applied to various repair geometries with good precision, the underlying melting and solidification processes inevitably lead to crucial problems impacting the mechanical performance, such as solidification porosity, high residual stresses, dendritic microstructure formation, elemental segregation, hot cracking, and stress corrosion cracking. To fundamentally solve or minimize these problems, one may employ solid-state technologies that leverage ultrasonic vibration, friction stirring, or particle impact to facilitate metallurgical bond formation. For robust geometry restoration, an additive capability needs to be incorporated for continuous material feeding and precise deposition path control. Currently, two solid-state technologies satisfy the requirement, cold spray and additive friction stir deposition.In this Account, we discuss the structural repair enabled by solid-state metal additive manufacturing, focusing on (i) cold spray, which is a relatively established process, and (ii) additive friction stir deposition, which is an emerging process recently triggering significant research efforts—the authors are particularly invested in this process and are pioneering the research on process fundamentals and structural repair applications. In cold spray, a substrate is bombarded with small metal particles at high speed; upon impact, the particles and substrate co-deform, resulting in interfacial bonding and mechanical interlocking. In additive friction stir deposition, frictional heat is created after the rapidly rotating feed-rod contacts the substrate, followed by co-plastic deformation and mixing between the deposited material and substrate surface. This renders a strong interface with complex 3D features. Both cold spray and additive friction stir deposition can be applied to a wide range of repair geometries while preventing hot cracking and high thermal exposure. Although cold spray has better portability and spatial resolution than additive friction stir deposition, we believe that additive friction stir deposition is the top choice for repairing load-bearing components given its unparalleled capabilities of rendering equiaxed microstructures and wrought-like mechanical properties. Regarding niche repair applications, cold spray is particularly suited for field repair of surface damage; our previous work has shown great promise of using additive friction stir deposition for underwater and large component repair. For future research in cold spray, strategies are needed to eliminate porosity and improve the as-repaired mechanical properties, especially when depositing high strength-to-weight ratio materials. For additive friction stir deposition, we hope to improve the spatial resolution and portability, possibly by down-scaling, and to enable robust repair of components made of high-temperature, high-strength materials.

This book serves as a comprehensive resource for professionals, students, and researchers in civil engineering, offering insights into advanced structural maintenance and repair techniques. The content is organized into eight units, covering a wide range of topics related to the preservation and improvement of concrete and steel structures. The book begins with an introduction to the key concepts in structural maintenance and repair, emphasizing the importance of concrete quality, damage assessment, and overall structural deterioration. It highlights the multifaceted nature of maintenance, including inspection, repair methods, and the conservation of heritage structures. Subsequent units delve into various aspects of structural maintenance and repair, including concrete quality assurance, durability, and the impact of design and construction errors. The use of specialized materials such as polymer concrete, sulphur infiltrated concrete, and fibre-reinforced concrete is explored, along with practical techniques for repair and demolition. The book also covers damage assessment, offering guidance on evaluating structural decay and monitoring distress in concrete structures. It provides insights into understanding different types of cracks and methods for measuring and monitoring them. Concrete structure repair techniques are thoroughly examined, including fracture repair, crack routing, stitching, prestressing, drilling, and the use of advanced materials to mitigate corrosion. The book concludes with a focus on steel structures, discussing repair types, preventive measures, and addressing common issues such as defects in welded joints. Additionally, the book addresses seismic retrofitting and the maintenance of heritage structures, highlighting their vulnerability to earthquakes and the importance of preserving historic buildings through retrofitting and restoration. Overall, this book provides a valuable and practical resource for those involved in civil engineering, offering a comprehensive understanding of advanced structural maintenance and repair techniques across various construction materials and methodologies.