Download or read book ACI fib International Symposium on Punching Shear of Structural Concrete Slabs 2016 written by Carlos Emilio Ospina and published by . This book was released on 2017 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Punching shear of structural concrete slabs written by FIB - Féd. Int. du Béton and published by FIB - Féd. Int. du Béton. This book was released on 2017 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: fib Bulletin 81 reports the latest information available to researchers and practitioners on the analysis, design and experimental evidence of punching shear of structural concrete slabs. It follows previous efforts by the International Federation for Structural Concrete (fib) and its predecessor the Euro-International Committee for Concrete (CEB), through CEB Bulletin 168, Punching Shear in Reinforced Concrete (1985) and fibBulletin 12, Punching of structural concrete slabs (2001), and an international symposium sponsored by the punching shear subcommittee of ACI Committee 445 (Shear and Torsion) and held in Kansas City, Mo., USA, in 2005. This bulletin contains 18 papers that were presented in three sessions as part of an international symposium held in Philadelphia, Pa., USA, on October 25, 2016. The symposium was co-organized by the punching shear sub-committee of ACI 445 and by fib Working Party 2.2.3 (Punching and Shear in Slabs) with the objectives of not only disseminating information on this important design subject but also promoting harmonization among the various design theories and treatment of key aspects of punching shear design. The papers are organized in the same order they were presented in the symposium. The symposium honored Professor Emeritus Neil M. Hawkins (University of Illinois at Urbana-Champaign, USA), whose contributions through the years in the field of punching shear of structural concrete slabs have been paramount. The papers cover key aspects related to punching shear of structural concrete slabs under different loading conditions, the study of size effect on punching capacity of slabs, the effect of slab reinforcement ratio on the response and failure mode of slabs, without and with shear reinforcement, and its implications for the design and formulation in codes of practice, an examination of different analytical tools to predict the punching shear response of slabs, the study of the post-punching response of concrete slabs, the evaluation of design provisions in modern codes based on recent experimental evidence and new punching shear theories, and an overview of the combined efforts undertaken jointly by ACI 445 and fib WP 2.2.3 to generate test result databanks for the evaluation and calibration of punching shear design recommendations in North American and international codes of practice.
Download or read book SP 315 ACI fib International Symposium on Punching Shear in Structural Concrete Slabs written by Carlos E. Ospina and published by . This book was released on 2017-07-28 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Shear and Punching Shear in RC and FRC Elements written by fib Fédération internationale du béton and published by fib Fédération internationale du béton. This book was released on 2010-12-01 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: fib Bulletin 57 is a collection of contributions from a workshop on "Recent developments on shear and punching shear in RC and FRC elements", held in Salò, Italy, in October 2010. Shear is one of a few areas of research into fundamentals of the behaviour of concrete structures where contention remains amongst researchers. There is a continuing debate between researchers from a structures perspective and those from a materials or fracture mechanics perspective about the mechanisms that enable the force flow through a concrete member and across cracks. In 2009, a Working Group was formed within fib Task Group 4.2 "Ultimate Limit State Models" to harmonise different ideas about design procedures for shear and punching. An important outcome of this work was the ensuing discussions between experts and practitioners regarding the shear and punching provisions of the draft fib Model Code, which led to the organization of the Salò workshop. Invited experts in the field of shear and FRC gave 18 lectures at the workshop that was attended by 72 participants from 12 countries in 3 different continents. The contributions from this conference as compiled in this bulletin are believed to represent the best of the current state of knowledge. They certainly are of general interest to fib members and especially helpful in the finalization of the 2010 fibModel Code. It is hoped that this publication will stimulate further research in the field, to refine and harmonize the available analytical models and tools for shear and punching design.
Download or read book Fibre Reinforced Concrete written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2022-11-01 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fibre Reinforced Concrete (FRC) is a composite material characterized by an enhanced post-cracking tensile residual strength, due to the capacity of fibres to bridge the crack faces by means of pull-out mechanism. Due to a better knowledge of FRC and the recent developments worldwide of guidelines for structural design, the fib Special Activity Group 5, who prepared the new fib Model Code, decided to introduce some sections on new materials and in particular on FRC structural design. At that time, working Groups TG 8.3 (“Fibre reinforced concrete”) and TG 8.6 (“Ultra high performance fibre reinforced concrete”) of fib prepared these sections of the new fib Model Code concerning FRC design rules for providing a guidance to engineers to properly and safely design FRC structural elements, both at serviceability and at ultimate limit states, based on the state-of-the-art knowledge. This bulletin was written with the aim to share the main framework used by the two groups to introduce these two sections and to describe the many aspects already known, but not yet introduced in the Model Code. Even though the basic principles introduced in the two sections are mainly obtained from research on steel fibre reinforced concrete, the Model Code is open to every type of fibres, following a performance-based design approach. The bulletin represents a wide effort made by the people of the Task Group 4.1 and 4.2 to trace the knowledge on FRC and aims to be helpful for structural designers when using this new material in the practice.
Download or read book Fibre Reinforced Concrete Improvements and Innovations II written by Pedro Serna and published by Springer Nature. This book was released on 2021-09-04 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume highlights the latest advances, innovations, and applications in the field of fibre-reinforced concrete (FRC), as presented by scientists and engineers at the RILEM-fib X International Symposium on Fibre Reinforced Concrete (BEFIB), held in Valencia, Spain, on September 20-22, 2021. It discusses a diverse range of topics concerning FRC: technological aspects, nanotechnologies related with FRC, mechanical properties, long-term properties, analytical and numerical models, structural design, codes and standards, quality control, case studies, Textile-Reinforced Concrete, Geopolymers and UHPFRC. After the symposium postponement in 2020, this new volume concludes the publication of the research works and knowledge of FRC in the frame of BEFIB from 2020 to 2021 with the successful celebration of the hybrid symposium BEFIB 2021. The contributions present traditional and new ideas that will open novel research directions and foster multidisciplinary collaboration between different specialists.
Download or read book Advances on bond in concrete written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2022-12-01 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well the crack development and crack width. At Ultimate Limit State, bond governs anchorage and lap splices behavior as well as structural ductility. When plain (smooth) bars were used, the steel-to-concrete bond was mainly associated with “chemical adhesion/friction” that is related to the surface roughness of the rebar. As steel strengths increased the need to enhance interaction between steel and the surrounding concrete was recognized, and square twisted rebars, indented rebars or, later on, ribbed rebars came into the market, the latter being the type of deformed bar most commonly adopted since the 1960/70s. When ribbed rebars became widely used, several research studies started worldwide for better understanding the interaction between ribs and the surrounding concrete. Researchers evidenced the development of micro-cracks (due to the wedge action of the ribs) towards the external face of the structural element. If confinement is provided by the concrete cover, by transverse reinforcement or by an external transverse pressure, the full-anchorage capacity is guaranteed and a pull-out failure occurs, with crushing of concrete between the ribs. On the contrary, with lesser confining action, a splitting failure of bond occurs; the latter may provoke a brittle failure of the lap splice or, in some cases, of anchorages. However, after many years of research studies on bond-related topics, there are still several open issues. In fact, new materials entered into the market, as concrete with recycled aggregates or fibre reinforced concrete; the latter, having a kind of distributed reinforcement into the matrix (the fibres), provides a better confinement to the wedge action of the ribs. In addition, concrete and steel strength continuously increased over the years, causing changes in the bond behavior due to differences in mechanical properties of materials but also to the different concrete composition at the interface with the steel rebar causing a different bond behavior. Moreover, the lower water/cement ratio of these high-strength concrete makes the bleeding phenomena less evident, changing the concrete porosity in the upper layers of the structural element and thus making the current casting position parameters no-longer reliable. Finally, concrete with recycled aggregates are becoming more important in a market that is looking forward to a circular economy. As such, all the experimental results and database that allowed the calibration of bond rules now present in building codes for conventional concrete, may be not be representative of these new types of materials nowadays adopted in practice. Furthermore, after more than 50 years of service life, structural elements may not satisfy the current safety requirements for several reasons, including material degradation (with particular reference to steel corrosion) or increased loads, by also considering the seismic actions that were non considered by building codes at the time of the original design. The structural assessment of existing structures requires proper conceptual models and new approaches for evaluating the reliability of existing structures by also considering the remaining expected service life. In addition, specific rules for older materials, as plain smooth bars, should be revised for a better assessment of old structures. Last, but not least, interventions in existing structures may require new technologies now available such as post-installed rebars. While many advances have been achieved, there remain areas where a better understanding of bond and its mechanisms are required, and where further work is required to incorporate this understanding into safe and economic rules to guide construction and maintenance of existing infrastructures. These aspects were widely discussed within the technical community, particularly in the fib Task Group 2.5 and in the ACI 408 Committee dealing with bond and anchorage issues. Furthermore, special opportunities for discussing bond developments were represented by the International Conferences on ‘Bond in Concrete’ held each decade since 1982 as well as by joint workshops organized by fib TG2.5 and ACI 408. Within this technical collaboration, this Bulletin was conceived, and, thus, it collects selected papers presented at the joint fib-ACI Convention Session on Bond in Concrete held in Detroit (USA) in 2017. The bulletin is based on four main Sections concerning: - General aspects of bond - Anchorages and laps of bars and prestressing tendons - Bond under severe conditions - Degradation of bond for corrosion - Bond in new types of concrete The main aim of the Bulletin is to shed some new lights on the advances in understanding and application of bond related issues achieved over the last few years, and identify the challenges and priorities to be addressed in the next years. Another important aspect of the bulletin is to provide practical information from research findings.
Download or read book Precast Concrete in Tall Buildings written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2021-12-01 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been continued global growth in tall building construction over recent years. The variation in the use of such buildings is remarkable, from lavish hotels and apartments to socially affordable units. As the world struggles to cope with growing numbers of people, dwindling resources and movements from rural to urban habitats it is unavoidable that population densities will increase, and more efficient use of scarce land will be needed. Taller buildings are the inevitable consequence. Tall buildings can use several different types of material to form their framework and envelope. Those materials are mixed to provide an optimum building solution to suit client requirements such as structure, occupancy, vision, affordability, timing, sustainability and quality. Precast concrete is one of those materials, and has been used from whole frameworks to facades, and elements mixed with structural steelwork and cast in place concrete. This state of the art report shows how precast concrete can be effectively integrated into tall buildings using modern materials and techniques, drawing on the experience and expertise that is currently available in the global precast concrete industry. The report is aimed at not only building professionals and students, but also at contractors, investors, owners, public bodies and any other parties interested in the possibilities for use of precast concrete in tall building construction. Extensive case studies at the end of the Bulletin illustrate the benefits and applications discussed in the earlier chapters.
Download or read book Precast concrete bridge continuity over piers written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2020-07-01 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concrete bridges are an important part of today's road infrastructure. An important part of those concrete bridges is to a large extent prefabricated. Precast concrete enables all the advantages of an industrialized process to be fully utilized. Contemporary concrete mixtures are used to realize high-strength bridge girders and piers that exactly meet the requirements set, both structurally and aesthetically, with a small ecological footprint. Sustainable and durable! On the construction site, there is no need for complex formwork, the execution time is drastically reduced and where road, water and rail traffic on or under the bridge has to be temporarily interrupted, it is only minimally inconvenienced during the execution of the project. There is a wide variety of prefabricated bridges. In 2004, the fib commission on prefabrication already published the Bulletin 29 Precast concrete bridges which, in addition to the history of prefabricated bridges, also gave an overview of the different bridge types and structural systems. This document elaborates on one specific structural system: the continuous bridge. Task Group 6.5 "Precast concrete bridges" discusses in detail how to achieve continuity over the piers with precast elements. This bulletin bundles the experiences of experts in the field of bridge design so that less experienced designers would be able to identify the points of attention and make a correct design. In addition to the theoretical considerations, the principles are tested against three realizations in the USA and Europe. Commission 6 thanks the Co-Conveners Maher Tadros and Hugo Corres and all active members of the Task Group for sharing their knowledge and experience and for the successful realization of this bulletin.
Download or read book Life Cycle Civil Engineering Innovation Theory and Practice written by Airong Chen and published by CRC Press. This book was released on 2021-02-26 with total page 2619 pages. Available in PDF, EPUB and Kindle. Book excerpt: Life-Cycle Civil Engineering: Innovation, Theory and Practice contains the lectures and papers presented at IALCCE2020, the Seventh International Symposium on Life-Cycle Civil Engineering, held in Shanghai, China, October 27-30, 2020. It consists of a book of extended abstracts and a USB card containing the full papers of 230 contributions, including the Fazlur R. Khan lecture, eight keynote lectures, and 221 technical papers from all over the world. All major aspects of life-cycle engineering are addressed, with special emphasis on life-cycle design, assessment, maintenance and management of structures and infrastructure systems under various deterioration mechanisms due to various environmental hazards. It is expected that the proceedings of IALCCE2020 will serve as a valuable reference to anyone interested in life-cycle of civil infrastructure systems, including students, researchers, engineers and practitioners from all areas of engineering and industry.
Download or read book Conceptual Design of Precast Concrete Bridge Superstructures written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2021-08-01 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concrete bridges are an important part of today's road infrastructure. An important part of those concrete bridges is to a large extent prefabricated. Precast concrete enables all the advantages of an industrialized process to be fully utilized. Contemporary concrete mixtures are used to realize high-strength bridge girders and piers that exactly meet the requirements set, both structurally and aesthetically, with a small ecological footprint. Sustainable and durable! On the construction site, there is no need for complex formwork, the execution time is drastically reduced and where road, water and rail traffic on or under the bridge has to be temporarily interrupted, it is only minimally inconvenienced during the execution of the project. Bridges capture the imagination. In addition to their pure functionality, overcoming a height difference, they offer designers unprecedented opportunities to shape their creativity, including when using precast concrete. This bulletin, prepared by the experts of Task Group 6.5 'Precast concrete bridges', takes a closer look at the conceptual (preliminary) design of prefabricated concrete bridges. The bulletin does not have the ambition to define the umbrella term 'conceptual design' but shows in a pragmatic way, using 24 examples spread all over the world, how leading designers use this methodology to select from the many possibilities to arrive at an ideal solution taking into account all design conditions. One often reads that experience is a necessary condition for good conceptual design. The pooled knowledge and experience in this bulletin already provide the reader with a good head start. Commission 6 thanks the former convener of the Task Group Hugo Corres, editor of this document, and the current co-conveners Marcello Waimberg and Ken-ichi Kata as well as all active members of the Task Group for sharing their knowledge and experience and for the successful realization of this bulletin.
Download or read book Insights and Innovations in Structural Engineering Mechanics and Computation written by Alphose Zingoni and published by CRC Press. This book was released on 2016-11-25 with total page 3395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Insights and Innovations in Structural Engineering, Mechanics and Computation comprises 360 papers that were presented at the Sixth International Conference on Structural Engineering, Mechanics and Computation (SEMC 2016, Cape Town, South Africa, 5-7 September 2016). The papers reflect the broad scope of the SEMC conferences, and cover a wide range of engineering structures (buildings, bridges, towers, roofs, foundations, offshore structures, tunnels, dams, vessels, vehicles and machinery) and engineering materials (steel, aluminium, concrete, masonry, timber, glass, polymers, composites, laminates, smart materials). Some contributions present the latest insights and new understanding on (i) the mechanics of structures and systems (dynamics, vibration, seismic response, instability, buckling, soil-structure interaction), and (ii) the mechanics of materials and fluids (elasticity, plasticity, fluid-structure interaction, flow through porous media, biomechanics, fracture, fatigue, bond, creep, shrinkage). Other contributions report on (iii) recent advances in computational modelling and testing (numerical simulations, finite-element modeling, experimental testing), and (iv) developments and innovations in structural engineering (planning, analysis, design, construction, assembly, maintenance, repair and retrofitting of structures). Insights and Innovations in Structural Engineering, Mechanics and Computation is particularly of interest to civil, structural, mechanical, marine and aerospace engineers. Researchers, developers, practitioners and academics in these disciplines will find the content useful. Short versions of the papers, intended to be concise but self-contained summaries of the full papers, are collected in the book, while the full versions of the papers are on the accompanying CD.
Download or read book Guidelines for Submerged Floating Tube Bridges written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2020-10-01 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: This bulletin is a guidelines document for “Submerged Floating Tube Bridges”, that represents an innovation in Marine Concrete Structures. This theme is considered important for Commission 1 since in the future several applications are forecast in marine environments. Submerged Floating Tube Bridges are a solution that can be proposed to solve different problems in passing water constrains as lakes and fiords, reducing the impact and allowing several economic advantages. The guidelines certainly will boost the application of Submerged Floating Tube Bridges since the document is useful not only for designers but also for construction companies, owners and public administrations. As guidelines, the bulletin gives wide information on the design, construction and management of these structures, allowing all the users to be confident in promoting the use of Submerged Floating Tube Bridges.
Download or read book External Tendons for Bridges written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2020-12-01 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: The concept of post-tensioning has been recognized for over a century. Interestingly, early developments started with external tendons, but failed to be recognized as a major construction technique for two main reasons: - Low tensile performance of early steels in combination with a poor knowledge of concrete creep and shrinkage properties, - Lack of a durable corrosion protection. With the technological progress, external tendons became increasingly popular in the 1980’s, as a post-tensioning method enabling inspection and, if necessary, replacement of tendons without demolition of structural members. Towards the end of the last century, more than 50 bridges have been built with external tendons, first in France and soon gaining traction in other countries. FIP published a state-of the-art report in May 1996 to provide a review of the application of external tendons, describing specific material problems and methods for dealing with them. 25 years have passed and, while the engineering principles covered by the FIP report remain unchanged, the context has evolved: - External tendons and construction methods have kept evolving with better materials, ever longer spans, and tighter schedules. - Normalization frame in Europe changed, Severe durability issues have occurred in some countries from which the industry can extract good knowledge of the causes and how to avoid similar problems in the future. This new fib bulletin has been prepared with the aim to reflect the current state of the art and encompass the knowledge amassed in the last quarter of century with chapters covering from the design and approval of systems and materials to installation, quality control and monitoring. The last chapter is a compilation of structures worldwide covering all sorts of materials, typologies and construction methods, which might be a source of inspiration for owners and designers alike.
Download or read book Acceptance of post tensioning systems for cryogenic applications written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2021-04-01 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the Second World War the demand of energy has undergone an exponential growth that has led to a sharp annual increase in the use of natural gas in both, cities and thermal power stations. Nowadays, the strategic relevance of natural gas as a main source of energy is evident with a contribution of more than 20% of the total world consumption. This development in increasing demand of natural gas has led for a need of suitable storage and transportation infrastructure. Various gases, especially hydrocarbons, are preferably stored in liquid form for transportation and storage since the phase transformation from gas to liquid comes with a significant reduction of the volume (e.g. up to 600 times). Gases can be liquefied by raising the pressure or by cooling to their boiling point, which for most gases is below 0°C. This is known as cryogenic storage. The term cryogenic is derived from two Greek words, namely kryos meaning icy-cold and genes which can be translated as shape. These fib recommendations are concerned about post-tensioning systems used in cryogenic tanks and have been formulated on the basis of actual available knowledge with the aim to reflect the current state of the art. Consequently, these recommendations have included a classification of the different cryogenic tanks typologies used in the past and nowadays, the associated different tendon types depending on their exposure to low temperature (e.g. never, only accidentally or during normal tank operation) and the testing regime required for acceptance of the materials and the post-tensioning system according to this document. An international working group comprising more than 20 experts from administrative authorities, universities, laboratories, owners, structural designers, suppliers of prestressing steels and post-tensioning systems suppliers have actively contributed in order to develop these recommendations. This text has been written to cover best construction practices around the world, and to provide material specifications which are considered to be the most advanced available at the time of preparing this text. For ease of use (for Owner, Designer and Post-tensioning System Supplier), the content has been arranged systematically according to the system components into chapters focusing on performance characteristics, requirements and acceptance criteria.
Download or read book Birth Certificate and Through Life Management Documentation written by FIB – International Federation for Structural Concrete and published by FIB - International Federation for Structural Concrete. This book was released on 2020-06-01 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: While it is generally accepted by owners and users that vehicles such as airplanes or cars must be subjected to a pre-defined maintenance plan during their lifetime, this is less obvious in public opinion for engineering structures and buildings. This may be related to the general feeling that “moving objects” should be more sensitive to aging and deterioration than “structures anchored in ground”! This may also relate to the fact that detailed maintenance manuals, which are considered obligatory by insurance companies, are generally for aircraft, boats and cars, but not systematically for civil engineering structures, except for iconic or major projects. The performance-based approach to the durability design and assessment of concrete structures is also becoming increasingly popular in the construction sector. In recent years, numerous studies have been carried out worldwide in order to better assess the expected properties related to the durability of concrete. This has led to the standardization of test protocols, but also to a better understanding of the main parameters impacting the overall durability of concrete. Documentation related to durability indicators will then become increasingly necessary for the accurate implementation of a performance-based approach that enables the promotion of sustainable materials. Durability models have a strong need for relevant in-field data feedback in order to define accurate inputs for modelling both during the design process (gathered from previous projects) and during the follow-up process to allow for re-calibration of inputs and re-assessment of durability expectations by the models if judged necessary. A framework for data collection was therefore considered extremely importance by the fib Commission 8: Durability, and is the objective of this fib Technical report “Birth-certificate and Through-Life Management Documentation”. It is indeed very important to collect relevant data within a comprehensive and standardized format, as now proposed by this fib Bulletin. Thanks to its pre-defined format, compatible with the general fib framework, “Birth-certificate and Through-Life Management Documentation” will definitively be useful to owners for the maintenance plan and intervention strategies of their assets. This operational technical report will also be very useful for designers, as it should encourage the collection of relevant information in databases to be used for future projects where a realistic assessment of expected properties is considered through largely similar concrete mix designs under given exposure conditions. The Commission, which deals with durability aspects, hopes that this Bulletin will provide users a valuable tool and perspective on service life management issues.
Download or read book High Tech Concrete Where Technology and Engineering Meet written by D.A. Hordijk and published by Springer. This book was released on 2017-06-08 with total page 2926 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the proceedings of the fib Symposium “High Tech Concrete: Where Technology and Engineering Meet”, that was held in Maastricht, The Netherlands, in June 2017. This annual symposium was organised by the Dutch Concrete Association and the Belgian Concrete Association. Topics addressed include: materials technology, modelling, testing and design, special loadings, safety, reliability and codes, existing concrete structures, durability and life time, sustainability, innovative building concepts, challenging projects and historic concrete, amongst others. The fib (International Federation for Structural Concrete) is a not-for-profit association committed to advancing the technical, economic, aesthetic and environmental performance of concrete structures worldwide.
