Cement used in structural concrete accounts for 60% of all cement. Thus, the amount of CO2 emission by cement in structural concrete in a year is about 5% of the amount emitted by mankind. However, ...the Life Cycle Assessment (LCA) of structural concrete emits CO2 not only at the product stage but also at the use stage after construction. In this paper, carbon neutrality is viewed from an economic point of view. Then a rough indicator is presented to grasp the CO2 emissions of structural concrete. This paper also shows that LCA of structural concrete should consider not only the materials but also the maintenance phase. And low‐carbon technologies currently in use is introduced. Then the need for multi‐cycle structural concrete with a circular economy is presented. Moreover, it is estimated that CO2 emissions due to disasters in the use stage could be enormous. The carbon neutrality of concrete is not a risk but an opportunity for us.
MC2020, with sustainability and performance‐based design at its core, is the model code for future thinking. It is designed so that both new construction and interventions can be completed based on ...this model code, bringing together the world's most advanced technologies. In this paper, the basic stance of fib toward sustainability is firstly described. Then, as the future envisioned by MC2020, examples of low‐carbon concrete structures will be presented. The paper also discusses the form and uses of conceptual design that MC2020 emphasizes and presents examples of new construction and the extension of service life/adaptation/upgrading of existing structures. New technologies for a circular economy will also be proposed. Sustainability has economic, social, and environmental aspects, and the optimization of each will eventually lead to carbon neutrality. It can be said that MC2020 will help us to arrive at solutions to those complex challenges.
Concrete engineers and researchers have been developed durable reinforced concrete technologies for long time. However, we have not reached the goal which gives us a perfect technology against ...deterioration of reinforced concrete. Basically, concrete itself is high durable material. And we recognize this fact when we see Roman concrete structures are still working now. The technologies described in this article are the challenge to derive the solutions against deterioration of reinforced concrete. This research and development have been taking for about 30 years. Then a non‐metallic highway bridge was built in 2020 with the key technologies of aramid fiber tendons, fiber‐reinforced concrete, and butterfly web.
Sustainability design of concrete structures Sakai, Koji; Shibata, Toshio; Kasuga, Akio ...
Structural concrete : journal of the FIB,
December 2016, Letnik:
17, Številka:
6
Journal Article
Recenzirano
Concrete became the most used material on Earth over 200 years following the invention of modern cement. The design concept has undergone a transition from the allowable stress design method, limit ...state design method, and to the performance‐based design method, in response to the evolution of materials, sophistication of experimental facilities, and advancement of computation skills. From the issues on resources and energy depletion, global warming, and resilience etc., it is necessary to create a new design framework taking into consideration the required performance beyond the conventional concept, in order to construct infrastructure and buildings in a more rational way. In other words, one should construct a design system which sets the continued existence of the diverse and rich global environment as its most important criterion of value. In this paper, the authors review the design and technology system developed in the past and discusses it based on the above‐mentioned new viewpoint, while constructing and presenting a new design system for concrete structures, focusing mainly on the concept of sustainability which is regarded as the most important in achieving conservation of the Earth's rich resources as well as sound socioeconomic activities of humankind in the future, and discusses its feasibility.
Hybrid structures have two major objectives. One is to make concrete structures lighter by combining different technologies. And another is to make structural functions clearer by combining different ...materials. This report outlines two examples of these objectives. The example of the first objective to make structure lighter is light‐weight bridges. We have been building many types of hybrid bridges, for example, the corrugated steel web type, the hybrid truss type and the composite girder type. However, when steel members are used, maintenance is required throughout the lifetime of the structure. To solve these issues, a new type of hybrid bridge has recently been developed – the butterfly web bridge. This new structure combines conventional concrete with high‐strength fibre‐reinforced concrete. The web consists of precast panels shaped like a butterfly wing. These members are reinforced using only prestressing steel in the tension area and have a thickness of just 15 cm. The remaining concrete members are cast‐in‐place. As a result, this new type of bridge achieves a weight reduction of 15 to 20 % compared with a conventional concrete box girder construction. The example of the second objective to make structural functions clear is the hybrid stay cable anchorage system in the tower of cable‐stayed and extradosed bridges. Basically, the steel absorbs the tensile forces of the horizontal component of the stay cable and the concrete absorbs the compressive forces of the vertical component. The steel box anchorage system developed during the 2000s has evolved to make its cheaper to construct in the 2010s. We have undertaken many experiments in our laboratory to confirm the structural behaviour of these evolving systems. The evolution of stay cable anchorage systems is outlined in this article.
Optimierte Hybridstrukturen im Brückenbau
Hybride Strukturen haben zwei Hauptziele. Zum einen soll die Betonstruktur durch die Kombination verschiedener Technologien leichter werden, zum anderen sollen die strukturellen Funktionen durch die Kombination verschiedener Materialien deutlicher werden. In diesem Bericht werden diese beiden Hauptziele anhand von Beispielen dargestellt. Das erste Beispiel sind Leichtbau‐Brücken. Es wurden viele Arten von Hybridbrücken gebaut, z. B. den Typ mit gewelltem Stahlsteg, den Hybrid‐Fachwerktyp und den Verbundträgertyp. Wenn jedoch Stahlträger verwendet werden, müssen diese während ihrer Lebensdauer gewartet werden. Um diese Probleme zu lösen, wurde kürzlich eine neue Art der Hybridbrücke entwickelt. Dabei handelt es sich um eine Kombination aus herkömmlichem Beton und hochfestem faserverstärktem Beton in einem neuen Bauwerk. Das Bauwerk ist eine Butterflystegbrücke (butterfly web bridge). Für den Steg werden vorgefertigte Platten in Form eines Schmetterlingsflügels aus neuen Materialien verwendet. Dieses Element wird nur durch Spannstahl im Zugbereich verstärkt und hat eine Dicke von nur 15 cm. Der Beton der übrigen Teile ist Ortbeton. Dadurch kann das Gewicht dieses neuen Brückentyps um 15 bis 20 % im Vergleich zu konventionellen Betonkastenträgern reduziert werden. Das zweite Beispiel ist das hybride Schrägseilverankerungssystem im Turm von Schrägseil‐ und Extradosed‐Brücken. Grundsätzlich wird die horizontale Komponente, d. h. die Zugkraft, der Schrägseile durch Stahl und die vertikale Komponente, d. h. die Druckkraft, durch Beton aufgenommen. Das System der Stahlkastenverankerung wurde in den 2000er‐Jahren weiterentwickelt, um seine Kosten in den 2010er‐Jahren zu senken. Um das strukturelle Verhalten dieser weiterentwickelten Systeme zu bestätigen, wurden zahlreiche Versuche in unserem Labor durchgeführt. Die Entwicklung des Schrägseilverankerungssystems wird hier dargestellt.
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