Optimization of Concrete Mixtures for Use in Structural Elements


Book Description

Portland cement is an essential ingredient in concrete. The use of cement is to enhance the strength as well as other hardened properties of concrete mixtures. Determining the accurate amount of cement is important because the required strength may not be achieved if not enough cement is used. By contrast, when using too much cement, concrete cracking may occur that leads to reducing durability. Researchers at the University of Arkansas (UA) have shown that many bridge decks achieve their 28 day design strength of 4000 psi by 7 days of age. Bridge decks having high strength may experience cracking, which affects the durability. The Arkansas State Highway and Transportation Department (AHTD) classifies two types of concrete mixtures that can be used in bridges. The first is Class S concrete, and the second is Class S(AE). Class S is used for the structural components and does not contain air entrainment while Class S (AE) is mainly used for bridge decks and contains air entrainment. AHTD requires the same minimum cementitious material content for both classes of concrete. The purpose of this research is to determine if the cementitious material content of Class S mixtures can be reduced while still meeting AHTD specifications. The research program examined cementitious material content, Class C fly ash content, and water to cementitious material ratio (w/cm) . For all mixtures, selected fresh and hardened concrete properties were measured to ensure that they complied with AHTD requirements.




Optimization Aided Design


Book Description

Optimierungsgestütztes Entwerfen und Bemessen liefert neuartige Methoden, bewehrten Beton besonders effizient einzusetzen. Dabei wird die mathematische Optimierung auf die praktischen Probleme des Betonbaus angewendet. Ziel ist es, sparsam mit dem weltweit meistverwandten Baustoff Stahlbeton umzugehen und damit den CO2-Ausstoß aus der Zement- und Stahlherstellung und den Ressourcenverbrauch an Kies, Sand und Wasser substanziell zu reduzieren. Drei Themenbereiche sind angesprochen. Erstens, die Strukturfindung, also die Frage nach der richtigen äußeren Form, dass schlanke, nach dem Kraftfluss ausgerichtete Tragwerke entstehen. Baustoffgerecht sind sie weitgehend auf Druck beansprucht. Zweitens, die Bewehrungsführung, die sich am inneren Kraftfluss orientiert. Vorteile ergeben sich gerade für Scheiben, volumenartige Bauteile, an Lasteinleitungsbereichen und Aussparungen. Es entstehen anschauliche, direkt in Bewehrungen umsetzbare Fachwerkmodelle. Dritter Entwicklungsschritt ist die Behandlung von Querschnitten. Sie werden in ihrer Form optimiert und in ihrer Bewehrung bemessen. Dies gilt auch für anspruchsvolle Beanspruchungen (zweiachsige Biegung) und nahezu beliebige Formen. Eine Parametrisierung ermöglicht die allgemeingültige Übertragung auf ganze Klassen von Querschnitten. Die optimierungsgestützten Methoden werden vertieft und anschaulich beschrieben. Sie sind universell anwendbar und unabhängig von Normen, Betonarten und Bewehrungen. Sie gelten für normalfeste bis zu ultrahochfesten Betonen, für Bewehrungen aus Stahl, Carbon oder Glasfasern und für Bewehrungsstäbe als auch -fasern. Zahlreiche Abbildungen und Berechnungsbeispiele verdeutlichen die Anwendung. Zudem werden praktische Umsetzungen vorgestellt, darunter ultra-leichte Stahl-Beton-Balken, schlanke Solarkollektoren aus Beton und verbesserte Bewehrungslayouts für Tunnelschalen. Das Buch richtet sich gleichermaßen an Studierende, Forscher und Praktiker.




Optimization Methods for Material Design of Cement-based Composites


Book Description

Provides a clear, comprehensive introduction to the subject. Different problems of optimization are considered and illustrated with examples. Large sets of new experimental data are presented and discussed.




Performance-Based Optimization of Structures


Book Description

Performance-Based Optimization of Structures introduces a method to bridge the gap between structural optimization theory and its practical application to structural engineering. The Performance-Based Optimization (PBO) method combines modern structural optimisation theory with performance based design concepts to produce a powerful technique for use in structural design. This book provides the latest PBO techniques for achieving optimal topologies and shapes of continuum structures with stress, displacement and mean compliance constraints. The emphasis is strongly placed on practical applications of automated PBO techniques to the strut-and-tie modelling of structural concrete, which includes reinforced and prestressed concrete structures. Basic concepts underlying the development of strut-and-lie models, design optimization procedure, and detailing of structural concrete are described in detail. Alternative approaches to topology optimization are also introduced. The book contains numerous practical design examples illustrating the nature of the load transfer mechanism of structures.







Optimization Methods for Material Design of Cement-based Composites


Book Description

Provides a clear, comprehensive introduction to the subject. Different problems of optimization are considered and illustrated with examples. Large sets of new experimental data are presented and discussed.




Guidelines for Optimizing the Risk and Cost of Materials QA Programs


Book Description

TRB’s National Cooperative Highway Research Program (NCHRP) Research Report 838: Guidelines for Optimizing the Risk and Cost of Materials QA Programs proposes guidelines for optimizing the risk and cost of materials quality assurance (QA) programs. It develops a methodology for establishing a materials QA program that optimizes risk and cost by providing appropriate types, levels, and frequencies of agency testing and inspection for transportation projects across their full range of type, size, complexity, and project-delivery method.




Process Optimization for 3D Printing of Cementitious Materials


Book Description

Three-dimensional (3D) concrete printers are extensively portable; they can save construction time and reduce labor costs. This technology is incredibly capable of creating complex elements with different structural scales. Some 3D concrete printers use a gantry system, while other printers may use a robotic arm or generalized Stewart platforms. These systems allow the freedom of movements to create desired concrete structures. The structures are printed layer-by-layer using additive manufacturing methods to ensure the overlay between the concrete layers. The components of a 3D printer play an important role in the print quality. For instance, the nozzle shape has a direct influence on the overall form of the structure, stress distribution, and durability of the printed element. Since the 3D concrete printers are at a very early development stage, part optimization is crucial for the ease of construction. Therefore, the first part of this research study focuses on developing different nozzle forms, extruder control system, and pump parameters. The outcome of the first part provides insights into 3D concrete printing protocols and can be used to optimize the process. The second part of this study focuses on the development of a novel composite material that meets the requirements used in the construction field. This research focuses on 3D concrete printing features, such as extruder and nozzle design, and their effect on the printed structures, while evaluating printing strategies using a developed concrete mixture that has the desired mechanical properties.




Integrated life cycle assessment of concrete structures


Book Description

Concrete is after water the second most used material. The production of concrete in the industrialized countries annually amounts to 1.5-3 tonne per capita and is still increasing. This has significant impact on the environment. Thus there is an urgent need for more effective use of concrete in structures and their assessment. The scope of activities of the fib Task Group 3.7 was to define the methodology for integrated life-cycle assessment of concrete structures considering main essential aspects of sustainability such as: environmental, economic and social aspects throughout the whole life of the concrete structure. The aim was to set up basic methodology to be helpful in development of design and assessment tools focused on sustainability of concrete structure within the whole life cycle. Integrated Life Cycle Assessment (ILCA) represents an advanced approach integrating different aspects of sustainability in one complex assessment procedure. The integrated approach is necessary to insure that the structure will serve during the whole expected service life with a maximum functional quality and safety, while environmental and economic loads will be kept at a low level. The effective application and quality of results are dependent on the availability of relevant input data obtained using a detailed inventory analysis, based on specific regional conditions. The evaluation of the real level of total quality of concrete structure should be based on a detailed ILCA analysis using regionally or locally relevant data sets.




Design and Control of Concrete Mixtures


Book Description

Portland Cement Association reference, dealing with fundamentals, cold weather concreting, curing, admixtures, aggregates, mixing, and much more.