Carl-Alexander Graubner

Formwork Pressure of Concretes with high Workability

In the last 15 years the application of high-workability concretes has increased significantly. Such concretes have a spread value larger than 55 cm according to DIN EN 12350-5 (2000) and are classified into the consistency classes F5, F6 (vibrated concretes) and Self-Compacting Concretes (SCC) according to DIN EN 206-1 (2001). Using SCC a mechanical compaction is not necessary anymore.

Formwork Pressure of Highly Workable Concrete – Experiments Focused on Setting, Vibration and Design Approach

The presented investigations were conducted at the Institut fur Massivbau and contributed to a joint research project including several German research institutes [1]. A number of experimental tests on highly workable concretes were carried out. Small scale material analyses as well as measurements of the formwork pressure on large specimens were carried out. Based on the test results an analytical model for the calculation of the concrete pressure on vertical formwork was developed. The analytical model takes into account the time dependent material parameters of the fresh concrete, the specific properties of highly workable vibrated concretes and self-compacting concretes (SCC) as well as operation aspects. A proposal for the design of formwork, based on the experimental tests and the semi-probabilistic safety concept was developed. It was found that even for highly workable concretes, the design load is often lower than the hydrostatic concrete pressure.

Eco-Friendly Concretes With Reduced Water and Cement Content: Mix Design Principles and Experimental Tests

The major environmental impact of concrete is caused by CO 2 emissions during cement production. Great potential for reducing the impact is seen especially for concretes with normal strength. The use of superplasticizers and highly reactive cements as well as an optimization of particle-size distribution and reduction in water content allow a significant reduction in Portland cement clinker in the cement and concrete. Essential is the addition of mineral fillers (e.g., limestone powder) to provide an optimal paste volume. In addition, the already practicable substitution of secondary raw materials like fly ash or furnace slag for cement clinker is an appropriate option that is, however, limited by the availability of these resources.

A new approach to measure sustainability in German facility management

Purpose – The purpose of this paper is to present the development of an action and assessment framework to make sustainability in German facility management (FM) transparent, measurable and assessable. Design/methodology/approach – The underlying research project’s approach to develop the new action and assessment framework consisted of a three-step methodology: to define and substantiate sustainability in FM, to operationalise and quantify sustainability in FM and to validate the developed system draft through an initial pilot study. Findings – The main result of the presented research project is a set of 24 criteria, organised into the separate areas of environmental, economic and sociocultural quality, as well as the quality of FM organisation and the sustainability of building/contract-specific facility services. The assessment methodology reflects the strategic approach of a plan–do–check–act loop to create a transparent and objective appraisal and a practical action framework. Research limitations/i...

SPANNBETONBAUWERKE. TEIL 2: BEMESSUNGSBEISPIELE NACH EUROCODE 2

Der zweite Teil des Handbuchs umfasst eine Beispielsammlung zur Bemessung von Spannbetonbauwerken nach Eurocode 2 unter Beruecksichtigung saemtlicher bisher erschienenen nationalen Anwendungsdokumente. Die Beispiele stammen aus den Bereichen des Strassen- und Eisenbahnbrueckenbaus sowie des Hoch- und Industriebaus und decken hinsichtlich Vorspanngrad und Verbundart das gesamte Gebiet des Spannbetons ab. Die mit der Ausfuehrlichkeit einer statischen Berechnung aufgestellten Beispiele werden durch umfangreiche Erlaeuterungen und detaillierte Hinweise auf massgebende Normenabschnitte und Anwendungsrichtlinien begleitet, so dass Systematik und Ablauf der Bemessungsschritte des neuen Normenkonzepts schnell verstaendlich und nachvollziehbar sind. Zur Erleichterung der Orientierung enthaelt der Anhang eine ergaenzende tabellarische Uebersicht zum gesamten Nachweiskonzept. Da in diesem zweiten Teil des Handbuchs die gleichen Beispiele (mit Ausnahme des nur selten verlangten Kranbahntraegers) wie im ersten Teil (mit Bemessung nach DIN 4227) behandelt werden, ergibt sich eine unmittelbare Vergleichsmoeglichkeit in der Anwendung der deutschen und europaeischen Vorschriften. (A*) (= Handbuch fuer Beton-, Stahlbeton- und Spannbetonbau).

Sustainable development in the building industry: an analysis and assessment tool for design of disassembly

Ecologically Sustainable Development (ESD) has been embraced by governments worldwide and as building plays a key role in development, it is implicated in this movement. Consideration of the whole life cycle of a building is a major aspect, when assessing its sustainability. While the reduction of operating energy and the optimization of building material selection has been a main focus of research in Europe, the consideration of maintenance during operation or the demolition of a building at the end of its life has usually been neglected. Aiming for sustainability the conversation of materials and energy by applying a closed system approach on a long term time scale must be realized. Therefore building materials are to be recycled, building elements are to be reused and buildings are to be more flexible. Designing to facilitate the disassembly of building elements is expected to be an improvement for sustainable buildings. A tool for the assessment of building elements has been developed that focuses on connection selection, its influence on material and energy flow, as well as the quality of building waste materials. The assessment of material production and erection processes, using Life Cycle Assessment is completed with a qualitative/quantitative classification of demolition processes, and disposal scenarios, considering environmental, economic and technical aspects. An analysis of floor elements has confirmed, that Design for Disassembly is very promising for the improvement of sustainable buildings but that improvement potentials can differ considerably. Details of the analysis tool developed and an analysis of building elements will be shown in this article

Floor Live Loads of Building Structures

Floor live loads are fundamental to structural design of buildings. A correct understanding of the intensity of loading is necessary for economic and safe design of structures. In the practical application, the defined design load values are not always the same in design codes. According to EN 1991-1-1, for example, the characteristic value of live load for office buildings is suggested to 3 kN/m2. In DIN EN 1991-1-1/NA (2010), however, the live load for offices is defined with a characteristic value of 2 kN/m2. Furthermore, the occupancy type of a building may be changed after a period of time. In this case, the building structure should be checked for the load carrying capacity when the new load is applied. Therefore, more accurate and reliable information of the load is very useful for the reliability evaluation of the studied structure. To check the accuracy of live load values for design, floor live loads were modelled and numerically simulated for different usage situations. The simulation used the statistical results of existing load surveys as input parameters. Characteristic values of live load for different load effects and possible live load reductions were determined.

Shrinkage of Mortar Samples Made of Limestone-Rich Cements

Shrinkage in concrete structures may lead to cracks which reduce the durability of concrete against aggressive mediums. In prestressed concrete elements shrinkage results in a significant loss of prestressing forces. Limestone-rich cements with limestone contents beyond the values of DIN EN 197-1 were developed in order to reduce the influence of cement production on environment. In this paper the shrinkage behavior of mortar and concrete samples made of limestone-rich cements up to 70 wt.% with different water/cement-ratios was analyzed. The results indicate that shrinkage of such cements is strongly dependent on the amount, chemical and physical properties and the mineral components of limestone. The mortar samples made of such cements had shown both higher or lower shrinkage than reference samples made of pure Portland cement (CEM I 52,5 R) depending on the used limestone type. Specific surface area measured by BET-method seems to play a key role on the shrinkage behavior by controlling the disjoining pressure between hydration products. Meanwhile, it was found that in contrary to reference samples the prolonged curing in water does not influence the shrinkage of specimens made of limestone-rich cements significantly.

Erdbebenbemessung massiver Wohngebäude

Der Beitrag befast sich mit Neuregelungen zur Erdbebenbemessung fur Bauwerke aus Beton und Mauerwerk nach den europaischen Vorschriften des Eurocode 8 im Vergleich zu den bisherigen Festlegungen nach DIN 4149. Es wird gezeigt, das die Anwendung von EC 8 bei massiven Wohngebauden in Gebieten mit kleiner Erdbebenbeanspruchung zu einer deutlichen Vergroserung der anzusetzenden Einwirkungen fuhrt. Weiterhin kann demonstriert werden, das die im EC 8 vorgesehene Unterscheidung von Stahlbetonbauteilen nach Duktilitatsklassen fur Wohngebaude niedriger Hohe keine Vorteile bietet, die den erhohten Bemessungsaufwand rechtfertigen.