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Isaacs, Ben; Lark, Robert; Jefferson, Tony; Davies, Robert; Dunn, Simon Crack healing of cementitious materials using shrinkable polymer tendons Structural Concrete 2/2013 138-147 Technical Papers

Kurzfassung

This paper presents an experimental study on autogenous healing in a recently developed shrinkable polymer cementitious material system. Small-scale hollow prismatic mortar beams with unbonded shrinkable polymer tendons were loaded until a crack of predefined width had formed. The specimens were then subjected to a range of combined heating/curing regimes to activate the shrinkable polymer and to promote autogenous healing of the cementitious material prior to reloading to failure. Upon reloading, specimens loaded with the shrinkable polymer tendons remaining after heating and curing achieved between 120 and 195% of their initial peak loads, whereas specimens tested with the shrinkable polymer tendons removed after the heating and curing stages recovered on average 80% of their initial peak loads. The overall conclusion was that, provided a supply of water is present and sufficient heat is applied for polymer activation, the material system is effective at not only closing cracks and applying a prestress, but also at enhancing the self-healing of cracks in cementitious materials.

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Ng, Tian Sing; Foster, Stephen J. Development of a mix design methodology for high-performance geopolymer mortars Structural Concrete 2/2013 148-156 Technical Papers

Kurzfassung

This paper presents the development of a mix design method for geopolymer mortar mixes with a principal focus on compressive strength. The method is based on the hypothesis that the overall strength of geopolymer mortar depends on the strength of the geopolymer binder materials, the packing density of the aggregates in the mortar and the amount of geopolymer binder. First, the strength of the binder was evaluated experimentally. Fly ash obtained from two different sources and ground granulated blast-furnace slag were used as the main ingredients in the production of the geopolymer binder. Correlation between the packing density of the aggregates in the mortar and their influence on the binder demand and compressive strength were investigated. Finally, a conceptual framework for a geopolymer mortar mix design approach is proposed. In addition to describing the mortar mix design methodology in a rational way, it is hypothesized that the approach can also be extended to the development of a geopolymer concrete mix.

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Clément, Thibault; Ramos, António Pinho; Fernández Ruiz, Miguel; Muttoni, Aurelio Design for punching of prestressed concrete slabs Structural Concrete 2/2013 157-167 Technical Papers

Kurzfassung

Prestressing in flat slabs helps to control deformations and cracking under service loads and allows the required slab thickness to be reduced, thus leading to more slender structures and an economic solution for long spans. However, as a consequence of the limited thickness of these members, punching typically governs at the ultimate limit state. Studies of the punching shear strength have shown that the presence of prestressing in flat slabs has a number of potential beneficial effects, namely the vertical component (force) carried by inclined tendons, the in-plane compression stresses and the bending moments developed near the supported region. However, the approach provided by codes of practice for punching design in the presence of prestressing may differ significantly. Some codes neglect the influence of the bending moments introduced as a result of prestressing and the sections at which the deviation forces of the tendons are considered may be located at different distances from the edge of the supported region. The influence of prestressing on the punching shear strength of members without shear reinforcement is investigated in this paper by using the fundamentals of the critical shear crack theory. Using that as a basis, and also taking into account 65 tests available in the scientific literature, the suitability and accuracy of a number of design codes, e.g. Model Code 2010, Eurocode 2 and ACI 318-11, are investigated and compared.

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Xiao, Jianzhuang; Fan, Yuhui; Tawana, M.M. Residual compressive and flexural strength of a recycled aggregate concrete following elevated temperatures Structural Concrete 2/2013 168-175 Technical Papers

Kurzfassung

A recycled aggregate concrete (RAC) with different replacement percentages of recycled coarse aggregates (RCAs) (i.e. 0, 30, 50, 70, 100%) was investigated experimentally at elevated temperatures. The residual compressive strength as well as the residual flexural strength of the RAC following elevated temperatures was studied and evaluated. A relationship between the residual compressive flexural strength of RAC and the elevated temperature was proposed. Furthermore, the relationship between the residual flexural strength and the compressive strength of the RAC was compared and analysed. It was found that both the residual compressive strength and the residual flexural strength of the RAC decrease with a rise in temperature, and the effect of the RCAs replacement percentage on the residual flexural strength and the residual compressive strength of RAC was found to be obvious.

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Khazraiyan, Najmeh; Liaghat, Gholam Hossein; Khodarahmi, Hossein Normal impact of hard projectiles on concrete targets Structural Concrete 2/2013 176-183 Technical Papers

Kurzfassung

This research study involves obtaining an analytical model for the perforation of unreinforced concrete targets by a hemispherical hard projectile. Dynamic cavity expansion theory and the reflection of compressive waves from the end of the concrete targets are used for developing the analytical model. The effect of the friction coefficient is also investigated in the analysis. Numerical modelling of the problem has been performed in LS-DYNA code for validating the analytical results. Johnson-Holmquist concrete and rigid material models have been employed for the concrete and the projectile respectively. The impact velocity range considered in this work is between 250 and 850 m/s. No projectile erosion is considered in this range. The analytical results have been compared with numerical results and show good agreement with numerical simulations.

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fib-news: Structural Concrete 2/2013 Structural Concrete 2/2013 185-191 fib-news

Kurzfassung

• 2013 fib symposium in Tel Aviv: Engineering a Concrete Future
• 2013 fib Medal of Merit and Honorary Membership
• 2013 Achievement Award for Young Engineers
fibUK meeting
• Advances in Cement and Concrete Technology in Africa (ACCTA)
• Report from the Norwegian fib Member Group)
• Congresses and symposia

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Contents: UnternehmerBrief Bauwirtschaft 2/2013 UnternehmerBrief Bauwirtschaft 2/2013 Contents

Kurzfassung

No Abstract.

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Schalk, Günther Wer nicht wirbt, der stirbt ?? UnternehmerBrief Bauwirtschaft 2/2013 1 Editorial

Kurzfassung

No Abstract.

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Kurz infomiert UnternehmerBrief Bauwirtschaft 2/2013 2 Kurz informiert

Kurzfassung

Mit dem BauGB im Kampf gegen verwahrloste Immobilien
Finanzierungslücke im Verkehrsbereich “alarmierend”
Getrübte Erwartungen der Architekten

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Riesterer, Ramona Öffentlichkeitsarbeit - auch für kleine Baufirmen ein Thema! UnternehmerBrief Bauwirtschaft 2/2013 3-10 Berichte

Kurzfassung

Autohäuser, Restaurants, Bekleidungsgeschäfte und Supermärkte - für alle ist Werbung selbstverständlich. Aber für Bauunternehmen? Auch eine Baufirma braucht Werbung. Die Kombination entpuppt sich in der Praxis allerdings vielfach als kompliziert und ungelenk: Die Kommunikationswissenschaft und das Fach Marketing stellen zwar viele Modelle und Handlungsempfehlungen bereit, die (auch Bau-)Unternehmen dabei helfen sollen, ihre externe Kommunikation strategisch und operativ optimal zu gestalten. Doch viele Unternehmer, nicht nur kleine Firmen, blicken eher etwas ratlos auf bis zu 12-stufige Kommunikationsmanagement-Prozesse [1] und fragen sich, woher man Zeit und Geld nehmen soll, um in der Praxis abzubilden, was in der Theorie wortreich beschrieben ist.

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Fuchs, Bastian; Schalk, Günther Aktuelles aus der Rechtsprechung UnternehmerBrief Bauwirtschaft 2/2013 11-13 Berichte

Kurzfassung

No Abstract.

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Gewerbeertrag: Einspruch trotz Vorläufigkeitsvermerks UnternehmerBrief Bauwirtschaft 2/2013 14 Berichte

Kurzfassung

No Abstract.

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Steuererklärung jetzt zwingend elektronisch einzureichen? UnternehmerBrief Bauwirtschaft 2/2013 14 Berichte

Kurzfassung

No Abstract.

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Telefonkosten auf beruflicher Auswärtstätigkeit UnternehmerBrief Bauwirtschaft 2/2013 15 Berichte

Kurzfassung

No Abstract.

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Bundesfinanzhof hat keine Zweifel UnternehmerBrief Bauwirtschaft 2/2013 15 Berichte

Kurzfassung

No Abstract.

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Firmenfahrzeug: Keine automatiche Zwangsentnahme UnternehmerBrief Bauwirtschaft 2/2013 16 Berichte

Kurzfassung

No Abstract.

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"Reverse-Charge-Verfahren" auf dem Prüfstand UnternehmerBrief Bauwirtschaft 2/2013 16 Berichte

Kurzfassung

No Abstract.

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Schalk, Günther Geiz ist am Bau nicht geil ? UnternehmerBrief Bauwirtschaft 2/2013 17 Berichte

Kurzfassung

No Abstract.

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Sicherheitseinbehalte sind steuerlich korrekt zu erfassen UnternehmerBrief Bauwirtschaft 2/2013 18-19 Berichte

Kurzfassung

No Abstract.

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Schalk, Günther Boden als Grundlage für den Bau UnternehmerBrief Bauwirtschaft 2/2013 20 Buchtipp

Kurzfassung

No Abstract.

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UBB-Veranstaltungstipps UnternehmerBrief Bauwirtschaft 2/2013 20 Veranstaltungen

Kurzfassung

No Abstract.

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Inhalt: Bauphysik 1/2013 Bauphysik 1/2013 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Ernst & Sohn (Hrsg.) Jahresinhaltsverzeichnis 2012 Bauphysik 1/2013 00 Jahresinhaltsverzeichnis

Kurzfassung

Keine Kurzfassung verfügbar.

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Nytsch-Geusen, Christoph Gebäudesimulation auf den Größenskalen Bauteil - Raum - Gebäude - Stadtquartier Bauphysik 1/2013 1 Editorial

Kurzfassung

Keine Kurzfassung verfügbar.

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Uphoff, Sonja; Krafczyk, Manfred; Martin , Schönherr; Stiebler, Maik; Zargari, Mani Numerische Simulation von Gebäudebelüftung mit einem Lattice Boltzmann-LES-Modell Bauphysik 1/2013 2-7 Fachthemen

Kurzfassung

In diesem Beitrag werden Belüftungseffekte am Beispiel des EnergieForums Berlin untersucht. Um Erkenntnisse über den Einfluss fluktuierender Windfelder auf die Belüftung zu erzielen, wird die Windumströmung und Temperatur im und um das Atriumgebäude mit einer Large Eddy Simulation (LES)-Modell zeitaufgelöst und räumlich untersucht. Dazu wird das Lattice Boltzmann-Verfahren mit dem Multi Relaxation Time (MRT)-Modell auf einem D3Q19-Gitter verwendet. Das kürzlich entwickelte Eso-Twist-Verfahren, das nur einen einzigen Lattice Boltzmann-Verteilungssatz benötigt, kommt zum Einsatz. Als LES-Modell wird das Smagorinsky-Modell verwendet. Zur Temperaturmodellierung dient das HTLB-Verfahren. Die Simulationen werden CUDA-basiert auf einer GeForceGTX 580 GPGPU durchgeführt. Anhand der Simulationen wird der Abfall der Tracergaskonzentration über der Zeit sowie der mittlere, durch Temperaturunterschiede und äußeren Wind induzierte Fluss bestimmt.

Numerical simulation of building ventilation with a Lattice Boltzmann LES model.
In this contribution ventilation effects are studied for the EnergieForum Berlin. To estimate the influence of external wind fields on the ventilation process, wind and temperature fields are simulated with a large eddy simulation (LES) model. With this approach spatially-and time-resolved output is generated. The Lattice Boltzmann method is being used on a D3Q19 grid with a multiple relaxation time (MRT) model. The recently developed EsoTwist scheme, which uses only a single set of LB distributions, is employed. The Smagorinsky model serves as the LES model. To model the temperature dynamics, the HTLBE method is used. The simulations are CUDA-based and carried out on a GeForce GTX580 GPGPU. The decay of the tracer-gas concentration over time and the mean flow through the building generated by temperature gradients and external wind is determined.

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