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Scott, Richard Serviceability uncertainties in flat slabs Structural Concrete 4/2014 469-483 Technical Papers

Kurzfassung

Service load tests on the 6th floor of the full-scale reinforced concrete building at BRE Cardington are described. Both deflections and reinforcement strains were measured. Finite element analyses of the floor slab were then undertaken using the measured material properties and four different models for the behaviour of the concrete in tension, the tension stiffening effect being known to influence slab behaviour significantly. Calculated deflections and reinforcement strains from the four analyses were compared with values measured in the load tests. As a consequence, comments, reservations and recommendations are made concerning the use of FE analyses for predicting deflections and reinforcement strains. Finally, the need to appreciate and accommodate the indeterminate nature of many of the parameters involved is emphasized.

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Winkler, Karsten; Mark, Peter; Heek, Peter; Rohländer, Sandra; Sommer, Simone Punching shear tests on symmetrically reduced slab quarters Structural Concrete 4/2014 484-496 Technical Papers

Kurzfassung

Experiments on large-scale reinforced concrete members such as beams or slabs with large effective depths are challenging and - not least due to the extensive material and financial input - rarely performed. However, results from such experiments are desperately needed, as critical size effects affect shear and punching shear failure types. At the Institute of Concrete Structures at Ruhr-Universität Bochum (RUB), an innovative test setup was devised following the principle of “upsizing by downsizing”. It transfers symmetry reductions - a standard feature in numerical simulations - to experiments. Thus, test loads and dead loads decrease markedly in proportion to the degree of symmetry, giving rise to larger specimens within given testing facilities. The setup enables tests on symmetrically sectioned concrete members - halved beams or quarters of slabs - concurrently implying the load-deformation behaviours of corresponding, i.e. full-size members, by simply factoring the loads with twice the axial symmetry degree.
This paper presents the single steps in the development to test quartered slabs, including the modular support constructions with sliding planes and anchoring of the bending reinforcement as well as the concrete specimen itself, with interconnections to the symmetry planes, measuring techniques and its specific assembly. Results from a first prototype testing prove the general applicability for failure modes, crack patterns and kinematics. However, ultimate punching loads are still slightly overestimated.

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Siburg, Carsten; Ricker, Marcus; Hegger, Josef Punching shear design of footings: critical review of different code provisions Structural Concrete 4/2014 497-508 Technical Papers

Kurzfassung

Eurocode 2 and the corresponding National Annex were introduced in Germany in 2012. Most of the design provisions for these new standards were adopted from Model Code 1990 and provide a new design approach for ground slabs and footings. For the fib Model Code for Concrete Structures 2010, the punching shear design concept has been revised and introduced in Swiss standard SIA262:2013. This paper presents in detail the design equations for determining the punching capacity according to Eurocode 2, the German National Annex to Eurocode 2, fib Model Code 2010 and SIA 262:2013.
Parametric studies have been used to examine the influence of the main parameters (shear span-depth ratio, effective depth, longitudinal reinforcement ratio and concrete compressive strength) on the punching shear resistance of footings. To quantify the level of safety and the efficiency, the design provisions are compared with systematic test series.

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Abdellahi, Majid; Heidari, Javad; Bahmanpour, Maryam A new predictive model for the bond strength of FRP-to-concrete composite joints Structural Concrete 4/2014 509-521 Technical Papers

Kurzfassung

In this work, gene expression programming (GEP), as a new tool, has been used to predict the bond strength of fibre-reinforced polymer-to-concrete composite joints as the performance symbol of this structure. Some 238 datasets were collected from the literature, divided into 192 and 46 sets at random and then trained and tested respectively by means of GEP. The parameters width of prism, concrete cylinder compressive strength, width of fibre-reinforced polymer (FRP), thickness of FRP, modulus of elasticity of FRP and bond length were used as input parameters. Using these input parameters, the bond strength of FRP-to-concrete composite joints in different conditions was predicted in the GEP model. The training and testing results in the GEP model show that GEP is a powerful tool for predicting the bond strength values of the FRP-to-concrete composite joints in the range considered.

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Hertz, Kristian; Castberg, Andreas; Christensen, Jacob Super-light concrete decks for building floor slabs Structural Concrete 4/2014 522-529 Technical Papers

Kurzfassung

This paper presents investigations carried out at the Technical University of Denmark (DTU) on a prototype series for a super-lightweight prestressed concrete deck element called the SL-Deck.
The intention behind making a new prefabricated deck element is to improve performance with respect to flexibility, sound insulation and fire resistance compared with present-day prefabricated structures.
Full-scale tests and theoretical investigations show that the deck structure performs as intended. Also, that it is possible to assess by calculation the loadbearing capacity in bending and shear, and assess the pull-out strength of prestressing wires, the fire resistance and the acoustic insulation. Based on the results of the investigations, recommendations are given for further development of the structure before fully automated mass production is established.

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Urban, Susanne; Strauss, Alfred; Schütz, Robert; Bergmeister, Konrad; Dehlinger, Christian Dynamically loaded concrete structures - monitoring-based assessment of the real degree of fatigue deterioration Structural Concrete 4/2014 530-542 Technical Papers

Kurzfassung

When it comes to dynamically loaded concrete structures, determining the real degree of fatigue damage of a structure on site is a very demanding process that has not been explored in depth. Calculation concepts according to current codes and specifications (e.g. fib Model Code for Concrete Structures 2010 [1]) do not offer efficient results for this task. However, the permanent monitoring from the erection of a structure up to the end of its lifetime is seen as a very promising possibility for assessing the degree of damage constantly. This article takes a closer look at the concrete fatigue concept of fib Model Code 2010 [1], shows an FE simulation of a time-dependent fatigue process for an offshore wind turbine foundation and presents a fatigue monitoring concept including laboratory tests, which enables the detection of the real degree of deterioration in a concrete structure. During tests, the use of ultrasound was identified as the most appropriate method. Measuring wave velocity enables the determination of the dynamic E-modulus, which correlates to the degree of damage within the cross-section of the structure considered.

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Won, Deok Hee; Park, Woo Sun; Jang, In-Sung; Han, Sang-Hun; Han, Taek Hee Fire resistance performance of steel composite hollow RC column with inner tube under ISO 834 standard fire Structural Concrete 4/2014 543-555 Technical Papers

Kurzfassung

An internally confined hollow RC (ICH RC) column offers strong and durable confinement owing to the reinforcement provided by the inner tube. The strength and ductility of the column are enhanced because of the continuous confining stress provided by the inner tube. The excellent structural performance of ICH RC columns makes them particularly suitable for applications in high-rise buildings. However, if a high-rise building is damaged by fire, it will collapse without fire resistance performance. Also, lack of evacuation measures endangers human life. Thus, to predict the status of structures in fires, their behaviour should be evaluated in terms of fire time. In this study, the fire resistance performance of an ICH RC column was analysed during an ISO 834 standard fire and with certain initial conditions. Furthermore, the effects of hollow ratio, thickness of inner tube and thickness of cover concrete on the fire resistance performance were analysed. The results could be used for designing fire-resistant ICH RC columns.

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Messari-Becker, Lamia; Mettke, Angelika; Knappe, Florian; Storck, Ulrich; Bollinger, Klaus; Grohmann, Manfred Recycling concrete in practice - a chance for sustainable resource management Structural Concrete 4/2014 556-562 Technical Papers

Kurzfassung

Private households consume about 30 % of Germany's total primary energy and cause about 15 % of the total CO2 emissions, and so this sector represents a key sector for climate protection targets. Whereas primary energy consumption in buildings is limited by regulations, the production of carbon emissions-intensive materials is only moving slowly into the focus of legislation, regulations and, ultimately, the perception of society. Considering a thermally conditioned building during its life cycle, most environmental effects are during operation. Nevertheless, the grey energy of a concrete structure can add up to 20 % in individual cases. Owing to the carbon-intensive cement production, concrete as a material causes relatively high environmental impacts. Logical options appear to be substituting cement with so called by-products or using recycled additives. In fact, there are only a few projects that have used a resource-saving concrete. In 2010 in Ludwigshafen, one building in a group of buildings was chosen as the first building in Germany to be built almost completely from recycled concrete without increasing the cement content. It was built as a low-energy construction and in a zero-carbon-emissions area. The project was supported scientifically by the Institute of Energy and Environmental Research in Heidelberg and the Brandenburg University of Technology Cottbus. The buildings won the Construction Prize 2011 with the distinction “best relation between quality and costs”. This paper discusses integral aspects of the use of recycling concrete from the structural design, eco-accounting and materials properties perspectives. It demonstrates the potential and opportunities for the quality-assured use of recycling concrete for sustainable resource management.

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Randl, Norbert; Kunz, Jakob Post-installed reinforcement connections at ultimate and serviceability limit states Structural Concrete 4/2014 563-574 Technical Papers

Kurzfassung

When reinforcing bars are post-installed in holes drilled in cured concrete, adhesive mortars are used to create a bond between concrete and bars. Appropriate adhesives can develop higher bond strengths than standard ribbed bars cast into concrete. A detailed design concept for the anchorage length of reinforcing bars has been developed by taking into account splitting/spalling of the concrete and pullout. Pullout and splitting tests on reinforcing bars set in concrete were carried out with different adhesive mortars and with varying concrete strengths and concrete covers. When higher bond strengths than those recommended for cast-in reinforcement are taken into account, it is important to check deformations and crack widths at the serviceability limit state (SLS) separately. For this reason, structural tests on slabs and corbels were carried out. Moreover, pullout tests on post-installed reinforcing bars were performed in order to measure displacements at service load level.

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Korte, Sara; Boel, Veerle; De Corte, Wouter; De Schutter, Geert Behaviour of fatigue loaded self-compacting concrete compared to vibrated concrete Structural Concrete 4/2014 575-589 Technical Papers

Kurzfassung

Fatigue loading and its sometimes inevitable fatigue failure are common in many civil engineering construction projects. The behaviour of vibrated concrete (VC) under this type of loading is well understood. However, the fracture and fatigue resistance of self-compacting concrete (SCC) is poorly documented in literature. Considering the substantially different composition of the two concrete types (VC and SCC), it is uncertain whether their mechanical properties are similar or not. This paper describes the results of a series of destructive static and cyclic four-point bending tests on inverted T-shaped reinforced concrete beams, made from VC and SCC in equal quantities and of equal compressive strength. A comparison of the two concrete types is made, based on deflection, strain, crack width evolution and failure mechanism. The experiments prove that these mechanical properties of VC and SCC, subjected to a fatigue load, in some cases relate differently from a static loading process. Furthermore, the results reveal a faster concrete strain and crack width development for SCC during the fatigue tests. Regarding the number of cycles to failure, the applied load level is crucial.

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2014 reviewers Structural Concrete 4/2014 590 Reviewers

Kurzfassung

Keine Kurzfassung verfügbar.

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fib-news: Structural Concrete 4/2014 Structural Concrete 4/2014 591-597 fib-news

Kurzfassung

Structural changes in the fib; 60 years of setting standards; Summer studies in Milan; fib Bulletin 73; New fib Presidium; HPC conference and MC2010 workshop in Beijing; Short notes; Congresses and symposia; Acknowledgement

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Structural Concrete 1/2015 Structural Concrete 4/2014 598 Preview

Kurzfassung

Keine Kurzfassung verfügbar.

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Inhalt: UnternehmerBrief Bauwirtschaft 4/2014 UnternehmerBrief Bauwirtschaft 4/2014 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Schroeter, Heinrich Wo kommen die Ingenieure her? UnternehmerBrief Bauwirtschaft 4/2014 1 Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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Kurz informiert: UnternehmerBrief Bauwirtschaft 4/2014 UnternehmerBrief Bauwirtschaft 4/2014 2 Kurz informiert

Kurzfassung

ÖPP und PPP sind nicht so schlecht wie ihr Ruf
Deutscher Immobilienmarkt als “sicherer Hafen”
Lob für Gesetzentwurf gegen Zahlungsausfälle am Bau

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Danielzik, Jürgen; Stenger, Stefan Duales Studium schafft ideale Führungskräfte von morgen UnternehmerBrief Bauwirtschaft 4/2014 3-9 Berichte

Kurzfassung

Unsere Gesellschaft und mit ihr die Bauwirtschaft befindet sich im demographischen Wandel. Als direkt spürbare Folge zeigt sich in vielen Unternehmensbereichen der Mangel an gut ausgebildeten Nachwuchs-Führungskräften. Heute und vermehrt in der Zukunft verlieren die Bauunternehmen in allen Hierarchieebenen wichtige Fachkompetenzen durch das altersbedingte Ausscheiden von erfahrenen Führungskräften. Für Baufirmen aller Größenordnungen stellt sich daher seit längerem die gleiche Frage: “Woher bzw. wie bekomme ich meine Führungskräfte von morgen, die sowohl in Theorie als auch der Praxis überzeugen können?” Eine Antwort auf diese Frage ist ein Absolvent eines dualen Studiengangs, der eine qualifizierte Ausbildung in einem Bauberuf des Hoch- oder Tiefbaus mit einem Hochschulstudium zum Bauingenieur kombiniert.

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BMWi-Markterschließungsprogramm für KMU UnternehmerBrief Bauwirtschaft 4/2014 9 Berichte

Kurzfassung

Keine Kurzfassung verfügbar.

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Talebitari, Burkhard Feiermarathon: BVMB wird 50 und vollzieht Generationenwechsel UnternehmerBrief Bauwirtschaft 4/2014 10-12 Berichte

Kurzfassung

Der Wechsel des Hauptgeschäftsführers der BVMB von Friedhelm Noss zu Michael Gilka - 50 Jahre Bundesvereinigung Mittelständischer Bauunternehmen e.V. - traditioneller Neujahrsempfang: Anlass zum Feiern, diesmal im Bonner Maritim-Hotel mit über 650 Teilnehmern, aber auch Anlass für deutliche Worte des Präsidenten der BVMB, Thorsten Bode. Denn zum Ausruhen, zumal nach wenig Winter, lässt die aktuelle Situation am Bau der nun 50jährigen, wie eh und je schlagkräftigen Vereinigung, wenig Zeit...

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Hendricks, Barbara Ehrgeizige Ziele im neuen Haus UnternehmerBrief Bauwirtschaft 4/2014 13 Berichte

Kurzfassung

Grußwort der Bundesministerin für Umwelt, Naturschutz, Bau und Reaktorsicherheit

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Englert, Florian Aktuelles aus der Rechtsprechung UnternehmerBrief Bauwirtschaft 4/2014 14-15 Berichte

Kurzfassung

Bindung an Schlussrechnung oder Korrekturmöglichkeit?
Planungsfehler und deren Ausläufer

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So vermeiden Geschäftsführer eine Lohnsteuer-Haftung UnternehmerBrief Bauwirtschaft 4/2014 16 Berichte

Kurzfassung

Gerät eine GmbH in finanzielle Schieflage und stellt sich dabei heraus, dass die Lohnsteuer nicht korrekt ans Finanzamt abgeführt wurde, droht den Geschäftsführern eine persönliche Haftung. Doch mit ein paar relativ einfachen Vereinbarungen und Überwachungsschritten kann das Haftungsrisiko minimiert werden.

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Nachzahlungen bei einer Betriebsprüfung legal "kleinrechnen" UnternehmerBrief Bauwirtschaft 4/2014 16 Berichte

Kurzfassung

Gerade kleine und mittelständische Unternehmer müssen bei Betriebsprüfungen des Finanzamts meist tief in die Tasche greifen und Steuern nachzahlen. Doch liegen die Voraussetzungen für den Investitionsabzugsbetrag vor, können die Steuernachzahlungen “kleingerechnet” werden.

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Ehegatten-Arbeitsverhältnis mit Dienstwagen zulässig UnternehmerBrief Bauwirtschaft 4/2014 17 Berichte

Kurzfassung

Stellt ein Unternehmer seinen Ehegatten oder Partner einer eingetragenen Lebenspartnerschaft in seinem Betrieb inklusive Gestellung eines Dienstwagens an, ruft das stets das Finanzamt auf den Plan. Damit die Anstellung vom Finanzamt akzeptiert wird, muss die so genannte “Fremdüblichkeit” erfüllt sein.

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Basanow, Hartmut DVLV will Öffentlichkeitsarbeit deutlich ausbauen UnternehmerBrief Bauwirtschaft 4/2014 18-19 Berichte

Kurzfassung

“Tue Gutes und rede darüber” - dieses Motto will sich der Deutsche Verband für Lärmschutz an Verkehrswegen verstärkt auf seine Fahnen schreiben. Zwei Jahre erfolgreiche Arbeit liegen hinter dem Verband. Er habe es geschafft, sich als Interessensvertreter zu etablieren, stellte die Mitgliederversammlung jetzt in Kassel fest. Auf der Agenda steht insbesondere ein Ausbau der Marketingaktivitäten im Sinne der Sache.

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