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Nyhus, Bente Skovseth Consistent practical design of concrete structures Structural Concrete 3/2014 305-316 Technical Papers

Kurzfassung

The design of large concrete structures is a very complex area which requires specialized skills and specialized tools. Tools are available to design these structures efficiently. However, these design tools are based on inconsistency between what is assumed in the structural analysis and the sectional design. This inconsistency is believed to be conservative, but is such an approach always safe and cost-effective? In light of this, a design tool has been developed to eliminate this inconsistency. The program is called ShellDesign and the new method is called the “consistent stiffness method”. The method can be used in practical design and is a more efficient alternative to running non-linear analysis programs. In order to obtain a more rational and consistent design method for transverse shear, implementation of the modified compression field theory (MCFT) in ShellDesign is almost finished. The main advantages of developing ShellDesign are to increase the competitiveness of concrete structures, contribute to increased safety and also to increase operability and document robustness in existing structures.

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Belletti, Beatrice; Damoni, Cecilia; Hendriks, Max A. N.; de Boer, Ane Analytical and numerical evaluation of the design shear resistance of reinforced concrete slabs Structural Concrete 3/2014 317-330 Technical Papers

Kurzfassung

The aim of this research is to compare the predictions of the design load-carrying capacity of slabs obtained with simplified analytical and numerical procedures which can be readily used by analysts in the current design process. The research fits into a research programme initiated by the Dutch Ministry of Infrastructure and the Environment for the re-examination of the load-carrying capacity of existing bridges and viaducts, and the beams and slabs they include, through the use of non-linear finite-element analyses. The behaviour of reinforced concrete slabs subjected to concentrated loads close to their supports is investigated in this contribution. Three tests from a series of 18 slabs with a total of 108 tests, tested at Delft University of Technology, were selected as case studies and analysed with non-linear finite-element analyses and analytical models either proposed by design codes or available in the literature. The research agrees well with the philosophy of the fib Model Code for Concrete Structures 2010, which offers different analytical and numerical calculation methods for evaluating the design shear resistance of reinforced concrete members according to different levels of approximation. For the three slabs investigated in this study, it indeed pays to use higher levels of approximation. The highest level (level IV) based on non-linear finite element analysis gives the highest design load resistance, but still well below the resistance obtained experimentally.

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Siburg, Carsten; Hegger, Josef Experimental investigations on the punching behaviour of reinforced concrete footings with structural dimensions Structural Concrete 3/2014 331-339 Technical Papers

Kurzfassung

Punching tests on 13 specimens under uniform soil pressure were conducted to evaluate the punching shear behaviour of footings with practical dimensions. The test series included square footings with and without punching shear reinforcement. The dimensions of the footings varied between 1.20 × 1.20 m and 2.70 × 2.70 m and the slab thickness varied between 0.45 and 0.65 m, resulting in shear span-depth ratios a&lgr;/d between approx. 1.25 and 2.00.
In addition to the measured steel strains in the flexural reinforcement and the stirrups, the increase in the slab thickness as well as the saw-cuts were examined to investigate the internal cracking and failure characteristic. In combination with previous tests conducted at RWTH Aachen University, this test series permits a description of the effect of the main parameters on the punching shear strength of footings. These parameters are the size effect of the effective depth, the concrete compressive strength, the flexural reinforcement ratio and the punching shear reinforcement.

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Gupta, Pramod K.; Ahuja, Ashok K.; Khaudhair, Ziyad A. Modelling, verification and investigation of behaviour of circular CFST columns Structural Concrete 3/2014 340-349 Technical Papers

Kurzfassung

This paper is an attempt to provide a detailed procedure for the finite element modelling and simulation of concrete-filled steel tubular (CFST) columns subjected to axial compression using the commercial software package ANSYS 12. A modified material model for modelling the concrete core is described and explained. Composite action is modelled between the concrete core and the steel tube and the procedure is presented with the recommended properties for modelling such behaviour. The proposed model is then validated by comparing its numerical results with selected experimental results available in the literature. The proposed model is used to investigate numerically the load transfer mechanism of CFST columns filled with different grades of concrete in order to study the effect of this parameter - i.e. compressive strength of concrete core - on the load transfer mechanism in such columns. Further, the proposed model has been employed for investigating the confining pressure provided by the steel tube on the concrete core along the length of the CFST column.

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Won, Deok Hee; Park, Woo Sun; Yi, Jin-Hak; Han, Sang-Hun; Han, Taek Hee Effect of welding heat on precast steel composite hollow columns Structural Concrete 3/2014 350-360 Technical Papers

Kurzfassung

Steel composite hollow columns have been studied in order to ease their construction. Welding or bolting are mostly used for connecting the steel tubes of precast steel composite hollow columns. However, welding generally results in temperatures of about 20000 °C in the welding zone and 1300 °C around the welding zone. Thus, the strength of the concrete in regions close to a welding zone is reduced. In this paper, the effects of arc welding and electro-slag welding - two widely used methods for connecting the column modules of steel composite hollow columns - on the temperature change in the welding zone are studied by performing heat transfer analysis. The changes in the strength of the concrete are investigated for each welding method. The rate of decrease in concrete strength due to electro-slag welding was greater than that due to arc welding. In addition, an effective method using ceramic fibres is suggested for preventing strength reduction in concrete due to welding heat.

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Carpinteri, Alberto; Cadamuro, Erica; Corrado, Mauro Minimum flexural reinforcement in rectangular and T-section concrete beams Structural Concrete 3/2014 361-372 Technical Papers

Kurzfassung

The prescriptions provided by codes of practice for assessing the minimum reinforcement amount for strength purposes in reinforced concrete beams usually disregard the non-linear contribution of concrete in tension and size-scale effects. In the present paper, these phenomena are taken into account correctly in the description of the flexural failure in lightly reinforced concrete beams by means of a numerical algorithm based on non-linear fracture mechanics. In this context, the application of dimensional analysis permits a reduction in the number of governing parameters. In particular, it is demonstrated analytically that only two dimensionless parameters, referred to as reinforcement brittleness number and stress brittleness number, are responsible for the brittle-to-ductile transition in the mechanical response. According to this approach, new formulae suitable for evaluating the minimum reinforcement in practical applications is proposed for both rectangular and T-sections. A comparison with experimental results demonstrates the effectiveness of the proposed model for different reinforcement percentages and beam depths.

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Castel, Arnaud; Gilbert, Raymond Ian Influence of time-dependent effects on the crack spacing in reinforced concrete beams Structural Concrete 3/2014 373-379 Technical Papers

Kurzfassung

This paper aims to put into perspective the influence of long-term effects, such as concrete creep and shrinkage, on concrete cracking. Long-term experimental results obtained at the Centre for Infrastructure Engineering & Safety (CIES) are reported and compared to design estimates made using the fib Model Code for Concrete Structures 2010. The influence of factors such as stirrup spacing and concrete cover are discussed. Results show that time-dependent shrinkage-induced cracking can considerably modify the cracking patterns obtained in short-term tests. For crack control in real structures and for the development of models for inclusion in codes of practice, it is strongly recommended that account be taken of time-dependent effects. Limiting observations to those made in short-term tests may lead to erroneous conclusions that are simply not applicable for structures that are more than a few weeks old.

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Strauss, Alfred; Zimmermann, Thomas; Lehký, David; Novák, Drahomír; Ker ner, Zbyn k Stochastic fracture-mechanical parameters for the performance-based design of concrete structures Structural Concrete 3/2014 380-394 Technical Papers

Kurzfassung

The experimental results for quasi-brittle materials such as concrete and fibre-reinforced concrete exhibit high variability due to the heterogeneity of their aggregates, additives and general composition. An accurate assessment of the fracture-mechanical parameters of such materials (e.g. compressive strength fc and specific fracture energy Gf) turns out to be much more difficult and problematic than for other engineering materials. The practical design of quasi-brittle material-based structures requires virtual statistical approaches, simulations and probabilistic assessment procedures in order to be able to characterize the variability of these materials. A key parameter of non-linear fracture mechanics modelling is the specific fracture energy Gf and its variability, which has been a research subject for numerous authors although we will mention only [1, 2] at this point. The aim of this contribution is the characterization of stochastic fracture-mechanical properties of four specific, frequently used classes of concrete on the basis of a comprehensive experimental testing programme.

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Van Coile, Ruben; Caspeele, Robby; Taerwe, Luc Towards a reliability-based post-fire assessment method for concrete slabs incorporating information from inspection Structural Concrete 3/2014 395-407 Technical Papers

Kurzfassung

After a concrete structure has been exposed to fire, a combination of destructive and non-destructive testing, expert judgment and calculations is used to decide whether the structure should be demolished or repaired, or can continue to be used without repairs or rehabilitation. However, there are many uncertainties associated with both the fire duration and the effect of elevated temperatures on the residual mechanical properties of the materials. Consequently, the maximum service load after fire exposure should be assessed based on reliability considerations in order to provide an adequate level of safety. As this type of calculation is too complex and time-consuming for practical use, a reliability-based assessment tool has been developed for concrete structures and applied to slabs to determine the maximum service load after fire. When using the proposed method, a safety level is targeted which is comparable with the safety level associated with the Eurocode format for the design of new structures. It is concluded that the proposed assessment method is both user-friendly and directly applicable in practice.

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Mancini, Giuseppe; Tondolo, Francesco Effect of bond degradation due to corrosion - a literature survey Structural Concrete 3/2014 408-418 Technical Papers

Kurzfassung

Bond can play an important role in the assessment of existing structures, particularly when corrosion of reinforcement is to be expected. The results of bond tests on corroded bars embedded in concrete are not yet fully conclusive for the definition of bond degradation due to the effect of corroded reinforcement. The structural effects of bond degradation can assume a different importance following the resisting mechanism that is activated within the structure. A critical review of the data available is presented here; some aspects such as embedment length, corrosion rate and type of test are analysed.

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Wilhelm, Sebastian; Curbach, Manfred Review of possible mineral materials and production techniques for a building material on the moon Structural Concrete 3/2014 419-428 Technical Papers

Kurzfassung

This article provides an overview of the findings and production processes for the mineral materials that have been developed and tested worldwide in the past with regard to the establishment of a lunar base. Firstly, the aim of and procedure for constructing a lunar base are briefly outlined. Following that, the lunar environment factors and their influence on a possible structure are described. The paper then presents the advantages and disadvantages of the materials examined, such as sulphur concrete, cast basalt, lunar concrete or polymer concrete, on the one hand, as well as production processes investigated previously, such as sintering, geothermite reaction and 3D printing, on the other. One promising method is the dry-mix/steam-injection (DMSI) method for producing a lunar concrete as a possible material which was developed by T. D. Lin and is based on cement made from lunar resources.

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fib-news: Structural Concrete 3/2014 Structural Concrete 3/2014 429-437 fib-news

Kurzfassung

AAYE: award opportunity for young engineers; First fib PhD Symposium held in North America; International conference in Moscow attracts renowned specialists; Innovation in Oslo; NZCS: New Zealand's member group; Structural Concrete impact factor on the rise; fib Bulletin 72; Montreal: the state-of-the-art in FRC; Short notes; EWH Gifford † 1921-2014; Congresses and symposia; Acknowledgement

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Inhalt: UnternehmerBrief Bauwirtschaft 3/2014 UnternehmerBrief Bauwirtschaft 3/2014 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Schalk, Günther "Ich habe leider keine Rose für Dich..."?! UnternehmerBrief Bauwirtschaft 3/2014 1 Editorial

Kurzfassung

Keine Kurzfassung verfügbar.

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Kurz informiert: UnternehmerBrief Bauwirtschaft 3/2014 UnternehmerBrief Bauwirtschaft 3/2014 2 Kurz informiert

Kurzfassung

Schwarzarbeit sorgt für dunkle Wolken am Bauhimmel
Es geht weiter vorsichtig bergauf am Bau
EU erleichtert Kapitalbeschaffung für Mittelständler

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Gebbeken, Norbert Ein Plädoyer für eine nachhaltige Bauingenieurausbildung UnternehmerBrief Bauwirtschaft 3/2014 3-10 Berichte

Kurzfassung

Bauen kann man - theoretisch - überall. Es braucht, anders als zum Beispiel in der Landwirtschaft, keine speziellen Standortfaktoren. Dafür aber fachkundige Ingenieure, und die wachsen nicht an Bäumen. Die deutsche Ingenieurausbildung war seit rund 200 Jahren weltweit führend. Aber ist sie das heute auch noch? Seit rund zehn Jahren wird die deutsche Ingenieursausbildung ohne wirkliche Not zerschlagen und dem “Mainstream” angepasst. Unser Autor, selbst Hochschulprofessor, sieht diese Entwicklung sehr kritisch. Er spricht von “Entwissenschaftlichung”, beschreibt Gefahren durch allzu frühe Spezialisierung an Hochschulen und plädiert engagiert für mehr Nachhaltigkeit in der Ausbildung künftiger Bauingenieure.

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Englert, Florian; Schalk, Günther Aktuelles aus der Rechtsprechung UnternehmerBrief Bauwirtschaft 3/2014 11-12 Berichte

Kurzfassung

Doppelte Zahlung & Verjährung..
Verjährung Teil II: Wann hemmen Verhandlungen?
Verjährung, die dritte: Mängel arglistig verschwiegen?

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Berichtigung der Umsatzsteuer auf Sicherheitseinbehalte UnternehmerBrief Bauwirtschaft 3/2014 13-14 Berichte

Kurzfassung

In einem Überraschungsurteil kippt der Bundesfinanzhof die Ungerechtigkeit, wonach Baufirmen trotz Sicherheitseinbehalten durch Auftraggeber die volle Umsatzsteuer aus der Schlussrechnung ans Finanzamt abführen müssen. Der UBB gibt wichtige Infos, wie Bauunternehmer nun vorgehen sollten.

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Vergaberecht aktuell UnternehmerBrief Bauwirtschaft 3/2014 15-16 Berichte

Kurzfassung

Keine Nebenangebote, wenn Preis einziges Kriterium
Wann sind Bietergemeinschaften zulässig?

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Rote Karte für automatische Vorsteuerkürzung UnternehmerBrief Bauwirtschaft 3/2014 17 Berichte

Kurzfassung

Fischt der Prüfer des Finanzamts eine Eingangsrechnung aus der Buchhaltung eines Bauunternehmers und stellt fest, dass der Rechnungsaussteller gar kein Unternehmer war oder dass er eine falsche Adresse angegeben hat, war der Vorsteuerabzug bisher verloren. Die Betonung liegt hier jedoch auf dem Wörtchen “war”: Denn die Richter des Finanzgerichts (FG) Münster zeigten dem Finanzamt nun die rote Karte. Konnte der Rechnungsempfänger nicht erkennen, dass er einem betrügerischen Rechnungsaussteller aufgesessen ist, darf an dem Vorsteuerabzug nachträglich nicht gerüttelt werden (FG Münster, Beschluss v. 12.12.2013, Az. 5 V 1934/13 U).

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Bender, Burkhard; Held, Franz Wie lässt sich Haftung des GmbH-Geschäftsführers vermeiden? UnternehmerBrief Bauwirtschaft 3/2014 18 Berichte

Kurzfassung

Die zivilrechtliche und strafrechtliche Verantwortlichkeit eines GmbH-Geschäftsführers oder Vorstandes einer AG ist schon für den ausgebildeten Juristen schwer zu überblicken, erst recht für den Betroffenen. Die Realisierung von Baumaßnahmen aller Art ist ohnehin risikobehaftet und haftungsträchtig. Eine deliktische Eigenhaftung kann sich aus dem Gesellschaftsrecht (Geschäftsführerhaftung), Strafrecht (deliktische Eigenhaftung bei Schutzgesetzverletzung), Steuerrecht, Insolvenzrecht, dem allgemeinen Zivilrecht (Verletzung von Verkehrssicherungspflichten) und Spezialvorschriften wie z.B. dem Bauforderungssicherungsgesetz ergeben.

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Steuervergünstigung nur für typische Berufskleidung UnternehmerBrief Bauwirtschaft 3/2014 19 Berichte

Kurzfassung

Ein selbstständiger Handwerker, der bei der Arbeit einen Blaumann, einen hygienischen Kittel oder spezielle Schuhe mit Stahlkappen benötigt, kann die Kosten dafür als Betriebsausgaben von seinem Gewinn abziehen. Bei Benutzung “bürgerlicher Kleidung” schalten Finanzamt und Bundesfinanzhof dagegen auf Stur.

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Positiv-Urteil: Keine Doppelbestrafung bei Darlehensausfall UnternehmerBrief Bauwirtschaft 3/2014 19 Berichte

Kurzfassung

Leiht sich ein Gesellschafter von seiner GmbH Geld, weil er von der Bank keinen Kredit mehr bekommt, ruft ein solches Darlehen den Betriebsprüfer auf den Plan. Denn: Werden keine Sicherheiten vereinbart, und das Darlehen fällt wegen Zahlungsunfähigkeit des Gesellschafters aus, liegt eine verdeckte Gewinnausschüttung vor.

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Schalk, Günther Bauen und Prozesse managen UnternehmerBrief Bauwirtschaft 3/2014 20 Buchtipp

Kurzfassung

Keine Kurzfassung verfügbar.

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UBB-Veranstaltungstipps UnternehmerBrief Bauwirtschaft 3/2014 20 Veranstaltungen

Kurzfassung

Keine Kurzfassung verfügbar.

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