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Abbasnia, Reza; Nav, Foad Mohajeri A theoretical method for calculating the compressive arch capacity of RC beams against progressive collapse Structural Concrete 1/2016 21-31 Technical Papers

Kurzfassung

Compressive arch action is one of the main resistance mechanisms against progressive collapse in reinforced concrete (RC) buildings. Hence, many studies have investigated the development of arching action in RC beams and frames but less attention has been paid to calculating the corresponding enhancement in structural capacity. In the present study, a theoretical method is introduced in order to calculate the arching capacity of RC beams and also to obtain a quantitative assessment regarding structural robustness against progressive collapse. The proposed method is validated using the experiments in the literature. The evaluation indicates that the procedure introduced here could establish a reliable foundation for estimating the arching capacity of beams and also structural robustness.

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Chin, Siew Choo; Shafiq, Nasir; Nuruddin, Muhd Fadhil Behaviour of RC beams with CFRP-strengthened openings Structural Concrete 1/2016 32-43 Technical Papers

Kurzfassung

A detailed investigation was conducted to study the behaviour of reinforced concrete (RC) beams with large openings strengthened by externally bonded carbon fibre-reinforced polymer (CFRP) laminates. A total of six simply supported beams consisting of two solid beams and four beams with openings were cast and tested under four-point bending. Each beam had a cross-section of 120 × 300 mm and length of 2000 mm. Each beam had a large opening placed symmetrically at mid-span. Test parameters included the opening shape and size as well as the strengthening configuration for the CFRP laminates. The study was conducted by way of both experimental testing and finite element analysis. The experimental results show that including a large opening at mid-span reduces the beam capacity to about 50 %. In the experimental results, strength gain due to strengthening with CFRP laminates was in the range 80-90 %. The finite element and experimental results were compared.

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Blomfors, Mattias; Engen, Morten; Plos, Mario Evaluation of safety formats for non-linear finite element analyses of statically indeterminate concrete structures subjected to different load paths Structural Concrete 1/2016 44-51 Technical Papers

Kurzfassung

To increase the efficiency of new structures and perform safety evaluations of existing structures, it is necessary to model and analyse the non-linear behaviour of reinforced concrete. The applicability of the safety formats in present design codes is unclear for indeterminate structures subjected to loading in several directions. The safety formats in fib Model Code 2010 have been evaluated for a reinforced concrete frame subjected to vertical and horizontal loading and the influence of load history studied. Basic reliability methods were used together with response surfaces to assess the failure probabilities and one safety format did not meet the intended safety level. The results indicate the importance of load history and it is concluded that more research is required regarding how load history influences the safety level of complex structures.

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Han, Sun-Jin; Lee, Deuck Hang; Cho, Sang-Heum; Ka, Soon-Beum; Kim, Kang Su Estimation of transfer lengths in precast pretensioned concrete members based on a modified thick-walled cylinder model Structural Concrete 1/2016 52-62 Technical Papers

Kurzfassung

In pretensioned concrete members, prestress is introduced by the bond mechanism between prestressing tendon and surrounding concrete. Therefore, to secure the intended level of effective prestress in the tendon, sufficient bond stresses between the prestressing tendon and the concrete should be developed at release, for which a certain length from the end of the pretensioned concrete member is required, and this required distance is defined as the transfer length of the prestressing tendon. In this study, the prestress introduction mechanism between concrete and prestressing tendon was mathematically formulated based on thick-walled cylinder theory (TWCT). On this basis, an analytical model for estimating the transfer length was presented. The proposed model was also verified through comparison with test results collected from the literature. It was confirmed that the proposed model can accurately evaluate the effects of influential factors - such as diameter of prestressing tendon, compressive strength of concrete, concrete cover thickness and magnitude of initial prestress - on the transfer lengths of prestressing tendons in various types of pretensioned concrete member.

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Claßen, Martin; Gallwoszus, Joerg Concrete fatigue in composite dowels Structural Concrete 1/2016 63-73 Technical Papers

Kurzfassung

In modern bridge construction, steel-concrete composite structures with composite dowels are being built more than ever, especially for small and medium spans. In contrast to headed studs, in which initial steel cracks occur after only a few load cycles [1], [2], the lifetime of composite dowels is characterized by the compression of the multi-axially stressed concrete in front of the composite dowel. Here, plastic compression strains occur in the concrete and accumulate over load cycles, leading to a cyclic increase in relative displacements in the connection. Certain proportions of these relative displacements, called inelastic slip, remain in the connection, even after the loading is relieved. The inelastic slip changes the characteristics of the static dowel curve. The initially rigid connection degrades over its lifetime, leading to redistributions of internal forces, which may be critical for fatigue design. In order to consider the degradation of the composite connection, a cyclic dowel curve can be used, which may be developed from the static dowel curve by introducing the inelastic slip. This paper presents the results of cyclic shear tests on different composite dowel geometries. The effect of load-dependent parameters (upper load level and load range) was investigated. Furthermore, an engineering model for determining the cyclic dowel curve is presented, which was developed based on the results of experimental and numerical investigations.

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Na, Okpin; Xi, Yunping; Ou, Edward; Saouma, Victor E. The effects of alkali-silica reaction on the mechanical properties of concretes with three different types of reactive aggregate Structural Concrete 1/2016 74-83 Technical Papers

Kurzfassung

This paper investigates the degradation of the mechanical properties of concretes made with three types of aggregate affected by alkali-silica reaction (ASR). Three standard testing methods - ASTM C289, JASS 5N T-603 and ASTM C1260 - were used to identify the reactivity of ASR of the three aggregates selected. The test results show that all three aggregates are potentially deleterious. A new acceleration method based on JASS 5N T-603 and ASTM C1260 was proposed for concrete specimens. In the acceleration method, cylindrical concrete specimens were used, additional alkali material was added to the concrete mixture and the specimens were stored under conditions similar to ASTM C1260. The preconditioned concrete specimens were then used for evaluating the mechanical properties of the ASR-affected concrete in terms of strength and stiffness. The test results show that special attention must be paid to the effects of two opposing mechanisms on the strength and stiffness of concrete: hydration reactions and ASR. Hydration reactions enhance the mechanical properties, whereas ASR does the opposite. The changes in length of concrete specimens were also measured, which showed that the basic trends for change in length and mechanical properties may be different. It is better to examine the effect of ASR on both change in length and mechanical properties. The size and reactivity of the aggregate are very important factors for the mechanical properties of ASR-affected concretes. Within the two-month testing period, the reactive fine aggregate might cause ASR expansion and the reactive coarse aggregates might not.

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Matos, Ana Mafalda; Sousa-Coutinho, Joana ASR and sulphate performance of mortar containing industrial waste Structural Concrete 1/2016 84-95 Technical Papers

Kurzfassung

“Greener” concrete using adequate industrial waste is a preferred option for sustainable construction. Alkali-silica reaction (ASR) and sulphate attack (SA) on concrete can be minimized by the use of mineral additions, which are particularly interesting if derived from waste. Grits from the paper industry, waste glass and two types of biomass ash were used as 10 % cement replacement in mortar and tested for ASR and SA. Results and scanning electron microscopy observations were compared with plain mortar and mortar containing commercial silica fume. All waste materials mitigated ASR compared with the control mortar. Resistance to sulphates was increased for one of the biomass ashes used and especially for glass powder, which surpassed silica fume. Therefore, two of these waste materials seem to be promising as partial replacement materials for cement, leading to enhanced durability and thus contributing to sustainable construction.

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Qian, Chunxiang; Nie, Yanfeng; Cao, Tianji Sulphate attack-induced damage and micro-mechanical properties of concrete characterized by nano-indentation coupled with X-ray computed tomography Structural Concrete 1/2016 96-104 Technical Papers

Kurzfassung

Sulphate attack is a serious problem for concrete in marine environments. Sulphate attack can change the composition and microstructure of concrete and eventually influence the mechanical and durability performance. In this paper, the heterogeneity and mechanical properties of concrete exposed to sulphate is investigated from the microscopic to the mesoscopic scale. X-ray computed tomography (XCT) and nano-indentation were adopted to define the defect zone and establish the relationship between interfacial transition zone (ITZ) and concrete matrix (mortar). The experiments were based on concrete and mortar specimens of different strengths. The results of XCT have nano-indentation indicate that the specimens had similar degrees of damage regionally and good correlation exists between the elastic moduli of the ITZ and the mortar. The concrete can be partitioned into three parts: the cracked zone with heavy damage, damaged zone and undamaged zone. The elastic modulus of the mortar phase and the ITZ has a linear relation.

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Kulovaná, Tereza; Vejmelková, Eva; Keppert, Martin; Rovnaníková, Pavla; Ker ner, Zbyn k; erný, Robert Mechanical, durability and hygrothermal properties of concrete produced using Portland cement-ceramic powder blends Structural Concrete 1/2016 105-115 Technical Papers

Kurzfassung

Blended Portland cement-ceramic powder binder containing up to 60 % fine-ground waste ceramics from a brick factory is used in concrete mix design as an environmentally friendly alternative to the commonly used Portland cement. The experimental analysis of basic physical characteristics, mechanical and fracture-mechanical properties, durability properties and hygrothermal characteristics shows that the optimal amount of ceramic powder in the mix is 20 % of the mass of blended cement. The decisive parameters in that respect are compressive strength, liquid water transport parameters and resistance to de-icing salts, which are not satisfactory for higher ceramics dosage in the blends. In the case of other parameters studied, the limits for the effective use of ceramic powder are higher: 40 % for effective fracture toughness and specific fracture energy, 60 % for frost resistance and chemical resistance to MgCl2, NH4Cl, Na2SO4, HCl and CO2. The water vapour diffusion coefficient is found to increase with increasing ceramics content, which for wet envelopes can be considered as a positive feature, but may have a negative effect for dry envelopes. The thermal conductivity of all mixes increases fast with growing moisture content; differences of up to 50 % between the dry and water-saturated state values are observed. This has to be taken into account in energy-related calculations.

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Shaikh, Faiz Effect of ultrafine fly ash on the properties of concretes containing construction and demolition wastes as coarse aggregates Structural Concrete 1/2016 116-122 Technical Papers

Kurzfassung

This paper presents the preliminary results of the effect of ultrafine fly ash (UFFA) on the properties of concretes containing recycled coarse aggregates (RCA) originating from construction and demolition (C&D) wastes. The effect of 10 % UFFA on the compressive strength, tensile strength, sorptivity and chloride ion permeability of concretes containing 25 and 50 % RCA is evaluated at 7, 28 and 56 days. The addition of UFFA increased the compressive strength of recycled aggregate concretes at all ages up to 56 days. However, a slight reduction in the tensile strength of recycled aggregate concretes was observed. Concrete containing 25 % RCA and 10 % UFFA achieved 94 % of the control concrete's compressive strength at 56 days. In both recycled aggregate concretes tested, the sorptivity and chloride ion permeability are much lower at all ages due to the addition of 10 % UFFA. This is because it serves to promote hydration and block the large capillary pores within the concrete.

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fib-news: Structural Concrete 1/2016 Structural Concrete 1/2016 125-131 fib-news

Kurzfassung

fib MC2020: The story so far
New fib SG
fib-ACI MoC
Betontage inShanghai
COM4: Materials-related priorities
4th IWCS
Ralejs Tepfers 1933-2015
Gabriel Tevec 1936-2016
Congresses and symposia
Acknowledgement

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Inhalt: UnternehmerBrief Bauwirtschaft 1/2016 UnternehmerBrief Bauwirtschaft 1/2016 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Jahresinhaltsverzeichnis des 38. Jahrgangs 2015 UnternehmerBrief Bauwirtschaft 1/2016 Jahresinhaltsverzeichnis

Kurzfassung

Keine Kurzfassung verfügbar.

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Ernst & Sohn (Hrsg.) Gesamtausgabe UBB 1/2016 UnternehmerBrief Bauwirtschaft 1/2016 1-24 Gesamtausgabe

Kurzfassung

Komplette Monatsausgabe

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Schalk, Günther Wenn der Bürger entscheidet... UnternehmerBrief Bauwirtschaft 1/2016 1 Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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Kurz informiert: UnternehmerBrief Bauwirtschaft 12/2016 UnternehmerBrief Bauwirtschaft 1/2016 2 Kurz informiert

Kurzfassung

Der alljährliche Blick in die Kristallkugel
Projekt Zununftssicherung

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Leupertz, Stefan Streitbeilegung in Bausachen ohne Hilfe des Gerichts UnternehmerBrief Bauwirtschaft 1/2016 3-7 Berichte

Kurzfassung

Bauprozesse sind zeitaufwändig und schwerfällig.Weil sie zudem in aller Regel erst beginnen, wenn die Baumaßnahme abgeschlossen ist, liegen zwischen der Entstehung eines bauvertraglichen Streits und seiner gerichtlichen Bescheidung oft Jahre, bei größeren Prozessen über mehrere Instanzen nichtselten sogar eine Dekade und mehr. Solche Verfahren binden in erheblichem Umfang Zeit und - bei gewerblich tätigen Parteien - Personal; die dadurch bedingten Transaktionskosten sind enorm und rasch höher als der Ertrag aus einem (regelmäßig nur teilweise) erfolgreich geführten Bauprozess.

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Bundesverkehrsminister Dobrindt hält Festrede bei der BVMB UnternehmerBrief Bauwirtschaft 1/2016 8 Berichte

Kurzfassung

Bald ist es wieder soweit: Der traditionelle Tag der mittelständischen Bauwirtschaft inklusive Neujahrsempfang der Bundesvereinigung Mittelständischer Bauunternehmen e.V. (BVMB) findet in diesem Jahr am 15. Februar 2016 - wie seit Jahrzehnten üblich - in Bonn statt. Hier treffen sich alljährlich die “Macher und Entscheider” aus dem Bau-Mittelstand zum Erfahrungsaustausch mit Politik, Verwaltung und Auftraggeberseite aus ganz Deutschland. Bundesverkehrsminister Alexander Dobrindt hat bereits seine Teilnahme zugesagt und wird die Festrede halten.

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Wie sieht "barrierefrei" aus? UnternehmerBrief Bauwirtschaft 1/2016 8 Berichte

Kurzfassung

Wie sieht eine Stadt-, Quartiers- und Verkehrsentwicklung unter Berücksichtigung barrierefreier Aspekte aus? Dieser Frage gingen Experten bei einem “Zukunftsforum” im hessischen Friedberg nach. Die Anforderungen an einen barrierefreien Alltag mit planerischen und baulichen Konzepten zur Standort- und Raumplanung sind hoch und stellen die Beteiligten vor große Herausforderungen.

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Schalk, Günther Aktuelles aus der Rechtsprechung UnternehmerBrief Bauwirtschaft 1/2016 9-10 Berichte

Kurzfassung

Keine Kurzfassung verfügbar.

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Neue Rechenregeln zur Pauschwertberichtigung UnternehmerBrief Bauwirtschaft 1/2016 11 Berichte

Kurzfassung

Ein kritischer Blick des Betriebsprüfers des Finanzamts gilt meist den bilanzierten Forderungen eines Bauunternehmens. Insbesondere die Pauschalwertberichtigung dürfte nach einem Infoschreiben der Finanzverwaltung ins Visier der Prüfer rücken.

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Behandlung von Arbeitslohnspende bei Minijobbern UnternehmerBrief Bauwirtschaft 1/2016 11-12 Berichte

Kurzfassung

Vereinbaren ein Arbeitgeber und ein Minijobber eine Arbeitslohnspende für Flüchtlinge, stellt sich in der Praxis die Frage, wie diese Spende sozialversicherungsrechtlich und steuerlich zu behandeln ist. Die Antwort kommt von der Minijobzentrale.

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Dienstwagenbesteuerung bei Leasing-Sonderzahlung UnternehmerBrief Bauwirtschaft 1/2016 12 Berichte

Kurzfassung

Bekommt ein Arbeitnehmer einen Dienstwagen zur Verfügung gestellt, muss für die Privatfahrten ein geldwerter Vorteil versteuert werden. Kompliziert wurde es bei der Ermittlung dieses Privatanteils immer dann, wenn für den Dienstwagen ein Fahrtenbuch geführt wurde und der Dienstwagen geleast wurde.

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Malkwitz, Alexander; Ehlers, Johann Prozessoptimierung im Tunnelbau am Beispiel des Emscherumbaus UnternehmerBrief Bauwirtschaft 1/2016 13-16 Berichte

Kurzfassung

Der Emscherumbau, das Generationenprojekt der Emschergenossenschaft, soll bis 2020 fertiggestellt werden. Der Umbau des Abwasserkanals in ein unterirdisches Abwassersystem von insgesamt 51 km Länge in einer Tiefe von bis zu 40 Metern steht im Vordergrund des Projekts. Dieser Artikel beschreibt anhand eines Bauabschnitts den Tunnelvortrieb und die Möglichkeiten diesen, am Beispiel des Rohrwechsels, zu optimieren.

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Vergaberecht aktuell UnternehmerBrief Bauwirtschaft 1/2016 17-18 Berichte

Kurzfassung

Keine Kurzfassung verfügbar.

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