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Ji í ek, Pavel; Foglar, Marek Numerical analysis of a bridge pier subjected to truck impact Structural Concrete 6/2016 936-946 Technical Papers

Kurzfassung

The impact of heavy trucks on a bridge substructure can lead to progressive collapse of the bridge superstructure, and to disastrous accidents. This type of load should therefore be taken into consideration, especially in the design of motorway bridges. For some structural arrangements, vehicle impact is the decisive loading for the design of the bridge substructure. This paper presents verification of the detailed procedures given by European standard EN 1991-1-7 for bridge pier impact load - dynamic analysis, which is compared with the outcomes from a detailed finite-element model (FEM) of a truck impact prepared using AUTODYN software. A nonlinear material model of concrete with damage and strain-rate effect is used to assess the impact performance of a bridge pier. The paper further presents the results of a numerical study focused on the influence of different types of bridge pier reinforcement arrangement on their resistance to vehicle impact. The performance of various types of reinforcement is analysed and compared. Practical recommendations are drawn for the design of bridge piers which can be subjected to vehicle impacts in an urban environment.

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Jing, Yuan; Ma, Zhongguo John; Clarke, David B. Full-scale lateral impact testing of prestressed concrete girder Structural Concrete 6/2016 947-958 Technical Papers

Kurzfassung

Lateral impact damage from over-height vehicle collisions with bridge superstructures is of increasing concern in the United States. However this issue is not fully addressed in current bridge specifications. Previous researchers have conducted a number of small-scale tests to study the impact process. Also, the finite element method has largely been used to analyze the complicated collision mechanism. This paper provides an opportunity for full-scale lateral impact testing of a prestressed concrete girder, which leads to a realistic level of damage and mechanism analysis. A full-scale lateral impact testing facility was designed and built on a construction site in Knoxville, Tennessee. The over-height vehicle impact was simulated by impacting the bottom of an AASHTO Type I prestressed concrete girder with an impact cart. This paper describes the details of the impact testing facility as well as the response of the prestressed concrete girder during lateral impact. The collected test data were calibrated by using finite element software ABAQUS.

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Yekrangnia, Mohammad; Taheri, Amir; Zahrai, Seyed Mehdi Experimental and numerical evaluation of proposed precast concrete connections Structural Concrete 6/2016 959-971 Technical Papers

Kurzfassung

In this article, the cyclic performance of an innovative precast beam-to-column connection is evaluated experimentally and numerically. Two full-scale beam-column cross-shape interior connection specimens named PF-1 and PF-2 are tested. By adding extra nuts to the connecting bolts, specimen PF-2 behaves in a more shear-dominant pattern and shows less pinching. Comparison of performance of these specimens with the numerical monolithic model in terms of stiffness, strength, ductility and energy dissipation capacity indicates the proposed system can provide conditions close to the monolithic connection. However, to reduce the pinching drawback, a minor modification was made leading to performance improvements in strength and equivalent viscous damping ratio up to 51 % and 29 % respectively. The results of this study have direct industrial relevance and may be used for the development of reliable seismic guidelines for precast concrete structures.

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Lu, Xilin; Wang, Lu; Wang, Dun; Jiang, Huanjun An innovative joint connecting beam for precast concrete shear wall structures Structural Concrete 6/2016 972-986 Technical Papers

Kurzfassung

The precast shear wall structure has outstanding features for green buildings due to its construction convenience, safety, high quality and low pollution. In general, precast concrete shear walls are connected by multiple joints. The joint between precast walls has very strong influence on the whole structure, which calls for more detailed investigation. A new kind of connection - the joint connecting beam - was developed to connect the vertical reinforcement in precast concrete shear wall structures. This innovative connecting method has the advantages of convenient operation and saving steel. To evaluate the performance and for better application of the joint connecting beam, an experiment on seven full-scale specimens was conducted under cyclic loading, including two cast-in-situ walls and five precast walls with varying reinforcement and sectional heights of the joint connecting beam. A comparison was performed between cast-in-situ walls and precast walls with joint connecting beam, focusing on failure mode, hysteretic curve, skeleton curve, bearing capacity, ductility and energy-dissipating capacity. The results show that the joint connecting beam can effectively transfer the load of precast walls, especially for squat precast walls. Moreover, finite element models were developed to simulate the performance of the specimens. The simulation results agree well with experimental results.

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Marchetto, Francesco; Caldentey, Alejandro Pérez; Corres-Peiretti, Hugo Structural performance of corner joints subjected to a closing moment using mechanical anchorages: an experimental study Structural Concrete 6/2016 987-1002 Technical Papers

Kurzfassung

Keine Kurzfassung verfügbar.

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Belletti, Beatrice; Damoni, Cecilia; Cervenka, Vladimir; Hendriks, Max A.N. Catenary action effects on the structural robustness assessment of RC slab strips subjected to shear and tensile forces Structural Concrete 6/2016 1003-1016 Technical Papers

Kurzfassung

In this paper, the behaviour of RC slab strips subjected to transverse loads and axial tensile forces is investigated by means of analytical and numerical simulations. The results obtained are compared to the experimental results from tests performed at the Swiss Federal Institute of Technology (ETH). The prediction of the structural response was part of an international benchmark study [1]. The aim of the paper is to investigate the capability of the adopted models and their main influencing parameters, especially from the perspective of a reliable structural robustness assessment. It is known that in some cases axial tensile forces have a beneficial effect on the bearing capacity of slab strips, thanks to the development of catenary actions. Such hidden strength resources are usually not taken into account in the current design process. For this reason, validation of suitable numerical tools, able to properly predict the structural response, is useful for a reliable structural robustness assessment. The paper underlines the importance of benchmark development, especially for specimens, in which both mechanical and geometrical nonlinearities play an important role.

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Cladera, Antoni; Marí, Antonio; Bairán, Jesús Miguel; Ribas, Carlos; Oller, Eva; Duarte, Noemí The compression chord capacity model for the shear design and assessment of reinforced and prestressed concrete beams Structural Concrete 6/2016 1017-1032 Technical Papers

Kurzfassung

A simplified mechanical model is presented for the shear strength prediction of reinforced and prestressed concrete members with and without transverse reinforcement, with I, T or rectangular cross-section. The model, derived with further simplifications from a previous one developed by the authors, incorporates the contributions of the concrete compression chord, the cracked web, the dowel action and the shear reinforcement in a compact formulation. The mechanical character of the model provides valuable information about the physics of the problem and incorporates the most relevant parameters governing the shear strength of structural concrete members. The predictions of the model fit very well the experimental results collected in the ACI-DAfStb databases of shear tests on slender reinforced and prestressed concrete beams with and without stirrups. Due to this fact and the simplicity of the derived equations it may become a very useful tool for structural design and assessment in engineering practice.

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Qi, Jia-Nan; Ma, Zhongguo John; Wang, Jing-Quan; Liu, Tong-Xu Post-cracking shear strength and deformability of HSS-UHPFRC beams Structural Concrete 6/2016 1033-1046 Technical Papers

Kurzfassung

Eleven T-beams, reinforced with high strength steel, were tested to failure to investigate the effect of shear span to depth ratio, fibre ratio, fibre type, concrete strength and stirrup ratio on the shear behaviour, especially post-cracking shear strength and deformability, of ultra-high performance fibre reinforced concrete (UHPFRC) beams. Test results indicated that fibres were efficient not only in enhancing the post-cracking shear strength, but also in improving the post-cracking deformability of UHPFRC beams. In addition, fibres could bridge the cracks and help in redistributing and homogenizing the concrete stress beside the cracks, allowing more short fine diagonal shear cracks with small spacing to develop around the existing cracks. A moderate amount of stirrups can effectively restrain shear cracks and allow more parallel diagonal shear cracks to develop and propagate thoroughly within the shear span. The stiffness of the UHPFRC beams at ultimate state was about 50 % of initial beam stiffness, which was considerable in strength calculations and ductility analysis, especially in seismic performance evaluation. Lastly, the current shear provisions were evaluated using the experimental results.

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Wieneke, Katrin; Kueres, Dominik; Siburg, Carsten; Hegger, Josef Investigations of the punching shear behaviour of eccentrically loaded footings Structural Concrete 6/2016 1047-1058 Technical Papers

Kurzfassung

The punching shear design provisions according to various codes have been derived from the results of tests conducted on centrically loaded flat slabs. The application of these provisions for footings and ground slabs might lead to inconsistent results since more compact dimensions and soil-structure interaction lead to higher punching shear capacities. In this context, Eurocode 2 introduced a new design equation for column bases, which was derived from the evaluation of test results from centrically loaded footings.
Since centrically loaded footings represent an exception in practice, Eurocode 2 and ACI 318-14 consider load eccentricities by increasing the applied load, while the fib Model Code 2010 proposes a reduced length of the control perimeter to determine the punching shear resistance. The different approaches were derived from the evaluation of tests on eccentrically loaded flat slabs and have not been verified for footings yet.
Theoretical and experimental investigations on the punching shear behaviour of eccentrically loaded footings indicate a reduction of the multi-axial stress state along the column face with increasing load eccentricity. Based on punching tests on eccentrically loaded footings described in literature, non-linear finite-element simulations were performed and subsequently the influence of load eccentricities on the punching shear behaviour was examined in parametric studies. In this article, the results of the numerical simulations are presented and compared to experimental results and various code provisions.

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Delnavaz, Ali; Hamidnia, Mohammad Analytical investigation on shape configuration of CFRP strips on lateral loading capacity of strengthened RC shear wall Structural Concrete 6/2016 1059-1070 Technical Papers

Kurzfassung

In the past few years, the use of carbon fibre reinforced polymer (CFRP) has increased, because of their high strength, in concrete elements such as shear walls. In this study, the behaviour of a shear wall strengthened with different layout configurations of CFRP under lateral loading was investigated. For this purpose, a model is first verified in laboratory work, then in the next step the models were analysed by increasing the number of fibre layers and the effect of fibre layers on shear wall capacity was studied. Sliding between fibres and concrete was neglected. Also the effect of increasing the concrete strength of a reinforced concrete (RC) wall on CFRP strengthening was studied. In all models, comparisons were made between the results of CFRP configurations in increasing lateral strength and also ductility. Finally, by comparing the results, the best fibre configuration was determined based on the maximum load capacity.

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Tori , Neno; Boko, Ivica; Juradin, Sandra; Baloevi , Goran Mechanical properties of lightweight concrete after fire exposure Structural Concrete 6/2016 1071-1081 Technical Papers

Kurzfassung

The paper presents an experimental research project that focused on analysing the short-term residual mechanical properties of lightweight concrete after exposure to temperatures of up to 600 °C and the effects of the short-term residual mechanical properties on the post-fire loadbearing capacity of different concrete sections. The experimental programme was conducted on four different concrete mixes by determining the mechanical properties immediately after cooling and up to 96 h after cooling. The following properties were investigated: compressive strength, ultrasonic pulse velocity and stress-strain curves. The results show that the compressive strength undergoes an additional reduction in comparison to the initial residual strength (0 h property) of up to 20 % in the reference time period. A numerical study is presented at the end of the paper in order to quantify the effects of the short-term strength reduction on the axial loadbearing capacity of slender and stocky concrete columns.

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Buttignol, Thomaz Eduardo Teixeira; Colombo, Matteo; di Prisco, Marco Long-term aging effects on tensile characterization of steel fibre reinforced concrete Structural Concrete 6/2016 1082-1093 Technical Papers

Kurzfassung

The paper discusses the effect of aging on steel fibre reinforced concrete (SFRC) after 10 years. The aim is to observe the change in mechanical properties, especially of the residual post-cracking tensile strength, due to long-term aging. For this purpose, a comparison between the results of four-point bending tests (4PB) at the age of 1 year and 10 years was carried out and it indicates that aging affects the serviceability post-cracking residual strength, increasing fibre interfacial bond strength. Material classification is performed according to fib Model Code 2010 for 1-year old and 10-year old specimens. The objective is to estimate possible changes in the material class through the years. Three- and four-point bending test results on 10-year old specimens are described, together with a comparison between those tests. Both tests showed very similar results; slightly higher values were obtained with the three-point bending (3PB) test. The tensile constitutive law is obtained according to fib Model Code 2010 and is compared with results of direct tensile tests on cylindrical specimens and Double Edge Wedge Splitting tests on prismatic specimens. A plane section (PS) approach adopting the tensile constitutive law is applied to predict the bending behaviour in terms of nominal stress against crack mouth opening displacement and it is compared with the bending test results.

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Zimmermann, Thomas; Lehký, David; Strauss, Alfred Correlation among selected fracture-mechanical parameters of concrete obtained from experiments and inverse analyses Structural Concrete 6/2016 1094-1103 Technical Papers

Kurzfassung

The correlations among selected parameters of concrete were investigated for concrete mixes of the strength classes C20/25, C25/30, C30/37, C40/50 and C50/60. The focus was laid on correlations between basic mechanical parameters such as compressive strength, tensile strength and modulus of elasticity as well as parameters related to concrete fracture, represented here by specific fracture energy. Laboratory tests examining the fracture behaviour and mechanical properties were carried out in order to determine the fundamental concrete parameters. In particular, standard compression tests on test cubes and three-point bending tests on beams with central edge notch were performed. Additional material parameters were identified using the inverse analysis technique. Finally, correlation factors between different parameters of concrete were identified using the rank-order correlation method.

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Metalssi, Othman Omikrine; Kchakech, Badreddine; Lavaud, Stéphane; Godart, Bruno A new model for the analysis of the structural/mechanical performance of concrete structures affected by DEF - Case study of an existing viaduct Structural Concrete 6/2016 1104-1113 Technical Papers

Kurzfassung

Concrete construction is becoming increasingly complex and the importance of producing structures that are both cost effective and durable in the long term has never been higher. Therefore, an understanding of concrete durability is considered fundamental to determine the service life of new or existing structures. However, at present a significant number of existing concrete structures and bridges have already been deteriorated by a chemo-mechanical process known as Delayed Ettringite Formation (DEF). This phenomenon causes expansion of the affected concrete, generally leading to cracking and a decrease of its mechanical properties. The disease or deterioration mechanism therefore induces serious problems regarding serviceability, sustainable operation and structural integrity, which makes it necessary to apply predictive models able to re-assess the mechanical state of the affected structures. In this way, chemo-mechanical modelling must be performed considering the influence of humidity, stiffness reduction and stress in the development of expansion.
The elaborated 3D model was applied to an existing viaduct affected by DEF. The displacements and stresses were computed based on the experimental data obtained from the in-situ measurements. The computed results highlight the relationship between the saturation degree and the expansion. Finally, comparisons between different calculations with and without considering the anisotropy of expansion and stiffness reduction are presented and discussed.

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Sakai, Koji; Shibata, Toshio; Kasuga, Akio; Nakamura, Hikaru Sustainability design of concrete structures Structural Concrete 6/2016 1114-1124 Technical Papers

Kurzfassung

Concrete has become the most used material on Earth over the 200 years following the invention of modern cement. The design concept has undergone a transition from the allowable-stress design method, limit-state design method, to the performance-based design method, in response to the evolution of materials, sophistication of experimental facilities, and advancement of computation skills. From the issues on resources and energy depletion, global warming, and resilience etc., it is necessary to create a new design framework taking into consideration the required performance beyond the conventional concept, in order to construct infrastructure and buildings in a more rational way. In other words, we should construct a design system that sets the continued existence of the diverse and rich global environment as its most important criterion of value. In this paper, we review the design and technology system developed in the past and discuss it based on the above-mentioned new viewpoint, while constructing and presenting a new design system for concrete structures, focusing mainly on the concept of sustainability, which is regarded as the most important factor in achieving conservation of Earth's rich resources as well as sound socio-economic activities of humankind in the future, and we examine its feasibility.

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Schlicke, Dirk; Tue, Nguyen Viet Erratum to: Minimum Reinforcement of Concrete Members regarding Hardening Caused Stresses and Member Dimensions Structural Concrete 6/2016 1125 Erratum

Kurzfassung

Keine Kurzfassung verfügbar.

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2016 reviewers Structural Concrete 6/2016 1126-1127 Reviewers

Kurzfassung

Keine Kurzfassung verfügbar.

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Inhalt: UnternehmerBrief Bauwirtschaft 6/2016 UnternehmerBrief Bauwirtschaft 6/2016 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Ernst & Sohn (Hrsg.) Gesamtausgabe UBB 6/2016 UnternehmerBrief Bauwirtschaft 6/2016 1-24 Gesamtausgabe

Kurzfassung

Komplette Monatsausgabe

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Schalk, Günther Total verplant am Bau? UnternehmerBrief Bauwirtschaft 6/2016 1 Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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Kurz informiert: UnternehmerBrief Bauwirtschaft 6/2016 UnternehmerBrief Bauwirtschaft 6/2016 2 Kurz informiert

Kurzfassung

BVMB kritisiert Reform des Bauvertragsrechts
Umsätze und Aufträge im Baugewerbe weiter im Aufwind
Mehr Beschäftigte im Baugewerbe

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Meinen, Heiko Risikocontrolling praxisgerecht: Risiken erkennen und absichern UnternehmerBrief Bauwirtschaft 6/2016 3-8 Berichte

Kurzfassung

Gemeinhin ist der Bausektor als einer der risikoreichsten Wirtschaftszweige bekannt. Das zeigt schon die Branchenübersicht nach Gleißner aus dem Jahr 2002. [1] Auch aktuelle Auswertungen wie die der Creditreform zeigen, dass die Situation auch heute noch Bestand hat. Im deutschlandweiten Vergleich liegt die Insolvenzquote der Baubetriebe etwas über 1% über dem Durchschnitt des verarbeitenden Gewerbes, die bei rund 0, 55% liegt. [2] Die meisten Mittelständler befassen sich erst mit ihren Risiken, nachdem etwas passiert ist. [..] 20 bis 40 Prozent haben bisher keine richtige Strategie. [3] Diese Aussage im Zusammenhang mit dem Kreditrating macht deutlich, dass sich die Bauunternehmen in punkto Risiko einer besonderen, branchenimmanenten Situation gegenüber sehen. Der Risikoindikator der Auskunftei Creditreform liegt für den Hochbau beispielsweise rund 15% über dem Durchschnitt aller Unternehmen. Spätestens, wenn der Betrieb in Schieflage gerät und die Nachfragen der Kapitalgeber nachdrücklicher oder Kreditlinien gekündigt werden, ist die Beschäftigung mit dem Risikomanagement unumgänglich.

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Gewinnausschüttung: Wann ist der steuerliche Zuflusszeitpunkt? UnternehmerBrief Bauwirtschaft 6/2016 9 Berichte

Kurzfassung

Wird ein Handwerksbetrieb in der Rechtsform einer GmbH geführt, profitieren GmbH-Gesellschafter-Geschäftsführer nicht nur von ihrem Gehalt und Tantiemen, sondern auch von Gewinnausschüttungen der GmbH. Doch beim Zufluss solcher Gewinnausschüttungen müssen GmbH-Gesellschafter eine Besonderheit beachten, um nicht steuerliche Nachteile zu erleiden.

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Schalk, Günther Was ist neu nach der Reform des Vergaberechts? UnternehmerBrief Bauwirtschaft 6/2016 10-13 Berichte

Kurzfassung

Wer in einem Bauunternehmen oder in der Verwaltung mit der Vergabe öffentlicher (Bau-)Aufträge betraut ist, muss sich in manchen Bereichen erheblich umstellen. Seit April ist inzwischen das neue Vergaberecht in Kraft. In den Bereichen ab den EU-Schwellenwerten hat sich die Landschaft der Vorschriften umfassend geändert. Aber auch in den Bereichen unterhalb dieser magischen Vergabeschwellen gibt es Neuerungen. Die schlechte Nachricht: Die Änderungen sind damit noch nicht abgeschlossen. Für die nationalen Vergabeverfahren stehen noch weitere Neuerungen an. Die entsprechenden Gremien arbeiten bereits an einer Neufassung auch des ersten Abschnittes von Teil A der VOB. Der UBB stellt die wesentlichen Neuregelungen in einem kleinen Überblick für die tägliche Praxis vor.

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"Risiken einer Insolvenzanfechtung schwer einzuschätzen" UnternehmerBrief Bauwirtschaft 6/2016 14-15 Berichte

Kurzfassung

Der Gesamtverband der deutschen Versicherungswirtschaft (GDV) äußert auf seiner Internetseite Besorgnis über die in den letzten Jahren zu beobachtende Entwicklung der Rechtsprechung zur Insolvenzanfechtung. Unternehmen unterlägen in zunehmendem Maße einem Anfechtungsrisiko, wenn sie mit Geschäftspartnern Ratenzahlungen oder gar einen Zahlungsaufschub vereinbarten. Im UBB-Gespräch erläutert Cengiz Horn, geschäftsführender Gesellschafter beim Kreditversicherungsmakler GGW Kredit, die Bedeutung der Insolvenzanfechtung für Unternehmen, was sie tun können, um ihre Risiken möglichst gering zu halten, und wie Versicherungsbranche und Politik auf die Entwicklung reagieren.

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