Artikeldatenbank
Autor(en) | Titel | Zeitschrift | Ausgabe | Seite | Rubrik |
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fib-news: Structural Concrete 2/2015 | Structural Concrete | 2/2015 | 305-311 | fib-news | |
KurzfassungWider scope for Commission 1; A first for FRP in Ghent; Presidium meets in Lausanne; fib Bulletin 74; ‘Innovative Concretes’ in Ulm; Short notes; Congresses and symposia; Acknowledgement x | |||||
Contents: Structural Concrete 1/2015 | Structural Concrete | 1/2015 | Contents | ||
Annual table of contents 2014 | Structural Concrete | 1/2015 | Annual table of contents | ||
Müller, Harald S. | From accomplishments to challenges | Structural Concrete | 1/2015 | 1 | Message from the fib President |
Ignatiadis, Anett; Fingerloos, Frank; Hegger, Josef; Teworte, Frederik | Eurocode 2 - analysis of National Annexes | Structural Concrete | 1/2015 | 3-16 | Technical Papers |
KurzfassungEurocode 2 consists of four parts that have to be applied in conjunction with the respective National Annexes of the CEN member states. The National Annexes were introduced, in particular, to maintain national safety levels and to account for regional aspects in the different states. x | |||||
Wang, Lijie; Caspeele, Robby; Van Coile, Ruben; Taerwe, Luc | Extension of tabulated design parameters for rectangular columns exposed to fire taking into account second-order effects and various fire models | Structural Concrete | 1/2015 | 17-35 | Technical Papers |
KurzfassungFire, as one of the most severe load conditions, has an important impact on concrete structures. Not only does a fire affect the material strength, it affects structural stiffness and stability as well. A concrete column, compared with other structural members, in most cases has to cope with both vertical forces and bending moments transferred by slabs and beams. Consequently, it is essential to find a reliable and practical way of establishing interaction curves for the overall structural behaviour of concrete columns subjected to fire. In this paper, a cross-sectional calculation method based on the material models of Eurocode 2 is explained and adopted in order to calculate interaction curves for a typical rectangular column exposed to the ISO 834 standard fire. Subsequently, an iterative approach is introduced to develop interaction curves taking into account second-order effects in the case of all the four faces of a column exposed to fire. The maximum permissible slenderness ratios for columns in different fire durations are obtained and compared with Eurocode 2 provisions. Finally, this method is used to calculate the maximum permissible slenderness ratios for columns exposed to hydrocarbon and natural fires. x | |||||
Duplan, François; Abou-Chakra, Ariane; Turatsinze, Anaclet; Escadeillas, Gilles; Brûlé, Stéphane; Javelaud, Emmanuel; Massé, Frédéric | On the use of European and American building codes with low-strength mortars | Structural Concrete | 1/2015 | 36-44 | Technical Papers |
KurzfassungThe standard European building specifications, grouped in a nine-volume Eurocode, describe different approaches for determining the properties of commonly used building materials such as steel, aluminium, concrete, etc. x | |||||
Cairns, John | Bond and anchorage of embedded steel reinforcement in fib Model Code 2010 | Structural Concrete | 1/2015 | 45-55 | Technical Papers |
KurzfassungThis paper describes the changes to design provisions for embedded steel reinforcement in the fib Model Code for Concrete Structures 2010. The changes introduce new coefficients for steel grade and clear spacing between bars, and extend the range of concrete strengths covered. The way in which the contribution of hooks or anchorages is calculated has been revised and the contribution of end bearing to laps and anchorages of compression bars is recognized. The revised rules represent a move away from a distinction between laps and anchorages per se towards a distinction based on the presence or absence of transverse pressure perpendicular to the bar axis within the bond length. The benefits of staggering laps with only a proportion of bars lapped at a section are also reviewed. Finally, the potential impact of lap and anchorage performance on structural robustness is discussed, and it is concluded that this can only be achieved if bar yield precedes splitting mode bond failures. x | |||||
Prince, M. John Robert; Singh, Bhupinder | Bond behaviour of normal- and high-strength recycled aggregate concrete | Structural Concrete | 1/2015 | 56-70 | Technical Papers |
KurzfassungThe effect of concrete grade on the bond between 12 mm diameter deformed steel bars and recycled aggregate concrete (RAC) has been investigated with the help of 45 pullout tests with concentric rebar placement for coarse recycled concrete aggregate (RCA) replacement levels of 25, 50, 75 and 100%. For all the three concrete grades, the measured bond-slip relationships indicate similar mechanisms of bond resistance in the RAC and the natural aggregate (NA) concrete. The most accurate and least conservative predictions of the measured bond strengths were obtained from the local bond-slip model in the fib Model Code for Concrete Structures 2010. Bond strength normalized to fc(3/4) resulted in an improved match with test data and increased with an increase in the RCA replacement levels and decreased with an increase in compressive strength. An attempt to explain this behaviour has been sought in terms of brittleness index, an analogous parameter from rock mechanics. An empirical bond stress versus slip relationship has been proposed for the 12 mm diameter bar and it is conservatively suggested that similar anchorage lengths for this bar in all three concrete grades can be adopted for the RAC and the NA concretes. x | |||||
Mihaylov, Boyan | Five-spring model for complete shear behaviour of deep beams | Structural Concrete | 1/2015 | 71-83 | Technical Papers |
KurzfassungThis paper presents a five-spring model capable of predicting the complete pre- and post-peak shear behaviour of deep beams. The model stems from a two-parameter kinematic theory (2PKT) for the shear strength and displacement capacity of deep beams under single curvature. Four of the springs of the model represent the shear resistance mechanisms of the beam, while the fifth spring models the flexural behaviour. The model predicts not only the load-displacement response, but also the deformation patterns of the beam and how these patterns change with increasing load. Validation studies are performed by using 28 tests from the literature, showing excellent results. The model is used to interpret the tests and to draw conclusions about the behaviour of deep beams. It is shown that shear strength variations of up to 60 % between nominally identical specimens can be caused by variations in the path of the critical shear cracks. It is also demonstrated that loss of bond of large reinforcing bars increases the shear capacity of deep beams. Finally, the five-spring model is shown to predict the post-peak shear behaviour effectively, which is important for the analysis of structures under extreme loading. x | |||||
Zhou, Lin-Yun; Liu, Zhao; He, Zhi-Qi | Further investigation of transverse stresses and bursting forces in post-tensioned anchorage zones | Structural Concrete | 1/2015 | 84-92 | Technical Papers |
KurzfassungIn the post-tensioned anchorage zone, the load transfer path of an anchor force can be visualized by an infinite number of isostatic lines of compression (ILCs). The method was initially proposed by Guyon and recently attracted significant interest from a number of researchers. Based on the work of these predecessors, an updated mathematical model has been proposed in order to analyse the bursting forces and the distribution of transverse stresses in the anchorage zone. Compared with the results of a finite element analysis, the updated equations are more accurate than the previous ones. Based on the observation that the sixth-order polynomial expression is better than the fourth-order one, as far as the solution of bursting stresses is concerned, it can be reasonably postulated that a de facto function of the ILCs must exist. Additionally, it is equally interesting that the bursting forces derived with the updated analytical model are the same as those obtained with the formula in the current AASHTO-LRFD Bridge Design Specifications based on numerical stress analyses. x | |||||
Amin, Ali; Foster, Stephen J.; Muttoni, Aurelio | Derivation of the σ-w relationship for SFRC from prism bending tests | Structural Concrete | 1/2015 | 93-105 | Technical Papers |
KurzfassungThe material characterization of steel fibre-reinforced concrete (SFRC), which is required for its implementation in design codes, should be based on nominal properties that describe its post-cracking strength in tension. In the case of brittle and quasi-brittle materials, such as concrete, the tensile parameters are often derived indirectly. However, for materials with more ductility, such as SFRC, there is conjecture as to whether or not an indirect measure may be used to establish the stress versus crack opening displacement relationship, such as the use of a three- or four-point prism test combined with an inverse analysis. In this paper a simple and efficient inverse analysis technique is developed and shown to compare well with data obtained from direct tension tests. Furthermore, the methodology proposed by the fib Model Code for Concrete Structures 2010 has been investigated and recommendations made to improve its accuracy. x | |||||
Scholzen, Alexander; Chudoba, Rostislav; Hegger, Josef | Thin-walled shell structures made of textile-reinforced concrete - Part I: Structural design and construction | Structural Concrete | 1/2015 | 106-114 | Technical Papers |
KurzfassungAt RWTH Aachen University recently, a pavilion was constructed with a roof shell made of textile-reinforced concrete (TRC), a composite material consisting of a fine-grained concrete and high-strength, non-corroding textile reinforcement in the form of carbon fibres. The thin-walled TRC shell structure demonstrates impressively the loadbearing capacity of this innovative composite material. The present paper discusses the practical issues concerning the construction, such as the fabrication of the TRC shells using shotcrete, the concepts developed for the arrangement of the textile reinforcement and the erection of the shells on top of the precast concrete columns. The issues concerning the design, assessment and numerical simulation of the loadbearing behaviour of TRC shells are presented in the companion paper (Part II). x | |||||
Scholzen, Alexander; Chudoba, Rostislav; Hegger, Josef | Thin-walled shell structures made of textile-reinforced concrete - Part II: Experimental characterization, ultimate limit state assessment and numerical simulation | Structural Concrete | 1/2015 | 115-124 | Technical Papers |
KurzfassungThe present paper describes a design approach for textile-reinforced concrete (TRC) shells which reflects the interaction between normal forces and bending moments based on the cross-sectional strength characteristics of the material determined experimentally. The influence of oblique loading on the composite strength of TRC elements with flexible reinforcement is included in a normalized interaction diagram for combined loading. As an example, the design approach is applied to the ultimate limit state assessment of a TRC shell in double curvature. Furthermore, the general applicability of the design approach is discussed in the light of the non-linear loadbearing behaviour of TRC. Due to its strain-hardening tensile response, stress redistributions within the shell result in loadbearing reserves. Details of the structural design and production solutions developed and applied during the realization of the TRC shell structure are described in the companion paper (Part I). x | |||||
Jung, Bastian; Morgenthal, Guido; Xu, Dong; Schröter, Hendrik | Quality assessment of material models for reinforced concrete flexural members | Structural Concrete | 1/2015 | 125-136 | Technical Papers |
KurzfassungNon-linear constitutive models for concrete in compression are frequently defined in design codes. The engineer generally uses either the linear (in SLS) or non-linear (in ULS) compression model. However, a large variety of different approaches exists for describing the behaviour of the cracked concrete tension zone, and the selection of a corresponding model is usually based on qualitative engineering judgement. The aim of this paper is to assess the prediction quality of several concrete material models in order to provide a quantitative model selection. Therefore, uncertainty analysis is applied in order to investigate the model and parameter uncertainty in the bending stiffness prognosis for flexural members. The total uncertainty is converted into a prognosis model quality that allows a quantitative comparison between the material models considered. The consideration of the reinforced concrete in tension is based on the characterization of the tension stiffening effect, which describes the cracking in an average sense. In the interest of the practical applicability of the models considered, even for large structures, no discrete crack simulations based on fracture mechanics are considered. Finally, the assessment identifies that the prediction quality depends on the loading level and, furthermore, the quality across the models can be quantitatively similar as well as diverse. x | |||||
Holomek, Josef; Bajer, Miroslav; Barnat, Jan; Schmid, Pavel | Design of composite slabs with prepressed embossments using small-scale tests | Structural Concrete | 1/2015 | 137-148 | Technical Papers |
KurzfassungThe loadbearing capacity of steel-concrete composite slabs using thin-walled steel sheeting with prepressed embossments is in most cases determined by their resistance in longitudinal shear. The design of composite slabs still requires full-scale laboratory bending tests to be performed. Small-scale shear tests cannot include all of the influences affecting the bent slab. However, by using an appropriate procedure, the shear characteristics obtained from such tests can be used to determine the bending capacity of the slab. Two such procedures are compared in this paper. x | |||||
fib-news: Structural Concrete 1/2015 | Structural Concrete | 1/2015 | 149-157 | fib-news | |
KurzfassungThe fib in Russia: new standards; Worldwide representation at ACF 2014; DISC2014: the past and the future; Old for new: Penang Bridge; A venerable institute turns 80; JPEE2014 in Lisbon; fib MC2010 course in Brazil; Short notes; Nigel Priestley † 1943-2014; Congresses and symposia; Acknowledgement x | |||||
Contents: Structural Concrete 4/2014 | Structural Concrete | 4/2014 | Contents | ||
Glavind, Mette | Innovations in concrete for sustainable infrastructure constructions | Structural Concrete | 4/2014 | 439-440 | Editorial |
Dahl, Kaare K. B. | Bella Sky Hotel - taking precast concrete to the limit | Structural Concrete | 4/2014 | 441-447 | Technical Papers |
KurzfassungThe Bella Sky Hotel consists of two towers each leaning away from each other at an angle of 15°. The basic principle is vertical loadbearing walls with precast concrete hollow-core floor slabs. x | |||||
Clark, Gordon | Challenges for concrete in tall buildings | Structural Concrete | 4/2014 | 448-453 | Technical Papers |
KurzfassungTall buildings present unique challenges in terms of both design and construction. The definition of tall is always a matter for debate and actually is related to the proportions of the building, although the actual physical height does also result in other influences such as extreme lateral loading. x | |||||
Reinhardt, Hans-Wolf | Aspects of imposed deformation in concrete structures - a condensed overview | Structural Concrete | 4/2014 | 454-460 | Technical Papers |
KurzfassungImposed deformation is a special case of loading that gets much less attention than mechanical loading due to external forces. However, imposed deformation can impair the serviceability of structures such as tightness and durability. Imposed deformations are due to shrinkage of concrete and temperature variations. The boundary conditions play an important role when analysing stresses due to imposed deformation. This paper provides an overview. x | |||||
Theiner, Yvonne; Andreatta, Andreas; Hofstetter, Günter | Evaluation of models for estimating concrete strains due to drying shrinkage | Structural Concrete | 4/2014 | 461-468 | Technical Papers |
KurzfassungThe present contribution focuses on a comparative study of shrinkage prediction models according to the European Standard Eurocode 2 (EC2), the recommendation by ACI committee 209 and fib Model Code for Concrete Structures 2010. The estimated ultimate drying shrinkage strains and the predicted evolution of drying shrinkage strains are compared with respective shrinkage strains measured on normal-strength concrete specimens of different sizes. For all prediction models, the estimated ultimate values are found to agree quite well with the ultimate drying shrinkage strains measured on thin concrete slices. Whereas the evolution of drying shrinkage strains measured on small concrete prisms agree quite well with the predicted values, substantial differences between code values and experimental data are encountered for larger specimen sizes. x | |||||
Scott, Richard | Serviceability uncertainties in flat slabs | Structural Concrete | 4/2014 | 469-483 | Technical Papers |
KurzfassungService 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. x | |||||
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 |
KurzfassungExperiments 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. x |