Artikeldatenbank
Autor(en) | Titel | Zeitschrift | Ausgabe | Seite | Rubrik |
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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 |
KurzfassungEleven 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. x | |||||
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 |
KurzfassungThe 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. x | |||||
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 |
KurzfassungIn 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. x | |||||
Tori , Neno; Boko, Ivica; Juradin, Sandra; Baloevi , Goran | Mechanical properties of lightweight concrete after fire exposure | Structural Concrete | 6/2016 | 1071-1081 | Technical Papers |
KurzfassungThe 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. x | |||||
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 |
KurzfassungThe 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. x | |||||
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 |
KurzfassungThe 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. x | |||||
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 |
KurzfassungConcrete 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. x | |||||
Sakai, Koji; Shibata, Toshio; Kasuga, Akio; Nakamura, Hikaru | Sustainability design of concrete structures | Structural Concrete | 6/2016 | 1114-1124 | Technical Papers |
KurzfassungConcrete 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. x | |||||
Stucchi, Fernando; Ungaretti, Marcelo Coelho; Fujii, Gilson; Peiretti, Hugo Corres; Martin, José Soriano; Doniak, Sérgio | Corinthians Arena - 2014 World Cup, design and construction | Structural Concrete | 5/2016 | 698-709 | Technical Papers |
KurzfassungThis paper describes the design and construction of the concrete structures of the Corinthians Arena built for the 2014 World Cup. Due to many constraints, the structure was designed, essentially, with prefabricated structural concrete members, some specific elements were designed with structural concrete cast in situ, and some areas, with special construction problems, were designed with composite steel-concrete structures. x | |||||
Godycki- wirko, Tadeusz; Nagrodzka-Godycka, Krystyna; Wojdak, Ryszard | Reinforced concrete thin-wall dome after eighty years of operation in a marine climate environment | Structural Concrete | 5/2016 | 710-717 | Technical Papers |
KurzfassungThe paper presents a description of the construction elements of the Gdynia Seaport main hall dome. Firstly, it provides information about the technical condition of the dome's structure. Secondly, it examines the strength analysis of the thin-walled reinforced concrete dome covering. Throughout the last 80 years the building has been exposed to an unfavourable marine climate. The analysis of the state of stress and deformations of several construction elements was carried out using a special model worked out with help of the FEM considering the combination of loads: deadweight, wind and snow, as well as the additional combination: deadweight and hurricane wind of velocity 200 km/h(55.5 m/s). The computed results of static quantities were also obtained according to F. Dischinger's method, which was used in design of the RC Gdynia Seaport dome in 1932. The computational analysis and the assessment of the technical state made it possible to make a decision concerning further safe operation of the building. x | |||||
von Greve-Dierfeld, Stefanie; Gehlen, Christoph | Performance-based durability design, carbonation, part 3: PSF approach and a proposal for the revision of deemed-to-satisfy rules | Structural Concrete | 5/2016 | 718-728 | Technical Papers |
KurzfassungA performance-based safety factor durability design format is proposed and developed with respect to carbonation of concrete. Deemed-to-satisfy rules based on a partial safety factor design approach are developed for the carbonation of concrete. This design format follows the design procedure proposed in EN 1990 [1]. For the design format, the limit state equation for the carbonation is introduced in its probabilistic and safety factor format. The PSF approach has been used to derive design charts. Values for minimum concrete cover depending on material resistance and exposure class are proposed for critical environmental conditions and a design service life of 50 years. x | |||||
Qian, Chunxiang; Zhang, Yi; Huang, Haoliang; Qu, Jun; Guo, Jinqiang | Influences of superplasticizers on the basic and drying creep of concrete | Structural Concrete | 5/2016 | 729-735 | Technical Papers |
KurzfassungThe influences of naphthalene-based plasticizers and polycarboxylate acid/salt superplasticizers on the creep of concrete, including basic creep and drying creep, were investigated. The internal relative humidity and pore structure of concrete and the surface tension of the pore solution were tested. The results show that polycarboxylate acid/salt superplasticizers refine capillary pores in concrete and reduce the surface tension of the pore solution, and also restrain internal moisture transmission and redistribution. As a result, creep of the concrete is reduced. Compared with naphthalene-based plasticizer, polycarboxylate acid/salt superplasticizer causes a greater reduction of drying creep, but a smaller reduction of basic creep. This is because the moisture redistribution is quite feeble and quickly balanced in a sealed condition. Concrete with polycarboxylate acid/salt superplasticizer has the lowest creep value because polycarboxylate acid/salt superplasticizer improves the degree of hydration and reduces the porosity of macro pores. x | |||||
Daviau-Desnoyers, Dominic; Charron, Jean-Philippe; Massicotte, Bruno; Rossi, Pierre; Tailhan, Jean-Louis | Influence of reinforcement type on macrocrack propagation under sustained loading in steel fibre-reinforced concrete | Structural Concrete | 5/2016 | 736-746 | Technical Papers |
KurzfassungTo meet the growing challenges of sustainability, it is necessary to control and anticipate the cracking problems of structures under sustained loadings. At the structural level, very little information is available regarding the combined effect of SFRC and reinforcement under sustained flexural loading. This paper presents the results of four flexural creep tests on large steel fibre-reinforced concrete beams reinforced with fibres only or in combination with unbonded/bonded prestressing strands or traditional reinforcing bars. The main objective was to assess the influence of the reinforcement type on crack propagation, crack openings and compliance evolution in SFRC under sustained loading. The results show that the driving mechanism behind crack propagation is the same for all beams, regardless of reinforcement type, and is therefore governed by type of fibre concrete. x | |||||
Di Carlo, Fabio; Meda, Alberto; Rinaldi, Zila | Design procedure for precast fibre-reinforced concrete segments in tunnel lining construction | Structural Concrete | 5/2016 | 747-759 | Technical Papers |
KurzfassungThis paper presents a procedure for designing precast tunnel segments for mechanically excavated tunnel linings in fibre-reinforced concrete, without any traditional steel reinforcement. Both ultimate and serviceability limit states are considered as well as structural checks at different construction stages of the segment, including demoulding, positioning on floor, storage, transportation, handling and the final stage concerning the loads due to the ground pressure. x | |||||
Nguyen, Viet Anh; Jesse, Frank; Curbach, Manfred | Experiments to establish the loadbearing behaviour of lightweight sandwich beams using textile-reinforced and expanded polystyrene concrete | Structural Concrete | 5/2016 | 760-767 | Technical Papers |
KurzfassungTextile-reinforced concrete (TRC) is a combination of small-grain high-performance concrete (HPC) and high-strength textile reinforcement. TRC enables thin layers and has high tensile and compressive strengths. In this paper, TRC was used for the face layers and combined with a core of lightweight expanded polystyrene concrete (EPC) to create lightweight sandwich beams without special joint reinforcement to connect the layers. The experimental testing of the loadbearing behaviour of this kind of sandwich beam, along with the influence of the shear span-to-depth ratio (a/d) as observed during three- and four-point bending tests, will be summarized. The failure behaviour of the sandwich beams is influenced by the shear span-to-depth ratio, the type of bending test and the tensile capacity of the TRC layer. A diagonal tension failure occurred in experimental beams with 2.6 ≤ a/d ≤ 5.2 in three-point bending tests and 3.1 ≤ a/d ≤ 4.1 in four-point tests. The shear strength of the beams could be conservatively estimated according to the current European standards. x | |||||
Ma, Chau-Khun; Awang, Abdullah Zawawi; Garcia, Reyes; Omar, Wahid; Pilakoutas, Kypros | Behaviour of over-reinforced high-strength concrete beams confined with post-tensioned steel straps - an experimental investigation | Structural Concrete | 5/2016 | 768-777 | Technical Papers |
KurzfassungThis study examines the flexural behaviour of high-strength concrete (HSC) beams confined using an innovative steel strapping tensioning technique (SSTT) able to provide active confinement. Twelve over-reinforced HSC beams (fc &equals: 50 or 80 MPa) were designed to fail prematurely by concrete crushing at mid-span. The mid-span region of eight such beams was confined externally using the SSTT with different steel strap confinement ratios, the aim of which was to delay concrete crushing. The test results are discussed in terms of the failure modes, load-deflection response and the concrete and tensile reinforcement strains observed. Although the unconfined beams failed in a brittle manner with no post-peak deflection, the steel straps were very effective at enhancing the post-peak deformation of the SSTT-confined beams by up to 126 %. Moreover, for the beams tested in this study, the use of the SSTT led to failures after yielding of the tensile reinforcement. The proposed SSTT can be used to confine HSC elements where ductility is required. x | |||||
Yu, Qiang; Le, Jia-Liang; Hubler, Mija H.; Wendner, Roman; Cusatis, Gianluca; Ba ant, Zden k P. | Comparison of main models for size effect on shear strength of reinforced and prestressed concrete beams | Structural Concrete | 5/2016 | 778-789 | Technical Papers |
KurzfassungThis paper presents a critical comparison of the existing code provisions for the shear strength of concrete beams. The comparison is based on the computerized filtering-out of the inevitable statistical bias from the available multivariate database on shear strength, on an examination of the predicted size effects on shear strength and their underlying hypotheses and on the results of recent high-fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure in concrete beams, which is necessary for future revisions to the design code provisions. x | |||||
Yang, Yuguang; den Uijl, Joop; Walraven, Joost | Critical shear displacement theory: on the way to extending the scope of shear design and assessment for members without shear reinforcement | Structural Concrete | 5/2016 | 790-798 | Technical Papers |
KurzfassungThis paper presents a new theory for the shear capacity of reinforced concrete members without shear reinforcement. While recognizing that there are multiple failure mechanisms, the theory attributes the opening of a critical flexural shear crack as the lower bound of the shear capacity. It proposes that the shear displacement of an existing flexural crack can be used as the criterion for the unstable opening of the critical flexural shear crack. Based on the theory, the paper presents a simplified shear evaluation model. Compared with the current shear provisions in the design codes, the model is characterized by good accuracy and a solid physical background. It demonstrates a great flexibility for dealing with complex design conditions. As an example, the paper discusses the possibility of extending the theory to the shear resistance of higher-strength concrete. The suggested method provides a more logical and fluent transition from normal- to high-strength concrete and shows good agreement with experimental observations. x | |||||
Brantschen, Fabio; Faria, Duarte M.V.; Ruiz, Miguel Fernández; Muttoni, Aurelio | Bond behaviour of straight, hooked, U-shaped and headed bars in cracked concrete | Structural Concrete | 5/2016 | 799-810 | Technical Papers |
KurzfassungMost classic investigations on bonding properties in reinforced concrete have been performed on the basis of pull-out tests, where a reinforcement bar is pulled out from an uncracked concrete cylinder, prism or cube. In these tests, the bond is governed by the concrete strength and bar surface properties of the reinforcement (bond index, rib geometry) or by the splitting strength of the concrete (concrete cover). In the latter case, bond failure occurs due to uncontrolled cracking of the concrete specimen. In contrast to these fundamental tests, bond in many structural members is activated within already cracked concrete. This is particularly relevant for the reinforcement in beams and slabs (both for flexural and transverse reinforcement), as the reinforcing bars might be located at planes where flexural cracks develop. The opening of these cracks along the reinforcement is nevertheless not uncontrolled (as opposed to splitting failures), but it is governed by the bending deformations. The bond properties and strength of the reinforcement in actual members are therefore influenced by the opening of these cracks and are potentially different from those observed in classic pull-out tests. x | |||||
Figueira, Diogo; Sousa, Carlos; Calçada, Rui; Neves, Afonso Serra | Design recommendations for reinforced concrete interfaces based on statistical and probabilistic methods | Structural Concrete | 5/2016 | 811-823 | Technical Papers |
KurzfassungA concrete interface is a material discontinuity that requires special care with respect to structural design and assessment. Therefore, the definition of design expressions based on experimental testing data must ensure the necessary reliability depending on the type of structure and its use. The present work describes a new proposal for the design of concrete interfaces subjected to shear loading for different roughness profile types. The proposal is characterized by three linear branches (for monotonic loading) and an S-N curve (for cyclic loading) and is the result of a parametric analysis of existing experimental data (obtained by the authors and also from an extensive literature search) based on statistical and probabilistic methods. Design expressions were defined in order to minimize the dispersion and variability of the safety factor values for each experimental test considered and also to assure that those values are within a target range (defined according to reliability considerations). These improvements became clearer when the new proposal was compared with the most common design code recommendations. x | |||||
Villalba-Herrero, Sergi; Casas, Joan R. | New structural joint by rebar looping applied to staged box girder bridge construction. Static tests | Structural Concrete | 5/2016 | 824-835 | Technical Papers |
KurzfassungThe paper describes the design, development and experimental checking of a modified type of structural joint with limited length between concrete segments cast in-situ. The design concept is based on the developed length of an anchorage hook stiffened by transverse reinforcement bars and is particularly suited for the case of in-situ construction of staged box girder bridges, with the intention of possibly using lighter scaffolding. x | |||||
Yanaka, Makoto; Ghasemi, Seyed Hooman; Nowak, Andrzej S. | Reliability-based and life-cycle cost-oriented design recommendations for prestressed concrete bridge girders | Structural Concrete | 5/2016 | 836-847 | Technical Papers |
KurzfassungThere are several methods available to decide appropriate design recommendations to prevent corrosion of reinforcing steel in prestressed concrete bridge girders. With respect to chloride-induced corrosion, in the present study two methods are considered. The first one is based on the target probability of corrosion initiation and the initial cost. The other method is based on the life-cycle cost that includes the initial cost, maintenance cost, and expected failure cost. This paper deals with the development of recommendations for durability design of structures in marine environments from the reliability point of view, taking into consideration the life-cycle cost of a structure. In order to address the problem, the chloride diffusion coefficient of a cracked area under service load is obtained considering opening and closing motion of cracks. Utilizing the diffusion coefficient of a cracked area, the development over time of the chloride concentration at the surface of reinforcement can be predicted. This information is used to quantify the probability of initiation of corrosion of prestressing steel as well as the distribution of life-cycle cost. Based on the findings, recommendations for durability design in various exposure environments are developed. x | |||||
Colajanni, Piero; Recupero, Antonino; Spinella, Nino | Increasing the flexural capacity of RC beams using steel angles and pre-tensioned stainless steel ribbons | Structural Concrete | 5/2016 | 848-857 | Technical Papers |
KurzfassungThis article presents an experimental programme on reinforced concrete beams retrofitted with steel angles and pre-stressed stainless steel ribbons to increase their flexural strength and ductility. Two different configurations of the steel ribbon were designed, and two companion specimens for each type considered were subjected to a four-point bending test to facilitate a direct comparison in the analysis of the effectiveness of the retrofitting technique. The influence of longitudinal steel angles and transverse stainless steel ribbons is analysed, and the concrete confinement due to stainless steel ribbons examined. The strengthened beams show remarkable increments in flexural strength and ductility with respect to the as-built beam. Moreover, a simple cross-sectional model was adopted to calculate the flexural strength; then sophisticated numerical tools were used to reproduce both the experimental load-displacement curve and crack pattern for each specimen. x | |||||
Confrere, Adeline; Michel, Laurent; Ferrier, Emmanuel; Chanvillard, Gilles | Experimental behaviour and deflection of low-strength concrete beams reinforced with FRP bars | Structural Concrete | 5/2016 | 858-874 | Technical Papers |
KurzfassungThe primary objective of this new study of fibre-reinforced polymer (FRP)-reinforced concrete (RC) beams is to evaluate the mechanical performance of RC beams made of low strength concrete internally reinforced with FRP. The use of FRP rebars with low compressive strength concrete is desirable in order to avoid the accelerated corrosion processes that could occur with steel rebars. For this purpose, an experimental programme was designed to identify the failure modes and bending behaviour. The experimental results are compared with equations from ACI 440.1R-06, CSA S806-12 and other design codes as well as with other results from a review of the literature. x | |||||
Zhou, Linyun; Liu, Huangin | Response of cracked simply supported concrete beam with moving vehicle load | Structural Concrete | 5/2016 | 875-882 | Technical Papers |
KurzfassungThe dynamic response of a cracked beam subjected to moving loads has been studied extensively in the past decades. However, very little is known about the dynamic impact factors and crack propagation when vehicles move along the cracked beam. It can be reasonably postulated that a crack extension may occur when the vehicle loads cross the cracked bridge at a high speed. As a result, the dynamic response will be enlarged significantly due to the flexural rigidity reduction induced by cracks, which may result in a dangerous effect on structures. To address this problem, a three-dimensional vehicle-bridge model was developed to investigate the dynamic response of cracked bridges with crack breathing. Crack breathing is simulated at the crack surface using contact elements. The modified crack closure method is adopted to calculate the stress intensity factors. The results showed that the impact factors for the damaged bridge under a moving load could be notably larger than those for the intact bridge, and could exceed the value specified in the AASHTO bridge design code. Meanwhile, crack propagation may occur when the vehicles move along the cracked bridge at a high speed. So, it is very necessary to limit the velocity and transverse position of the vehicles to avoid further damage to the cracked bridge. x |