bluuebunny/crossref_metadata_2025_split huggingface dataset:
History and overview of fabric formwork: using fabrics for concrete casting
Authors: Veenendaal Diederik , West Mark , Block Philippe 
Published: October 2013

AbstractThe concept of casting concrete in fabrics, fabric formwork technology, has resurfaced at various times and in different forms throughout the past century. The following paper traces developments that have used fabrics for concrete formwork, including different types of flexible formwork, controlled permeability formwork and pneumatic formwork. This paper presents a comprehensive historical overview of fabric formwork, listing key innovators, technological developments and their advantages, and offering examples of structures built with these methods. The information gathered is used to present a taxonomy of these related formwork technologies as well as a formal definition of the term “fabric formwork” that encompasses them. The paper is intended to introduce readers to these technologies and offer readers already familiar with these methods additional historical background.
Effects of cross‐sectional shape on the reliability of RC columns
Authors: Baji Hassan , Ronagh Hamid R. 
Published: October 2013

AbstractThis paper studies the effects of cross‐sectional shape and rebar configuration on the reliability indices of concrete columns. Three sections with rectangular, square and circular shapes are selected. Using the Monte Carlo simulation technique, the statistical parameters for reinforced column resistance are calculated along several load eccentricities using the most recent statistical data available in the literature. The statistical parameters show that the magnitude and the variation of bias factors and the coefficients of variation are not similar for the sections selected. The coefficients of variation of the square and circular sections are greater than that of the rectangular section. The results of reliability analysis indicate the importance of sectional shape, especially at low load eccentricities. In some cases, the effect of cross‐sectional shape or reinforcement configuration is found to be more important than the effect of the compressive strength of the concrete. It is recommended to include the shape factor and the reinforcement configuration in the code calibration process for the capacity reduction factors.
An innovative design concept for improving the durability of concrete bridges
Authors: Berger Johannes , Bruschetini‐Ambro Sebastian Zoran , Kollegger Johann 
Published: October 2013

AbstractIt is proposed to build concrete bridges with tendons fully encapsulated in plastic ducts and without the use of reinforcing steel. In this case the durability of the proposed bridge depends only on the durability of the concrete because corrosion is no longer a determining factor regarding the lifetime of the structure. The requirements of the serviceability and ultimate limit states are fulfilled by providing post‐tensioned tendons with strands fully encapsulated in plastic ducts and watertight anchorages. Since the proposed bridge does not contain any steel, which would be endangered by material‐related corrosion, there is no need for insulation to the deck. Consequently, there is also no need for pavement and edge beams. This concept of building bridges represents a breakthrough with regard to sustainability and durability of concrete bridges and is applicable to small and mediumsized bridges. The method has already been implemented for the design of the Egg‐Graben Bridge in the Großarl valley in the province of Salzburg, Austria. Prior to the actual construction of the bridge, large‐scale tests were performed to obtain practical values for the serviceability, ductility and loadbearing capacity of this structural system.
Ultimate strength of curved strand tendons
Authors: Kollegger Johann , Gmainer Susanne , Lehner Klaus , Simader Josef 
Published: October 2013

AbstractIn a bridge construction process, where large concrete elements are rotated with the aid of strand lifting units (lowering of arch halves, balanced lift method), the tendons have to be deviated over saddles with small radii of curvature. Since information on the ultimate strength of curved strand tendons was not available at the time, a test programme was carried out in order to determine the ultimate strength as a function of radius of curvature (R = 0.5 m, R = 1.0 m, R = 3.0 m, straight tendons), number of strands (1 to 55) and type of strand (0.5″ and 0.6″). The results of the full scale experiments showed almost no decrease in efficiency with regard to single strand tendons and only moderate losses regarding multistrand tendons. Based on the experimental results and a biaxial failure criterion, an analytical model was developed which is able to predict the ultimate strength of curved tendons.
Improvements to the Eurocode 2 shrinkage model for concrete using a large experimental database
Authors: Raphael Wassim , Faddoul Rafic , Geara Fadi , Chateauneuf Alaa 
Published: October 2013

AbstractShrinkage plays an important, sometimes crucial, role in the design of many types of concrete structures as well as in their behaviour after construction. However, the uncontrolled strains are often larger than the expected values. As a matter of fact, there is as yet no perfectly satisfactory physical explanation for shrinkage. In this work, a large database has been set up for shrinkage testing performed by several research centres in Europe. On the basis of the statistical analysis of this database and by observing real structural behaviour, it becomes possible to investigate the current codes of practice regarding the computation of time‐dependent shrinkage strains. As comparison with experimental tests has shown that predictions are often inaccurate, a correction factor is proposed in this work to improve the European Code, Eurocode 2, and lead to more satisfactory results.
Considerations for the design of doubly unsymmetrical precast pretensioned beams used for box girder construction
Authors: Ayoub Essam , Malek Charles , Helmy Gamal 
Published: October 2013

AbstractMany box girder bridges are constructed with doubly unsymmetrical precast beam units. The aim of this paper is to present special considerations for the optimum arrangement of pretensioned strands in a simply supported precast pretensioned beam with a doubly unsymmetrical section. The goal of the optimum arrangement is to minimize the distortion (lateral sway phenomenon) caused by the doubly unsymmetrical characteristic of the beam section at transfer. The study shows that the distortion of the unsymmetrical section is minimized when the resultant stresses at transfer are constant over all of the top flange and over all of the bottom flange of the precast beam for most of the sections within the beam length. In this case, the neutral axes of these sections will be horizontal with respect to the beam section. This approach is verified with the help of two different finite element models. In the first model, the beam is modelled as one‐dimensional space frame elements; in the second model, the beam is modelled using three‐dimensional solid elements. A practical example of a box girder bridge made from doubly unsymmetrical precast pretensioned beams in the APM (Automated People Mover) elevated bridge project in Saudi Arabia is also presented.
Façade damage assessment of concrete buildings in the 2011 Christchurch earthquake
Authors: Baird Andrew , Palermo Alessandro , Pampanin Stefano 
Published: October 2013

AbstractThe magnitude 6.3 earthquake that struck Christchurch on 22 February 2011 caused widespread damage throughout Christchurch's central business district (CBD), where a large proportion of the building stock consists of reinforced concrete (RC) buildings. Damage to the façades of these buildings was a clear contributor to overall building damage. This paper presents the damage assessment of the façade systems of these RC buildings. A survey of 173 RC buildings in the Christchurch CBD is conducted here, focusing on the damage to the façade systems of the buildings. The survey covers only buildings greater than three storeys in height, excluding the majority of unreinforced masonry façades, the damage to which has been well documented. The façade type and modularity is classified for each system, as well as the connection type where possible. The level of damage to each façade is determined in terms of the following performance levels: Operational, Immediate Occupancy, Life Safety and High Hazard. Further investigation is also made into three precast concrete panel systems. These case studies examine the damage, detailing and construction practice of each particular system.
The seismic performance of RC buildings in the 22 February 2011 Christchurch earthquake
Authors: Kam Weng Yuen , Pampanin Stefano 
Published: October 2013

AbstractThe 22 February 2011 Mw 6.2 Christchurch (Lyttelton) earthquake was a particularly severe test for both modern seismically designed and existing non‐ductile reinforced concrete (RC) buildings. Some 16.2 % of 833 buildings with RC systems within the Christchurch central business district (CBD) were severely damaged. There were 182 fatalities, 135 of which were the unfortunate consequences of the complete collapse of two medium‐rise RC buildings. As with the post‐Northridge 1994 earthquake, the design performance of “modern” structures is being scrutinized – with the inevitable question: is “life safety” but irreparable damage still a valid performance target? This brief paper presents a summary of RC building damage from a broad performance‐based earthquake engineering perspective. Several preliminary lessons, not all of them surprising, and the issues that have arisen will be discussed using case study buildings, with suggestions for urgently needed research areas.
Behaviour of grouted dowels used in precast concrete connections
Authors: Aguiar Eduardo Aurélio Barros , Bellucio Ellen Kellen , El Debs Mounir Khalil 
Published: October 2013

AbstractThis research deals with the behaviour of grouted dowels used in beam‐to‐column connections in precast concrete structures. The research focuses primarily on the theoretical and experimental analysis of the resistance mechanism of the dowels. The experimental programme included 15 models for analysing the following variations in dowel parameters: a) dowel diameters of 16, 20 and 25 mm, b) dowel inclinations of 0° (i.e. perpendicular to the interface), 45° and 60°, c) compressive strength of classes C35 and C50 for the concrete adjacent to the dowels, and d) the absence or presence of compressive loads normal to the interface. The experimental results indicate that the ultimate capacity and shear stiffness of the inclined dowels are significantly higher than those of the perpendicular dowels. Based on these results, an analytical model is proposed that considers the influence of the parameters studied regarding the capacity of the dowel.
Design model for reinforcement corrosion
Authors: Osterminski Kai , Schießl Peter 
Published: October 2013

AbstractThe performance‐based durability design of reinforced concrete structures for corrosion of reinforcement is currently limited to the initiation period. That includes modelling the transport processes of chlorides and carbon dioxide into the concrete structure. Up to now, the subsequent time period after depassivation of the reinforcement, in which corrosion propagates, could not be modelled in a comparable manner. The task of the research project presented here, which was part of German Research Unit 537, was to develop a design model that enables a reinforced concrete structure to be designed against reinforcement corrosion for its entire service life. Therefore, a physically well‐defined damage model for corrosion propagation was chosen as a basis. All system parameters in the damage model were investigated on the basis of numerical and laboratory studies carried out in the subprojects of the research unit. Statistical analysis allowed the simplification of the complex damage model into a user‐friendly design model. This paper presents the working steps, the basic results of the analysis and the user‐friendly full‐probabilistic design model for reinforcement corrosion.
Design and optimization of skew reinforcement in concrete shells
Authors: Bertagnoli Gabriele , Giordano Luca , Mancini Simona 
Published: October 2013

AbstractNowadays, it is more and more often necessary to design two‐dimensional reinforced concrete elements to satisfy both architectural demands and to comply with traffic safety requirements in the design of road and railway infrastructures. In fact, the demand for non‐regular structural geometry is increasing in both cases.As a consequence, the use of finite element analyses to model structures and calculate internal actions is constantly growing because closed‐form solutions are generally unavailable for irregular shapes. Therefore, the problem of reinforcement design needs our attention because steel bars, in general, should be placed in non‐orthogonal directions and can vary over the structure.Consequently, there are two different kinds of design problem: choice of reinforcement direction and evaluation of the reinforcement ratio between the chosen directions, with the aim of minimizing the total amount.Such problems can be easily overcome by generalizing a mechanical model consolidated in the literature for orthogonal reinforcement for skew directions. The model is set up according to the ultimate plastic behaviour of the elements. An optimization technique based on genetic algorithms is then applied to the new model to reduce the amount of reinforcement.This paper describes both the ultimate resisting mechanism with generic reinforcement directions and the way genetic algorithms are employed to optimize the amount of reinforcement.
Time‐dependent analysis during construction of concrete tube for tower high‐rise building
Authors: Jiang Wei , Gong Jian , De Schutter Geert , Huang Yulin , Yuan Yong 
Published: October 2013

AbstractVertical and differential deformations in super‐high‐rise buildings are extremely important during construction. In order to be able to adjust the construction process accurately, taking the deformations into account, such deformations must be calculated exactly. The analysis of the vertical deformations of the high‐rise Shanghai World Financial Centre building is illustrated in this paper. The prediction models of CEB‐FIP 90 are used for calculating shrinkage and creep. The fictitious degree of hydration method has been applied for calculating the creep behaviour of the early‐age concrete. The influence of steel bars on the vertical deformations has been analysed based on the macroscopical modulus method. Calculation of the vertical deformations includes the pre‐construction and the post‐construction deformations. Finally, the differential deformation between the concrete and the mega‐structure column is determined. Theoretical results for the vertical displacement of this super‐high‐rise building agree very well with field monitoring data.
Crack healing of cementitious materials using shrinkable polymer tendons
Authors: Isaacs Ben , Lark Robert , Jefferson Tony , Davies Robert , Dunn Simon 
Published: October 2013

AbstractThis paper presents an experimental study on autogenous healing in a recently developed shrinkable polymer cementitious material system. Small‐scale hollow prismatic mortar beams with unbonded shrinkable polymer tendons were loaded until a crack of predefined width had formed. The specimens were then subjected to a range of combined heating/curing regimes to activate the shrinkable polymer and to promote autogenous healing of the cementitious material prior to reloading to failure. Upon reloading, specimens loaded with the shrinkable polymer tendons remaining after heating and curing achieved between 120 and 195% of their initial peak loads, whereas specimens tested with the shrinkable polymer tendons removed after the heating and curing stages recovered on average 80% of their initial peak loads. The overall conclusion was that, provided a supply of water is present and sufficient heat is applied for polymer activation, the material system is effective at not only closing cracks and applying a prestress, but also at enhancing the self‐healing of cracks in cementitious materials.
The influence of aggregate fracture on the shear strength of reinforced concrete beams: an experimental and analytical research project
Authors: Sagaseta Juan 
Published: October 2013

AbstractHigh‐performance concretes such as high‐strength concrete (HSC) or lightweight aggregate concrete (LWAC) are generally used to reduce member sizes and self‐weight, and to optimize the construction of reinforced concrete structures. The bond between the aggregate particles and the cement paste can be strong enough in HSC and LWAC to cause the aggregate to fracture at cracks, which in turn reduces the shear stress that can be transferred across cracks by means of aggregate interlock. Relatively smooth cracks can also develop in self‐compacting concrete due to the low coarse aggregate content. The contribution of aggregate interlock to the shear strength of RC beams is uncertain and depends on parameters such as the amount of shear reinforcement or the contribution of arching action for loads applied close to the support. Existing tests on slender RC beams without shear reinforcement have shown that shear strength is reduced by aggregate fracture. However, there is a lack of similar test data for members with stirrups and for members with varying shear span/effective depth ratios. This paper reviews the findings and contributions in this area from the experimental and analytical research of the author's PhD thesis, which was awarded the fib Achievement Award for Young Engineers in 2011.
Development of a mix design methodology for high‐performance geopolymer mortars
Authors: Ng Tian Sing , Foster Stephen J. 
Published: October 2013

AbstractThis paper presents the development of a mix design method for geopolymer mortar mixes with a principal focus on compressive strength. The method is based on the hypothesis that the overall strength of geopolymer mortar depends on the strength of the geopolymer binder materials, the packing density of the aggregates in the mortar and the amount of geopolymer binder. First, the strength of the binder was evaluated experimentally. Fly ash obtained from two different sources and ground granulated blast‐furnace slag were used as the main ingredients in the production of the geopolymer binder. Correlation between the packing density of the aggregates in the mortar and their influence on the binder demand and compressive strength were investigated. Finally, a conceptual framework for a geopolymer mortar mix design approach is proposed. In addition to describing the mortar mix design methodology in a rational way, it is hypothesized that the approach can also be extended to the development of a geopolymer concrete mix.
Design for service life: implementation of fib Model Code 2010 rules in the operational code ISO 16204
Authors: Helland Steinar 
Published: October 2013

AbstractCEB/FIP Model Code 1990 (MC‐1990) did represent the technology and focus some 20 years ago. However, it soon became evident that the document had some notable lacunas. In 1995 the general assemblies of the two organizations endorsed CEB/FIP bulletin No. 228, extensions to MC 1990 for high‐strength concrete, and in 2000 a similar extension to MC 1990 for lightweight aggregate concrete as bulletin No. 4.The fib approved bulletin No. 34 Model Code for Service Life Design (MC SLD) in 2006. All these three additions have since matured and are now incorporated in the new fib Model Code for Concrete Structures 2010 (MC‐2010).The main purpose of an fib Model Code is to act as a model for operational standards. The obvious counterpart for a body such as fib operating worldwide is ISO. The initiative taken by MC SLD has therefore further matured in ISO TC‐71/SC‐3/WG‐4 and it was accepted as ISO 16204 “Durability – Service Life Design of Concrete Structures” during the summer of 2012.According to the obligations given in the WTO Agreement on Technical Barriers to Trade, it is hoped that these principles will be further implemented in national and regional standards.This article describes the need for a transparent methodology when dealing with service life design, and the process – originating from a group of enthusiasts one decade ago – through fib and finally reaching international consensus in ISO.
Behaviour of concrete in a stress continuity region after cracking under restrained drying shrinkage
Authors: Seo Tae‐Seok , Kim Jung‐Chul 
Published: October 2013

AbstractSome studies have investigated the time‐dependent characteristic of concrete for predicting stress under restrained shrinkage. However, these studies investigated the shrinkage behaviour of concrete in restrained conditions before cracking, and no study has yet investigated the behaviour of concrete due to restrained shrinkage in the stress continuity region after cracking. Therefore, this study investigates the shrinkage behaviour of concrete in the stress continuity region after cracking in uniaxial restrained specimens and analyses the restrained tensile stress of concrete in this region by way of a bond analysis. The results show that the effective tensile Young's modulus considering tensile creep is approx. 22–26% of the static modulus of elasticity. Moreover, the analytical results of the restrained tensile stress of concrete considering the effective tensile Young's modulus were in accordance with the experimental results.
Resistance of reinforced concrete members with hollow circular cross‐section under combined bending and shear – Part II: New calculation model
Authors: Völgyi István , Windisch Andor 
Published: October 2013

AbstractPart II analyses the applicability of current shear design models for RC members with a hollow circular cross‐section on the basis of experimental results introduced in Part I of this paper. A new calculation model is proposed which assigns the contribution of the concrete zone in compression to shear resistance. The proposed model takes into account how the flexural and shear reinforcement, the load‐to‐support distance and the shape of the cross‐section affect the shear resistance.The model is based on the analysis of potential failure sections subjected to bending and shear, and applies a compatibility criterion that considers how the member carries the load. The analogy between the failure of the concrete compression zone and the failure of the soil along a sliding surface are presented as well as the conditions for the development of the failure section.
Residual compressive and flexural strength of a recycled aggregate concrete following elevated temperatures
Authors: Xiao Jianzhuang , Fan Yuhui , Tawana M.M. 
Published: October 2013

AbstractA recycled aggregate concrete (RAC) with different replacement percentages of recycled coarse aggregates (RCAs) (i.e. 0, 30, 50, 70, 100%) was investigated experimentally at elevated temperatures. The residual compressive strength as well as the residual flexural strength of the RAC following elevated temperatures was studied and evaluated. A relationship between the residual compressive flexural strength of RAC and the elevated temperature was proposed. Furthermore, the relationship between the residual flexural strength and the compressive strength of the RAC was compared and analysed. It was found that both the residual compressive strength and the residual flexural strength of the RAC decrease with a rise in temperature, and the effect of the RCAs replacement percentage on the residual flexural strength and the residual compressive strength of RAC was found to be obvious.