bluuebunny/crossref_metadata_2025 huggingface dataset:
Weather forecast skill comparisons at a location in the Midwest United States
Authors: Athar H. , Sara A.
Published: October 2013

This paper presents the results of a forecast skill score comparison for the popular two semester weather forecast game played at University of Missouri, Columbia, MO, United States, for a total of 106 days, during the autumn 2006 and winter 2007 semesters. A relatively less experienced/first time student forecaster (SF) skill, based upon the funnel approach to weather forecasting, is compared with the then state‐of‐the‐art mesoscale operational numerical weather prediction (NWP) model outputs and the observations. Several measures of the forecast skills are employed to illustrate the intercomparison of the different aspects of performance of the game players for a conventional forecast game setup in an educational environment, after paying particular attention to the associated sampling uncertainty in the analysis of the forecast game. Bootstrap resampling based confidence intervals are computed and compared for the SF and NWP model forecasts and the observations to quantify the relative accuracies of the forecasts. The SF performed quite comparable to the NWP models, and better than the climatology and the persistence, for the next‐day forecasts of temperature and precipitation, when the forecast skill scores of the game players were averaged over the period of the forecast game. These observations support the judgement that the contribution of human forecasters, even in the contemporary era of progressively improving and fully automated NWP model outputs, remained a crucial one.
Lower extremity soft tissue defect reconstruction with the serratus anterior flap
Authors: Mastroianni Melissa , Leto Barone Angelo A. , Shanmugarajah Kumaran , Leonard David A. , Di Rosa Luigi , Feingold Randall S. , Israeli Ron , Cetrulo Curtis L.
Published: October 2013

Reconstruction of limb‐threatening lower extremity defects presents unique challenges. The selected method must provide adequate coverage of exposed bone, joints, and tendons while maximizing function of the limb. The traditional workhorse flaps, the free latissimus dorsi and rectus abdominis flaps, have been associated with donor site morbidity and bulkiness that can impair rehabilitation. We report a case series (n = 18) in which the free serratus anterior muscle flap and split thickness skin graft (STSG) was used for lower limb soft tissue coverage. Injuries were due to diabetes (9/18), trauma (7/18), and chronic venous stasis (2/18). A 94% flap survival rate was observed and all but one patient was ambulatory. No donor site morbidity was reported. Our series demonstrates that serratus anterior is an advantageous, reliable free flap with minimal donor site morbidity. © 2013 Wiley Periodicals, Inc. Microsurgery 34:183–187, 2014.
Complex phase behavior and state of miscibility in Poly(ethylene glycol)/Poly(l‐lactide‐co‐ε‐caprolactone) Blends
Authors: Hernandez‐Montero N. , Ugartemendia Jone M. , Amestoy Hegoi , Sarasua J. R.
Published: October 2013

A miscibility and phase behavior study was conducted on poly(ethylene glycol) (PEG)/poly(l‐lactide‐ε‐caprolactone) (PLA‐co‐CL) blends. A single glass transition evolution was determined by differential scanning calorimetry initially suggesting a miscible system; however, the unusual Tg bias and subsequent morphological study conducted by polarized light optical microscopy (PLOM) and atomic force microscopy (AFM) evidenced a phase separated system for the whole range of blend compositions. PEG spherulites were found in all blends except for the PEG/PLA‐co‐CL 20/80 composition, with no interference of the comonomer in the melting point of PEG (Tm = 64 °C) and only a small one in crystallinity fraction (Xc = 80% vs. 70%). However, a clear continuous decrease in PEG spherulites growth rate (G) with increasing PLA‐co‐CL content was determined in the blends isothermally crystallized at 37 °C, G being 37 µm/min for the neat PEG and 12 µm/min for the 20 wt % PLA‐co‐CL blend. The kinetics interference in crystal growth rate of PEG suggests a diluting effect of the PLA‐co‐CL in the blends; further, PLOM and AFM provided unequivocal evidence of the interfering effect of PLA‐co‐CL on PEG crystal morphology, demonstrating imperfect crystallization in blends with interfibrillar location of the diluting amorphous component. Significantly, AFM images provided also evidence of amorphous phase separation between PEG and PLA‐co‐CL. A true Tg vs. composition diagram is proposed on the basis of the AFM analysis for phase separated PEG/PLA‐co‐CL blends revealing the existence of a second PLA‐co‐CL rich phase. According to the partial miscibility established by AFM analysis, PEG and PLA‐co‐CL rich phases, depending on blend composition, contain respectively an amount of the minority component leading to a system presenting, for every composition, two Tg's that are different of those of pure components. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014, 52, 111–121
Randomized trial of print messaging: the role of the partner and monitoring style in promoting provider discussions about prostate cancer screening among African American men
Authors: Miller Suzanne M. , Roussi Pagona , Scarpato John , Wen Kuang‐Yi , Zhu Fang , Roy Gem
Published: October 2013

Objective

Although African American (AA) men are at elevated risk for prostate cancer, medical guidelines do not present consistent screening recommendations for this group. However, all guidelines stress the need for screening decision making with a provider. This study evaluated the effectiveness of a brochure for the female partners of AA men, designed to help promote such discussion on the part of their mates. We also explored the effect of the partner's monitoring style (i.e., the extent to which the partner typically attends to health threats) on promoting discussion.

Methods

Female partners of AA men (N = 231) were randomized to receive either a prostate cancer screening Centers for Disease Control brochure for AA men, combined with a ‘partner’ brochure containing strategies to promote men's initiation of a provider visit to discuss screening, or the Centers for Disease Control brochure only and completed preintervention and post‐intervention surveys online.

Results

The message groups did not differ on taking active steps to engage in provider discussion: relative risk ratio (RRR) = 0.99, p = .98; thinking about it: RRR = 1.13, p = .74. However, among partners who received the partner brochure, monitoring style was associated with ‘thinking about initiating a provider visit’ on the part of the mate (RRR = 1.74, p < .01). Across conditions, monitoring style was also associated with ‘taking active steps to initiate a provider visit’ on the part of the mate (RRR = 1.38, p < .05).

Conclusions

High monitoring partners may be effective in influencing their AA mates to initiate provider discussion, particularly when tailored messaging is provided. Copyright © 2013 John Wiley & Sons, Ltd.
The C‐terminal extension of human RTEL1, mutated in Hoyeraal‐Hreidarsson syndrome, contains Harmonin‐N‐like domains
Authors: Faure Guilhem , Revy Patrick , Schertzer Michael , Londono‐Vallejo Arturo , Callebaut Isabelle
Published: October 2013

Several studies have recently shown that germline mutations in RTEL1, an essential DNA helicase involved in telomere regulation and DNA repair, cause Hoyeraal‐Hreidarsson syndrome (HHS), a severe form of dyskeratosis congenita. Using original new softwares, facilitating the delineation of the different domains of the protein and the identification of remote relationships for orphan domains, we outline here that the C‐terminal extension of RTEL1, downstream of its catalytic domain and including several HHS‐associated mutations, contains a yet unidentified tandem of harmonin‐N‐like domains, which may serve as a hub for partner interaction. This finding highlights the potential critical role of this region for the function of RTEL1 and gives insights into the impact that the identified mutations would have on the structure and function of these domains. Proteins 2014; 82:897–903. © 2013 Wiley Periodicals, Inc.
Lonely Sunsets: Impacts of Rural–urban Migration on the Left‐behind Elderly in Rural China
Authors: He Congzhi , Ye Jingzhong
Published: October 2013

Drawing on the data from the research that samples 400 elderly who lived separately from their migrant children in 10 rural communities in China, this paper examines how the outmigration of rural youth shapes the situation of their older kin and analyses the consequences of the rural–urban migration for the old‐age support system. The research finds that a large scale of rural labour force has been drained off from rural societies and placed in a ‘semi‐proletarianized’ situation during the recent three decades of rapid social transformations. The rules and resources of traditional care system have been changed and family is no longer a ‘network of safety’ or reliable source of obtaining support for the elderly. Although some elastics and adaptabilities can be found in rural families, the family cannot soften and deal with all the risks popped up in the transformation independently. It can be said that the migration of the rural workforce to urban centres has degraded the welfare of the left‐behind elderly. Institutional interventions should no longer mystify and romanticise the role of the family, rather, it should look beyond the family level, caring more about ‘human beings’ instead of economy and efficiency. Copyright © 2013 John Wiley & Sons, Ltd.
Consensus of positive real systems cascaded with a single integrator
Authors: Oh Kwang‐Kyo , Lashhab Fadel , Moore Kevin L. , Vincent Tyrone L. , Ahn Hyo‐Sung
Published: October 2013

We study output consensus in a network of interconnected non‐identical positive real systems cascaded with a single integrator. Assuming undirected, diffusive interconnections, sufficient conditions are provided to ensure output consensus for two cases: (i) the individual systems are weakly strictly positive real systems cascaded with a single integrator, and (ii) the individual systems are positive real systems cascaded with a single integrator. We illustrate our results with the example of a load frequency control network of synchronous generators. Copyright © 2013 John Wiley & Sons, Ltd.
Development of a new bridge construction method using suspension structures
Authors: Kasuga Akio
Published: October 2013

A unique suspension method developed over a period of more than 10 years produces a rational structure in the form of a single‐span composite truss bridge. For this structure, the steel truss and concrete deck are constructed on the spanning cables. During construction the horizontal forces of these cables are anchored into the ground, but after completion of the bridge the forces are transferred to concrete upper and lower chords as prestressing forces. A single‐span composite truss bridge of this type can be constructed without temporary supports or falsework. Using this method to bridge a deep valley produces benefits in terms of both construction costs and sustainability. A single‐span bridge requires less excavation than other bridge types, and utilizing a composite truss with this construction method can minimize the environmental impact of the construction.
Green concrete structures
Authors: Glavind Mette
Published: October 2013

There are numerous ways of improving concrete structure's environmental performance. An overview of these are presented and exemplified in the present article. They include choice of raw materials, mix design of the concrete, production processes, construction processes, design and use during service life and the end‐of‐life demolition‐crushingreuse. Thus the whole life cycle is considered. This will be the key content of the future fib 3.8 guidelines on green concrete structures which will also include some background information and specific benchmark data.
Anchorage failure and shear design of hollow‐core slabs
Authors: Araujo Carlos Antonio Menegazzo , Loriggio Daniel Domingues , Da Camara José Manuel Matos Noronha
Published: October 2013

A number of studies in recent years have attempted to understand and calculate the shear strength of hollow‐core slabs, but no consensus has been reached on this issue. The current design methods for hollow‐core shear resistance are derived from experimental results and elastic theories that are not usually directly related to the behaviour at the ultimate limit state. Moreover, some manuals on this subject do not discuss anchorage failures, which although not common in this type of slab, may influence the shear strength. This paper considers the anchorage failure of strands using the concepts of Eurocode 2 and presents an analytical methodology for shear design based on the modified compression field theory (MCFT). Furthermore, the safety concepts of Eurocode 2 are properly presented and evaluated using the experimental data available in the literature. The proposed methodology is proved to be accurate and is simple enough for use in design. Comparisons with CSA A23.3 and Eurocode 2 are also shown.
Life cycle assessments of concrete structures – a step towards environmental savings
Authors: Hájek Petr , Fiala Ctislav , Kynčlová Magdaléna
Published: October 2013

Considering the volume of concrete produced and the number of concrete structures built, the problem of the associated environmental impact forms a significant part of the entire global problem of sustainable development. Utilization of environmentally optimized concrete structures thus creates a potential for increasing the quality of construction and consequently a reduction of the environmental impact. A life cycle assessment (LCA) is a complex, multi‐parametric assessment of the environmental impact of the structure over its whole life cycle. It covers, in one assessment process, all the essential environmental issues, including CO2 emissions, energy consumption, water consumption, waste generation, etc. In the case of concrete, selected criteria should support the design and construction of high‐quality and at the same time environmentally friendly concrete structures. The principal problem is to collect relevant environmental input data for specific concrete types plus transport and production processes which can be used in the LCA procedure.
Footbridge across the River Svratka in Brno, Czech Republic
Authors: Stráský Jiří , Štefan Petr , Nečas Radim
Published: October 2013

This bridge, which won a fib Award for Outstanding Concrete Structures in 2010, connects a newly developed area (Spielberk Office Centre) with an old city district. It is situated in the vicinity of a new international hotel and a prestige business area. Close to the bridge there is an old multi‐span arch bridge with piers in the river. It was evident that any new bridge should also make use of an arch structure, but with a bold span not needing piers in the riverbed, see Fig. 1. Due to poor geotechnical conditions, a traditional arch structure with a large horizontal force to be resisted was considered too expensive. Therefore, a self‐anchored stress ribbon and arch structure was chosen. The smooth curves so characteristic of stress ribbon structures allowed a “soft” connection of the bridge deck at both banks.
Design and optimization of fabric‐formed beams and trusses: evolutionary algorithms and form‐finding
Authors: Veenendaal Diederik , Coenders Jeroen , Vambersky Jan , West Mark
Published: October 2013

Fabric formwork entails the use of fabrics as the main contact material for a concrete mould. The fabric is either hung or prestressed in a supporting falsework frame. Beams or trusses cast in fabric formwork are inherently non‐prismatic and have been shown to offer potential for structurally efficient shapes. The casting of beams or trusses in fabric formwork is a highly non‐linear problem due to the interaction of the fluid concrete with the woven, prestressed fabric material. Numerical models need to be developed for the engineering of these elements. To this end, it is demonstrated that it is feasible to integrate manufacturing constraints in an automatic optimization process. This is achieved by creating an automated computational framework that includes fabric form‐finding and finite element analysis, which operate within an optimization process that uses principles from biological evolution. The results show structurally efficient and manufacturable beams and demonstrate potential for optimization in general that explicitly includes fabrication considerations.
The 2010 fib Model Code for Structural Concrete: a new approach to structural engineering
Authors: Walraven Joost C. , Bigaj‐van Vliet Agnieszka
Published: October 2013

The fib Model Code is a recommendation for the design of reinforced and prestressed concrete which is intended to be a guiding document for future codes. Model Codes have been published before, in 1978 and 1990. The draft for fib Model Code 2010 was published in May 2010. The most important new element in this Model Code is “Time” in the sense of service life. Additionally, the Model Code contains an extended state‐of‐theart chapter on the structural materials concrete and steel but regards non‐metallic reinforcement and fibres as reinforcement as well. Many loading conditions are considered, ranging from static loading to non‐static loading, considering earthquake, fatigue and impact/explosion. Five methods are offered to verify structural safety. Attention is given to verification of limit states associated with durability, robustness and sustainability. Finally, verification assisted by numerical methods and by testing is considered. Other elements that are links in the chain of life cycle design are construction and conservation. In the part on conservation the conservation strategy is treated in combination with conservation management, condition survey and assessment, and evaluation and decision‐making.
Determining the in situ concrete strength of existing structures for assessing their structural safety
Authors: Steenbergen R.D.J.M. , Vervuurt A.H.J.M.
Published: October 2013

EN 13791 applies when assessing the in situ compressive strength of structures and precast concrete components. According to the code itself, it may be adopted when doubt arises about the compressive strength of a concrete. For assessing the structural safety of existing structures, however, the method given in EN 13791 does not seem to be applicable and may lead to an unsafe approach for determining the characteristic concrete strength. This paper presents an alternative method for determining the characteristic concrete strength from cylinders obtained in situ. The method proposed is based on EN 1990 (Eurocode basis of design) and the corresponding Annex D. The method according to EN 13791 is outlined in this article. Moreover, the practical implementation of the method in accordance with clause 5.2 of EN 1990 is explained and an example is given. Finally, both methods are compared with each other. It is demonstrated that EN 13791 does not apply to safety assessments of existing concrete structures and the use of this code may lead to unsafe situations.
Design according to MC2010 of a fibre‐reinforced concrete tunnel in Monte Lirio, Panama
Authors: Caratelli Angelo , Meda Alberto , Rinaldi Zila
Published: October 2013

This paper discusses the possibility of using precast tunnel segments in fibre‐reinforced concrete without traditional reinforcement. The case study of a hydraulic tunnel in Monte Lirio, Panama, excavated with a tunnel boring machine (TBM) by SELI S.p.A., has been analysed.

The segments were designed according to the draft of Model Code 2010. In order to achieve the required performance and to optimize the structural behaviour, three different types of steel fibre were considered in the research.

The design was backed up by full‐scale tests on precast segments. In particular, 18 full‐scale tests were performed, including point load tests simulating the thrust of the TBM and bending tests. The results show the good behaviour of the elements and indicate the fibre‐reinforced concrete suitable for the precast elements.
DEM simulation of concrete fracture and crack evolution
Authors: Beckmann Birgit , Schicktanz Kai , Reischl Dirk , Curbach Manfred
Published: October 2013

A two‐dimensional simulation of concrete behaviour using the discrete element method (DEM) is presented in this work. The main aim of this paper is the modelling of the failure process and crack initiation. The failure process of a concrete prism during a compression test is simulated. A substructure representing the concrete components – aggregate and cement matrix – is introduced. It is shown that convex and concave concrete specimens can be treated, whereas the particle geometry always remains convex. The crack patterns of the concrete specimens resulting from the simulation are shown and compared with laboratory experiments. It is shown that the calculated peak load does not depend on the particle number used in the simulation. The ratio of lateral strain to longitudinal strain of the concrete specimen during load application is simulated and compared with experimental results.
Seismic performance of concrete bridges during Canterbury earthquakes
Authors: Palermo Alessandro , Wotherspoon Liam , Hogan Lucas , Le Heux Mitchel , Camnasio Elena
Published: October 2013

In less than six months, the city of Christchurch, New Zealand, experienced two major earthquakes: on 4 September 2010 and 22 February 2011. The former was generated by the rupture of the previously unknown Greendale fault, releasing a magnitude Mw 7.1 earthquake 30–40 km away from the Central Business District (CBD); the latter event, of magnitude Mw 6.2, was less than 10 km from the CBD on an unknown buried fault at the edge of the city. There was widespread damage to the lifelines covering not only Christchurch City but also the closest districts of Selwyn and Waimakariri. The different nature of the fault ruptures and locations of the two events resulted in a variation in damage levels between the earthquakes throughout the region.

Teams from various organizations performed inspections on over 800 bridges throughout the affected Canterbury region. No major collapses were registered among concrete bridges and only 20 bridges required closure due to damage caused by the two earthquakes. Owing to the nature of the Canterbury soils, extensive liquefaction and lateral spreading occurred throughout the region. It was this lateral spreading that caused most of the traffic disruption and closure of bridges, due to damage to the abutments and approaches, foundation settlement and rotation.

The authors aim to give a detailed overview of the damage assessment and seismic performance of the Canterbury bridges during these two earthquakes, emphasizing unexpected issues that are still not properly detailed in New Zealand and overseas standards.
Analysis of the subgrade stiffness effect on the behaviour of ground‐supported concrete slabs
Authors: Alani Amir M. , Aboutalebi Morteza
Published: October 2013

This paper confirms that the structural behaviour of ground‐supported slabs is a non‐linear function of the structural properties of slabs as well as the supporting soil. The findings reported emphasize that the suggested equations used in design codes pay insufficient attention to the effect of the supporting ground stiffness within the context of the mechanical behaviour of slabs as far as ductility is concerned. The results presented demonstrate that ground stiffness has a significant effect on the ductility of ground‐supported slabs. It also pays particular attention to the possibility of determining the ductility limit of slabs.
Design model for the fatigue behaviour of normal‐strength, high‐strength and ultra‐high‐strength concrete
Authors: Lohaus Ludger , Oneschkow Nadja , Wefer Maik
Published: October 2013

Fatigue design according to CEB‐FIP Model Code 90 is limited to concrete grades up to C80. In addition, the design rules include a strength‐dependent reduction in the fatigue reference strength, which leads to uneconomical design of high‐strength concrete. Considering comprehensive knowledge now available concerning the fatigue behaviour of normal‐strength and high‐strength concretes, the amount of this reduction can no longer be justified. A new design model for compressive fatigue loading and its derivation is presented in this article. A comparison between the new design model and the current standard ones reveals that the new design model ensures safe and economical design of normal‐strength, high‐strength and ultra‐high‐strength concrete. This new design model is included in the new fib Model Code 2010.
Performance of olive waste ash concrete exposed to alkali‐silica reaction
Authors: Al‐Akhras Nabil M.
Published: October 2013

This work investigates the effect of olive waste ash (OWA) on the durability of concrete exposed to alkali‐silica reaction (ASR). Three OWA contents were considered in the work: 7, 15 and 22 %, with crushed Pyrex glass used as reactive fine aggregate. The other experimental parameters investigated in the study were: w/c ratio (0.4 and 0.5) and air content (non‐air‐entrained and air‐entrained). The OWA concrete specimens were submerged in 1‐N NaOH solution at 40 °C to accelerate the ASR. The ASR damage was monitored by measuring the expansion of concrete prisms and the decrease in compressive strength.

The study demonstrates that OWA concrete is more resistant to ASR deterioration than plain concrete. The durability of OWA concrete with respect to ASR damage improved with the increase in OWA content. The OWA concrete with a w/c ratio of 0.4 exhibited a better performance with respect to ASR deterioration than the OWA concrete with a w/c ratio of 0.5. The air‐entrained OWA concrete exhibited better durability with respect to ASR damage than the non‐air‐entrained OWA concrete.
Dynamic response of concrete footbridges
Authors: Stráský Jiří , Nečas Radim , Koláček Jan
Published: October 2013

Experience with the analysis and performance of 15 lightweight concrete footbridges is presented from the point of view of their dynamic response caused by moving people. The footbridges are formed either by a stress ribbon or by a slender deck supported by arches or suspended from pylons. The dynamic response was determined according to a procedure given in a 1998 draft of Eurocode 2: Design of Concrete Structures – Part 2: Concrete Bridges. Thirteen footbridges have been built and so far no complaints about their dynamic behaviour have been recorded.
Transverse thermal stresses in concrete box cross‐sections due to climatic exposure
Authors: Larsson Oskar , Thelandersson Sven
Published: October 2013

Spatial and temporal temperature variations in a concrete structure due to variations in the surrounding climate will produce movements which, if restrained, may induce stresses in the structure. To get a better understanding of transverse thermal stresses due to climatic effects in concrete box cross‐sections, the FE simulations in this study have been performed using extensive climatic input data directly or by using simplified methods to simulate the temperature and resulting stress fields in a section of the hollow concrete arch of the New Svinesund Bridge. Studies of other cross‐sections with varying depth, width and wall thicknesses have also been performed to investigate the geometrical influence. The results reveal an overestimation of the maximum thermal tensile stress when using a linear temperature differential approach compared with the direct use of climate data that includes the non‐linear part of the temperature distribution. The effect of depth, width and orientation is negligible compared with variations in thickness between slabs and walls. For box sections with slabs/walls having different thicknesses, the transverse thermal stresses will be significantly larger in the thinner members, irrespective of the actual orientation and position of the member.
Cracking of RC members revisited: influence of cover, ϕ/ρs, ef and stirrup spacing – an experimental and theoretical study
Authors: Pérez Caldentey Alejandro , Corres Peiretti Hugo , Peset Iribarren Joan , Giraldo Soto Alejandro
Published: October 2013

This article describes an experimental programme aimed at studying the effect of cover, ratio between diameter and effective reinforcement ratio (ϕ/ρs, ef) and the influence of stirrup spacing on the cracking behaviour of reinforced concrete elements. The experimental programme was conceived in order to contribute to the debate – fuelled by the publication in recent years of Eurocode 2 EN1992‐1‐1 and the revision of the Model Code under way when the tests were carried out (and now published as a finalized document) – regarding the influence of these parameters on cracking. Important theoretical aspects are discussed, including where the crack width is estimated by current code formulations and what relevance this may have on the correlation between crack opening and durability of RC structures, especially with regard to structures with large covers. The effect of stirrup spacing, a variable absent from current codes, is also discussed.
Global safety format for non‐linear analysis of reinforced concrete structures
Authors: Allaix Diego Lorenzo , Carbone Vincenzo Ilario , Mancini Giuseppe
Published: October 2013

Semi‐probabilistic safety formats for the non‐linear analysis of reinforced concrete structures are of practical interest for structural designers. The safety format proposed in EN 1992‐2 enables a safety assessment through a non‐linear structural analysis and the application of a global safety factor, which is defined as the ratio between the representative and design values of the material resistances. A more realistic estimate of the global safety factor can be obtained from the distribution of the structural response. This paper proposes a safety format based on the mean values of the material resistances and a global resistance factor. Its practical application in the structural design of concrete beams and columns is also presented.
Finite element study of bond strength between concrete and reinforcement under uneven confinement condition
Authors: Zanuy Carlos , Curbach Manfred , Lindorf Alexander
Published: October 2013

It is well known that many factors affect the bond behaviour between concrete and steel reinforcement. Most of them characterize the degree of confinement, which is necessary for an appropriate determination of the bond strength and bond‐slip relationship according to most extended models. Nevertheless, there are situations where the confinement is not known in advance or it can hardly be defined. That is, for example, the case of reinforced concrete under transverse pressure or tension. Under such conditions the confinement varies both longitudinally and circumferentially. This paper presents a 3D finite element approach to study the bond capacity of cases where the bond strength of the specimen is the result of the different contribution provided along the steel‐concrete interface and cannot be described uniquely. A surface‐to‐surface contact model with frictional behaviour and debonding is used to study the influence of the local stress state at the interface. The model is able to reproduce the different failure modes (splitting or pull‐out) obtained in experiments and provide a rational explanation of the influence of transverse tension.
Resistance of reinforced concrete members with hollow circular cross‐sections under combined bending and shear – Part I: experimental investigation
Authors: Völgyi István , Windisch Andor , Farkas György
Published: October 2013

Part I of this paper introduces an experimental programme carried out on RC members with thick‐walled hollow circular cross‐sections to study their behaviour under combined bending and shear. The study looked at ultimate resistance and propagation of characteristic crack pattern as well as the shape and behaviour of the failure sections as a function of wall thickness, amount of longitudinal and transverse reinforcement, shear span and axial force. Test results were used to verify a newly developed calculation model describing the behaviour of the members investigated at failure under combined bending and shear. This model will be presented in Part II.
Sound engineering through conceptual design according to the fib Model Code 2010
Authors: Corres‐Peiretti Hugo
Published: October 2013

Conceptual design is the approach that creates an idea in order to find a solution to a new proposal for a structure or solve a detail in a specific structure. It is a personal approach that is learned over time and with experience. It is not normally dealt with at university, but is vitally important for producing sound structures.

The fib Model Code for Concrete Structures 2010 introduced this concept in the first section of chapter 7 “Design”. The content of that section explains the general approach to developing conceptual design.

This paper will show different examples of conceptual design following the general guidelines stated in the Model Code.
Shear resistance evaluation of prestressed concrete bridge beams: fib Model Code 2010 guidelines for level IV approximations
Authors: Belletti Beatrice , Damoni Cecilia , den Uijl Joop A. , Hendriks Max A. N. , Walraven Joost C.
Published: October 2013

The design shear resistance of an existing structure can be evaluated with analytical design procedures and numerical procedures provided by non‐linear finite element analyses. The new fib Model Code 2010 proposes different calculation methods that fall into four different levels of approximation. As the level of approximation rises, so the complexity and the accuracy of the calculated shear resistance increases. Non‐linear finite element analyses belong to the highest level of approximation, but although they are more and more becoming a customary tool in the daily design process, building codes do not provide guidance on how to perform these analyses.

This paper describes non‐linear finite element analyses performed on prestressed beams, which underwent shear failure during experimental loading, in order to assess and criticize the finite element approaches. The aim of this work is to propose guidelines for numerical simulations in order to reduce model and user factors. The results obtained from the non‐linear finite element analyses have been compared with the analytical results using different levels of approximation. The design shear resistance obtained with the highest level of approximation, level IV, derived from non‐linear finite element analyses, turned out to be higher than the design shear resistance obtained with analytical procedures (levels I/II/III).
Concrete: treatment of types and properties in fib Model Code 2010
Authors: Müller Harald S. , Anders Isabel , Breiner Raphael , Vogel Michael
Published: October 2013

Section 5.1 “Concrete” of the fib Model Code for Concrete Structures 2010 contains basic definitions and well‐established constitutive relations for structural concrete. However, it also presents various new approaches and updated models compared with the earlier CEB‐FIP Model Code 1990. This is particularly true for the strength, stress and strain characteristics of structural concrete, for creep and shrinkage and for sophisticated durability‐related processes. The validity of the models has been extended to several types of concrete such as high strength concrete, self‐compacting concrete and lightweight aggregate concrete. The durability‐related models are either suitable for facilitating a full probabilistic service life design or for applying simpler code‐type approaches.

This article provides a concise and selective overview of some of those models. Background information is summarized and there is a focus on improvements achieved by the updated models. In addition, some simple design aids are given to allow pre‐design, for example
3D numerical modelling of concrete structural element reinforced with ribbed flat steel rebars
Authors: Phan Thanh Song , Tailhan Jean‐Louis , Rossi Pierre
Published: October 2013

Construction company MATIERE has developed a new type of reinforcement based on ribbed flat steel in recent years. The objective of the present work is to obtain information about the bending behaviour of RC structural elements reinforced with these ribbed flat steel bars and also about the cracking process they induce (number of cracks and crack opening), especially at the serviceability limit state. The structural element chosen for this work is a small slab‐beam (330 × 15 × 80 cm) subjected to three‐point central bending. Concurrent with this experimental study, a 3D finite element model was developed at IFSTTAR to consolidate the experimental results. It appears that the numerical modelling strategy chosen in this work is relevant for analysing both the bending behaviour of an RC structural element and its cracking process.
Restoring force model for steel reinforced concrete columns with high steel ratio
Authors: Lu Xilin , Yin Xiaowei , Jiang Huanjun
Published: October 2013

Key points on the load‐displacement skeleton curves of steel reinforced concrete (SRC) composite cantilever columns are established based on the experimental results in the literature. Influencing parameters such as the ratio of encased steel, the transverse reinforcement characteristic value, the size of the cross‐section, etc. are considered in the study. A degrading trilinear restoring force model applicable to SRC columns with an encased steel ratio of 10–20% is suggested. The main results show that the influencing parameters have different effects on the values of key points. The proposed restoring force model, which considers various influencing parameters, can predict the test results more accurately and can be applied to the non‐linear dynamic analysis of structures with such SRC column types.
Concrete shells – towards efficient structures: construction of an ellipsoidal concrete shell in Switzerland
Authors: Muttoni Aurelio , Lurati Franco , Fernández Ruiz Miguel
Published: October 2013

Concrete shells have been widely used in the past as economical and suitable solutions for a number of structures such as roofs, silos, cooling towers and offshore platforms. Taking advantage of their single or double curvature, bending moments and shear forces are limited, and the structures develop mostly membrane (in‐plane) forces, allowing them to span large distances with limited thicknesses (typically just a few centimetres). In recent decades, advances in numerical modelling, formwork erection and concrete technology have opened up a new set of possibilities for the use of concrete shells. This paper describes the design and construction of a shell in the form of an ellipsoid (93 × 52 × 22 m) and with thickness varying between 100 and 120 mm. The shell was built using sprayed concrete and also ordinary concrete in some regions. A number of tailored solutions were also adopted, such as post‐tensioning, addition of fibres and shear studs, to ensure satisfactory performance at both the serviceability and ultimate limit states.
Background to fib Model Code 2010 shear provisions – part II: punching shear
Authors: Muttoni Aurelio , Ruiz Miguel Fernández , Bentz Evan , Foster Stephen , Sigrist Viktor
Published: October 2013

This paper outlines the theoretical background to the punching shear provisions implemented in the fib Model Code for Concrete Structures 2010 and presents a practical example of their application. The aim is to explain the mechanical model that forms the basis for the punching design equations, to justify the relevance of the provisions and to show their suitability for the design and assessment of structures.
Background to the fib Model Code 2010 shear provisions – part I: beams and slabs
Authors: Sigrist Viktor , Bentz Evan , Ruiz Miguel Fernández , Foster Stephen , Muttoni Aurelio
Published: October 2013

This paper examines the evidence for the one‐way shear model developed for the fib Model Code for Concrete Structures 2010 and provides examples of its application. For the design and analysis for shear, for members with and without shear reinforcement, the fib Model Code 2010 procedures have been developed from physical‐mechanical models that are based on observed behaviour at the meso‐scale level; they represent a significant advance over previous standardized empirical methods. In addition, an approach referred to as “level of approximation” (LoA) is incorporated where advanced models are simplified in a consistent and conservative way such that the designer can select the effort needed to justify their design. To illustrate the practical use of the models and the LoA approach, two examples are presented. The first is a deck slab of a cut‐and‐cover tunnel where design and possible refinements are discussed for a given configuration. The second is a prestressed concrete bridge girder, which is considered for the cases of design and for the analysis of an existing structure.
The state of the art regarding the long‐term properties of recycled aggregate concrete
Authors: Xiao Jianzhuang , Li Long , Tam Vivian W.Y. , Li Hong
Published: October 2013

This paper reviews the long‐term properties of recycled aggregate concrete (RAC), including long‐term strength, shrinkage, creep, carbonation resistance, antifreeze resistance, impermeability, abrasion resistance, alkaline aggregate reactions, sulphate corrosion and fatigue behaviour. Most studies have shown that the long‐term properties of RAC are inferior to those of natural aggregate concrete (NAC), and some researchers have observed that the long‐term properties are better than those of NAC. RAC's long‐term properties are affected by many factors such as recycled coarse aggregate (RCA) replacement percentage, water‐cement ratio, mineral admixtures and mix proportions. The long‐term properties of RAC can be improved through better control of these factors. This paper will be helpful for a comprehensive understanding of and further research on RAC, and provides an important basis and references for the engineering applications of RAC.
Crystal Structure of 3R‐LiTiS2 and its Stability Compared to Other Polymorphs
Authors: Nakhal Suliman , Lerch Martin , Koopman Jeroen , Islam Mazharul M. , Bredow Thomas
Published: October 2013

The crystal structure of 3R‐LiTiS2 was studied with combined experimental and theoretical approaches. The 3R polymorph of lithium titanium disulfide crystallizes rhombohedrally in the well‐known NaCrS2 type with lattice parameters a = 352.98(1) pm, c = 1807.51(3) pm. The relative stability of 3R‐LiTiS2 with respect to other known and hypothetical polymorphs was evaluated theoretically at DFT level employing the hybrid method B3LYP. 3R‐LiTiS2 is less stable than the most common 1T phase (by 4 kJ·mol–1), and is more stable (by 5 kJ·mol–1) than the known phase c‐LiTiS2 thus confirming the importance of this phase for further investigations.
How the Substitution Faraway from NHCs Affects the Structural Features and Catalytic Activity of Dicarbene Dipalladium Complexes
Authors: Ge Kaiqi , Cao Changsheng , Liu Gang , Li Yuling , Zhang Juan , Pang Guangsheng , Shi Yanhui
Published: October 2013

A series of [PdPyCl2]2(di‐NHC) complexes were prepared (di‐NHC are two 1‐(2,6‐dimethylphenyl)imidazolidene molecules bridged by an aliphatic –(CH2)n– linker (n = 3, 4, 5, 6, and 10)). All complexes were fully characterized by NMR spectroscopy and elemental analyses. The crystal structures of four complexes (n = 3, 4, 5 and 6) were determined by X‐ray diffraction. The influence of the distant methyl group on the structural features and catalytic activity with increasing of length of linker was investigated by comparing the results of these 2,6‐dimethylphenyl palladium complexes with those of their known mesityl analogues. X‐ray studies show the distant methyl substitution has big impact on the structure feature of the complexes with the shorter linker between two NHC (ethylene and propylene), but has a little or no effect on that of the complexes with longer linker (butylene and hexylene). Catalytic results of the arylation of styrene show that the remote substitute has big effect on the regioselectivity of the product in all complexes with shorter and longer linkers, but has a limited effect on the yield.
Structure and Properties of [Al4(OH)8(o‐C6H4(CO2)2)2]·H2O, a Layered Aluminum Phthalate
Authors: Reinsch Helge , De Vos Dirk , Stock Norbert
Published: October 2013

The aluminum phthalate [Al4(OH)8(BDC)2]·H2O (where BDC2– stands for phthalate, i.e. 1,2‐benzenedicarboxylate) denoted as CAU‐15 (where CAU stands for Christian‐Albrechts Universität) was synthesized under solvothermal conditions and thoroughly characterized. The structure was determined from X‐ray powder diffraction data using a combination of direct methods and force‐field calculations followed by subsequent refinement by Rietveld methods. The compound is built up by the interconnection of chains of edge‐sharing AlO6 octahedra via phthalate anions, which results in a layered structure. Water molecules could be located between these layers and the dehydration behavior of the compound was studied by means of thermogravimetry and IR spectroscopy.
On Aliovalent Substitution on the Li Site in LiMPO4: an ­X‐ray Diffraction Study of the Systems LiMPO4–M1.5PO4 (= LixM1.5–x/2PO4; M = Ni, Co, Fe, Mn)
Authors: Clemens Oliver , Haberkorn Robert , Springborg Michael , Beck Horst Philipp
Published: October 2013

In this paper we report on the possibility of Li substitution by M2+ to various high degrees in LiMPO4 olivine‐type compounds (M = Ni, Co, Fe, Mn), depending on the kind of transition metal M. The experimental studies were carried through by reacting stoichiometric amounts of LiMIIPO4 and MII1.5PO4 (= MII3(PO4)2) to form compounds of composition LixMII1.5–x/2PO4 (0 ≤ x ≤ 1). A complete solid solution over the whole range of x was found for M = Ni (together with a second order structural transition from orthorhombic to monoclinic for decreasing x), whereas far smaller degrees of dopability of the Li site were found for LiCoPO4 and LiFePO4 (up to compositions of approx. (Li0.8Co0.1)CoPO4 and approx. (Li0.9Fe0.05)FeO4. In addition, the nearly stoichiometric monoclinically distorted olivine‐type compounds with compositions (Li0.42–0.47Co0.29–0.265)CoPO4 and (Li0.14–0.16Fe0.43–0.42)FePO4 could be identified and are described in this article.
The Reducing Ability of Cycloheptatrienyl‐Cyclopentadienyl Zirconium Sandwich Complexes towards Silver(I)
Authors: Tagne Kuate Alain C. , Pinkert Lukas , Freytag Matthias , Jones Peter G. , Tamm Matthias
Published: October 2013

The redox reaction between the cycloheptatrienyl‐cyclopentadienyl zirconium sandwich complexes [(η7‐C7H7)Zr(η5‐C5R5)] [R = H (2a), R = Me (2b)] and three equivalents of silver(I) acetate, Ag(OAc), afforded [(η5‐C5R5)Zr(OAc)3] [R = H (6a), R = Me (6b)] together with elemental silver and 7,7′‐bi‐1,3,5‐cycloheptatriene (5). The molecular structures of 6a and 6b were established by X‐ray diffraction analyses, revealing the presence of monomeric half‐sandwich complexes with three acetato‐κ2O,O′ ligands.