| 1. |
- Casas, Joan Ramon, et al.
(författare)
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Guideline for Load and Resistance Assessment of Existing European Railway Bridges : Advices on the use of advanced methods
- 2007
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Rapport (refereegranskat)abstract
- The bridge assessment in many aspects is very similar to the bridge design. The same basic principles lie at the heart of the process. Nevertheless, an important difference lies in the fact that when a bridge is being designed, an element of conservatism is generally a good thing that can be achieved with very little additional costs. When a bridge is being assessed, it is important to avoid unnecessarily conservative measures because of the financial implications that may follow the decision of ratingthe bridge as deficient. Therefore, the design codes (e.g. EC codes) may not always be appropriate for assessment of existing bridges and some additional recommendations or guidelines are required that will lead to less conservative assessment of theirs load carrying capacity. Such guidelines have been already proposed for assessment of highway bridges in Europe. However, there is a lack of this type of documents that can be applied for the assessment of railway bridges.The present "Guideline for Load and Resistance Assessment of Existing European Railway Bridges - advices on the use of advanced methods" is providing guidance and recommendations for applying the most advanced and beneficial methods, models and tools for assessing the load carrying capacity of existing railway bridges. This includes systematized step-level assessment methodology, advanced safety formats (e.g. probabilistic or simplified probabilistic) refined structural analysis (e.g. non-linear or plastic, dynamic considering train-bridge interaction), better models of loads and resistance parameters (e.g. probabilistic and/or based on the results of measurements) and methods for incorporation of the results form monitoring and on-site testing (e.g. Bayesian updating).Basis for the "Guideline for Load and Resistance Assessment of Existing EuropeanRailway Bridges - advices on the use of advanced methods" is the research work carried out in the work package WP4 of the Sustainable Bridges project combined with the best practical experience and know-how of all the partners involved.The research activities within the work package WP4 have been carried out in the following five groups:− Loads and dynamic effects, with focus on train loads and dynamics (Deliverables D4.3, also referred as SB 4.3 Dynamic (2007), or just SB4.3 (2007));− Safety and probabilistic modelling (Deliverables D4.4, also referred as SB4.4Safety (2007), or just SB4.4 (2007));− Concrete bridges, with focus on non-linear analysis (Deliverables D4.5, also referred as SB4.5 Concrete (2007), or just SB4.5 (2007));− Metal bridges, with focus on riveted bridges (Deliverables D4.6, also referredas SB4.6 Metal (2007), or just SB4.6 (2007));− Masonry arch bridges including soil/structure interaction (Deliverables D4.7,also referred as SB4.7 Masonry (2007), or just SB4.7 (2007)).The results of these activities are reported in corresponding Background Documents (Deliverables) listed above within parenthesis.The main results from the research activities performed and the know-how of all the partners in the specific areas of bridge assessment are tried to be presented in this Sustainable Bridges SB-LRA 2007-11-30 6 (428) Guideline in such a way that the target reader of the Guideline, a structural engineer experienced in assessment of railway bridges, is able to apply them in the everyday practice, without necessity of searching for several specific scientific publications. Nevertheless, in some cases it has been necessary to refer to public available literature and Background Documents prepared in the Sustainable Bridges project.The present Guideline has been prepared aiming to follow somehow the structure of the EC codes and it is divided into 10 chapters and 12 Annexes concerning:− Assessment procedure (Chapter 2);− Requirements, safety formats and limit states (Chapter 3, Annexes 3.1-3.7);− Basic information for bridge assessment (Chapter 4);− Load and dynamic effects (Chapter 5, Annex 5.1);− Concrete bridges (Chapter 6);− Metal bridges (Chapter 7, Annex 7.1);− Masonry arch bridges (Chapter 8, Annexes 8.1 and 8.2);− Foundations and transition zones (Chapter 9);− Improvement of assessment using information from testing and monitoring (Chapter 10, Annex 10.1).In most of the topics related to railway bridges assessment the Guideline uses the current state-of-the-art knowledge and the presently best practice. Nevertheless, in many subjects it propose the use of original methods and models that have been developed, obtained or systematized due to research performed within one of the five groups of work package WP4.
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| 2. |
- Elfgren, Lennart, et al.
(författare)
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Krister Cederwall, 1932-2006 : Minnesord
- 2007
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Annan publikation (populärvet., debatt m.m.)abstract
- Krister Cederwall föddes I Borås den 1 oktober 1932. Efter civilingenjörsexamen I väg- och vattenbyggnad på KTH arbetade han som konstruktör. Han flyttade efter några år till Göteborg och knöts till Chalmers tekniska högskola som forskningsassistent vid Hjalmar Granholms institution för byggnadsteknik där han blev tekn lic 1961. Under åren 1960-65 var han brokonstruktör vid Granholms konstruktionsbyrå och var bland annat med om att utforma broarna i Essingeleden I Stockholm. År 1965 utnämndes han till universitetslektor I betongbyggnad vid Chalmers och disputerade 1971 på en avhandling om stabilitet och långstidsdeformationer I tryckta betongkonstruktioner. När den nya tekniska högskolan I Luleå byggdes upp blev Krister Cederwall dess förste innehavare av professuren I Konstruktionsteknik. Han byggde med stor energi upp nya forskningsinriktningar som byggteknik i kallt klimat och studier av isbärighet och ishållfasthet. Han initierade även studier av massiva betongkonstruktioner och deras sprickbenägenhet. Han arbetade nära samman med byggföretag och knöt adjungerade professorer till högskolan. Han var tidigt ute med att använda sannolikhetsteori för att studera bärighet och att använda brottmekanik för att förstå hur konstruktioner går sönder och hur man undviker spröda brott. När professuren i betongbyggnad blev ledig på Chalmers 1983 efter Anders Losberg flyttade han tillbaka till Göteborg. Hans hjärta fortsatte dock att klappa för Luleå, och han var många gånger på besök för att gästföreläsa och delta i disputationer och licentiatseminarier i ämnen som han en gång initierat. Han blev professor emeritus I januari 1995 och avled den 1 november 2006 vid 74 års ålder.
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| 3. |
- Fang, Congqi, 1963, et al.
(författare)
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Bond behaviour of corroded reinforcing steel bars in concrete
- 2006
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:10, s. 1931-1938
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Tidskriftsartikel (refereegranskat)abstract
- The effect of steel corrosion on bond between steel bars and the surrounding concrete was investigated for different corrosion levels. Both pullout tests and finite element analysis were used and the results from the two were compared. An electrolyte corrosion technique was used to accelerate steel corrosion. For confined deformed bars, a medium level (around 4%) of corrosion had no substantial influence on the bond strength, but substantial reduction in bond took place when corrosion increased thereafter to a higher level of around 6%. It is demonstrated that the confinement supplied an effective way to counteract bond loss for corroded steel bars of a medium (around 4% to 6%) corrosion level. The results of finite element analyses, where it was assumed that rust behaved like a granular material, showed a reasonably good agreement with the experiments regarding bond strength and bond stiffness.
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| 4. |
- Fang, Congqi, 1963, et al.
(författare)
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Effect of corrosion on bond in reinforced concrete under cyclic loading
- 2006
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Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:3, s. 548-555
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic loading can result in severe deterioration in the bond between reinforcing steel bar and the surrounding concrete, especially when the reinforcement is corroded. In this study, tests were carried out for bond stress-slip response of corroded reinforcement with concrete under cyclic loading. Parameters investigated include: corrosion level, confinement, bar type, and loading history. The results revealed that bond behaviour was significantly reduced under cyclic loading. Degradation in bond was significantly less for deformed bars than for smooth bars at the initial loading cycle, but the difference was diminished with loading. The bond reduction was more substantial for unconfined steel bars than for confined bars. The relatively high level of corrosion caused degradation primarily in the initial five cycles, the effect of corrosion being decreased with loading. It was also demonstrated that the cyclic bond stress-slip curves depended on loading history.
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| 5. |
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| 6. |
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| 7. |
- Gylltoft, Kent, 1945, et al.
(författare)
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Tests to determine the modulus of elasticity for CFRP confined concrete columns in stage above the bearing capacity of unconfined concrete
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This study covered investigations into the compressive behaviors of concretes strengthened by CFRP of various qualities. Concrete of three strengths were used - 20, 40 and 60MPa in cubic strength. The confined specimens had the size of diameter: 150, 250, 350mm keeping the shape ratio of height to diameter = 3 unchanged. The wrapping was 3, 5 and 7 layers for small size specimens (150mm x 450mm) and 5 layers for medium size (250mm x 750mm). The results were that no scale effect was observed between two dimension ratios of concrete samples. It was shown that the loading paths in the normalized stress space merge to the single master curve determined by the line of the concrete strength as function of the lateral pressure. From this observation follows, that in the nonlinear region the tangent modulus of the confined concrete E2 and differential Poisson ratio a can be expressed a simple formulae. The non-dimensional parameter is a function of only non-dimensional parameter , where the lateral modulus El = Ej h/R ( - radius of specimen, - thickness of carbon confinement, - modulus of confinement). The confined column breaks when the stress in the composite jacket reaches its critical level.
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| 8. |
- Jansson, Anette M, 1963, et al.
(författare)
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Applying a fracture mechanics approach on FRC beams, material testing and structural analysis
- 2008
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Ingår i: Submitted to Journal of Advanced Concrete Technology.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The presented work has been focused on strain-softening FRC and the interrelationship between material properties and structural behaviour. The main purpose of this work was to establish a procedure for structural analysis of flexural members with a combination of steel fibres and conventional reinforcement. A systematic approach for material testing and structural analysis, based on fracture mechanics, has been used and this covers: (1) material testing; (2) inverse analysis; (3) adjustment of the -w relationship for fibre efficiency; and (4) cross-sectional and structural analysis. The results suggest that the approach used for the material testing provides the necessary properties to perform analyses based on non-linear fracture mechanics. The structural behaviour could be predicted with good agreement with FEM using both bi-linear and multi-linear -w relationships. When comparing the peak loads obtained in the experiments with the results from the analyses, the agreement was good, with a high correlation. This demonstrates the strength of the fracture-mechanics approach for material testing and structural analysis.
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| 9. |
- Jansson, Anette M, 1963, et al.
(författare)
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Applying a fracture mechanics approach to material testing and structural analysis of FRC beams
- 2007
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Ingår i: Conference proceedings for FRAMCOS-6, Catania, Italy June 2007. ; , s. 1491-1496
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Konferensbidrag (refereegranskat)abstract
- The presented work has been focused on strain-softening FRC and the interrelationship between material properties and structural behaviour. The main purpose of this work was to establish a procedure for structural analysis of flexural members with a combination of conventional reinforcement and steel fibres. A systematic approach for material testing and structural analysis, based on fracture mechanics has been used, this covers: (1) material testing; (2) inverse analysis; (3) adjustment of the -w relationship for fibre efficiency; and (4) cross-sectional and structural analysis. The results suggest that the approach used for the material testing provides the necessary properties to perform analyses based on non-linear fracture mechanics. The structural behaviour could be predicted with good agreement, using both FEM and an analytical model, and when comparing the peak loads obtained in the experiments with the results from the analyses, the agreement was good, with a high correlation. Hence, this demonstrates the strength of the fracture-mechanical approach for material testing and structural analysis.
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| 10. |
- Jansson, Anette M, 1963, et al.
(författare)
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Design methods of fibre reinforced concrete: a state-of-the-art review
- 2008
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Ingår i: Submitted to Nordic Concrete Research.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The increasing interest in the use of fibre reinforcement has created a need for established design and analysis methods. Fibre reinforcement is mainly used in applications such as industrial floors and sprayed concrete, although other application areas exist. Apart from increased load carrying capacity, one of the main benefits of adding fibres to concrete is the potential reduction in crack width, which depends on the amount of fibres added and positively affects the durability of the finished structure. By comparing ten design methods proposed by technical committees, this paper provides a basis for further research aimed at developing a common design basis. Evaluation is based on the way the fibre capacity is considered. In addition, a “good” design method should also consider all (or most) design situations. It was found that, for design, the Italian proposal provides comprehensiveness. However, some amendments are needed, e.g. a suggestion is that the proposed formula for calculating crack width/crack spacing be modified to also consider the residual tensile strength.
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