| 1. |
- af Klintberg, Tord, 1951-, et al.
(författare)
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System för personlig meritering och certifiering för ingenjörer inom den svenska byggsektorn
- 2018
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Rapport (populärvet., debatt m.m.)abstract
- SammanfattningIncitament till systematisk personlig kompetensutveckling för ingenjörer inom byggbranschen saknas. Detta leder till att vi har svårt att upprätthålla tillräckligt hög kompetens och utvecklingstakt i branschen.Frågan är om ett system för meritering kan underlätta och ge större incitament för kontinuerlig kompetensutveckling än vad som finns idag. I ansökningstexten till detta projekt nämns bland annat att: Det är dock väsentligt att ett sådant system är utformat på ett sätt som gör att branschens aktörer finner det relevant och behövligt, samt att det verkligen stärker ingenjörens roll och bidrar till att kompetens bibehålls och utvecklas. I projektet ingår också att beakta ekonomiska och legala aspekter.Arbetet rör först och främst konstruktörer även om slutsatserna kan tillämpas på stora delar av ingenjörskollektivet. Det förefaller finnas brist på kompetenta ingenjörer för centrala positioner i stora projekt med förmåga att upprätthålla kontroll och kommunikation med projektets ingående parter, som byggherre, installationsföretag etc.Ett flertal intervjupersoner hävdar att många stora bygg- och anläggningsprojekt är fragmentiserade med bristande intern kommunikation och att de lider av höga merkostnader. Intervjuade personer inom Trafikverket, med inblick i den egna verksamheten, menar att det kan finnas höga merkostnader även inom de egna projekten. Trafikverket är dock en mycket kompetent byggherre. Det är troligt att mindre byggherrar med lägre kompetens kan ha en värre situation avseende denna typ av kostnader. Många merkostnader skulle kunna begränsas eller undvikas om kompetensnivån höjs inom ingenjörssektorn.Ett meriteringssystem med vidareutbildning, mentorskap mellan seniorer och juniorer, fokuserat på bland annat personlig utveckling skulle kunna höja kompetensnivån bland ingenjörer. Ett meriteringssystem skulle göra konstruktörsyrket mer attraktivt, om det blir tydligt att en oerfaren konstruktör har en karriärväg mot högre expertkompetens.Förbättrade meriter kan valideras genom ett certifieringssystem, som bör fokusera på ingenjörskunskaper såsom konceptuell förståelse och bedömning av bärförmåga och konstruktioners verkningssätt. Systemet ska ha en kontroll- och reklamationsfunktion, som hanterar eventuella kvalitetsproblem hos den certifierade personen. Ett certifieringssystem dokumenterar kompetensnivån för en certifierad och kan därigenom göra det lättare för byggherrar att säkerställa kvalitet i sina beställda projekt.Beträffande värdet av certifiering påvisas i en brittisk rapport att certifiering för testlaboratorier är lönsamt för ingående parter, alltså både för de certifierade och för beställarna. Rapportens slutsats är att det är samhällsekonomiskt lönsamt med certifiering, då den bygger upp förtroende samt minskar risker.Regeringen skulle kunna ge en eller flera myndigheter, exempelvis Transportstyrelsen och/eller Boverket ansvar för personlig kompetensutveckling inom väg och vattenbyggnadssektorn. Denna myndighet skulle alltså få ett liknande ansvar som Socialstyrelsens, som under ett flertal år har medverkat till att utveckla medicinsektorn, med en höjd personlig expertis som resultat. Socialstyrelsens verktyg har här varit personcertifiering (läkarlegitimation). Dessutom ges vidareutbildning, samt handledar- och mentorskap inom medicinsektorn.Trafikverket skulle eventuellt kunna undersöka möjligheten att upphandla certifiering för nyckelkompetenser samt definiera dessa kompetenser i sina egna projekt. Ett liknande förfarande finns hos Stockholms Exploateringskontor när det gäller upphandling av nyckelkompetenser. Om Trafikverket skulle avisera att det skulle ställa särskilda krav på certifiering vid cirka 20 upphandlingar år 2021, så skulle det ge konsultbolagen tid att etablera ett antal certifierade ingenjörer. Dessa projekt kan då jämföras med projekt utan certifiering.Det är förmodligen kostsamt att bygga upp ett svenskt system för personlig certifiering liknande medicinsektorns legitimationssystem. Författarnas förslag är därför att branschen kan börja använda internationella certifieringssystem, exempelvis ”Institution of Civil Engineers” (ICE) och ”Institution of Structural Engineers” (IStructE). ICE är ett bredare system för väg och vattenbyggnadsingenjörer i allmänhet och IStructE certifierar konstruktörer. ICE och IStructE fokuserar på ingenjörs- och marknadskompetens, personlig utveckling och har en kontroll- och reklamationsfunktion samt olika grader avseende medlemmarnas kompetens.De svenska konsult- och entreprenadföretagen har i denna rapports intervjuundersökning visat stort intresse för att låta meritera och certifiera sina konstruktörer, särskilt om stora beställare kommer att efterfråga meriterade konstruktörer. Om internationella certifieringssystem (ICE och IStructE) används, kommer förmodligen svenska konsult- och entreprenörföretag att stärkas på en internationell marknad. Under en övergångstid behövs ett register över befintliga svenska kompetenta ingenjörer så att dessa inte stängs ute från marknaden.Det kommer att ta tid att införa utökad meritering, mentorskap och certifiering. Det är fråga om en kulturförändring i ingenjörssektorn och det behövs då en uthållighet hos branschen, framför allt hos byggherrar. Systemet kommer inledningsvis att medföra ökade kostnader, medan besparingar och vinster kommer i ett senare skede.
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| 2. |
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| 3. |
- Bagge, Niklas, 1987-, et al.
(författare)
-
A multi-level strategy for successively improved structural analysis of existing concrete bridges: examination using a prestressed concrete bridge tested to failure
- 2019
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 15:1, s. 27-53
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a multi-level strategy with increased complexity through four levels of structural analysis of concrete bridges. The concept was developed to provide a procedure that supports enhanced assessments with better understanding of the structure and more precise predictions of the load-carrying capacity. In order to demonstrate and examine the multi-level strategy, a continuous multi-span prestressed concrete girder bridge, tested until shear failure, was investigated. Calculations of the load-carrying capacity at the initial level of the multi-level strategy consistently resulted in underestimated capacities, with the predicted load ranging from 25% to 78% of the tested failure load, depending on the local resistance model applied. The initial assessment was also associated with issues of localising the shear failure accurately and, consequently, refined structural analysis at an enhanced level was recommended. Enhanced assessment using nonlinear finite element (FE) analysis precisely reproduced the behaviour observed in the experimental test, capturing the actual failure mechanism and the load-carrying capacity with less than 4% deviation to the test. Thus, the enhanced level of assessment, using the proposed multi-level strategy, can be considered to be accurate, but the study also shows the importance of using guidelines for nonlinear FE analysis and bridge-specific information.
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| 4. |
- Bagge, Niklas, et al.
(författare)
-
Punching Capacity of a Reinforced Concrete Bridge Deck Slab Loaded to Failure
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Full-scale failure tests of a 55 year old prestressed concrete girder bridge have been carried out to calibrate models for assessment of existing bridges. This paper summarises the outcome from the punching test and analytical analysis according to the model stated in the Eurocode. The experimental load was approximately 2.4 times the code value using measured material properties.
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| 5. |
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| 6. |
- Berg, F., et al.
(författare)
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Anchorage capacity of naturally corroded reinforcement in an existing bridge
- 2012
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Ingår i: Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management, IABMAS 2012, Stresa, Lake Maggiore, 8-12 July 2012. - : CRC Press. ; , s. 2800-2807
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Konferensbidrag (refereegranskat)abstract
- Corrosion of reinforcement is one of the most common causes of deterioration in reinforced concrete bridges. Anchorage, prior to shear and bending moment resistance, is the main uncertainties in the evaluation of the structural behavior of corroded reinforced concrete bridges. Thus, to assess the remaining load-bearing capacity of deteriorated existing bridges, models to estimate the remaining bond and anchorage capacity are needed. Most of our knowledge on the structural behavior of corroded reinforced concrete structures is based on experimental investigations of artificially corroded concrete specimens. In this study, the anchorage capacity of naturally corroded steel reinforcement was investigated experimentally. The test specimens were taken from edge beams of a bridge, Stallbackabron, in Sweden. Since the dimensions and the amount of reinforcement were given on beforehand, it was only the test set-up which could be chosen freely. A test set-up consisting of a four point bending test indirectly supported with suspension hanger was considered to be the best alternative with the least disturbance and influence of the natural damages. Detailed design was done by using a non-linear finite element method. It was seen that the edge beams needed to be strengthened with transverse reiforcement, else they would have failed in a local failure at the suspension hole or in shear. The technique adopted for the strengthening was an internal mounting of steel reinforcement using epoxy as adhesive. The bond and anchorage behavior was examined in tests through measurements of applied load, free-end slip and mid-span deflection. A first test showed that additional measures were needed to ensure anchorage of the strengthening bars. In subsequent tests, they were therefore anchored at the top of the beam with hexagonal nuts and flat steel plates. In two following tests, the beams failed in a splitting induced pull-out failure, i.e. anchorage failure was achieved as wanted.
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| 7. |
- Blomfors, Mattias, 1990, et al.
(författare)
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Evaluation of safety formats for non-linear finite element analyses of statically indeterminate concrete structures subjected to different load paths
- 2016
-
Ingår i: Structural Concrete. - : Wiley. - 1751-7648 .- 1464-4177. ; 17:1, s. 44-51
-
Tidskriftsartikel (refereegranskat)abstract
- To increase the efficiency of new structures and perform safety evaluations of existing structures, it is necessary to model and analyse the non-linear behaviour of reinforced concrete. The applicability of the safety formats in present design codes is unclear for indeterminate structures subjected to loading in several directions. The safety formats in fib Model Code 2010 have been evaluated for a reinforced concrete frame subjected to vertical and horizontal loading and the influence of load history studied. Basic reliability methods were used together with response surfaces to assess the failure probabilities and one safety format did not meet the intended safety level. The results indicate the importance of load history and it is concluded that more research is required regarding how load history influences the safety level of complex structures.
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| 8. |
- Broo, Helén, 1968, et al.
(författare)
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A guide to non-linear finite element modelling of shear and torsion in concrete bridges
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Non-linear finite element (FE) analysis has become an important tool for structural design and assessment of reinforced concrete structures. When shear and torsion are limiting the capacity of a structure, three dimensional non-linear finite element methods often show higher load-carrying capacity compared to conventional analyses; therefore there is much to gain by using these methods, especially at assessment of existing structures. The reason for the higher capacities evaluated are mainly a more favourable load distribution when the structure is analysed in three dimensions and that the fracture energy associated with concrete cracking is included. In order to be able to use these higher capacities in reality, it is important that the modelling method is verified and to be aware of possible limitations. Recommendations are given concerning analysis methods and how a verification can be done, both concerning the capability of the program and concerning the actual FE model. Most important comments and recommendations are:•It is important to note that in FE programs commercially available today, beam elements cannot describe shear cracking and shear failure or reduced torsional stiffness due to cracking. The same applies for the out-of-plane shear in shell elements.•Most often in analysis of bridges, it is enough to assume full interaction between the reinforcement and the concrete. One exception is if the slip is important for the global response or the final failure, as if a shear failure takes place in a region where prestressing is anchored. Then the modelling should include slip between the steel and the concrete.•It is recommended that only the fracture energy of plain concrete is taken into account when defining the softening response of concrete, i.e. when the stress-strain relationship of the concrete is defined. This will yield results on the safe side; i.e. underestimation of the capacity and overestimation of deformations and crack widths.•It is often more stable to perform analyses using deformation control than load control. A method to enable deformation-controlled loading for several point loads by using a separate statically determined arrangement of stiff beams is described.Comments and recommendations are also given concerning how to model important details such as supports and connections, how different loading types can be considered, how to perform the analyses, how to evaluate the results through post-processing, and how to use the results in a safety format context.
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| 9. |
- Broo, Helén, 1968, et al.
(författare)
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Non-linear finite-element analysis of the shear response in prestressed concrete bridges
- 2009
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Ingår i: Magazine of Concrete Research. - : Thomas Telford Ltd.. - 0024-9831 .- 1751-763X. ; 61:8, s. 591 -608
-
Tidskriftsartikel (refereegranskat)abstract
- For the structural assessment of concrete bridges, the non-linear finite-element method has become an important and increasingly used tool. The method has shown a great potential to reveal higher load-carrying capacity compared with conventional assessment methods. However, the modelling method used for reinforced and prestressed concrete members subjected to shear and torsion has been questioned. The aim of this study is to present an analysis method for evaluation of the load-carrying capacity of prestressed concrete bridges, when failure resulting from shear and torsion is the main problem. The modelling method used was previously worked out and verified for shear-type cracking and shear failure. Here, shell elements with embedded reinforcement were used together with non-linear material models, taking into account the fracture energy of cracking plain concrete and the reduction of the concrete compression strength owing to lateral tensile strain. Analyses with the method proposed have shown to predict the shear response and the shear capacity on the safe side. In the work presented here, the load-carrying capacity of a box-girder bridge was evaluated as a case study. The whole bridge was modelled, but only the part that was most critical to shear and torsion was modelled according to the method previously worked out and was combined with beam elements for the rest of the bridge. The case study showed a substantially higher load-carrying capacity for the bridge compared with the assessment with conventional methods. In the evaluation, several possible safety formats were used in combination with the non-linear finite-element method. It was shown that the format using partial safety factors gave unrealistic conservative results; it is more correct to use the semi-probabilistic formats for non-linear finite-element analysis. © 2009 Thomas Telford Ltd.
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| 10. |
- Broo, Helén, 1968, et al.
(författare)
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Reinforced and prestressed concrete beams subjected to shear and torsion
- 2007
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Ingår i: Fracture Mechanics of Concrete and Concrete Structures. - 9780415440660 ; 2, s. 881-888
-
Konferensbidrag (refereegranskat)abstract
- Today, the nonlinear finite element method is commonly used by practicing engineers, although design and assessment for shear and torsion in reinforced concrete structures are still made using methods based on sectional forces. By modelling the shear behaviour, using 3D nonlinear FEM, higher load carrying capacity and more favourable load distribution was shown, compared to conventional analysis. A modelling method using four-node curved shell elements with embedded reinforcement was evaluated in this study. Tests of reinforced and prestressed beams loaded in bending, shear and torsion were simulated. The increase in shear capacity, in addition to the reinforcement contribution, was modelled with a relationship for concrete in tension according to the modified compression field theory and compared with the use of a relationship related to the fracture energy of plain concrete. The results show that evaluations of the load-carrying capacity or crack width will be on the safe side, if only the fracture energy is used to define the concrete in tension.
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| 11. |
- Broo, Helén, 1968, et al.
(författare)
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Simulation of shear-type cracking and failure with non-linear finite element method
- 2007
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Ingår i: Magazine of Concrete Research. - : Thomas Telford Ltd.. - 0024-9831 .- 1751-763X. ; 59:9, s. 673-687
-
Tidskriftsartikel (refereegranskat)abstract
- Today, the non-linear finite element method is commonly used by practising engineers. Simulating the shear behaviour and shear failure of reinforced concrete structures, using three-dimensional non-linear finite element methods, has shown higher load-carrying capacity due to favourable load distribution, compared to conventional analyses. However, the modelling method for reinforced and prestressed concrete members subjected to shear and torsion has not been generally verified. Therefore, the method needs to be further investigated and confirmed to be practically reliable. The aim of this project is to develop, improve and verify a method to simulate the shear response of reinforced and prestressed concrete members. The method should be possible to use for large structures, for example box-girder bridges, subjected to various load actions. Experiments with panels loaded in shear and beams loaded in bending, shear and torsion are simulated by using non-linear FE analysis. The results showed that four-node curved shell elements with embedded reinforcement could simulate the shear response. It is well known that the shear sliding capacity is larger than what can be explained by the reinforcement contribution determined from a truss model. This increase is due to dowel action and aggregate interlock, and has been accounted for in the past by modifying the concrete tension response in models, e.g. according to the modified compression field theory. Results from the analyses show that without any modification, the capacity was underestimated and the average strains, i.e. the crack widths, were overestimated. On the other hand, if the concrete contribution to the shear capacity was considered with the expression from MCFT, the capacity was in many cases overestimated and the average strains underestimated.
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| 12. |
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| 13. |
- 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
-
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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| 14. |
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| 15. |
- Casas, Joan Ramon, et al.
(författare)
-
Safety and Probabilistic Modelling : Sustainable Bridges Background document D4.4
- 2007
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Rapport (refereegranskat)abstract
- The main objective of this background document is to bridge the gap between the most advanced structural assessment techniques based on probabilistic methods and the daily practice of bridge evaluators in the railway agencies, not specifically trained on them and responsible of the load and resistance assessments. To this end, the background document explains and summarizes the basis of the safety assessment using a probabilistic approach, providing simplified methods whenever possible and also providing examples of application in order to make the documents more readable and understandable.The present background document is divided in the following deliverables:D4.4.1 Safety format and required safety levelsD4.4.2 Probabilistic modellingD4.4.3 Probabilistic non-linear analysisD4.4.4 Examination of fatigue safety and remaining fatigue life of structural details andcomponents in steel of railway bridges using probabilistic methodsD4.4.5 Long-term behaviour of subsoil below railway embankments – A simplified predictionmethod of settlements with a probabilistic approach
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| 16. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge building- An effective bridge construction process through an integrated design and construction process
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. - 9788282080439 ; 2014:2, s. 79-82
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Konferensbidrag (refereegranskat)abstract
- This PhD-project aims to develop and industrialise bridge building, in order to achieve a more efficient and sustainable bridge construction process. The advancements of several key areas - materials science and technology, design and analysis methods, production techniques and information and communication technology - have resulted in a vast potential to rationalise the process and renew the designer's role. Initially, the project will define effective bridge construction criteria’s by means of interviews and case-studies. The work should result in an integrated design and production process. This project is a collaborative project, involving: Swedish Transport Administration, WSP and Chalmers.
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| 17. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Industrial bridge construction: Need for a more effective bridge construction process
- 2015
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Ingår i: The Eighth International Structural Engineering and Construction Conference, Sydney, Australia, November 23-28, 2015. - : ISEC Press. - 9780996043717 ; , s. 1115-1120
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Konferensbidrag (refereegranskat)abstract
- Designing for ease of construction is something that is always demanded by contractors and a challenge for the designers. It is widely known that the ability to influence a structure and its future properties is at its greatest in early stages, i.e. the project preparation phase followed by the design phase. Despite the fact that there is an obvious need for knowledge of construction in design work, there is a lack of a consistent and structured transmission of experience between the construction stage and the designing engineers. The results in this project are achieved based upon three standalone studies. A thorough literature review, a meta-analysis of the current research covering effective bridge construction and a study of the current industrial view on how the industry intend to achieve a more effective bridge building process. Based upon these studies it is clear that using a holistic approach and a production oriented design methodology is likely to generate the progress that the construction industry needs.
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| 18. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Integrated project team performance in early design stages – performance indicators influencing effectiveness in bridge design
- 2019
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Ingår i: Architectural Engineering and Design Management. - : Informa UK Limited. - 1745-2007 .- 1752-7589. ; 15:4, s. 249-266
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Tidskriftsartikel (refereegranskat)abstract
- To create multi-functional and integrated project teams, and to adopt a team perspective in the early design stages, it is recognised in the literature that a more effective process is required; one that reduces the probability of costly changes and difficulties during construction. This paper presents an evaluation of project team collaboration during early design and development of construction documents for bridges in Sweden. The purpose was to study key variables influencing the performance of integrated project teams by using importance performance analysis (IPA). A self-evaluation questionnaire addressed clients, contractors, and structural engineering consultants in the Swedish bridge construction industry. The questionnaire addressed three essential cornerstones of value-creation during the engineering design process; culture, structure and competence. These were addressed at three organisational hierarchy levels, the organisation, project, and the individual level. Our results show that increased support and resources are required at the project level for better project team performance. Results further identify that project culture needs to be developed including both collaboration and social relationships as well as project competence, especially the ability to solve mutual issues. This research offers a ‘generalised’ and prioritised view of the challenges in the Swedish bridge construction industry in terms of creating integrated project teams.
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| 19. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Integrated project teams in early design stages - Key variables influencing cost effectiveness in bridge building
- 2016
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Ingår i: 19th IABSE Congress Stockholm, 21-23 September 2016, Challenges in Design and Construction of an Innovative and Sustainable Built Environment. ; , s. 598-606
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Konferensbidrag (refereegranskat)abstract
- The construction industry is usually regarded as a complex, multidisciplinary and project focused environment. It is also regularly identified as a one-of-a-kind nature, hence focus is on the uniqueness of projects rather than in similarities. The results presented in this article are based on questionnaire addressed to clients, contractors, and designers, mainly active within the Swedish infrastructure sector. The purpose is to highlight key-variables influencing cost effectiveness for the organization of integrated project teams, designing of projects, and construction at site. The results indicate that more attention needs to be paid to the actual project setting if to fully gain the benefits from integrated project teams. Further, the results indicates that it is mainly project culture; collaboration and social relationships, and project competence, the ability to solve mutual issues, that needs to be developed.
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| 20. |
- Ekström, Daniel P T, 1976, et al.
(författare)
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Samarbetsprojekt för effektivare brobyggande
- 2014
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Ingår i: Bygg & Teknik. - 0281-658X. ; 2014:7, s. 58-61
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Den svenska anläggningsbranschen har i ett flertal utredningar fått skarp kritik på grund av dålig produktivitet. Forskning visar på samma tendenser i övriga Europa och USA. Vissa mätningar tyder på att byggandet i den svenska anläggningsbranschen har en kostnadsökning som är dubbelt så hög jämfört med övriga branscher under de senaste 20 åren. Låg produktivitet och låg innovationsförmåga i byggbranschen leder till högre kostnader som inte garanterat ger en högre kvalitet. Trenden behöver vändas så att avkastningen på investeringar i vår infrastruktur ökar! Det första steget är att integrera konstruktions- och produktionsprocesserna, vilket ger kortare ledtider för både planering och uppförande av byggnadsverk. Onödigt långa byggtider orsakar störningar för andra aktörer i samhället.I ett pågående doktorandprojekt, som är ett samarbete mellan Trafikverket, WSP och Chalmers, söks möjligheten till att öka produktiviteten inom den svenska anläggningsbranschen. Huvudspåret är att utveckla och industrialisera brobyggandet. En effektivare byggindustri skapar möjligheter till att generera ett mervärde för samhället där mervärdet exempelvis kan motsvaras av att konstruktioner byggs med högre kvalitet till samma kostnad som idag alternativt samma eller högre kvalitet till en lägre kostnad än idag. Bortsett från rena kostnader bör naturligtvis en effektivare byggindustri också se till att lösningar väljs utifrån ett hållbart samhälle men med bibehållen fokus på produktivitet och innovation. En sådan lösning kan variera från själva processen till konstruktionsdetaljer.
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| 21. |
- Ekström, Jonas, 1985, et al.
(författare)
-
Influence of strain softening on spalling of concrete due to blast load
- 2014
-
Ingår i: Nordic Concrete Research. ; 2/2014:50
-
Konferensbidrag (refereegranskat)abstract
- A society needs a certain readiness for different emergency situations, such as explosions within the urban community but also civil safety shelter in the case of war. Therefore, the ability to evaluate and to strengthen existing buildings exposed to new demands is of great importance. Many experiments and numerical analyses indicate that structures of fibre reinforced concrete yield a more favourable response during dynamic load conditions compared to plain concrete. In this study the effects of spalling of a concrete wall subjected to blast loads were studied for plain concrete modelled with an elastic-plastic material model. The results from the analysis show that spalling occur when cyclic loading from a pressure wave gradually increase the plastic strains in the concrete.
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| 22. |
- Ekström, Jonas, 1985, et al.
(författare)
-
Spalling in concrete subjected to shock wave blast
- 2016
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 122, s. 72-82
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies the response in a concrete wall subjected to shock wave blast, leading to spalling failure. This situation is important since spalled-off fragments in protective structures may cause severe injury to the persons or equipment it is supposed to protect. Many theoretical expressions indicates that spalling occurs when and where the tensile strength of a strain-softening material like concrete is reached regardless of the time duration of the applied load. By using a simple uni-axial numerical model, this study shows that spalling instead might occurs when the cyclic response from a blast wave gradually increase the inelastic strains in the concrete. This means that spalling takes place after several loading cycles and not necessarily at the depth where tensile strength is firstly reached. Furthermore, the study shows that the cyclic response in the material model used for numerical simulation has a decisive influence on the position and extent of the resulting spalling crack.
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| 23. |
- Elfgren, Lennart, et al.
(författare)
-
Brottbelastning av en 55 år gammal spännbetongbro i Kiruna - Kalibrering av modeller för tillståndsbedömning : Slutrapport till BBT
- 2015
-
Rapport (refereegranskat)abstract
- En 55 år gammal spännbetongbro med fem spann med längden 121,5 m har provats till brott för att studera och kalibrera metoder för tillståndsbedömning av befintliga broar. Projektet harbidragit till att ge svar på flera av de frågor som ställs beträffande hållbart byggande och uppföljning av befintliga konstruktioner inom BBT - Branschprogram för forskning och innovation avseende byggnadsverk inom transportsektorn. Framför allt adresseras följande områden:A.2.1 Säkerhet, robusthet och sårbarhet – En betydande robusthet finns i den studerade typen av broar och säkerheten mot brott är större än den som erhålls med modellerna i de europeiska betongnormerna.A.2.4 Metodik för individuell bärighetsklassning av broar – En kombination av FE-modellering och analytiska studier baserade på verklig geometri och aktuella materialdata har goda förutsättningar att kunna ge betydligt mer kvalificerade bedömningar av kvarvarande bärförmåga än nu tillämpade metoder.A.2.5 Beständighet och livslängd hos nya byggnadsverk – Projektet ger underlag för förbättrade metoder att bestämma beständighet och livslängd hos spännbetongbroar.A.3.1 Mätmetoder – I projektet har en ny metod för fotografisk töjningsmätning provats. Resultaten har ännu inte hunnit helt utvärderas men de ser lovande ut.A.3.2 Bedömning av tillstånd och livslängd – Projektet ger underlag för förbättrade metoder för bedömning av tillstånd och livslängd.Projektet har hittills redovisats i en doktors- och en licentiatavhandling och i tio tidskrifts- och konferensartiklar.
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| 24. |
- Elfgren, Lennart, et al.
(författare)
-
New technologies to extend the life of elderly rail infrastructure : Deliverable 1.3 in MAINLINE - a project within the EC 7th Framework Programme
- 2015
-
Rapport (refereegranskat)abstract
- There are many traditional technologies available to extend the life of elderly rail infrastructure, some of which are being improved or developed, whilst new technologies continue to emerge.In two earlier reports a benchmark of new technologies was given and assessment methods were presented, ML-D1.1 (2013) and ML-D1.2 (2013). In this report, ML-D1.3, an overview is given of some of the most promising new or updated technologies. Based on the findings, work in the Mainline project has focused on the following two areas for bridges, tunnels and track:- Assessment methods- Repair and Strengthening methodsSome of the methods are still under development and may not yet be available commercially. Hence these are presented on a “for information” basis and as something that may be introduced on a broader scale in a near future.In the report assessment and strengthening of bridges are treated in Chapter 4 and Chapter 5.Tunnels are treated in Chapter 6 and track and earthwork in Chapter 7.The report also includes with five appendices with details of important work that has been donein the MAINLINE project. Appendix A presents results from the assessment and full scale testing to failure of a 50 year old metallic truss bridge. Appendix B presents results from the strengthening by post-tensioning of a concrete trough bridge. Appendix C presents methods to extend life for tunnels. Appendix D proposes methods for the assessment of fatigue andAppendix E, finally, gives a fairly comprehensive list of references on how to extend the life of structures.A Guideline for application of the new technologies is given in ML-D1.4 (2014).
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| 25. |
- Fang, Congqi, 1963, et al.
(författare)
-
Bond behaviour of corroded reinforcing steel bars in concrete
- 2006
-
Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:10, s. 1931-1938
-
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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| 26. |
- Fang, Congqi, 1963, et al.
(författare)
-
Effect of corrosion on bond in reinforced concrete under cyclic loading
- 2006
-
Ingår i: Cement and Concrete Research. - : Elsevier BV. - 0008-8846. ; 36:3, s. 548-555
-
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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| 27. |
- Fang, Congqi, 1963, et al.
(författare)
-
The effect of corrosion on concrete bridges
- 2004
-
Ingår i: Bridge Maintenance, Safety, Management and Cost / edited by Eiichi Watanabe, Dan M. Frangopol, Tomoaki Utsunomiya. - 9058096807
-
Konferensbidrag (refereegranskat)
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| 28. |
- Fernandez, Ignasi, 1984, et al.
(författare)
-
1D and 3D analysis of anchorage in naturally corroded specimens
- 2014
-
Ingår i: Proceedings of the 10th fib International PhD Symposium in Civil Engineering, Université Laval 21 – 23 July 2014, Québec, Canada. - 9782980676222 ; , s. 547-552
-
Konferensbidrag (refereegranskat)abstract
- Corrosion of reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, tests have been carried out on specimens with naturally corroded reinforcements; in this study, the focus is given to the modelling of these specimens. The aim was to evaluate the scope of simpler and more complex bond models to assess the structural behaviour. A comparison of two approaches to model the anchorage behaviour was done: (a) a one-dimensional analysis, where the bond-slip differential equation with a non-linear bond-slip constitutive model is numerically solved, and the mean bond strength as well as the required anchorage length to anchor the yield force are computed. (b) Finite element (FE) analyses were performed using 3D solid elements for concrete, and beam elements for reinforcement, where the interaction was explicitly described using the same bond-slip constitutive model as in approach (a). The results show differences between the two approaches. Each of the modelling alternatives had both drawbacks and advantages; while the more complicated model accounting for more variables led to more realistic results in comparison with observations, the simpler 1D analysis was very fast and efficient.
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| 29. |
- Gottsäter, Erik, et al.
(författare)
-
Comparison of Models for the Design of Portal Frame Bridges with Regard to Restraint Forces
- 2017
-
Ingår i: Structures Congress 2017, Denver, United States, 6-8 April 2017. - Reston, VA : American Society of Civil Engineers. - 9780784480403 ; , s. 326-339
-
Konferensbidrag (refereegranskat)abstract
- In the design of concrete bridges an important aspect is limiting crack widths, since large cracks can lead to e.g. corrosion and affect the bridge functionality. Restraint forces caused by thermal loads and shrinkage will likely constitute a large part of the total forces acting on the bridge in crack width design. In this paper, restraint stresses in portal frame bridges are calculated according to Eurocode with simple hand calculation models, 2D frame models and linear elastic 3D FE-models. The results are then compared and used in Eurocode crack width design methods. Large tensile restraint stresses were found in the transverse direction close to the frame corners, and the required reinforcement amount significantly exceeded the minimum reinforcement prescribed by codes. The results are however unrealistic since the thermal load distribution is simplified, and the crack width formula does not take the reduction of restraint stresses due to cracking into account. Future studies shall therefore determine a more realistic thermal load distribution and the effects of cracking, in order to create a more accurate linear elastic 3D FE design method.
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| 30. |
- Gottsäter, Erik, et al.
(författare)
-
Crack widths in base restrained walls subjected to restraint loading
- 2019
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 189, s. 272-285
-
Tidskriftsartikel (refereegranskat)abstract
- Cracks in concrete structures can have a negative impact on durability and aesthetic appearance. It is therefore important to estimate crack widths before construction, and to use suitable reinforcement amounts to limit crack widths. Crack widths are however hard to predict in restrained structures, as cracking reduces the stiffness, which in turn reduces the restraint and thereby the amount of cracking. In this paper, nonlinear finite element analyses of cracking are performed on base restrained walls mainly subjected to shrinkage. A non-linear material model for concrete and a bond-slip relation for concrete – reinforcement interaction are used. The model does not include the hardening process of concrete but instead applies the load effects on mature concrete, and is validated by comparisons with test results from full scale tests performed in previous research. Additionally, a sensitivity study is made to investigate the influence of certain parameters on crack widths and crack patterns. The intention is to use the model in the development of a model to be used in design of concrete structures which takes restraint effects into account in an improved, yet a simplified way. The results show that the model gives realistic crack patterns, but that it tends to overestimate crack widths and the number of cracks obtained. Therefore, the model is considered to be acceptable.
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| 31. |
- Gottsäter, Erik, et al.
(författare)
-
Crack widths in portal frame bridges subjected to restraint effects
- 2019
-
Ingår i: 20th Congress of IABSE, New York City 2019: The Evolving Metropolis - Report. ; , s. 1101-1105, s. 1101-1105
-
Konferensbidrag (refereegranskat)abstract
- Restraint stresses appear in structural parts which are prevented from adjusting their shape when subjected to e.g. shrinkage or thermal actions. If the restrained stresses are large, cracking might occur, which can affect the durability of the structure. In the case of restraint effects, the reinforcement required in a bridge to limit the crack widths can be difficult to determine, as the magnitude of the restraint stresses depend on the stiffness of the structure. If cracking occurs, the stiffness is reduced and thereby also the stresses. For this reason, in structural parts affected by restraint effects, it can be hard to estimate both the number of cracks that will appear and the resulting restraint stress that governs the crack widths. In this study, crack widths in a portal frame bridge subjected to thermal actions and shrinkage were investigated using non-linear FE analysis. A bond-slip relation was used for concrete-reinforcement interaction, as the resulting crack spacing was unknown. Corresponding analysis was performed using linear elastic material models and hand calculations of crack widths, for two different thermal load cases, and relations between the results from the different methods are presented. The result can lead to the development of a more accurate design model, which would lead to more efficient use of reinforcement.
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| 32. |
- Gottsäter, Erik, et al.
(författare)
-
Measurements and simulation of temperature in a portal frame bridge
- 2018
-
Ingår i: IABSE Symposium, Nantes 2018: Tomorrow's Megastructures. - 9783857481611 ; , s. S24-9-S24-16
-
Konferensbidrag (refereegranskat)abstract
- Since thermal loads can cause cracking, they are important to consider in bridge design. In order to evaluate and develop thermal load cases based on real simulations, models for simulating temperatures can be used. In this paper, a model for thermal simulation is used to simulate temperature in a portal frame bridge outside Lund, Sweden. The results are compared with temperature measurements in 13 locations in the same bridge, which were made during a 12-month period. The results show that although many important material parameters were unknown, the model could recreate both daily and seasonal temperature variations, although it tended to render temperatures about 1°C lower than the measurements, at least during summer. The model can be used in future work in determining thermal load values for the specific bridge type, assuming the model uncertainty is considered by e.g. adding 1°C to calculated load values.
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| 33. |
- Gottsäter, Erik, et al.
(författare)
-
Restraint effects in portal frame bridges : Practical design methodologies and background information
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents methodology, results and conclusions from the PhD-project “Evaluation, modeling and handling of restraint stresses in concrete bridges”, which can be relevant for bridge designers. The project investigated thermal actions in portal frame bridges, and the widths of cracks resulting from restraint effects. The main results and conclusions are given in the summary in Swedish, while the following parts in English presents both results and conclusions, as well as the methodology.The report is developed as a guide for practicing bridge designers on how the load case describing temperature differences between structural parts can be included in design. It also highlights the difficulties and need for further research on determining what the resulting crack widths are and how to design crack distribution reinforcement when cracking is caused by restraint effects.An extensive summary in Swedish is also part of the report.
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| 34. |
- Gottsäter, Erik, et al.
(författare)
-
Simulation of thermal load distribution in portal frame bridges
- 2016
-
Ingår i: IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment.
-
Konferensbidrag (refereegranskat)abstract
- Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. It is shown that the temperature difference between parts which is proposed by Eurocode 1 is overestimated, thus the resulting stress distribution being unrealistic. Using the design method proposed by Eurocode 1 is therefore likely to exaggerate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. Further studies are needed in order to determine proper thermal load values and temperature distributions.
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| 35. |
- Gottsäter, Erik, et al.
(författare)
-
Simulation of thermal load distribution in portal frame bridges
- 2017
-
Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 143, s. 219-231
-
Tidskriftsartikel (refereegranskat)abstract
- Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference between the bridge parts. Factorial design is used in a parametric study to determine the influence of different factors on the temperature difference and the largest reasonable temperature difference obtainable for the chosen weather data. The study shows that the quasi-permanent temperature difference between parts which is proposed by Eurocode 1 is overestimated, causing tensile stresses in the transverse direction to be exaggerated significantly. Using the design method proposed by Eurocode 1 is therefore likely to overestimate the required reinforcement in crack width limit design, which in turn would lead to unnecessary costs and environmental impacts. The results also indicate that the temperature distribution within the bridge is different from what is given in Eurocode load cases, and consequently, the largest tensile stresses appear in other areas of the bridge. A simplified temperature distribution is therefore investigated and shown to give similar results as the detailed thermal simulations.
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| 36. |
- Gottsäter, Erik, et al.
(författare)
-
Tvångseffekter i plattrambroar
- 2020
-
Ingår i: Bygg & teknik. - 0281-658X. ; 112:4, s. 12-17
-
Tidskriftsartikel (populärvet., debatt m.m.)
|
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| 37. |
- Gottsäter, Erik, et al.
(författare)
-
Validation of Temperature Simulations in a Portal Frame Bridge
- 2018
-
Ingår i: Structures. - : Elsevier BV. - 2352-0124. ; 15, s. 341-348
-
Tidskriftsartikel (refereegranskat)abstract
- In the design of bridges, thermal loads are important to take into account since they can cause cracking if the structure or structural part is restrained from changing its size. Accurate thermal load values must therefore be used in bridge design, based on knowledge of the actual temperature distribution in the bridge. This paper presents the validation of a model for temperature simulation, to be used in future work in the determination of temperature differences between deck and abutments in portal frame bridges. The validation is performed by comparing simulated temperatures with temperatures measured at 13 locations in a portal frame bridge during a period of 12 months. The simulation model uses measured air temperature, wind speed and long- and short wave radiation as input to calculate the temperature for every hour in the time period, and includes the soil beside the bridge. The results show that the model was capable of predicting the temperature distribution adequately, and that conservative values of the temperature difference between the structural parts can be obtained by adding no more than a ΔT of 1.5 °C to the simulated temperature difference, depending on the application.
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| 38. |
- Honfi, Daniel, et al.
(författare)
-
Decision support for maintenance and upgrading of existing bridges
- 2017
-
Ingår i: IABSE Conference, Vancouver 2017. - : International Association for Bridge and Structural Engineering (IABSE). - 9783857481536 ; , s. 336-345, s. 336-345
-
Konferensbidrag (refereegranskat)abstract
- Maintenance of transportation infrastructure assets can be relatively expensive, since it does not only include the direct cost of interventions, but also the indirect consequences of traffic disruptions. To make optimal decisions about maintenance actions, including rehabilitation and upgrading, reliable information about the performance of existing structures is needed. However, obtaining such information might require significant efforts and can be done in various ways. The purpose of an ongoing Swedish research project BIG BRO is to develop a framework for a decision support methodology that can be used for implementing maintenance strategies for bridges on a rational basis. The present paper provides a brief overview about the project as well as describes some of the ongoing work.
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| 39. |
- Honfi, Daniel, et al.
(författare)
-
Inspection and monitoring of bridges in Sweden
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report provides an overview about recent research activities and current practice concerning inspection and monitoring of the structural performance of bridges and the related decision-making process. A brief review of common methods of collecting information on structural performance of bridges is presented, followed by a description of the use of the information collected in structural analysis and maintenance planning. An overview about the state of the art is given including recent scientific developments. Finally, the current Swedish practice for bridge management is presented.
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| 40. |
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| 41. |
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| 42. |
- Jensen, Jens S., et al.
(författare)
-
Guideline for load and resistance assessment of existing European railway bridges
- 2007
-
Ingår i: Sustainable Bridges: Assessment for Future Traffic Demands and Longer Lives. - 9788371251610 ; , s. 221-230
-
Konferensbidrag (refereegranskat)abstract
- Many of the European railway bridges are getting close to the end of their service life. At the same time the railway operators demand higher axle loads for freight trains and higher speeds for passenger trains. This requires new and better approaches for assessing both the railway loads and the resistance of railway bridges. The main objective of the "Guideline for load and resistance assessment of existing European railway bridges" is to provide bridge evaluators with the most advanced knowledge regarding methods, models and tools that can be used in the assessment of existing railway bridges in order to get a realistic evaluation of their load carrying capacity and also more accurate evaluation of their remaining service life. This paper gives the general overview of the whole Guideline. Nevertheless, the major focus is placed on the innovative elements proposed in the Guideline, which have been developed due to several research activities performed within WP4.
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| 43. |
- Johansson, Morgan, et al.
(författare)
-
Explosionslast och dynamisk strukturrespons i armerade betongkonstruktioner
- 2023
-
Ingår i: Bygg och Teknik. - 0281-658X .- 2002-8350. ; 115:6
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Med syfte att frigöra attraktiv markyta för ny bebyggelse finns det imånga svenska städer idag ett önskemål att förtäta den befintliga stadsmiljön. En sådan åtgärd kan dock resultera i minskade avstånd mellan byggnader och transportled, vilket kan medföra ökade krav med hänsyn till bland annat explosioner. För att skapa en optimal helhetslösning för sådana olycksscenarion behöver de tre delområdena riskhantering, explosionslast och strukturrespons samordnas på ett korrekt sätt. I dagens explosionshantering finns dock betydande brister bland både riskanalytiker och konstruktörer, något som ofta beror på otillräcklig kommunikation och kunskap.
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| 44. |
- Karlsson, Mats, 1953, et al.
(författare)
-
Methodology for selection of production method in an early stage - improved conceptual design process
- 2017
-
Ingår i: IABSE Conference, Vancouver 2017: Engineering the Future - Report. ; 109, s. 1879-1886
-
Konferensbidrag (refereegranskat)abstract
- The design of buildings and load carrying structures in early stages is a challenging task for a number ofreasons; scant information generally exists and several different requirements involving building structuresshould be managed, including technical, environmental and financial requirements. However, this phase ofthe design process is important and will fundamentally influence the following construction phase, as wellas the entire life of building structures. It is particularly important that the construction phase is properlyconsidered already in the design phase and that the production method selected is suitable for the designof building structures. The purpose of this research has been to improve the design process in theconceptual phase. The findings will highlight the benefits of design for production in bridge engineering.The aim has been to identify examples of practices and work methodologies that are of good caliber in theSwedish bridge construction sector. Early findings show that there exists a divergence between researchfindings and current practices. The research community has presented several participatory methodologiesfor the design process, such as Early Contractor Involvement (ECI) and Integrated Project Delivery (IPD) forthe potential of improving effectiveness in bridge engineering. However, studies of current practices inindustry show that these methodologies are difficult to implement and that there are hiddenconsequences. The processes developed should manage several requirements simultaneously, includingtechnical, environmental, health and safety, and financial. Competencies involved include StructuralEngineering, Architecture and Production Management, in addition to expertise in health and safety,materials science, environmental impact and procurement. Further, the intention is for the processes todeal with verification methods for the proposed conceptual solutions and risk analyses based on qualityassurance. Both new and existing building structures should be considered.
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| 45. |
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| 46. |
|
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| 47. |
- Khouri Chalouhi, Elisa, 1991-
(författare)
-
Optimal design solutions of concrete bridges considering environmental impact and investment cost
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The most used design approach for civil engineering structures is a trial and error procedure; the designer chooses an initial configuration, tests it and changes it until all safety requirements are met with good material utilization. Such a procedure is time consuming and eventually leads to a feasible solution, while several better ones could be found. Indeed, together with safety, environmental impact and investment cost should be decisive factors for the selection of structural solutions. Thus, structural optimization with respect to environmental impact and cost has been the subject of many researches in the last decades. However, design techniques based on optimization haven’t replaced the traditional design procedure yet. One of the reasons might be the constructive feasibility of the optimal solution. Moreover, concerning reinforced concrete beam bridges, to the best of the author knowledge, no study in the literature has been published dealing with the optimization of the entire bridge including both the structural configuration and cross-section dimensions.In this thesis, a two-steps automatic design and optimization procedure for reinforced concrete road beam bridges is presented. The optimization procedure finds the solution that minimizes the investment cost and the environmental impact of the bridge, while fulfilling all requirements of Eurocodes. In the first step, given the soil morphology and the two points to connect, it selects the optimal number of spans, type of piers-deck connections and piers location taking into account any obstacle the bridge has to cross. In the second and final step, it finds the optimal dimensions of the deck cross-section and produces the detailed reinforcement design. Constructability is considered and quantified within the investment cost to avoid a merely theoretical optimization. The wellknown Genetic Algorithm (GA) and Pattern Search optimization algorithms have been used. However, to reduce the computational effort and make the procedure more user-friendly, a memory system has been integrated and a modified version of GA has been developed. Moreover, the design and optimization procedure is used to study the relationship between the optimal solutions concerning investment cost and environmental impact.One case study concerning the re-design of an existing road bridge is presented. Potential savings obtained using the proposed method instead of the classic design procedure are presented. Finally, parametric studies on the total bridge length have been carried out and guidelines for designers have been produced regarding the optimal number of spans.
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| 48. |
- Khouri Chalouhi, Elisa, 1991-
(författare)
-
Optimal design solutions of road bridges considering embedded environmental impact and cost
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Continuous urbanization and population growth are increasing the demand for transportation infrastructure such as bridges. The construction of these structures represents a significant economic investment for public authorities; moreover, the construction sector accounts for a big portion of CO2 emissions. For countries across the world to deliver on their promises of keeping global warming limited, a change in the design philosophy is needed. Within the bridge engineering field, a common design approach can be identified as point-based design. While this approach delivers functional solutions, it often results in an expensive and not climate-friendly solution. Design based on structural optimization represents a good alternative as shown by many researchers in the last decades. However, it has not replaced the traditional design procedure yet. Among the reasons, there is the lack in literature of complete design of realistic structures and the complexity of the proposed optimal solutions. Moreover, a collection of recommendations for designers to assist them in the decision-making process is missing as well. The aim of this work is to cover the gap between theoretical studies and actual application by proposing optimal design solutions of road bridges that are feasible and simple to build. An automated design and optimization procedure is presented as an alternative to the traditional point-based design with the aim of reducing embedded environmental impact and cost. In the field of road bridges, the procedure is applied to three common structures: reinforced concrete beam bridges, reinforced concrete overhang bridge slabs and decks of composite beam bridges. The potential savings obtained by replacing traditional design with the proposed solution are shown through case studies. The use of commercial software commonly employed in design offices and the comparison with existing structures shows the feasibility of the optimal solutions obtained with this approach. Parametric studies are performed to help the potential user make appropriate decisions when performing optimization on these types of structures. As a support in the early design stages instead, recommendations on best solutions are given in the form of graphs and tables. Finally, the relationship between optimal solutions concerning cost and embedded environmental impact is studied for several materials. Material improvements or replacement to further reduce embedded emissions are proposed as well.
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| 49. |
- Lozano Mendoza, Fabio José, 1991, et al.
(författare)
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Experimental validation of two CFD solvers for prediction of blast loading in an urban environment
- 2023
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Ingår i: 26th International Symposium on Military Aspects of Blast and Shock.
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Konferensbidrag (refereegranskat)abstract
- The evolution and propagation of a blast wave in urban environments differ substantially from those of free-field blast waves. The interaction of the blast wave with obstacles along its path gives rise to physical phenomena such as reflection, diffraction and superposition which significantly increase the complexity of the loading. Therefore, for such environments, simplified engineering tools commonly used for predicting shock wave parameters in free-field settings are not sufficient. Indeed, to properly estimate the characteristics of the blast loading for such cases, it may be necessary to use more advanced tools based on computational fluid dynamics (CFD). However, CFD codes must be validated against experimental data before they can be implemented in real life cases. In this study, the open-source CFD solver blastFoam [1] was validated against a scaled (1:5) experimental campaign of an explosion of PETN at a street intersection. The setup of the experiment consisted of four concrete boxes arranged in a 2×2 layout. Multiple locations of the charge were tested. In general, very good agreement between the experimental results and the blastFoam simulations was obtained. The study showed that blastFoam was able to describe the arrival and amplitude of both the main shock wave and secondary waves with a good level of accuracy at multiple points in the configuration.
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| 50. |
- Lundgren, Karin, 1968, et al.
(författare)
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3D Modelling of the bond behavior of naturally corroded reinforced concrete
- 2015
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Ingår i: Extended abstract in “Residual Capacity of Deteriorated Concrete Structures” mini-seminar, 21st of April 2015, Oslo, Norway.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Corrosion of steel reinforcement causes cracking and spalling of concrete cover which affects the bond; this is a crucial factor in deterioration of concrete structures. Earlier, anchorage tests have been carried out on specimens with naturally corroded reinforcements. In an ongoing study, the focus is given to the modelling of thesespecimens. The aim is to evaluate the structural behaviour of the tested naturally corroded specimens. The analyses are performed in the FE program Diana. The frictional bond and corrosion models developed by Lundgren and Zandi are implemented in interface elements to model the interaction between the concrete and reinforcements. The preliminary results of the analysis showed differences in the shear crack pattern in comparison with the experiments. In the analysis, a longer remaining anchorage length was obtained in comparison with the experiment which resulted in a wrong failure mode. The issue might be related to the influence of aggregate interlock in FE analysis.
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