| 1. |
- Akbarian, Mehdi, et al.
(författare)
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LCA+: Moving LCA into the Pavement Design Space
- 2012
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Ingår i: Proceeding of ACI International Convention.
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Konferensbidrag (refereegranskat)abstract
- The construction, operation, and maintenance of the United States roadway system are responsible for substantial energy and resource consumption. The current system of paved roads in the United States handles a volume of traffic on the order of 8 billion vehicle-miles per day. Due to high energy demand, road transport contributed the most greenhouse gases (GHGs) of any transportation mode in 2007, accounting for 83% of emissions from the transportation sector and 27% of all emissions in the United States. Improving the sustainability of this network requires better technical and decision making strategies starting with the design stage of pavements.While the Mechanistic-Empirical Pavement Design Guide (MEPDG) is being adopted as a design tool throughout the U.S. it lacks the ability to take into account the environmental impacts of pavement systems. Hence, it is necessary to incorporate the performance designs of MEPDG with an environmental assessment tool to merge the structural and environmental aspects of pavement design.The environmental impact of pavements throughout their lifetime is calculated using the life cycle assessment (LCA) technique. Conventional environmental assessments of pavements often overlook use phase related emissions, leading to conclusions based on incomplete results. Studies have empirically shown that an important factor in the life cycle assessment of pavements is the pavement-vehicle interaction (PVI) which describes the effect of pavement properties on vehicle fuel consumption. However, the results of these studies are not conclusive and cannot be generalized to all pavement designs.This research uses a mechanistic approach to rationalize PVI and creates a link between pavement properties and their impacts on fuel consumption. Moreover, a network-level analysis has been performed using the Long Term Pavement Performance (LTPP) program’s databases to calibrate and validate this model. Finally, life cycle assessment is taken into the design space by incorporating MEPDG designs with LCA principles, taking into account the effect of PVI over the pavement’s lifetime. Moreover, evaluation of high performance sustainable pavement systems is enabled by extending the realm of MEPDG to model-based LCA principles. Through this approach, pavement design is enhanced structurally and environmentally constructing the necessary foundations for LCA+.
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| 2. |
- 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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| 3. |
- Coronelli, Dario, et al.
(författare)
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Bond Strength of Highly Corroded Reinforcement and Cover Delamination
- 2012
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Ingår i: Proceeding of the Fourth International Conference on Bond in Concrete. ; 1, s. 469-474
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Konferensbidrag (refereegranskat)abstract
- A recent experimental and analytical research program (Zandi et al., 2011-a, b) provided bond strength values for highly corroded bars. The test program included both main reinforcement and stirrup corrosion. These results must be compared to the rather wide but scattered database of test results in this field. Two relevant sources for comparison are the indications of FIB MC2010, based on the existing literature, and some recently published test results (Regan and Kennedy Reid, 2009). The latter simulated the delamination of the concrete cover by casting the concrete either flush to the bar surface or at mid-barrel i.e. the bars had either no cover or even were partly external to the concrete; the reinforcement was not corroded. The paper summarizes the tests by the authors and develops the comparison with the other studies. The conclusions discuss the choice of bond strength values for the assessment of existing structures and future research outlooks.
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| 4. |
- Coronelli, Dario, et al.
(författare)
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Severely Corroded RC with Cover Cracking
- 2013
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Ingår i: Journal of Structural Engineering. - 0733-9445 .- 1943-541X. ; 139:2, s. 221-232
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Tidskriftsartikel (refereegranskat)abstract
- It is not uncommon that cover cracking, spalling, and delamination occur in many corroding RC structures. Previous research has mainly been concerned with corrosion levels leading to cover cracking along the main reinforcement, whereas corrosion of stirrups is often overlooked. Corrosion phenomena, including stirrup corrosion, were studied in an experimental investigation presented in this paper. High levels of corrosion were reached, up to 20% of the main bars and 34% of the stirrups legs. The occurrence of crack initiation, propagation, and cover delamination were examined. The specimens had the shape of a beam end and were corroded with an accelerated method; an imposed current was used, taking care to keep the current density as low as practically possible for the duration of the laboratory testing. The effects of this process were compared with those of natural corrosion using models from the literature. The location of the bar, middle and corner placement, the amount of transverse reinforcement, and the corrosion level of longitudinal reinforcement and of transverse reinforcement were studied. The results concerning the concrete cracking in the experimental campaign are presented. The crack patterns and widths were analyzed, showing differences between specimens with or without stirrups and whether stirrups were corroding. Finally, the effect of corrosion was simulated as the expansion of corrosion products in a finite-element (FE) model, and the results, mainly the crack pattern and width, were compared with the test results. The conclusions addressed the importance of taking into consideration both high corrosion levels and corrosion of stirrups for the assessment of deteriorated structures.
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| 5. |
- Coronelli, Dario, et al.
(författare)
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Severely Corroded Reinforced Concrete with Cover Spalling: Part 1. Crack Initiation, Crack Propagation and Cover Delamination
- 2010
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Ingår i: RILEM Bookseries. - 2211-0844 .- 2211-0852. ; 5, s. 195-205
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Konferensbidrag (refereegranskat)abstract
- In many corroding RC structures, it is not uncommon that cover spalling and delamination have occurred. Previous research has been mainly concerned with lower corrosion levels leading to cover cracking. Moreover, the main focus of the available knowledge concerns the corrosion of the main reinforcement; while the corrosion of the stirrups is often overlooked. In an experimental investigation, corrosion attack causing crack initiation, propagation and cover delamination are measured. The specimens have the shape of a beam-end and are corroded with an accelerated method. The location of the bar, middle and corner placement; the amount of transverse reinforcement; the corrosion level of longitudinal reinforcement and of transverse reinforcement are studied. The specimens after corrosion are also used in pull-out bond tests; the results are presented in a companion paper subtitled “Part 2. Anchorage Capacity”. The first test results of the ongoing experimental campaign are presented. The crack patterns are analysed, showing differences between specimens with or without stirrups and when stirrups are corroding or not. Finally, the effect of corrosion was simulated as the expansion of corrosion products in a finite element model and the results, mainly the crack pattern, were compared with the test results. The conclusions address the importance of taking into consideration both high corrosion levels and the corrosion of the stirrups for the assessment of deteriorated structures.
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| 6. |
- Fall, David, 1983, et al.
(författare)
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Two-way slabs: Experimental investigation of load redistributions in steel fibre reinforced concrete
- 2014
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 80, s. 61-74
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Tidskriftsartikel (refereegranskat)abstract
- In the design of two-way reinforced concrete slabs, e.g. using the strip or yield line design method, the possibility of redistributing the load between different loading directions is used. The main aim of the present study was to investigate how fibres affect the structural behaviour such as the possibility for redistribution, crack patterns and load-carrying capacity. The investigation was conducted by means of experiments on two-way octagonal slabs, simply supported on four edges, centrically loaded with a point load. The slabs spanned 2.2 m in both directions and the reinforcement amount was twice as large in one direction as in the other, in order to provoke uneven load distribution. Three slabs of each reinforcementconfiguration were produced and tested: conventionally reinforced slabs, steel fibre reinforced slabs and a combination of both reinforcement types. The reaction force on each supported edge was measured on five rollers per edge. A moderate fibre content (35 kg/m3) of double hook-end steel fibres was used. The steel fibres affected the structural behaviour significantly by providing post-cracking ductility and by increasing the ultimate load-carrying capacity by approximately 20%. Most significant, the steel fibres influenced the load redistribution in such a way that more load could be transferred to supports in theweaker direction after cracking. Further, more evenly distributed support reactions were obtained in the slabs containing both reinforcement types compared to the case when only conventional reinforcement was used. The slabs reinforced by steel fibres alone did not experience any bending hardening; however, a considerable post-cracking ductility was observed. Furthermore, the work presented in this paper will provide results suitable for use in benchmarking numerical and analytical modelling methodsfor steel fibre reinforced concrete, as the experimental programme also included extensive testing ofmaterial properties.
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| 7. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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1D and 3D analysis of anchorage in naturally corroded specimens
- 2014
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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
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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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| 8. |
- Flansbjer, Mathias, et al.
(författare)
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Mechanical behaviour of concrete piles affected by sulphate attack
- 2013
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Ingår i: Proceeding of the International IABSE Conference. - 9783857481239 ; , s. 389-392, s. 556-557
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Konferensbidrag (refereegranskat)abstract
- Assessing the remaining service life is vital for the planning of maintenance of concrete constructions in aggressive environments. Here we present results from testing of two concrete piles affected by sulphate attack in marine environment. A multi-method approach going from micro scale to structural level has been applied. The crack propagation was monitored during loading by means of DIC and AE. After the test crack patterns was studied using fluorescence microscopy. Furthermore, non-linear finite element analysis at the structural level was used to study the influence of the chemical attack on the response of concrete piles.
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| 9. |
- Flansbjer, Mathias, et al.
(författare)
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Mechanical behaviour of concrete piles affected by sulphate attack
- 2012
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Ingår i: Proceeding of fib Symposium: Concrete Structures for Sustainable Community, 11 – 12 June 2012, Stockholm, Sweden. ; , s. 389-392
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Konferensbidrag (refereegranskat)abstract
- Assessing the remaining service life is vital for the planning of maintenance of concrete constructions in aggressive environments. Here we present results from testing of two concrete piles affected by combined sulphate and chloride attack in marine environment. A multi method approach going from micro scale to structural level has been applied. The crack propagation was monitored during loading by means of DIC and AE. After the test crack patterns was studied using fluorescence microscopy. Furthermore, non-linear finite element analysis at the structural level was used to study the influence of the chemical attack on the response of concrete piles.
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| 10. |
- Lundgren, Karin, 1968, et al.
(författare)
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Analytical model for the bond-slip behaviour of corroded ribbed reinforcement
- 2012
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Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 8:2, s. 157-169
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion of reinforcement affects the bond mechanism between reinforcement and concrete, and thus the anchorage. Reliable models describing this are needed especially for assessment of the load-carrying capacity of existing structures. This paper presents an analytical one-dimensional model for bond-slip response of corroded reinforcement. The proposed model is an extension of the bond-slip model given in the CEB-FIP Model Code 1990, and is practically applicable for structural analyses to determine the load-carrying capacity of corroded structures. Furthermore, the anchorage length needed to anchor the yield force is calculated from the bond slip, using the one-dimensional bond-slip differential equation. Results of the proposed model are compared to experimental results as well as results from an advanced three-dimensional finite element model. The suggested model is shown to give results that are consistent with the physical behavior.
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