| 1. |
- Elfgren, Lennart, 1942-, et al.
(författare)
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Assessment of Fasteners to Concrete : A Tribute to Rolf Eligehausen
- 2017
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Ingår i: Connections between Steel and Concrete. - Stuttgart. - 9783945773062 ; , s. 1294-1302
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Konferensbidrag (refereegranskat)abstract
- Some examples are given of assessment of fastenings to concrete structures and the work started by Rolf Eligehausen in fib Task Group 2.9 “Fastenings to structural concrete and masonry”. Studies have been made on e.g. the influence of creep on adhesive anchors and of surface reinforcement and size effects on headed anchors.
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| 2. |
- Nilforoush, Rasoul, et al.
(författare)
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Anchorage capacity and performance in plain and steelfibre-reinforced-concrete
- 2020
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Ingår i: 1st IABSE Online Symposium 2020. - : International Association for Bridge and Structural Engineering (IABSE). ; , s. 700-709
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Konferensbidrag (refereegranskat)abstract
- Nowadays, prefabricated concrete components made from Steel-Fiber-Reinforced Concrete (SFRC) are widely used in the construction industry. These components are often connected to existing or new structural elements through various fastening systems. Previous studies have shown that the addition of steel fibers to concrete mixture substantially improves the fracture properties of concrete. To date, however, rather limited research is available on the behavior of fastening systems in SFRC. To improve the current knowledge of fastening systems to SFRC structures, a pilot experimental study is carried out on cast-in-place anchor bolts embedded in Plain Concrete (PC) and SFRC members. In this study, the influence of the presence of steel fibers and concrete compressive strength on the anchorage capacity and performance is evaluated. Furthermore, the applicability of current design methods is evaluated for anchorage systems in SFRC.
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| 3. |
- Nilforoush, Rasoul, et al.
(författare)
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Experimental Evaluation of Influence of Member Thickness, Anchor-Head Size, and Orthogonal Surface Reinforcement on the Tensile Capacity of Headed Anchors in Uncracked Concrete
- 2018
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Ingår i: Journal of Structural Engineering. - : American Society of Civil Engineers (ASCE). - 0733-9445 .- 1943-541X. ; 144:4
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Tidskriftsartikel (refereegranskat)abstract
- Cast-in-place headed anchors with different head sizes embedded in plain and reinforced concrete members of various thicknesses were subjected to pullout tests. The influence of member thickness, size of the anchor head, and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts was evaluated. The member thickness varied from 1.5 to 3.0 times the anchor embedment depth and headed anchors with small, medium, and large heads were tested.The experimental results of the present study showed that increasing member thickness and/or the use of orthogonal surface reinforcement lead to increased anchorage capacity and anchorage ductility, whereas the anchorage stiffness decreases slightly. In contrast to the anchorage ductility, the tensile breakout resistance and the anchorage stiffness increase significantly with increasing size of the anchor head.The experimental results corresponded closely to numerical results from a previous study (Nilforoush et al. 2016 a & b), which suggested a modified model incorporating several modification factors for improving the predictive capability of the Concrete Capacity (CC) method. In the present study, these factors yielded improved prediction of the tensile breakout capacity of the tested headed anchors.
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| 4. |
- Nilforoush, Rasoul, et al.
(författare)
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Experimental evaluation of tensile behaviour of single cast-in-place anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete
- 2017
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Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 147, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- Cast-in-place anchor bolts embedded in plain and steel fibre-reinforced normal- and high-strength concrete members were subjected to monotonic tensile loads. The influence of the concrete member thickness, concrete strength, and the addition of steel fibres to the concrete mixture, on the anchorage capacity and performance was evaluated. The experimental results were evaluated in terms of anchorage capacity, anchorage ductility and stiffness as well as failure mode and geometry. Furthermore, the validity of Concrete Capacity (CC) method for predicting the tensile breakout capacity of anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete members was evaluated.The anchorage capacity and ductility increased slightly with increasing member thickness, whereas the anchorage stiffness decreased slightly. In contrast to the anchorage ductility, the anchorage capacity and stiffness increased considerably with increasing concrete compressive strength. The anchorage capacity and ductility also increased significantly with the addition of steel fibres to the concrete mixtures. This enhanced capacity and ductility resulted from the improved flexural tensile strength and post-peak cracking behavior of steel fibre-reinforced concrete.The average ratio of measured strengths to those predicted by the CC method for anchors in plain concrete members was increased from 1.0 to 1.17 with increasing member thickness. In steel fibre-reinforced concrete, this ratio varied from 1.29 to 1.51, depending on the member thickness and the concrete strength.
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| 5. |
- Nilforoush, Rasoul, et al.
(författare)
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Fracture energy of concrete for bridge assessment
- 2020
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Ingår i: 1st IABSE Online Symposium 2020. - : International Association for Bridge and Structural Engineering (IABSE). ; , s. 692-699
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Konferensbidrag (refereegranskat)abstract
- In numerical assessments of concrete bridges, the value of the concrete fracture energy GF plays an important role. However, mostly the fracture energy is only estimated based on the concrete compressive strength using empirical formulae. In order to study methods to determine the concrete fracture energy for existing bridges, tests were carried out on 55-year-old concrete from a bridge tested to failure in Kiruna in northern Sweden. Uniaxial tensile tests are performed on notched cylindrical concrete cores drilled out from this and other bridges. In the paper, different methods to determine the concrete fracture energy are discussed and recommendations are given for assessment procedures.
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| 6. |
- Nilforoush, Rasoul, et al.
(författare)
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Influence of Surface Reinforcement, Member thickness and Cracked Concrete on Tensile Capacity of Anchor Bolts
- 2017
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Ingår i: ACI Structural Journal. - : American Concrete Institute. - 0889-3241 .- 1944-7361. ; 114:6, s. 1543-1556
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Tidskriftsartikel (refereegranskat)abstract
- An extensive numerical study was carried out to evaluate the influence of concrete member thickness and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts in uncracked concrete members. Anchor bolts at various embedment depths (hef=50 to 300 mm (1.97 to 11.81 in.)) in unreinforced and reinforced concrete members of various thicknesses (H=1.5 – 5.0∙hef) were simulated. The reinforced concrete slabs were considered to be lightly-reinforced and over-reinforced to evaluate also the influence of amount of reinforcement. Furthermore, the behavior of anchor bolts at various embedment depths in pre-cracked reinforced concrete members was numerically investigated. The numerical results were compared with predictions from current design models including the Concrete Capacity (CC) method.The numerical results show that in uncracked concrete the tensile capacity of anchor bolts increases up to 20% and the anchorage behavior becomes more ductile with increasing member thickness or by having surface reinforcement. The numerical results also show that the CC method underestimates the tensile capacity of deep anchors (hef≥200 mm (7.87 in.)), while it slightly overestimates the capacity of short anchors (hef≤100 mm (3.94 in.)) in thin unreinforced members. It was also found that the over-reinforced concrete does not improve the anchorage capacity and performance any further than the lightly-reinforced concrete. Based on the numerical results, several recommendations are proposed to account for the influence of member thickness, surface reinforcement and cracked concrete. Further experimental studies are ongoing to verify and generalize the recommendations of this study.
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| 7. |
- Nilforoush, Rasoul, et al.
(författare)
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Numerical and Experimental Evaluations of Influence of Member Thickness, Anchor Head Size, and Surface Reinforcement on Tensile Breakout Capacity of Anchor bolts
- 2017
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Ingår i: Connections between Steel and Concrete. - Stuttgart. - 9783945773062 ; , s. 752-764
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Konferensbidrag (refereegranskat)abstract
- The influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of cast-in-place headed anchors in uncracked concrete was studied both numerically and experimentally. The aim of this paper is to form a background for developing improved methods for the design of new fastenings as well as the assessment of current anchorages in practice. For this purpose, anchor bolts at various embedment depths (hef=50–500 mm) were simulated in plain and reinforced concrete members of various thicknesses (H=1.5–5.0∙hef). Three different head sizes of anchor bolts (i.e. small, medium and large) were also considered at each anchor embedment depth. Furthermore, to verify the numerical findings, a series of anchor pullout tests were carried out at which the testing parameters were similar to those in the numerical study.Numerical and experimental results show that the tensile breakout capacity of anchor bolts increases by increasing the member thickness or if surface reinforcement is present. The anchorage capacity further increases with increasing the anchor head size. The anchorage behavior becomes ductile by increasing member thickness or by having surface reinforcement, whereas it becomes stiff and more brittle by increasing the size of anchor head. To account for the influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of headed anchors, the CC method was modified and extended by incorporating three modification factors.
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| 8. |
- Nilforoush, Rasoul, et al.
(författare)
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Numerical Modelling and Experimental Verification of Pullout Loading of Anchor Bolts in Reinforced Concrete Structures
- 2016
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Ingår i: IABSE CONGRESS, STOCKHOLM, 2016. - CH - 8093 Zürich, Switzerland. - 9783857481444 ; , s. 2172-2178
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Konferensbidrag (refereegranskat)abstract
- The aim of this study is to provide a numerical model which can realistically present the failure load and failure mechanism of pullout loaded anchor bolts (headed studs) in reinforced concrete structures. The numerical analysis is carried out through a three-dimensional finite element (FE) code based on the Microplane constitutive law. The intension is to calibrate the FE model and to verify the numerical results against available test results. The calibrated FE model is intended to be used for an ongoing study to evaluate the influence of member thickness, surface reinforcement and size of anchor head on the tensile capacity and performance of anchor bolts.The simulation results showed very good agreements with the available test results. The objectivity of numerical modelling in respect to the size of finite elements as well as the defined boundary conditions was confirmed by additional numerical analyses.
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| 9. |
- Nilforoush, Rasoul, et al.
(författare)
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Sustained load performance of adhesive fastening systems in concrete
- 2017
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Ingår i: Life-Cycle of Engineering Systems. - Leiden : CRC Press/Balkema. - 9781138028470 ; , s. 2365-2371
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Konferensbidrag (refereegranskat)abstract
- Influence of several sustained loading levels and various in-service conditions on the long-term performance of adhesive bonded anchors are experimentally evaluated. Adhesive bonded anchors with 16 and 20 mm diameters were subjected to sustained load levels between approximately 23 and 70% of their mean ultimate short-term capacities. The creep deformation of tested adhesive anchors was monitored over approximately 28 years. The tested in-service conditions were indoor, outdoor, wetness (i.e. water on the surface of concrete) and presence in the concrete of salt additives. The tested adhesive anchors in the indoor conditions could carry sustained loads up to 47% of their mean ultimate short-term capacities. However, the adhesive anchors under outdoor environment showed larger creep deformations and failure occurred for anchors subjected to sustained loads higher than 23% of the anchors’ mean ultimate short-time capacities. Wet condition seemed to have no adverse effect on the anchors’ creep behavior, but caused corrosion of the steel in the anchors over time. Salt additives in concrete had negligible influence on the long-term performance and creep deformation of the tested adhesive anchors
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| 10. |
- Nilforoush, Rasoul, et al.
(författare)
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Tensile breakout capacity of cast-in-place headed anchors in concrete
- 2017
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Ingår i: XXIIIth Symposium on Nordic Concrete Research & Developement. - Oslo, Norway. - 9788282080569 ; , s. 235-238
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Konferensbidrag (refereegranskat)abstract
- The influence of member thickness, size of anchor head, and orthogonal surface reinforcement on the tensile breakout capacity of cast-in-place headed anchors was studied both numerically and experimentally. The aim of this paper is to form a background for developing improved methods for the design of new fastening systems as well as the assessment of the current anchorage systems in practice. Numerical and experimental results showed that the tensile breakout capacity of anchor bolts increases by increasing the member thickness or if surface reinforcement is present. Furthermore, the anchorage capacity increases with increasing the anchor head size.
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