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Nilforoush, R., Nilsson, M. & Elfgren, L. (2018). Experimental Evaluation of Influence of Member Thickness, Anchor-Head Size, and Orthogonal Surface Reinforcement on the Tensile Capacity of Headed Anchors in Uncracked Concrete. Journal of Structural Engineering, 144(4), Article ID 04018012.
Open this publication in new window or tab >>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 (English)In: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541X, Vol. 144, no 4, article id 04018012Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2018
Keywords
headed anchor; anchor bolt; concrete cone breakout; concrete splitting; member thickness; anchor head; surface reinforcement.
National Category
Civil Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-66332 (URN)10.1061/(ASCE)ST.1943-541X.0001976 (DOI)000425620500004 ()2-s2.0-85040823012 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-01-23 (andbra)

Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2018-09-25Bibliographically approved
Al-Gburi, M., Jonasson, J.-E. & Nilsson, M. (2018). Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks (ed.). European Journal of Environmental and Civil Engineering, 22(2), 226-245
Open this publication in new window or tab >>Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks
2018 (English)In: European Journal of Environmental and Civil Engineering, ISSN 1964-8189, E-ISSN 2116-7214, Vol. 22, no 2, p. 226-245Article in journal (Refereed) Published
Abstract [en]

Estimation of restraint is very important for accurately predicting the risk of early thermal and shrinkage cracking in concrete structures. The stress in young concrete is affected by changes in its dimensions during hydration and the restraint imposed by adjoining structures. In concrete culverts, the restraints from existing structures acting upon the first and second casting sections to be cast are different, causing them to exhibit different early cracking behaviour. This work presents a new method for predicting restraint in complex concrete structures using artificial neural networks (ANNs). Finite element calculations were performed to predict restraint in 108 slabs, 324 walls and 972 roofs from second sections of concrete culverts, and the results obtained were used to train and validate ANN models. The ANN models were then used to study the effects of varying selected parameters (the thickness and width of the roof and slab, the thickness and height of the walls, and the length of the culvert section) on the predicted restraint. Mathematical expressions for predicting restraint values in slabs, walls and roofs were derived based on the ANN models’ output and implemented in an Excel spreadsheet that provides a simple way of predicting restraint in practical applications. Restraint values predicted in this way agree well with the results of finite-element calculations

Place, publisher, year, edition, pages
Taylor & Francis, 2018
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-13947 (URN)10.1080/19648189.2016.1186116 (DOI)000427321300006 ()d43d84f0-c1d2-4a54-9629-77677abf0d2c (Local ID)d43d84f0-c1d2-4a54-9629-77677abf0d2c (Archive number)d43d84f0-c1d2-4a54-9629-77677abf0d2c (OAI)
Note

Validerad;2017;Nivå 2;2017-12-04 (svasva)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-04-06Bibliographically approved
Nilforoush, R., Nilsson, M. & Elfgren, L. (2017). Experimental evaluation of tensile behaviour of single cast-in-place anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete. Engineering structures, 147, 195-206
Open this publication in new window or tab >>Experimental evaluation of tensile behaviour of single cast-in-place anchor bolts in plain and steel fibre-reinforced normal- and high-strength concrete
2017 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 147, p. 195-206Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Anchor bolt; Headed anchor; Concrete cone breakout; Splitting failure; Normal-strength concrete; High-strength concrete; Member thickness; Steel fibre-reinforced concrete
National Category
Civil Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63862 (URN)10.1016/j.engstruct.2017.05.062 (DOI)000408073500015 ()2-s2.0-85020246241 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-06-12 (andbra)

Available from: 2017-06-10 Created: 2017-06-10 Last updated: 2018-07-10Bibliographically approved
Nilforoush, R., Nilsson, M., Elfgren, L., Ožbolt, J., Hofmann, J. & Eligehausen, R. (2017). Influence of Surface Reinforcement, Member thickness and Cracked Concrete on Tensile Capacity of Anchor Bolts. ACI Structural Journal, 114(6), 1543-1556
Open this publication in new window or tab >>Influence of Surface Reinforcement, Member thickness and Cracked Concrete on Tensile Capacity of Anchor Bolts
Show others...
2017 (English)In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 114, no 6, p. 1543-1556Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
American Concrete Institute, 2017
Keywords
headed anchor, cone breakout failure, splitting failure, tension loading, surface reinforcement, member thickness, cracked concrete
National Category
Civil Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-66331 (URN)10.14359/51689505 (DOI)000427207500015 ()
Note

Validerad;2018;Nivå 2;2018-04-03 (andbra)

Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2018-10-03Bibliographically approved
Nilforoush, R., Nilsson, M. & Elfgren, L. (2017). Numerical and Experimental Evaluations of Influence of Member Thickness, Anchor Head Size, and Surface Reinforcement on Tensile Breakout Capacity of Anchor bolts. In: Akanshu Sharma, Jan Hofmann (Ed.), Connections between Steel and Concrete: . Paper presented at 3rd International Symposium on Connections between Steel and Concrete, Stuttgart, September 27–29 2017 (pp. 752-764). Stuttgart
Open this publication in new window or tab >>Numerical and Experimental Evaluations of Influence of Member Thickness, Anchor Head Size, and Surface Reinforcement on Tensile Breakout Capacity of Anchor bolts
2017 (English)In: Connections between Steel and Concrete / [ed] Akanshu Sharma, Jan Hofmann, Stuttgart, 2017, p. 752-764Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stuttgart: , 2017
Keywords
Anchor Bolt, Headed Anchor, Pullout Load, Cone Breakout, Concrete Splitting, Member Thickness, Anchor-Head Size, Surface Reinforcement, Concrete Capacity Method
National Category
Civil Engineering Infrastructure Engineering Building Technologies
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65920 (URN)978-3-945773-06-2 (ISBN)
Conference
3rd International Symposium on Connections between Steel and Concrete, Stuttgart, September 27–29 2017
Projects
Anchorage to concrete structures
Available from: 2017-10-03 Created: 2017-10-03 Last updated: 2018-03-26Bibliographically approved
Nilforoush, R., Elfgren, L. & Nilsson, M. (2017). Sustained load performance of adhesive fastening systems in concrete. In: Jaap Bakker; Dan M Frangopol; Klaas van Breugel (Ed.), Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure. Paper presented at 5th International Symposium on Life-Cycle Engineering, IALCCE 2016, Delft, Netherlands, 16-20 October 2016 (pp. 2365-2371). Leiden: CRC Press/Balkema
Open this publication in new window or tab >>Sustained load performance of adhesive fastening systems in concrete
2017 (English)In: Life-Cycle of Engineering Systems: Emphasis on Sustainable Civil Infrastructure / [ed] Jaap Bakker; Dan M Frangopol; Klaas van Breugel, Leiden: CRC Press/Balkema , 2017, p. 2365-2371Conference paper, Published paper (Refereed)
Abstract [en]

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

Place, publisher, year, edition, pages
Leiden: CRC Press/Balkema, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-63451 (URN)2-s2.0-85018639337 (Scopus ID)9781138028470 (ISBN)
Conference
5th International Symposium on Life-Cycle Engineering, IALCCE 2016, Delft, Netherlands, 16-20 October 2016
Available from: 2017-05-19 Created: 2017-05-19 Last updated: 2018-03-26Bibliographically approved
Nilforoush, R., Nilsson, M. & Elfgren, L. (2017). Tensile breakout capacity of cast-in-place headed anchors in concrete. In: Marianne Tange Hasholt (Ed.), XXIIIth Symposium on Nordic Concrete Research & Developement: . Paper presented at 23rd Nordic Concrete Research Symposium, Aalborg, Denmark, 21 – 23 August 2017 (pp. 235-238). Oslo, Norway
Open this publication in new window or tab >>Tensile breakout capacity of cast-in-place headed anchors in concrete
2017 (English)In: XXIIIth Symposium on Nordic Concrete Research & Developement / [ed] Marianne Tange Hasholt, Oslo, Norway, 2017, p. 235-238Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Oslo, Norway: , 2017
Keywords
Modelling, Pullout Testing, Concrete Cone Breakout, Concrete Splitting, Anchor Bolt, Headed Anchor, Fastening System, Member Thickness, Anchor-Head Size, Surface Reinforcement, Structural Design
National Category
Infrastructure Engineering Building Technologies Construction Management
Research subject
Structural Engineering; Construction Engineering and Management
Identifiers
urn:nbn:se:ltu:diva-65907 (URN)978-82-8208-056-9 (ISBN)
Conference
23rd Nordic Concrete Research Symposium, Aalborg, Denmark, 21 – 23 August 2017
Available from: 2017-10-02 Created: 2017-10-02 Last updated: 2018-03-26Bibliographically approved
Nilforoush, R., Nilsson, M., Elfgren, L., Ožbolt, J., Hofmann, J. & Eligehausen, R. (2017). Tensile capacity of anchor bolts in uncracked concrete: Influence of member thickness and anchor’s head size. ACI Structural Journal, 114(6), 1519-1530
Open this publication in new window or tab >>Tensile capacity of anchor bolts in uncracked concrete: Influence of member thickness and anchor’s head size
Show others...
2017 (English)In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361, Vol. 114, no 6, p. 1519-1530Article in journal (Refereed) Published
Abstract [en]

This study evaluated the influence of concrete member thickness and size of anchor head on the tensile capacity and performance of anchor bolts in concrete. Anchor bolts at various embedment depths (hef=50 – 500 mm (1.97 – 19.69 in.)) in concrete members of various thicknesses (H=1.5 – 5.0∙hef) were simulated. Three different sizes of anchor head (small, medium and large) were considered at each anchor embedment depth. The numerical results were compared with predictions from several theoretical and empirical models, including current design models, as well as some test results.

The numerical results show that the concrete cone resistance increases with increasing thickness of concrete member and/or size of the anchor head. Simulations also indicate that current design models generally underestimate the tensile capacity of large anchors.

Two modification factors are proposed to account for the influence of the member thickness and the size of anchor head. Predictions of anchorage capacity using the proposed modification factors have good correlation with the available test results found in the literature.

Place, publisher, year, edition, pages
American Concrete Institute, 2017
Keywords
anchor bolt; concrete cone breakout; pullout loading; size effect; member thickness; head size.
National Category
Civil Engineering Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-66330 (URN)10.14359/51689503 (DOI)000427207500013 ()2-s2.0-85034080496 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-04-03 (andbra)

Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2018-10-03Bibliographically approved
Hösthagen, A., Jonasson, J.-E., Emborg, M. & Nilsson, M. (2017). Thermal Crack Risk Estimations of Concrete Walls: Temperature and Strain Measurements Correlated to the Equivalent Restraint Method. In: Proceedings of the 23rd Nordic Concrete Research Symposium: . Paper presented at 23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017. Oslo, Norway: Nordic Concrete Federation
Open this publication in new window or tab >>Thermal Crack Risk Estimations of Concrete Walls: Temperature and Strain Measurements Correlated to the Equivalent Restraint Method
2017 (English)In: Proceedings of the 23rd Nordic Concrete Research Symposium, Oslo, Norway: Nordic Concrete Federation , 2017Conference paper, Published paper (Refereed)
Abstract [en]

 Self-induced non-elastic deformations in hardening concrete, caused by restrained volume changes due to thermal dilatation and moisture deformations, often leads to cracking. In crack risk analyses, determination of the degree of restraint is vital. One model to estimate the restraint and calculate the thermal crack risk is the Equivalent Restraint Method, ERM. The method has previously been analyzed but needs to be further examined and validated. Recordings of tunnel sections were performed and compared to calculated values by ERM. Satisfying correlation between theoretically estimated and observed temperatures, strains and time of through cracking was achieve which is promising for future implementation and testing of the method.

Place, publisher, year, edition, pages
Oslo, Norway: Nordic Concrete Federation, 2017
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65990 (URN)978-82-8208-056-9 (ISBN)
Conference
23th Symposium on Nordic Concrete Research & Developement, Aalborg, Denmark, 21 - 23 August 2017
Available from: 2017-10-06 Created: 2017-10-06 Last updated: 2018-06-20Bibliographically approved
Nilsson, M., Edelbro, C. & Edström, K. (2016). Adapting CDIO to Civil Engineering: Investigate - Plan - Desig - Construct - Operate and Maintain (ed.). In: (Ed.), Jerker Björkqvist; Kristina Edström; Ronald J. Hugo; Juha Kontio; Janne Roslöf; Rick Sellens; Seppo Virtanen (Ed.), The 12th International CDIO Conference: Proceedings – Full papers. Paper presented at International CDIO Conference : 12/06/2016 - 16/06/2016 (pp. 164-172). Turku
Open this publication in new window or tab >>Adapting CDIO to Civil Engineering: Investigate - Plan - Desig - Construct - Operate and Maintain
2016 (English)In: The 12th International CDIO Conference: Proceedings – Full papers / [ed] Jerker Björkqvist; Kristina Edström; Ronald J. Hugo; Juha Kontio; Janne Roslöf; Rick Sellens; Seppo Virtanen, Turku, 2016, p. 164-172Conference paper, Published paper (Refereed)
Abstract [en]

The aim of this paper is to propose an alternative expression for engineering practice in thecontext of the civil engineering and built environment sector. Our first objective is todemonstrate that the CDIO approach can, with these modifications, be applied in developingcivil engineering and built environment programs. Our second objective is to showcase theadaptability of the CDIO approach, thereby encouraging other thoughtful modifications andtransformations. We outline the ideas underpinning the original expression, and identify therole it plays in the CDIO methodology for curriculum development. Taking these factors intoaccount, a modified expression is proposed to describe the engineering process in civilengineering and built environment. We divide the process into ‘investigation – planning –design – construction – operation and management’. Further, to ‘products, processes andsystems’, we propose the addition of ‘environments’.

Place, publisher, year, edition, pages
Turku: , 2016
Series
Turku University of Applied Sciences, ISSN 1796-9964 ; 45
Keywords
Social sciences - Pedgogical work, Skill development, Self-regulated learning, independent learning strategy, learning objectives, Socialvetenskap - Pedagogiskt arbete
National Category
Infrastructure Engineering Other Civil Engineering
Research subject
Structural Engineering; Mining and Rock Engineering
Identifiers
urn:nbn:se:ltu:diva-39918 (URN)ed8c6ad1-513f-44e5-bd46-8033d6834a6b (Local ID)9789522166104 (ISBN)9789522166104 (ISBN)ed8c6ad1-513f-44e5-bd46-8033d6834a6b (Archive number)ed8c6ad1-513f-44e5-bd46-8033d6834a6b (OAI)
Conference
International CDIO Conference : 12/06/2016 - 16/06/2016
Note
Godkänd; 2016; 20160622 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-03-26Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3459-2855

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