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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
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0001-9937-6072
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0002-3459-2855
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0002-0560-9355
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. Vol. 147, p. 195-206
Keywords [en]
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: urn:nbn:se:ltu:diva-63862DOI: 10.1016/j.engstruct.2017.05.062ISI: 000408073500015Scopus ID: 2-s2.0-85020246241OAI: oai:DiVA.org:ltu-63862DiVA, id: diva2:1107704
Note

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

Available from: 2017-06-10 Created: 2017-06-10 Last updated: 2023-09-05Bibliographically approved
In thesis
1. Anchorage in Concrete Structures: Numerical and Experimental Evaluations of Load-Carrying Capacity of Cast-in-Place Headed Anchors and Post-Installed Adhesive Anchors
Open this publication in new window or tab >>Anchorage in Concrete Structures: Numerical and Experimental Evaluations of Load-Carrying Capacity of Cast-in-Place Headed Anchors and Post-Installed Adhesive Anchors
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Various anchorage systems including both cast-in-place and post-installed anchors have been developed for fastening both non-structural and structural components to concrete structures. The need for increased flexibility in the design of new structures and strengthening of existing concrete structures has led to increased use of various metallic anchors in practice. Although millions of fasteners are used each year in the construction industry around the world, knowledge of the fastening technology remains poor. In a sustainable society, buildings and structures must, from time to time, be adjusted to meet new demands. Loads on structures must, in general, be increased to comply with new demands, and the structural components and the structural connections must also be upgraded. From the structural connection point of view, the adequacy of the current fastenings for the intended increased load must be determined, and inadequate fastenings must either be replaced or upgraded. The current design models are generally believed to be conservative, although the extent of this behavior is not very clear. To address these issues, the current models must be refined to allow the design of new fastenings and also the assessment of current anchorage systems in practice.

The research presented in this thesis consists of numerical and experimental studies of the load-carrying capacity of anchors in concrete structures. Two different types of anchors were studied: (I) cast-in-place headed anchors, and (II) post-installed adhesive anchors. This research focused particularly on the tensile load-carrying capacity of cast-in-place headed anchors and also on the sustained tension loading performance of post-installed adhesive anchors. The overall objective of this research was to provide knowledge for the development of improved methods of designing new fastening systems and assessing the current anchorage systems in practice.

For the cast-in-place headed anchors (I), the influence of various parameters including the size of anchor head, thickness of concrete member, amount of orthogonal surface reinforcement, presence of concrete cracks, concrete compressive strength, and addition of steel fibers to concrete were studied. Among these parameters, the influence of the anchor head size, member thickness, surface reinforcement, and cracked concrete was initially evaluated via numerical analysis of headed anchors at various embedment depths. Although these parameters have considerable influence on the anchorage capacity and performance, this influence is not explicitly considered by the current design models. The numerical results showed that the tensile breakout capacity of headed anchors increases with increasing member thickness and/or increasing size of the anchor head or the use of orthogonal surface reinforcement. However, their capacity decreased considerably in cracked concrete. Based on the numerical results, the current theoretical model for the tensile breakout capacity of headed anchors was extended by incorporating several modification factors that take the influence of the investigated parameters into account. In addition, a supplementary experimental study was performed to verify the numerically obtained findings and the proposed refined model. The experimental results corresponded closely to the numerical results, both in terms of failure load and failure pattern, thereby confirming the validity of the proposed model. The validity of the model was further confirmed through experimental results reported in the literature.

Additional experiments were performed to determine the influence of the concrete compressive strength and the addition of steel fiber to concrete on the anchorage capacity and performance. These experiments showed that the anchorage capacity and stiffness increase considerably with increasing concrete compressive strength, but the ductility of the anchor decreases. However, the anchorage capacity and ductility increased significantly with the addition of steel fibers to the concrete mixture. The test results also revealed that the tensile breakout capacity of headed anchors in steel fiber-reinforced concrete is significantly underestimated by the current design model.

The long-term performance and creep behavior of the post-installed headed anchors (II) was evaluated from the results of long-time tests on adhesive anchors under sustained loads. In this experimental study, adhesive anchors of various sizes were subjected to various sustained load levels for up to 28 years. The anchors were also exposed to several in-service conditions including indoor temperature, variations in the outdoor temperature and humidity, wetness (i.e., water on the surface of concrete), and the presence of salt (setting accelerant) additives in the concrete. Among the tested in-service conditions, variations in the outdoor temperature and humidity had the most adverse effect on the long-term sustained loading performance of the anchors. Based on the test results, recommendations were proposed for maximum sustained load levels under various conditions. The anchors tested under indoor conditions could carry sustained loads of up to 47% of their mean ultimate short-term capacities. However, compared with these anchors, the anchors tested under outdoor conditions exhibited larger creep deformation and failure occurred at sustained loads higher than 23% of their mean ultimate short-term capacities. Salt additives in concrete and wet conditions had negligible influence on the long-term performance of the anchors, although the wet condition resulted in progressive corrosion of the steel. Based on the experimental results, the suitability of the current testing and approval provisions for qualifying adhesive anchors subjected to long-term sustained tensile loads was evaluated. The evaluations revealed that the current approval provisions are not necessarily reliable for qualifying adhesive anchors for long-term sustained loading applications. Recommendations were given for modifying the current provisions to ensure safe long-term performance of adhesive anchors under sustained loads.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017. p. 352
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Headed anchor, Anchor bolt, Adhesive anchor, Concrete cone breakout, Concrete splitting, Pullout loading, Size effect, Member thickness, Anchor head size, Orthogonal surface reinforcement, Concrete Strength, High-strength concrete, Cracked concrete, Steel fiber-reinforced concrete, Sustained loading, Creep behavior
National Category
Civil Engineering
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-66333 (URN)978-91-7790-002-3 (ISBN)978-91-7790-003-0 (ISBN)
Public defence
2017-11-30, F1031, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2017-11-06 Created: 2017-10-31 Last updated: 2023-09-05Bibliographically approved

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Nilforoush, RasoulNilsson, MartinElfgren, Lennart

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