Analytical Calculation of Critical Anchoring Length of Steel Bar and GFRP Antifloating Anchors in Rock Foundation

Nan Yan,Xueying Liu,Cuicui Li,Zhongsheng Wang,Mingyi Zhang,Yongfeng Huang,Xiaoyu Bai,Jun Yan,Zheng Kuang,Desheng Jing,Jose J Muñoz

doi:10.1155/2021/7838042

Nan Yan, Xueying Liu + Show 9 more

Open Access

https://doi.org/10.1155/2021/7838042

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Abstract

Antifloating anchors are widely used during the construction of slab foundations to prevent uplift. However, existing methods for calculating the critical length of these anchors have limited capabilities and therefore require further research. As the mechanisms which govern the displacement and stability of antifloating anchors are closely related to those of piles subject to uplift, a simplified anchor model has been developed based on existing concentric thin-walled cylinder shear transfer models used for pile design. Analytical expressions for the critical length of the steel bar and GFRP (glass fiber reinforced polymer) antifloating anchors in rock are derived accordingly before demonstrating the validity of the method through engineering examples. The research results show that when the length of an antifloating anchor is less than a critical length, shear slip failure occurs between the anchor and surrounding material due to excessive shear stress. When the length of an anchor approaches the critical length, the shear stress gradually decreases to the undisturbed state. If the anchor length is larger than the critical length, the uplift loads are safely transferred to the ground without causing failure. The ratio of elastic modulus between the anchor and rock mass was found to be positively correlated with the critical anchoring length. Because the elastic modulus of GFRP bars is lower than that of steel bars, the critical anchoring length of GFRP bars is greater than that of steel bars under the same anchor-to-rock modulus ratio (Ea/Es). The results show that the proposed calculation method for the critical length of antifloating anchors appears valid and could provide a theoretical basis for the design of antifloating anchors after further refinement.

Highlights

Antifloating anchors are widely used to prevent the uplift of slab foundations as they cause only small stress concentrations, employ simple construction technology, and are low cost [1,2,3]
Zhang et al [8] proposed a time-varying model to describe the loaddeformation characteristics of glass fiber reinforced polymer (GFRP) soil nails during the pullout process by observing the continuous interaction
Bai et al [10] found that there is a critical anchoring length in the steel bar and GFRP antifloating anchor through field drawing test, that is, the anchor will no longer be stressed after reaching a certain depth. is indicates that increasing the anchoring length without limit cannot continuously improve the anchoring performance of the antifloating anchor and will result in the consequence of increasing cost and material waste. erefore, it is of great significance to determine the accurate calculation method of critical anchoring length of antifloating anchor with steel and GFRP bars for saving cost and improving construction efficiency

Summary

Introduction

Antifloating anchors are widely used to prevent the uplift of slab foundations as they cause only small stress concentrations, employ simple construction technology, and are low cost [1,2,3]. Nonmetallic antifloating anchors have the potential to overcome this limitation Within this class of anchor, the glass fiber reinforced polymer (GFRP) type has become prominent due to the advantages of high tensile strength, corrosion resistance, electromagnetic interference resistance, and low cost [4,5,6,7]. Bai et al [10] found that there is a critical anchoring length in the steel bar and GFRP antifloating anchor through field drawing test, that is, the anchor will no longer be stressed after reaching a certain depth. Erefore, it is of great significance to determine the accurate calculation method of critical anchoring length of antifloating anchor with steel and GFRP bars for saving cost and improving construction efficiency. There are few reports on the calculation method of critical anchoring length of steel and GFRP anchors in rock foundation. Compared with an engineering example, the feasibility of the above calculation method is verified, and the influence of the ratio of elastic modulus of anchor to rock mass on the critical anchoring length is discussed

Basic Theory

Example Analysis

Findings

Conclusion