Analysis of the Extended Hollo-Bolt component in concrete-filled steel connections

Cabrera Duran, Manuela (2023) Analysis of the Extended Hollo-Bolt component in concrete-filled steel connections. PhD thesis, University of Nottingham.

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Steel Hollow Sections (SHS) offer many structural, economical and architectural advantages. However, their use is limited due to the difficulties of site bolting using standard bolts. Blind-bolted systems overcome this limitation as they only require access to one side of the hollow section to tighten the bolt. They are also an alternative to site welding. Commercially available blind bolts are restricted to be used in simple connections due to their limited contribution to the stiffness.

The Extended Hollo-Bolt (EHB) is a modified version of the commercially available Lindapter Hollo-Bolt (HB). The EHB uses a nut anchored into a concrete-filled SHS and it has shown to have the ability to be used in rigid or semi-rigid joints. The tensile performance of the EHB has been investigated in terms of strength and failure mode. Three failure modes have been identified in the literature, i.e., bolt failure in tension, column face in bending and the combination of the previous two. Extensive research has been performed by different authors to investigate independently the first two failure modes on the basis of the component method. However, the failure mode where all components can contribute to deformability has not been investigated yet. Therefore, this research aimed at investigating the preload behaviour and the performance of the EHB component when all components can contribute to failure.

Preload experimental and numerical programmes were carried out to identify the effects of concrete hardening in the load relaxation process of the EHB. A total of 9 tests were performed while varying the bolt grade and diameter.

A comprehensive experimental programme was performed to examine the effect of varying the influential parameters on the EHB connection tensile behaviour by testing 28 specimens. The tests involved applying monotonic pull-out load on the EHBs. Specimens with single row of two EHBs were tested to investigate the effect of concrete grade, column face slenderness ratio, bolt gauge distance, anchored length and bolt grade and diameter. Specimens with double rows of EHBs (two in each row) were tested to investigate the effect of bolt pitch distance. The connection strength, stiffness and failure mode were used to evaluate the effect of each parameter.

Abaqus/CAE software was then used to perform numerical analysis. The models were validated with the experimental results, and used to conduct parametric studies within the range of the validity of the model. Hybrid Machine Learning (ML) methods were explored to develop metamodels, defined as the model of a model, based on the data from the experimental and numerical programmes, resulting in a software tool for the prediction of the EHB component behaviour.

Analytical models were also devised to estimate the connection strength and stiffness based on an equivalent spring model with four components: bolt component in tension, column tube wall in bending, and sleeve and anchorage components. The analytical models were validated with experimental and finite element data and they provided reliable results, which can be considered as a benchmark for the design of connections using EHB fasteners.

The main contribution of this work is the proposed metamodels and the mechanical strength and stiffness component model for the EHB component calculation, which can be used for the design of connections made with extended and anchored HBs. These models could be extended and generalized for other similar blind-bolted connections in future research.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Tizani, Walid
Ninic, Jelena
Wang, Fangying
Keywords: Bolts and nuts; Steel; Concrete
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 73152
Depositing User: Cabrera Duran, Manuela
Date Deposited: 31 Jul 2023 04:40
Last Modified: 31 Jul 2023 04:40

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