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![Fig. 10. Spring component model for EHB [3].](profile/Manuela-Cabrera/publication/351811467/figure/fig3/AS:1026886134161411@1621840141415/Spring-component-model-for-EHB-3_Q320.jpg)
Steel Hollow Sections (SHS) offer many structural, economical and architectural advantages in multi-storey and high-rise construction. However, their use is not suitable for a wide range of applications due to the difficulties of site bolting as there is limited access to the inner part of the steel section for tightening of standard bolts. Blind b...
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... to the commercial blind bolts in order to increase their tensile stiffness, and increase the bending stiffness of the face of the hollow section. This is the case of the Extended Hollo-Bolt (EHB) developed by Tizani and Ridley-Elis [21] as a modified version of the commercially available 40 Lindapter Hollo-Bolt (HB). The modified fastener, Fig. 1, has an extended bolt shank and an additional nut at the end of the bolt which creates an anchoring effect taking advantage of the concrete around the ...
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... numerical model developed by Pitrakkos [3] for a single EHB assumes three sources of deformability for the bolts in tension component: elongation of the internal bolt shank (k b ), slippage of expanding sleeves (k HB ), and slippage of the mechanical anchorage (k M ). The massless spring model proposed in Fig. 10 is used for the assembly of these individual components to estimate the EHB global force-displacement 475 ...
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... allow for the investigation of the behaviour of the models by visual inspection when the number of important components is low. Fig. 11 and Fig. 12 ...
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... allow for the investigation of the behaviour of the models by visual inspection when the number of important components is low. Fig. 11 and Fig. 12 ...
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... scatterplots for the bolt component in Fig. 11a show that the connection strength is only influenced by the bolt grade. This expected as the failure corresponds to bolt fracture and therefore the strength properties of the bolt define the connection strength, this is also in agreement with Pitrakkos [3]. On the other hand, Fig. 11b shows that all studied parameters have a positive ...
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... scatterplots for the bolt component in Fig. 11a show that the connection strength is only influenced by the bolt grade. This expected as the failure corresponds to bolt fracture and therefore the strength properties of the bolt define the connection strength, this is also in agreement with Pitrakkos [3]. On the other hand, Fig. 11b shows that all studied parameters have a positive correlation with the connection 525 stiffness such that the parameter influence can be rank as: concrete strength > gauge distance > anchored length > bolt ...
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... the case of the column component, a linear relationship between component strength and concrete grade can be observed in Fig. 12a with this parameter being the most influential. In the case of gauge distance and anchored length, parabolic [72] and used to identify the most important model parameters when a relatively small number of sample points is ...
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Citations
... According to Figure 2, the Lindapter Hollobolt is made up of a threaded steel cone and a sleeve with four slots. References [13][14][15][16][17] introduced the application of Lindapter-Hollobolt in the connection of closed section columns with I-shaped or T-shaped beams. The results proved that this blind bolt had sufficient bending stiffness, but the tensile strength was lower than that of the standard bolt. ...
Due to their high bending stiffness, high torsional stiffness, and high local stability, rectangular section members of Al alloy space structures are frequently utilized as load-bearing elements. However, the joint construction is more complex because of the closed cross-section. To join rectangular section members without drilling holes in them, a variety of blind bolts that can be placed and fastened on one side have been devised. The blind bolts researched in this paper is known as BOM bolt. The shear resistance of BOM-bolted Al alloy connections is investigated using shear testing and finite element calculations of individual bolts and bolt groups. According to the test and numerical simulation results, the formulas for the compressive strength of the aluminum plate and the shear capacity reduction factor of BOM-bolted long connections are derived.
... Pitrakkos and Tizani [11] introduce the EHB as a modified version of the Lindapter Hollo-bolt with distinction of containing an elongated internal bolt and the anchor head which is attached to the end (Fig. 1). The added head at the end of the extended shank in the EHB is to make use of the infill concrete and create an anchoring effect to improve the resistance of the connection [2]. ...
... Despite the research that have been done about the EHB and the potential of EHB being used as a rigid connection in SHS design, Cabrera et el. [2] concluded that there are still areas of this topic unexplored yet such as the combined failure mode and the insufficiency of the knowledge at present prevents the EHB to be a safe design of a moment-resistant connection. Cabrera et al. ...
... To overcome these major drawbacks, blind bolt is developed, which can be assembled from only one side of the joint. Cabrera et al. [2] state many different types of ...
The structural hollow sections (SHS) have several advantages comparing with the open sections. However, the application of the SHS in the industry is limited due to the traditional bolt connection and cannot be used for the SHS as the inaccessibility to the inside of section. Several blind bolt systems were developed to overcome this problem and the EHB is the modified version of one of the blind bolt systems.
This project aims to investigate the behaviour of the Extended Hollo-bolt (EHB) connection under combined failure mode with a focus on the influence of the bolt pitch distance by using test data and Finite Element (FE) models and to propose an analytical model for the connection. The EHB connection is between a SHS column filled with concrete and a beam made of an open section. Two rows of EHB were embedded in concrete filled SHS and tested under tension.
FE models were created and validated by tests data and they were used to investigate the aforementioned aims. It is found that pitch distance has a significant influence on the strength of the connection as increase of the pitch distance increases the strength of the connection until a critical value. An analytical model was also proposed for the connection.
... Blind bolts are installed from one side of the tubular section (Figure 1), overcoming the installation challenges given by the lack of space to install a standard nut in the inner part of the steel tube. These connections are under investigation for the development of moment-resisting connections [9][10][11]. In the field of bolted connections in structural engineering, the use of traditional methods such as the component method [12] for the characterisation of new bolting techniques continues to be highly researched [13][14][15]. ...
The development of robust prediction tools based on Machine Learning (ML) techniques requires the availability of complete, consistent, accurate, and numerous datasets. The application of ML in structural engineering has been limited since, although real size experiments provide complete and accurate data, they are time consuming and expensive. On the other hand, validated Finite Element (FE) models provide consistent and numerous synthetic data. Depending on the complexity of the problem, they might require large computational time and cost, and could be subjected to uncertainties and limitation in prediction capability given they are approximations of real-world problems. Hybrid approaches to combine experimental and synthetic datasets have emerged as an alternative to improve the reliability of ML model predictions. In this paper, we explore two hybrid methods to propose a robust approach for the prediction of the Extended Hollo-Bolt (EHB) connection strength, stiffness, and column face displacement: i) supervised ML methods with Data Fusion (DF) where learning is optimised with Particle Swarm Optimization (PSO), and ii) Artificial Neural Networks (ANN) based method with Model Fusion (MF). Based on the analysis of a dataset that combines 22 tensile experimental results with 2000 synthetic datapoints based on FE models, we concluded that using the first method (ML with data fusion and PSO) is the most suitable method for the prediction of the connection behaviour. The ANN based method with model fusion shows to be a promising method for the characterisation of the EHB connection, however, more extensive experimental data is required for its implementation. Finally, a Graphical User Interface (GUI) application was developed and shared in a public repository for the implementation of the proposed hybrid model.
... However, the drawback is that this type of connection requires drilling in the column and using a head plate in the beams, so they are challenging to reconfigure, as in the case of classic bolted structures. Concerning existing research work on this type of connection, Cabrera et al. [46] carried out a state-of-the-art study describing the procedures used for experimental testing and the failure modes produced, also addressing the development of analytical models for their mechanical analysis. Further, Cabrera et al. [47] performed an experimental and numerical analysis of the preload effect on this type of connection. ...
In this review paper, first of all, an analysis of the circular economy and its application to steel structures is carried out. It highlights the need to apply the philosophy of Design for Deconstruction or Design for Disassembly (DfD) from the conception of the structure so that it can be truly reconfigurable. Then, a brief review of the different types of connections for steel structures is conducted, comparing the level of research and development of each of them and the degree of reconfiguration that is possible to obtain. Subsequently, the article focuses on the type of connection using clamps, a key point of this work and on which, to date, there are no state-of-the-art studies. It describes the types of clamps, their principle of operation, the types of connections developed with them, and the results of the different investigations that allow for calculating these types of connections. A summary is also given of how these connection types work according to the geometrical characteristics of the clamp and the bolt so that this review work can serve as a driver for the widespread use of clamp-based connections by researchers and engineers in the design and manufacturing of demountable and reconfigurable steel structures. Finally, some conclusions are given, indicating the advantages and disadvantages of this connection system and future lines of research.
... During the last decades, extensive efforts have been devoted to understand the performance of blind bolted connections and various types of anchored blind bolts have been invented and investigated. Cabrera et al. [16] and Tizani et al. [17] reviewed the studies on Extended Hollo Bolt (EHB) connections as will be discussed in Section 2.4, but they did not cover other types of blind bolts. ...
... Extensive studies have been carried out for EHB connections, including the anchorage of bolt, bolt connected to CFST, T-stub to CFST connection containing a group of bolts and beam-to-column joints [56,57]. Some of the studies were reviewed in the recent papers from Tizani's group [16,17]. ...
... Wan et al. [24] examined the performance of an innovative one-sided bolt with an ellipse head, revealing an acceptable performance compared to ordinary bolts. Extended Hollo-bolts were also demonstrated to be suitable for moment connections [25]. In addition, three prefabrication strategies were suggested by [26], which enable the application of bolted connections to box-column. ...
... Multiple modifications to commercial blind bolts have been proposed by the scientific community to expand the use of blind bolts in moment resisting connections. For instance, connections using the Double-Headed Anchored Blind Bolt (DHABB), introduced by Oktavianus et al. [13] as a modification of the The Ajax-Oneside fastener [14], exhibit higher secant stiffness and lower cyclic deterioration than connections made with the original blind fastener [15]; another example is the Thread-Fixed One-side Bolt (TFOB), which uses a similar concept to the Flowdrill system [16] that has shown to be a good alternative to the traditional bolt and nut in engineering applications [17]; finally, the blind fastener of interest in this article is the Extended Hollo-Bolt (EHB), modified from the HB by Tizani and Ridley-Ellis [18] which has promising potential to be used in moment resisting connections [19][20][21][22]. ...
Extended Hollo-Bolts (EHBs) are blind-bolts that have an extended bolt shank ending with an anchor nut. When used with concrete-filled tubes, the extension and the anchor in concrete serve to significantly enhance the performance of both connection components: bolts in tension and tube face in bending. The enhancements are a result of confining the concrete, preventing the local bucking of the steel tube, and allowing the blind-bolt to achieve tensile strength equal to that of standard bolt-nut fasteners. Overall, the use of the EHB results in providing a bolted connection to hollow sections that is moment-resisting with the possibility of achieving rigid behaviour under certain configuration. This paper summarizes research work done to date on such connections at the University of Nottingham. This includes experimental, numerical , and analytical modelling. The aim of the work is to provide the fundamental understanding of the behaviour of anchored blind bolt connections to concrete filled columns leading to the specification of appropriate design rules allowing the use of such bolted moment resisting connections in practice. The work has proposed analytical models for: connection stiffness, column face-bending strength considering both single and group behaviour of bolt rows, anchored bolt in tension, and anchored bolt under combined tension and shear.
... In order to solve the bolt fastening problem in closed-shape sections, the application of innovative bolts such as blind bolts [24][25][26], flowdrill connectors [27], one-sided bolts [28], and Extended Hollo-Bolt [29] has also been suggested. Various prefabrication techniques were also proposed to resolve the problem of bolt and continuity plate installations in a box-column [30]. ...
In this paper, the behaviour of an innovative connection proposed to connect steel beams to box-columns is investigated experimentally and numerically. This connection eliminates the need for using continuity plate inside the box-column by introducing a new load transfer mechanism. The connection also benefits from the extended end-plate connection in its configuration, allowing for fast erection and cost-effectiveness. Two full-scale specimens were tested under reversed load cycles, and parameters including connection rigidity, ductility, and energy dissipation capacity were evaluated. In all specimens, the plastic hinge formed within the beam, and its location complied with the requirements of extended end-plate connections. The specimens could resist 6% story drift with stable hysteretic curves, revealing their qualification for use in special moment resisting frames (SMF) based on seismic provisions of AISC 341–16. Moreover, the specimens showed high ductility and energy dissipation capacity along with reasonable stiffness degradation. Finally, the unnecessity of continuity plates was investigated, which confirmed that the continuity plates were not required in the proposed connection.
... The tightened shape of the EHB differs from its untightened shape as the sleeve expands while the cone is pushed up during tightening, as 10 shown in Fig. 1. This type of fastener is the subject of an ongoing research programme at the University of Nottingham for its application in moment resisting connections [2,3,4]. ...
Adequate initial bolt preload is necessary to ensure the strength and stiffness of bolted connections. In this study, an experimental torque control method was used to determine the relationship between tightening torque and preload of nine Extended Hollo-Bolt (EHB) blind bolted connections to Concrete-Filled Steel Hollow Sections (CFSHS). In order to obtain the EHB nut factors, which allow to calculate the level of preload for any value of applied torque, torque versus preload curves were drawn based on the experimental results and curve fitting method was carried out. Bolt preload relaxation was also recorded for a period of 7 days while concrete hardening occurred. Additionally, a detailed 3D Finite Element (FE) model of the tightening stage of the EHB was established. The experimental and numerical results show that the nut factor for the EHB is higher than that of standard bolts and bolt relaxation is not affected by the concrete presence during the hardening stage. Adequate friction coefficients were proposed as well as an equation for calculating the residual preload of the EHB.
This paper reports the development and validation of an advanced FE model that can predict the overall behaviour and failure modes of blind bolted T‐stub to unfilled tube (UT), concrete‐filled tube (CFT) and foam‐filled tube (FFT) joints in tension. The joints investigated were made of S355 Square Hollow Sections (SHS) either empty or with concrete or polyurethane infill, connected to a rigid T‐stub using HB 10 hollow bolts. Associated experimental results are used for model validation purposes. The main modelling assumptions and relevant simulation strategies in terms geometric and material modelling are discussed and the resulting models are shown to accurately replicate the experimentally observed response in terms of yield load, failure load, observed failure modes and available ductility of the connections. The favourable performance of connections employing SHS with a polyurethane infill compared to the empty and concrete filled SHS in terms of both strength and ductility is highlighted.
