Load-bearing capacity of occlusive high-strength bolt connections
Introduction
As a major connection form in the building structures [1], [2], [3], [4], the bolt connection is usually classified into two types including the ordinary bolt connection and the high-strength bolt connection. Compared with the ordinary bolt connection, the high-strength bolt connection has been wildly used in the building structures recently because of its easier installation, higher bearing capacity, and better anti-fatigue performance. According to the difference of the force transmission patterns, the high-strength bolt connection could be designed as bearing type and friction type. For the bearing type, the bearing capacity of connection depends on the bearing resistance of hole wall and the shear resistance of bolts. For the friction type, the force is transmitted by friction between the faying surfaces of plates. The resistance of the connection of the bearing type is usually higher than the one of the friction type. However, the connection of the bearing type is not suitable for the fatigue load and the dynamic load directly.
To solve the aforementioned limitations of conventional high-strength bolt connections, numerous efforts have been devoted to high-strength bolt connections. He et al. [5] proposed a pre-stressed tube bolted connection whose initial rotational stiffness, ultimate bending resistance, and ductility are better than the conventional high-strength bolt connection. Ma et al. [6], [7] investigated the seismic performance of high-strength bolt connections with slotted holes through experimental studies and found that with the help of the slotted hole, the ductility of the connections is improved obviously. Tizani et al. [8] conducted a testing program to assess the performance of a newly developed blind-bolt connection. Wang et al. and Tizani et al. [9], [10], [11] carried out a series of further researches for the mechanical behavior of the different blind-bolt connections. Annan et al. [12], [13] found that the zinc-based metallized faying surfaces could improve the slip resistance of high-strength bolt connections significantly. In addition, from the structural point of view, the concept of advanced researches has been gradually focused on innovative joints. Guo et al. [4], [14] developed a new type joint system, namely, a bolted ball–cylinder joint. The bolted ball–cylinder joint has a better illuminative effect and could achieve considerable material savings for the space truss structure. Feng and Yong [15], [16], [17] proposed a new concrete-filled stainless steel tubular joint. Compared with the conventional tubular joint, the concrete-filled stainless steel tubular joint has a lot of advantages, including high corrosion resistance, high strength, and stiffness. Guo et al. [18] studied the mechanical behavior of aluminum alloy gusset joints systematically. Recently, the aluminum alloy gusset joint has been widely used in the aluminum single-layer latticed shell.
For the further development of innovative high-strength bolt connections, a new occlusive high-strength bolt (OHSB) connection was proposed in this paper, as shown in Fig. 1. The OHSB connection is usually composed of high-strength bolts, clamp plates, and core plates. The clamp plates and core plates are manufactured with grooves. Due to bolt pretension, the clamp plates and core plates connect with each other tightly. Therefore, the force could be transmitted through the grooves of faying surfaces stably. To meet the requirements of erection error, circular holes are bored in the clamp plates and slotted holes are bored in the core plates. Compared with the conventional high-strength bolt connection, the OHSB connection has a lot of outstanding merits such as attractive appearance, higher bearing capacity, material saving, reduction of high-strength bolts, and rapid construction, etc. These merits provide a widespread application prospect for the OHSB connection.
The main objective of this paper was to investigate the response behavior of OHSB connections subjected to concentric axial tensile forces. To achieve this aim, experimental and analytical studies were carried out on fourteen OHSB connections and four conventional high-strength bolt connections to investigate their load-bearing capacities and failure modes. The experimental results were then discussed and compared to those obtained using the nonlinear finite element program ABAQUS. In addition, a parametric study on the mechanical behavior of OHSB connections was presented in detail.
Section snippets
Specimens
A series of tests on fourteen OHSB connections and four conventional high-strength bolt connections was conducted under axial tensile load. The overall configurations of the conventional connection specimens and the OHSB connection specimens are plotted in Fig. 2, Fig. 3, respectively. The length and width of all the clamp plates were 330 and 160 mm. Eight circular holes were bored in each clamp plate. The length and width of all the core plates were 350 and 180 mm. For the conventional
Failure modes and ultimate loads
The failure modes of the conventional connection specimens are shown in Fig. 10 (a). As the axial tensile load increased, the bolt shanks touched the hole walls tightly. Therefore, large deformation occurred at the hole walls of the clamp plates gradually. When the load exceeded the shear resistance of the high-strength bolts, the shear rupture of bolts occurred at last. The failure modes of the OHSB connection specimens were shown in Fig. 10 (b)–(d). Due to the slotted holes of the core
FE simulations
The aforementioned analyses were mainly focused on the experimental studies. In order to better understand the load-bearing capacity of OHSB connections, the analyses were developed by means of FE method simulations carried out with the non-linear code ABAQUS [22].
Comparison with experimental results and model validation
Validations of the FE modeling were performed against the experimental results on the failure modes and M-φ curves of the OHSB connections.
Parametric studies
In order to develop a further understanding of the load-bearing capacity of OHSB connections, parametric studies were performed by using the proposed FE method. A new FE model was established, as shown in Fig. 22. Mild steel Q235 was selected as the material for the plates. Their constitutive relation was tightly based on the hypothesis of perfect plasticity. The behavioral parameters taken into account were the bolt pretension and the groove size.
Conclusions
On the basis of conventional high-strength bolt connections, a new kind of OHSB connection system was invented. Both the experiments and the FE method were used to study the load-bearing capacity of OHSB connections. The main conclusions could be drawn as follows:
- (1)
The main failure mode of these conventional high-strength bolt connections was the shear rupture of bolts, while the main failure modes of these OHSB connections were the dislocation of plates and the loose of bolts.
- (2)
Compared with the
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