The purpose of this paper is to investigate analytically the fully grouted rock bolt interaction with grout and rock in pullout test and to determine the load-displacement curve of the bolt head (beginning of the bonded section). Usually, the pullout test output is only the load-displacement curve. This paper discusses how to use this curve to determine the bolt-grout-rock interaction. For modeling bolt-grout interface behavior, coupling (compete for bonding), partial decoupling, decoupling with the residual shear strength, and complete decoupling have been considered. With increasing the applied load, two possible cases including complete pullout and bolt shank yielding are considered. Based on experimental results, a model for the shear stress along a fully grouted bolt is assumed. According to this model, the distribution of axial stress in the bolt and displacement of the bolt head is determined. It is also assumed that the bolt is sufficiently long, which is usually used in underground excavations. Based on the presented analytical method, the bolt head load-displacement curve is determined by assuming input parameters. This curve is compared with a pullout test result.

For making rivet and bolt connections, making a hole is necessary. While basic S-N graph can be extracted from design documents, analysis of stress can be used for two different approaches. The first approach is the theoretical derivation of analytical relations with simplified assumptions like planar stress or uniform bolt load distribution. The other one is the numerical simulation using robust codes like Abaqus software. By using these two approaches, residual stress distribution around the hole can be extracted in various conditions. In this experiment, an aluminium 2024-T3 plate with 3.2 mm thickness is considered. The stress analysis results and basic S-N graph were combined and discursive S-N graphs were obtained for different cold-expanded bolted holes. These graphs were compared with experimental data in several steps. First, the bolt fastening was considered. In the second step, cold expansion was considered and in the final step, the effects of fastening bolts and nuts and cold expansion was considered simultaneously. At last, a comparison between various steps was drawn. The results of this study showed that this new analytical method on distribution of residual stresses around cold expansion holes is as effectiveness as old methods.

Precise investigation of the connections in a steel structure is important, and inaccuracy in the design and implementation of connections not only does cause failure in the connection, but also has a devastating effect on other members of the structure. Bolted end plate connections are commonly used in steel structures. There are two types of beam-to-column flange connections, four-bolt and eight-bolt. The four-bolt connection is used for low anchor values and the eight-bolt connection is used for large bending anchor values. In this study, the cyclic behavior of the restrained beam-to-column connections with end plate under cyclic loading has been evaluated. In the calculations, all of the parameters affecting the behavior of this connection have been investigated and solutions are proposed to reach the maximum connection capacity. Since the behavior of this connection depends on several factors, two general models of beam connection to different columns with beams of 30 and 40 cm depth are considered for research purposes. The thickness of end plate, shape of end plate, thickness of the column flange, strength or material of the bolts, the necessity of using continuity plate, stiffener and doubler plate are among the parameters considered in the analyzes. According to the results of this study, the use of a thin-walled end plate leads to local buckling of plate. The use of continuity plate is very important and prevents local buckling in the panel zone. Also, in cases where the thickness of the column web is low, the use of a doubler plate will also be necessary. In addition, the use of a stiffener improves the flexural strength of the section.

Considering the importance of composite connections, this study evaluated two experimental and numerical methods for bolted joints of epoxy-glass composite plates. Then, using an artificial neural network, a model was defined between experimental and numerical results. The results of this study showed that the maximum force tolerated by bolted joints was various at several distances and its maximum value was tolerated by the connection at 4cm equal to 5332 and 7093N, for two specimens. Comparison of numerical and experimental results of Von-Mises stress for distances of 2, 3, and 4cm was done. The Von-Mises stress for these distances was 313.59, 217.57, and 177.71MPa, respectively. In this research, the connection of epoxy-glass plates using M6-bolt was studied, and by increasing the coverage of two composite plates, the Von-Mises stress in the connection was raised. Concerning the determination of the stress measuring path, from the internal edge of the critical notch to the end of the defined range with a smaller mesh, the Von-Mises stress was extracted, which in distance equal to 3cm with the vertical arrangement, maximum stress was equal to 513MPa. The minimum stored energy of the numerical method in the connection was related to the bolted joint with a two-bolt in the vertical position.

In this work, the effect of rock bolt angle on the shear behavior of Rock Bridges is investigated using the particle flow code in two dimensions (PFC2D) for three different Rock Bridge lengths. Firstly, the calibration of PF2D is performed to reproduce the gypsum sample. Then the numerical models with the dimensions of 100 mm * 100 mm are prepared. The Rock Bridge is created in the middle of the model by removal of the narrow bands of discs from it. The uniaxial compressive strength of the Rock Bridge is 7. 4 MPa. The Rock Bridge lengths are 30 mm, 50 mm, and 70 mm. The rock bolt is calibrated by a parallel bond. The tensile strength of the simulated rock bolt is 360 MPa. One rock bolt is implemented in the Rock Bridge. The rock bolt angles related to the horizontal axis are the changes from 0 to 75 degrees. Totally, 18 models are prepared. The shear test condition is added to the models. The normal stress is fixed at 2 MPa, and the shear load is added to the model till failure occurs. The results obtained show that in a fixed rock bolt angle, the tensile crack initiates from the joint tip and propagates parallel to the shear loading axis till coalescence to rock bolt. In a constant Rock Bridge length, the shear strength decreases with increase in the rock bolt angle. The highest shear strength occurs when the rock bolt angle is 0° .

Historically, the design of the in-stope pillar in underground excavations has been based on empirical formulae and numerical modeling. Although these design methods have been extensively applied in several gold mines in South Africa, rockburst, in-stope pillar burst/failure are continuously reported as the major problem faced by mines. Therefore, this study attempts to compare the performance of the shotcreted and bolt-reinforced in-stope pillar with the bolt-reinforced in-stope pillars. Numerical modeling was simulated focusing on the major principal stresses ahead and along the de-stress cuts, damage along the in-stope pillar (yieldability of the in-stope pillar), and the rate of energy release along the in-stope pillar. Owing to that, seismic events with log P ≥ 1 were used through assessing their source mechanism, damaged area, rock mass response after the event, and source parameters for the events. The results of the study have shown that the in-stope pillar along different de-stress cuts was extensively yielding in the model. Very high-stress magnitudes were forecast in a zone ahead of the advancing face. Further results from a seismic point of view have shown that the estimated source mechanism from different case studies had a dominant double-couple component, and the steeply dipping nodal plane aligns well with the NNE-SSW to the dike. Shear-type failure on the faults/dike was the most probable source mechanism of the events. Visually, observation results have shown that most of the bolt-reinforced in-stope pillars resulted in extensive scaling and fracturing during the dynamic movement of the ground, while bolt-reinforced and shotcreted in-stope pillars were noted to have minor or no damage during the dynamic movement of the ground.