Behavior Of Bolts Research Articles

繰り返しせん断力を受ける接着系あと施工アンカーの力学モデル

Recently, it has become increasingly important to instigate more widespread seismic retrofitting for seismically weak structures in Japan, which is frequently subject to massive earthquakes. Generally, post-installed anchors are used to connect the seismic retrofitting members to existing members. However, no computational models of post-installed anchors have yet been proposed in previous studies to evaluate stress-displacement relationships. Accordingly, we developed a new mechanical model for post-installed anchors. In this model, the kinking behavior of anchor bolts, bearing behavior of concrete, and tensile behavior of anchor bolts are considered. The proposed model can reasonably simulate the mechanical behaviors of the previous test results.

Analysis on the Mechanical Behavior of Pipe Roof and Rock Bolt of Shallow and Unsymmetrical Tunnel in Soft Rock

In this paper, the mechanical behaviors of pipe roof and bolt of shallow and unsymmetrical tunnel in soft rock are analyzed. Through the finite element software Phase2.0, combined with the geological conditions that construction site often appear, the mechanical behaviors of pipe roof and bolt and surrounding rock in the process of horseshoe highway tunnel construction in the condition that surface is soft rock and underground for the bedrock are analyzed. Research results show that: after tunnel excavation in soft rock, surrounding rock near the tunnel is easy to suffer soft-rock large deformation even failure, which needs to timely support；Due to the impact of the unsymmetrical tunnel, the mechanical behaviors of surrounding rock are unsymmetrical, such as the maximum displacement of tunnel around 0.4 m distant from apex of arch ring, the stress is asymmetrical on both sides of the tunnel arch ring etc; In addition, pipe roof can effectively prevent from the displacement of soft rock strata, improve tunnel strength factor, reduce the plastic zone of surrounding rock. This paper provides theoretical basis for the design of pipe roof and bolt.

The Finite Element Analysis on High Duty Bolted Joints of Slewing Bearing

By reasonable assumption and considering the friction, contact, preload intensity, load eccentricity, bolt bending, and other nonlinear factors, we establish three-dimensional finite element model for the high duty bolted joint to reflect the bolt behavior and develop the finite element calculation method for static strength, fatigue strength and related stresses of bolt. By this method, we do numerous numerical simulation experiments to study the effects of preload intensity, support plate thickness on the bolt behavior. These results will guide designer to complete the slewing bearing design effectively and accurately, and these research ideas can be well applied to bolted joints study in other devices.

Tightening and loosening torque of M253M bolts: Experimental and analytical investigation

The present paper deals with the study of the installation behavior of high-strength bolts under friction. For this purpose an experimental program was conducted to evaluate the energy of these bolts that is dissipated due to tightening and loosening. The total number of tested specimens was 100 bolts furnished to the requirements of AASHTO specification M253M. The turn-of-nut tightening method is applied experimentally to evaluate the pretension and the torque for tightening and loosening of bolts. It is mentioned that a number of 56 bolts has 76 mm length while the rest is of 152 mm. The experimental preloading and the lost torque that overcomes friction are compared with the respective analytical values. It is confirmed that the K-nut factor is affected by the type of lubricant and the length of the bolt. Additionally, most of torque is going to overcome friction. The percentage of tightening and loosening torque for both the analytical and the experimental cases is very close.

Behaviour of Slope Protecting and Retaining Structures during Wenchuan Earthquake on May 12 2008

At 14:28, May 12th 2008, a strong earthquake measured Ms8.0 hits Longmenshan mountain area, west Sichuan province, China. The quake is induced by the thrust of Longmenshan central fault, results in around 50000 rock avalanches and landslides, destroys numerous villages and towns, and causes nearly 90000 fatalities or missing. Based on field reconnaissance, the geology and fault patterns in Longmenshan mountain area are firstly introduced, then the damage or failure phenomena of slope protecting and retaining structures in quake-hit area is described and discussed, including slide-resistant piles, gravity retaining walls, shotcrete, anchored concrete frame, cable bolts and protecting nets. Special discussion is given to the behaviour of cable bolts based on measured data. And finally design issues is discussed in quake-prone areas.

Experimental Bond Behavior of Mortar Grouted GFRP Rock Bolt

Bolts are widely used in slope engineering, tunnel and large cave supporting structures, as well as restoration of engineering structures. They can improve the strength and stability of ground, rock mass, and other structures. The traditional steel bolt has some disadvantages, such as easy corrosion, heavy weight, and difficult operation. Glass Fiber Reinforced Polymer (GFRP) is more resistant to chloride, stronger and lighter than steel. Those advantages make it a better alternative in some fields of engineering. To utilize GFRP bars as rock bolt, some aspects of its behavior, such as bond strength in mortar, bearing capacity, and bond stress distributing along its interface, have to be examined. This paper presents a research on bond behavior of GFRP rock bolts. A concrete block is used to represent rock mass in laboratory. Modified pull out tests were conducted on selected GFRP bars and compared with steel ones that were grouted with mortar in concrete blocks. Bond characteristics of mortar grouted GFRP rock bolts with diameter 16mm were mainly evaluated and other specs of bolts were also discussed.

Testing of composite steel top-and-seat-and-web angle joints at ambient and elevated temperatures: Part 2 — Elevated-temperature tests

An experimental programme of eight elevated-temperature tests on composite steel top-and-seat-and-web (TSW) angle joints was carried out to investigate the behaviour of this form of joints under fire conditions. It is found that the inherent strength and stiffness of composite joints can significantly improve the structural behaviour of steel framed structures under fire conditions. However, experimental works on composite steel TSW angle joints under fire conditions have not been published yet. To develop a versatile model to predict the joint moment-rotation characteristics, the authors have developed a component-based mechanical model for this form of joints. The objectives of this study are to ascertain the moment-rotation characteristic for this form of joint at elevated temperatures and to validate the authors’ mechanical model. The effects of some parameters on the overall joint behaviour, such as elevated temperatures, longitudinal shear strength of RC slabs, steel beam depth and bolt behaviour were observed and investigated. The mechanical model predictions are compared with the test results and showed good agreement.

Shear strength of high-strength bolts at elevated temperature

Failure of bolted connections has frequently occurred during fire events. Because knowledge of the behavior of high-strength bolts while under fire is insufficient, there is further need to establish the behavior of high-strength bolt while under fire load. In this study, the behavior of high-strength bolts was investigated by a series of tests conducted at elevated temperatures with the parameters of temperature, number of bolts and the joint geometry analyzed. The strength deterioration and the deformation characteristics of the bolts were analyzed and discussed. Based on the experimental results, it was found that AIJ specification provides a conservative prediction for the strength of high-strength bolt under fire conditions, while BS5950 overestimated bolt strength. Eurocode 3 gave a good prediction on bolt strength.

617 三次元有限要素解析による植え込みボルトの力学特性の評価(GS-3 材料検査および評価)

617 三次元有限要素解析による植え込みボルトの力学特性の評価(GS-3 材料検査および評価)

The Impact of Corrosion on the Mechanical Behavior of Bolt

Corrosion is a negative contributor on the structural integrity of rock bolt and leads to degradation of the mechanical properties of steel rock bolt. Exposure to chloride, seawater, salt and saltwater and deicing chemical environments influences rock bolt and weakens it. In order to evaluate the influence of corrosion and the size of the steel on the mechanical properties of rock bolt, an experimental investigation was conducted on rock bolt whose rebar is 8, 12, 16, and 18 mm diameter, and which were artificially corroded for 10, 20, 30, 45, 60, 90, and 120 days. By the simulation corrosion test of loaded and unloaded bolts in Na2SO4 solution, the relation curves of the mechanical performance with the corrosive conditions and the corrosion time are given. The mechanical performance is compared between these two types of bolts. At the same time, the influential trend of the load on the mechanical performance of the corroded bolt is analyzed. The laboratory tests suggest that corrosion duration and rebar size had a significant impact on the strength and ductility degradation of the specimens. after being corroded in Na2SO4 solution, both the ultimate bearing capacity and the maximal tensility of loaded bolt decrease far more than those of unloaded bolt, and the endurance and service life of loaded bolt will also be shortened much more severely. The tensile mechanical properties before and after corrosion indicated progressive variation and drastic drop in their values.

209 有限要素解析による軸継手用リーマボルトの力学特性の評価(GS-3 力学特性(1))

209 有限要素解析による軸継手用リーマボルトの力学特性の評価(GS-3 力学特性(1))

PULL-OUT TEST OF ANCHOR BOLT FOR FASTENING LEAD DAMPER TO CONCRETE FOUNDATION

Pull-out tests on anchor bolts for fastening lead damper to concrete foundation were conducted to evaluate factors affecting pull-out behavior of anchor bolts. The main parameters were type of anchor bolt commonly used for anchorage of lead damper and layout of reinforcements around anchor bolt. The following results were obtained : (1) Vertical reinforcements arranged around anchor bolt contribute to increase in concrete breakout strength. (2) For long nut type anchor bolt, long nut length covered anchor bolt must be treated with enough care to avoid slipping anchor bolt. Because slipping failure lead to decrease in tensile strength and increase in pull-out displacement at failure. (3) The slope of the concrete cone was much flatter than 45 degree assuming in design procedure, regardless of the embedment depth, anchor type and reinforcement pattern. (4) Based on test results, simple concrete failure model was proposed. Using this model, effective radius of projected area were assessed 0.81le - 0.96le. These values were close to effective radius 1.0 le in existing design formula according to AIJ.

Experimental behaviour of anchor bolts under pullout and relaxation tests

The anchoring between a metallic component and a concrete block is an essential point in stability and durability of the structure. This joint has to transfer the deadweight of the structure and tensile, compressive and shearing loads created by the structure in service. This study focuses on the joint constituted of long anchor bolts cast-in-place. The anchor rods are prestressed in order to minimize the effects of fatigue stress. To design these anchors the long-term behaviour of concrete is not taken into account whereas the concrete creep and shrinkage involves a decrease in the initial prestress level. This paper presents experimental results of pull-out tests and mass-spring modelling of the joint is proposed. In this model the long-term behaviour of the joint is taken into account using the creep and shrinkage laws given in Eurocode 2. The modelling of the evolution in time of the rod prestress shows good agreement with the measurements obtained in relaxation tests.

Shear Behavior of A325 and A490 High-Strength Bolts in Fire and Post-Fire

High strength ASTM A325 and A490 bolts were tested in shear at temperatures up to 800 °C (1,472 °F). The shear strength showed a gradual reduction in both types of bolts as the temperature was increased above 300 °C (572 °F). Strength reduction factors for both types of bolts at elevated temperatures were obtained to provide a means of estimating the bolt shear strength during fire. The residual strength of A325 and A490 bolts after exposure to elevated temperatures was also investigated by both direct shear tests and hardness tests. Significant strength loss occurs on both types of bolts after exposure to temperature higher than the tempering temperature employed in the manufacturing process. The hardness value at 1/2R location on the bolt cross section was found to provide a good estimate of the bolts residual strength. The hardness test provides a simple and practical method to assess the post fire strength of a bolt.

Structural behavior of tension joint with high-strength bolted split-tee

The strength and behavior of split-tee connections that are applicable to all tensile connections with high-strength bolts have been studied in many countries. The design code of each country (AISC, Eurocode 3) does not consider various field conditions, however, such as the painting of the connection surface, the length of the bolt shank, and the preload. Moreover, the previous studies (Bahaari) that used the link element on the preload of the bolt could not predict the correct behavior of high-strength bolts. In this study, to evaluate the tensile capability of split-tee connections, a total of 20 split-tee specimens with two bolts each were fabricated and tested. The experiment parameters that were used were the thickness of the T-flanges, painting, preload, and the length of the bolt shank. The joint stiffness of split-tee connections was compared with the stiffness equation of Faella et al., and finite-element method analysis with Ansys 8.0 was conducted. Further, to verify the reliability of the highstrength-bolt model, the load-to-bolt stress relation in the experiment test and the analysis results were compared.

Analytical Behaviour of Bolt–Joint Intersection Under Lateral Loading Conditions

An analytical method is developed to provide a better understanding of bolt shearing across joint planes under lateral confinement. The study was undertaken in conjunction with a laboratory study of the double shearing of bolts in concrete. A review of various analytical methods is discussed, and the bending behaviour of the bolts is studied under both elastic and plastic conditions. Issues examined include; hinge point location, the effect of concrete strength on the bolt-bending behaviour; the influence of bolt axial loading and bolt diameter on the hinge point position with respect to sheared joint planes. It was found that the applied axial load on the bolt had a significant bearing on the location of the hinge points in different strength concrete, particularly at low strengths. The hinge point location is also influenced by the bolt diameter.

A Comparison for Shear Resistant Behavior of Joints with Rock and Spiral Bolts Installed—A Numerical Approach

ABSTRACT Spiral bolt is recently developed to enhance the support capability and cost effectiveness of rock bolt type support, and previous studies show that pull-out strength of spiral bolt is superior to rock bolt owing to gearing effect of spiral shape, even though the spiral bolt has less cross sectional area. In addition to the axial reaction of rock bolt such as suspension of rock blocks, if rock block slides on joint surface, bolt should react on shear force. Many studies indicate that shear loading contributes significantly to failure, which implies that shearing behavior of rock bolt type support ought to be investigated. In this study, we made two different numerical model with single weak layer for weathered rock, soft rock and hard rock as base rock blocks: (1) cylindrical shape mortal with centered deformed bar rock bolt, (2) cylindrical shape mortal with centered spiral bolt (twisted flat bar). To investigate the effect of axial force of bolt on shear strength, numerical simulations were done for both with and without the initial axial force of bolts. The results shows that shear resistant behavior of spiral bolt for hard rock joint is slightly superior to the rock bolt, but shear resistant performance of rock bolt for soft rock and weathered rock is equivalent or slightly superior spiral bolt. Spiral bolt can be a good alternative to rock bolt as it shows high performance in both axial and shear behavior of bolts.

Load–deformation prediction for eccentrically loaded bolt groups by a kinematic hardening approach

The use of steel plates anchored on the sides of beams is effective in strengthening existing beams when they have deteriorated. The behaviour of the side plated beam is highly affected by the level of partial interaction between the components, which is provided by the use of bolts acting in groups. To determine the structural response of composite beams, the interaction through bolts or the load deformation response of bolt groups should be modelled. This study aims to develop a procedure to predict the non-linear load–deformation response of bolt groups subjected to combined in-plane moment and shear. The in-plane behaviour of bolts is first established by adopting the analogy from material plasticity. Then the incremental load–deformation responses of bolt groups are derived. Numerical examples are carried out and the results are verified by the available experimental results. The theory developed herein is able to model the load–deformation response of bolt groups and can potentially be applied to non-linear analyses of bolted side plated structures.

Effect of different salts on the corrosion properties of friction type A607 steel rock bolt in simulated concentrated water

Friction type steel rock bolts are one of the most commonly used for reinforcing tunnels (since the late 1970s) due to their ability to sustain large rock mass displacements. In this paper, corrosion behavior of an FRS rock bolt (ASTM A607 steel) was investigated under Yucca Mountain simulated concentrated water at different concentrations (1×, 10× and 100×) and temperatures by using electrochemical measurements. Effects of individual salts, chlorides, sulfates, bicarbonates and silicates were also evaluated using the same method. Overall, the corrosion rate was an order of magnitude higher in an aerated condition than in a deaerated condition. The results from the individual salts showed the highest corrosion for the bicarbonate salts (∼300 μm/yr) and lowest for the silicate (4 μm/yr). The bicarbonate solutions accelerate the anodic dissolution of steel at higher concentrations. In the case of silicate solutions, the rock bolt shows passivity even at a higher negative potential (−925 mV) compared to other salts (∼−750 mV) with a large passive region which forms a protective layer on the specimen surface.

A numerical study on bolted end-plate connection using shape memory alloys

Superelastic shape memory alloys (SMAs) have the ability to recover their original shape after experiencing large strains. A new beam-to-column connection incorporating long shank SMA bolts is presented in this paper. By using the unique characteristics of SMAs, the connection possesses self-centering abilities. The 3D connection model is created using the software ANSYS, and Auricchio’s model is used to simulate the superelastic behavior of the SMA bolts. With cyclic loads applied on the beam ends, the behavior of the connection is studied. The results show the semi-rigid and moderate energy dissipation characteristics of the connection. Since the moment-carrying capacity of bolt cluster controlled below the elastic flexural capacity of connecting beam, a superelastic hinge forms just at the beam-to-column interface. The inelastic interstory drift angle of the connection reaches 0.035 rad, and 94% of the total rotations are recoverable upon unloading.