Axial Bolt Force Research Articles

652 ボルト軸力のばらつきが内圧作用下の非石綿ガスケット付き管フランジ締結体の密封性能に及ぼす影響

652 ボルト軸力のばらつきが内圧作用下の非石綿ガスケット付き管フランジ締結体の密封性能に及ぼす影響

The Effect of Axial Bolt Force and Gasket Properties on Sealing Performance of Flange Connection

The Effect of Axial Bolt Force and Gasket Properties on Sealing Performance of Flange Connection

604 ガスケット締結体の高温時軸力挙動評価

604 ガスケット締結体の高温時軸力挙動評価

Influence of Dilation on the Axial Load of Bolt as Joint Subjected to Shearing

Based on the load transfer mechanism of bolts, the relationship between the axial load and shear displacement of bolt changing with the dilatancy of joint was analyzed, then the theoretical solutions of axial load of the bolt were verified by the direct shear test of bolted rock mass with different normal stress (0.5MPa, 0.7MPa, 1.0MPa) applied on the joint. The results show that the calculated values fit well with the results of tests; the increment of dilation angle can enhance the axial force of bolt quickly, but decrease the length of crushing failure zone.

Analysis on Dynamic Response of the Foundation Pit Supporting Structure under Vehicle Loads

Using ABAQUS software analyzed the dynamic response of foundation pit supporting structure under vehicle loads. The vehicle load was simplified as a half-wave sinusoidal load, in order to analyze the influence of internal force and displacement of pile-anchor supporting structure under the vehicle loads, the position of half-wave sinusoidal load and the size of radian frequency were considered. Loading location away from the supporting structure is more nearly and the displacement value of support piles is greater, the greater the axial force of the bolt; with the increasing of radian frequency, the horizontal displacement value of supporting piles increased, on the contrary, the axial force of bolt reduced. A practical engineering was studied here. analysis of the monitoring data and compared with the numerical results, the analysis showed that the experimental results and numerical results are in good agreement, and the numerical method can be used as an effective means of research. The conclusion of the study has significance on engineering practice.

The Studying of Reinforcement Mechanism of Fully Grouting Rock Bolt in Brittle Wall Rock Mass

The bolt’s load transfer differential equation has established according the stress equilibrium in a small section of a bolt and load transfer mechanics. And according the rock mass deformation before and after bolt assembling, the rock bolt’s load transfer equation has gained. In this paper, from later researching achievement, the radial displacement function of brittle wall rock for tunnel is gotten. And combining the radial deformation of tunnel wall rock mass, the axial force and friction resistance of rock bolt have gotten in brittle wall rock mass. Through analyzing the stress distribution feature and stress distribution tendency and affection factors, the affection factors to anchoring results is the dilatancy angle. And through the studying, it is show that the axial force and shear stress of rock bolt are bigger with the dilatancy angle increase

FEM Stress Analysis and Sealing Performance Evaluation of Pipe Flange Connection under Cyclic Internal Pressure and Thermal Changes

The effects of cyclic internal pressure and thermal changes on the sealing performance and mechanical behaviors in pipe flange connection are examined using the FEM analyses for pipe flange connections with spiral wound gasket (SWG). The contact gasket stress distributions and the axial bolt forces taking into account the cyclic internal pressure and thermal changes are demonstrated. The load (internal pressure, thermal changes) sequences are determined from the conditions for actual pipe flange connections used in petroleum and chemical plants. Furthermore, the effect of material differences between pipe flange and bolts on the contact gasket stress distribution are examined. From the FEM results, it is found that the contact gasket stress reduces to be the smallest when a plant is restarted. The reduced contact gasket stress should be taken into account in the sealing design of the connection. On the other hand, the leakage tests were carried out to verify the FEM results and the effect of number of cycles (for 21days). A fairy good agreement is seen between the estimated amount of leakage due to the contact gasket stress distributions obtained from the FEM and the measured amount of leakage. It is found that the contact gasket stress decreases when the plant is restarted and as the temperature decreases. At that time, the contact gasket stress is the smallest which may lead to a leakage accident.

Experimental and Finite Element Study on Mechanical Behavior of Bolted Joint with Bolt Clearance in Transmission Tower

To accurately analyze the force and deformation of the transmission tower, it is necessary to study performance of bolted joint in the tower. In the paper single shear and double shear bolted joint with number of bolts changed is tested. Based on the actual data in test, nonlinear finite element model of bolted joint is established with ABAQUS, considering the bolt clearance and preload, and shows good agreement with test results, which is proved correct and applicable. Eventually, through a comparison of FEM and test results, the factors that affect bolt slip and the changing relationship of axial force of bolt and friction force is described.

부재 및 고장력볼트 구멍치수에 따른 미끄러짐계수의 실험적 연구

Abstract Slip coefficient, whose value is dependent on the condition of contact surface at the friction joint of high tension bolt, is determined by slip load. Because contact area affects slip load, contact area that varies with bolt hole size is also related to the slip coefficient. In this study, we manufactured 32 specimens and performed bending and tension tests in order to examine changes in slip coefficient and load with material type, bolt diameter, and size of bolt hole. Slip load of specimens with oversize bolt hole had strength that was more than 80% higher than the slip load of specimens with standard bolt hole, and it also exceeded the design slip strength. In addition, we observed significant correlation between net-section ratio and slip ratio of specimens with oversize and standard bolt hole. However, some differences between the specimens are thought to have been caused by reduction in initial axial force of high tension bolt, which is an important parameter of slip coefficient. It is self-evident that increased bolt hole size would lead to decrease in design strength as it reduces both slip coefficient and bolt axial force. Nevertheless, we suggest that some flexibility in regulation of bolt hole, as long as it does not threaten the structural stability, may be a positive factor in terms of workability and efficiency.

Application of Plastic Region Bolt Tightening Method to Larger Flange Connections

The plastic region bolt tightening method has been applied to the smaller pipe flange connections and its advantages had been demonstrated. The scatter in axial bolt forces for the smaller pipe flange connections which applied the plastic region bolt tightening method was minimal and it was effective for the leak prevention. In addition it is possible that the bolt diameter is downsized due to an obtainment of the higher axial bolt forces. However, the behavior of the larger flange connections has not been investigated. The flange rotation of larger flanges increases when the internal pressure is applied. In addition, the gasket stress is not uniform and it may cause the leak accident. It is necessary to investigate the behavior of the larger flange connections. The present paper describes the behavior of the larger flange connections under the plastic region bolt tightening. Firstly, JPI 20-inch flange connections tightened to the plastic region by downsized bolt and superiority in the uniformity in the axial bolt forces is demonstrated. And then, the internal pressure is applied to the flange connections and the behavior of the additional axial bolt force is demonstrated. The axial bolt force decreases with an increase in the internal pressure, and the load factor is negative due to increase of the flange rotation. However, the load factor of flange connections tightened to the plastic region by using downsized bolt approached zero. Downsizing of the bolt acts on advantageously for the larger flange connections whose load factor is negative and it is effective to the leakage prevention. Moreover, the leak rate from the flange connections is measured and sufficient sealing performance is obtained.

Estimation of Axial Force of Bolt in Bolted Joint under Constant Amplitude Loading

Fatigue tests of bolted joint were carried out under constant amplitude loading. In all tests, bolts were broken at the root of the first thread where the nut and bolt were engaged. The relationship between the stress amplitude, which was defined as the load divided by the effective cross-sectional area of the bolt, and the number of cycles to failure showed a curve similar to a typical S-N curve. To estimate the axial force of bolt in bolted joint, the compressive force of bolted joint was detected by using the self-made load cell during the fatigue test. The maximum compressive force decreased as the cycle increased, while the minimum compressive force was equal to zero independent upon the load cycle. The axial loading pattern applied to the bolt could be estimated based on the change of maximum compressive force and the test load amplitude. The fatigue tests of bolt were carried out under the estimated loading pattern. The fatigue life of bolt was in good agreement with the life of bolted joint.

Elasto-Plastic FEM Stress Analysis and Mechanical Characteristics of Pipe Flange Connections with Non-Asbestos Gaskets under Internal Pressure

The effects of the nominal diameter of pipe flange connections with non-asbestos spiral wound gaskets(SWG) under internal pressure on the mechanical characteristics such as the contact gasket stress distribution which governs the sealing performance, the load factor and the hub stress of the connections were evaluated. The stresses in the connections with the nominal diameters from 3” to 24” under internal pressure are analyzed using the elasto-plastic(EP) FEM analysis taking account the hysteresis and non-linearity of deformation behavior of the non-asbestos SWG. As a result, it is found that the variations in the contact gasket stress distributions are substantial due to the flange rotation in the connections with the larger nominal diameter. Leakage tests were conducted to measure the axial bolt forces (the load factor) and the hub stress. The results obtained from the EP-FEM analyses are fairly consistent with the experimental results concerning the variation in the axial bolt forces (the load factor) and the hub stress. Using the obtained contact gasket stress distributions and the fundamental relationship between the amount of leakage and the contact gasket stress, the amount of the leakage of the connections is estimated. It is observed that the sealing performance of the connections with larger nominal diameter is worse than that of the connection with smaller nominal diameter because of the flange rotation. The estimated results are in a fairly good agreement with the measured results. The difference in the hub stress between the EP-FEM and ASME code is demonstrated and the differences in the load factor and the sealing performance of the connections are shown between the asbestos and non-asbestos gaskets.

OS1411 フランジ締結体の密封特性に及ぼすボルト軸力とガスケット特性の影響

OS1411 フランジ締結体の密封特性に及ぼすボルト軸力とガスケット特性の影響

Shearing Stress Model of Damage Bolt in Tunnel

When bolt is damaged, character of stress is different from character of shear stress integrated bolt. Firstly, Based on the displacement formula of the tunnel surrounding rock，the shear stress and axial force calculation formula of integrated bolt are educed. Subsequence, based on the BOUSSINESG formula of displacement, models on fully grouted bolt shear stress and axial force of uniform rock are educed under pullout load. Consequently, the author deduces shear stress model of bolt damage (completely void of bolt and grouting), combining modes on shear stress and axial force of integrated bolt and shear stress model of bolt under pullout load..

Studies on gasketed flange joints under bending with anisotropic Hill plasticity model for gasket

The behavior of a gasketed flange joint under bending loads has been studied by three dimensional finite element analysis (FEA) and experiments. The in-plane and bending stiffness of spiral wound gaskets are considered using anisotropic Hill plasticity material model. The variation in bolt axial force of joints under bending load predicted by the finite element analysis compares well with the experimental results. The contact stress distribution obtained have significant variation in the pattern from the previous material models and consistent with the results of Bouzid [1] regarding flange rotation.

Analysis of Mechanical Characteristics of Site Experiment on Supporting Structure in Gypsum Breccia Tunnel

Gypsum breccia is a kind of soft rock-hard soil, and its component is complex. It has poor cementation, low intensity, strong water reaction, slight expansibility and corrosion. During the tunnel construction of gypsum breccia stratum, the mechanical characteristic of supporting structure is very complex. In order to ensure the safety, reasonability and economy of tunnel support system, it is important to acquire the information on displacement and stress of surrounding rock and support system. Two test sections are selected to monitor. Based on the measured data, the distribution characteristics and the time variation law of different kinds of support in gypsum breccia stratum are studied, including surrounding rock pressure, axial force of rock bolt, support pressure and stress. Such conclusions can be got: When strengthened lining (16# I-steel) of the V-grade surrounding rock used, support system performs well; but the stiffness of primary support is not enough if grillage lining is used. Growth of surrounding pressure is for a long time, which shows that the rock mass has Flow characteristics. Especially the surrounding rock pressure increases continuously. The spatial distribution is random, and the value is large. The stiffness of support system should be strengthened. Most blots at the waist arch are compressive. Bolts at the foot arch and sidewall are under tension. The maximum is nearly 124kN. Contact pressure between primary support and secondary lining at the sidewall is higher than that at arch parts. Steel frame stress comes up to 80% of the maximum within 20 days. Excavation of invert has great influences on stress state of surrounding rock and support system.

Optimisation of pre/post-stressed embedment-type timber joint

This paper analyses the optimisation studies of a pre-stressed embedment-type timber joint system, the Kusabi–Nageshi (K–N) timber joint system, designed to be used for structures in seismic-prone countries. The K–N joint is composed of a triangular-sectioned beam and wedges in combination with bolts. Its resistive mechanism utilises the embedment strength of timber and the pre-stress in association with friction. In addition, elastic energy deposited in the bolt as storage fills the gap as it is deformed during the embedment. With the aim of optimising both mechanically and physically, several alterations were tested in terms of shape (taper angle) and of combining densified veneer wood (DVW) with the joint members. A cyclic loading test of the cross joints was made to examine their structural behaviour. The use of less tapered wedges showed higher stiffness and strength, but the beam beneath was undesirably embedded. Different combinations of reinforcement with densified veneer wood showed that the use of the wedges alone provided high optimisation, and an increase in bolt axial force. The successful test results observed in the alteration using the densified veneer wood are expressed using the ‘analytical K–N joint diagram', an analytical method modified from a conventional joint diagram used in mechanical engineering, which showed itself to be an applicable method to predict the trend of the altered K–N joint. The use of the new tapered angle and densified veneer wood for optimisation, and the performance predictions using the analytical K–N joint diagram, will need further precise investigations but their great benefits are potentially promising.

Elasto-Plastic Stress and Deformation Analyses of the Bearing Surfaces in Hollow Cylindrical Bolted Joints under External Axial Loads

An important issue is how to determine a bolt preload of a bolted joint taking an external axial load into account. The following two methods for determining the bolt preload are discussed in the present paper. In the first method, the bolt preload is determined such that the stress at the bearing surfaces is lower than the yield stress of the clamped parts taking account of the load factor. In the second method it is determined such that the stress at the bearing surfaces is higher than the yield stress of clamped parts. Thus, firstly the load factor to obtain the increment Ft in the axial bolt force when an external load is applied to a bolted joint is investigated using axi-symmetrical theory of elasticity, FEM analyses and experiments. The analytical results are in a fairly good agreement with the FEM and the experimental results. Then, the contact stress distributions and the plastic displacement distributions at the bearing surfaces under external loads are examined using elasto-plastic FEM analyses. Experiment to measure the load factor and the reduction in the axial bolt forces were carried out. The prediction for the reduction in axial bolt force of the joint under external load is fairly consistent with the experimental result. In addition, in the first method for determining the bolt preload, it is found that no plastic deformation is occurring at the bearing surfaces and no reduction is occurring. It is noticed that a higher bolt preload according to the second method shows a small reduction in axial bolt force. Discussion is made on the critical stress at the bearing surfaces.

G030162 軸方向外力を受ける中空円筒ねじ締結体の内力係数と座面永久変形にっいて([G03016]材料力学部門一般セッション(16):応力分布)

An important issue is how to determine a bolt preload of a bolted joint taking an external axial load into account. One method for determining the bolt preload is such that the stress at the bearing surfaces is less than the yield stress of the clamped parts taking account of the load factor. Another method is such that the stress at the bearing surfaces is higher than the yield stress of clamped parts. Firstly the load factor to obtain the increment F, in the axial bolt force is investigated using axi-symmetrical theory of elasticity, FEM analyses and experiments. Then, the contact stress distributions and the plastic displacement distributions at the bearing surfaces under external loads are examined using elasto-plastic FEM analyses. The prediction for the reduction in axial bolt force of the joint under external load is fairly consistent with the experimental result. It is noticed that a higher bolt preload according to the second method shows a small reduction in axial bolt force. Discussion is made on the critical stress at the bearing surfaces.

OS2622 一定振幅荷重下のボルト締結体におけるボルト軸力の評価(OS26-5 西谷弘信セッション4,OS-26 西谷弘信セッション)

OS2622 一定振幅荷重下のボルト締結体におけるボルト軸力の評価(OS26-5 西谷弘信セッション4,OS-26 西谷弘信セッション)