High-tensile Bolts Research Articles

A Study on Improving the Construction of Tunnel Steel Ribs Using High-Tensile Long Bolts

Steel ribs installed to enhance tunnel stability have consistently been criticized owing to their structural vulnerabilities and on-site construction inconvenience. Therefore, this study aims to address these issues and contribute to safer tunnel construction. To address the structural weaknesses resulting from the reduced steel section at the upper and lower junction parts of the tunnel steel ribs as well as the keystone junction parts, reinforcement was achieved by using long high-tensile bolts and steel bars. Test results on the bending strength of the junction revealed that the upper and lower junction parts exhibited a bending strength 1.38 times higher than those of the general sections of steel ribs, and the keystone junction parts showed a bending strength of 1.70 times higher, meeting or surpassing the equivalent strength criteria. Moreover, by utilizing high-tensile long bolts with adjustable heights, the constructability and construction speed were both enhanced. Consequently, it was determined that construction costs could be reduced by 2.42% and that the construction speed could be improved by approximately 333 h/km.

An Experimental Study on the Seismic Performance of a Replaceable Steel Link System Acting as a Structural Fuse

This study investigated the seismic performance of reinforced concrete columns retrofitted with Replaceable Steel Links (RSLs), focusing on the effects of varying sliding slot lengths and torsional loads. The RSL system, known for its simple construction and effective seismic performance, was analyzed to assess the feasibility of substituting damaged steel links post-earthquake, using the system as a structural fuse. The experimental results highlighted the role of sliding slot lengths in delaying the initiation of shear cracks, especially under eccentric lateral loads. The RSL system exhibited notable torsional resistance, showing only a 10% decrease in maximum load capacity, even with a two-fold increase in the eccentric distance. Furthermore, with an increase in sliding slot length, the difference in cumulative energy dissipation attributable to augmented eccentric distances reached approximately 50%, indicating a notable impact of sliding slot length on the system’s ability to resist torsion. Consequently, it is recommended that the length of the sliding slot be based on the specific seismic design objectives when employing the RSL system as a structural fuse. The post-experiment inspection revealed no deformation in the steel plates, and the buckled steel links could be effortlessly replaced by loosening the high-tensile bolts in the slots. These findings demonstrate the RSL system’s efficiency as a structural fuse.

Connecting performance evaluation of the Quick-Connector for modular steel construction

This study presents the Quick-Connector, a new self-fastening joint system designed specifically for modular steel construction. By eliminating the need for a dedicated workspace during the connection process, the Quick-Connector minimizes disruptions to finishing work. A comprehensive set of tests, including pull-out, shear, and cyclic tests, was conducted on a full-scale prototype to evaluate its structural performance. The experimental results demonstrate that the Quick-Connector exhibits exceptional connecting performance, meeting the shear and tensile strength requirements for high-tension bolts. The seismic performance of the Quick-Connector was also evaluated through cyclic testing, highlighting its potential as a viable replacement for high-tensile bolts. Furthermore, a push-over analysis was carried out to develop an elastic structural design model specifically for buildings incorporating the Quick-Connector. The analysis results closely aligned with the experimental findings, validating the accuracy of the proposed model. Overall, the Quick-Connector offers a promising alternative to traditional bolted connections in modular construction, with the potential to enhance construction efficiency, quality, and safety.

System-level seismic fragility of high-speed railway track-bridge system with component-replaceable U-shaped combined steel damper

A component-replaceable U-shaped combined steel damper (UCSD) was presented as an energy dissipation device to mitigate the seismic damage of high-speed railway track-bridge system (HSRTBS). The energy-dissipation modules inside the UCSD can be replaced by removing the high-tensile bolts. A low cyclic test of the energy dissipation module was carried out. Parametric analysis of the UCSD with varying U-shaped plate thicknesses was conducted using finite element analysis, including 8, 10, 12, 14, and 16 mm. To study the effect of the UCSD on HSRTBS under near-fault ground motions, twenty-eight near-fault records recommended by FEMA-P695 were selected, and the UCSD was installed adjacent to bearings in HSRTBS. Component-level fragility curves of HSRTBS with UCSDs with the different thicknesses of U-shaped plates were compared. To comprehensively and efficiently evaluate the contribution of the UCSDs on HSRTBS, system-level fragility curves were obtained by the product of the conditional marginal (PCM) method. Results indicate that the UCSD exhibits excellent hysteresis performance and energy dissipation capacity, improving with the U-shaped plate. At the maximum considered earthquakes (MCE) level, the exceeding probability of complete damage of the system is reduced from 100 % to 95 %, 79 %, 57 %, 35 %, and 20 % respectively after adding UCSDs in five different U-shaped plate thicknesses. This reveals that the proposed UCSD can effectively mitigate HSRTBS seismic damage under near-fault motions, progressively improving with increased U-shaped plate thickness.

Fatigue Behavior of M20 Torque Shear High-Strength Bolts under Constant-Amplitude Loading

Torque-shear high strength bolts were developed and widely used recently, and such high-tensile bolts may fracture in practical engineering due to the frequent complex loads, resulting in economic losses and even casualties. However, the fatigue performance of M20 torque shear high-strength bolts under constant-amplitude loading has not been investigated yet, and there are no specific design provisions for determining the constant-amplitude fatigue performance of such bolts. Hence, a total of 10 constant-amplitude fatigue tests were conducted using an MTS fatigue testing machine. For comparison, five different stress amplitudes were investigated. The fatigue performance, stress concentration and fracture analysis were analyzed. The scanning electron microscope images of fatigue failure were obtained to analyze the fatigue fracture characteristics of high-tensile bolts. A finite element model was established to analyze the stress distribution and the hot-spot stress of the bolts. The results suggested that the allowable nominal stress amplitude of M20 torque-shear type high-strength bolts was 96.371 MPa, while the allowable hot-spot stress amplitude was 283.296 MPa. Finally, the test results were compared against the existing design provisions. Upon comparison, the existing design formulas in GB 50017(2017), ANSI/AISC 360-16 (2010) and Eurocode 3 (2003) were found to be generally conservative. The S-N curve of torque-shear high strength bolts under constant-amplitude loading was proposed using the hot-spot stress amplitudes.

STUDY ON OUT-OF-PLANE BENDING BEHAVIOR OF COUPLED GLULAM FRAME WITH HIGH JOINT PROPERTIES ON THE END

The aim of this study is to establish the design method of a timber semi-rigid frame construction system composed with coupled glulam members jointed by screws with steel side plate and high-tensile bolts. In this paper, firstly we proposed the evaluation method for the out-of-plane bending characteristics of the coupled members with high joint properties on the end. Secondly, we conducted the full-scale out-of-plane bending test for the coupled glulam specimens to grasp the mechanical behaviors. We found that the experimental results showed good agreement with the calculations by the proposed method.

Experimental Study on Impedance-Based Damage Detection Considering Temperature Effect

The impedance-based damage detection technique has the potential for health monitoring of different types of structures. However, it is necessary to consider the temperature effect on the impedance signal in applying this technique to actual structures. In this study, an effective impedance-based damage detection method that compensates for the temperature effect was developed. Experimental tests on a steel frame structure connected with high tensile bolts were performed. Moreover, the temperature effect on the impedance damage index was compensated for detecting damage caused by bolt looseness; that is, the relationship between the impedance damage index and the temperature was established through long-term measurements. Based on this relationship, damage detection was performed by compensating for the temperature effect. Because the damage index after the bolt loosening reflects the effects of temperature and damage, it is difficult to evaluate the damage by monitoring only the damage index. However, after compensating for the temperature effect, it was observed that the damage could be estimated precisely. The damage was effectively monitored after measuring the impedance signal and temperature over a specific period for the initial healthy structural state, analyzing the correlation between the impedance damage index and temperature, and setting an appropriate warning criterion based on the correlation.

DEVELOPMENT OF TIMBER MOMENT RESISTING JOINT WITH STEEL SIDED SCREWED JOINT PART 2 : A STUDY ON DETAIL AND DESIGN METHOD OF BEAM-TO-COLUMN JOINT

We developed a timber semi-rigid frame construction system composed with coupled glulam members jointed by screws with steel side plate and high-tensile bolts. Firstly in this paper, we designed the interior and exterior beam to column joints and the frames consisting of the joints of beam end joint precedent yielding type. Secondly, we conducted the bending tests for the frames to confirm the characteristics of the failure behaviors and the estimability of their mechanical behaviors from single screwed joint properties.

The influence of high tensile bolts tightening torque on stress distribution in the bolted connection of rockfall barrier under impact load

The paper presents the finite element method approach to determine stress distribution in rockfall barrier post with end to end-plate connection, assembled with high tensile bolts under two different types of impact load. For the analysis purposes typical fixed to the foundation, rockfall barrier post is adopted with 2,50 m height and sixty degrees slope to the horizontal ground line. One post end is fixed (welded) to the base plate – anchored to foundation, the second end is supported via retaining rope. The impact load applied exactly in the post mid-height and boulder caught via net in the mid-distance between two consecutive post are discussed. Four different locations of end to end-plate connection are analysed measuring from the fixed support i.e. dimension varies in the range of 0,30 m up to 0,60 m with 0,10 m step. Six high tensile bolts, zinc coated with 12.9 grade strength have been adopted in the connection. The stated boundary problem was solved by means of SolidWorks software.

EFFECT OF SURFACE PREPARATION GRADE ON REPAIR BY MEANS OF COVER PLATES AND ADHESIVE

There are a lot of corroded steel bridges, which have to be prolonged its life in Japan. Corroded members in these bridges generally have local corrosion damages, and are often repaired by covering on the corroded area with steel plates in order to rehabilitate the strength. Recently, adhesive such as epoxy resin is often used for bonding the cover plates made of steel or CFRP, even though high-tensile bolts or welding have been adopted conventionally. In this case, surface preparation is the most important issue to bond the cover plates completely. However, complete removal of rust and wastes are quite difficult in the fieldwork of surface preparation. This paper presents recovery effect of local corrosion damage by means of covering method used by adhesive when the rust is not completely removed. Axial tensile tests were conducted for rectangular steel plates of 1,100mm x 100mm x 12mm with 400mm length of corrosion-surface-unevenness on the both surfaces, and the defects of surface preparation are made by putting tape paper at the damaged area. Then various sizes of the repair plates are bonded to consider the influence to repairing. From the test results, the ultimate strength decreased 7-10% compared with non-rust state when the defect area rate was about 30%.

A study of high-strength bolts after dephosphoring

A wide variety of fasteners are produced, including those for the automobile industry, household electrical appliances industry, architectural engineering, and even the aviation industry. The effects of the high-tensile bolt dephosphoring process on the entire fastener manufacturing process and its organizational characteristics and mechanical properties are analyzed and discussed in this study. Our experimental results reveal that the bolt dephosphoring process must be completed before heat treatment, which can be confirmed with a dephosphoring reagent or metallographic observation. Once bolt heat treatment is completed, bolts without dephosphoring appear to be coated with δ ferrite (delta ferrite) composed of a phosphate coating and a phosphatizing coating, which are not easily removed. Heat treatment with phosphorus results in grain boundary segregation, causing embrittlement and a reduction in lattice bonding forces and resulting in a high risk of fracturing when bolts are used in high-temperature environments or undergo multiaxial stresses.

The effect of eccentric loading on the fatigue performance of high-tensile bolts

The effect of eccentric cyclic loading on the fatigue life of bolts has been investigated. It was found that eccentric loading reduced the fatigue life of bolts by an amount proportional to the increase in the local stress amplitude produced by the eccentricity. The increase in local mean stress due to eccentricity was found not to affect the fatigue life, and eccentric loading was found not to affect significantly the shape of fatigue cracks.

非熱処理型高張力ボルトの頭部成形応力と軸部強度に及ぼすバウシンガー効果と時効の影響

At the heading of high-tensile bolt with work-hardend drawing wire, Bauschinger effect appears and raises the tool life. On the other hand, this effect reduces the shank strength of bolt. This paper proposes the steel which has large Bauchinger effect at the heading of drawing wire and the aging process which reduces the Bauschinger effect in the bolt shank. Mn or Si do not raise the Bauschinger effect. Carbon raises this effect and the high cooling rate after rolling of wire is useful too. Reduction of yield strength and tensile strength of bolt shank after compression are 15-17% and 6-7%, respectively. These reductions in strength are recovered by aging. It is concluded that aging at 573K recovers the reduction of yield strength and tensile strength of bolt-shank by the compression under strain no more than 0.03. During the compression of drawing wire, X-ray diffraction half value breadth which corresponds to the dislocation density indicates constant value. This fact suggests that the number of dislocations which are newly genereted under compression is nearly equal to that which distinguishes by the Bauschinger effect.

The Effect of Mean Stress on the Fatigue Limit of High Tensile Bolts

Currently engineers use modifications to empirical rules such as the Goodman line or the Gerber parabola, including ideas about notch tip plasticity, to predict the fatigue limit of notched specimens (including bolts) at varying mean stresses. This study compares a large data set obtained from tests on bolts at many different levels of mean stress with these empirical formulations. The data show that the empirical rules are adequate for limited ranges of mean stress. Some new ideas are also presented, which improve the ability of the empirical rules to predict behaviour at high mean stress and for improved design procedures.

High-tensile bolts without heat treatment

According to DIN-ISO 898-1 high tensile bolts of class 8.8 must have a quenched and tempered structure. Therefore either quenched and tempered wire rod is used for cold heading or the bolts are quenched and tempered after the bolt forming process. This paper presents a new wire rod, which offers the chance to get comparable or even better final properties and lower production costs: a low-carbon MnSi wire rod is used as basic material. The final tensile strength is produced by drawing and cold forming. The conventional final quenching and tempering is omitted and for many cases also baking can be avoided. An increased fatigue resistance and the elimination of final straightening of the bolts are additional advantages of the new process

高力ボルト引張り接合に関する研究 : 第 2 部 Split-Tee 型引張り接合の解析 (その 2)

高力ボルト引張り接合に関する研究 : 第 2 部 Split-Tee 型引張り接合の解析 (その 2)

高力ボルト引張り接合に関する研究 : 第 2 部 Split-Tee 型引張り接合の解析 (その 1)

It is known that spring constant of the plates is the most important factor in estimating tension type joints strength. Up to present, the absence of exact solution of both range of stress distribution inside of the plates and amounts of displacement of plate surface created by fastened bolts may be accounted for a barrier in direct estimation of joints strength. Thus estimation of exact solution of these two aspects on individual plates seems to be very important in analysis of tension type joints strength. The previous report describes theoretical and numerical analysis of exact solution of above two aspects using three dimensional elastic theory, and thereafter approximate equations to be useful for practical calculation of both spring constant and range of stress distribution inside of bolted plates were introduced. Now, in this report, changes of both bolt tension and plates' bending moments of T-stub joints, which was fastened with high tensile bolts, under various external tensions were theoretically estimated by new methods using the results of the previous report. Strength of joints under various tensions were further substantiated experimentally. All experimental values were in good agreement with those obtained by theoretical computation at corresponding conditions. Therefore, simple approximate equations here introduced can be applicable for practical estimation of T-stub joints strength. Similar approach may also be applicable for estimation of strength of more complicate tension type joints.

Second Paper: An Investigation into the Effects of Pre-Heat Temperature on Ductility in a Warm Heading Process

Two-stage warm heading operations were carried out on a mild steel and three high tensile bolt materials (types 1, 2 and 4 from B.S. 3111:1959) at pre-heat temperatures in the range from ambient up to 600°C. The tests were carried out in the form of a transfer process (approximately 2 seconds delay between stages) and also as an interrupted process (approximately 30 minutes delay between stages). Artificial surface defects of various depths were machined on the heading specimens to aid measurements of the change in ductility with increase in pre-heat temperature. The method consisted of estimating the critical depth of groove which would be just on the point of fracture at the end of a particular heading operation. The steels tested were found to have low ductility at pre-heat temperatures in the range from 200°C to 300°C; at a pre-heat temperature of 600°C the steels exhibited extremely high ductility. The results suggest that rolled bar of relatively poor surface quality could be warm headed at 600°C without fracturing. A solid film of colloidal graphite and a high chlorine oil were both found to be satisfactory lubricants at all specimen pre-heat temperatures up to 600°C.

高力ボルト引張り接合に関する研究 : 第 1 部板のバネ常数設定の為の軸対称三次元弾性理論解析 (その 1)

高力ボルト引張り接合に関する研究 : 第 1 部板のバネ常数設定の為の軸対称三次元弾性理論解析 (その 1)

Design of Bolts or Rivets Subject to Combined Shear and Tension

The 1963 AISC specification introduced, in Section 1.6.3, new provisions pertaining to the combined tension and shear stresses in bolts and rivets. The formulas given in this section permit the checking of a given design but leave the design itself to a rather cumbersome cut and try procedure. The purpose of this paper is to present a simple method which enables the designer or detailer to establish the required number of bolts or rivets in a bracket connection—the most common case in which rivets or bolts are under combined action of shear and tension (see Fig. 1). The specification provides different criteria for various rivet types, high tensile bolts of the friction or bearing type and for unfinished bolts; for this reason a different analysis is required for each ofthese elements. This paper will deal, however, only with the most commonly used types, that is, ASTM A325 type high tensile bolts and A141 rivets.