Stud Bolts Research Articles

보 단부에 철판을 매립한 PC 콘크리트 보의 실험연구

In this study, an experiment was conducted to evaluate the flexural performance of steel plate embedded beams, in which the steel plate was embedded at the end of the PC beam. From the factory manufacturing stage of the PC beam, the design process of each step in which the construction and finishing loads were applied at completion was reviewed to produce a 12 m span beam. A stud bolt was installed on the embedded steel plate at the end of the beam to ensure adhesion, and the experiment was performed using two specimens with embedded depths of 250 and 450 mm. When the load was removed owing to the pre-stressing effect of the strand, the displacement recovery rate averaged 87.0%, and the stiffness gradually increased even after yielding, exhibiting trilinear behavior that was approximately 1.8 times higher than that of the yield load when the load reached perfect plasticity. Even after the 250-mm test, which was the minimum depth of the steel plate embedment in the beam end, the joint remained in excellent condition, indicating that the bonded steel plate had a minimum depth of 250 mm.

Faulty machining and micro-segregation assisted fatigue failure of cylinder head stud of a diesel generator

A detailed failure analysis of cylinder head stud bolt of a four-stroke diesel generator has been presented. The study included optical emission analysis, tensile testing, hardness testing, optical microscopy, SEM, and EDX analyses. The investigation showed that the main mechanism of failure was corrosion-fatigue. Fatigue initiation was assisted by pitting corrosion induced by faulty machining, moisture, and presence of tempered martensite and non-metallic inclusions at the surface. Propagation of the fatigue crack was encouraged by localized corrosion within the tempered martensite, non-metallic inclusions, and Mn/Cr/Mo/Si micro-segregation. Both excessive C and Mn/Cr/Mo/Si micro-segregation caused the formation of mixed microstructure of tempered martensite and fresh martensite with retained austenite. The non-uniform microstructure led to non-uniform hardness distribution and caused localized deformation during cyclic loading and promoted fatigue crack propagation.

The axial tensile performance of DSCW-RC joints with lap-spliced bars

Joints formed between double-skin concrete shear walls (DSCWs) and reinforced concrete (RC) foundations commonly utilize lap-spliced bars to transfer forces. However, the behavior and design of these critical connections have not been thoroughly investigated. This study experimentally analyzes a steel-reinforced DSCW-to-RC foundation anchorage joint under monotonic uniaxial tension loading. Seven 1:3 scale specimens were tested to examine the effects of varying lap-spliced bar diameter, steel plate thickness, and stud bolt spacing. Crack propagation, load-displacement response, and reinforcement strain were measured. The results characterize two potential failure modes: ductile steel yielding and brittle stud shearing. Steel strains developed linearly up to yielding, demonstrating uniform transmission of tensile loads. Increased plate thickness and decreased stud spacing enhanced capacity. To mitigate sudden shear failures, the number and strength of studs must exceed the expected tensile demand. New design recommendations are proposed, including minimum stud bolt shear strength and the use of confining tie bars. This study provides an improved understanding of the behavior of DSCW-to-RC foundation lap-spliced connections, enabling resistance to axial demands while avoiding brittle failure modes. The experimental data will inform future analytical models and design provisions for these critical structural joints.

Strength calculation of composite slabs by the partial shear connection method considering the friction

This paper aims to evaluate the behavior and longitudinal shear strength of the steel-concrete composite slab using the Steel Deck P75 through the partial shear connection method considering the contribution of the friction acting in the interface of the steel deck with the concrete at the region of supports. The method proposed by EN 1994-1-1:2004 for the design of composite slab systems is based in the analytical model similar to that of composite beams which allows to determine the degree shear connection between the steel sheeting and the concrete. This method allows to analyse the influence of friction at the support, in addition to the contribution of stud bolts on the mechanical resistance of composite slab. The composite slab was tested in the Federal University of Minas Gerais structure laboratory which used the semi-empirical "m-k" method to obtain its resistance. The behavior of the composite slab system was analysed through of the graphics deflections, end slips and strains, allowing the determination of its failure mode. Finally, the results obtained from the longitudinal shear resistance considering the friction at the support were applied in one practical example.

Flexural behavior of cold‐formed U‐shaped steel members encasing concrete composite beam using continues stud bolts

AbstractThe current paper presents an innovative form of the cold‐formed U‐shape steel encasing concrete composite beam (CUCB). The suggested CUCB consists of a cold‐formed U‐shaped steel encasing plain concrete beam which are connected to each other using continuous transversal threaded stud bolts. The experimental program consisted of eight beam specimens tested in the four‐point bending set‐up. One of them was a normal reinforced concrete beam and considered as a reference specimen while the remaining specimens were CUCB specimens without ordinary flexural and shear reinforcement. Four parameters were studied in this paper: (i) the thickness of the U‐shaped steel, (ii) the spacing between the stud bolts, (iii) the arrangement of the bolts, and (iv) the number of the bolt's rows. Results indicated an overall improvement in the load‐carrying capacity and stiffness of most CUCB specimens in comparison with the reference specimen. It was found that the using of three rows of bolts can significantly improve the ductility and toughness of the CUCB specimen in comparison with two rows of bolts. On the contrary, an increase in the bolt spacing entails a decrease in the CUCB specimens' toughness.

Devepopment of manufacturing methods of high strength fasteners made of two-phase ferrite-martensitic 20G2R steel

The new manufacturing methods of stud bolt M8 made of 20G2R steel with a pre-prepared two-phase ferrite-martensitic structure, providing product strength class 10.9 is presented. The use of this technology will improve the quality and strength properties of fasteners and reduce the production cost.

Upaya Peningkatan Kualitas dengan Menggunakan Analisis Siklus PDCA pada Perusahaan Otomotif

In this era of globalization, the competition in the automotive industry is getting more challenging, and consumer demands are also continually increasing. This is what encourages the automotive industry to make products as perfect as possible, one of which is minimizing the level of defects in their production lines. By reducing defects, the process will flow faster without going through the repair process. But in actuality, there are still defects found in the poses of its production. This research was conducted in the welding process in the automotive industry. This paper aims to identify defects in the welding production process in the automotive industry. Then analyze the most dominant defect, find the root cause, and improve. This study uses the PDCA cycle method. The PDCA cycle is a continuous improvement model consisting of four sequential components, Plan, Do, Check, and Action. The results of this study identified five major defects in the welding process: hole nut not centered, dents, NG stud bolts, NG parts, and non-stick spots. The average defect per month is 110 defects, and the dominant defect is the non-centered nut hole of 63.8 defects (58%). The root cause is when the part setting stopper position is unstable. The improvement made is adding a locator pin cylinder hole nut to stabilize the position. The results of this improvement can reduce welding defects to 58.5 defects per month, and the average defect hole nut is not centered by 3.5 defects (6%). So the PDCA cycle is very effective in efforts to improve product quality.

Interlayer behavior investigation of box profile shear connectors in steel-concrete-steel sandwich structures

The present study introduces box profile (BP) shear connectors for steel-concrete-steel sandwich composite structures. The shear connectors were joined to steel faceplates using slot and fillet welding. The advantages of this shear connector include unlimited thickness, easy application, high strength, and low cost compared to other available shear connectors. A total of eight experimental specimens were fabricated to evaluate the interlayer shear behavior of BP shear connectors. The effects of geometric parameters, including the BP thickness, BP width, concrete thickness, and BP configuration, on the shear behavior of the BP shear connectors were studied. The results of experiments and comparison with other shear connectors show that BP shear connectors have improved the composite behavior and interlayer shear strength. Also, the effect of geometrical parameters was analyzed on the shear strength. The BP shear connector is dependent on its width. A 20-mm rise in the width of the BP connector increased the ultimate strength and energy absorption by 76% and 41%, respectively. The use of BP shear connectors in a V-WEB configuration reduced ductility by 52% (from 501.4 to 239 kN.mm) and initial strength by 43% (from 192 to 109 kN). Therefore, V-WEB BP shear connectors are not recommended. Then, a model was offered to predict the load-slip behavior of BP shear connectors and was compared with the relations of previous researchers. Finally, the proposed shear connector was compared with different available shear connectors in terms of strength and load-slip behavior. It can be concluded that the BP shear connector had higher stiffness and ultimate strength than other shear connectors, e.g., stud bolt, bi-steel, J-hook, CSC, and headed stud shear connectors.

Effect of manufacturing defects on fatigue life of high strength steel bolts for wind turbines

This work investigates the effect of manufacturing defects induced by thread rolling on the high-cycle fatigue life of M30 class 10.9 stud bolts. High-cycle fatigue tests of two batches of nominally identical bolts show significant differences in fatigue performance between the batches. Scanning electron microscopy characterisation of defects in the form of rolling-induced microcracks in the thread root reveals a clear correlation between the defect size and the fatigue life of the investigated bolts. It is demonstrated that initial cracks present in the stud threads have a considerable effect on the slope of S–N curves. Numerical fatigue analysis shows good agreement with the experimental data. Electron backscatter diffraction is used to establish a characteristic length of microstructurally short defects in the tempered martensite microstructure. The obtained results shed light on the definition of critical manufacturing defect sizes in bolts as an essential parameter for quality control in manufacturing process.

Implementation of Period Order Quantity (POQ) Method to Minimize Material Inventory Costs of 5/8in X 90mm Stud Bolts at PT. ZTH Kasim

Inventory control is one of the important factors to ensure that a material or item does not experience excess or deficiency, this is very important because if there is a deficiency it can hinder the operational process of a company, on the other hand, if there is an excess it will cause a loss in the cost factor. So that the Supply Control factor must be really considered. At PT. ZTH Kasim has paid attention to this inventory control factor but does not take into account the costs incurred, this causes inventory control to be carried out uneconomical, so the authors try to compare it with the POQ method, where this method can properly regulate when to order what amount ordered and can save costs for controlling the provision of stud bolts 5/8 IN X 90 MM of Rp.32,920 in 2020. Because POQ is more efficient, forecasting material needs in 2021 is carried out and Inventory Control is carried out for stud bolts 5/8 IN X 90 MMs so that the order frequency is 2.4 times and the number ordered is 129 units so that it is obtained at a cost. inventory control of Rp.185,549.

Experimental tests on shallow foundations of onshore wind turbine towers

AbstractThe current effort towards the progressive switch from carbon‐based to renewable energy production is leading to a relevant spreading of both on‐ and off‐shore wind turbine towers. Regarding reinforced concrete shallow foundations of onshore wind turbine steel towers, possible reductions of reinforcement may increase their sustainability, speed of erection, and competitiveness. The article presents the results of an experimental program carried out at Politecnico di Milano concerning both cyclic and monotonic loading, simulating extreme wind conditions on 1:15 scaled models of wind turbine steel towers connected by stud bolt adapters to reinforced concrete shallow foundations embedded in a sandy soil. Three couples of foundation specimens were tested with different reinforcement layouts: (a) similar to current praxis, (b) without shear reinforcement, and (c) without shear reinforcement and with 50% of ordinary steel rebars replaced by steel fibers. Additional vertical loads were added to the small‐scale models in order to ensure similarity in terms of stresses. The test results allowed to (i) characterize the mechanical behavior of the foundation element considering soil‐structure interaction under both service and ultimate load conditions, (ii) assess the foundation failure mode, (iii) highlight the role of each typology of reinforcing bars forming the cage, and (iv) provide hints for the optimization of these latter.

Demountable Bolted Shear Connector for Easy Deconstruction and Reconstruction of Concrete Slabs in Steel–Concrete Bridges

Welded headed studs are used to connect steel girders and concrete slabs in steel composite bridges. However, environmental problems related to welded shear connectors have been reported, including noise and dust generation during the replacement and demolition of damaged or worn concrete slabs. To overcome these issues, demountable shear connectors that enable easy replacement of damaged or worn concrete slabs must be developed. However, conventional bolted shear connectors mainly use embedded nuts, which cannot be used in structures such as bridges because initial slip occurs and the stiffness and shear resistance strength are relatively low. To address these issues, this paper proposes a bolted shear connector that integrates the embedded nut part into the stud bolt and has a tapered shape at the bottom of the expansion column. For performance verification in regard to static shear strength and slip displacement, push-out tests were performed according to Eurocode-4, and the performance of the proposed stud bolt was compared to those of conventional welded headed studs and embedded nut-style bolted shear connectors. In addition, an analytical review was performed using the ABAQUS program for the 1/4 axisymmetric model of the push-out test. As a result of applying the material nonlinear model and the surface contact analysis, the load-slip displacement of each analysis model showed a tendency extremely similar to the experimental results. The proposed demountable bolted shear connector exhibited excellent shear performance and can be used as a satisfactory replacement for conventional welded studs because it meets slip displacement and ductility standards.

Torsional Overload Fracture of Twist-off Bolts During Assembly

Abstract Supposedly simple cases of failure are most often best suited to communicate the principles of component failure analysis in the field of materials engineering to a wide readership, especially to those peers in the specialist community who are just beginning to familiarize themselves with the subject. The present case of failure relates to components that failed as early as during the assembly, and more specifically, during the final assembly stage of combustion chamber components for heavy-duty gas turbine engines. Hence, they lost their functionality (in fact, the common definition of component failure). At tightening torques of the nuts opposite of the tapered heads as low as below 25 Nm, so-called twistoff bolts which, when welded into combustion chamber sheets, take on the function of stud bolts, sheared off. By way of exception, a materialographic failure analysis could show that the primary cause of the failure was not the component’s design, but the disregard of the drawing specifications during final assembly. However, on a secondary level, design deficiencies had to be mentioned, as untempered welded joints in martensitic chromium steels invariably act as metallurgical notches. If the respective part is subjected to dynamic loads, as is the case in virtually all turbo machinery, they are thus to be avoided.

Assessment of the Durability of Threaded Joints

The article deals with the determination of the resistance to cyclic loading of the threaded joints of pressure vessels and defective elements according to the failure mechanics criteria. Theoretical and experimental studies do not provide a sufficient basis for the existing calculation methods for the cyclic strength of the threaded joints of pressure vessels. The short crack kinetics in the threaded joints, a shakedown in one of the joint elements of pressure vessels, i.e., in the bolt or stud, has not been studied sufficiently. The calculation methods designed and improved within the study were based on theoretical and experimental investigations and were simplified for convenient application to engineering practice. The findings could be used to investigate the shakedown of studs of a different cross-section with an initiating and propagating crack. Value: the developed model for the assessment of durability of the threaded joints covers the patterns of resistance to cyclic failure (limit states: crack initiation, propagation, final failure) and shakedown (limit states: progressive shape change and plastic failure). Analysis-based solutions of plastic failure conditions and progressive shape change were accurate (the result was reached using a two-sided approach; the solutions were obtained in view of the parameters of the cyclic failure process in the stud (bolt) and based on experimental investigations of the threaded joints).

Experimental and numerical investigation on seismic performance of retrofitted RC columns with web direct/indirect bonding external H-section

This paper presents experimental and numerical investigations of existing reinforced concrete (RC) columns enhanced by two seismic retrofit methods, web indirect bonding and web direct bonding combined with a steel endplate. The former retrofit system is an H-shaped steel member connected to an existing RC column with anchor bolts and an infilled-concrete layer. The latter is quite similar to the web indirect bonding method but incorporates a steel endplate and a stud bolt layer additionally. Three RC columns with/without the retrofitted methods, designated BC, SC-T2, and SC-T4, were built and tested under cyclic loading. The experimental findings showed that the retrofitted RC columns were superior to the non-retrofitted specimen in terms of initial stiffness, peak strength, and energy dissipation capacity. Based on the experimental responses, finite element (FE) models were developed and verified with the experimental results. The results obtained from the simulations were consistent with those from the experiments, indicating the finite element (FE) models can reproduce the seismic responses of bare and retrofitted RC columns with slight simulation variation. Finally, a parametric analysis was carried out to investigate the effect of the material strength and length of the added components on the seismic behavior of the SC-T2 specimen.

Fractographic Study of Marine Diesel Engine Connecting Rod Stud Bolt Crack

Abstract Failures of marine diesel engine components can lead to serious consequences for a vessel, cargo and the people on board a ship. These consequences can be financial losses, delay in delivery time or a threat to safety of the people on board. This is why it is necessary to learn about connecting rod bolt failures in order to prevent worst-case scenarios. This paper aims at determining the origin, velocity and the duration of fatigue crack development of a diesel alternator engine which suffered a significant failure of one of its mains, not long after a major overhaul had been completed and with less than 1000 running hours having elapsed. It was verified with fatigue rupture of one of the four connecting rod stud bolts. Tensile tests were performed in the remaining connecting rod bolts. During this procedure, another fatigue crack in an adjacent bolt was identified. The probable root case of damage, and at the end some final remarks are presented.

STRUCTURAL BEHAVIOR OF CONNECTIONS BETWEEN CONCRETE COMPONENTS AND GUSSET PLATE WITH STUD BOLTS

Dampers are effective in ensuring the earthquake resistance of reinforced concrete (RC) buildings. Reliable connections between dampers and concrete components are critical for dampers to effectively function in RC buildings. In this study, the structural behavior of connections between concrete components and a gusset plate with stud bolts to join the damper to the RC buildings was analyzed. Component tests of the connections between the concrete components and the gusset plate with stud bolts were conducted. The specimen parameters were the arrangement of stud bolts and the presence or absence of a closing plate. As a result of the tests, the stiffness of the connections was different depending on the arrangement of the stud bolts. In addition, the specimen with the closing plates exhibited high stiffness and strength. Finally, an evaluation method for the force-displacement curve of the connections between the concrete components and the gusset plate with stud bolts is provided.

Development of Automatic Equipment for Washing and Nondestructive Inspection of Stud Bolt

Low-pressure steam turbines in a power plant are required to operate at high temperatures and under high pressures to achieve better energy utilization and better performance. Higher operating temperatures accelerate the rate of oxidation and sludge formation, so the steam turbine is periodically inspected including strict examination of the stud bolts, and it is necessary to clean the bolts by removing sludge from their screw threads. In the conventional cleaning process, the sludge has been removed by manual cleaning, which is labor-intensive and time-consuming. Therefore, this study developed automatic equipment for washing and nondestructive inspection of stud bolts using theoretical analysis and finite element analysis (FEA). An optimal clamp load to prevent sliding of the roller was calculated, and a structural analysis of the equipment under operating conditions was conducted. An optimal washing condition to maximize cleaning efficiency was proposed using design of the experiment and verified by performing washing test of prototype.

Investigation of the Behaviour of Steel-Concrete-Steel Sandwich Slabs with Bi-Directional Corrugated-Strip Connectors

The most researches on steel-concrete-steel (SCS) sandwich slabs are to control the cracking of concrete core along with losing weight, and shear connector type. In this study, the behaviour of SCS slabs with bi-directional corrugated-strip shear connectors (CSC) was investigated. One of the most important practical problems of CSCs in SCS slabs is lack of access for another end welding to the second steel faceplate. In this research, plug weld was proposed to provide partial welding of the other end of CSCs to a steel plate. For this reason, three slabs were manufactured using the normal concrete core as a control sample and lightweight concrete (LWC) core with and without steel fibres. The behaviour of these slabs was compared with the behaviour of SCS slabs with J-hook and stud bolt connectors from previous researches. The specimens were tested under a concentrated block load as quasi-statically. Based on the load-displacement relationship at the centre, failure modes, loading capacity, energy absorption, and ductility showed acceptable behaviour for CSC system slabs. There was also a good agreement between the ultimate flexural strength based on experiments and previous research relationships.

Flexural responses of steel-UHPC composite beams under hogging moment

Using ultra-high performance concrete (UHPC) in the hogging moment regions of composite beams might significantly enhance their cracking and flexural performance. In the present paper, the flexural test was performed on steel-UHPC composite beams with stud connectors (SU-S) and bolt connectors (SU-B) at the interface. Crack resistance, ultimate flexural capacity, failure modes, and deformation characteristics of SU-S and SU-B under hogging moment were investigated. The test results showed that steel-UHPC composite beams exhibited excellent cracking and flexural performance under the hogging moment. As compared to the steel-normal strength concrete (NSC) composite beam (SC-S), cracking load and ultimate flexural capacity of steel-UHPC composite beams increased by around 340% and 26%, respectively. Moreover, the length and width of cracks in the UHPC flange plate developed slowly with load. Many short and small cracks were observed, having a close spacing in the UHPC flange plate. However, ductility and rotation capacity of both SU-S and SU-B under the hogging moment were smaller than those of SC-S. Due to the bolts’ slip in SU-B, the tensile stress in the UHPC flange plate was reduced, resulting in higher crack resistance and rotation capacity than SU-S, while its flexural stiffness and ultimate flexural capacity were slightly smaller than those of SU-S. Finally, theoretical formulas were proposed for calculation of the slip moment, moment at crack width of 0.05 mm and ultimate moment of the steel-UHPC composite beams under the hogging moment. The test results verify the applicability of these formulas to predict flexural capacity of the steel-UHPC composite beams.