Middle Bolts Research Articles

Strength Optimisation of Hybrid Bolted/Bonded Composite Joints Based on Finite Element Analysis.

A finite element analysis (FEA) was conducted to examine the behaviour of single-lap quasi-isotropic (QI) and cross-ply (CP) hybrid bolted/bonded (HBB) configurations subjected to tensile shear loading. Several critical design factors influencing the composite joint strength, failure conditions, and load-sharing mechanisms that would optimise the joining performance were assessed. The study of the stress concentration around the holes and along the adhesive layer highlights the fact that the HBB joints benefit from significantly lower stresses compared to only bolted joints, especially for CP configurations. The simulation results confirmed the redundancy of the middle bolt in a three-bolt HBB joint. The stiffness and plastic behaviour of the adhesive were found to be important factors that define the transition of the behaviour of the joint from a bolted type, where load sharing is predominant, to a bonded joint. The load-sharing potential, known as an indicator of the joint's performance, is improved by reducing the overlap length, using a low-stiffness, high-plasticity adhesive, and using thicker laminates in the QI layup configuration. Enhancing both the ratio of the edge distance to the hole diameter and washer size proves advantageous in reducing stresses within the adhesive layer, thereby improving the joint strength.

Cumulative damage and bearing capacity attenuation law of anchorage structure interface under cyclic loading and unloading

The specimens of anchorage structures bonded by different anchoring materials are prepared to study the damage and reduced safety and reliability caused by the cyclic loading and unloading stress to the roadway anchorage structure. Using Fiber Bragg grating, acoustic emission monitoring and ANSYS, the anchorage structures’ bearing properties, interface failure characteristics, overall failure mode and internal influence mechanism are obtained under cyclic loading and unloading stress path. Results show that the cracks at the anchorage interface would develop and expand rapidly under this path, and the cumulative damage to anchorage structures is primarily caused by repeated residual deformation, periodic opening-expanding-closing of internal cracks, and impact vibration resulted from large-scale cyclic loading and unloading. Compared with the results under single pull-out stress, the ultimate loads of the anchorage structures bonded by H and S materials are reduced by 30.8% and 45.5%, respectively, and the radii of inner damage are increased by 1.64 and 1.67 times, respectively, showing a significant decrease in the bearing capacity of anchorage structures under cyclic loading and unloading. The anchorage structures bonded by these two materials have more prominent brittleness and weaker post-peak bearing capacity than those bonded by resin anchoring agent. Therefore, the balance between bonding strength and brittle-plastic extension characteristics shall be fully considered for the selection of anchoring materials. Five failure modes of anchorage structure are summarized: failure of the bolt-anchoring material interface, failure of the anchoring material-surrounding rock interface, fracture of the anchoring material, fracture of the bolt, and integral bulging of the anchorage structure. Besides, under the action of stress disturbance, the anchorage structure of bolt group can mobilize adjacent bolts to restrain the continuous damage and bearing capacity attenuation of the middle bolt, thus guaranteeing the overall safety and stability.

Tensile properties analysis of CFRP-titanium plate multi-bolt hybrid joints

Hybrid joints have better tensile properties than pure bonded and bolted bolts, and are increasingly used in the aerospace field. Tensile tests are carried out for the Hybrid Bonded/Bolted (HBB) joints of Carbon Fiber Reinforced Polymer (CFRP) laminate and titanium alloy plate under different bolt numbers, and the corresponding load–displacement curves are obtained. At the same time, based on Continuum Damage Mechanics (CDM) theory, which is derived from 3D Hashin failure criteria, and a Cohesive Zone Model (CZM), the tensile strength prediction model of the composite laminate-titanium alloy plate multi-bolted HBB joint was established, and the numerical simulation results were in good agreement with the experimental height, which validate the feasibility of the model. The difference in the bearing capacity of HBB joints under different numbers of bolts is compared and analyzed. On this basis, the influence of inter-bolt distance on the tensile properties of the HBB joints is explored. The results show that the double-nail HBB joints can effectively improve the end warpage and low bearing capacity of the single-nail HBB joints. The tensile failure load of the double-nail HBB joints under the standard lap width (30 mm) is 82.6% higher than that of the single nail, the tensile failure load of the three-bolt HBB joints is 34.1% higher than that of the double nail. For the three-bolt HBB joint, the joint strength is controlled by the adhesive and the external bolt, while the internal bolt is redundant, the hybrid joint can be simplified by reducing the middle bolt. The inter-bolt distance has a great influence on the failure load of the hybrid joint. Increasing the inter-bolt distance can effectively improve the bearing capacity of the structure.

Influence of Geometric and Setup Parameters of the Arrangement of Working Tools on Agrotechnical and Power Characteristics

The paper contains the analysis results of the influence of geometric and setup parameters of the plow working tools on agrotechnical indicators and traction resistance of a plow. ( Research purpose ) To determine the agrotechnical indicators of tillage quality depending on the type of a plow moldboard and determine the optimal moldboard for loamy soils. ( Materials and methods ) Agrotechnical indicators included crumbling, soil layer turnover, and the incorporation (embedding) degree of plant residues. More intensive lumpiness is observed as the content of clay particles increases. The angle of plow body setup relative to the furrow walls is changed using the middle bolts securing the plow body rack of the frame and installing additional washers on one of the two remaining bolted joints. For experiments on the influence of the inclination angle of the plow-bottom surface relative to the furrow wall, the plow bodies were located at angles of 30 to 55 degrees. ( Results and discussion ) It has been established that at angles of 30-35 degrees, the diameter of clods increases to values exceeding the permissible norm by 10-20 percent. An increase in the angle of more than 45 degrees reduced the diameter of clods to 10-30 millimeters. With an increase in angle to 50-55 degrees, shearing chips changed into shifting chips. The authors determined traction resistance of plows with various types of moldboards and identified the results of analytical calculations and experimental data in field trials using a dynamometer. Traction resistance of the plow decreases as cylinder moldboards are substituted with screw (auger-type) ones. ( Conclusions ) It has been determined that as the angle of plow body setup relative to the furrow walls increases, the size of soil fragments decrease, and shearing chips change into shifting chips. It has been proved that general-purpose and half-screw moldboards demonstrate the best agrotechnical indicators on loamy soils

Influence of bolts on seismic performance of earthquake-resilient prefabricated sinusoidal corrugated web steel beam-column joints

Earthquake-resilient structures have been widely recognized and applied in the seismic field of prefabricated steel structures due to their excellent performance. The prefabricated sinusoidal corrugated web steel beam-column joint (PSCWJ) with the earthquake-resilient design concept has been previously proposed. To study the impact caused by the bolt parameters on the seismic behavior of the new PSCWJ, five specimens were designed, with varying the number of flange connecting bolts, type of bolt holes, and interval between the middle bolts. A low cycle reciprocating load test and the finite element (FE) simulations were conducted on the specimens to determine the failure mode, energy dissipation capacity, ductility, hysteretic curves, sliding curves, strain curves, skeleton curves, and other main indexes on seismic performance. And the study indicates that the PSCWJ has excellent bearing capacity and seismic performance, the new prefabricated joint can realize the dual energy dissipation by buckling and sliding of the flange cover plate (FCP), and the number of flange connecting bolts directly determines the sliding load of FCPs. A rational interval between middle bolts can control the buckling load of FCPs and provide the joint with a satisfactory bearing capacity. The setting of slotted hole can increase the rotation and energy dissipation capacity of the joint. Further, the energy dissipation performance of the repaired specimens is stable under the low frequency constant amplitude loading, thereby ensuring that the PSCWJ can be used as a damper.

Experimental study of earthquake-resilient end-plate type prefabricated steel frame beam-column joint

In order to avoid the complex stress field of traditional beam-column joints caused by arranging end side plate or support plate on beam end, and realize the earthquake-resilient of joints, based on the plastic damage control idea, a kind of end-plate type prefabricated steel frame beam-column joint (EPPSFJ) is put forward in this paper. The new type joint mainly consists of the circular steel tube column with cantilever beam, ordinary beam, and the connecting devices. The EPPSFJ can realize stiffness control of the connection by adjusting the thickness of the flange cover plate (FCP), the distance between the middle bolts and other parameters, and make use of the plastic distortion and friction sliding of the FCP to dissipate the seismic energy, so as to ensure the basic elasticity of the structural member and realize the rapid post-earthquake repair of the joint. In the article, the low cycle load test is carried out on five specimens and one repair specimen to obtain the failure pattern, hysteresis curve and strain curves of joints etc., The impact rule of parameters such as the thickness of cantilever beam flange, the distance between the middle bolts, thickness and weakening form of FCP on the seismic performance is researched. The experimental study shows that: the joints have good seismic performance by reasonably designing parameters of bolts and the FCP, and the plastic distortion is focused on the FCP easily replaced, which make sure that plastic damage does not occur at the structural member. The repaired specimen still has great energy dissipation capacity, ductility and other seismic performance indexes, which indicates that the joint can be quickly repaired post-earthquake through replacing the FCP and other connecting devices.

Experimental study of earthquake-resilient prefabricated beam-column steel joint with L-shaped plate

The research of prefabricated steel structure have become a hot topic in international structural engineering, which accelerates its promotion and application. Based on the idea of damage control, an earthquake-resilient prefabricated beam-column steel joint (PBCSJ) has been proposed, which can make the plastic damage occur at the flange cover plate (FCP) by reasonable design of the FCP thickness, middle bolts interval and other parameters. It is ensured that no plastic damage occurs at the main components such as beams and columns. Thus, joint can be repaired by replacing the connection devices to restore its use function. In this article, four specimens are designed, and the quasi-static loading tests and the numerical simulations are conducted to the four specimens and two repaired specimens. The impact on the seismic performance caused by the FCP thickness, FCP connecting bolts number, beam gap and other parameters, as well as the post-earthquake resilience are emphatically investigated. The failure mode, hysteretic curves, skeleton curves and other main performance indexes are obtained. The study shows that: PBCSJ can dissipate energy through the FPC plastic deformation; the thickness of FCP has a relatively big influence on the joint bearing capacity and energy dissipating performance; the decreasing number of FCP connecting bolts would cause the FCP sliding; the insufficient gap of beams would cause the local plastic damage due to the extrusion of the beams. In addition, the joint before and after the repairing would have excellent bearing capacity and energy dissipating performance. The results of the refined finite element (FE) analysis basically match the test results, and can be used as an important tool for the performance study of such type of joints.

Design theory of earthquake-resilient prefabricated beam-column steel joint with double flange cover plates

Prefabricated steel structure with earthquake-resilience has become one of the hot topics in the field of seismic engineering. Based on the idea of damage control, this paper proposes a new type of earthquake-resilient prefabricated beam-column steel joint (PBCSJ) with double flange cover plates (FCPs), which is formed by a circle tubular steel column with a cantilever beam, an independent beam and a set of connecting devices in between. After the comprehensive analysis of the mechanical behaviour of PBCSJ, the formulas are derived from three aspects: the thickness of FCPs, the number of flange connection bolts and the middle bolts interval. Then the design theory of earthquake-resilient PBCSJ with double FCPs is established in this paper, and its rationality and applicability are verified by 11 groups of 57 numerical examples. The study shows that the design theory can be used to accurately calculate the yield load of PBCSJ. The sliding moment of flange connection bolts and the ultimate load of PBCSJ also can be controlled effectively. The joints designed according to this theory have superior bearing capacity and ductility, which ensures that the beams and columns are kept in elastic stage and provides preconditions for post-earthquake repair of PBCSJ.

Low cycle reciprocating tests of earthquake-resilient prefabricated column-flange beam-column joints with different connection forms

With the aim of damage control, a new earthquake-resilient prefabricated column-flange beam-column joint (PCFBCJ) had been presented for the connection between column-flange and beam-column. On this basis, the low cycle reciprocating test and finite element (FE) numerical validation were carried on the four specimens of PCFBCJ and one repaired specimen in this paper, and the hysteretic curves, skeleton curves, strain curves of these specimens were obtained. The seismic performance and earthquake resilience of the joints were studied by changing the connection form and the other design parameters such as the flange cover thickness, middle bolts interval, bolt number and shape of bolt holes. The results showed that, under the condition of reasonable design parameters, the joints had good load bearing and seismic performance whether the connection form was single or double flange cover plates (FCPs). The joints can be repidly repaired after earthquake by replacing the key energy dissipation components. The repaired joints still have good seismic performance and energy dissipation capacity. The middle bolts interval has a significant effect on the yield load and ultimate load of the joints, especially on the ultimate load of the joint. When the FCP does not slide, the shape of the holes had little influence on the energy dissipation capacity and bearing capacity of the joints.

Experimental study of earthquake-resilient prefabricated steel beam-column joints with different connection forms

Prefabricated steel structure is widely used as a kind of green building structure with life cycle significance. As the key link in steel structure design, the beam-column joint design has been deeply studied. Based on this, the paper proposes earthquake-resilient prefabricated steel beam-column joints (PSBCJs) with different connection forms. The main components of the joints are circle tubular steel column with cantilever beam and common I-beam, and the differences are the change of connection forms of flanges and webs. In this paper, five specimens were designed, and the low-cycle reciprocating test and numerical simulation were carried out on these specimens and the corresponding repaired specimens. The parameters such as the forms of flange cover plates, the forms of connecting plates, the middle bolts interval and the influence of the earthquake-resilient behavior on the mechanical properties of the joints are investigated, and the load-displacement curves, skeleton curves and damage models of each specimen are obtained. Test results and numerical analysis were mutually verified. The results of the tests showed that the new PSBCJs can effectively dissipate energy through the plastic deformation of the flange cover plates; the middle bolts interval has a great influence on the bearing capacity and energy dissipation performance of the joints; under the premise of the same main structure, the reasonable changes of the connection forms of the flange cover plates and the web connectors have little effect on the deformation mode of PSBCJs; after the completion of the loading, the main components such as beams and columns are basically kept elastic, and the seismic performance of the joints after replacing the connection devices are still favorable.

Experimental study on earthquake-resilient prefabricated cross joints with L-shaped plates

Earthquake-resilient functionality has become a leading issue in seismic engineering, and as an important component of earthquake-resilient, cross joints have become a research hotspot. A new type of earthquake-resilient prefabricated cross joint (ERPCJ) with L-shaped plates for damage control have been proposed in this study. The new type of prefabricated cross joint is constructed of a circular tubular steel column with a cantilever beam, a common beam, and a connection device consisting of a flange cover plate, L-shaped plates, and high-strength bolt groups. By controlling the thickness of the flange cover plate and the distance of the middle bolt, the rigidity of the connection can be adjusted so that the frictional sliding of the bolt and the plastic deformation of the flange cover plate can dissipate energy and ensure that the beams, columns, and other primary components do not undergo plastic failure. To study the seismic performance and earthquake-resilient performance of this new type of cross joint, three specimens were designed and fabricated. Unequal amplitude low cyclic loading tests were carried out on the three designed specimens, while 30 laps of an equivalent amplitude low cyclic loading test was carried out on a repaired specimen. The hysteresis curves, skeleton curves, and failure modes of the specimens were obtained. The effect of the distance of the middle bolt, shape of the bolt holes, and repair test on the seismic performance of the joints were investigated. The experimental results indicate that the joint can effectively utilize the plastic deformation of the flange cover plate and the sliding of the bolt for energy dissipation. Adjusting the middle bolt distance had a significant effect on the bearing capacity and energy dissipation capacity of the joint. Changing the form of the bolt hole from circular hole to slotted hole effectively improves the ductility of the joint. The repaired joint retained its good energy dissipation capability, indicating that the joint has a good post-earthquake restoring performance and can be used as a displacement-control damper.

Experimental and numerical study on the mechanical behavior of Q460D high-strength steel bolted connections

Based on static tensile test of 20 Q460D high-strength steel bolted connection joints, influences of high-strength steel material strength and bolt arrangement pattern on bearing capacity and deformation of connections were analyzed. According to differences of end distance, edge distance, and pitch between bolts, finite element modeling, theoretical calculation, and test results were compared, a quantitative analysis was carried out for mechanical property of high-strength steel bolted connections, and applicability of relevant standards was investigated. The study showed that bearing capacity and deformation of specimens for Q460D high-strength steel increased as pitch increased when bolts were under transversal arrangement. Influence of increased edge and end distance on bearing capacity of the connection was minimal after standard value of the structure was reached. Stress nephogram obtained from numerical analysis and plastic region presented symmetrical distribution with two holes bearing balanced stress, fitted curve points were dispersedly distributed, and margin of theoretically calculated value was large when EC3 standard was used. When bolts were under longitudinal arrangement, bearing capacity of the specimens only presented a linearly increasing trend as pitch increased, two holes bore unbalanced stress in stress distribution, stress borne by bolt hole at end part and its deformation were both large, and bearing capacities of end and middle bolts calculated according to the EC3 standard were relatively accurate. This study can provide a theoretical basis for design and connection structure of Q460D high-strength steel bolted connection joints.

Seismic behaviour of an earthquake-resilient prefabricated beam-column cross joint

Earthquake-resilient structures have become a hot topic in seismic research. Based on the concept of damage control, this paper presents a new type of earthquake-resilient prefabricated beam-column cross joint (ERPCJ). After a strong earthquake, the function of the joint can be quickly restored because damage is concentrated mainly on replaceable connecting parts. First, the construction and advantages of the ERPCJ are explained, and its seismic design requirements are established. Then, the theory behind the design of the ERPCJ is proposed and verified by numerical simulation using eight ERPCJ models. The hysteretic behaviour of the ERPCJ was investigated using the finite element (FE) method considering the effects of the weakening profile in the flange cover plate, the thickness and strength of the flange cover plate, the distance between the middle bolts, the gap between the beams, and the bolt hole shape. Finally, cyclic loading and repairing tests were conducted on a basic specimen, and the rationality of the design theory was verified. The seismic performance and the post-earthquake resilience performance of the joint were investigated. Numerical analysis and experiments showed that the proposed design theory could accurately predict the yield load of the ERPCJ. A reasonably well-designed ERPCJ should have good bearing capacity, collapse resistance capacity, seismic performance, and post-earthquake resilience performance. The thickness and strength of the flange cover plate, the distance between the middle bolts, and the gap between the beams have a large effect on the seismic behaviour of the joint, and so should be properly designed.

Design theory of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint

Prefabricated steel structure systems have become a new trend in the development of steel structures. In particular, earthquake-resilient steel structures have become a hot issue in the field of structural seismic research. Based on the idea of damage control and a new kind of energy-saving, material-saving and environmentally friendly sinusoidal corrugated web, this paper put forward a new type of earthquake-resilient prefabricated sinusoidal corrugated web beam-column joint (PSCWJ). Then, its constitution, its mechanics mechanism and its seismic design requirements are introduced. After considering the influence of the bolt binding coefficient, the overall bending of the binding section and the overall instability of the flange cover plate, the design theory of the earthquake-resilient PSCWJ is established. Through 55 examples of PSCWJs, the rationality of the design theory proposed in this study is verified, and a reasonable value range of the middle bolt interval on the flange cover plate is determined. During the process of theoretical derivation, the influences of many design parameters are considered, such as the section parameters of the sinusoidal corrugated web beam and cantilever beam, the thickness of the flange cover plate, the material properties of the flange cover plate, the diameter of bolts, the middle bolt interval and the weaken rate of the cover plate. Research shows that the design theory proposed in this paper can predict the yield load of PSCWJ accurately and effectively control the ultimate bearing capacity of PSCWJ. The PSCWJ designed through this theory has good bearing behaviour and ductility, which can make sure the main members, such as the beam and the column, remain in an elastic range and meet the requirements of earthquake resilience.

The dynamic analysis of a steel pipeline under a seismic shock

This paper presents the analysis of the dynamic response of a steel overground pipeline to a strong seismic shock. The scientific motivation of this study was to identify the response of connections of steel pipeline sections to a strong seismic shock. A 105-metre-long steel pipeline was the subject of this investigation. A submodelling technique was used in the numerical analysis. All details, such as bolts, flanges and the support pillar, were modelled. Both models were subjected to non-uniform kinematic excitation. An actual seismic shock was used for the excitation of the pipeline. The excitation was applied to the structure as accelerations of particular supports acting in three dimensions. The three tested values of seismic wave velocity were 250m/s, 500m/s and 1500m/s; numerical calculation was conducted for each wave speed. During analyses, the normal stresses at representative points were calculated. The analysed points were located at the top, at the bottom and at the middle bolt. The values of stresses obtained for each analysis were compared. On the basis of this comparison, it can be noted that the stresses obtained for selected points reflected the complex state of stress in the connection. The bolt deformations also show the strong bending that occurred in connection elements.

Effect of Bolts Assembly on the Deformation and Pressure Distribution of Flow‐Channel Plates in Micro‐PEMFC

AbstractThe main aim of this study is to simulate the response of a micro‐PEMFC numerically by utilizing a 3‐D FEM model while the micro‐PEMFC was assembled by three pairs of bolt along the upper and lower portions, respectively, of the end plates. The effects of different bolts locking sequences on the deformation and pressure distributions at flow‐channel plates in a micro‐PEMFC were investigated. The simulated results showed that if one locked the middle bolt either on the upper or lower portion first, then the obtained warpage, uniformities of deformation and von Mises equivalent stress were superior than those results if one locked either one of the four corner bolts first. Also, among the three pairs of bolts used for assembling the cell, the first locking bolt of the first pair of locking bolt and the first locking bolt of the rest of two pairs of locking bolt were to minimize the warpage and stress should locate on the different portions of the end plates.

Behaviour of pultruded beam-to-column joints using steel web cleats

Response of pultruded Fibre Reinforced Polymer (FRP) beam-to-column joints with steel bolted web cleats is studied through physical testing. Two joint configurations are considered with either three or two bolts per cleat leg, as per drawings in a pultruder's Design Manual. Moment–rotation curves, failure modes and potential performance gains from semi-rigid action are determined from two batches, each having six nominally identical joints. Results show that initial joint properties for stiffness and moment can possess, at 19 to 62%, an extremely high coefficient of variation. All joints failed by fracturing within the FRP column's flange outstands. Because this failure mode has not been reported previously there is a need to establish how its existence influences joint design. As joint properties for the three- and two-bolted configurations are not significantly different, the middle (third) bolt is found to be redundant. Damage is shown to initiate within the column flange outstands when the mid-span deflection of a 5.08m span beam, subjected to a uniformly distributed load, is span/500. This is half the serviceability vertical deflection limit recommended in the EUROCOMP Design Code and Handbook. The mean joint moment resistance for design is established to be 2.9kNm and this is 1.5 times the moment for damage onset.

Measurement of load distribution in multibolt composite joints, in presence of varying clearance

An experimental study is presented on the effects of bolt-hole clearance on the load distribution in multibolt composite joints. Single shear, three bolt joints were studied. The specimens were manufactured from graphite-epoxy HTA/6376, with quasi-isotropic layups. Protruding head bolts of 8 mm diameter, torqued to finger tight conditions, were used. Different combinations of clearance were obtained by using four different reamers and a purpose designed, high precision drilling jig. Instrumented bolts with strain gauges attached for measurement of shear strain at the shear plane, were used to measure bolt load distribution. Prior to use in the multibolt joints, the bolts were calibrated in single bolt joints. For assembly of the multibolt joints, a special jig had to be designed to allow simultaneous aligning of the bolt along the axis of the joint, centring of each bolt in its hole, and torquing of the bolts to a prescribed level. The results of the study show that relatively small amounts of clearance can have substantial effects on load distribution. As an example, the middle bolt in a joint of this type is normally assumed to carry less load than the outer bolts, and is therefore considered not to be under threat of failure. But in the presence of clearance the load can shift to the middle bolt, potentially causing an unexpected failure mode.

Resin acid, turpentine, and caloric content of paraquat-treated slash pine

Slash pines (Pinuselliottii Engelm.) were injected with 2% paraquat cation (weight/weight basis) and harvested after 24 months. Each stem was cut into three bolts and the amounts of resin acids and of turpentine, the net energy value, and the moisture content were measured. In the lower bolt, adjacent to the treated zone, a 984% increase in resin acids and a 2460% increase in turpentine were found. Averaged over the entire tree stem (three bolts) resin acids increased 407% and turpentine 784%. Moisture content was reduced 53.2% in the lower bolt and 28.4% in the middle bolt and increased 10% in the upper bolt. Turpentine amounts from treated and untreated trees were qualitatively similar and had an average heating value of 10 369 cal/g (1 cal = 4.1868 J). Lower moisture and increased resin of the treated trees increased the caloric content of the lower 152-cm bolt by 33.1% above controls and of the whole tree stem by 12.7% above the controls.