In this experimental research a transparent thermoplastic manufactured by the DOW Corporation and known as Surlyn is investigated for use as an interface material in fabrication of an all-glass ...pedestrian bridge. The bridge is modular in construction and fabricated from a series of interlocking hollow glass units (HGU) that are geometrically arranged to form a compression dominant structural system. Surlyn is used as a friction-based interface between neighbouring HGUs preventing direct glass-to-glass contact. An experimental program consisting of axial loading of short glass columns (SGC) sandwiched between Surlyn sheets is used to quantify the bearing capacity at which glass fracture occurs at the glass-Surlyn interface location. Applied load cases include 100,000 cycles of cyclic load followed by 12 hours of sustained load followed by monotonic load to cracking, and monotonic loading to cracking with no previous load history. Test results show that Surlyn functions as an effective interface material with glass fracture occurring at bearing stress levels in excess of the column-action capacity of an individual HGU. Furthermore, load cycling and creep loading had no effect on the glass fracture capacity. However, the load history had a nominal effect on Surlyn, increasing stiffness and reducing deformation.
The effect of using thin plies to increase the bearing strength of composite laminates has been investigated. A series of 5 laminates of theoretically identical stiffness with varying proportions of ...thin plies were manufactured using a single material system. Four specimens from each plate were tested for bearing strength and damage was subsequently characterized using an optical microscope. The results show that performance in terms of bearing stiffness, strength at onset of damage, and ultimate bearing stress increase proportionally with the increasing amount of thin plies within the stack. Shifting from a 100% conventional ply laminate to a 100% thin-ply laminate gave an increase of 47% in the strength at onset of damage. Placement of the thin plies within the stack was also shown to be important for strength at initial onset of damage. Microscopic examination of the failure modes for all samples showed fiber kinking, localized to the center of the hole, to be the dominant failure mode regardless of the stacking sequence.
•Calculation methods for the bearing stress of exposed column bases are studied.•A full-scale experiment is conducted to normalize experimental results.•A method to obtain the full plastic moment is ...proposed.•A database of experimental results on exposed column bases is established.•A more conservative calculation method for the bearing stress is proposed.
Exposed column bases are widely used in low-to-medium rise steel structures. As they can transfer all the loads from the superstructure to the sub-system, exposed column bases are in the most severe state of stress. Further, they show various failure modes because of the complex stress transfer mechanism. One of the failure modes stated in the Japanese design recommendations are the yielding of anchor rods. To ensure the yielding of anchor rods, the bearing failure of foundation concrete must be prevented. However, studies on the bearing stress of exposed column bases are limited. In the present study, the existing calculation methods for the bearing stress of exposed column bases are summarized. A database of previous experimental studies on exposed column bases was also established to analyze the calculation methods. To normalize the experimental results in the database, an experiment was conducted on full-scale, exposed column bases, and a method was proposed to obtain the full plastic moment for further analysis. With the proposed method, the accuracy and applicability of the calculation methods were verified. Furthermore, considering the design philosophy in Japan, a more conservative method to calculate bearing stress was proposed.
Taking the filling mining in Yungang Coal Mine 8402 working face as the background, firstly, five gangue slurry with different proportions were prepared, and bleeding rate, setting time and uniaxial ...compressive strength tests were tested. Reasonable gangue slurry ratios were selected according to the requirements of use and cost, and the design of filling hydraulic support and filling mining technology was carried out. Considering the change of rock mass mechanical parameters with mining stress, based on Hoek-Brown model, FLAC3D software was used to study and analyze the spatial-temporal evolution law of deformation and failure of roof overburden in 8402 working face with or without filling. The results show that: when the dosage of cement and fly ash is 180 kg/m3 and 210 kg/m3 respectively, it can meet the requirements of filling mining and cost of 8402 working face in Yungang Coal Mine at the same time; under the condition of no filling, the 8402 working face has a periodical pressure step of 18-25 m, and t
The paper presents experiments on connections with one and two bolts made of mild steel grade S235. The results are compared with the tests on connections made of high strength steel. The test ...results are substantiated with numerical parametric analysis. The effect of bolt bearing is thoroughly analysed. The bearing strength at bolt holes according to standard EN 1993-1-8 is critically evaluated and a modified design check is proposed. The modified check is conceptually the same as the current one, but it is simpler, less conservative and it is in better correlation to the test results. The block shear strength and net cross-section strength are also discussed and modifications to the EN 1993 design rules are given.
•Tests on bolted bearing-type connections•Comparison of mild steel and high strength steel connections•Bearing strength at bolt holes compared to EN 1993-1-8 and modifications are proposed.•Modifications to net cross-section and block shear EC3 rules are given.
The use of mechanically-fastened fibre-reinforced polymer (MF-FRP) strips has been recently proposed as a possible alternative solution to the most common externally-bonded (EB) sheets and laminates. ...Although several applications of MF-FRP strengthening on reinforced concrete (RC) structures are already available, further experimental and theoretical studies are needed for both achieving a thorough knowledge of their mechanical behaviour and formulating sound design rules.
The present paper deals with identifying the relationships between the actual bearing stress transferred by the fastener and the corresponding relative displacement (slip) at the FRP–concrete interface. For this purpose, a simplified numerical model is firstly formulated to simulate the experimental behaviour observed from direct shear tests (DSTs) recently performed by the Authors on FRP laminates fastened to concrete blocks with screwed steel anchors. Then, the numerical model is employed within an optimisation procedure aimed at indirectly identifying the relationships between the force applied on the single fastener and the corresponding displacement. Finally, the results of this inverse identification procedure are compared for pointing out the differences possibly arising in terms of interface stress–slip relationship as a result of different detailing in the fastening system. In particular, the cases of fasteners with or without steel washers are investigated.
The working face 1303 passing through the gob was studied by means of field investigation, laboratory test, theoretical analysis and numerical simulation, taking the engineering geological conditions ...of 1303 working face in the north wing of a mine in Datong, Shanxi Province as the background. The results show that the influence range of the leading bearing stress of the coal wall in the working face is 39.2 m, and that of the side bearing stress of the tunnel is 9.6 m. When the width of the coal pillar L is less than 48.8 m, the bearing stress begins to overlap; when the width of the coal pillar L is reduced from 50 m to 10 m, the peak stress keeps increasing continuously, and when the width of the coal pillar is 10 m, the peak stress is the largest, which is the critical bending stress width of coal pillar; when the width of coal pillar is less than 10 m, the critical yield state of coal pillar changes from full yield state to full yield state, and the peak stress shifts to the outer side of the goaf, so it
Purpose
Bearings are critical components used to support loads and facilitate motion for rotating and sliding parts of the machinery. Bearing malfunctions can cause catastrophic failures. Hence, ...failure analysis and endeavors to improve bearing performance are essential discussions for worldwide designers, manufacturers and end users of vital machinery. This study aims to investigate a type of roller bearing from the railway industry with premature failures. The task arises because locomotives’ maintenance and service life quality are vital to railway operations while providing transportation services for the nation. To assist in maintaining the designated locomotives, the present study scrutinizes the causes of failure of heavy-duty roller bearings from locomotive bogie axleboxes.
Design/methodology/approach
It is intended to inspect this bearing service life and statistically scrutinize its design parameters to reveal the failures’ shortcomings and origins. The significant measures include examinations of their failures’ primary and vital factors by comparing them with a real-life service history of 16 roller bearings of the same type. The bearings come from the axleboxes of a locomotive bogie with an axle load of 20 tons. The bearing loads are estimated using the EN13104 standard document and confirmed by the finite element method using ABAQUS engineering software. To validate the finite element modeling results, the bearings’ stress analysis is performed using the Hertzian contact theory that demonstrated perfect conformity. The said methods are also used to search for the areas susceptible to failures in these bearings. With the inclusion and exploitation of the bearing maintenance conditions and the logbook recordings of the locomotives for the past seven years, the critical cause for this type of bearing’s failures is surveyed and discussed.
Findings
With the inclusion and exploitation of the bearing maintenance conditions and the logbook recordings of the locomotives for the past seven years, the critical cause for this type of bearing’s failures is surveyed and discussed. As a crucial result, it is found that deprived maintenance and inadequate lubrication are the root causes of the loss of the selected bearings.
Originality/value
For the designated locomotives, the origins of the heavy-duty roller bearing failures and its design shortcomings are revealed by examining and comparing them with a real-life service history of many of the same types of bearings. The novelty of the research is in using the combination of the methods mentioned above and its decent outcome.
Wear of polyethylene bearings represents a limiting factor in the long-term success of total elbow prostheses. Bearing stress is 1 factor contributing to accelerated wear. Physiological loading of ...total elbow prostheses and implant design influence upon bearing stresses have not been well described. This study evaluates bearing stresses in 3 commercially available implant designs under loads associated with daily living.
Motion tracking from a healthy volunteer helped establish a musculoskeletal model to simulate flexor and extensor muscle activation at 0°, 45°, and 90° of shoulder abduction with a 2.3-kg weight in hand—forces and moments were measured at the elbow. Resulting physiological joint reaction forces and moments were applied to finite element models of 3 total elbow bearing designs (Coonrad/Morrey, Nexel, and Discovery) to evaluate contact area and polyethylene stresses.
Increasing shoulder abduction resulted in minimal changes to the elbow joint reaction force but greater joint moments. All implants showed greater peak stresses with increasing shoulder abduction—elbow varus. Discovery and Nexel achieved greater contact area (23% vs > 100%) and demonstrated up to 39% lower peak polyethylene stresses compared with the Coonrad/Morrey design.
Shoulder abduction results in a varus moment at the elbow. Newer bearing designs (Nexel and Discovery) provide a combination of higher contact area, improved load sharing, reduced edge loading, and lower stresses through elbow range of motion when compared with a cylindrical hinge-bearing design (Coonrad/Morrey).
Although the Coonrad/Morrey is a clinically successful prosthesis, our physiological loading model shows that Discovery and Nexel provide greater contact area, better load sharing and lower peak stresses. This may lead to a decrease in polyethylene wear rates and the eventual risks of osteolysis and aseptic loosening. Further studies are needed to determine how these findings translate clinically.
Current study illustrates the effect of interference on closely spaced square footings in loose, medium and dense sand beds using experimental and numerical studies. Experimental results suggest that ...with increase in the clear spacing interference decreases and after 2B spacing between the footings, the interference effects are almost zero, where B is width of the footing. The interference effect is quantified as Interference Factor, IF and is defined as ratio of ultimate bearing pressure of an interfering footing to that of an isolated footing. Maximum Interference Factor of about 1.25 is observed in dense sand. Interference is attributed to increase in confinement pressure due to the interaction between the failure zones of interfering footings. To this end, FLAC 3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) models were developed and numerical simulations have been carried out. The effects of frictional angle and dilation on interference factor are presented.
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