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This Special Issue of the International Journal of Fatigue contains selected papers presented at the International Conference on Multiaxial Fatigue and Fracture held in Seville, Spain, on 1–3 June 2016.

The quasi-periodic irregularity that appears on the running surface of rails, which is known as rail corrugation, is reviewed here. The review concentrates on particular characteristics of different types of corrugation, understanding its root causes and proposing practical methods for avoiding or alleviating the phenomenon. Different types of corrugation can be identified by their ‘wavelength-fixing’ and ‘damage’ mechanisms. Six different types of corrugation are thus identified, for four of which wear is the ‘damage mechanism’. The most common wavelength-fixing mechanism is the P2 resonance of a vehicle’s unsprung mass on the track stiffness, which is significant for three of the six types of corrugation. An understanding of this phenomenon and development of efficacious treatments have advanced significantly in the last 15 years as a result of research having been applied and the effects accurately and comprehensively monitored.

An impact-wear testing rig was designed to study the wear occurring between solid materials undergoing repetitive impulsive loading combined or not with simultaneous transverse sliding. The apparatus allows to measure impact forces and relative velocities. Besides, numerical simulations of impact-sliding situations were performed to obtain the relevent internal stress distribution. Both experimental and calculation results will allow to validate an improved impact-sliding wear model. The present paper describes the testing apparatus and procedures and includes preliminary results from the tests and numerical calculations.

The effect of journal misalignment on the performance of a big-end connecting-rod is analysed in this paper. The misalignment considered varies in magnitude and direction during all the cycle up to contact between the shaft and the bearing. The numerical procedure incorporates misalignment velocities. The technique used for bearing characteristics evaluation (minimum film thickness, friction torque, axial flow) is an extension of the mobility method of BOOKER.

Fibers such as fabric and bristles can be readily fabricated into a variety of configurations that are compliant and responsive to high-speed or lightly loaded systems. These configurations can be linear, circular, or contoured linear or circular. In this paper visualization and characterization of the complex flow fields in simulated linear bristle configurations as applied to brush seals (bearings) are explored. The full-field flow tracking (FFFT) method is used to visualize the flow field and bristle dynamics, which were nonintrusively determined and graphically reconstructed. Visualization of the flow field revealed regions that are characteristically river, jetting, vortical, cross, and edge flows and exist upstream, downstream, or within the brush. Such flows are caused by variations in fiber packing and stiffness that are both spatial and temporal and strongly influence leakage, stability, and load capacity. Potential applications of brush seals are described herein, and in the appendix a brush seal system design procedure is provided that compares favorably with brush seal leakage results.

This paper presents experimental measurements from laboratory dynamometers of the dependence of the life of automotive timing belts on belt torque and total tension in the transmission of power between two crankshaft sized (19 tooth) pulleys, each with an angle of wrap of 180°. Failure observations of tooth root cracking and of worn belt covers are also presented. Contact loads between belt and pulley teeth have been calculated and it is found that in the conditions of the present experiments tooth load at exit from the driven pulley is the critical load controlling life by tooth root cracking: assuming that this remains the critical load, predictions are made of the effect on life of changing belt tension, pulley size and angle of wrap.

The purpose of this paper is to reveal the relation between flexibility and clearance of oil film by a co-rotating bearing (bush is rotating together with shaft in the same direction and rotation rate), which can be used for sharing load equally in planetary transmission of vehicle. The authors have adopted a theoretical approach of infinite width bearing and explained the characteristics of oil film for co-rotating bearing. Using the numerical calculation to solve the non-linear equation, the authors have gotten the results on finite width co-rotating bearing. By experiments, the relations between flexibility and clearance of oil film for co-rotating bearing are presented by charts in different clearance, rotation rate and load. A good consistency of the results between experimental and numerical calculation result is gotten.

Experimental investigations on connecting-rod bearings in operating engines required the use of a mechanical scissor linkage to support the wires carrying the electronic signals. In many applications, one end of the linkage is attached to the big-end bearing cap by a yoke, the other end being fixed to the engine frame. The mass and inertia of the linkage modify the load acting to the bearing and change the bearing characteristics. The effect of the mechanical linkage is estimated by carrying out both rigid and elastic bearing calculations with and without a contribution from the linkage to the connecting-rod load. The loads arising from the yoke and links on the connecting-rod were calculated as a function of crankangle for different crankshaft speeds. The calculations showed that the linkage and yoke increase the inertial part of the load diagramm by about 10% and modify the orbit of the bearing center at small eccentricity ratios.

The current state of advancement of the analysis of layered media, subject to repeated contact loading, and containing a flaw, is given. References are included to contributions to component parts of the analysis of this configuration, and an indication made of how they might be amalgamated to form the desired solution. The goal of such an analysis is the determination of the conditions under which a layered surface might fail, when subject to rubbing or rolling contact. Also, the rate of detachment of a badly-adhered layer should be predictable, and the combination of materials which elastically give rise to a mild state of internal stress found.

The analyses was carried out for dry contact tribosystems to elucidate the notorious uncharacterized relationship between the coefficient of friction, wear, and sliding velocity as functions of the tribotesters global dynamic properties: its mass, imbalance, stiffness, frequency, etc. Since the presence and level of dynamic loads are elevated by an order of magnitude in the modern tribotesters, dry contact, high speed rolling/sliding and low resilient tribomaterials are the subject of study. Two types of tribometers, pin-on disk and disk-on-disk, have been considered for evaluation in order to determine: 1) dynamic forces due to runout of the spinning disc specimen; 2) load wear and coefficient of friction measurements and their interlocking relationship with item 1. The significance of the analyses lies in the prediction of dynamic loads in the contact surfaces of the tribomaterials due to the runout (static, dynamic and transient) of the specimens; where the coefficients of friction and wear values contain a certain degree of error in a complex form. The results of analyses and theoretical models backed by experiments offers a guide towards the correction, measurement and design methodology of such tribotesters.

In practical applications a rubber-like is often deposited on the internal surface of the housing to improve the bearing performance. In the present work, the influence of this layer on the bearing static and dynamic behaviour is examined by taking into account the housing deformation. A parametrical study is carried out to evalute the influence of different types of housings. It is found that the transmissibility is under-estimated in the case of rigid bearings and that a critical layer thickness exits for which the transmissibility is maximum.

This paper presents experimental data on the performance of parallel plate thrust bearings for a range of loads, speeds and inlet oil temperatures. Several aspects of bearing operation were investigated, including the possible effects of a tapered edge at the inlet to the pads. A careful mapping of the temperature field provided insight into the mechanism of generating hydrodynamic pressures in parallel plate thrust bearings. These temperatures on one hand support the postulate that thermoelastic distortion induced by the temperature gradients normal to the fluid film and the bi-metallic babbitt-metal assembly is responsible for the load capacity of parallel plate surfaces. On the other hand, past and recent experience indicated that a wide spectrum of tribological interactions cannot be treated by the separate approaches that have always been assigned to hydrodynamic action-morpho-morphological effects are at work.

Pivoted-pads thrust bearing are commonly used to support axial load rotating machinary. Analysis of such bearing is complicated by the ability of each pad to pivot, as the rotor is displaced and to translate axially due to the flexibility of the pad support. This leads to dependance of linearized stiffness and damping coefficients on rotor vibrational frequency, pad inertia and support dynamic characteristics. This paper describes an approach based on the pad assembly technique often used to devlop pad journal bearings. A reduced matrix (3,3) can be devoloped once a vibrational frequency is assumed. Conclusions on the role of pivot support and mass pad are derived.

In this paper, two types of the externally pressurized, gas lubricated and circular thrust bearings with the flexible surface are purpose for the purpose of developing the high performance bearings. Their static and dynamic characteristics have been theoretically derived and the effects of the flexiblilties of the bearing surfaces on them have been made clear. From the calculated results, it was discussed which type of the bearings was better in the practical applications, and one of these two types of the compliant surface bearings have been recommended as the high performance bearing.

The purpose of this paper is to report the results of an extensive series of tests on a special tilting pad thrust bearing. The primary interest was to determine the effects on bearing performance of using circumferential pivot locations outside the normal range of 50 to 60% of the pad arc, from the leading edge. Secondary results were also obtained from tests with pad support disks of various diameters, and with pads of different thicknesses.

In this paper, the theoretical and experimental investigations on the static and dynamic charactristics of tilting pad bearing are described. The experiments for indetifying the dynamic properties of journal bearing have been performed by using the machanica PRBS exciter. Good agreement between the measured and the calculated value of the static and dynamic properties has been shown. Either calculation or experiment justifies that the dynamic coefficients of tilting pad bearing vary versus the exciting frequency. It is demonstated in practice that the system under testing can be exceted validity within a wide frequency range by means of mechanical PRBS exciter.

Experimental structures have been built and tested which utilize polyester-impregnated, paper-laminated urethane foam board as the principal stress-resisting material. These structures have been found adequately strong for the construction of light industrial and residential buildings. Material properties are in some instances an advantage; in others a restriction. A two-story prototype building has been constructed which shows performance characteristics similar to conventional wood-frame structures.

A discussion is presented concerning three kinds of pressure boundry conditions at the inlet edge of hydrodynamic thrust bearings under the turbulent operating conditions including the inertia effects. The one-dimensional turbulent lubrication equation considering the inertia effects is solved for infinitely long slider bearings, in which three kinds of pressure boundry conditions are applied at the inlet edge of the bearings, in accordance with three types of lubrication conditions, namely: flooded condition, overflooded condition, overflooded condition and starved condition, and an analytical solution for each condition is presented for the plane slider bearings. Some results are indicated in graphical form and the relationship between three kinds of pressure boundry conditions and the static characteristics of the bearings are discussed.

Publisher Summary This chapter describes the construction of a flat-plate collector. It describes a workshop that was organized to explain the simple techniques involved in building two types of collectors: (1) solar still and (2) solar cabinet dryer for agricultural purposes. The collectors consist of “roll bond” galvanized and serpentine soft copper piping on copper plate. For making the collector, the upper and lower sheets are cut in specific sizes. The sheets are clamped onto each other and bolt holes drilled. The connector holes are drilled in the lower sheet to which the connectors are attached. The gasket rubber is cut into 3/4′′ × 3/4′′ pieces and holes drilled to accommodate the bolts. With the use of silicon sealant on the lower sheet the gasket rubber is glued in place. Now the upper sheet is placed over the lower and all the bolts put in place. The edges are then soldered and the plate is tested for water tightness. The plate is thoroughly cleaned to remove flux and dirt using vinegar and emery paper is used to sand down the top surface.

The paper investigates the influence of biaxial loading on punching resistance at square and elongated edge columns of flat slabs which is virtually neglected in the literature. In the absence of experimental data, the influence of biaxial loading is determined using nonlinear finite element analysis (NLFEA) with 3D solid elements. The resulting baseline punching resistances are compared with the predictions of various implementations of the Critical Shear Crack Theory (CSCT) including a Joint Shell Punching Model (JSPME) in which punching failure is simulated using nonlinear joint elements inserted between the nodes of nonlinear shell elements located around the punching control perimeter. The failure criterion of the JSPME, which is most suited for structural assessment, implicitly accounts for the effect of biaxial loading unlike the original (classic) and closed form versions of the CSCT. The classic CSCT indirectly accounts for loading eccentricity by reducing the punching control perimeter by a multiple ke which is determined in this paper using shear field analysis. Conversely, the closed form CSCT, which is adopted in the draft for the next generation of Eurocode 2 (EC2), enhances the design shear force by a multiple β. The paper uses experimental data to determine an expression for β for edge column connections subject to inwards eccentricity normal to the slab edge. Subsequently, shear field analysis on representative flat slab to edge column connections is used to extend this expression for β to edge column connections subject to biaxial eccentricity. NLFEA simulations with 3D solid elements are used to validate the predictions of the JSPME, the shear field methodology used to determine ke in the classic CSCT and the proposed expression for β in the closed form CSCT. Reasonable agreement is achieved between all these analysis methods. The main advantage of the JSPME over NLFEA with 3D solid elements is its increased computational efficiency which makes it more suitable for the assessment of large structures.

For thousands of years, arches have been used as durable structures that are easy to build and that rely on gravity for their inherent stability. Since then, many researchers and engineers have studied their stability either when subjected to gravity or inertial loading. Currently, given the Insight mission to Mars and the ambitious Artemis program to the Moon, it has become apparent that there will soon be the need to design and build the first resilient extraterrestrial structures and arches represent an ideal option for such structures. This paper focuses on the stability of parabolic arches with different embrace angles subjected to different levels of equivalent inertial loading in low-gravity conditions. The results are contrasted with the well-studied circular arches. More specifically, this investigation employs variational principles to identify the imminent mechanisms and numerical methods based on the limit thrust line concept in order to estimate the minimum required thickness of parabolic arches for a given loading and in different gravitational fields. The paper shows that although parabolic arches can be much more efficient than their circular counterparts for gravitational-only loading, this is not the case for different combinations of inertial loading and embrace angles where the opposite can be true. It highlights the dominant effect of low-gravity conditions on the minimum thickness requirements for both types of arches and considers the effect of a potential additional infill for radiation shielding. Furthermore, this study reveals a self-similar behaviour, introduces a “universal” inertial loading and showcases, through the use of master curves, the areas where the parabolic arches are more efficient than their circular counterparts and those where the opposite is true. These areas can be used for the preliminary design of such structures. Additionally, the paper identifies hidden patterns associated with the developed mechanisms between the two different geometries for the different gravitational fields. Finally, it presents a case study where the need to optimise the structural form of extraterrestrial structures becomes evident.

The aim of this paper is to explore the potential use of advanced composite materials as an alternative material to conventional steel to design and fabricate a lightweight fiber reinforced polymer (FRP) guyed towers. Both theoretical and experimental testing are involved. The paper offers recommendations for the design of composite towers using various non-linear finite element models. It contains a comparative cost analysis between an 81 m composite and a steel guyed tower both designed to resist identical loading conditions. The paper results confirmed that FRP tower creates more economically viable alternatives and sustainable solutions to steel towers in the future. Keywords: FRP, Guyed, Tower, Composite, Steel, ANSYS

This paper accompanies the paper titled "Experimental validation for the application of the flat jack test in cob walls" presented by the same authors to the Construction and Building Materials Journal [1]. It contains data collected during the consolidation process of six cob wallettes and data collected after single and double flat jack test were applied for the first time to a set of cob wallettes at the laboratory facilities of the Department of Civil, Structural and Environmental Engineering at Trinity College Dublin. The data served to estimate the value of the dimensionless geometrical efficiency constant, Ke , and cob´s mechanical properties, namely, Young's modulus, Poisson's ratio and compressive strength. The detailed information presented here may be of interest for verification and replicability purposes.

This paper deals with contact analysis of rolling bearings. A new mathematical model and numeric method are presented in this paper for the purpose of contact analysis of rolling bearings based on the principle of mathematical programming method. Three-dimensional (3D), finite element method (FEM) is introduced to calculate deformation influence coefficients and gaps of assumed pairs of contact points between the contact surfaces in the mathematical model. Special software is developed to realize numeric calculation procedures of the contact analysis. With the help of the developed software, loaded bearing contact analyses are conducted for a deep groove ball bearing and a cylindrical roller bearing. In the case of the ball bearing, it is found that calculated contact pressure on the ball surfaces is correct elliptical distribution (usually called contact ellipse). This result is more reasonable than the results obtained by commercial software SolidWorks and other researchers. In the case of the roller bearing, it is found that edge-loads (non-Hertz contact that cannot be analyzed with Hertz theory) on the roller surface are analyzed when the roller is not crowned. It is also found that the edge-loads disappear and contact pressure on the roller surface becomes uniform distribution when the roller is crowned with Johson-Gohar curve. Since the most important features (contact ellipse and edge-loads) of the bearing contacts are analyzed successfully by the developed software and these results cannot be obtained simply by general methods, the mathematical model and numeric method presented in this paper are of practical meaning in engineering design and the developed software can be used as a tool for contact strength and rigidity calculations of the rolling bearings.

The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence on existing tunnels such as displacements of the lining and additional loads on the lining. In this paper, three-dimensional numerical parametric study is performed to explore this complex interaction. This study investigates the effects of different parameters that may affect the tunnel response. These parameters are: excavation sequence method, horizontal/vertical stress ratio, slope angle, and tunnel diameter. This study shows that the mining sequence affects the stability of the tunnels. The open-pit mining activities lead to both higher axial forces in rock bolts and normal forces and bending moments in the lining. The results of the analysis also demonstrate that the mining sequence causes tunnel heave and significant tensile forces in the lining. Based on the study in this paper a better understanding of the interaction between open-pit mining sequence and tunnels will be obtained. Keywords: Three-dimensional, Numerical parametric study, Existing tunnel, Open-pit mining sequence, Modeling

Timber-concrete composite (TCC) bridges represent an attractive structural system due to the synergistic use of its wood and reinforced-concrete constituent components. However, their relatively large flexibility limits their application for larger spans. This paper presents an alternative solution for TCC bridges involving the implementation of post-tensioned under-deck tendons. Based on a series of design and numerical studies, the advantages of the newly proposed system for 30-m, 60-m and 90-m spans are evaluated. This paper shows that the incorporation of under-deck post-tensioning changes the critical limit states governing the design of TCC bridges, and allows for a significant increase in their slendernesses at medium and long spans. Timber’s shear-deformation contribution to the vertical deflection of TCC bridges is significant and should be accounted for, especially when the span/depth ratio ( l / h ) is less than 20. However, this additional deformation can be neglected when stay cables are implemented, especially for bridges with medium and long spans. In order to achieve a more efficient structure, it is proposed that concrete-to-timber shear connections with an efficiency coefficient ( γ ) greater than 0.8 be used. Finally, the best practical eccentricity of the under-deck tendons and the best location of the deviators are determined on the basis of parametric analyses.

Latent Heat Thermal Energy Storage Systems (LHTESS) containing Phase Change Material (PCM) are used to establish balance between energy supply and demand. PCMs have high latent heat but low thermal conductivity, which affects their heat transfer performance. In this paper, a novel fin array has been optimized by multi-objective Response Surface Method (RSM) based on discharging process of PCM, and then this fin configuration is applied on LHTESS, and comparison between full discharging time by applying this fin array and LHTESS with other fin structures has been carried out. The employed numerical method in this paper is Standard Galerkin Finite Element Method. Adaptive grid refinement is used to solve the equations. Since the enhancement technique, which has been employed in the present study reduces the employed PCM mass, maximum energy storage capacity variations have been considered. Therefore phase change expedition and maximum energy storage capacity have been considered as the objectives of optimization and the importance of second objective is indicated which is proposed as the novelty here. Results indicate that considering maximum energy storage capacity as the objective of optimization procedure leads to efficient shape design of LHTESS. Also employing optimized V-shaped fin in LHTESS, expedites discharging process considerably in comparison with the LHTESS without fin.

Reliability-based safety factors for metallic strip flexible pipes(MSFP) subjected to external pressure are calibrated in this paper. The partial safety factors of such pipes are obtained by introducing a target reliability index and using a combination of Monte-Carlo simulation and FORM. The relationship between the safety factors and the coefficient of variation for key basic variables as well as the impact of different distribution types for both the resistance and load effect parameters on the calibrated results are investigated. Recommended design safety factor for MSFP is given similar to the widely used design safety factor for conventional metallic pipes. The calibration process presented in this paper is relatively easy to understand and to carry out. This also applies to cases with multiple components and even requiring complex iterations in relation to the mechanical model. The results obtained here can provide some guidance in connection with manufacturing procedures at the initial design stage of the MSFP.

WOS:000417667000015; International audience; Composite material aircrafts are protected against lightning on the basis of complex and expansive lightning strike experimental plans aiming at designing optimal protections. The paper aims at reducing the number of lightning strike tests on protected and painted composite panels. An analytical calculation is presented that gives the characteristics of an equivalent mechanical impact configuration based on an assessment of the typical time scale of energy deposit and kinematic behaviour during a lightning strike test. The paper presents our analytical hypotheses and calculations, as well as experimental lighting strikes and mechanical impact settings and results. The method is shown to give an acceptable approximation of both the kinematics and the delamination surface.

Gear tooth surface wear is a common failure mode. It occurs over relatively long periods of service nonetheless, it degrades operating efficiency and leads to other major failures such as excessive tooth removal and catastrophic breakage. To develop accurate wear detection and diagnosis approaches at the early phase of the wear, this paper examines the gear dynamic responses from both experimental and numerical studies with increasing extents of wear on tooth contact surfaces. An experimental test facility comprising of a back-to-back two-stage helical gearbox arrangement was used in a run-to-failure test, in which variable sinusoidal and step increment loads along with variable speeds were applied and gear wear was allowed to progress naturally. A comprehensive dynamic model was also developed to study the influence of surface wear on gear dynamic response, with the inclusion of time-varying stiffness and tooth friction based on elasto-hydrodynamic lubrication (EHL) principles. The model consists of an 18 degree of freedom (DOF) vibration system, which includes the effects of the supporting bearings, driving motor and loading system. It also couples the transverse and torsional motions resulting from time-varying friction forces, time varying mesh stiffness and the excitation of different wear severities. Vibration signatures due to tooth wear severity and frictional excitations were acquired for the parameter determination and the validation of the model with the experimental results. The experimental test and numerical model results show clearly correlated behaviour, over different gear sizes and geometries. The spectral peaks at the meshing frequency components along with their sidebands were used to examine the response patterns due to wear. The paper concludes that the mesh vibration amplitudes of the second and third harmonics as well as the sideband components increase considerably with the extent of wear and hence these can be used as effective features for fault detection and diagnosis.

This paper provides a quantitative assessment of the racking performance of partially anchored timber framed walls, based on experimental tests. A total of 17 timber framed wall specimens, constructed from a combination of materials under different load configurations, were tested. The experimental study was designed to examine the influence of a range of geometrical parameters, such as fastener size and spacings, wall length, arrangement of studs and horizontal members, as well as the effect of vertical loading on the racking strength and stiffness of the walls. The experimental results were then compared with results obtained from design rules, as given in the relevant European standards, to determine the racking performance of the walls, and are discussed in the paper.

In the last research [S. Li, Effects of machining errors, assembly errors and tooth modifications on load-carrying capacity, load-sharing rate and transmission error of a pair of spur gear, Mech. Mach. Theory 42 (2007) 698–726], effects of machining errors, assembly errors and lead crowning on tooth surface contact stresses (CS), root bending stresses, load-sharing ratios (LSR) and transmission errors of a pair of spur gears were investigated through performing loaded tooth contact analysis (LTCA) with developed finite element method (FEM) programs. But this research couldn't investigate the effects of tooth profile modification and lead relieving on tooth engagements. Also, the effects of machining errors, assembly errors and tooth modifications on tooth mesh stiffness (MS) couldn't be investigated. So, as a continuous study of the last research, this paper investigates the effects of tooth profile modification and lead relieving on tooth engagements of a pair of spur gears and the effects of misalignment error of gear shafts on the plane of action, tooth lead crowing and transmitted torque on tooth MS. An arc curve is used to modify tooth profiles of a pair of spur gears in this paper. This is because this method is used very popularly for the spur gears. Methods used in the last research are also used here to investigate the effects of the tooth profile modification, lead relieving and transmitted torque on tooth engagements. Based on the results, it is found that the tooth profile modification and lead relieving have significant effects on tooth CS, LSR and MS. It is also found that transmitted torque has a little effect on tooth MS, but has no effect on LSR of the gears. For the lead-relieved gears, calculation results show that edge-loads happened at the joint parts of the relieved part and the non-relieved part of tooth lead when the lead is relieved with straight lines. Since the edge-loads resulted in greater contact stresses at the joint parts and weakened tooth contact strength, attention must be paid to the lead relieving. It is necessary to reduce the edge-loads as small as possible through making the joint part smooth when the lead relieving is made.

Due to advances in numerical modelling, it is possible to capture complex support-ground interaction in two dimensions and three dimensions for mechanical analysis of complex tunnel support systems, although such analysis may still be too complex for routine design calculations. One such system is the forepole element, installed within the umbrella arch temporary support system for tunnels, which warrants such support measures. A review of engineering literature illustrates that a lack of design standards exists regarding the use of forepole elements. Therefore, when designing such support, designers must employ complex numerical models combined with engineering judgement. With reference to past developments by others and new investigations conducted by the authors on the Driskos tunnel in Greece and the Istanbul metro, this paper illustrates how advanced numerical modelling tools can facilitate understanding of the influences of design parameters associated with the use of forepole elements. In addition, this paper highlights the complexity of the ground-support interaction when simulated with two-dimensional (2D) finite element software using a homogenous reinforced region, and three-dimensional (3D) finite difference software using structural elements. This paper further illustrates sequential optimisation of two design parameters (spacing and overlap) using numerical modelling. With regard to capturing system behaviour in the region between forepoles for the purpose of dimensioning spacing, this paper employs three distinctive advanced numerical models: particle codes, continuous finite element models with joint set and Voronoi blocks. Finally, to capture the behaviour/failure ahead of the tunnel face (overlap parameter), 2D axisymmetric models are employed. Finally, conclusions of 2D and 3D numerical assessment on the Driskos tunnel are drawn. The data enriched case study is examined to determine an optimum design, based on the proposed optimisation of design parameters, of forepole elements related to the site-specific considerations.

SSPA experiences a growing interest in twin skeg ships as one attractive green ship solution. The twin skeg concept is well proven with obvious advantages for the design of ships with full hull forms, restricted draft or highly loaded propellers. SSPA has conducted extensive hull optimizations studies of LNG ships of different size based on an extensive hull data base with over 7,000 models tested, including over 400 twin skeg hull forms. Main hull dimensions and different hull concepts such as twin skeg and single screw were of main interest in the studies. In the present paper, one twin skeg and one single screw 170 K LNG ship were designed for optimally selected main dimension parameters. The twin skeg hull was further optimized and evaluated using SHIPFLOW FRIENDSHIP design package by performing parameter variation in order to modify the shape and positions of the skegs. The finally optimized models were then built and tested in order to confirm the lower power demand of twin skeg designed compaed with the signle screw design. This paper is a full description of one of the design developments of a LNG twin skeg hull, from early dimensional parameter study, through design optimization phase towards the confirmation by model tests.

The present paper studies effect of the variation of pit distance on structural reliability of a reinforced concrete (RC) beam, with particular emphasis on the interference of localized corrosion on adjacent tensile rebars. The research question leading the inquiry of this article is how does average distance between corrosion pits in rebars affect the probability of failure in RC beams. In this paper, by using Monte Carlo Simulation (MCS), probabilities of failure in a corroded RC beam with different pit distances are quantified. Uncertainties in material properties, geometry, loads, corrosion modelling, pit distances and pit interference are taken into account. Statistical data reported in literature regarding the extent and location of corrosion is utilized to undertake a parametric study of corresponding probability distribution functions. According to results, variation of pit distance has significant influence on probabilities of failure. This influence increases if the effect of interference of localized corrosion is taking into account.

Monitoring temperatures in structures during fires provides valuable information to 1) the firemen engaged in extinguishing it, 2) those who assess its security, and 3) the organizations who have to decide on its possible repair, renovation or demolition. Developing sensors able to measure extremely high temperatures in actual blaze conditions is therefore a fundamental requirement. This paper proposes a new fiber optic sensor based on Regenerated Fiber Bragg Gratings specially designed to be embedded in concrete structures to monitor temperatures during fire events. A practical test was carried out on a 5.8m long beam subjected to the ISO-834 fire curve for 77 minutes under the typical loads borne by beams in conventional structures. Nine optical sensors were installed at the mid-span section of the beam and were submitted directly to flames and high temperature gradients (of the order of 200ºC/min) that make them measure maximum temperatures of 953º C. The temperatures recorded by the new sensors were compared with those obtained from electrical sensors (thermocouples) and a numerical model, with which they showed a good fit, except in those places in which concrete spalling caused distortions in the results and/or failure of the sensors. The paper thus demonstrates the viability of optical technologies in monitoring reinforced concrete during fires and analyzes sensor behavior to point out areas in which additional research is required., This work was made possible by the support from the Universitat Politecnica de Valencia, the Spanish Ministry for Science and Innovation (Research Project BIA2011-27104 and TEC2011-29120-C05-05) and the Spanish Ministry of Public Works (Project Sopromac P41/08).

The full plastic resistance under a combination of bending and axial force of tubes of all possible wall thicknesses, from thin cylinders to circular solid sections, does not ever seem to have been thoroughly studied, despite the fact that this is a relatively simple analysis. The first part of this paper presents a formal analysis of the state of full plasticity under longitudinal stresses in a right circular tube of any thickness free of cross-section distortions. The derivation leads to relatively complicated algebraic expressions which are unsuitable for design guides and standards, so the chief purpose of this paper is to devise suitably accurate but simple empirical descriptions that give quite precise values for the state of full plasticity whilst avoiding the complexity of a formal exact analysis. The accuracy of each approximation is demonstrated. The two limiting cases of a thin tube (cylindrical shell) and circular solid section are shown to be simple special cases. The approximate expressions are particularly useful for the definition of the full plastic condition in tension members subject to small bending actions, but also applicable to all structural members and steel building structures standards, as well as to standards on thin shells where they provide the full plastic reference resistance. These expressions are also useful because they give simple definitions of the orientation of the plastic strain vector, which can assist in the development of analyses of the plastic collapse of arches and axially restrained members under bending.

An experimental investigation into the structural performance of compressed high strength steel (HSS) square and rectangular hollow sections is described in this paper. Both hot-rolled and cold-formed HSS sections were examined. In total six S460NH and five S690QH hot-rolled section sizes and three S500MC, two S700MC and four S960QC cold-formed section sizes were tested. The experimental programme comprised tensile coupon tests on flat and corner material, measurements of geometric imperfections, full cross-section tensile tests and stub column tests. The results of the experiments presented in this paper have been combined with other available test data on high strength steel sections, and used to assess the existing design guidelines for high strength steels given in Eurocode 3. The focus has been on the material ductility requirements, the Class 3 slenderness limit for internal elements in compression and the effective width formula for Class 4 internal elements in compression.Reliability assessments of the Class 3 slenderness limit (both the current value of 42 and a proposed value of 38) and the effective width formula for Class 4 internal elements in compression were carried out. The analysis indicated that, based on the assembled test data considered in this study, and the assumptions made regarding the statistical distributions of material and geometric properties, a partial safety factor greater than unity is required for HSS. Similar findings have also recently been presented for ordinary strength steels. This research has received funding from the Research Fund for Coal and Steel (RFCS) under grant agreement No. RFSR CT 2012-00028 and RFSR CT 2012-00036.

This paper introduces, for applications in the mining industry, an innovative hybrid column form which consists of an inner steel tube, an outer fibre-reinforced polymer (FRP) tube and an annular concrete infill between them. The two tubes may be concentrically placed to produce a section form more suitable for columns, or eccentrically placed to produce a section form more suitable for beams. The FRP is combined with steel and concrete in these hybrid structural members in such a way that the advantages of FRP are appropriately exploited while its disadvantages are minimized. As a result, these hybrid members possess excellent corrosion resistance as well as excellent ductility and seismic resistance. This paper summarizes existing research on this new form of structural members, and discusses their potential applications in mining infrastructure before presenting a summary of the recent and current studies at University of Wollongong (UOW) on their structural behaviour and design. Keywords: Hybrid column, Tubular column, Fibre reinforced polymer, Sustainable mining infrastructure

Many steel structures contain multiple fatigue sensitive details that have similar geometries and are subjected to similar load fluctuations. Examples are orthotropic (bridge) decks and stiffened (ship) hulls where tens to thousands of similar details are present in one structure. Generally only visual inspections on fatigue cracks are considered for these structures because more accurate techniques are considered to be too expensive and time consuming when so many details need to be inspected. Visual inspections are known to have a low probability of detection. Consequently Bayesian update techniques usually show a marginal effect of the result of visual inspections on the reliability of structures with respect to fatigue failure. On the other hand the inspection result of one location also provides information on similar details at other locations and thus the significance of the inspection result may be larger if multiple potential crack locations occur and cracks are not detected at any of these locations. This paper provides a probabilistic fatigue crack growth (fracture mechanics) model of a system containing a fatigue sensitive detail at multiple locations that accounts for the results of inspections. Spatial correlations of loading, resistance, and uncertainty variables between the different locations are evaluated and estimated through a literature review and are accounted for in the model. The model is demonstrated on a practical example of an orthotropic bridge deck containing a detail at 100 locations. The paper shows that visual inspections may be effective provided that a certain minimum inspection reliability can be guaranteed, that the structure is relatively tolerant to large cracks, and that the geometry and loading conditions are similar for a large number of locations.

Although stability charts suggested by Hoek and Bray on the basis of Mohr–Coulomb criterion are used for rock slopes, but complete and precise recognition is required for distinguishing cohesive strength and Mohr–Coulomb equivalent internal friction angle for rock mass. The paper by Lia et al. [6] is the only one that introduced rock slope charts according to Hoek–Brown failure criterion. In this paper, at first, this type of charts is introduced. Then, Mohr–Coulomb failure criterion charts [2] are compared and validated with Hoek–Brown failure criterion ones [6]. Next, Bishop method utilizing Slide software is compared with Hoek–Brown failure criterion stability charts. Average standard deviation (ASD), root mean square error (RMSE) and variance account for (VAF) were used for the comparison. According to the results, because of high distribution and very low correlation among the comparisons, Hoek–Brown failure criterion charts are not efficient. Keywords: Slope stability, Stability charts, Mohr–Coulomb failure criterion, Hoek–Brown failure criterion

Creep is one of the major problems of deep underground mining that must be studied theoretically, experimentally, and numerically over a long period. Experiments and field tests are methods which can directly and more accurately describe the engineering practices as compared with others. However, these approaches are also time-consuming because creep problem of rock engineering, such as the roadway/tunnel squeezing phenomenon, usually lasts from several months to a few years. A numerical method can be employed to overcome this time-consuming problem. The discontinuous deformation analysis (DDA) method was originated in 1984 and received considerable attention from geo-engineers and researchers. The current paper discusses the creep calculation methods using the continuous and the discontinuous methods, and proposes a creep analysis method based on DDA. The method proposed in this paper can directly change the stiffness matrix while inheriting the advantages of the original DDA. Applying this method does not require any changes in the contact part of DDA. Thus, this method does not have any effect on the open–close iteration and convergence and can solve the creep problem, while maintaining the advantages of the original DDA. We theorized that creep problems are static problems, and based on this, the work using DDA in this study was divided into two parts: (1) addition of a new loop for the original DDA to “discredited” the total creep time into several time elements, thereby changing the material properties in each time element; and (2) division of each of the time elements by the time steps, similar to the original DDA. In this manner, one creep problem can be solved via assembling of static problems. Afterwards, the method mentioned above is employed to modeling a tunnel case. The evolution of the displacement filed and stress field during creep are analyzed and discussed. Keywords: Creep, Deep underground mining, DDA, Tunnel squeezing

Aluminium alloys are nonlinear metallic materials with rounded stress–strain curves that are not well represented by the simplified elastic-perfectly plastic material model used in most existing design specifications. Departing from current practice, the continuous strength method (CSM) is a recently developed design approach for aluminium alloy structures, which gives consideration to strain hardening for non-slender sections. The CSM is a deformation-based method and employs a base curve to define the continuous relationship between cross-section slenderness and deformation capacity. This paper explains the background and the two key components of the CSM: (1) the base curve, which is extended herein such that the method covers both non-slender and slender sections and (2) the strain hardening material model. Three international design specifications from America, Australia/New Zealand and Europe, as well as the CSM are compared with approximately 900 aluminium alloy experimental and numerical results. Reliability analyses have been carried out to assess the reliability level of different design methods according to both the American Institute of Steel Construction (AISC) and European Standard (EN 1990) approaches. Finally, worked examples of the CSM for aluminium alloy stub columns and continuous beams are illustrated in this paper.

In this paper an experimental, numerical and analytical investigation is presented of the wrinkling behaviour that occurs in the flange of deep drawn cylindrical cups of aluminium alloy sheet using macro-textured blankholder surfaces. A series of deep drawing experiments were performed using a range of tool textures, draw ratios and blank-holding forces. A numerical material and process model was formulated to enable the occurrence of wrinkling to be simulated. In addition, two analytical buckling models of aluminium alloy sheet in deep drawing with macro-textured blankholder based on the energy method, (namely a one-dimensional and two-dimensional model) were developed for the first-time and utilised to predict the effect of process parameters on wrinkling. The analytical buckling models investigated two boundary conditions, hinged and built-in boundary condition. It was found that texture geometry and draw ratio had a significant effect on wrinkling but the blank-holding force did not. The analytical models developed in this paper to represent sheet metal wrinkling behaviour for the macro-textured tools can be used as a design guide to determine the geometry of tool textures necessary to avoid wrinkling defects in aluminium alloy stamping processes.

This paper presents a study of the effects of axial and rotational restraints on the fire response of concrete filled tubular (CFT) columns. The fiber model presented by the authors in a previous paper Ibañez et al. (2013) is employed to simulate the fire behavior of CFT columns within non-sway frames. Parametric studies are performed to analyze the influence of the different factors affecting the problem. Consequently, the opposite effects that the restraining frame has on the fire response of CFT columns are corroborated. On one hand, the restrained thermal elongation induces restraining forceswhich negatively affects the column. However, a beneficial effect is produced by the rotational restraintwhich positively modifies the boundary conditions of the heated column. Besides, another favorable effect comes from the gradual redistribution of the internal forces as the heated column loses its mechanical capacity, resulting in higher FRR. In a second step, current provisions given by Eurocode 4 Part 1.2 (EC4) are analyzed together with those given in the UK National Annex to Eurocode 4. Finally, these values are also used in the assessment of the simple calculation model presented by the authors in a previous paper Ibañez et al. (2015) and subsequently a proposal is made obtaining reasonably accurate but slightly safe results since the guidelines of CEN-Horizontal Group Fire were followed. As a result, the fire effective length value of 0.5 L given by EC4 is found to lead to unsafe results, being more appropriate to adopt the value of 0.7 L suggested in the UK National Annex., The authors would like to express their sincere gratitude to both the Spanish "Ministerio de Ciencia e Innovacion" and to the European Community through the FEDER funds for the help provided to finance the Project BIA2012-33144.

In this paper, a procedure for the kinematic design of a 3-PRS compliant parallel manipulator of 3 degrees of freedom is proposed. First, under the assumption of small displacements, the solid body kinematics of the 3-PRS has been studied, performing a comprehensive analysis of the inverse and forward kinematic problem, and calculating the rotations that the revolute and spherical flexure joints must perform. Then, after defining some design requirements and therefore the necessary displacements to fulfill, a design process based on the finite element calculations has been stablished, giving the necessary guidelines to reach the optimal solution on a 3-PRS compliant mechanism. Also, a prototype has been tested, using a coordinate measuring machine to verify its dimensions and the resulting displacements in the end effector and the actuated joints. Finally, those measurements have been compared with the FEM and the rigid body kinematics predictions, contrasting the validity of those two modelling approaches for the kinematic design of compliant mechanisms. The authors of this paper wish to acknowledge the financial support received from the Spanish Government via the Ministerio de Educación y Ciencia (Project DPI2011-22955) and Ministerio de Economía y Competitividad (Project DPI2015-64450-R), the ERDF of the European Union, the Government of the Basque Country (Project GIC07/78, IT445-10 and SAIOTEK 2013 SAI13/245, SPC13UN011), and the University of the Basque Country (Project EHUA13/30 and Zabalduz-2012). Thanks are also addressed to Dr. Jorge Presa and Alfonso Urzainki from Egile Corporation XXI for their valuable contributions.

This paper is concerned with the ultimate behaviour of composite floor slabs. Steel/concrete composite structures are increasingly common in the UK and worldwide, particularly for multi-storey construction. The popularity of this construction form is mainly due to the excellent efficiency offered in terms of structural behaviour, construction time and material usage all of which are particularly attractive given the ever-increasing demands for improved sustainability in construction. In this context, the engineering research community has focused considerable effort in recent years towards understanding the response of composite structures during extreme events, such as fires. In particular, the contribution made by the floor slab system is of crucial importance as its ability to undergo secondary load-carrying mechanisms (e.g. membrane action) once conventional strength limits have been reached may prevent overall collapse of the structure. Researchers have focused on developing the fundamental understanding of the complex behaviour of floor slabs and also improving the methods of analysis. Building on this work, the current paper describes the development and validation of a finite element model which can simulate the response of floor slab systems until failure, both at ambient and elevated temperature. The model can represent the complexities of the behaviour including the temperature-dependent material and geometric nonlinearities. It is first developed at ambient temperature and validated using a series of experiments on isolated slab elements. The most salient parameters are identified and studied. Thereafter, the model is extended to include the effects of elevated temperature so it can be employed to investigate the behaviour under these conditions. Comparisons with current design procedures are assessed and discussed.

[EN] This paper examines the effect of concrete compressive strength on the transfer length of prestressing strands. The paper includes the results from several research projects conducted at the University of Arkansas (UA) and from testing reported in the literature. At the UA, 57 prestressed, precast beams have been cast since 2005. The beams were cast with selfconsolidating concrete (SCC), high strength concrete (HSC), lightweight self-consolidating concrete (LWSCC), and ultra-high performance concrete (UHPC). Using data from the UA and from the literature, an equation to estimate transfer length was developed and presented. The results were also compared with the American Concrete Institute (ACI 318) and the American Association of State Highway and Transportation Officials (AASHTO) prediction equations for transfer length, which were designed for conventional concrete. The results also showed that there was little change in transfer length when the compressive strength at release was greater than 34.5 MPa. (C) 2015 The Institution of Structural Engineers. Published by Elsevier Ltd. All rights reserved.

This paper reports the second part of the study on the structural behaviour of stainless steel circular hollow sections subjected to combined axial load and bending moment. A series of numerical parametric studies is presented, using the validated finite element (FE) models from the companion paper, with the aim of generating further structural performance data over a wider range of stainless steel grades, cross-section slendernesses and combinations of loading. The considered parameters include the outer cross-section diameter, the ratio of outer cross-section diameter to thickness and the initial loading eccentricity. Both the experimentally and numerically derived section capacities were compared with the strength predictions determined from the current European code, the American specification and the Australian/New Zealand standard, allowing the applicability of each codified method to be assessed. The comparisons revealed that the current design standards generally result in unduly conservative and scattered strength predictions for stainless steel circular hollow sections under combined loading, which can be primarily attributed to the neglect of strain hardening in the determination of cross-section resistances and to the use of linear interaction formulae. To overcome these shortcomings, improved design rules are proposed through extension of the deformation-based continuous strength method (CSM) to the case of circular hollow sections subjected to combined loading. Comparisons between the proposals and the test and FE results indicate a high level of accuracy and consistency in the predictions. The reliability of the proposed approach was confirmed by means of statistical analyses according to EN 1990.

Dynamic Soil-Structure Interaction (DSSI) is an area of much ongoing research and has wide and varied applications from seismic response analysis to offshore wind foundation response. DSSI covers a wide range of load regimes from small-strain vibrations to large-strain cyclic loading. One of the most common ways to model DSSI uses the Winkler model, which considers the soil as a series of mutually independent springs. The difficulty with modelling DSSI arises with the inelastic and nonlinear load–displacement response of soil with increasing strain, therefore modelling of large-strain DSSI relies on the specification of many interrelated parameters. The relative magnitude of these parameters can have a significant effect on the modelled response. In this paper, the specification of an initial stiffness coefficient to model the elastic (small-strain) response of a soil–pile system is investigated. The coefficient of subgrade reaction method can be used to generate spring stiffness moduli for Winkler type models. A number of subgrade reaction theories have been proposed and their application to the problem of static loading has been widely studied. However, relatively little research concerning the application of these models for small-strain dynamic loading has been undertaken. This paper describes a sensitivity study in which a number of subgrade reaction models were used to estimate the frequency response at small-strain levels for a range of pile geometries and ground conditions. A field investigation was undertaken on two piles with different slenderness ratios to estimate the frequency response and damping ratios. The experimental results were compared to predictions of damped natural frequency obtained from numerical models using the force input and measured damping ratio from each experiment. The ability of each subgrade reaction formulation to model the response at small-strain levels is evaluated. European Commission - European Regional Development Fund European Commission - Seventh Framework Programme (FP7) Higher Education Authority Earth and Natural Sciences (ENS) Doctoral Studies Programme EU FP7 SMART RAIL