Out-of-plane Bending Research Articles

Research on Wear Damage of Anchor Chain under Different Load Modes

In the marine environment, mooring anchor chains bear complex loads such as axial tension and out of plane bending. These loads cause wear and corrosion damage to the anchor chain, reducing its fatigue strength, and even leading to fatigue fracture. The inspection load applied to the anchor chain before leaving the factory will generate residual stress, which will affect the stress characteristics and fatigue life of the anchor chain during service. This article aims to obtain the residual stress generated by the test load on the anchor chain through numerical simulation, and explore the impact of the test load residual stress on the stress characteristics and wear performance of the anchor chain; Analyze the stress and contact characteristics of anchor chains under different bending angles and wear depths, and obtain the locations where fatigue damage is prone to occur in the later stage of anchor chain wear.

An Out-of-Plane Bending Fatigue Assessment Approach for Offshore Mooring Chains Considering the Real-Time Updating of Interlink Bending Stiffness

Fatigue failure caused by frequent tension and bending loads is a crucial safety concern for mooring chains used on floating structures in the oil and gas industry. The bending effect for a chain’s fatigue is usually not considered by existing fatigue analysis methods, and even if it is considered, existing commercial software can only calculate the constant interlink bending stiffness without consideration of the stiffness variations due to tension and friction. To address this issue, this study develops an in-plane bending (IPB)/out-of-plane bending (OPB) fatigue assessment approach for offshore mooring chains considering the time-varying nonlinear interlink bending stiffness. Initially, the mooring tension and IPB/OPB angles are calculated by an in-house code MeCAP (multi-element coupled analysis program), considering the time-varying interlink stiffness between the chain links. The fatigue life of mooring chains for pure tension–tension (TT) and OPB combined fatigue at different hotspot locations (A, B, and C) is calculated by MeCAP-fatigue, a newly-developed module in MeCAP. Based on the analysis model, a comparative study is implemented to investigate the effects of interlink stiffness on fatigue damage. The differences and advantages of the combined fatigue calculation method over the pure TT fatigue assessment method are discussed. The results illustrate that combined fatigue would be underestimated significantly if zero interlink stiffness (hinge joint assumption) is applied or even constant interlink stiffness (calculated by mooring pretension), while pure TT fatigue will be largely unaffected. Moreover, compared to pure TT fatigue, the OPB combined fatigue assessment method, considering the effects of OPB/IPB and the time-varying properties of the connection between chain links, could evaluate fatigue life more comprehensively.

Bending load effects on stress concentration factor distribution of multi-planar DTKY tubular joints

The stress concentration factor (SCF) in tubular joints is an important parameter in calculating the fatigue life of offshore structures. In design practices, estimating the SCF is usually based on standard empirical formulas, providing the majority for uni-planar tubular joints, and could not be applied directly for multi-planar joint cases. Therefore, accurate SCF estimation became critical for specific multi-planar tubular joints commonly found as members of offshore platforms. More detailed analyses of complex designs are possible with the recent development of finite element analysis and supported by advanced digital computers. Thus, this research is intended to analyze the SCF of multi-planar DTKY tubular joints with finite element analysis. The local model of the tubular joint will be simulated for bending moment load cases. The results show stress distribution characteristic of the joint at both brace and chord sides. The results indicated that the SCF of the joint under the in-plane bending (IPB) loading is higher at the brace than the chord side, with values of 2.83 and 1.47, respectively. Meanwhile, under the out-of-plane bending (OPB) loading, the SCF is 2.43 at the chord saddle location and 3.54 at the brace saddle location.

Fatigue life estimate of metallic chain links of mooring systems assuming out of plane bending: From constant amplitude to random loading

In this work, a numerical and analytical study of the fatigue life of chains in the mooring system of FPSO platforms is carried out. Initially, analytical equations are proposed to calculate the stress at the hotspot of the critical chain link, considering axial stresses generated by axial loads and out-of-plane bending (OPB). The analytical equations consider the operating angle of the mooring systems as well as the interlink angle of the links. Thus, the validation of the equations is done by comparing the stress values obtained through numerical simulations of the mooring-fairlead system, where a satisfactory correlation was observed. In addition, loads with constant and variable amplitude are generated as well as random load histories, always between the maximum and minimum operating load of the system, which represent 1/3 and 1/6 of the minimum breaking load (MBL) of the chain link. Based on the Smith-Watson-Topper (SWT) approach, the fatigue life of the chain was estimated, considering the analytical value of the stress at the hotspot based only on the axial contribution and later, due to the axial and OPB contributions. Finally, it was verified that the analytical equations were able to determine the stress values at the hotspot and that the effect of normal stress at the hotspot due to OPB can cause a severe loss in the fatigue life of the mechanical component.

Relationships between stiffness of material, lamellas and CLT elements with respect to out of plane bending and rolling shear

The use of cross laminated timber (CLT) for construction has increased greatly in recent years and the large volumes of wood used for CLT means that it is important to optimize the use of the material. This requires relevant grading of lamellas and knowledge of relationships between lamella and CLT properties. In the present study, the relationship between dynamic axial modulus of elasticity (MoE) of lamellas and the quasi-static out of plane bending stiffness of CLT is investigated. By means of four-point bending test, it is shown that the effective quasi-static MoE of lamellas in CLT is only 2–6% lower than the average axial dynamic MoE of the individual lamellas. With this knowledge, producers of CLT can easily predict and control the important out of plane bending stiffness of the produced CLT. Moreover, it is shown that effective rolling shear stiffness of layers in CLT can be accurately determined by means of digital image correlation performed in connection to four-point bending of CLT, even for long test spans. For layers of lamellas of Scots pine of size 40 × 190 mm2 the average apparent or effective rolling shear modulus was determined to be 159 MPa. The average rolling shear modulus of the same material was determined to be 56 MPa.

Geometrical effects on the local joint flexibility of three-planar tubular Y-joints in substructures of offshore wind turbines

ABSTRACT Although three-planar tubular Y-joints are amongst the most common joint types in jacket- and tripod-type substructures of offshore wind turbines (OWTs), local joint flexibility (LJF) of this type of connection has not been studied so far, mainly due to the complexity of the problem and high cost involved. Results of a parametric study conducted on the LJF of three-planar tubular Y-joints are presented and discussed in this paper. A set of finite element (FE) analyses were carried out on 81 FE models subjected to six types of axial, in-plane bending (IPB) moment, and out-of-plane bending (OPB) moment loadings in order to study the effects of geometrical characteristics of the three-planar Y-joint on the LJF factor (f LJF). FE results were then used to develop a new parametric equation for the prediction of the f LJF in axially loaded three-planar Y-joints, and the derived equation was checked against the UK DoE acceptance criteria.

Experimental investigation of cold formed high strength steel tubular joints subjected to moment loading

In recent years, simple design methods for high strength steel tubular joints have been proposed by several design standards. According to these standards, the design resistance of high strength steel joints is obtained from the same design equations used for mild steel joints, but the resistance should be reduced properly by applying the material factor and/or the design yield stress. The material factor is a direct reduction factor to design resistance which generally corresponds to 0.9 for 460-grade and 0.8 for 700-grade steels, while the design yield stress (or fu/ fy limit) is a measure to account for the low fu/ fy ratios of high strength steels. In this study, a recent experimental program on moment-loaded high strength steel tubular joints is reported, which covered both circular (CHS) and rectangular (RHS) hollow section joints and both in-plane bending (IPB) and out-of-plane bending (OPB) moments. Based on the test results and additional test data collected from available database, the design equations, material factor, and design yield stress recommended by the revised draft of EN 1993-1-8 (prEN 1993-1-8) are evaluated for moment-loaded tubular joints made of grade 700 steels. It is shown that the prEN 1993-1-8 equations, combined with the material factor and design yield stress, generally provide conservative moment resistances for 700-grade tubular X and T-joints. However, based on the experimental implication that nonuniform stress distribution may cause an early fracture in CHS joints, it is suggested that the effective width, which is usually considered only for RHS joints, be considered also for CHS joints subjected to OPB.

Effects of chord compression on OPB fire performance of CHS T-joints: An experimental study

Almost all previous experimental studies on the fire performance of steel circular hollow section (CHS) joints were conducted in the absence of external load in the chord [9-15, 17-19, 21-22, 24, 26-28]. This paper is focused on the chord compression effects on the fire performance of CHS T-joints under out-of-plane bending (OPB). Seven identical small-scale tubular specimens were tested under different combinations of axial compression in the chord, OPB in the brace, and the standard fire. It was found that the chord compression effect on the OPB of CHS T-joints significantly escalates under fire conditions, compared to that at ambient temperature. Dominant failure modes in the specimens tested were local buckling of the chord face around brace/chord intersection, crippling/bulging of the chord sidewalls, and flexural yielding of the brace.

Behaviour of plain and fibre reinforced cement stabilised rammed earth under compression, tension and shear

Cement stabilised rammed earth (CSRE) is used for load-bearing walls in buildings and other structures. There is an upsurge in interest for using CSRE constructions worldwide in the last six to seven decades. The CSRE wall elements in a structure undergo sudden catastrophic shear failures under the compression and shear loadings and exhibit brittle flexure failures under out of plane bending. The brittle failures should be avoided in the structural wall elements. The limited studies on the fibre reinforced CSRE reveal that the addition of fibres can enhance the material's mechanical properties and help prevent sudden catastrophic failures. However, the studies on the fibre reinforced CSRE are still in nascent stage. The behaviour of fibre reinforced CSRE under different loading conditions remains an unexplored area. The present study attempted to understand the behaviour of fibre reinforced CSRE under compression, tension, and shear. The investigations revealed that the addition of short coir fibres significantly increases the failure strains and the energy absorption capacity of CSRE under compression and in-plane shear, eliminating the sudden catastrophic shear failures observed in the plain CSRE. The coir fibre inclusion, although partially increases the compression and the shear strength of CSRE, it significantly enhances the splitting tensile strength and post peak response.

Seismic response of the long-span steel truss arch bridge with the thrust under multidimensional excitation

PurposeUnder different ground motion excitation modes, the spatial coupling effect of seismic response for the arch bridge with thrust, seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approachTaking a 490 m deck type railway steel truss arch bridge as the background, the dynamic calculation model of the whole bridge was established by SAP2000 software. The seismic response analyses under one-, two- and three-dimension (1D, 2D and 3D) uniform ground motion excitations were carried out.FindingsFor the steel truss arch bridge composed of multiple arch ribs, any single direction ground motion excitation will cause large axial force in the chord of arch rib. The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation. The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation. For the bottom chord of arch rib, the arch foot is the weak part of earthquake resistance, but for the upper chord of arch rib, the arch foot, arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts. The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force, but the normal stress of the upper chord of the arch rib is caused by the axial force, in-plane and out of plane bending moment.Originality/valueThe research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.

Degree of bending (DoB) in jack-up unit tubular KK-joints under the axial, in-plane bending (IPB), and out-of-plane bending (OPB) loads

ABSTRACT The determination of degree of bending (DoB) is critical to improve the accuracy of estimating fatigue life using stress life (S-N) method. Based on the truss structure of jack-up unit, the numerical model of tubular KK-joints including rack plate (thickness is 180mm) is established. In the present research, the data extracted from 378 FE analyses on 108 tubular KK-joints models were used to study the effect of geometric parameters on DoB values of KK-joints under six different types of axial loading, IPB and OPB loadings. The geometric parameters affecting the DoB of tubular KK-joints are analyzed by multiple nonlinear regression analysis, and 21 parameter design formulas are obtained to calculate the DoB values of tubular KK-joints under axial loadings, IPB and OPB loadings. The established geometric parameter equation can effectively evaluate the fatigue characteristics of truss legs with rack plate of jackup unit.

Neutron-γ discrimination with organic scintillator crystal: 9-Phenylcarbazole (9-PCz) grown by Bridgman – Stockbarger method

Organic scintillator crystal 9-Phenylcarbazole (9-PCz) has been grown using Bridgman -Stockbarger technique. The crystal structure, lattice parameter and bond angle values are measured from single-crystal X-ray diffraction (SXRD) analysis. C–H inplane bending and out of plane bending and skeletal vibrations of 9-PCz molecule were identified from vibrational spectral analysis. UV–visible NIR spectral study shows that the crystal exhibits around 50% of transmittance in the infrared region and the direct optical bandgap energy is calculated to be 3.36 eV. Thermal properties of grown 9-PCz material were measured using thermogravimetric and differential thermal analyses (TG-DTA). The photoluminescence (PL) measurements show two emission bands with a maximum peak at 365 nm and a shoulder peak at 381 nm. X-ray induced luminescence spectrum of 9-PCz crystal exhibits a maximum emission peak at 381 nm. Scintillation decay time measurement shows the major component of 18 ns decay time. The pulse shape discrimination (PSD) capability of the grown crystal sample was studied for the signals induced by α-particles and γ-rays from 241Am and 137Cs sources, respectively. The figure of merit (FOM) is found to be 2.69. The preliminary results showed that the present studied organic crystal (9-PCz) scintillator can be considered in the field of fast neutron detection application.

Influence of interlayer shear studs on the behaviour of cement stabilised rammed earth under compression, tension and shear

Cement stabilised rammed earth (CSRE) has been used for the construction buildings since the last 6–7 decades across the world (Australia, Europe, Asia, Africa, and countries such as New Zealand and the United States). The rammed earth is a monolithic construction, where the processed earth is compacted in layers. The interfacial bond strength between the compacted layers is weak, and hence there is a weak link among the compacted layers of CSRE. The major issues with CSRE walls are (1) catastrophic shear failures under compression and shear and (2) poor flexure and shear strength. Introducing short shear studs at the interfaces of the compacted rammed earth layers is one possibility to enhance the shear and the flexure strength of the CSRE. The paper focuses on evaluating the compressive strength, interface shear strength, shear stress-shear strain relationships, and the flexural strength of steel studs embedded CSRE for the first time. The results reveal that due to the introduction of shear studs, (a) the interfacial shear strength and diagonal shear strength of CSRE improved significantly, (b) The ultimate moment-resisting capacity doubles and (c) the steel studs embedded CSRE wallette showed ductile failure. The results clearly demonstrated that introducing steel studs among the compacted layers of CSRE could help avoid sudden catastrophic failures of CSRE walls under out of plane bending.

Calcium carbonate nanoparticles of quail’s egg shells: Synthesis and characterizations

Abstract Avian eggshell is a natural biomaterial that has been used as an alternative natural source of CaCO3 and is accessible in big amounts from egg manufacturing. This study was planned to estimate CaCO3 in quail’s eggshell because it has a probable use in the progress of a novel choice of many applications. Physical properties: mineralogical documentation of the natural eggshell nanoparticles were approved using XRD and FTIR to explore the chemical bond or molecular structure of the materials. Micrographs were obtained using FESEM/EDX and TEM to identify the morphology and size of nanoparticles. The results showed that quail eggshell was soft, with white to light sand color, and a smooth texture which allows good deposition of different color spots, from black to brown spots. The resulted of eggshells signifies almost 8.4% w/w of the overall weight (12.2) gram of quail egg and 91.60% w/w of the micropowder to the full weight of (0.94) gram of quail eggshell. The results presented that calcium is the main element in an eggshell; frequently occurs in a formula of CaCO3 and the crystal construction was almost pure calcite. FTIR spectra for quail eggshell demonstrated the existence of the out of plane bending, the asymmetric stretching, and the plane bending styles of the carbonate groups, specific of normal dolomite, situated at 873 cm–1, 1405 cm–1, and 710 cm–1, respectively. The FESEM and TEM for nanoparticles were shown calcite CaCO3 nanoparticles with an ordinary size of ≤ 100 nm for FESEM and with a variety size of ≤ 50 nm for TEM. Unfortunately, eggshell is an egg product manufacturing deposit. These incomes will let fast developments in proportional studies of the organic elements of avian eggshell and their purposeful consequences by usages of eggshell in nourishment and medicine which can be applied for many resolutions that diminish their consequence on environmental contamination.

Out-of-plane bending fire response of steel tubular T-joints: A sequentially coupled thermal-stress modelling

The current paper deals with numerical simulation of out-of-plane bending (OPB) of steel tubular T-joints in a standard fire. The data from fire tests, already carried out by the authors on OPB of small-scale steel tubular T-joints, are used to validate the numerical model. An extensive parametric study is conducted on the fire response of full-scale steel tubular T-joints. The results show the chord diameter to thickness ratio (γ), brace/chord diameters ′ ratio (β), load ratio (η), steel grade, and the chord axial fixity (KC−ax) as the most influential parameters affecting the OPB fire response of the steel tubular T-joints.

Fracture mechanics assessment for mooring chain links tensioned over a curved surface

A fracture mechanics (FM) based investigation on the effects of curved surfaces on fatigue lives of mooring chain links tensioned over curved surfaces is conducted in this paper. Three typical curved surfaces including ungrooved surface, shallow grooved surface, and deep grooved surface are investigated. The mooring chain links tensioned over an ungrooved surface are considered under the combined action of in-plane bending (IPB), out-of-plane bending (OPB), torque, and tension. The chain links supported by the bottom of a shallow groove surface are assumed to be influenced by extra IPB. The chain links laying on the upper surface of a deep grooved surface are considered to be subjected to OPB. The results show that fatigue lives of mooring chain links tensioned over the three curved surfaces are significantly shorter than those of mooring chain links subjected to pure tension. Fatigue lives of mooring chain links tensioned over the three curved surfaces would decrease with the decrease of the diameter of the curved surface. For mooring chain links tensioned over an ungrooved surface, the fatigue lives of mooring chain links would decrease with the increase of the angle between the transverse axis of mooring chain link and the surface.

Experimental study of fire effects on out-of-plane bending strength/flexibility of steel tubular T-joints

Steel tubular structures are popular in ocean and offshore structures, buildings, bridges, space frames, mining equipment, recreation structures and transportation vehicles. A tubular joint has a critical role in maintaining the integrity of a steel tubular structure under operational and extreme loading conditions. This paper reports the first experimental investigation on the out-of-plane bending (OPB) strength and stiffness of steel tubular T-joints under fire conditions. The tubular specimens were tested to failure under OPB at ambient temperature and under ISO-834 standard fire. The moment rotation response, critical temperature, fire endurance time, structural strength and flexibility of the T-joint specimens were explored. The failure mode of the specimens was noticed to change from “development of a plastic hinge in the brace” at ambient temperature to “the chord face plastification” under fire conditions. Temperature adjustments were made to available parametric equations, basically proposed for the OPB capacity and stiffness of steel tubular joints at ambient temperature. The temperature-modified OPB capacity equations somewhat under-predicted the test results for OPB strength under fire conditions. The temperature-modified OPB stiffness equations showed satisfactory correlation with the test results under fire conditions.

Stress concentration factors in steel tubular KT-connections with FRP-Wrapping under bending moments

Stress concentration factors (SCF) in steel tubular joints have gained considerable attention since it is the crucial parameter for fatigue design of steel tubular structures. Meanwhile, among various strengthening methods, Fiber Reinforced Polymer (FRP) wrapping has shown to be an effective scheme for reinforcing steel structures. This study is dedicated to the numerical investigation of SCF values in FRP-strengthened tubular KT-joints under the action of In-Plane Bending (IPB) and Out-of-Plane Bending (OPB) moments on the central as well as outer braces with three various practical loading patterns per each moment. The Finite Element (FE) modeling methodology for joint geometry and FRP generation was validated against the available data in the literature and well-known codes. The effects of different geometrical parameters along with the FRP parameters on the SCF values were studied through post-analyzing a total of 2920 FE models. The numerical parametric studies indicated that FRP strengthening could lower the SCF values in KT-connections by about 30 and 55 percent under IPB and OPB moments, respectively. Using the driven data, practical fatigue design formulas were developed for predicting SCF in FRP-strengthened KT-joints under bending moments, and reliability of the proposed equations was examined using Fatigue Guidance Review Panel recommendations.

Probability density functions of the DoB in tubular KT-joints of jacket-type platforms under out-of-plane bending loads

The degree of bending (DoB) has a profound effect on the fatigue behavior of tubular joints commonly found in offshore jacket structures. Probability density functions (PDFs) of the involved random variables are necessary for the fatigue reliability analysis of jacket structures. The objective of present research was the derivation of PDF for the DoB in tubular KT-joints commonly found in jacket-type platforms. A total of 243 finite element (FE) analyses were carried out on 81 FE models of KT-joints subjected to three types of out-of-plane bending (OPB) moment loading. Generated FE models were validated using experimental data, previous FE results, and available parametric equations. Based on the results of parametric FE study, a sample database was prepared for the DoB values. Thirteen theoretical PDFs were fitted to the developed histograms and the maximum likelihood (ML) method was applied to evaluate the parameters of fitted PDFs. In each case, the Kolmogorov-Smirnov test was used to evaluate the goodness of fit. After substituting the values of estimated parameters, six fully defined PDFs were presented for the DoB at the saddle positions of the central and outer braces in tubular KT-joints subjected to three types of OPB moment loading.

Bending analysis of laminated beams using isogeometric variational asymptotic method

Variational asymptotic method (VAM) is a robust mathematical method employed to arrive at a reduced order governing equations in solid mechanics. VAM for beam analysis is accomplished in two stages: first stage involves performing a two-dimensional cross-sectional analysis, and the last stage is one-dimensional beam analysis. Cross-sectional analysis stage involves determining the stiffness coefficients for the beam cross section. VAM can be implemented either by developing analytical solutions or by adopting numerical methods. For beams with arbitrary cross-sectional shapes and material heterogeneity, cross-sectional analysis in VAM is generally carried out by adopting a finite element type procedure. In this study, a numerical procedure for the two-dimensional analysis and the one-dimensional beam analysis based on isogeometric framework is presented. NURBS functions are employed to model the geometry of a cross section and the warping displacement field. Warping represents the deformation of cross section of the beam. Stiffness coefficients obtained by cross-sectional analysis are input to the one-dimensional analysis. A NURBS-based one-dimensional method for bending analysis of laminated composite beams is proposed which can handle axial forces, twisting moments, in-plane and out-of plane bending moments. The one-dimensional analysis features four unknown variables, namely axial displacement, twist and two transverse displacements. The one-dimensional beam geometry and the unknown variables are modelled using NURBS functions. The one-dimensional formulation requires $$C^1$$ continuity which can be easily satisfied by NURBS functions. Numerical examples are solved to ascertain accuracy of the proposed methods. Results obtained were compared with exact solution and was found to be accurate. The one-dimensional analysis based on NURBS functions is non-intrinsic. Application of boundary conditions is far simpler to implement in comparison with the intrinsic one-dimensional analysis methods existing in traditional one-dimensional analysis of VAM literature.