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• The dynamic response of thin-walled cylindrical shells subjected to lateral shock loading via foam projectile impact was systematically studied. • Structural deformation evolution, deformation/failure modes, and mid-point deflections of thin-walled cylindrical shells under lateral shock loading were experimentally measured. • The sensitivity of the dynamic response of thin-walled cylindrical shells to the impact momentum level and geometric parameters under lateral shock loading was numerically explored. • It is found that the deformation on the rear side exhibits two patterns: indentation and bulge, which are dictated by the combined effect of circumferential membrane forces and bending moments. A combined experimental and numerical study was carried out to explore the dynamic response of Q235 thin-walled cylindrical shells under lateral shock loading. The machined Q235 specimens were clamped on both sides and subjected to centered lateral simulated shock loading via foam projectile impact tests, with their dynamic deformation evolution, mid-point deflections, and final deformation modes experimentally measured. The mid-point deflections of the impact side are all positive (the direction of deformation is the same as the impact direction) while those of the rear side all exhibit negative values (the direction of deformation is opposite to the impact direction). To further explore this phenomenon, the method of finite element (FE) was employed to simulate the foam projectile impact, with good agreement against experimental measurements achieved. Using the validated numerical model, the effects of impact velocity, length-to-diameter ratio, and thickness-to-diameter ratio on the dynamic response of the thin-walled cylindrical shell were further analyzed. The direction of both side deflections and deformation modes are significantly affected by the impact level and the shell geometries. For the rear side, within the given range of impact momentum and geometric parameters, the numerically predicted deflection varies from −1.775 mm to 2.45 mm. Thereupon, the coupling of indentation and bulge deformation patterns are indicated, and their corresponding contribution changes are considered the main mechanism for determining the final deformation of the thin-walled cylindrical shell's rear side. [ABSTRACT FROM AUTHOR]

• Experimental research on the out-of-plane ultimate bearing capacity of high strength steel (HSS) arches with thin-walled I-section. • Examined the out-of-plane ultimate bearing capacity of 14 HSS arch specimens, considering variations in yield strength, cross-sectional dimensions, slenderness, rise-span ratios, and span. • The finite element analysis of HSS arch, accounting for residual stress and initial defects, demonstrated a high degree of alignment with experimental results. • Investigated the effects of yield strength, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. • Established axial force-bending moment (N-M) design formulas for the out-of-plane ultimate bearing capacity of HSS arches. This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches. [ABSTRACT FROM AUTHOR]

• Perform three-point bending tests on high strength grouted tube-sleeve connection. • Investigate load transfer mechanism of grouted tube-sleeve connection. • Perform FE simulation of grouted tube-sleeve connection under lateral load. • Perform moment-shear interaction analysis of grouted tube-sleeve connection. Prefabricated prefinished volumetric construction divides traditional buildings into room-sized modules that are manufactured off-site and assembled on-site. This construction method offers improved construction speed, superior quality control, and reduced environmental impact compared to traditional construction. In high-rise modular construction, the connections between modules may experience significant bending moments due to wind loads or earthquakes. Therefore, the flexural performance of these connections becomes a critical factor that affects the overall stability and robustness of the modular structures. The present study combines the advantages of high strength grout and square hollow section tube sleeves to develop a robust grouted connection for prefabricated structures without compromising assembly efficiency. Firstly, the study conducts three-point bending tests on eight full-scale specimens to investigate the flexural behavior of the connection. The load transfer mechanism, failure modes, moment-curvature relationship, and strain development of the tube-sleeve connection under lateral load are analyzed in detail. The study also quantifies and discusses the effects of different shear key spacing, grout length, inner tube width, and steel fiber content on the strength and stiffness of the connection. In addition, the study utilizes ABAQUS to simulate the bending responses of the connection, including inner tube fracture, grout crack development, and internal complex strain state. The finite element analysis results demonstrate good agreement with the experimental results, with an average ratio of 1.04 between numerical results and test results for flexural resistance, and a standard deviation of 0.04. Furthermore, based on elasto-plastic mechanics and the actual cross-sectional stress distribution of the connection, three analytical models are proposed to predict the flexural resistance of the connection. Finally, the moment-shear interaction relation is verified against the finite element and test results using the elastic-plastic analytical model and the ultimate state shear model. [ABSTRACT FROM AUTHOR]

• SHG deflection and local deflection correlate with cumulative underwater explosion damage. • SHGs deform at 10 impact factors; increased explosive mass causes plastic bending deformation. • SHG's residual strength decreases with explosions, primarily due to altered load distribution. The dynamic response and cumulative damage mechanism of simplified hull girders (SHGs) subjected to repeated underwater explosions were investigated in this research. Experimental and numerical investigations were conducted to gain a comprehensive understanding of the relationship between cumulative damage and explosive charge. Three series of experiments were carried out on SHGs, subjecting them to both single and repeated loading (up to five times). The analysis focused on the overall deflection values of the SHG and the local bottom plate deflection values, revealing a linear relationship with the cumulative number of occurrences. A validated finite element simulation model was employed to examine the response of the SHGs under repeated blast loading, utilizing experimental results for validation. An impact factor was established to quantify the magnitude of the explosive force, considering both the power of the explosive and the distance of detonation. The SHGs showed localized deformation at 10 impact factors, but experience pronounced cumulative effects at 14.4 and 20 impact factors. Furthermore, a consistent decline in the residual strength of the SHGs as the number of explosions increased. Following the first underwater explosion, the damaged SHG displayed an ultimate plastic bending moment of 3696.5 N m, reflecting a 16.3 % reduction compared to the unloaded SHGs. This reduction can primarily be attributed to the altered load distribution on the deformed SHGs. These findings contributed to the understanding of the cumulative damage behavior and response of SHGs exposed to repeated underwater explosions, providing valuable insights for the design and structural integrity assessment of naval vessels. [ABSTRACT FROM AUTHOR]

• Proper quantification of joint rotational stiffness (JRS) of a flight intersection joint (FIJ) influences the dynamic characteristics of a flight vehicle. • JRS of an FIJ is often determined experimentally due to the lack of a right predictive model. • An analytical model is proposed to evaluate the JRS of a radial-type FIJ when subjected to an external bending moment. • Numerical analyses and experiments are performed on six different FIJ configurations. • JRS and moment-rotation behavior predicted by the proposed model are correlated with both experimental and numerical analyses. • Further, the effect of joint clearances on the behavior of FIJ is investigated through the present model. Joint rotational stiffness (JRS) of a flight intersection joint (FIJ) and its accurate quantification play an essential role in studying the dynamic modal characteristics of a flight vehicle. This JRS of a FIJ is mostly determined through elaborate experiments due to the non-availability of a reliable predictive model. Therefore, in this paper, an analytical model is proposed to evaluate JRS of a radial type FIJ when subjected to external bending moment. In this model, at first, the tensile and compressive part of the FIJ section is identified by determining the neutral axis position. The respective part's contributing stiffness is then estimated by employing a spring-mass model. Later, the JRS expression is derived from the moment equilibrium condition and expressed as a function of the stiffness of the tensile and compressive part and neutral axis position. Subsequently, finite element analysis (FEA) is conducted with different numbers of screws, followed by detailed experimental investigations. The proposed analytical model is validated with the results from FEA and experiments for different screw configurations of FIJ. Further, the proposed model is extended to account for the effect of joint clearances on the JRS and the corresponding moment-rotation characteristics of the FIJ. [Display omitted] [ABSTRACT FROM AUTHOR]

Locally slender cross-section members, such as cold-formed steel open sections, are susceptible to significant twisting and high warping torsion stresses. Torsion considerations are complicated by whether it is derived as a first-order effect from loading or a second-order effect from instability. Previous direct torsion experiments on lipped Cee sections have shown significant inelastic reserve. Furthermore, the current design for combined bending–torsion interaction has limitations, including only considering the first yield and ignoring the cross-section slenderness in torsion. Two parametric studies were conducted to predict both the torsion capacity and the combined bending–torsion interaction in locally slender cross-sections. Shell finite element analysis of lipped Cee and Zee sections for both the torsion only and the combined bending–torsion cases were created using a validated model. For the torsion-only study, various cross-section geometries, steel grades, and member lengths covering the range of practically expected torsional slenderness were investigated. A set of bimoment parameters, including yield, buckling, and plastic bimoments, were calculated and the ultimate bimoment was determined by shell finite element collapse analyses. A simple uniform equation predicting the bimoment capacity was adopted and two bimoment strength curves are proposed for local and distortional buckling-controlled cases respectively. For the combined bending–torsion case, various practical cross-sections and bracing conditions were investigated with various ratios of applied torsion and bending. Shell finite element buckling and collapse analyses were performed to determine the critical and ultimate moments and bimoments. It was found that the current AISI standard is conservative under most scenarios. Updated torsion–bending interaction equations incorporating bimoment and bending moments are proposed. The interaction equations are dependent on the cross-section, the direction of the applied torsion, and the bracing condition. • Current design for CFS open sections under combined bending–torsion has limitations. • Design strength for CFS open sections under torsion is proposed. • Combined bending–torsion interaction for CFS open sections is developed. • Developed design equations for both torsion scenarios are calibrated. [ABSTRACT FROM AUTHOR]

• A 3D free-bending process method that can accurately control the process parameters in transition zone is proposed. • An analytical model of finned special-shaped tube bending forming based on exponential hardening behavior is constructed. • The influence rule of the speed parameters in transition section on the forming radius and cross-section deformation is obtained. • FE results are in good agreement with experimental results. In 3D free-bending technology, the bending forming of the tube consists of the transition section and the stable forming section. However, because of the continuous movement of the bending die and tube in the transition section, the forming mechanism of the tube in the transition zone is relatively complex and still unclear. In addition, due to the complexity of the cross-section deformation of the finned special-shaped tube (FSST), its application in the heat dissipation pipeline of aerospace vehicles is severely hindered. To address the above issues, in this paper, a 3D free-bending forming process method, which can effectively coordinate the movement of FSST and the bending die in the transition section, was proposed. Meanwhile, an analytical model of FSST bending forming was established, which can effectively characterize the elastic-plastic evolution of the FSST cross-section and match the bending radius with the cross-sectional bending moment effectively. Then, the effectiveness of the process method and analytical model was verified by finite element model (FEM), and experiments. Further, FEM and experiments were used to investigate the influence of the process parameters of the transition section on the forming radius and cross-section deformation of FSST after springback. The results from this study show that reasonable coordination of the rotation speed of the bending die and the advancing speed of FSST in the transition zone can improve the forming quality of FSST. [ABSTRACT FROM AUTHOR]

Welded T-joints are commonly used in manufacturing of stiffened panels or crossbeams. However, welding of web-to-flange joint induces residual stresses and distortions resulting in significant challenges during both manufacturing and service. These issues can ultimately impact the structural performance, including fatigue and stability, and lifetime of the weldment. The purpose of current paper is determining the distribution and magnitude of manufacturing-induced longitudinal residual stresses in welded T-joints. Influence of hot rolling, thermal cutting, prestressing, welding, etc. are all included using the so-called contour method. Deformed surfaces are measured using coordinate measuring machine after wire electrical discharge machining of specimens. An inverse linear elastic finite element analysis is carried out for assessing residual stresses after data smoothing. Two-dimensional longitudinal residual stress patterns are evaluated in representative cross-sections clearly indicating high stress peaks near the welds, even exceeding yield strength of the base material. In addition, longitudinal membrane residual stresses are determined based on through-thickness stresses. In addition, a simplified residual stress model, satisfying the requirement for equilibrium of internal forces and bending moments, is developed for welded T-joints with double-sided fillet welds based on contour method results. [Display omitted] • A novel application of contour method is used for determining residual stresses. • Longitudinal residual stresses are assessed in welded T-joints. • Tensile residual stress peaks near the welds exceed yield strength of the material. • A simplified residual stress model is developed for welded structural steel T-joints. • Residual stress model satisfies equilibrium of internal forces and bending moments. [ABSTRACT FROM AUTHOR]

A non-negligible percentage of steel products for civil and industrial constructions is realised with members characterised by a mono-symmetric cross-section. The non-coincidence between the centroid and the shear centre reflects in a quite complex behaviour that is remarkably influenced by the warping effects. Usually, frame design is based on the output data of commercial Finite Element Analysis Packages (FEAPs) but only few of them offer a refined beam element formulation able to reproduce the response of non-bisymmetric cross-section members (like the 7 degrees of freedom, DOFs, beam element). As a consequence, warping effects are usually neglected in routine design, leading in several cases to assess non-correct internal stresses, global displacements and critical buckling multipliers. This paper is focussed on mono-symmetric cross-section members and deals with the influence of the interaction between axial force, bending moments and bimoment in linear elastic range. In particular, the two strategies that FE developers usually adopt, in the 7 DOFs beam formulation, to pass from the local to the global reference system are herein shortly introduced and discussed. The effects of the associated transformation matrices have been investigated in few examples, also reproduced via closed expressions derived from the mixed torsion theory and FE shell models. Paper outcomes show that the results in terms of generalised displacements, internal forces and, consequently, stress distribution along the member cross-section are significantly different, strictly depending on the adopted transformation matrix. The importance of a correct evaluation of the bimoment distribution is stressed also by the fact that the new edition of the EN1993-1-1, expected in the next months, includes also the bimoment contribution for member checks. • Interaction between bending moments and bimoment in linear elastic range for mono-symmetric cross-section members. • The two strategies adopted in 7DOFs beam formulation, to pass from the local to the global reference system are discussed. • Vlasov's theorems are discussed and applied to example of practical interest for structural design. • Displacements and internal forces are significantly different, strictly depending on the adopted transformation matrix. [ABSTRACT FROM AUTHOR]

The shear stability of steel webs near the support section for long-span composite girders with corrugated steel webs is one of the main control factors for structural safety, which should be paid special attention to. Generally, concrete is poured on the inner side of corrugated steel webs to improve its shear stability, but encased concrete increases the weight of the girder, raises the difficulty of the construction process, and reduces the efficiency of the prestressing application. This paper proposes a new type of stiffened corrugated steel webs at the support area by adopting vertical or/and horizontal stiffeners instead of encased concrete. In order to explore the shear performance of proposed stiffened corrugated steel webs, experimental and numerical investigations were carried out in the present paper and the companion paper [1] , respectively. Four steel I-girders with corrugated webs considering different stiffener arrangements were designed and tested under shear loading. The failure modes, shear strength and stiffness, strain distributions were obtained and analyzed in detail. The test results show that all specimens failed due to interactive shear buckling of corrugated steel web; shear buckling occurred between horizontal stiffeners and bottom flange for horizontal stiffened corrugated steel webs, but extended to the entire height for vertical stiffened corrugated steel webs, the stiffeners distorted associated with the deformation of corrugated steel web. Shear strength of corrugated steel webs can be improved by vertical and horizontal stiffeners. The vertical stiffeners do not affect the "accordion effect" of corrugated steel webs, but the horizontal stiffeners increase the axial stiffness of corrugated steel web in local area and resist bending moment together with top and bottom flanges. The shear strain of stiffened corrugated steel web still distributes uniformly along the height of the web. All the experimental results are then employed in the companion paper for the validation of finite element method and the evaluation of existing analytical models for predicting shear strength of un-stiffened and stiffened corrugated steel webs. • We proposed a new type of stiffened corrugated steel web. • Shear behavior of steel I-girder with stiffened corrugated webs has been experimentally investigated. • Shear strength of corrugated steel web can be improved by vertical and lateral stiffeners. • Lateral stiffeners increase the axial stiffness of corrugated steel webs in local area. [ABSTRACT FROM AUTHOR]

Abstract Due to being increasingly used in infrastructure, studying stress concentration in concrete-filled steel tubular joints is necessary. In this study, the variation of the maximum Stress Concentration Factor (SCF max) with non-dimensional geometric parameters in steel circular hollow section brace welded to concrete-filled circular hollow section chord (CHS-to-CFCHS) T-joints under in-plane and out-of-plane bending moment has been investigated. A database of the maximum SCFs in CHS-to-CFCHS T-joints under in-plane and out-of-plane bending moment is developed based on three-dimensional (3D) finite element (FE) models. The 3D FE models developed using ABAQUS software, have been verified using experimental results. Graphs showing variation of the maximum SCF, in CHS-to-CFCHS T-joints, with non-dimensional geometric parameters have been produced and compared with those for non-filled empty T-joints. Parametric equations for predicting the maximum SCFs in CHS-to-CFCHS T-joints under in-plane and out-of-plane bending moment have been developed in a multiple nonlinear regression analysis. There is a good agreement between the maximum SCFs predicted by the parametric equations and those determined from the experiments. Highlights • The effect of the concrete infill in reducing the SCF max is moderate under in-plane bending and its effect is significant under out-of-plane bending. • Parameter β has very little effect on the SCF max under in-plane bending and has significant effect under out-of-plane bending. • The trend in variation of the SCF max under in-plane and out-of-plane bending with parameter τ in CHS-to-CFCHS T-joints is similar to that in empty T-joints yet its effect is less under out-of-plane bending in the CHS-to-CFCHS T-joints due to significant effect of the concrete infill. • The trend in variation of the SCF max under in-plane and out-of-plane bending with parameter γ in CHS-to-CFCHS T-joints is similar to that in empty T-joints yet its effect is less under out-of-plane bending in the CHS-to-CFCHS T-joints due to significant effect of the concrete infill. • Parameter α has no effect on the SCF max under out-of-plane bending. [ABSTRACT FROM AUTHOR]

Abstract Structural design formulae for beam-columns require accurate end points (i.e. accurate resistance predictions for pure compression and pure bending), should be of suitable form to capture the interaction between the different components of loading and should take due account of the influence of a moment gradient along the member length. However, existing design rules for stainless steel beam-columns do not fully capture the interaction responses observed in experiments and numerical simulations, and are often tied to inaccurate end points; the adopted equivalent uniform moment factors can also be unconservative in the case of high moment gradients. As a consequence, previous comparisons of stainless steel beam-column experimental and finite element results with codified strength predictions have often revealed a rather high degree of scatter. This prompted the present research, to develop improved design proposals for stainless steel square hollow section (SHS) and rectangular hollow section (RHS) beam-columns under moment gradients. To this end, revised design approaches are proposed firstly through the derivation of more accurate design interaction curves for stainless steel SHS and RHS beam-columns under uniform bending moment and then through the employment of more suitable equivalent uniform moment factors, underpinned by and validated against over 1500 test and numerical data points. The new design approaches are shown to lead to improved (safe-sided, accurate and consistent) resistance predictions for stainless steel SHS and RHS beam-columns under moment gradients over the current codified design rules. Finally, statistical analyses are performed to demonstrate the reliability of the proposed approaches, according to the requirements specified in EN 1990. Highlights • Current codified design rules for stainless steel beam-columns under moment gradients were briefly reviewed. • Shortcomings in the existing design codes were identified, and methodologies for overcoming them were described. • Improved design approach for stainless steel beam-columns under moment gradients was proposed. • Assessment of the new proposal indicates a higher level of design accuracy and consistency. • The reliability of the new proposal has been confirmed by means of statistical analyses. [ABSTRACT FROM AUTHOR]

Beam-to-beam connections are widely used in steel structures, especially in large floor applications and in cases where they are dictated by architectural restrictions. This type of connection is often designed without rotational restrictions (pinned connections), leading to relatively high bending capacity demands for the connected secondary beam, particularly when larger spans are employed. A commonly used practice to limit the above mentioned effect is to design beam-to-beam fixed connections at both ends of the secondary beam. Although joints transferring bending moments are covered in EN-1993 Part 1–8, there is no standardization for beam-to-beam fixed connections, often resulting in questions about their rotational capacity. Moreover, there is very little guidance on the design of beam-to-beam connections in the open literature. Therefore, this paper presents a comprehensive investigation of the beam-to-beam eccentric end plate connections using finite element analysis following the experimental tests. The parametric study is conducted using experimental data to propose a reliable analytical model of structural behavior under monotonic gravitational loading. The eccentric end plate connection exhibited satisfactory rotational stiffness and bending capacity. The failure mechanism on the connection parts is also presented for a better evaluation of the key parameters affecting the connection's structural performance. • Beam-to-beam eccentric end plate connections using finite element analysis. • Stiffeners and end plates are the critical components for failure. • The span of the secondary beam length directly affects the initial stiffness boundary. • Larger section sizes lead to the semi-rigid classification. • Level difference has an effect on the initial stiffness and the joint strength. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the cross-section behaviour and resistance of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment. An experimental programme, including initial local geometric imperfection measurements and ten major-axis eccentric compression tests, was firstly conducted, with the test setup, procedures and results reported in detail. This was followed by a numerical modelling programme, where finite element models were developed and validated against the major-axis eccentric compression test results and then adopted to conduct parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. Based on the obtained test and numerical data, the design interaction curves for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative resistance predictions, due to the conservative bending end point and inefficient linear shape of the design interaction curve. New design interaction curves were also developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment than the codified design interaction curves. • The local buckling of ferritic stainless steel channel sections under major-axis combined loading was studied. • Ten major-axis eccentric compression tests were carried out. • FE models were developed to simulate the test results and then adopted to conduct parametric studies. • The codified design interaction curves were evaluated, with shortcomings highlighted. • New improved design interaction curves were proposed. [ABSTRACT FROM AUTHOR]

An improved aluminium alloy gusset joint (I-AAGJ) with two types of shear connectors (SCs) and a peripheral bending system (PBS) is proposed to address traditional aluminium alloy gusset joint (T-AAGJ) imperfections. The mechanical performance of the I-AAGJ, including axial stiffness, in-plane and out-of-plane flexural stiffness, and ultimate bearing capacity, is investigated by full-scale testing under simplex and complex load states. Numerical simulation results of I-AAGJ behaviour are presented via nonlinear finite element analysis (FEA). Three-phase models are determined to explain the I-AAGJ deformation process. In the linear phase, PBS is proven to provide significant assistance for the joint bearing axial force and bending moment. By comparing with the T-AAGJ, an at least 30% improvement of joint stiffness along three directions can be observed respectively. In the nonlinear phase, SCs strengthen the joint by delaying plastic hinge formation and preventing gusset plates from being folded. The complex load state of lower level has a negligible impact on the I-AAGJ mechanical performance, while that of higher level still has to break through the protection of PBS and SCs before it destructs the joint. • An improved aluminium alloy gusset joint with two types of shear connectors and peripheral bending system is proposed. • Semi-rigid mechanical performance of the joint can be observed in both full-scale tests and numerical analysis. • The improved joint shows higher stiffness and bearing capacity along axial and in-plane and out-of-plane flexural directions. • Lower stiffness degradation will be caused by complex load states due to the assistance from the peripheral bending system. [ABSTRACT FROM AUTHOR]

To investigate the overall stability behavior of Q460 high strength steel (HSS) welded I-section overhanging beams and develop the corresponding design method of codified specifications, nine overhanging beams with various top flange strengthened section forms and overhanging span length ratios were tested under concentrated loads. The initial geometric imperfections and residual stresses were measured in advance. Test results indicate that the overall stability capacity of the specimens decreases with the increase of overhanging span length ratio and top flange strengthened has a greater effect on the overall stability capacity of overhanging beams than overhanging span length ratio when the dominative stability segment of specimens is located at the simply supported span. Finite element analysis (FEA) models verified by test results were established to examine the effects of load form, load ratio, section form, height-to-width ratio, simply supported span length and overhanging span length ratio on the overall stability capacity of Q460 HSS welded I-section overhanging beams. On the basis of the eigenvalue buckling analysis results and the formulas for the elastic moment of simply supported beam stipulated in Design code of steel structures (GB50017-2017), the calculation formulas of elastic critical moment for overhanging beams were obtained by regression. Furthermore, the calculation formulas of ultimate bending moment for Q460 HSS welded I-section overhanging beams were proposed based on the obtained formulas for elastic critical moment of such beams, test results and nonlinear buckling analysis results. • Tests on welded I-section overhanging beams for Q460 high strength steel. • The finite element model considering initial geometric imperfections and residual stresses was developed and verified against tests. • The extensive finite element parametric analyses were carried out for study on design method. • The overall stability design method of overhanging beams for Q460 high strength steel was proposed. [ABSTRACT FROM AUTHOR]

Buried circular corrugated steel arches (BCCSAs) are often adopted in underground engineering. However, the current design specifications cannot accurately estimate the BCCSA's load-bearing capacity due to the complicated interaction between the soil and the arch. This paper presents the strength design recommendations for deeply buried circular corrugated steel arches with various rise–span ratios under axial compression and under combined axial compression and bending moment respectively, with meeting a proposed width–thickness ratio limit of the BCCSA for local buckling prevention. At first, a finite element model (FEM) of sinusoidally corrugated steel plate (S-CSP) for analyzing its local plate buckling under axial compression (FEM-l) is established, and this FEM can eliminate other possible buckling modes except the local buckling mode by constraining the out-of-plane displacement at the crest and valley lines in S-CSPs. Through FEM-l, the local buckling behaviors of S-CSPs are studied and the width–thickness ratio limit of S-CSPs under axial compression for local buckling prevention is determined in terms of a design principle that local buckling of plate elements does not occur before fully sectional yielding. Then, a global arch-spring model of BCCSA is established for analyzing its elastic global buckling, with considering the interaction between the soil and arches by simplifying the radial restraint of soil as radial unidirectional springs around the arch. The normalized slenderness of BCCSA in the arch-spring model is obtained from its elastic global buckling load calculated by theoretical derivation with bidirectional spring assumption. Finally, the ultimate load-bearing capacity of BCCSAs is calculated by employing elastoplastic finite element models under axial compression and under combined axial compression and bending moment respectively. Based on extensive numerical results obtained in this study, the conservative strength design methods for BCCSAs are proposed in practical engineering applications. [Display omitted] • Local buckling prevention is implemented by proposed width–thickness ratio limit. • The soil radial restraint is equivalent to unidirectional radial springs. • Initial imperfection amplitude affects the load-bearing capacity of the arch much. • Axial compression stability coefficient under various rise–span ratios is proposed. • Load-bearing capacity is proposed for combined axial compression and bending. [ABSTRACT FROM AUTHOR]

This paper reports an experimental and numerical investigation into the buckling behaviour and resistance of press-braked ferritic stainless steel slender channel section beam–columns under combined compression and minor-axis bending moment. An experimental programme was firstly performed, including material coupon tests, initial global and local geometric imperfection measurements and ten beam–column tests. The experimental programme was followed by a numerical modelling programme, where finite element models were developed and validated against the experimental results and then adopted to conduct parametric studies to generate additional numerical data. Based on the obtained test and numerical data, the existing design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated and found to result in conservative and scattered resistance predictions. An improved design interaction curve, anchored to more accurate end points and featuring more appropriate shape, was then developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel slender channel section beam–columns over the codified design interaction curves. Statistical analyses were also performed to confirm the reliability of the new proposal. • The behaviour of press-braked ferritic stainless steel slender channel section beam–columns was studied. • Ten beam–column tests were conducted. • FE models were developed to validate against the test results and then used to conduct parametric studies. • The codified design interaction curves were evaluated, revealing conservatism. • A new improved design interaction curve was developed. [ABSTRACT FROM AUTHOR]

This two-part contribution presents a novel theory of bending of thin-walled beams with influence of shear (TBTS). The theory is based on the Vlasov’s general beam theory as well as on the Timoshenko’s beam bending theory. The theory is valid for general thin-walled open beam cross-sections. Part I is devoted to the theoretical developments and part II discusses analytical and obtained numerical results. The theory is based on a kinematics assuming that the cross-section maintains its shape and including three independent warping parameters due to shear. Poison’s effect is ignored, as well as warping constrains due to shear (as it known, those effect have small and for engineering praxis neglected influence on the stresses and displacements). Closed-form analytical results are obtained for three-dimensional expressions of the normal and shear stresses. Under general transverse loads, reduced to the cross-section principal pole, the beam will be subjected to bending with influence of shear and in addition to torsion due to shear with respect to the cross-section principal pole and to tension/compression due to shear, in the case of non-symmetrical cross-sections. The beam will be subjected to bending with influence of shear (i) in the plane of symmetry under the loads in that plane and in addition to tension/compression due to shear, (ii) in the plane through the principal pole orthogonal to the plane of symmetry under the loads in that plane and in addition to torsion with respect to the principal pole, in the case of the mono-symmetrical cross-sections. The beam will be subjected to bending with influence of shear in the principal planes, in the case of the bi-symmetrical cross-sections. The principal cross-section axes as well as the principal pole are defined by the classical Vlasov’s theory of thin-walled beams of open section. The analytical and numerical analyses presented in part II include comparisons with the classical beam theory, Euler-Bernoulli’ theory (EBBT) as well as comparisons with the finite element method (FEM). [ABSTRACT FROM AUTHOR]

In this study, a refined nonlinear finite-element (FE) model of steel-concrete composite beam (SCCB) capable of accommodating various effects such as the initial geometric imperfection, residual stress, interface slip, geometric nonlinearity, and material nonlinearity is developed to study the distortional instability of SCCBs under negative bending moment. The accuracy of the model is validated by publicly available results previously observed by experiments. On the basis of the refined nonlinear FE model, the ultimate bending moment of 54 groups of SCCBs with varying cross-section parameters is calculated. Also, the effects of the force ratio of the SCCB, width–thickness ratio of the compression flange, shear connection degree, and height–thickness ratio of the web on the ultimate bending moment stability coefficient of SCCB in negative bending moment area are investigated in detail. Results show that the effect of the degree of shear connection on the stability coefficient of the SCCB is insignificant, while the stability coefficient decreases with the increase of the remaining parameters, among which the effect of the height–thickness ratio of the web is proven to be the most significant. Finally, considering various effects aforementioned properly, practical formulas are proposed to compute slenderness ratio and ultimate bending moment stability coefficient of SCCB in a concise form, which are shown to be consistent with the FE modelling and experimental results, and thus are suitable for engineering design. [ABSTRACT FROM AUTHOR]

Owing to the limited literature on the impact performance of steel beams with hexagonal web opening (SBHWOs), this study conducted drop hammer tests and used finite element methods to investigate the dynamic response of SBHWOs subjected to impact loads. The impact force, displacements and accelerations of the beam, and the strains around a hexagonal web opening were collected during the tests. The impact process was captured by a high-speed camera. Furthermore, a finite element model was developed to analyze the post-impact internal forces of SBHWO, development and distribution of stresses in its web, the effect of impact position, and differences with solid webbed steel beam (SWSB). Results showed that the impact force, displacements, and web-post buckling of the SBHWO were significantly affected by impact energy, spacing between openings, and opening height. The average energy absorption ratio of the SBHWOs was found to be 51.56%. Additionally, the midspan acceleration decayed rapidly after impact and spread from the midspan towards the supports. The finite element analysis proved that numerical models can be used to accurately predict the dynamic responses of a SBHWO subjected to impact loads. The axial forces, shear forces, and bending moments of the SBHWO redistribute themselves during the impact, and the magnitude of the internal forces increased very rapidly before decaying gradually. The pattern through which stress developed in the SBHWO web was obtained using finite element modeling. A position close to the support approximately 1/4 of the calculated length of the SBHWO was the most unfavorable impact position. The SWSB was more resistant to impact load than the SBHWO. • The mechanical properties of steel beams with hexagonal web opening (SBHWOs) subjected to impact loads were studied by experiments and finite element method. • The impact force, displacements, and web-post buckling of the SBHWO were significantly affected by impact energy, spacing between openings, and opening height. • The average energy absorption ratio of the SBHWOs was found to be 51.56%. • The axial forces, shear forces, and bending moments of the SBHWO redistribute themselves during the impact. • A position close to the support approximately 1/4 of the calculated length of the SBHWO was the most unfavorable impact position. • The solid webbed steel beam (SWSB) was more resistant to impact load than the SBHWO. [ABSTRACT FROM AUTHOR]

There is no commonly accepted and reliable design method to determine the lateral–torsional buckling (LTB) resistance of steel trapezoidally corrugated web girders. Therefore, the focus of the current paper is on the investigation of this failure mode, detailed evaluation of the structural behavior and determination of the accurate LTB resistance. An advanced finite element (FE) model is developed and validated using the results of laboratory test performed at the Budapest University of Technology and Economics in 2018. Based on the experimental background virtual tests are performed on a simply supported beam subjected by pure bending moment. The effect of the different flange sizes, corrugation layouts, boundary conditions and steel grade including high-strength steel as well, are investigated. Two kinds of parametric studies are performed using (i) deterministic and (ii) stochastic nonlinear analysis. In both cases the imperfections have a key role in the FEM-based resistance calculation. Therefore, the imperfections are considered as initial geometric imperfections and residual stress, and also as equivalent geometric imperfections and their results are compared. The required equivalent geometric imperfection magnitude is determined and proposed in such a way to achieve the same impact as the initial geometric imperfection and residual stresses have. By both the deterministic and stochastic analysis results the required buckling curve of the Eurocode is determined by reliability assessment. The results of the two different analyses are compared and design recommendation is given for reduction factor determination for trapezoidally corrugated web girders. • Advanced finite element model is developed, verified and validated based on own experimental tests specimens. • Imperfection sensitivity study is performed. • Both residual stresses and initial geometric imperfections are considered. • Effects of the corrugated web layout, the boundary conditions and the steel grade are studied. • Deterministic and stochastic nonlinear analyses are performed. • Reliability assessment is performed. • New design method is developed. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations of the buckling behaviour and resistance of S960 ultra-high strength steel slender welded I-section beam–columns under combined compression and minor-axis bending moment. An experimental programme, including initial geometric imperfection measurements and eight beam–column tests, was firstly conducted. The test procedures, setups and results were fully reported. Following the experimental programme, a numerical modelling programme was carried out, with finite element models initially developed and validated against the test results and then employed to conduct parametric studies to generate further numerical data. On the basis of the test and numerical data, the relevant design interaction curves, as provided in the European code, Australian standard and American specification, were evaluated for their applicability to S960 ultra-high strength steel slender welded I-section beam–columns. The evaluation results revealed that all three codified design interaction curves lead to conservative resistance predictions, mainly owing to the conservative end points (i.e. column buckling strength and cross-section minor-axis bending resistance). Finally, a revised Eurocode design interaction curve, with improved compression end point determined from more accurate column buckling curve and bending end point determined from the direct strength method, was finally proposed, and shown to result in more accurate resistance predictions for S960 ultra-high strength steel slender welded I-section beam–columns than the codified design interaction curves. • The buckling behaviour of S960 ultra-high strength steel slender welded I-section beam–columns is studied. • Eight beam–column tests on S960 ultra-high strength steel slender welded I-sections are conducted. • FE models are developed and validated against the test results and then used to perform parametric studies. • The applicability of the relevant codified design interaction curves is assessed, revealing inaccuracy. • A new design interaction curve is proposed, resulting in more accurate failure load predictions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Due to the growing number of used corrugated webs in structural members such as buildings and bridges, their behaviour and strength should extensively be investigated. Accordingly, this paper is an extension to the experimental study recently conducted by the authors on trapezoidally corrugated web girders (CWGs) under pure bending moment (PBM). In particular, this paper focuses on the flexural strengths of CWGs, for highway bridges, under the effect of elastic and inelastic lateral–torsional buckling (LTB). Currently, ABAQUS programme is employed to generate linear and nonlinear finite element (FE) analyses. Firstly, verified FE models using the above mentioned experimental data are adopted to generate parametric studies using large corrugation dimensions (used in actual bridges). Girder length, defined by the number of the corrugation waves, changes from 4 to 36 waves with an increment of 4 waves. Furthermore, changes in the corrugated web height, web thickness, flange thicknesses, flange widths and corrugation angle have been considered. The elastic FE results are compared with available prediction equations in the literature, which calculate the critical LTB stress using different warping constants. The results show that the calculations using Nguyen et al's method (2010) is the best. With regard to the design strength, the comparisons exhibit that original predictions of Lindner equation (1990), EC3-1-1 (2004) and AISC (2010) are highly conservative. Hence, modified versions for Lindner equation (1990), EC3-1-1 (2004) and AISC (2010) are suggested to provide more suitable design strengths for CWGs. • Flexural strengths of CWGs under the effect of lateral–torsional buckling (LTB) are presented. • Using ABAQUS, 3D finite element models under pure BM are developed. • The feasibility of current design codes to design the CWGs is evaluated. • The modified design models are shown to predict well the strengths of CWGs. [ABSTRACT FROM AUTHOR]

This paper presents experimental and finite element analyses of the ultimate strength and buckling collapse behaviours of a single- and a double-hull girder with a large deck opening subjected to cyclic ultimate bending moments. The cyclic ultimate bending moments here means that the external load in every cycle exceed the ultimate load bearing capacity of the specimens; the aim is to understand how the structures behave under this kind of extreme but not unusual load condition. The results showed that, in general, the plastic deformation would be accumulated under the cyclic loads, and the buckling collapse would expand from the deck plates to the broadside plates in both specimens. However, even if overall buckling occurred on both specimens, the specimens still preserved most of the load bearing capacity for the next ultimate loading cycles, but the double-hull specimen had a higher safety stock. In addition, the different behaviours of these two types of specimens were recorded, and the reasons behind were deeply analysed, which has helped us gain a deeper understanding of how these complex engineering structures perform under this kind of extreme but not well-studied load condition. The conclusions drawn in this works would be beneficial to improve the structural safety of ship hull girders and other similar thin-walled structures. • The collapse behaviours of box type hull girder under cyclic ultimate moments were analysed by experiments and FEM. • Coupled effect of structural complexity and loading condition on the collapse behaviour of the girders was investigated. • The difference between single- and double-hull girders regarding the collapse behaviours was compared and deeply analysed. • Suggestions on how to improve the structural safety under extreme load condition were provided. [ABSTRACT FROM AUTHOR]

The mechanical behavior of the traditional special-shaped concrete-filled steel tubular (CFST) columns can be improved by employing longitudinal stiffeners or using multi-cell cross-section. In practical application, the stiffened and multi-cell L-shaped CFSTs are often subjected to bi-directional loading. However, there are only few research studies on their performance as loaded eccentrically with different orientations of the loading and there is no relevant design guideline. This paper reports tests on 16 L-shaped CFST columns (nine stiffened, six multi-cell specimens and one reference specimen) loaded in eccentric compression. The main variables were the angle indicating the orientation of the load action line (0°, 45°, 135°, 180° and 225°), load eccentricity ratio (0, 0.25 and 0.5) and slenderness ratio (31.5 and 41.9). Finite element models for the eccentrically loaded stiffened and multi-cell L-shaped CFST columns were developed. Based on the parametric analysis, practical design methods were proposed for predicting the bearing capacity based on the stability loss and the axial force vs. bending moment interaction diagrams for the members considering the influence of the load orientation at the end face of the column. [ABSTRACT FROM AUTHOR]

For flexural thin-walled section beams, the ultimate strength is significantly affected by the interaction of different local buckling modes associated with combined bending and shear stresses. This paper provides a comprehensive analytical and numerical study of elastic buckling of thin-walled channels subjected to different combinations of bending and shear stresses. The commercial ABAQUS software package using Finite Element Method (FEM) has been used to perform the elastic buckling analyses of the channel sections. The results are benchmarked against those from the Semi-Analytical Finite Strip Method (SAFSM) for the cases of pure bending and shear only. Two typical types of channels with and without lips are selected for investigation. To study the effect of different combinations of bending and shear on the buckling stresses, different normal stress distributions and equilibrating shear stresses are applied at two end cross-sections of the channels to maintain static equilibrium. Different types of interactions which occur during the buckling analyses are studied by varying the ratios of bending moments resulting from the modelled longitudinal stresses. A new concept for the elastic local buckling interaction based on the Average Bending Moment (ABM) at buckling is provided. In addition, an explicit approach for local buckling loads of channels under different combinations of bending and shear is also introduced for the practical design use. The results from this explicit solution for elastic buckling can be used as direct inputs for an explicit Direct Strength Method (DSM) design of members under combined bending and shear. • A comprehensive study of elastic buckling of thin-walled channels under combined bending and shear stresses is performed • ABAQUS software package using FEM is used to conduct elastic buckling analyses of thin-walled channel sections • Results are benchmarked against those from the Semi-Analytical Finite Strip Method for the cases of pure bending and shear only cases • A new concept for elastic local buckling interaction based on the Average Bending Moment (ABM) at buckling is provided • Results from the explicit solution for elastic buckling analyses can be used in the Direct Strength Method (DSM) of design [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on hot-rolled stainless steel channel sections subjected to combined compression and minor-axis bending moment have been conducted and are fully reported in the present paper. The testing programme included initial local geometric imperfection measurements and ten minor-axis eccentric compression (combined loading) tests. The numerical modelling programme comprised a validation study, where finite element models were developed and validated against the test results, and a series of parametric studies, where the developed finite element models were adopted to generate further numerical data over a wide range of cross-section dimensions and loading combinations. The experimentally and numerically obtained data were used to assess the accuracy of the design interaction curves for hot-rolled stainless steel channel sections under minor-axis combined loading, as given in the European code and American specification. The assessment results generally reveal that the design interaction curves provided in the main body of the two design codes lead to unduly conservative and scattered failure load predictions, mainly owing to the conservative end points (i.e. the cross-section compression and bending resistances), which are calculated without considering material strain hardening. The appendix of each design code also provides an alternative method that uses the continuous strength method to account for material strain hardening in calculating the end points of the design interaction curve, and is shown to result in much more accurate and consistent predictions of failure load for hot-rolled stainless steel channel sections under combined compression and minor-axis bending moment. • The behaviour of hot-rolled stainless steel channel sections under minor-axis combined loading is studied. • Ten eccentric compression tests on hot-rolled stainless steel channel section stub columns are conducted. • FE models are developed and validated against the test results and then used to conduct parametric studies. • The codified design interaction curves are assessed, indicating conservatism. • The CSM-based codified design interaction curves are shown to yield higher accuracy. [ABSTRACT FROM AUTHOR]

Pipe elbows, also known as pipe bends, are important components of a piping system. These curved elements are very flexible when compared to their straight counterparts, and are often responsible for reducing the reaction forces and moments within the piping system. However, due to large deformations, the elbows are more likely to exceed their stress limits. The effect of in-plane bending on plastic limit loads of Functionally Graded (FG) pipe bends is presented using three-dimensional non-linear finite element analysis and a micromechanical constitutive model. The effective properties of the material are estimated by the Mori–Tanaka homogenization scheme and the TTO plasticity model. The analysis was carried out for different loading cases, geometries and volume fraction distribution. The results showed that an FG elbow has a very distinct behavior comparatively to a similar homogeneous elbow made out of metal, specially in terms of limit moments and stress distribution. Finally, an analytical model to estimate the limit moment of FG elbows is presented. • Functionally Graded pipe elbows provide wear resistance and ductility without the associated interfacial problems. • The volume fraction distribution of ceramic inclusions was found to play a major role on the overall behavior of FGM pipes. • Micromechanical Elastoplastic models can be easily employed to simulate the behavior of FGM metal-matrix pipe elements. • The volume fraction distribution of ceramic inclusions plays a major role on the overall bending behavior of FGM pipe elbows. • A predicting equation for bending of FGM pipes was developed for limit bending moments. [ABSTRACT FROM AUTHOR]

This study proposes a new analytical flexure theory that considers the shear deformation of the web and flange of a thin-walled box girder. Starting with the relationship between the strain and displacement of each slab, the flexural displacement function of thin-walled box girders considering the shear deformation effect is derived by using the deformation continuity condition. Compared with the traditional flexural displacement model, this function obtained by the theoretical analysis is more rigorous and can be transformed into the flexural displacement function of the traditional shear lag or Timoshenko beam by eliminating some parameters. Then, according to the balance conditions of axial force and bending moment, the shear deflection deformation state and Euler–Bernoulli beam deflection deformation state are decoupled. On this basis, a new convenient method for calculating the warping stress and shear deflection of thin-walled girders is proposed. Furthermore, a simplified analysis method for converting continuous box girders into simply supported beams is proposed on the basis of continuity condition of shear deflection at middle supports. Taking into account the shear deflection deformation state, a beam-type finite element model considering the shear deformations of each box wall is developed by using Hermite polynomials to analyze the complex variable cross-section box girder. Finally, numerical examples are used to verify the effectiveness of the simplified method and the beam-type finite element model. Numerical examples show that the flexural stress and deflection calculated by the proposed method agree well with the three-dimensional finite element model analysis results. The shear warping normal stress has a larger value at the shear force discontinuity point. In the control cross-section, the normal warping stress and shear deflection caused by shear deformation both exceed 75% and 38% of stress and deflection of the Euler–Bernoulli beam, respectively. • A new flexural displacement function for thin-walled box girders is proposed. • The shear deflection and elementary beam deflection are decoupled. • A simplified method for flexural analysis of thin-walled box girder is proposed. • The correction formula of shear warping stress is obtained. [ABSTRACT FROM AUTHOR]

Abstract: Trapezoidal sheeting of thin-walled steel is applied frequently for roofing and cladding. As such, it is loaded by a concentrated load (at the support) and a bending moment. A recently developed model to predict the sheeting's failure behaviour leaves the question open whether mode jumping (the phenomenon where a plate dynamically changes its buckling mode during an increasing load) should be taken into account in the model. This article presents the analytical and finite element modelling of square and long plates, which, depending on the boundary conditions, may represent the compressed flange of trapezoidal sheeting. The analytical modelling is based on the combination of several displacement functions and using the principle of minimal potential energy. Hereafter the stability of each part of the resulting equilibrium curves is determined. A spin-off of the analytical model is an analytical expression for a current curve-fitted based prediction formula for the post/pre-buckling stiffness ratio by Rhodes. Furthermore, the accuracy range of a solution by Williams and Walker for the far-post buckling behaviour can be confirmed. The finite element modelling has been carried out by implicit dynamic, and explicit (dynamic) simulations. Both for the load levels and the buckling mode sequences, the analytical and finite element models give equivalent results. It is concluded that for the specific boundary conditions that represent the situation of a compressed flange for trapezoidal sheeting, it is very likely that mode jumping will not occur. [Copyright &y& Elsevier]

Abstract: Experimental and numerical investigation of cold-formed lean duplex stainless steel flexural members is presented in this paper. The test specimens were cold-rolled from flat plates of lean duplex stainless steel with the nominal 0.2% proof stress of 450MPa. Specimens of square and rectangular hollow sections subjected to both major and minor axes bending were tested. A finite element model has been created and verified against the test results using the material properties obtained from coupon tests. It is shown that the model can accurately predict the behaviour of lean duplex stainless steel flexural members. An extensive parametric study was carried out using the verified finite element model. The test and numerical results as well as the available data on lean duplex beams are compared with design strengths predicted by various existing design rules, such as the American Specification, Australian/New Zealand Standard, European Code and direct strength method for cold-formed stainless steel. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that these current design rules provide conservative predictions to the design strengths of lean duplex stainless steel flexural members. In this study, modified design rules on the American Specification, Australian/New Zealand Standard, European Code and direct strength method are proposed, which are shown to improve the accuracy of these design rules in a reliable manner. [Copyright &y& Elsevier]

Abstract: In a recent paper (Gonçalves and Camotim, 2013 [1]), the authors presented an investigation concerning the buckling (bifurcation) behaviour of uniformly compressed thin-walled tubes with regular polygonal cross-sections (RCPS). The present paper complements the previous work by addressing the local and distortional buckling behaviour of RCPS members subjected to bending or torsion and aims at providing a novel insight into these phenomena. In particular, the specialization of Generalized Beam Theory (GBT) for RCPS, as recently proposed in Gonçalves and Camotim (2013) [2], is employed to obtain closed-form analytical solutions and also to carry out parametric studies by means of numerical analyses which are both computationally efficient (due to the small number of d.o.f. involved) and clarifying (due to the modal decomposition features of GBT). For validation purposes, solutions taken from the literature and also standard shell finite element model results are employed. [Copyright &y& Elsevier]

Abstract: This paper investigated the bending strength of girth-welded stainless steel circular hollow sections by numerical method. At first, finite element simulation of girth welding process was carried out to obtain the weld-induced residual stresses and deformations employing sequentially coupled three-dimensional thermo-mechanical finite element formulation. Then, nonlinear finite element analysis in which the moment versus end-rotation response, the ultimate moment resistance and the failure mode of the girth-welded circular hollow sections under pure bending were explored incorporating the residual stresses and depressions along with the initial global geometric imperfections was performed. Feasibility of adopting the current codified provisions (Eurocode 3) for stainless steel circular hollow sections in bending as the cross-section slenderness limit for girth-welded stainless steel circular hollow section flexural members was also examined. Results showed that the flexural behavior of girth-welded stainless steel circular hollow sections always involves local buckling near the girth weld on the compression side, which significantly affects the moment versus end-rotation behavior. Moreover, the results demonstrated that the Class 3 slenderness limit of 280 from Eurocode 3 for stainless steel circular hollow sections in flexure may be applied to girth-welded stainless steel circular hollow sections subjected to bending. [Copyright &y& Elsevier]

Abstract: In this paper we present the Finite Element modeling of the bending of micropolar elastic plates. Based on our recently published enhanced mathematical model for Cosserat plate bending, we present the micropolar plate field equations as an elliptic system of nine differential equations in terms of the kinematic variables. The system includes an optimal value of the splitting parameter, which is the minimizer of the micropolar plate stress energy. We present the efficient algorithm for the estimation of the optimal value of this parameter and discuss the approximations of stress and couple stress components. The numerical algorithm also includes the method for finding the unique solution of the micropolar plate field equations corresponding to the optimal value of the splitting parameter. We provide the results of the numerical modeling for the plates made of polyurethane foam used in structural insulated panels. The comparison of the numerical values of the vertical deflection for the square plate made of dense polyurethane foam with the analytical solution of the three-dimensional micropolar elasticity confirms the high order of approximation of the three-dimensional (exact) solution. The size effect of micropolar plate theory predicts that plates made of smaller thickness will be more rigid than would be expected on the basis of the Reissner plate theory. We present the numerical results for plates of different shapes, including shapes with rectangular holes, under different loads. [Copyright &y& Elsevier]

The global buckling behaviour of hot-rolled stainless steel channel section beam–columns under combined compression and minor-axis bending moment has been studied based on testing and numerical modelling and reported in this paper. A testing programme was conducted on ten hot-rolled austenitic stainless steel channel section beam–columns, with five buckling towards webs and the other five buckling towards flange tips. This was followed by a numerical modelling programme, in which finite element models were firstly developed and validated against the test results and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions, member effective lengths and loading combinations. The test and numerical results were adopted to assess the current design interaction curves given in the European code and American guide, both of which were found to result in inaccurate and scattered failure load predictions. The inaccuracy of the codified design interaction curves stems from the inaccurate end points (i.e. the member resistances under pure compression and pure bending) and the inappropriate shape. To address these shortcomings, a new design interaction curve was developed firstly through the adoption of more accurate end points and secondly through the derivation of a more proper shape. The proposed design interaction curve was shown to yield accurate and consistent failure load predictions for hot-rolled stainless steel channel section beam–columns. The reliability of the new proposal was also confirmed by means of statistical analyses. • The buckling behaviour of hot-rolled stainless steel channel section beam–columns is studied. • Ten beam–column tests were conducted. • FE models were firstly developed and validated against the test results and then adopted to perform parametric studies. • The codified design interaction curves were assessed, indicating inaccuracy. • A new design interaction curves was proposed, with the accuracy and reliability demonstrated. [ABSTRACT FROM AUTHOR]

In this research, the durability of Carbon Fiber Reinforced Polymer (CFRP) repaired corroded marine pipelines with the bending moment and seawater immersion was studied using experiments. The durability factors were studied, and the attenuation of the repaired structure was broken into the attenuation of CFRP and the interface between the CFRP and the steel. Based on the attenuation law, a numerical damage model of CFRP repaired pipelines was constructed using Finite Element Method (FEM). The mechanical properties of the repaired pipelines after long-term durability conditions were obtained numerically. These properties were almost the same as those for the experimental results. • The durability and attenuation laws of CFRP repaired pipelines were studied. • A numerical damage model of CFRP repaired pipelines was constructed using FEM. • The attenuation laws of repaired pipelines could be accurately obtained using FEM. [ABSTRACT FROM AUTHOR]

Abstract: For the coupled static and dynamic buckling of thin walled beam subjected to various forces, such as axial force, uniform bending moment, and bending moment due to concentrated and distributed lateral forces, the spline finite element method is employed to obtain the dynamic stiffness matrix. Second order effects of the axial force and moment are considered. A doubly symmetric cantilever beam with uniform cross-section is investigated. Extensive static and dynamic interaction diagrams are plotted. The effects of warping rigidity, torsional rigidity, axial tension and compression on moment buckling, moment on axial buckling compression, higher buckling modes are discussed in detail. The spline finite element method is proved to be very efficient for the present problem and many interaction diagrams can be plotted easily. Some new results are presented. The methodology is based on finite element formulation and therefore it can be easily extended to analyze structural frames. [Copyright &y& Elsevier]

Abstract: This paper presents a beam formulation for large displacement analysis of beam-type structures with flexible connections. Within the framework of updated Lagrangian incremental formulation and the nonlinear displacement field of thin-walled cross-sections, which accounts for restrained warping and the second-order displacement terms due to large rotations, the equilibrium equations of a straight beam element are firstly developed. Due to the nonlinear displacement field, the geometric potential of semitangential moment is obtained for both the internal torsion and bending moments, respectively. Material nonlinearity is introduced for an elastic-perfectly plastic material through the plastic hinge formation at finite element ends. To account for the flexible connection behaviour, a special transformation procedure is developed. The numerical algorithm is implemented in a computer programme and its reliability is validated trough several test examples. [Copyright &y& Elsevier]

Abstract: This paper presents a crashworthiness design of regular multi-corner thin-walled columns with different types of cross-sections and different profiles, including straight octagonal columns and curved hexagonal columns. In this paper, the straight octagonal section columns are first optimized, which mainly take axial crash loads during crashes. Next, the curved hexagonal section columns are optimized following the same approach, which are subject to bending moment when impact occurs. During the design optimizations, specific energy absorption (SEA) is set as the design objective, side length of the cross-sections and wall thickness are selected as design variables, and maximum crushing force (P m) is set as the design constraint. Both the objective and constraint are formulated using the response surface method (RSM) based on sets of finite element (FE) results obtained from FE analyses (FEA). After obtaining the optimal designs, parametric studies are performed to investigate the influences of the design variables on the crash performance of such multi-corner thin-walled columns. [Copyright &y& Elsevier]

This work presents an investigation on the compressive strain capacity of resisting buckling on an X80 steel corroded pipeline subjected to a bending moment using nonlinear finite element analysis (FEA) validated by full-scale tests. The modelling results indicate that the existing strain-based assessment method is not suitable for pipelines with deep corrosion and has certain application limitations. Consequently, a new evaluation method based on far-field strain was developed to predict the buckling failure of corroded pipelines subjected to bending loads. The influence of the corrosion shape type, corrosion size (i.e., depth d , length L , and width w), pipe geometry, and internal pressure on the critical buckling strain capacity and critical buckling moment of the pipeline were studied using parameter sensitivity analysis to verify the proposed strain criteria. The results illustrate that the variation trends between the critical buckling strain and the critical buckling moment with each factor were consistent, indicating that the proposed novel strain-based evaluation method is effective and applicable. In addition, the buckling resistance of a pipeline with rectangular corrosion is relatively weaker than that with a semi-spherical corrosion pit or cylindrical grooved corrosion under the same defect size. Further, the critical compressive strain capacity of a corroded pipeline is primarily affected by the depth and width of the corrosion, whereas the effect of the corrosion length is relatively insignificant. Moreover, the critical length and width of the corrosion defect affecting the bending capacity of resisting buckling were determined as L / D t = 20 and w / π D = 0. 5 , respectively. • A novel strain-based assessment method of local buckling of corroded pipelines. • Determined the effect of defect geometry on critical compressive strain capacity. • Determined the critical defect size that affect the pipe buckling strain capacity. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents 20 years of research on failure of sheeting subjected to combined concentrated load and bending moment, performed at Technische Universiteit Eindhoven. The aim of this research is to develop accurate, insight providing design rules using simple mechanical models, based on observed failure modes. The paper summarizes the performed experiments, finite-element simulations, and analytical models. It is concluded that mechanical models may be feasible only for sheeting without stiffeners in web and flanges. For sheeting with stiffeners, the models become so complex that it is not likely that they will lead to simple design rules. [Copyright &y& Elsevier]

Abstract: The problem of buckling of the Euler–Bernoulli and Timoshenko beams is analyzed by the finite element method. Significant improvement in accuracy of the method is obtained by replacing the discontinuous function of the bending moment related to the approximation of the eigenfunction obtained by FEM by a “smoothed” function in the Rayleigh quotient. The smoothed function is obtained by fitting the discontinuous one using the least square technique. [Copyright &y& Elsevier]

Sandwich pipe (SP), composed of two concentrically steel tubes with a strain-hardening cementitious composite (SHCC) filling core, is a new concept designed for oil and gas transportation in deep waters. Bending is a primary loading condition for the SP during the installation process. There is currently a lack of research on SPs' bending capacity, considering the actual interlayer behavior. The extreme adhesion conditions of fully bounded and unbounded layers have been commonly adopted in numerical simulations. This paper aims to study the actual interlayer behavior through push-out and self-stress tests and proposes an SP numerical model with a bond-slip layer, based on the finite element method. The results from experimental tests for bending on a rigid surface to simulate the reeling installation method are correlated with the results from the finite element model, presenting good agreement. A parametric study is then performed to investigate the influence of geometric parameters and the interlayer bond behavior on the ultimate bending strength. • Push-out and self-stress tests to study the actual interlayer behavior of sandwich pipes are presented. • A numerical model with a bond-slip layer for sandwich pipe is proposed. • Full-scale sandwich pipes bending tests are presented. • A correlation study between the experimental and numerical results is performed. • Influence of geometric parameters and initial ovality on the ultimate bending moments of sandwich pipe are analyzed. [ABSTRACT FROM AUTHOR]

A grouted connection (GC) is critical to the transfer of combined axial force and bending moment from an upper tower to a substructure. Meanwhile, the increasing offshore wind turbine capacities and deeper pile foundation locations require robust connection structures. However, it is difficult to completely test the stress in GCs through experiments. So, in this paper, a numerical approach combined with python was adopted to analyze the load transferring mechanism between staggered shear keys mounted. A Parametric (grout thickness, the height-to-spacing ratio of the shear keys, and the length-to-diameter ratio of the tube) study was conducted to determine the effect on the mechanical behavior. In addition, an equation and two coefficients were proposed: the regression function of the contact pressure distribution, the non-uniform coefficient η sk and the amplification coefficient β sk of the shear keys force. Through an analysis of the composition of the flexural capacity, it was found that shear keys accounts for the largest proportion while the contact pressure took the second place. From the study, programming enriches the post-processing of the numerical simulation, which provides researchers a method to research the GCs through complex calculations. And by the analyzing the parameters and introducing related variables, a deeper understanding of the mechanical performance of GCs has been obtained. • This paper takes t g , L / D p and h/s as variables. • Finite element analysis method and numerical integration method are used. • The stress states and the composition of flexural capacity are analyzed. • The non-uniform coefficient η sk and the amplification coefficient β sk are proposed. [ABSTRACT FROM AUTHOR]

For trapezoidal steel sheeting, design codes so far calculate the web crippling strength via curve fitted rules; bending moment failure is predicted by the effective width method or the Direct Strength Method (DSM); and their combination is handled by a curve fitted interaction rule. As the DSM is easy to use, potentially more accurate, and closer to a mechanical description than curve fitted rules, this paper investigates whether it can be used for trapezoidal sheeting, limited here to the first-generation, i.e. without stiffeners. First, an existing set of experiments is presented, in which first-generation sheeting has been subjected to combined web crippling and bending moment via three-point bending tests. In these experiments, web-crippling deformation, beam deflection, and support rotations have been recorded, and failure behaviour has been studied well beyond the ultimate load. These experiments are simulated by the finite element method, and after verification, the simulations are used to record the first Eigenvalue, first yield, and the ultimate load of the experiments. Additionally, each experiment is also modelled as an Interior One Flange (IOF) web crippling test and a pure bending moment test. Finally, the DSM is developed based on the simulation data (not the experimental data), using two approaches. (i) For the interaction approach, only the web crippling strength and the bending moment capacity are predicted by the DSM, using the simulation data from the IOF web crippling tests and pure bending moment tests. Interaction is described by an interaction rule, calibrated to the simulations of the three-point bending tests. (ii) For the explicit approach, the DSM is used to predict the combined load capacity, based on the simulation data from the three-point bending tests. It is concluded that both approaches work, but the interaction approach performs better than the explicit approach. Using Interior Two Flange (ITF) Eigenvalues in combination with IOF yield loads and IOF ultimate loads increased the performance of the IOF web crippling DSM equations, however, it not leads to a further improvement of the interaction approach. • Existing experiments with transient phenomena modelled with FEM. • FE simulations provide DSM data for Eigenvalues, first yield, ultimate load. • Explicit DSM correlates with 0.79 to data, implicit with 0.90 • For interaction DSM, ITF Eigenvalues improve IOF predictions. • Improved IOF predictions do not improve interaction DSM. [ABSTRACT FROM AUTHOR]

This paper proposes a numerical and an approximate analytical method for the in-plane non-linear elastic stability of arches under the multi-pattern distributed load. There are six key parts in this paper. Firstly, the approximate analytical solution for funicular axis of arches subjected to the multi-pattern distributed load is derived from the approximations of linear elastic bending moment and horizontal reaction force in the arch end. Secondly, the numerical solution of the in-plane non-linear elastic equilibrium equation is solved by using the shooting method and the bisection method simultaneously. Thirdly, the approximate analytical solutions for the in-plane non-linear elastic equilibrium are derived according to the approximate analytical solution for funicular arch axis obtained from the first part, the simplified strain-displacement expression in Cartesian coordinate system and the virtual work principle. Fourthly, a key parameter is proposed to transform the approximate analytical solutions into the corresponding equations of catenary and parabolic arches. Fifthly, the in-plane non-linear elastic symmetric and asymmetric buckling of arches under the multi-pattern distributed load is derived analytically. Lastly, the in-plane non-linear elastic buckling behaviors of arches subjected to multi-pattern distributed load are deduced based on the obtained analytical solutions. The multi-pattern distributed load with the uniformly distributed load along the span and the uniformly distributed load along the arch is selected as example to verify the proposed method. Comparisons with numerical solutions demonstrate that the proposed approximate analytical solutions for the funicular arch axis and linear elastic horizontal reaction force agree well with the results of Runge-Kutta method and the proposed approximate buckling predictions have sufficient accuracy compared with the results of finite element method in different rise-to-span ratios, relative slenderness and arch axis parameters. • Approximate closed-form solution for funicular axis was proposed. • Numerical solution was obtained by shooting method and bisection method. • Analytical solutions of in-plane nonlinear elastic stability were derived. • Analytical solutions can be transformed into equations of catenary and parabolic arches. • Critical slenderness were derived to distinguish different buckling behaviors. [ABSTRACT FROM AUTHOR]

The current slenderness limits are significantly different in international design codes for cold-formed Circular Hollow Sections (CHS) under pure bending. This paper aims to use the Finite Element (FE) method to understand the behaviour of cold-formed CHS under pure bending and to propose new design rules. The model is calibrated by comparing its predicted load-deflection curves with previously published experimental data. In total, 21 specimens were modelled with diameter-to-thickness ratios ranging from 13 to 122. The current slenderness limits in the present international steel specifications were examined using the FE model and their suitability for cold-formed CHS is discussed. The effect of section slenderness on rotation capacity has been examined where the predicted variation of rotation capacity against section slenderness has been compared to the experimental results. A new equation for the amount of initial geometrical imperfection as a function of section slenderness has been developed and proposed for design purposes. The ovalisation deformation ratio and the critical strain at local buckling were determined and compared for compact, non-compact and slender sections. The progressive bending deformations of CHS at 10 critical steps have been presented and compared for the three cross sectional types, in particular at the maximum moment and bending rotation. In general, a good agreement has been obtained between the predicted strengths and ductilities using the current FE models and those of the experimental data of cold-formed CHS. • Using finite element method to determine the slenderness limit of cold-formed steel tubes and compared to the previous experimental results. • The effect of geometrical imperfections on the deformation cold-formed CHS has been examined. • The rotation capacity has been presented for CHS. • The ovalisation of compact, non-compact and slender section has been analysed. • The buckling mechanism has been analysed by using strain analysis, the critical strain at maximum moment has been determined and compared to the theoretical results. [ABSTRACT FROM AUTHOR]