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Double-skin tubular columns (DSTCs) represent one of the most novel column systems for future structures, such as bridges, flyovers, high-rise buildings, and towers, due to their higher axial compressive strength and improved ductility characteristics. The enhanced confinement of the concrete is the primary reason for the improved axial compressive strength and superior ductility in DSTCs. However, the steel in DSTCs is localized to the outer and inner layers only, without any connecting element in-between inner and outer steel tubes. As a result, a significant sudden drop in the load-carrying capacity has been observed in DSTCs as soon as the outer or inner steel tube fails. However, the failure in inner and outer steel tubes can be significantly delayed or prevented if they are connected through stiffeners. The present study, through an extensive experimental investigation, focused on effectively strengthening and connecting both the outer and inner tubes in DSTCs by adopting various stiffener schemes. Additionally, the stiffeners split the concrete core into discrete concrete cells. Accordingly, in the current study, these columns have been referred to as multicell double-skin tubular columns (MC-DSTCs). From the experimental observations, axial compressive strengths in MC-DSTCs were higher than that in the unstiffened DSTCs by up to 62%. Further, MC-DSTCs exhibited larger axial deformations compared with the unstiffened DSTCs, improving their ductility index by up to 253%. The increased axial strengths and ductility in MC-DSTCs have been attributed to delayed and controlled failure of steel and concrete components because of the improved participation of inner and outer tubes through stiffener connections. Finally, a design model has been proposed based on the concept of concrete confinement in MC-DSTCs to accurately predict their axial compressive strength, which has been verified through a regression analysis. A good correlation (with R2=0.986) between the predicted and experimental axial compressive strengths of MC-DSTC was observed. [ABSTRACT FROM AUTHOR]

This research introduces a novel gusset plate damper designed to safeguard structures from intense seismic activity and enhance the performance of X-braced frames. The damper includes a grooved plate with multiple parallel steel strips, and cross braces segmented into four parts by the central grooved plate. Both sides of each brace segment, a set of strips is embedded within the gusset plate, oriented perpendicular to their corresponding brace axis. The X-braced frames equipped with grooved gusset plate damper (GGPD) were subjected to cyclic loading both experimentally and numerically. The experimental results demonstrated that the proposed system exhibits robust seismic performance. Employing ABAQUS, the calibration results demonstrated excellent agreement between the experimental and numerical outcomes, affirming the accuracy of the finite element method in predicting the cyclic behavior and fracturing patterns of this innovative system. Additionally, the study delved into the local buckling and the necessity of incorporating stiffeners for the grooved plate damper along their edges, evaluating their impact on the main characteristics of the new damper. The findings revealed that when appropriately reinforced at its edges, the proposed damper demonstrates excellent behavior and stable hysteretic curves. Moreover, decreasing the width-to-thickness ratios of steel stiffeners in the GGPD resulted in wider hysteresis loops. Findings indicated that a width-to-thickness ratio of 7 yields favorable outcomes for design parameters, including lateral elastic stiffness and ultimate strength. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiaotong University (Science) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wrinkling is a typical failure mode of sandwich structures with thin skins, where the bending deformation of face skins occurs simultaneously in conjunction with transverse stretching deformation of core layer. To analyze the three-dimensional (3D) deformation of wrinkling, a model is required to possess a capability describing completely different deformations at each ply. Therefore, by utilizing the Chebyshev polynomial at each layer of sandwich panels, this paper focuses on proposing a higher-order model to individually illustrate deformations of the skins and the core. By means of the proposed model, a refined triangular element has been constructed. By analyzing the stability of a sandwich plate without stiffeners, the finite-element formulation has been verified by comparing it to the quasi-3D elasticity solutions. In addition, it is anticipated that wrinkling failure can be effectively restrained by designing the stiffener layout. To this end, the influence of stiffener layouts on wrinkling behaviors of sandwich plates has been investigated in detail, and it is found that the capability of resisting the wrinkling deformation can be obviously improved by designing reasonable stiffener layouts. Moreover, the translation between buckling and wrinkling behaviors of sandwich panels with different stiffeners has been also explored, which can help to better understand wrinkling deformation mechanism. In summary, the proposed model can be used to design a reasonable arrangement of stiffeners to resist the wrinkling failure of sandwich panels. [ABSTRACT FROM AUTHOR]

Stiffened structures have great potential for improvingmechanical performance, and the study of their stability is of great interest. In this paper, the optimization of the critical buckling load factor for curved grid stiffeners is solved by using the level set based density method, where the shape and cross section (including thickness and width) of the stiffeners can be optimized simultaneously. The grid stiffeners are a combination ofmany single stiffenerswhich are projected by the corresponding level set functions. The thickness and width of each stiffener are designed to be independent variables in the projection applied to each level set function. Besides, the path of each single stiffener is described by the zero iso-contour of the level set function. All the single stiffeners are combined together by using the p-norm method to obtain the stiffener grid. The proposed method is validated by several numerical examples to optimize the critical buckling load factor. [ABSTRACT FROM AUTHOR]

An ordinary double steel plate–concrete composite wall (ODSC wall) is composed of core concrete, the faceplates, and shear connectors such as studs, etc. Based on an ODSC wall, a new type of stiffened double steel plate–concrete composite wall (SDSC wall) is conceived by incorporating additional stiffeners and tie plates on the internal surface, which aims to improve the local stability of the faceplates. In the authors' previous study, a series of axial compression tests were conducted on the SDSC walls. The SDSC walls in the test showed better mechanical performance, as the presence of stiffeners changed the buckling deformation mode and significantly improved the corresponding local buckling stress and ultimate strength. In this paper, a comprehensive summary of the prior research on SDSC walls is provided, and the effect of the constructive parameters on the local stability is discussed. The results reveal that the modified formula of the critical stress can degrade to the Euler formula when the stiffener-to-stud spacing ratio (i.e., a/B ratio) approaches infinity. What is more, the analysis model is also applicable for DSC walls with enclosed side plates, and the proposed formula can predict the buckling stress of the SDSC walls with different a/B ratios. In addition, according to the analysis of the numerical simulation, a design approach for SDSC walls to prevent local buckling is provided, which is applicable in practical engineering applications. [ABSTRACT FROM AUTHOR]

The I-shaped beam to circular column connections can be constructed by curved cutting of the beam flanges or by installing external diaphragms around the column, which cause both economic and practical difficulties. A practical method proposed for construction of these connections consists of welding a link channel to the circular column and welding the beam to the link channel. As this method is new, the effect of link channel dimensions, I-shaped beam section dimensions, circular column dimensions and the link channel stiffeners on the connection behavior is not known well. Accordingly, this paper presents a FE investigation on the cyclic behavior of I-shaped beam to circular column moment connections with link channel. The main novelty of the research is the parametric evaluation of the affecting parameters, considering the stiffness and strength degradation from ultra-low-cycle fatigue, which is made possible by including ductile damage for metallic materials in ABAQUS software. For this purpose, first, the parameters of the damage model are calibrated by comparing the numerical results with the laboratory data, and then, the connection models are analyzed under a displacement-control quasi-static cyclic loading. Based on the results, the thickness of the link channel plate has the most significant effect on the overall behavior of the connection compared to other link parameters. It is also observed that the link channel stiffeners increase overall stiffness and strength of the connection. However, they cause extension of yielding towards the beam to link connection, and cause rapid growth of plastic strain in this area.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The I-shaped beam to circular column connections can be constructed by curved cutting of the beam flanges or by installing external diaphragms around the column, which cause both economic and practical difficulties. A practical method proposed for construction of these connections consists of welding a link channel to the circular column and welding the beam to the link channel. As this method is new, the effect of link channel dimensions, I-shaped beam section dimensions, circular column dimensions and the link channel stiffeners on the connection behavior is not known well. Accordingly, this paper presents a FE investigation on the cyclic behavior of I-shaped beam to circular column moment connections with link channel. The main novelty of the research is the parametric evaluation of the affecting parameters, considering the stiffness and strength degradation from ultra-low-cycle fatigue, which is made possible by including ductile damage for metallic materials in ABAQUS software. For this purpose, first, the parameters of the damage model are calibrated by comparing the numerical results with the laboratory data, and then, the connection models are analyzed under a displacement-control quasi-static cyclic loading. Based on the results, the thickness of the link channel plate has the most significant effect on the overall behavior of the connection compared to other link parameters. It is also observed that the link channel stiffeners increase overall stiffness and strength of the connection. However, they cause extension of yielding towards the beam to link connection, and cause rapid growth of plastic strain in this area. [ABSTRACT FROM AUTHOR]

Defects/imperfections can occur during manufacturing, assembly, welding, and other processes, which can reduce the critical buckling load. However, the axial buckling load is beyond the scope of this work, and there are many studies on the stiffening effect of longitudinal dents. This concept combined the idea of the dent-to-stiffener evaluation concept for thin-walled steel cylinders. This study aims to transform the dents into artificial dents for a stiffening effect on the buckling phenomena. For this purpose, 37 thin-walled steel cylinder models, including the perfect model, were designed for varying dent shapes, dent widths, dent depths, dent lengths, and dent angles. The study also contributed to the effect of dent parameters on the critical buckling load of thin-walled steel cylinders. In particular, increasing the initial buckling will motivate the industry to convert dents into stiffeners with small artificial touches to enhance the longevity of the structure. The results showed that the introduction of certain artificial dents can significantly increase the critical buckling load of cylinders, thus improving their resistance against buckling, which has significant implications for various industries that use thin-walled steel cylinders in their structures. The proposed simulations for transforming dents into artificial stiffeners can be a valuable tool for enhancing the longevity and safety of thin-walled steel cylinders and other structures.

[Introduction] The topside module of an offshore step-up station usually has numerous tube-I section joints with complicated structure, which cannot be checked by general structural design software. Hence, a feasible checking design method and refinement of stiffener schemes are in need. [Method] A simplified model based on typical tube-I section joints of the topside module of an offshore step-up station was established, and five stiffener schemes were designed for it. Based on the finite element software simulation method, three typical displacement loading conditions, i.e., axial compression displacement, in-plane rotation, and out-of-plane rotation, were applied to analyze the plastic zone development and failure modes of the five stiffener schemes. For the longitudinal stiffener scheme selected, the effective stress section of the stiffener was assumed based on existing codes, and a simplified calculation method for stiffener stress check under complicated loads was proposed. The results were examined using the finite element method. [Result] The results show that the unstiffened tube-I section joint cannot satisfy the design principle of "strong joint and weak member", and it is necessary to take stiffening measures such as stiffeners. The longitudinal stiffener scheme performs better in terms of bearing capacity and economical efficiency. Longitudinal stiffeners are essential for the shearing capacity of beam webs, while the transverse stiffeners cannot enhance shearing capacity. Finite element analysis indicates that the stress distribution is consistent with the assumption of the simplified calculation method, and the simplified calculation method predicts higher stress levels than the finite element results, which means the proposed simplified calculation method is feasible and safer. [Conclusion] The longitudinal stiffener scheme is a better stiffening scheme for the joint. The proposed simplified calculation method can be adopted to check the longitudinal stiffener scheme efficiently.

Buckling analyses of orthogonally stiffened functionally graded graphene platelet reinforced composite plate with circular cutout supporting on Winkler elastic foundation is conducted according to the third order shear deformation plate theory and the finite element method to achieve the desired solutions. Material properties of the composite plate are evaluated using Rule of mixture and Halpin-Tsai approach. Graphene platelet reinforcements and Poly methyl methacrylate matrix are considered as the two components of the composite media. The material of the stiffeners is selected the same as that of the polymer matrix. In one efficient case, adding a set of stiffeners increased the critical buckling load by 41.8 % with only a 10.3 % increase in weight of the structure. Influence of broad range of factors such as GPLs nanofillers distribution pattern and weight fraction, Winkler-type elastic foundation, uniaxial and biaxial normal and shear loads, plate thickness and aspect ratio, width, height and number of longitudinal and transverse stiffeners are reported in several tabular and graphical data in detail.

A shape and generalized topology optimization method based on the level set-based density method is proposed to design the curved grid stiffeners. The overall layout of the stiffeners is described by combining many single stiffeners, and each single stiffener is described by a level set function parameterized by using the compactly supported radial basis functions (CS-RBFs). The curvilinear path of each stiffener is described by the zero iso-contour of each level set function, and the width of each stiffener is described by applying an interval projection to each level set function. The combination operation that is similar to the Boolean operation "union" is achieved by using the p-norm method. The expansion coefficients of CS-RBFs are taken as part of the design variables of the optimization, and they are responsible for changing the shape of curved stiffeners. A topology design variable is assigned to each single stiffener, and it is responsible for changing the existence of single stiffeners. The proposed method is validated through several numerical examples, and the results demonstrate that the shape and topology of stiffeners can be effectively changed during the optimization. [ABSTRACT FROM AUTHOR]

As the main structural component of aircraft skin, aluminum alloy integral panel is characterized by smooth aerodynamic configuration, light weight, high specific strength and stiffness, short fabrication cycle and so on. It is imperative to develop effective forming technology to manufacture integral panel with high configuration and dimension accuracy from flat or profiled sheet metal. Bend forming has advantages over other processes. Significant research work has been carried out in recent decades. This literature covers a review of the research and development of bend forming of aluminum alloy integral panels regarding principles, applications, forming processes and defects like buckling and fracture based on experiments and finite element simulations. Future research directions are also pointed out. [ABSTRACT FROM AUTHOR]

The use of aluminum in civil engineering applications has increased significantly over the past decades. Aluminum is a durable, lightweight, and recyclable material that can provide alternative structural solutions for building power transmission towers. In order to achieve this objective, it is necessary to develop structural members that take advantage of specific properties of the material, such as low density, high strength, resistance to corrosion, and the geometric flexibility that aluminum extrusions provide to design robust and easy-to-assemble structures. This paper presents a section optimization study of an existing medium-voltage steel 120--160 kV lattice tower owned by Hydro-Québec, considering the use of various extruded aluminum sections. The proposed optimized aluminum sections are compared with the steel sections of the existing tower. The study's main objective is to optimize the tower's aluminum sections. A SAP2000 structural finite element stick model of the tower coupled to a Matlab optimization routine is used to optimize the aluminum sections. ASCE10-15 and CSA-S157-17R22 standards are used to impose the design constraints for selecting the optimized aluminum square and octagonal hollow sections, with and without stiffeners. This study proposes optimized section shapes suitable for constructing aluminum lattice transmission towers. The study reveals that the proposed aluminum tower prototype is twice as light as its steel counterpart. The aluminum members' price is also very competitive compared to steel. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to study the nonlinear buckling behavior of carbon nanotube-reinforced (CNT-reinforced) cylindrical shells with the CNT-reinforced stiffeners under external pressure taking into account the effects of uniform temperature rise. A new design of stiffener system is proposed for CNT-reinforced cylindrical shells with five cases of the CNT distribution law for shell and stiffeners. A modified homogenization technique for CNT-reinforced stiffeners is developed and presented. Based on the Donnell shell theory and the von Kármán nonlinearity assumption, the Galerkin method is applied with the solution of deflection approximated in threeterm form, the critical buckling, and load-deflection postbuckling curves can be achieved in explicit expressions. Effects of the CNT-reinforced stiffeners, the thermal temperature, and the CNT-reinforced parameters on the external pressure buckling responses are numerically indicated and validated. [ABSTRACT FROM AUTHOR]

In this study, a new algorithm for the nonlinear buckling behavior of the stiffened functionally graded graphene-reinforced composite laminated (FG-GRCL) toroidal shell segments in the thermal environment surrounded by the elastic foundation and subjected to torsional load is introduced. The FG-GRCL shell segment is stiffened by the FG-GRCL ring and/or stringer stiffener system. Based on the Donnell shell theory with the Stein and McElman approximation, considering the von Karman geometrical nonlinearity and the anisotropic smeared stiffener technique for FG-GRCL stiffeners, the formulations to investigate the critical buckling load and postbuckling torsional load-deflection curves are determined. A new algorithm is fully developed by adding the effect of circumferential stress into the stress function. The significant effects of temperature, stiffener system, geometrical parameters, and elastic foundation are considered and studied in detail. [ABSTRACT FROM AUTHOR]

An ordinary double steel plate–concrete composite wall (ODSC wall) is composed of core concrete, the faceplates, and shear connectors such as studs, etc. Based on an ODSC wall, a new type of stiffened double steel plate–concrete composite wall (SDSC wall) is conceived by incorporating additional stiffeners and tie plates on the internal surface, which aims to improve the local stability of the faceplates. In the authors’ previous study, a series of axial compression tests were conducted on the SDSC walls. The SDSC walls in the test showed better mechanical performance, as the presence of stiffeners changed the buckling deformation mode and significantly improved the corresponding local buckling stress and ultimate strength. In this paper, a comprehensive summary of the prior research on SDSC walls is provided, and the effect of the constructive parameters on the local stability is discussed. The results reveal that the modified formula of the critical stress can degrade to the Euler formula when the stiffener-to-stud spacing ratio (i.e., a/B ratio) approaches infinity. What is more, the analysis model is also applicable for DSC walls with enclosed side plates, and the proposed formula can predict the buckling stress of the SDSC walls with different a/B ratios. In addition, according to the analysis of the numerical simulation, a design approach for SDSC walls to prevent local buckling is provided, which is applicable in practical engineering applications.

The eccentric RHS (rectangular hollow sections) joint offers improved mechanical properties and better space utilization. Its use in frame structures has gained significant attention. Currently, the initial rotational stiffness of RHS joints, the simplified finite element analysis method of eccentric RHS joints, and the influence of the spatial effect of RHS joints are still unknown. The purpose of this research is to establish a calculation formula for the initial rotational stiffness of eccentric RHS joints, study the influence of the spatial effect under complex stress conditions, and propose a mathematical model that can be used to simplify the analysis of eccentric RHS joints. The research findings indicate that the web plate's deformation stiffness primarily influences the joints' initial rotational stiffness. This increases with a higher beam-to-column depth-to-width ratio, beam-to-column thickness ratio, and column width-to-thickness ratio. The form of the moment distribution in the joint changes, and begins to have a significant effect on the rotational stiffness when the beam-to-column flange width ratio reaches and exceeds 0.7. The stiffeners have a direct additive effect on the joint stiffness. The influence of adjacent beams on the joint is minimal, and the spatial effect of the joint can be disregarded. Furthermore, the finite element analysis confirmed the accuracy of the power function model in accurately simulating the static load behavior of the joint, particularly the bending moment–angle relationship. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to investigate the postbuckling and buckling of functionally graded graphene-reinforced composite (FG-GRC) laminated cylindrical shells strengthened by stiffeners under axial compression with the uniform temperature change effect. The stiffener design option for FG-GRC cylindrical shells under axial compression is presented and a suitably smeared stiffener technique for GRC laminated stiffener system is developed. Basing on the von Kármán Donnell shell theory, the Galerkin's procedure, and the three-term solution of deflection, the explicit forms of critical buckling and expression of load-deflection postbuckling curves relation are obtained. Effects of the GRC laminated stiffeners, the environment temperature, the graphene-reinforced parameters on the compressed buckling behavior are validated. [ABSTRACT FROM AUTHOR]

Stiffeners reinforcing silo's wall made from corrugated sheets are main structural elements sustaining meridional forces evoked by shear forces, source of which is friction of the material stored inside silo. Buckling resistance of stiffeners can be assessed by the method recommended in PN-EN 1993-4-1:2009/A1-2017-08E and in the draft of the Eurocode prEN 1993-4-1:2022. This method consists in determination of stiffener's resistance treated as a column resting on elastic substrate which is the susceptible wall of the silo. It means that it was assumed that the stiffness of the sheeting resists buckling displacements normal to the silo wall. The procedure recommended in mentioned Eurocodes requires determination of stiffness coefficient K on the basis of the flexibility of an equivalent arch of the span equal to the double circumferential separation between adjacent stiffeners. The stiffness coefficient K was derived in the paper using classical mechanics methods and its value was compared to the one given in mentioned Eurocodes. Careful comparative analyses resulted in the identification of errors in one of the Eurocode formulae, which could result in a significant misestimation of the buckling resistance of the stiffeners. The proposed amendment led to a full correspondence between the final formula for K derived in the paper and that proposed in the referenced Eurocodes. The errors found were reported to the coordinator of the CEN working group updating EN 1993-4-1. [ABSTRACT FROM AUTHOR]

Copyright of Southern Energy Construction is the property of Southern Energy Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nowadays, Engineers are actively seeking to improve construction materials and properties. In that, the usage of the castellated beam is become very popular due to its advantageous structural applications. In existing researches are described the presence of large openings in the web that creates different mechanical behaviour compared to strong web beams. While it does not deal with the behaviour of the shear strength performances of the castellated beam, which is due to the limitations on maximum allowable deflections by welding stiffeners. Therefore, this research analysis intends on augmentation of shear strength in castellated beam. Hence, the work incorporates shear stiffeners along with the web opening of the web adjacent to the shear region. Consequently, it leads to increase the shear strength of the castellated beam chassis with regard to cyclic loading and also efficiently reduce the deflection. In order to improve the behaviour of the castellated chassis beam, the study investigation providing the diagonal stiffeners on the web opening with the shear zone and thus compared to without stiffeners and vertical stiffeners. At last castellated beam and deflection effects with increased depth of web openings are analysed with the aid of Finite Element Analysis software ANSYS 16.0. From the experimental findings, the paper achieves the maximum deflection of forwarding and reverse cyclic loading is 7.7mm and 7.29mm respectively. This demonstrates the efficacy and the confines of the assorted studies of stiffening solutions. [ABSTRACT FROM AUTHOR]

In this paper, a multi-cell design method with built-in stiffeners is proposed to improve the crashworthiness of metal circular tubes. In the study, multi-cell circular tubes with three different stiffeners (Line, Waved, Polyline) were subjected to compression tests under quasi-static load. The finite element model of the metal circular tube was validated by ABAQUS/EXPLICIT, and the geometry of the stiffener was designed on this basis. The results showed that the energy absorption of the multi-cell tube was significantly better than that of the initial tube. Further, 'Waved' and 'Polyline' are more conducive to improving the crashworthiness of the multi-cell tube from the geometric design of the stiffeners. Through the analysis of load-displacement responses and crashworthiness indexs, it was found that the more the number of 'Waved' or 'Polyline' (from 2 to 8), the better the energy absorption of the multi-cell tubes and the smaller the load fluctuation. In addition the effect of the number of stiffeners on energy absorption was also revealed. [ABSTRACT FROM AUTHOR]

This study presents finite element analysis of double split tee (DST) connections with high-strength steel bolts and coupled split tee sections, to evaluate various cyclic response parameters and elements. The investigation included quantifying connection behavior and hysteretic response, damage indexes, and failure modes. Over 40 specimens were simulated in ABAQUS under cyclic loading, including shape memory alloy (SMA)-built specimens. In the post-analysis phase, the T-stub thickness, the T-stub yield strength, the bolt preload and bolt number, and the stiffener type and stiffener material for the most significant parts of the DST connection were calculated. Simulation results showed that a lower ultimate moment yielded fewer needed stem bolts. The energy dissipation (ED) capacity increased as the horizontal distance between the stem bolts decreased. Additionally, increasing the strength of the bolt and T-stub by 15% resulted in a 3.86% increase in residual displacement (RD) for the bolt and a 1.73% decrease in residual displacement for the T-stub. T-stub stiffeners enhanced ED capacity by 31.7%. SMA materials were vulnerable to mode 1 failure when used in T-stubs, bolts, or stiffeners. However, the use of SMA increased the rate of energy dissipation. Adding stiffeners to the T-stubs altered the failure indexes and improved the pattern of failure modes. In addition, stiffeners decreased the rupture and pressure indexes. As a result, the failure index of a T-stub shifted from brittle failure to ductile failure.

T-stubs are important components in the application of the component method; hence it is crucial to clarify the T-stub mechanism for the analysis of the mechanical properties of steel joints. In this study, the mechanical behavior of T-stubs was assessed via 6 static tests and 18 finite element analysis models. The influences of flange thickness, bolt spacing, bolt diameter, and stiffener rib on initial stiffness, ultimate bearing capacity, and bolt force of T-stubs were analyzed. Furthermore, the development process and relations of the T-stub bolt force with and without stiffeners were analyzed. The results show that an effective stiffener arrangement can reduce the bending moment and prying force to a certain degree; however, offsetting the bending moment and prying force entirely is difficult. Furthermore, the influence of bending moment and prying force on the bearing capacity should be considered in the design. [ABSTRACT FROM AUTHOR]

This study presents finite element analysis of double split tee (DST) connections with high-strength steel bolts and coupled split tee sections, to evaluate various cyclic response parameters and elements. The investigation included quantifying connection behavior and hysteretic response, damage indexes, and failure modes. Over 40 specimens were simulated in ABAQUS under cyclic loading, including shape memory alloy (SMA)-built specimens. In the post-analysis phase, the T-stub thickness, the T-stub yield strength, the bolt preload and bolt number, and the stiffener type and stiffener material for the most significant parts of the DST connection were calculated. Simulation results showed that a lower ultimate moment yielded fewer needed stem bolts. The energy dissipation (ED) capacity increased as the horizontal distance between the stem bolts decreased. Additionally, increasing the strength of the bolt and T-stub by 15% resulted in a 3.86% increase in residual displacement (RD) for the bolt and a 1.73% decrease in residual displacement for the T-stub. T-stub stiffeners enhanced ED capacity by 31.7%. SMA materials were vulnerable to mode 1 failure when used in T-stubs, bolts, or stiffeners. However, the use of SMA increased the rate of energy dissipation. Adding stiffeners to the T-stubs altered the failure indexes and improved the pattern of failure modes. In addition, stiffeners decreased the rupture and pressure indexes. As a result, the failure index of a T-stub shifted from brittle failure to ductile failure. [ABSTRACT FROM AUTHOR]

In the past years, special attention has been drawn to the explosion and its effect on various structures, especially thin-walled structures. One of the most effective factors for changing the behavior of such structures is thermal and shock loads caused by explosions. In the meantime, considering the geometric nature of the shells, which have a wide surface and thinness, as well as their wide application in various industries such as missile industries, nuclear industries, shipbuilding and silo construction, it is necessary to investigate the effect of these loads on the nonlinear dynamic behavior of the shells. However, knowing the large deformation of such structures under these loads, practical and cost-effective solutions such as strengthening the shells using hardeners are recommended. On the other hand, implementation problems and the possibility of creating an opening in the shells lead to a change in their behavior. In this thesis, using the ABAQUS finite element software, the elastoplastic response of single-curvature steel shells with and without opening and stiffener against blast loads is investigated. For this purpose, the effect of the supporting conditions, the thickness of the single curved shell, the mass of the TNT material, the distance from the place of explosion to the centre of the shell, the curvature of the shell, and the effect of opening and stiffener have been investigated. The results indicated better performance of the shell with the bearing support condition compared to other support conditions. Increasing the curvature of the shell initially led to an increase in displacement and then a decreasing trend. Results of the research indicate that the creation of circular and square openings has reduced the stiffness of the shell, followed by an increase in displacement, and the increase in displacement for square openings is more than circular openings. [ABSTRACT FROM AUTHOR]

This article examines the mechanical behavior of steel endplate beam-to-column joints with different stiffeners under bending moment. This type of connection is commonly used in steel frameworks to transmit loads from beams to columns. In frame design procedures, engineers tend to consider beam-to-column joints either ideally pinned or fully rigid. The present study aims to show their semi-rigid behavior by analyzing the characteristics of the relation between the bending moment and the rotation of the studied connection. The analysis is based on the development of a finite element model considering the material, geometrical and contact nonlinearities between the components. Three types of stiffeners are introduced in different positions to investigate their effect on the global behavior of the joints. The moment rotation curve is defined together with the procedure of determination of the initial rotational stiffness, the elastic and plastic moments of the connection. The numerical model is validated by comparing the moment rotation curves with those of similar studies available in the literature and also with the design approach proposed by Eurocode 3. The obtained results have showed that the use of stiffeners in the column web or on the endplate increases significantly the rigidity of the studied connection. The failure modes have been discussed in detail for each configuration with respect to the rotation capacity and the initial stiffness. Finally, the model has been used to show the influence of three bolts classes on the ultimate load of the joints and the deformation of the endplate and bolts at failure. [ABSTRACT FROM AUTHOR]

The detached double-shell dome comprises the outer shell, inner shell, drum, and usually stiffeners. This article closely examines a kind of stiffener, called 'khashkhāshī ,' within two main discussions. (I) By comparing various examples, eight cases representative of all the khashkhāshī types are selected and studied morphologically to introduce a grounded definition for khashkhāshī , encompassing twelve types assorted in three distinct structural forms. (II) By implementing a base model with variations of khashkhāshī , their different structural effects on the overall structural behaviour of the dome are analyzed using linear Finite-Element modeling subject to dead and seismic loads. Although beneficial in redirecting the force flow and decreasing the stress and span increase at the expense of added weight, khashkhāshī might cause localized inefficiencies in some cases. The obtained results are solely for a better understanding of the behaviour of the khashkhāshī , and shall not be directly used for studying individual cases. [ABSTRACT FROM AUTHOR]

Strengthening-by-stiffening (SBS) is a technique for enhancing the shear performance of buckling-prone webs of steel beams by bonding glass fiber–reinforced polymer (GFRP) stiffeners. This paper focuses on changes in load capacity, ductility, and mode of failure of SBS under cyclic loading and after exposure to weathering conditions for 1 year. First, weathering effects on mechanical properties of the adhesive used in bonding the GFRP stiffeners are presented. The ductility of the epoxy was significantly reduced; however, the ultimate stress increased by about 68% over the ultimate stress of the nonweathered coupons. Furthermore, weathering led to the formation of a thin film of rust that propagated around the edges of the bonding adhesive for the full-scale beams. Consequently, the ultimate load capacity of the weathered beam dropped about 11% after 1 year of environmental exposure. Cyclic loading, however, resulted in negligible change in the ultimate load capacity. For all tested beams, the ductile adhesive used in bonding the GFRP stiffeners prevented a sudden drop in load capacity due to debonding of the GFRP stiffener in all tests. [ABSTRACT FROM AUTHOR]

In this paper, hierarchical studies based on both analytical and computational approaches have been employed to validate and improve current structural designs of mud holding tanks for hydraulic fracturing in petroleum industries. Through detailed comparisons at different levels of approximations for both real world complex structural design problem and a simplified stiffened plate with extreme geometrical aspect ratios, proper design procedures have been reiterated and validated. It is highly recommended that low-dimensional structures with emphasis on classical mechanics principles should be considered before full-fledged three-dimensional computational analyses. Both Castigliano’s Theorems and Galerkin methods are utilized along with simulation packages such as ADINA and Solidworks. The hierarchical approximation procedures reemphasize important subjects such as planes and shells, strength of materials, structural mechanics, asymptotic and perturbation analysis no longer required in some engineering programs, yet often necessary for the study of complex three-dimensional structural systems.

High-frequency organic dielectric substrate materials have been widely applied in the fabrication of FCBGA (Flip Chip Ball Grid Array) substrates due to their excellent characteristics of high-speed signal transmission. However, their higher coefficient of thermal expansion (CTE) causes the CTE mismatch between the chip and substrate to increase. High-temperature heating during the reflow soldering process intensifies the thermal mismatch within packaging structure, causing severe warping of the substrate, thereby reducing the yield and subsequent reliability. This study adopted a flatness analyzer and scanning electron microscope (SEM) to characterize the package deformation and micromorphology, and found that the substrate warped after reflow soldering, which caused defects such as chip cracks and micro-bump delamination. A fine finite element simulation model was constructed based on the structure of the experimental sample, and the structure deformation during the soldering process was simulated. An accurate finite element simulation model was constructed based on the structure of the experimental sample to simulate the deformation process of substrate during reflow. Research results show that the constraint of the chip on the substrate during the soldering process is the main factor affecting the thermal deformation mechanism, and the deformation can be suppressed by adding stiffener. This research benefits to the design of FCBGA high-density packaging. • A fine model on the deformation behavior of high-density FCBGA packaging structure was built. • Substrate warpage leads to defects such as crack and delamination in the package during reflow. • The deformation mechanism of substrate during reflow was analyzed. • Adding stiffener improves the rigidity of the substrate and suppresses its warpage. [ABSTRACT FROM AUTHOR]

The investigation aimed to reveal the disparities in the damage sustained by unstiffened and U-shaped stiffened steel plates under blast loads induced by cuboid and cylindrical explosives. A Finite Element Model (FEM) with S-ALE mesh established using LS-DYNA was employed for the analysis. The numerical model was validated against field blast test results before being utilized for further analysis. Two configurations (Arrangement-1 and Arrangement-2) of the cuboid and cylinder explosives were examined. While the displacement responses and damages of unstiffened and stiffened steel plates subjected to cuboid and cylinder explosives with Arrangement-1 induced blast loads were similar, notable differences were observed when the explosives were arranged in Arrangement-2. To quantify the disparities of cuboid and cylinder explosives with Arrangement-2, influential factors such as TNT mass (m TNT), maximum incident angle (α max), number of stiffeners (n), steel plate thickness (t d), and stiffener thickness (t u) were analyzed. The dimensionless energy absorption index χ (the ratio of energy absorbed by steel plates exposed to cuboidal and cylindrical explosives versus spherical explosives) was utilized to evaluate the impact of these parameters. Through parameter analysis, it was found that α max and n had a significant impact on χ. χ decreased notably with an increase in α max , while an increase in n caused χ to show an increasing trend. The m TNT had a minor influence when ι exceeds 4 under local explosion conditions. Although the χ slightly decreased as the m TNT increased, this influence was not notable. Additionally, the impact of t d and t u on χ can be almost ignored. Curve fitting was then employed to describe the relationship between χ and the influences of α max and n. The results indicated that χ (for both cuboid and cylinder explosive detonation) exhibited linear relationships with the logarithm of the explosive height to width (diameter) ratio (log (ι)). The impacts of α max and n were also quantified through curve fitting. This study also presented an illustrative case to demonstrate the calculation of χ cu (χ for cuboid explosive) and χ cy (χ for cylinder explosive), with the difference between cuboid and cylinder explosive-induced damages of the steel plates expressed as the proportion of χ cu and χ cy (Γ). This investigation provided insights into the disparities in damages of steel plates induced by cuboid, cylinder, and sphere explosive detonation, proposing a method to quantify these differences. • The damage differences in steel plate damage induced by two arrangements of cuboid and cylinder explosives were studied. • The factors influenced the dimentionless energy absorption of steel plates were analyzed; • The relationship between the dimentionless energy absorption of steel plates and the explosive dimension was established; • A method to quantify the differences in cuboid and cylinder charges induced steel plate damage was proposed. [ABSTRACT FROM AUTHOR]

The use of aluminum in civil engineering applications has increased significantly over the past decades. Aluminum is a durable, lightweight, and recyclable material that can provide alternative structural solutions for building power transmission towers. In order to achieve this objective, it is necessary to develop structural members that take advantage of specific properties of the material, such as low density, high strength, resistance to corrosion, and the geometric flexibility that aluminum extrusions provide to design robust and easy-to-assemble structures. This paper presents a section optimization study of an existing medium-voltage steel 120–160 kV lattice tower owned by Hydro-Québec, considering the use of various extruded aluminum sections. The proposed optimized aluminum sections are compared with the steel sections of the existing tower. The study’s main objective is to optimize the tower’s aluminum sections. A SAP2000 structural finite element stick model of the tower coupled to a Matlab optimization routine is used to optimize the aluminum sections. ASCE10-15 and CSA-S157-17R22 standards are used to impose the design constraints for selecting the optimized aluminum square and octagonal hollow sections, with and without stiffeners. This study proposes optimized section shapes suitable for constructing aluminum lattice transmission towers. The study reveals that the proposed aluminum tower prototype is twice as light as its steel counterpart. The aluminum members’ price is also very competitive compared to steel.

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Buckling of composite stiffened cylindrical shell panels having cutout is analyzed using the finite element approach. Shell panel and stiffeners are modeled using first-order shear deformation theory and considering displacement compatibility at the stiffener-panel interface. Convergence and validation studies are conducted to establish the accuracy of the present approach. An attempt is made to maximize the uniaxial and biaxial buckling loads by varying the lamination, boundary conditions, load position, depth of stiffeners, and their arrangements. Parametric studies show that buckling load and mode shapes depend on the size of cutout, ratio of shell width to thickness, degree of orthotropy, and fiber orientation angle. The parametric variations considered here may help the practicing engineers to have an elaborate design aid for improving the buckling strength of such shell panels. [ABSTRACT FROM AUTHOR]