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An economic type of buckling-restrained braces (BRBs) to allow long spans and large capacities, the reduced-core-length BRBs (RCL-BRBs) are formed by sequentially assembling ordinary BRBs (yield portions) and ordinary braces (elastic portions) with high-strength bolts. This paper presents design recommendations for the global stability of the RCL-BRBs via theoretical and numerical investigations. In the analysis, the interaction between the yield and elastic portions of the RCL-BRBs is considered. First, the RCL-BRBs were classified into six types according to their compositions (the yield portion at one end, mid-span or both ends) and joint types (rigid or semi-rigid joint). Second, formulas for predictions of the elastic buckling loads of the RCL-BRBs were theoretically derived, and were verified by performing finite element (FE) eigenvalue buckling analyses. To investigate the nonlinear behavior of the RCL-BRBs, FE models considering both geometrical and material nonlinearities were built and calibrated with existing hysteretic tests of the RCL-BRBs. Then, a parametric study was conducted to investigate the effects of the geometrical parameters on the global stability behavior of the RCL-BRBs. Finally, based on the numerical results, the restraining ratio design requirements corresponding to the different types of RCL-BRBs were proposed to prevent their global buckling under axial compressive loads. Moreover, recommendations on the connection types between the yield and elastic portions of the RCL-BRBs are provided by analyzing a number of numerical examples.

An innovative buckling-restrained brace (BRB) is devised by imposing a cable stayed system (CSS) on a common BRB, namely single cross-arm pre-tensioned cable-stayed buckling-restrained brace (SPCS-BRB). Its overall external stiffness thus load-bearing capacity can be dramatically enhanced over the common BRB. A previous study conducted by the authors investigated comprehensively the elastic buckling behavior of the brace, yet experimental investigations and detailed design suggestions were not provided. Two SPCS-BRB specimens have been devised and tested. Test results revealed that both specimens possessed excellent hysteretic response with stable hysteretic curves, which fulfilled the ductility requirement specified in the AISC seismic provisions. The adopted simplified Finite Element (FE) model for experimental simulations corresponds well with the obtained test results. Moreover, additional FE analysis (FEA) has been conducted on the SPCS-BRBs subjected to monotonic and cyclic axial loads, respectively as to validate the test results further. In addition, threshold values of restraining ratios are obtained by guaranteeing the cables to remain tensioned prior to attaining ultimate failures, and ensuring maximum load resistance of the SPCS-BRBs is obtained. It is observed from the FEA that global instability failures of the SPCS-BRBs are caused by expansion of yielding at the extreme fibers of the external tube. Finally, FEA has been conducted on the load resistance of the SPCS-BRBs by considering the effect of interactive buckling and prestressing force of cables. It is found that interactive buckling could become critical in dominating the load resistance of the SPCS-BRBs when single-wave symmetric buckling mode is considered.

This paper presents the sectional strength design method of concrete-infilled double steel corrugated-plate walls with T-section (T-CDSCWs). The T-CDSCW is composed of flange and web wall elements and concrete-filled steel tubes, where the former are formed by bolt-connected steel corrugated-plates and infilled concrete while the latter behave as vertical boundary elements. Load bearing capacities of T-CDSCWs are significantly improved by the favorable combination effect between bolt-connected steel corrugated-plates and infilled concrete in the wall elements. The failure mechanism and the sectional strength design of T-CDSCWs under combined axial compression and bending moment are focused analytically, experimentally and numerically, with an assumption of no consideration of overall instability of T-CDSCWs and local buckling of the steel corrugated-plates in the wall elements. An experiment of the T-CDSCW for sectional strength prediction was carried out, and a refined finite element (FE) model of the T-CDSCW was validated by the experimental results. Based on the FE model, parametric analyses of T-CDSCWs are performed to further investigate the effects of steel ratio and sectional geometry on the load-bearing capacities. It is found that T-CDSCWs under axial compression have completely different values of load-bearing capacities when they incorporate different bending direction moments. Based on experimental and numerical results, design formulas for predicting the sectional strength of T-CDSCWs under axial compression and bending moments are proposed, providing a preliminary structural design method of T-CDSCWs.

The porosity of a self-lubricating chromium-free passivation film is evaluated by means of a novel finite element model and structural parameter, λ (λ represents the porosity of passive film). The applicability of this equivalent model is validated via thin-film thermocouple measurements and laser interferometry. Our results revealed that the roughness of the film can be improved by a lubricating filler. A value of λ = 0.25 yielded the optimal friction and wear characteristics of the self-lubricating chromium-free passivation film. This optimal condition corresponded to temperature values and stress values of 77.99°C (theoretical) and 81.24°C (experimental), and 1.67 × 105 Pa (theoretical) and 1.65 × 105 Pa (experimental), respectively. The close correspondence between the experimental and the theoretical results indicate that the model is reasonable.

Concrete-infilled double steel corrugated-plate walls (CDSCWs) are composed of two steel corrugated-plates (SCPs) which are connected through bolts, and concrete filled the spacing formed between the two SCPs. Two vertical boundary elements are installed additionally at both sides of CDSCWs. On the one hand, the corrugated configuration of SCPs has great improvement on the load-bearing efficiency of CDSCWs; on the other hand, much higher bearing capacities and better seismic performance for CDSCWs are provided owing to the interactions among SCPs, bolts and infilled-concrete. This paper investigates the load-bearing mechanism and strength design formulae of CDSCWs under compressions. Since SCPs are prone to local buckling failure between two rows of bolts under the conditions of large vertical bolt spacing and small thickness of SCPs, this paper mainly focuses on the load-bearing mechanism of SCPs in CDSCWs under uniform compressions. The unilateral constraint on SCPs provided from infilled-concrete and the restraining effect on the flexural deformation of SCPs owing to bolts are considered. At first, series of finite element (FE) eigenvalue buckling analyses are conducted to study the elastic buckling behavior of SCPs subjected to uniform compressions. On the basis of Euler's formula, the formulae for predicting the elastic buckling stresses and corresponding normalized slenderness ratios λs of SCPs are achieved respectively. The instability performance of SCPs under uniform compressions is then investigated through FE nonlinear analyses, and accordingly the stability coefficient φs is attained. The corresponding φs−λs curve is therefore established in order to calculate the ultimate bearing capacities of SCPs. In addition, the cooperative performance of material strengths between SCPs and concrete is analyzed numerically when CDSCWs reach their compressive ultimate strength. With this consideration, the design method for predicting the cross-sectional strength of CDSCWs under compressions is proposed. Moreover, a CDSCW specimen with I-section is tested under a compressive load. Its cross-sectional strength is investigated experimentally. The results of the experiment coincide with those of numerical simulation, this verifying the safety and validity of the design method for cross-sectional strength design of CDSCWs.

This paper investigates the elastic buckling loads, load resistance and hysteretic responses of the multiple cross-arm pre-tensioned cable stayed buckling-restrained braces (MPCS-BRBs) with circular rigid plates as the cross-arms that are fixed to the external tube, and the circular rigid plates are considered equivalent as stays with infinite stiffness in the finite element analysis (FEA). The span and elastic buckling load efficiency of the MPCS-BRBs could be increased and improved effectively by adopting multiple cross-arms that are considered to possess infinite stiffness. Explicit expressions for the elastic buckling loads of the MPCS-BRBs are obtained in closed form through curve fitting, by adopting the FEA results on a generalized structural design parameter β that is deduced from a single cross-arm PCS-BRB (SPCS-BRB). In addition, a protocol has been proposed for the height of stays so as to achieve a convenient and generalized design guide, where the outermost point at each stay falls on the same circular arc. Furthermore, the load resistance and hysteretic responses of the MPCS-BRBs subjected to monotonic and cyclic axial loads are explored through an elastic-plastic FEA. It is found that a lower limit of restraining ratio exists, which would ensure overall instability of the MPCS-BRBs not to occur by considering an optimal initial pre-tensioning force in the cables so that they do not become slack before the MPCS-BRBs reach their ultimate failures, and ensure maximum ultimate load-carrying capacities of the braces to be obtained. The investigation and its findings on the elastic buckling loads, load resistance and hysteretic responses of MPCS-BRBs provide fundamentals and guidance for their preliminary design in actual engineering applications.

Buckling-restrained braces (BRBs) could be installed in pares in high-rise frames or long-span structures, forming inverted-V patterned BRB systems, and the pre-compression effects are inevitably introduced into the BRB systems due to the vertical loads transmitted from upper structures. This paper presents the investigations on hysteretic performances of the inverted-V patterned BRB systems subjected to lateral cyclic loadings and vertical pre-compression. First, a parametric study via finite element (FE) analyses is conducted, considering the parameters including: pre-compression factors, vertical translational rigidity ratios, angles of the BRB systems and material properties of the BRB cores. According to the FE results, design recommendations are provided for practical designs of the BRB system and each individual BRB member. Then, based on the evaluation of the vertical and horizontal loading effects applied to the roof of a long-span structure equipped with the BRB system, formulas are proposed for designing of the long-span roof subjected to pre-compression as well as lateral earthquake effects. Finally, design procedures for the BRB system and the long-span roof are provided, which are further demonstrated by a practical design example.

Multiple cross-arm Pre-tensioned Cable Stayed Buckling-Restrained Braces (MPCS-BRBs) can significantly enhance the elastic buckling performance and load resistance over common double-tube BRBs because of the additional cable stayed system. Previous studies conducted by the authors intended to investigate the lower limits of restraining ratios of MPCS-BRBs with pin-ended stays subjected to either monotonic or cyclic axial loads, where the initial geometric imperfection was taken to be consistent with the first order buckling mode. This study is a continuation of the previous paper, and it aims to explore interactive buckling of MPCS-BRBs with pin-ended stays in order to obtain a safe estimate of their load-carrying capacities through nonlinear Finite Element Analysis (FEA). In addition, interactive buckling of MPCS-BRBs is considered by introducing a series of asymmetric imperfections that are the mixtures of symmetric and antisymmetric imperfections during buckling analysis. The effects of different imperfections (symmetric, antisymmetric, and asymmetric) and initial pre-tensioning force of cables on the load-carrying capacities of the MPCS-BRBs with and without minor diagonal cables are explored and compared. Furthermore, a conservative design approach for those MPCS-BRBs can be established by fulfilling the corresponding lower limits of restraining ratios and optimal initial pre-tensioning force of cables based on the findings considering different types of initial geometric imperfections. Finally, such a conservative design approach is validated through nonlinear FEA for MPCS-BRBs subjected to either monotonic or cyclic axial loads. The findings in this study could provide guidance for a preliminary conservative design of the MPCS-BRBs in actual engineering applications.

Purpose: The purpose of this study was to investigate finite element biomechanical properties of the novel transpedicular transdiscal (TPTD) screw fixation with interbody arthrodesis technique in lumbar spine. Methods: An L4–L5 finite element model was established and validated. Then, two fixation models, TPTD screw system and bilateral pedicle screw system (BPSS), were established on the validated L4–L5 finite element model. The inferior surface of the L5 vertebra was set immobilised, and moment of 7.5 Nm was applied on the L4 vertebra to test the range of motion (ROM) and stress at flexion, extension, lateral bending and axial rotation. Results: The intact model was validated for prediction accuracy by comparing two previously published studies. Both of TPTD and BPSS fixation models displayed decreased motion at L4–L5. The ROMs of six moments of flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation in TPTD model were 1.92, 2.12, 1.10, 1.11, 0.90 and 0.87°, respectively; in BPSS model, they were 1.48, 0.42, 0.35, 0.38, 0.74 and 0.75°, respectively. The screws' peak stress of above six moments in TPTD model was 182.58, 272.75, 133.01, 137.36, 155.48 and 150.50 MPa, respectively; and in BPSS model, it was 103.16, 129.74, 120.28, 134.62, 180.84 and 169.76 MPa, respectively. Conclusion: Both BPSS and TPTD can provide stable biomechanical properties for lumbar spine. The decreased ROM of flexion, extension and lateral bending was slightly more in BPSS model than in TPTD model, but TPTD model had similar ROM of axial rotation with BPSS model. The screws' peak stress of TPTD screw focused on the L4–L5 intervertebral space region, and more caution should be put at this site for the fatigue breakage. The translational potential of this article: Our finite element study provides the biomechanical properties of novel TPTD screw fixation, and promotes this novel transpedicular transdiscal screw fixation with interbody arthrodesis technique be used clinically. Keywords: Bilateral pedicle screw system, Biomechanics, Finite element, Lumbar arthrodesis, Transpedicular transdiscal screw

In this paper, a double-corrugated-plate shear wall (DCPSW) is proposed. It consists of two trapezoidally corrugated plates connected with high-strength bolts. It could be utilized in high-rise buildings as an alternative of the ordinary corrugated plate shear wall (CPSW) to resist lateral shear loads resulting from horizontal seismic or wind effects. In this paper, the elastic buckling behavior of DCPSWs subjected to pure in-plane shear loads is of major concern and is firstly investigated. The DCPSWs are equivalent into orthotropic plates, and accordingly, the rigidity constants, including flexural rigidity constants in the orthotropic directions ( D x and D y ) and the torsional rigidity constant ( H ), are defined and theoretically derived. By comparing the theoretical formulas of the rigidity constants with the results obtained from finite element (FE) eigenvalue buckling analyses, these theoretical formulas are validated to be accurate enough for practical engineering applications. Then, the shear elastic buckling formulas of the DCPSWs are provided by means of FE analyses and numerical fitting technique, and these formulas are validated to be able to conservatively predict the shear elastic buckling loads of DCPSWs with good accuracy. Finally, the shear-resistant behavior of the DCPSWs is investigated via a parametric study of FE models subjected to monotonic shear loads. It is concluded that the normalized aspect ratio could be regarded as a comprehensive design parameter which reflects the ultimate shear resistance of the DCPSW.

This paper proposes Multiple cross-arm Pre-tensioned Cable Stayed Buckling-Restrained Braces (MPCS-BRBs) with pinned connections between stays and external tube. By adopting pin-ended stays, the additional bending moment that would be exerted on those connections can be effectively released instead of fixed connections. This eliminates premature strength failures at those connections and simplifies the tensioning process of the cables, thus making the pin-ended stays to be a very practical option in engineering applications. Comparative studies have been conducted on the elastic buckling, load resistance and cyclic behaviors of the MPCS-BRBs with and without additional minor diagonal cables through Finite Element Analysis (FEA). Explicit expressions for the elastic buckling loads of the two types of MPCS-BRBs are obtained in closed form through curve fitting based on a generalized structural design parameter β of the external restraining system. It is found that the elastic buckling performance of the MPCS-BRBs with additional minor diagonal cables could be enhanced dramatically as compared to those not possessing the minor diagonal cables. At last, by ensuring the major cables not to become slack before reaching ultimate failures of the MPCS-BRBs, the load resistance and cyclic behaviors subjected respectively to monotonic and cyclic axial loads are explored through an elastic-plastic FEA. Corresponding lower limits of restraining ratios are attained, where they would provide fundamentals and guidance for preliminary design of the MPCS-BRBs in actual engineering applications.

This paper proposes a new type of composite walls, namely concrete-infilled double steel corrugated-plate walls (CDSCWs). The CDSCW consists of a wall element that is formed by two steel corrugated-plates, where they are interconnected through high-strength bolts, and the spacing between the two steel corrugated-plates is filled with concrete. Additionally, two concrete-infilled steel tubes (CFSTs) are assigned as vertical boundary elements at both sides of the wall element. Not only the corrugated configuration of steel sheets themselves would significantly improve the load-bearing efficiency of CDSCWs, but also the interactions and combined actions among steel corrugated-plates, high-strength bolts and concrete could provide much better load-bearing capacity and seismic performance for CDSCWs. In addition, industrial mass production of the CDSCWs can be achieved by adopting integrated cold-formed steel rolling techniques. Therefore, the CDSCWs are much more suitable for applications in high-rise building structures as shear wall structural systems that carry axial loads and bending moments as well as shear loads. This paper mainly investigates the overall instability performance of I-section CDSCWs under uniform compressions and corresponding design formulae are recommended. Firstly, Finite Element (FE) eigenvalue buckling analyses are carried out to investigate the overall elastic buckling behavior of CDSCWs subjected to vertical compressive loads. The formulae for estimating the elastic buckling loads of CDSCWs and corresponding normalized slenderness ratios λn are obtained based upon the form of Euler's formula. The overall instability performance of CDSCWs under compressions is then studied by FE nonlinear analyses, leading to the overall stability coefficient φ as well as φ-λn curve for their strength design. Moreover, an I-section CDSCW specimen has been designed and tested under uniform compressive load, and its overall instability performance is investigated experimentally. The results obtained from the experiment show an agreement with those obtained from FE numerical analyses, which also verifies the safety and validity of φ-λn curves for the strength design of CDSCWs.

Foreign object damage (FOD) has been identified as one of the main concerns for fan blades. In this paper, systematic experimental and numerical investigations are conducted on aerofoil specimens subjected to FOD by a falling object. The failure mechanism is attributed to the combination of stress concentration, residual stress, and initial damage. Finite element analysis is carried out to simulate the stress field. Using the experimental data from smooth, typically notched, and FOD notched specimens, a novel theory of critical distance model coupling residual stress and initial damage is proposed, falling in a scatter band of 2.

This paper presents investigations into the overall stability design of irregularly-shaped concrete-filled steel tubular columns with T-shape (T-ICFSTCs). The T-ICFSTC consists of I-steel, U-steel, and infilled concrete, forming a multi-cell steel tubular column. They are applied in the T-shaped sectional corner of the intersection between two walls in the residential buildings structures. The overall instability of the slender T-ICFSTCs may still be a significant concern in their strength design when they are placed in a higher spacing between two adjacent floors. This paper mainly focuses on establishing a design method for predicting the overall stability capacity of T-ICFSTCs subjected to axial load. Firstly, experimental investigations of an end-hinged T-ICFSTC and an end-fixed T-ICFSTC under axial load were carried out for checking its overall stability bearing capacity. Subsequently, the refined finite element (FE) model of the T-ICFSTCs is established and validated by the experimental results. In addition, the elastic buckling behavior of T-ICFSTC is studied by employing finite element (FE) eigenvalue buckling analysis, and the corresponding normalized slenderness ratio is obtained in the form of the Euler formula. Finally, based on the FE model validated experimentally, the parametric analyses of T-ICFSTCs are performed to investigate their overall stability capacities through changing the effects of steel ratio, sectional size, and material strength combination between concrete and steel. With these FE parametric analytic results, the overall stability coefficient φ, as well as φ-λ curves of T-ICFSTCs, are then obtained. These curves form the overall stability design formula of T-ICFSTCs loaded axially and apply in a common range of the percentage of load-carrying capacity shared by concrete. This design formula provides fundamentals to further develop a comprehensive design method of the T-ICFSTCs subjected to combined axial loads and moments.

Buckling restraining braces (BRBs) have functions of both high load-carrying capacity and good energy-dissipation performance. Therefore, they are widely used in high-rise buildings and large-span space structures as lateral resistant axially-loaded members. But, in actual engineering applications, BRBs may be subjected additionally to external lateral loads so that the external restraining system (ERS) should be strengthened against the adversely lateral load effects in addition to the effects imposed by the core bending. Therefore, this paper investigates the instability mechanism and design method of BRBs considering additional symmetrical lateral load effects. First, the formula for predicting the lower limit of the restraining ratio of uniform-section BRBs is derived, based on considering the combined effect of an axial compression load of the core and a symmetrical external lateral load. Then, taking the double-tube BRB (DT-BRB) as an example, a finite element (FE) model is established with the FE software ANSYS to investigate the influence of the key parameters on the elastic buckling performance, elastic-plastic ultimate load-carrying capacity and hysteretic behavior. The FE numerical investigations of the key parameters covering the common application variation in the length and section size, the lateral load types and amplitudes, have been carried out, focusing on the effect of the parameters on the outcomes of the proposed lower limit of the restraining ratio. Finally, the design procedure for the DT-BRB is established according to the lower limit of the restraining ratio, which is used as a preliminary fundamental structural design guide in actual application.

This paper presents a numerical investigation on elastic buckling and hysteretic behavior of a steel angles assembled buckling-restrained brace (SAA-BRB). The SAA-BRB is composed of a cruciform-sectional steel core encased by an external restraining system, which consists of four steel angles connected together by high-strength bolts and spacers. It is found that the SAA-BRB may fail in a global buckling mode or in a local buckling mode. In order to predict the global and local buckling behavior of SAA-BRBs, two design parameters: the restraining ratio and segment restraining ratio are proposed. To determine these two design parameters, a simplified theoretical model of SAA-BRBs and an accurate finite element (FE) model are used to investigate the global and local elastic buckling behaviors of SAA-BRBs. Based on more than 500 FE results, explicit expressions of the restraining ratio and segment restraining ratio are obtained and validated to be sufficiently accurate for practical design applications. In addition, 20 refined FE models considering material and geometrical nonlinearities are used to carry out parametric studies for comprehensively investigating the hysteretic behavior of SAA-BRBs. Finally, the following design recommendations for fix-ended SAA-BRBs are proposed: (1) the restraining ratio should be >2.2 to prevent a SAA-BRB from the global buckling failure, and (2) the segment restraining ratio should be >6.0 to prevent a SAA-BRB from the local buckling failure.

This study investigates the load-carrying behavior of a proposed all-steel buckling-restrained brace (BRB) under seismic loading. The proposed steel channels assembled BRB (SCA-BRB) consists of a steel core plate encased by four steel channels assembled by high-strength bolts. Self-weight of an SCA-BRB is relatively small since the use of concrete is eliminated, leading to easier transportation and erection of the BRB. Firstly, by simplifying the restraining system of an SCA-BRB into a 2-chord battened column, the reduction factor of the elastic buckling load of the restraining system considering the discrete connection of bolts was derived. On this basis, the formulas in predicting ultimate resistance of an SCA-BRB were deduced along with the formulas of the lower limit of restraining ratio, and the upper limit of bolt spacing. Then, subassemblage test results of four specimens were reported. All the test specimens maintained stable load-carrying capacity during the loading process, and satisfactory energy-dissipating ability was achieved. Finite element (FE) models were established, and they well predicted the hysteretic responses of the test specimens. A total of 25 additional FE models was analyzed to perform a parametric study, verifying the effect of the member length, number of bolts, steel grade, gap size and geometrical imperfection on the hysteretic response and ultimate resistance of BRB. Finally, a design procedure of the SCA-BRB was proposed based on theoretical formulas, which have been validated by tests and FE results.

Lots of endeavors have been made to apply optimization techniques to real design problems for various engineering beam-plate structures, however, due to the limitation of traditional topological form and the difficulty of finding the optimal topology in numerous optional design plans, many beam-plate structure designs are not the optimal solution but only a feasible solution. This paper proposes an integrated optimal design framework for beam-plate structure based on combining bi-directional evolutionary structural optimization (BESO) and surrogate model method, which covers three optimization levels, as dimension optimization, topology optimization and section optimization. BESO is used for topology optimization. In order to deal with beam-plate structures, the traditional BESO method is improved by using cubic box as the unit cell instead of solid unit to construct periodic lattice structure. Requirements for the framework are discussed based on the features of beam-plate structure design process first. The proposed framework consists of automated finite element modeling module, structure optimization module and post-processing module. Usefulness of the designed framework is examined through a cantilever beam structure design.

In recent years, buckling-restrained braces (BRBs) have been widely utilized in engineering structures. Generally, BRBs are diagonally installed in frame structures to serve as lateral-resistance and energy-dissipation members. To prevent the local buckling of the unrestrained portion of a pin-ended BRB, an end collared BRB (EC-BRB) was proposed by prior researchers by installing end collars at both ends of an ordinary BRB. By using this approach, the enhancement construction of the unrestrained portion could be remarkably simplified, and the end collars can provide lateral restraints to the restraining member, thus improving the global stability of the BRB member. In this paper, a design method for global buckling prevention of pin-ended EC-BRBs based on the restraining ratio requirements is provided via theoretical and numerical analyses. The equation of elastic buckling loads of EC-BRBs is firstly derived and validated by the eigenvalue buckling analyses via ANSYS, and the restraining ratios of EC-BRBs could be further calculated. Then, the restraining ratio requirements of EC-BRBs are theoretically proposed based on the magnification factor of the mid-span lateral deformation, and accordingly a recommended design procedure is provided. The design procedure is further validated by numerous finite element (FE) models subjected to hysteretic and monotonic loadings, indicating that this procedure can conservatively ensure the global stability of EC-BRBs and it is suitable for practical engineering applications.

Adequate compression during mammography lowers the absorbed dose in the breast and improves the image quality. The compressed breast thickness (CBT) is affected by various factors, such as breast volume, glandularity, and compression force. In this study, we used the finite element analysis to simulate breast compression and deformation and validated the simulated CBT with clinical mammography results. Image data from ten subjects who had undergone mammography screening and breast magnetic resonance imaging (MRI) were collected, and their breast models were created according to the MR images. The non-linear tissue deformation under 10−16 daN in the cranial-caudal direction was simulated. When the clinical compression force was used, the simulated CBT ranged from 2.34 to 5.90 cm. The absolute difference between the simulated CBT and the clinically measured CBT ranged from 0.5 to 7.1 mm. The simulated CBT had a strong positive linear relationship to breast volume and a weak negative correlation to glandularity. The average simulated CBT under 10, 12, 14, and 16 daN was 5.68, 5.12, 4.67, and 4.25 cm, respectively. Through this study, the relationships between CBT, breast volume, glandularity, and compression force are provided for use in clinical mammography.

Vierendeel steel truss arches are often used in lighting zones of the spatial roof to obtain good permeability and lighting effects. They are different from conventional steel truss arches in terms of failure mechanism and strength design because they have only transverse tubes without diagonal tubes between chords. The chords of the Vierendeel truss arch undertake axial, bending and shear actions while the transverse tubes only resist the bending action. Hence, their structural design against strength is different from conventional steel truss arches. However, this aspect is not well analyzed in literature. This study analyzed the in-plane instability mechanism, failure mode and corresponding strength of the Vierendeel truss arch under a uniform radial load, a full-span uniform vertical load, a half-span uniform vertical load and their combinations. The global in-plane elastic buckling load of the arch under a uniform radial load is derived firstly and an interaction design formula for predicting the global in-plane strength of the arch under a uniform axial compression is proposed. It is found that the chords of the arch may fail in fully sectional plastic moment mode. Transverse tubes may fail because of the end moments. Slender enough arches may also undergo global failure. Strength design equations for local chord failure and for global failure of arches are developed. All of the equations proposed for predicting global in-plane elastic buckling, global in-plane ultimate strength and chord local strength of the arch agree quite well with the finite element results.

This paper proposes a new type of buckling-restrained braces (BRBs), namely shuttle-shaped buckling-restrained braces (SS-BRBs). The proposed SS-BRB is composed of a circular steel tube as the inner core, and a shuttle-shaped thin-walled steel tube as the external restraining member. The space between them is filled by a steel-plate isolation system. The shuttle-shaped restraining member of the SS-BRB significantly improves load-carrying efficiency and saves material in its strength design. Moreover, the SS-BRB is more aesthetically appealing and can be utilized as an exposed BRB in long-span or spatial structures. In terms of the concept of restraining ratio of a BRB, no design method of an SS-BRB is available currently because it concerns the solution of the elastic buckling load of an SS-BRB. Therefore, the elastic buckling load of a pin-ended SS-BRB is initially studied by adopting the equilibrium method and is further verified through finite element (FE) method. The lateral displacement function of an SS-BRB, and the longitudinal stress at the extreme fiber of the external restraining member are derived by considering an initial geometric imperfection that is consistent with the first order overall buckling shape of the SS-BRB. A correction factor considering shear deformation has been incorporated for a more accurate prediction. The lower limit of the restraining ratio for a load-bearing type of SS-BRBs is further obtained based on yielding of the extreme fiber of the restraining member. Furthermore, the proposed formula has incorporated a strain hardening factor for the SS-BRB that experiences strain hardening of the core after its initial yielding. The proposed formulas have been validated through FE numerical analysis. The findings in this paper provide fundamentals to develop the design method for an energy-dissipation type of SS-BRBs.

The concrete-infilled double steel corrugated-plate walls (CDSCWs) consist of two steel corrugated plates (SCPs), infilled concrete and two boundary elements. The two SCPs are connected by high-strength bolts and the spacing between the two SCPs is filled with concrete. The two vertical boundary elements are installed at both sides of CDSCWs. The sectional load-bearing performance of CDSCWs only under uniform compression has been investigated previously by the authors. But CDSCWs under a combination of compression and in-plane bending moment are applied in practice widely and commonly. Therefore, this paper presents the corresponding sectional load-capacity design method of CDSCWs under a combination of compression and in-plane bending moment. Firstly, an experimental investigation on sectional load-capacity of an I-shaped CDSCW specimen subjected to combined compression and in-plane bending moment is completed. The experimental results reveal a high axial load-bearing efficiency of the SCPs in the CDSCW specimen, and also validated the finite element (FE) model adopted in this study. Then, the FE numerical simulation is applied to systematically analyze the load-bearing performance of CDSCWs subjected to the combination of compression and in-plane bending moment. The coefficient φsp is introduced to consider the local buckling of compressive zone and the weakening effect of tensile-compressive transition zone in SCPs. The coefficient βc is introduced to consider the weakening effect of tensile-compressive transition zone in concrete and the adverse cooperative effect among SCPs, concrete and boundary elements owing to their different ultimate strains at the ultimate state of CDSCWs. As a result, the N-M correlation curve for predicting the sectional load-bearing capacity of CDSCWs under both the uniform compression and in-plane bending moment is then established and also verified by the experimental results.

This paper studies the load-carrying capacity of concrete-infilled double steel corrugated-plate walls with T-section (T-CDSCWs) under axial compression and biaxial bending. T-CDSCWs are composed of flange and web walls and boundary elements. The T-section is mono-symmetric and exhibits different interaction curves of load-carrying capacity when subjected to axial load and different direction bending. Based on the finite element (FE) model established by the previous study, the local buckling of the steel corrugated-plates is considered in the load-carrying capacity. Subsequently, this paper investigates the behaviours of T-CDSCWs under axial compression and uniaxial bending, including stress distribution, load–displacement curves, and interaction curves. Based on the numerical results, the pure moment capacity is found to be evaluated by reducing the plastic moment capacity, and the interaction equations of N–positive Mx, N–negative Mx, and N–My are proposed in the bilinear, linear, and parabolic form. For biaxial bending, the shape of the interaction curves is almost exclusively related to the axis compression ratio. Accordingly, this paper proposes the interaction equations of Mx–My subjected to certain axial compression. Moreover, the local buckling of steel corrugated-plates has no significant influence on the shape of the interaction curves no matter the bending direction. The global stability of T-CDSCWs is not involved in the study, and with the interaction equations obtained above, the global stability design of T-CDSCWs can be investigated by introducing the magnification factor of the bending moment caused by the secondary effect.

An effective way for improving the global load-carrying capacity of a steel arch with a welded hollow section is to increase the height of its webs. However, the high and thin web may buckle locally, which will affect the global load-carrying capacity and should be taken into account in predicting the global strength of the arch. This paper presents a numerical investigation for the in-plane strength and design for pin-ended circular steel arches with a welded hollow section, focusing on the effects of web local buckling by the large deformation inelastic analysis in association with a finite shell element model. The circular steel arches subjected to a radial load uniformly distributed along the arch length, a load uniformly distributed over the full span of the arch, or/and over the half span of the arch and their various combinations are considered in the investigation of their failure modes and strengths. The initial global and local geometric imperfections as well as residual stresses are included in the finite element model. It is found that web local buckling influences the global strength of the steel arches significantly and needs to be accounted in formulate their strength design formulas. The parameters related to the web local buckling and global buckling of the arch are thoroughly explored. It is found that the stability coefficients of arches under the nominal uniform axial compression are related to the equivalent normalized web height-to-thickness ratio of the cross-section and the normalized slenderness of the arch, and accordingly the design formula of the stability coefficients is proposed by including their effects. In addition, a design formula for predicting the strengths of the arches under a load uniformly distributed over the full span is developed by introducing a corrective coefficient into the stability coefficient, and it is found that the corrective coefficient is related to the arch rise-to-span ratio and slenderness of the arch. Furthermore, a general interaction design formula is developed for predicting in-plane strength of the arches under general in-plane loading such as a load uniformly distributed over the half span of the arch and various combinations of a full span uniform load and a half span uniform load. Comparisons with the finite element results demonstrate the proposed design formulas can provide good predictions and/or lower bound predictions for the strengths of the steel arches with a welded hollow section.

Pre-compression loads are conducted in BRBs if the installation of frames and BRBs are performed simultaneously. In this paper, the load-carrying and energy-dissipating behavior of BRBs under pre-compression are investigated by subassemblage tests and additional finite element (FE) analyses. A total of five specimens were tested, in which two specimens were tested by cyclic pure compression loads and three specimens were tested by hysteresis loads; four of them maintained stable load-carrying behavior during loading process. The load-carrying and energy-dissipating behavior of the specimens were satisfactorily simulated using a refined FE model with a combined isotropic and kinematic hardening rule of the core material, and the compression strength adjustment factor and the stress enhancement coefficient were well predicted by the FE analytical results with a relative error less than 3.0%. The FE analytical results of BRBs with different pre-compression strains are presented, indicating that the pre-compression in a BRB would aggravate the stress enhancement of the core material in both tension and compression, yet it would hardly influence the value of the compression strength adjustment factor.

The augmented electric-field integral equation is extended for the analysis of inhomogeneous media at low frequencies. The internal surface integral equation for inhomogeneous region is derived from the vector potential ( ${{\mathbf A}}$ ) and the scalar potential ( ${{\mathbf \Phi }}$ ) equations, which are free of low-frequency breakdown. In the new equations, Green's functions of ${{\mathbf A}}$ and ${{\mathbf \Phi }}$ for inhomogeneous media are incorporated. Due to the absence of the analytic solutions, Green's functions for ${{\mathbf A}}$ and ${{\mathbf \Phi }}$ are solved numerically with the finite-element method and represented in matrix forms. Numerical examples are presented to demonstrate the validity of the proposed scheme in the study of inhomogeneous objects at low frequencies.

This paper proposes a new type of buckling-restrained braces (BRB), namely a pre-tensioned cable stayed buckling-restrained brace (PCS-BRB) which is formed through introducing an additional structural system of pre-tensioned cables and a number of cross-arms to the outside of a common BRB. This new system significantly improves the BRB’s overall external restraining stiffness, hence increasing the load-carrying efficiency in its structural design. Due to its aesthetically appealing structure, it can be utilised in stadiums and so forth as a laterally resistant brace. Equilibrium method is utilised to deduce formulas of elastic buckling load of pin-ended PCS-BRB. The restraining ratio and the initial pre-tensioning force of cables are investigated to explore the effect on the axial compressive load-carrying capacity of the PCS-BRB through finite element analyses in elastic-plastic range. The findings indicate that two different types of buckling modes may occur in this PCS-BRB, namely single-wave symmetric and double-wave antisymmetric buckling modes. It was found from theoretical and numerical analyses that: a negative linear correlation exists between elastic buckling load and initial pre-tensioning force of the cables; the geometric parameters of the cable stayed system possessed remarkable effect on the elastic buckling load. In addition, the post-yield behaviour and ultimate compressive load-carrying capacity of the PCS-BRB is directly proportional to the restraining ratio, and there exists a lower limit of the restraining ratio which allows the inner core to reach full cross-sectional yielding without overall instability failure of the PCS-BRB. Furthermore, there exists an optimal initial pre-tensioning force of cables to make the load-carrying capacity of the PCS-BRB to reach a maximum value. The investigation of elastic buckling and load resistance of PCS-BRB provides fundamentals to further develop a complete design method of PCS-BRB.

The A- $\Phi $ formulation with generalized-Lorenz gauge is free of catastrophic breakdown in low-frequency regime. In the formulation, A and $\Phi $ are completely separated and Maxwell’s equations are reduced into two independent equations pertinent to A and $\Phi $ . This, however, leads to more complicated equations in contrast to the traditional E formulation. The numerical dicretization of the equations is challenging, especially for the equation pertinent to A. By virtue of the differential forms theory and Whitney elements, the direct action of divergence operator on A is bypassed. Thus, the equations can be discretized compatibly using regular finite element method. The condition of the resultant matrix system is much better than that of the E formulation as frequency becomes low, and even approaches to zero. The generalized-Lorenz gauged A- $\Phi $ formulation is verified to be accurate and efficient for low-frequency circuit problems.

This paper deals with elastic shear buckling behavior of infill panels in sinusoidally corrugated steel plate shear walls, and fitting equations predicting the shear buckling loads are presented. Firstly by using finite element analyses (FEA), the previous formulae for bending rigidities of sinusoidally corrugated plates are revised, then pure shearing model are established to study the effects of key parameters on elastic shear buckling of sinusoidally corrugated infill panels, such as the aspect ratio, corrugation ratio, corrugation depth to plate thickness ratio and corrugation repeating number. Based on extensive FEA numerical results, fitting equations with good accuracy are proposed to estimate elastic shear buckling loads of sinusoidally corrugated panels, which are improved much compared with the solutions in previous studies. It is found that, the formulae for bending rigidities of corrugated plates revised in this paper are accurate compared with the previous ones. For sinusoidal corrugated infill panels, only global buckling and local buckling can be observed in the lowest buckling mode of eigenbuckling analysis, while interaction buckling is not obvious. The parameter of corrugation repeating number has a significant influence on elastic shear buckling loads, whereas it was neglected in previous studies.

In the process of complex engineering designs or optimizations, a large number of physical experiments or numerical simulations are required to evaluate certain performance qualities before a satisfactory result can be obtained. In both cases, constructing an approximate model is often necessary to provide a reliable response as an alternative to experiments or simulations. In this paper, three types of approximation models were developed and applied in a shape design of an aerofoil forging preform tool. Their modeling techniques are presented in detail. An optimal Latin hypercube technique was employed for the design of the experiment and sampling with the expected coverage of parameter space. Finite element (FE) simulations of multistep forging processes were implemented to acquire the objective function values for evaluating the forging performance. By a parametric study, the effects of design variables on objective responses and correlations were investigated for a clear insight into their functional nature. Comprehensive analyses and comparisons between different approximate models have been carried out. Finally, an optimization design of a preform tool was successfully achieved based on a particle swarm (PSO) algorithm combined with the proposed approximate model.

As inspired from a double-arm pre-tensioned cable stayed column (PCSC), a concept of a double-arm pre-tensioned cable stayed buckling-restrained brace (DPCS-BRB) is put forward through adding the core inside PCSC. But a previously published paper only limited into the DPCS-BRBs that have pin-ended stays and their practical application is limited undoubtedly. Therefore, this paper focuses on DPCS-BRBs with fix-ended stays and investigates into their structural performance and design through theoretical derivation and Finite Element Analysis (FEA). With fix-ended stays in the DPCS-BRBs, flexural rigidity and deformations of the stays must be considered in both elastic and elastoplastic FEA of DPCS-BRBs. The design method in obtaining the lower limit value of restraining ratios should be re-established by considering the fix-ended stays. Firstly, this study explores elastic buckling behavior of DPCS-BRBs, focusing on explicit formula prediction of the elastic buckling load under either symmetric and antisymmetric buckling mode by using energy method. The obtained theoretical formulas are then validated through FEA. And then, the static load-carrying behavior and hysteretic performance of DPCS-BRBs are investigated by employing elastoplastic FE models that were validated by experimental tests conducted previously by the authors. Finally, because the possible existence of asymmetric imperfection interaction between two possible aforementioned buckling modes would lead to reduction in the load-carrying capacity, therefore, interactive buckling must be considered for establishing conservative design method of DPCS-BRBs, particularly where prestressing force of cables is involved. The research outcomes attained would provide structural design guidance in engineering applications of DPCS-BRBs with fix-ended stays.

This paper reports experimental and numerical investigations used to develop a simple and accurate design method for the in-plane strength of circular steel I-section arches having a sinusoidal corrugated web under a uniform vertical load over the entire span. In deference to a flat web that can resist both shear and normal stresses, a sinusoidal corrugated web can resist only shear stresses, since its axial and bending stiffnesses are quite small. Tests are carried out to investigate the global in-plane elasto-plastic behaviour and strength of a circular steel I-section arch with a sinusoidal corrugated web under symmetric loading. A finite element model is also developed, validated by the test results, and then used to further investigate the global in-plane elasto-plastic behaviour and strength of the steel arches. Based on the test and finite element results, a design equation for predicting the global in-plane strength of circular steel I-section arches with a sinusoidal corrugated web subjected to a uniform vertical load over the entire span is proposed. It is found from the finite element results that in addition to an in-plane global failure mode, a circular steel I-section arch with a corrugated web may also fail in an elasto-plastic web shear buckling mode. Hence, elasto-plastic shear buckling of the sinusoidal corrugated web in arches must also be considered in their design.

The contact force distribution between the core member and the external member of a buckling-restrained brace (BRB) is closely related to its deformation mode, and it directly affects the working state of the extended core and external restraining member. This study focuses on a pinned BRB with extended core as a research object and investigates the stress state of a BRB. Based on the specified core deformation modes and contact force distributions, the contact force and the bending moment distribution in the external member are deduced. Lastly, by considering the mechanical characteristics of the external member and extended strengthened core region (ESCR), their strength design criteria are established. In the theoretical derivation of the design method, the influence of some parameters is considered, including the initial geometrical imperfection of the external member, the gap between the core and the external member, the rigidity reduction of the restrained strengthened core region (RSCR), and the change of contact position. Finite element numerical verification of the corresponding theoretical derivation is discussed in detail in another paper as Part II (Jiang et al., 2015).

The theoretical derivation from Part I (Jiang et al., 2015) has obtained the core contact force and the bending moment distribution of the external member in the single-wave core deformation mode. In addition, the design criteria of the external member and the strengthened core region (SCR) have also been obtained based on the understanding of the mechanical characteristics of the buckling-restrained brace (BRB). Based on the theoretical results from Part I, this study conducts the corresponding finite element (FE) numerical verification, and the BRB parameter analysis is also performed when the core deforms as a single-wave deformation. The influence of nine parameters on the core contact force and the external member stress is investigated. These parameters include the flexural rigidity of external member, the initial imperfection of external member, the core thickness and its width-to-thickness ratio, the pinned connector length, the external member length, the length of restrained strengthened core region with uniform section and the height of the wing-plate of the SCR, as well as the gap between the core and the external member. Lastly, the 12 examples of BRBs that are designed according to the proposed design criteria are analyzed using FE simulation, and the reliability of the theoretical derivation is also verified.

This paper presents an experimental study on the out-of-plane inelastic buckling strength of fixed circular steel arches under symmetric and non-symmetric loading. A test loading arrangement that allows for lateral deflections to develop freely under vertical loading is described. A finite element (FE) model consisting of the tested steel arch and the loading system is established for carrying out supplementary numerical investigation on the inelastic out-of-plane buckling strength of the fixed steel arches. The FE numerical model is validated by the experimental results. From the experimental results and supplementary FE investigation, it is found that the out-of-plane inelastic buckling strength of fixed steel arches is influenced significantly by the magnitude and distribution of initial out-of-plane geometric imperfections, as well as the out-of-plane elastic buckling modes and the in-plane loading patterns. It is also found that the out-of-plane buckling strength of a fixed steel arch under non-symmetric loading is lower than that under symmetric loading. Based on the experimental and FE results, a lower bound interaction equation is developed for predicting the out-of-plane inelastic buckling strength in the design of fixed circular steel arches against their out-of-plane failure.

For several decades, innovative studies on the external restraining system of the buckling-restrained brace (BRB) have focused on the design and application of BRBs. This paper presents a Spatial Triple-Truss-Confined BRB (STC-BRB) with a longitudinal shuttle-shape and investigates its buckling behaviour, static strength and seismic design. The STC-BRB could significantly improves the material utilization and particularly enhance the architectural aesthetics when it is used as an exposed design externally. The overall elastic buckling performance, load resistance and hysteretic responses of the STC-BRB are investigated numerically by adopting a finite element model (FEM) validated by previously conducted test results of a truss-confined BRB (TC-BRB). A design method regarding the lower limit of the restraining ratios of the STC-BRBs is recommended. First the overall elastic buckling performance of the STC-BRB is comprehensively investigated by using a beam element FEM, leading to an explicit expression for the overall elastic buckling load of the STC-BRB, which is further adopted to define a restraining ratio of the STC-BRB design. Consequently the load resistance of STC-BRBs under monotonic axial compression is numerically analyzed. Accordingly a lower limit of the restraining ratio of the STC-BRBs is recommended for monotonic axial load resistance design, such that the core reaches the fully sectional yield, along with a plasticity strain amplitude of 2% without a global instability of the STC-BRBs. Finally, the hysteretic responses of STC-BRBs subjected to axially compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of the restraining ratio of STC-BRBs is proposed in the design as an energy-dissipating device. The two lower limits of the restraining ratios of the STC-BRBs obtained in this study form fundamentals for the preliminary static and seismic design of STC-BRBs.

This paper presents load-carrying performance and design method for a Shuttle-Shaped Truss-Confined Buckling-Restrained Brace (SSTC-BRB). Such external restraining system (ERS) innovation through adopting longitudinally variable cross-sectional trusses in the BRB significantly enhances axial load-carrying efficiency of SSTC-BRB that could carry very large axial applied load for over long BRB design when used on exposed purpose externally. Firstly, the elastic buckling performance of the SSTC-BRB is comprehensively investigated by adopting a beam element Finite Element (FE) model, and this leads to an explicit expression of the elastic buckling load of the SSTC-BRB that is adopted to define the restraining ratio of the SSTC-BRB for its strength and stiffness design. Consequently, the load resistance of SSTC-BRBs under monotonic axial compression is numerically analyzed. Accordingly, the lower limit of restraining ratio of the SSTC-BRBs subjected to monotonic axial load is recommended for their load resistance design, where the core could be fully yielded with the plastic strain amplitude reaches 2% without global instability of the SSTC-BRBs. Finally, the hysteretic responses of SSTC-BRBs subjected to axial compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of restraining ratio of SSTC-BRBs is proposed for their energy-dissipation design. Those two lower limits of restraining ratios of the SSTC-BRBs obtained in this study provide fundamentals for preliminary static and seismic designs of SSTC-BRBs.

This paper investigates the flexural-torsional buckling behaviour about the symmetric axis of axially loaded concrete-infilled double steel corrugated-plate walls with T-section (T-CDSCWs). The T-CDSCW is composed of steel corrugated-plates, infilled concrete and intermediate bolts, among which a positive composite effect further improves load-bearing capacities effectively and thus reduces the thickness of composite walls. The failure mode of the T-CDSCW with high height and small thickness is governed by global instability, and flexural and flexural-torsional buckling may occur for the T-CDSCW under axial compression. This paper focuses on numerical and theoretical analyses of the flexural-torsional buckling behaviour. Based on the refined finite element (FE) model validated by previous experimental researches, parameter analysis is carried out to investigate the elastic and inelastic flexural-torsional buckling behaviour. The formulas of the elastic flexural-torsional buckling load are derived and prove it feasible to design flexural-torsional buckling in accordance with torsional buckling. Numerical results show that the strength reduction factor of flexural-torsional instability can be delineated well by the height-to-thickness ratio of the web and the normalized torsional slenderness ratio of the T-CDSCW. Together with the design formulas of flexural instability, the design formulas of flexural-torsional instability proposed in this paper supplements the design method of axially loaded T-CDSCWs, and provides the foundation for further investigation into global instability of T-CDSCWs under combined compression and bending.

This paper investigates the flexural buckling behaviour of axially loaded concrete-infilled double steel corrugated-plate-walls with T-section (T-CDSCWs). The T-CDSCW is composed of flange and web wall elements and vertical boundary elements. The wall element consists of two bolted-connected steel corrugated-plates with concrete infilled. The composite effect of the components in the wall element improves the load-bearing capacities of the T-CDSCW efficiently and leads to a thinner wall. Therefore, the failure mode of the T-CDSCW may be governed by global instability. With the web breadth relatively less than the flange breadth, the first-order elastic buckling mode of the T-CDSCW is flexural buckling about the asymmetric axis. The design issue of the flexural instability of the axially loaded T-CDSCW is investigated experimentally and numerically in this paper. The load-bearing and deformation behaviours were investigated by an experiment of the axially loaded T-CDSCW, based on which refined finite element (FE) models of T-CDSCWs are established and validated. The FE buckling analysis is carried out to investigate the elastic buckling behaviour of the T-CDSCW and propose the elastic flexural buckling load and the borderline between flexural and flexural-torsional buckling. Then, the inelastic flexural instability of the T-CDSCW is investigated by the FE nonlinear analysis, and influences of initial geometric imperfection are discussed. The normalized flexural slenderness ratio derived from elastic flexural buckling load delineates flexural instability pretty well and bases the design formulas of strength reduction factor. The design formulas proposed in this paper help to understand the axial load-bearing behaviour of the T-CDSCW.

Double-corrugated-plate shear wall (DCPSW), which is composed of two identical corrugated plates and assembled by connecting bolts, is an innovative type of lateral force resistant device for high-rise building structures. In this paper, the shear resistant behavior of the DCPSW is investigated via tests and additional finite element (FE) parametric study. First, the test results of two DCPSW specimens subjected to monotonic in-plane shear loads are reported. Second, FE models are introduced to perform simulations on the shear resistant behavior of the test specimens; it is seen that the numerical results fit well with the test results, and hence the FE models for simulations of the DCPSWs are validated. Then, an additional parametric study is presented by changing the geometrical parameters including aspect ratio, bolt column number, corrugation amplitude and dimensions of boundary elements of the DCPSWs. As a result, the effects of these parameters on the shear resistant behavior of the DCPSWs are further revealed. It is shown that the ultimate shear resistance of the DCPSWs increases with the increase of aspect ratio, bolt column number and corrugation amplitude, yet the dimensions of the boundary elements have little effect on the shear resistance of the embedded corrugated plates. Finally, by analyzing the results of the parametric study, some design remarks are concluded to provide valuable references for the design of the DCPSWs in practice.

It is widely believed that large composite materials are difficult to build a ship which is longer than 40 meters because of lack of structural stiffness. Up to now, the ships, 72-meter in length, made of glass fiber reinforced composite have been in serve abroad, while 35 meters in China. Therefore, it’s absolutely necessary to study the problem about the stiffness of the 70-metre composite materials hulls. Start from integration design and finite element analysis of composite materials and structure, the influences of material component, laminated angle and laminated sequences of composite materials’ hull on the dynamic stiffness and static stiffness of the ship are studied to explore the method of improving stiffness. The result show that, in the conditions of having the same molded surface, ship's weight and applied stress, it can improve the ship’s longitudinal stiffness to reach standard requirements by using the part of the high modulus fiber as well as the high modulus fiber laying on the outboard of the hull.

The contact interaction between the core and external restraining members is a vital factor that affects the overall performance of buckling-restrained braces (BRBs) significantly. In this study, refined finite element (FE) model was employed to evaluate the contact force between the core and external restraining members and to investigate the BRB performance. Moreover, the influences of strength and stiffness of external restraining member, core length, and other geometric parameters on the BRB performance were also studied. On the basis of numerical results obtained in the study, the recommended values of core width-to-thickness ratio, core thickness and gap were proposed. By considering the core plasticity and the lateral restraint of external restraining member, some formulas for predicting the half-wave length of core buckling as well as contact force were also proposed while the core buckled in multi-wave form. These formulas were numerically verified and could be references in the design of BRB.

Residual stress of thin-walled blanks with complex cavity structure is an important influence factor on the stability of machining. The most residual stress testing technologies is only suitable to measure residual stress of surface or shallow surface. It is difficult to ensure the accuracy to measure residual stress inside workpiece. In order to study the reliability and accuracy of incremental hole drilling method measuring interior residual stress, according to residual stress test for casting ZL205A aluminum alloy tapered thin-walled blank, finite element (FE) model with initial residual stress is established to simulate incremental hole drilling on the platform of ANSYS. Then error and the rationality of the finite element simulation model has been analyzed by comparing the simulation stress value with the test. The results indicate that the incremental hole drilling method has some errors to measures residual stress inside workpiece. The method is only suitable to measure surface residual stress.