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Buckling-restrained members ( BRMs) can be classified as the buckling-prevented BRMs and the buckling- delayed BRMs. Buckling-delayed BRMs buckle before the yielding of the core, so it is more economic when it meets the bearing requirements. But most of previous studies focused on the buckling-delayed BRMs. A kind of new members named as the battened core-separated buckling-restrained member (battened CSBRM) was investigated. The effective length coefficient of a chord was obtained firstly based on the equilibrium method. Then elastic buckling loads bending about x and y axis were introduced and the buckling performance was investigated by finite element (FE) buckling analysis. Finally, based on the results of numerical analysis, an interaction formula between normalized slenderness ratio and stability factor was proposed to predict the ultimate bearing capacity. The research shows that the effective length coefficient of a chord is only related to the linear flexural rigidity ratio between a batten and a chord. The buckling mode of a specific member can be predicted by simply comparing the slenderness about two axes. Comparison with FE results show that the proposed interaction formula for calculating the ultimate resistance is effective and conservative. Furthermore, it is recommended that the critical value of normalized slenderness should be taken as 0.75. At last, design recommendations are proposed to prevent the failure of a chord before the overall failure of a battened CSBRM. The above research establishes a unified design method for both types of battened CSBRMs. [ABSTRACT FROM AUTHOR]

The buckling-restrained braces (BRBs) are often connected to the frame structures by fixed joints in practice, and the cores usually have complicated details near the ends, namely unsupported yielding segments and/or strengthened segments. Based on theoretical and numerical analysis, this paper presents the influence of complicated boundary constraints on the behaviors of the BRBs. It is revealed that the fixed joints can effectively prevent the core unsupported segments from bending too much, and BRBs with fixed ends usually perform better than those with pinned joints, and the advantage exists even when the ends of BRBs rotate with frame joints in the structures. Based on theoretical and FEA results, a simplified model is proposed to simulate the core segments near the BRB's ends. Using an iterative algorithm cooperatively, the simplified model can approximately determine the unfavorable additional eccentricities at the ends of restraining part. In the frame structures the rotations at two ends of the BRB are unequal, and the two different eccentricities can be equivalent to the same eccentricity by equivalent eccentricity coefficient. Finally, by taking the equivalent additive eccentricities obtained into account, a design procedure for the fixed-fixed BRBs is achieved. [ABSTRACT FROM AUTHOR]

In buckling-restrained braces (BRBs) with pinned joints, the core component near the ends have influence on both the capacity of the core segments near the ends and the overall behavior of the BRB. Based on theoretical and numerical analysis, this paper discusses the failure modes and the overall behaviors of pinned-pinned BRBs with unsupported yielding segments and strengthened segments near the ends. It is found that the unsupported yielding segments and strengthened segments of the core will bend under axial pressure, which will induce additional eccentricities at the ends of the restraining part, making the stress state more unfavorable. If the unsupported segment of the core is too long, failure may occur in the segment with too much bending. By taking the core segments near the ends out as a free body, a simplified model was obtained. Using an iterative method cooperatively, the simplified model can approximately determine the eccentricities added at the two ends of restraining parts. Finally an overall stability design method that can take the additional eccentricities into account is given. [ABSTRACT FROM AUTHOR]

Throughout the whole design process of the Shenzhen Bao'an Stadium, this paper presents a research into the major difficulties encountered during different stages of design. In the phase of conceptual design, comparison was made among 3 schemes from perspectives including architectural appearance, functionality, structural behavior and construction difficulties, etc. In the phase of scheme verification, both theoretical analysis and a 1:10 scale model test were conducted in order to observe the static and dynamic performance of the structure. In the phase of detailed design, descriptions of several typical joints were presented and the basic principles for joint design of cable-membrane structures were summarized. The above research shows that for the Bao'an stadium, the spoke structure with circular inner and outer cable rings is the best choice. And A-shape column fits the spoke structure best, for its ability to provide sufficient lateral stiffness while making no constraint to the outer ring in radial direction. Research also shows, the 1st buckling mode of the outer ring is in the form of buckling with cable trusses as fulcrums. [ABSTRACT FROM AUTHOR]

To design a spoke structure, basic knowledge of form finding and how architectural form will affect structural behavior is necessary. Hence this paper presents a research into the above two fields, by theoretical derivation and numerical simulation. First, the force-density method was introduced to find the initial state of equilibrium for the structure. Different from ordinary form-finding processes, the analysis in this article goes from shape to force and then back to shape, which successfully avoids the convergence difficulties often encountered when using general force-density method. Comparison was made among different structural forms of the single-layer and two-layer spoke structures, respectively in terms of planar projections of the inner and outer rings, the spatial shape of the outer ring, and cable truss forms, etc. Through these work, the feasibility of different structural forms and main factors influencing structural rigidity were investigated. Research shows that similar inner and outer rings are preferred for the spoke structure, and the height difference of saddle-shaped outer ring does little to improve structural rigidity. Though convex cable trusses can improve structural rigidity efficiently, they tend to lose lateral stability. [ABSTRACT FROM AUTHOR]

Arch wall is a vertical plane structure which combines pure arch, columns and beam together. The applied in-plane vertical loads on the beam will reach the large span arch through columns. For studying the stability of arch wall, the elastic and inelastic mechanical properties of arch wall were discussed in this paper by finite element method. It is shown that lateral bracing stiffness of beam and column stiffness are the key factors which affect the stability of arch wall: if the lateral bracing stiffness is less than its threshold stiffness, the arch wall shows a global out-of-plane buckling mode; if the bracing stiffness is greater than its threshold stiffness and column stiffness is less than its threshold stiffness, the pure arch shows an out-of-plane buckling mode; if both of the bracing stiffness and column stiffness are greater than their threshold stiffness, the arch wall shows an in-plane buckling mode. After that, two analytical models of arch wall from a practical engineering structure were proposed for predicting the ultimate out of plane strength of arch wall. One analytical model reflects only the arch wall laterally braced by equivalent lateral spring resulting from lateral trusses, and the other is a combination of arch wall with longitudinal trusses. The result points out that the lateral bracing stiffness of beam supplied by longitudinal trusses is much larger than the threshold stiffness, the bearing capability of arch wall can be improved only by increasing the stiffness of column or strengthening the reliable connection of column ends. [ABSTRACT FROM AUTHOR]

This paper presented the out-of-plane elastic buckling behavior of circular steel arches discretely and laterally braced, and based on FE analysis a threshold value of bracing stiffness for design was proposed. The effects of bracing parameters, including bracing stiffness, brace types, the number and longitudinal location of bracing point, on the arch elastic buckling behavior were investigated carefully. An equation for predicting the threshold value of bracing stiffness was obtained for equally-spaced lateral braces of pin-ended and fixed arches with I-section in pure compression. And the required arch segment length between bracing points to prevent the arch segment from elastic out-of-plane buckling was proposed. It shows that, the closer brace is to the crown of arch, the higher efficiency brance has to prevent out-of-plane buckling of arch. When arches with lateral braces buckle, buckling half-waves increase with the augment of bracing stiffness, while arches with torsional braces always buckle with one half-wave. For equally-spaced lateral braces, a threshold value of stiffness of arches in uniform compression is suitable to the arches under other general load conditions. When segment length meets the requirement mentioned above for arches with I-section, in-plane asymmetric buckling form will take place before out-of-plane buckling of arch segment. [ABSTRACT FROM AUTHOR]

Based on the previous studies on out-of-plane stability of arches in uniform compression and bending moment, this paper presented the research results of the out-of-plane ultimate strength of circular steel arches under the combination of axial compression and bending by using FE analysis in elasto-plastic range of materials. With the consideration of different geometric parameters, support conditions, section forms and load combinations etc, a design method for predicting the out-of-plane ultimate strength of circular steel arches was proposed based on FEA results. The results obtained indicate that the N-M interaction equation proposed for predicting the out-of-plane strength of arches is applicable for various support conditions and complex load combination, where average axial force, maximum bending moments within 1/3 arc length of arch top and stability coefficient for non-uniform moment distribution are introduced. [ABSTRACT FROM AUTHOR]

In order to create a systematic design method for out of-plane stability of steel arch under the combination of uniform compression and bending, the out-of-plane ultimate strength of circular arch under bending moment is required to be investigated at first. By considering the factors such as arch section types, initial geometric inperfection, residual stresses, rise-to-span ratio, support conditions and end moment ratio, this paper presented design principles for out-of-plane strength of circular arches under bending moment. Firstly, arches under uniform positive bending were studied and stability design curves with normalized arch slenderness for welded I-section, welded box section and hot-rolled pipe section were proposed. Then for arches under non-uniform bending with end moment, two methods of modified normalized slenderness and moment modified coefficient for calculation of the out-of-plane ultimate strength were established, which can be applied in the formulation of design method for arches under the combination of compression and bending. It shows that the stability curve of circular arches under uniform positive bending is similar to that of straight beams. Modified normalized slenderness or moment modified coefficient should be introduced to take account of the effects of moment gradient and negative moment. The results of ultimate strength calculated by the two methods proposed are close to those of FEA. [ABSTRACT FROM AUTHOR]

With the promulgation of JGJ/T 249--2011 'Technical specification for steel arch structure', key issues involved in the design, analysis, fabrication and erection of steel arch structures are discussed, such as load-bearing performance, selection of structural forms, stability and manufacturing process. Compared with those of straight columns and beams, the design theories of steel arch structures, especially for stability design, are more complicated. The structural performance and mechanism are affected by parameters including axis form, span, rise-to-span ratio, boundary conditions, section types, loading forms and their combinations, and lateral braces, etc. It indicates that, in-plane loading-carrying capacity of steel arch is sensitive to the unsymmetrical initial geometry or loading imperfection, and for latticed steel tubular arch the effect of local buckling of chord on global buckling strength needs to be considered. The deformation and performance of arch are complex in out-of-plane flexural-torsional buckling, and the buckling strength is greatly affected by boundary conditions, loading conditions and arrangement of out-of-plane braces. The design methods of in-plane loading-carrying capacity are established and specified in JGJ/T 249--2011 for steel arch including solid-web steel arch (and steel arch with web opening), latticed steel tubular arch and concrete filled steel tubular arch. Further studies are required for out-of-plane stability of arch and design of lateral braces. [ABSTRACT FROM AUTHOR]

By considering the factors such as arch section types, initial geometric crookedness, residual stresses, riseto- span ratio and support conditions, this paper presented the out-of-plane stability design curves for circular arches under uniform compression. It can be not only applied in the practical design of arch under uniform compression directly, but also involved in the design of arch under the combination of uniform compression and bending. It indicates that load with constant direction which causes lower out-of-plane load-carrying capacity of arches is more adverse than one with direction pointing to a constant center. Compared with initial geometric crookedness and residual stresses, rise-to-span ratio and support conditions much more affect the out-of-plane load-carrying capacity. However, stability design curves for arches with different rise-to-span ratio and support conditions are unified by using the normalized arch slenderness. Finally, out-of-plane stability design method of arches with hot-rolled pipe section, welded box section and welded I section is proposed by employing stability design curves for columns of type b, c, d in Chinese code (GB 50017-2003) respectively. [ABSTRACT FROM AUTHOR]