Design method of the pinned external integrated buckling-restrained braces with extended core. Part I: theoretical derivation

Abstract

Abstract: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).

Design method of the pinned external integrated buckling-restrained braces with extended core. Part II: finite element numerical verification

“…In Part I (Jiang et al, 2015), the following assumptions are made in a simplified model: the initial geometric imperfection of the core and the external member follow a sinusoidal pattern and the critical state when the core and the external member end start to have two-point-contact is deemed to be the initial state of the BRB (Fig. 2).…”

“…where c 2 , w 1 , w 2 , k 1 , k 2 , r 1 , and r 2 are calculation coefficients mentioned in Part I (Jiang et al, 2015);…”

“…Based on the bending capacity of the external member, the design criteria for the external member of the pinned BRBs were deduced in Part I (Jiang et al, 2015). The value of the BRB's restraining ratio ξ is…”

“…1). Based on a hypothetical core member's contact force distribution mode, Part I has theoretically derived the core contact force and the bending moment distribution of the external member (Jiang et al, 2015). In addition, the design criteria of the external member and the strengthened core region (SCR) have been formulated, so as to prevent the pinned BRBs from the two failure modes mentioned above.…”

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Abstract: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).

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