The insertion of steel bracing systems equipped with dissipative devices is a widely used technique for the seismic retrofitting of reinforced concrete (r.c.) framed buildings; yet, few attempts have been made so far to construct an external arrangement in the form of a double skin. The dissipative exoskeleton (DEX) appears convenient from energetic and functional points of view. It eliminates the indirect costs associated with downtime during retrofitting and cuts out the unwanted effects to the existing structure that commonly arise with the dissipative endoskeleton. This paper provides a DEX sizing procedure through use of overdamped elastic response spectra, which could prove a valuable tool for practitioners. The DEX is designed on the assumption of a rigid coupling with the existing structure, making a distinction between mass and stiffness properties of the steel exoskeleton and added damping of the dissipative bracing system. Concentrically braced chevron frames with pinned joints and damped bracing systems incorporating fluid viscous dampers (FVDs) are considered. Elastic‐linear behaviour of steel frame members and nonlinear pure viscous dashpot for FVDs, with a storey‐shear proportional distribution, are hypothesised. The retrofitting of a six‐storey r.c. framed structure, representative of the Italian residential buildings designed for moderate seismic loads during the 1990s, is to be simulated in a high risk‐seismic region. Three external arrangements of DEX are selected: parallel (DEX.Pa) and perpendicular (DEX.Pe) to all façades of the existing building and a mixed solution (DEX.Mi) with both parallel and perpendicular disposition placed along the shorter façades without apertures. Nonlinear structural models of the original (F) and coupled (DEXF) structures are developed in OpenSEES, considering ductile and brittle failure modes of r.c. elements and joints. The seismic analyses not only confirm the effectiveness of the proposed DEX design but also provide insights into the strength and weaknesses of the examined configurations.

中文翻译：

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耗散钢外骨骼，用于钢筋混凝土框架房屋的抗震控制

插入配备有耗散装置的钢支撑系统是钢筋混凝土（rc）框架建筑物的抗震改造中广泛使用的技术；然而，迄今为止，几乎没有尝试构造双层皮肤形式的外部布置。从能量和功能的角度来看，耗散性外骨骼（DEX）显得很方便。它消除了与改造期间的停机时间相关的间接成本，并消除了耗散性内骨架通常对现有结构产生的不良影响。本文通过使用过度阻尼的弹性响应谱提供了DEX大小调整过程，这可能是对从业者有价值的工具。DEX是在与现有结构刚性耦合的前提下设计的，区分了钢外骨骼的质量和刚度特性，并增加了耗散支撑系统的阻尼。考虑了带销接头的同心支撑人字形框架以及结合了流体粘性阻尼器（FVD）的阻尼支撑系统。假设钢框架构件的弹性-线性行为和FVD的非线性纯粘性阻尼器具有层-剪切比例分布。将在高风险地震区域模拟六层RC框架结构的改造，以代表1990年代设计用于中等地震荷载的意大利住宅建筑。选择了DEX的三种外部布置：与现有建筑物的所有立面平行的（DEX.Pa）和垂直的（DEX.Pe），以及混合解决方案（DEX。Mi）沿较短的立面平行且垂直放置，没有孔。考虑到rc元件和接头的延性和脆性破坏模式，在OpenSEES中开发了原始（F）和耦合（DEXF）结构的非线性结构模型。地震分析不仅证实了所提出的DEX设计的有效性，而且还提供了对所检查构型的优缺点的见解。