Nascimbene R, Brunesi E, Sisti A
Scuola Universitaria Superiore IUSS Pavia, Piazza della Vittoria n.15, 27100, Pavia, Italy.
EUCENTRE, European Centre for Training and Research in Earthquake Engineering, Via Ferrata 1, 27100, Pavia, Italy.
Heliyon. 2024 Oct 25;10(21):e39729. doi: 10.1016/j.heliyon.2024.e39729. eCollection 2024 Nov 15.
The seismic design of precast structures hinges on unique characteristics intrinsic to precast technology. Emphasis is placed on lightweight structural elements for efficient on-site assembly and cost reduction. This leads to increased slenderness in beams and columns compared to traditional cast-in-situ constructions, accentuating the role of second-order effects. Dry pinned joints, favoured for connecting beams and columns, contribute to the overall efficiency in assemblage. Cast-in-situ concrete is typically reserved for connection to foundations and topping precast floor elements. Pinned joints transform the structure into an ideal isostatic system, with cantilevered columns anchored securely at the base, in designers' mind. However, this transformation reduces the energy dissipation capacity, preventing plastic hinge formation in beams and amplifying P-Delta effects in columns. The simplified approach proposed herein assesses dynamic instability in single and multi-storey precast hinged frames, providing a tool for expeditious numerical capacity assessment, useful at the initial design stage. The goal is to predict dynamic collapse and/or the attainment of specific seismic-oriented limit states based on fundamental structural parameters. Incremental nonlinear dynamic analysis, utilising far-field ground motion records, is employed to evaluate performance of a variety of precast structures modelled as equivalent single-degree-of-freedom systems. The outcomes yield inelastic spectra that provide insights into the structural capacity in terms of response modification factor and could help analysts/designers towards seismic performance-based design as well as the assessment problem. These spectra, which can themselves be taken as metrics for structural performance evaluation (in addition to as a reliable tool/means for design), are generated based on various structural parameters, including building height, column aspect ratios, and floor mass configurations, in relation to different limit states typically deemed crucial in the design of these structures for earthquake-induced actions. Regression analyses of median spectra show that polynomial expressions could fit them with good accuracy, as testified by a coefficient of determination in the 0.76-0.98 range for most of the cases.
预制结构的抗震设计取决于预制技术所固有的独特特性。重点在于采用轻质结构构件，以实现高效的现场组装并降低成本。这导致梁和柱的细长比相较于传统现浇结构有所增加，凸显了二阶效应的作用。连接梁和柱时常用的干连接节点有助于提高整体组装效率。现浇混凝土通常用于连接基础和浇筑预制楼板构件。在设计师的观念中，连接节点将结构转变为理想的静定体系，悬臂柱在底部可靠锚固。然而，这种转变降低了能量耗散能力，阻碍了梁中塑性铰的形成，并放大了柱中的P-Δ效应。本文提出的简化方法评估单层和多层预制铰接框架的动力不稳定性，提供了一种在初始设计阶段进行快速数值能力评估的工具。目标是基于基本结构参数预测动力倒塌和/或达到特定的地震相关极限状态。利用远场地面运动记录进行增量非线性动力分析，以评估建模为等效单自由度体系的各种预制结构的性能。结果得出非弹性谱，从反应修正系数的角度深入了解结构能力，有助于分析人员/设计师进行基于地震性能的设计以及评估问题。这些谱本身可作为结构性能评估的指标（除作为可靠的设计工具/手段外），基于各种结构参数生成，包括建筑高度、柱的长宽比和楼层质量配置，与通常在这些结构的地震作用设计中被视为关键的不同极限状态相关。中位数谱的回归分析表明，多项式表达式能够很好地拟合它们，大多数情况下决定系数在0.76 - 0.98范围内即可证明这一点。
