Study on Plastic Design Method of Staggered Truss Structure with Two-Side Connecting Steel Plates
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摘要: 交错桁架框架结构体系(STF结构体系)具有高效、实用、经济的特点,符合建筑工业化发展的趋势,目前已经在我国低烈度抗震设防区域逐步推广应用,众多的优点使其对中高烈度抗震设防区域也有较大的吸引力,其桁架可采用混合式桁架、空腹式桁架或帕式桁架。相对于空腹式桁架以及帕式桁架,混合式桁架因其刚度适中,并且空腹区域可以设置为内走廊等优点,应用最为广泛。已有试验结果表明,虽然混合式STF结构体系受力性能良好,但耗能能力较弱,结构抗震性能有待提升。为改善混合式STF结构的抗震性能,提出在桁架跨中设置两边连接钢板(TSCSP),并将跨中作为消能段用以耗能的延性交错桁架框架结构称之为两边连接钢板式交错桁架框架结构(TSCSP-STF结构)。在多遇地震作用下,消能段中的钢板既不屈曲也不屈服;在罕遇地震作用下,仅消能段中的钢板屈服耗能,非消能段桁架保持弹性,从而提高混合式STF结构的延性和耗能能力,有效改善混合式STF结构易发生腹杆失稳破坏的问题。
在分析了消能段剪切承载力需求的基础上,推导了两边连接钢板剪切承载力需求的计算方法,并将两边连接钢板等效为偏心交叉支撑,建立TSCSP-STF结构的简化分析模型,进而建立结构体系的塑性设计方法和流程。根据文中提出的塑性设计方法,设计一个10层的TSCSP-STF结构,并按照已有文献提出的塑性设计方法,设计一个10层混合式STF结构进行对比分析,设计目标是在两个结构设计条件相同且含钢率接近的情况下,使两种结构都能充分发挥消能段的耗能能力。对设计的两个试件分别采用振型分解反应谱法和Pushover方法对比分析其承载力以及抗震性能。
有限元分析结果表明:在多遇地震作用下,构件均能保持弹性;在罕遇地震作用下,消能构件可以充分耗散地震能量,保护延性区段外构件不会破坏;STF试件的塑性铰集中在空腹节间的端部,沿楼层分布较均匀;TSCSP-STF试件的塑性铰主要出现在消能段的拉、压支撑杆上,分布也比较均匀;根据塑性设计方法设计的TSCSP-STF结构和混合式STF结构均能满足GB 50011—2010《建筑抗震设计规范》关于罕遇地震下对承载力、变形和稳定性的要求,而试件TSCSP-STF的层间位移分布得更为均匀,减小了薄弱层出现的可能性,延性相对更好。-
关键词:
- 两边连接钢板 /
- 交错桁架 /
- Pushover方法 /
- 抗震性能
Abstract: The staggered truss framing (STF) structural system is an efficient, practical and highly economical framing system, and it follows the trend of building industrialization. The STF structural system has been widely used in areas of low earthquake risk, and the merits make this system attractive in moderate to high seismic regions. The truss can be a hybrid truss, a vierendeel truss or a pratt truss. Compared with the vierendeel truss and the pratt truss, the hybrid truss is the most widely used because of its moderate rigidity and its vierendeel panel which can be set as an inner corridor. Existing tests have shown that the hybrid STF structural system has good mechanical performance but poor seismic performance and weak energy consumption capacity, and the soft storey problem is prone to occur. To enhance the seismic behaviour of STF structural systems, this paper proposed a ductile STF structure in which two-side connecting steel plates (TSCSPs) are set in the middle of the truss span and the middle span is taken as an energy dissipation section to dissipate energy. The ductile STF structure is called the two-side connecting steel plate-staggered truss framing (TSCSP-STF) structure. The steel plates of energy dissipation section would not buckle nor yield under frequent earthquakes, while only the steel plates would yield and dissipate energy under major and infrequent earthquakes. The non-dissipative sections of the truss remain elastic. In this way, the ductility and energy dissipation capacity of the traditional hybrid STF structure can be improved, and the instability and brittle failure of the web members can be mitigated or avoided.
The calculation method for the shear capacity demands of the TSCSP was derived from analyzing the shear capacity demands of the energy dissipation section. Assuming TSCSP as eccentric cross brace, we established a simplified analysis model of the TSCSP-STF structure, and then the plastic design method and process of the system. Further, a 10-story TSCSP-STF structure and a 10-story hybrid STF structure were designed with the same design conditions and nearly the same steel consumption. The design goal was to make both structures deplete the energy consumption capacity of the energy dissipation section. The seismic behaviours of the two specimens were investigated by the mode-superposition response spectrum method and Pushover analysis method.
The analysis results showed that:under the action of frequent earthquakes, the components can maintain elasticity, while under the action of major and infrequent earthquakes, the energy dissipation components can fully dissipate the seismic energy and protect the other components from damage. The plastic hinges of STF specimen were concentrated at the ends of vierendeel chords, and evenly distributed along the height of the building. The plastic hinges of TSCSP-STF specimen mainly appeared on the ties and struts of the energy dissipation sections, and the distribution was also relatively uniform. Both the TSCSP-STF structure and the hybrid STF structure designed according to the plastic design method can meet the requirements of the code for load-carrying capacity, deformation and stability under major and infrequent earthquakes. The drift of TSCSP-STF specimen was more uniformly distributed, reducing the possibility of soft-story, and has relatively better ductility. -
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