冷弯型钢-秸秆草砖结构体系抗震性能研究

Study on Seismic Performance of Cold-Formed Steel-Straw Bale Structure System

冷弯型钢结构体系具有构件轻量化、全装配施工(施工现场无需大型机械)、连接快捷简便、安全可靠的特点,适合乡村低多层建筑的建造。秸秆建筑是高能效的建筑型式,可以为居住者营造贴近自然、舒适的室内环境,同时具有节能减排的良好效果,当建筑物被废弃时,秸秆也可以被生物降解。由于秸秆储量丰富,具有固碳能力,逐渐成为受到关注的绿色建筑材料。传统冷弯型钢结构体系中,平台式层间连接的构造复杂,连接强度和刚度较弱,易于破坏;侧挂式层间连接时,墙架柱承受楼层梁传来的附加弯矩而易于局部屈曲。矿物棉、泡沫聚苯乙烯、挤塑聚苯乙烯等围护材料生产能耗高,费用高,难于广泛用于乡村建筑。为此,将冷弯型钢结构体系与秸秆建筑相结合,并对平台式冷弯型钢结构体系进行改进,提出平台式-贯通式冷弯型钢-秸秆草砖结构体系,该体系符合绿色建筑和低能耗的建筑需求,在农村地区具有独特的优势和较大的发展空间。为考察该体系在地震作用下的抗震性能,以实际工程为背景,分别建立平台式冷弯型钢结构、平台式-贯通式冷弯型钢结构、平台式-贯通式冷弯型钢-秸秆草砖结构有限元模型,得到三者的自振频率,并分别对3种结构进行地震动的非线性时程分析,对比分析了3种结构在不同地震作用下的地震反应,包括加速度响应、位移响应、底部剪力-顶部位移曲线等。由实际工程的建造过程可以看出,相较于平台式冷弯型钢结构,平台式-贯通式冷弯型钢结构构件数量少,节点构造简单,安装方便,整体性好,适合在农村地区应用;平台式-贯通式结构的前三阶自振频率均大于平台式冷弯型钢结构,在最不利地震动荷载工况下,其峰值基底剪力、峰值屋面位移、峰值层间位移均小于平台式冷弯型钢结构,结构的最大层间位移角满足JGJ 227-2011《低层冷弯薄壁型钢房屋建筑技术规程》和GB 50011-2010《建筑抗震设计规范》的限值要求,表明平台式-贯通式冷弯型钢结构的整体刚度和抗震性能均优于平台式冷弯型钢结构;考虑秸秆墙体的影响后,平台式-贯通式冷弯型钢结构的峰值基底剪力减少约12.5%,峰值屋面位移减小约30%,表明秸秆墙体黏弹性的力学特性能够减轻冷弯型钢结构的地震响应。

The cold-formed steel(CFS)structure system features lightweight components,fully assembled construction,and no need for large machinery on the construction site.It is connected with self-tapping screws,which is fast,simple,safe,and reliable.The CFS structure system is suitable for the construction of low and multi-story rural buildings.The cold-formed steel(CFS)structure system has the characteristics of lightweight components,fully assembled construction(without the need for large machinery at construction site),fast and simple connection,safety and reliability,and is suitable for the construction of low and multi-story buildings in rural areas.Straw building is a highly energy-efficient building type,which can create a natural and comfortable indoor environment for residents,and has a good effect of energy saving and emission reduction.When the building is abandoned,the straw can also be biodegraded.Straw is rich in reserves and has the ability to sequester carbon,which has gradually become a green building material that has attracted attention.In the traditional CFS structure system,the platform inter-story connection is complicated,with weak connection strength and stiffness,and is prone to failure.The ledger-framed inter-story connection is prone to local buckling,as the studs bear the additional bending moment transmitted by the floor joists.The enclosure materials such as mineral wool,expanded polystyrene,extruded polystyrene are difficult to be widely used in rural buildings due to high energy consumption and high cost in the production.This paper proposed a platform-balloon type CFS-straw bale structure system,which combined CFS with straw bale and improved the platform CFS structure.This system meets the needs of green buildings and low energy consumption,and has unique advantages and large development space in rural areas.In order to investigate the seismic performance of the structure system subjected to earthquake,the finite element models of platform CFS structure,platform-balloon CFS structure,and platform-balloon CFS-straw bale structure were established respectively based on the actual project,and the natural frequencies of the three were obtained.The nonlinear time-history analysis of ground motion was carried out,and the seismic responses of the three subjected to different levels of earthquake were compared,including acceleration response,displacement response,and base shear-top displacement curve.It can be seen from the construction process of the actual project that compared with the platform CFS structure,the platform-balloon CFS structure has fewer components,simple joint configuration,convenient installation and good integrity,which is suitable for application in rural areas.The first three natural frequencies of platform-balloon CFS structure are higher than those of the platform CFS structure.Under the most unfavorable ground motion,the peak base shear force,peak roof displacement,and peak inter-story displacement of platform-balloon CFS structure are smaller than those of platform CFS structure,and the maximum inter-story drift of the structure meets the limit requirements of the code JGJ 227—2011"Technical Specification for Low-rise Cold-fromed Thin-walled Steel Buildings"and GB 50011—2010"Code for Seismic Design of Buildings".Those results indicate that the structural stiffness and seismic performance of the platform-balloon CFS structure are better than those of the platform CFS structure.Considering the influence of the straw wall,the peak base shear and peak roof displacement of the platform-balloon CFS structure are reduced by 12.5%and 30%respectively,indicating that the viscoelastic mechanical properties of straw wall can reduce the seismic response of CFS structure.