钢-混凝土组合扁梁受弯性能理论分析与试验

Theoretical Analysis and Experimental Study on Bending Behavior of Steel-Concrete Composite Flat Beams

钢-混凝土组合扁梁楼盖以其楼盖结构高度小、防火性能好、下表面平整观感好、便于管线铺设以及在经济跨度范围内梁高更小的优势,在国外(特别是英国和北欧地区)得到了较广泛的应用。实际工程中,钢-混凝土组合扁梁楼盖应用较多的是SP预应力混凝土叠合楼板和深肋压型钢板组合楼板,用于住宅建筑时,存在以下不足:1)钢梁下翼缘外露,需要进行防腐防火保护;2)深肋压型钢板组合扁梁下翼缘不平整需做吊顶,增加了成本和结构高度;3)SP预应力混凝土叠合楼板和深肋压型钢板组合楼板均为单向板,导致楼盖厚度较大,且楼盖高度难以进一步降低等,制约了钢-混凝土组合扁梁楼盖在实际工程中的应用。为此,提出了预制叠合密肋楼板和预制叠合密肋楼板组合扁梁楼盖的概念,预制叠合密肋楼板由预制带肋底板和现浇层组成,可实现双向传力。由于该新型预制叠合密肋楼板组合扁梁楼盖区别于传统的SP预应力混凝土叠合楼板和深肋压型钢板组合扁梁楼盖,为研究该新型组合扁梁楼盖预制叠合密肋楼板与钢梁协同工作性能及其设计方法,结合某高层钢结构住宅示范工程的设计,对该新型钢-混凝土组合扁梁的受弯性能进行了理论分析与试验研究。设计制作了2个预制叠合密肋楼板组合扁梁试验试件,主要变化参数为钢梁腹板开孔形式和剪力键设置方式。钢梁采用焊接不等翼缘钢梁,楼板采用预制叠合密肋楼板,预制板均不出筋。钢材牌号为Q345B,楼板混凝土强度等级为C35,钢筋为HRB400级。试件计算长度为3 800 mm,几何长度为4 000 mm。通过试验研究该新型钢-混凝土组合扁梁的承载能力、延性、变形性能、裂缝开展、应力及应变发展情况等。在试验研究的基础上,提出了预制叠合密肋楼板组合扁梁抗弯极限承载力计算简化假定,并基于破坏强度理论推导了预制叠合密肋楼板组合扁梁抗弯极限承载力计算公式。通过理论分析和试验研究得到以下结论:1)预制叠合密肋楼板组合扁梁具有优良的承载能力和延性性能。试件挠跨比达到1/32时,试件承载力仍未有明显下降,试件呈延性破坏特征。2)在钢梁下翼缘边缘和受拉钢筋屈服时,试件达到屈服承载力;在钢梁全截面屈服、受拉和受压钢筋屈服、受压区混凝土压溃时,试件达到极限承载力。在峰值荷载之前,混凝土和钢梁截面应变分布近似呈线性分布,可以采用平截面假定。3)基于破坏强度理论提出的预制叠合密肋楼板组合扁梁的抗弯承载力计算公式,与试验结果吻合良好,且偏于安全。

The steel-concrete composite slim floor has the advantages of small height of the floor structure,good fire resistance,good appearance of the lower surface,easy pipeline laying,and smaller beam height in the economic span,and has been widely used in foreign countries(especially the United Kingdom and Northern Europe).The steel-concrete composite slim floor commonly used in the actual project is SP prestressed hollow slab and deep deck steel plate composite floor.When used in residential buildings,there are the following deficiencies:1)The lower flange of the steel beam is exposed,requiring anti-corrosion and fire protection.2)The uneven bottom flange of composite slim beam with deep deck needs to be suspended,which increases cost and structural height.3)SP prestressed hollow slab and deep rib profiled steel plate both are one-way slabs,which results in a large floor thickness,and it is difficult to further reduce the height of the floor,which restricts the application of the steel-concrete composite slim floor in practical projects.To this end,this paper presents the concept of prefabricated concrete hollow slab and composite slim beam with concrete hollow slab.The prefabricated concrete hollow floor is composed of prefabricated concrete hollow slab and cast-in-place concrete,which can achieve two-way force transmission.Because this new type of composite slim beam with concrete hollow slab is different from the traditional SP prestressed hollow slab and deep rib profiled steel plate.In order to study the cooperative working performance and design method of the new composite slim beam with concrete hollow slab,theoretical analysis and experimental study of the bending performance of the new steel-concrete composite slim beam with concrete hollow slab were carried out.In this paper,two specimens of composite slim beam with concrete hollow slabs were designed and manufactured.The main changing parameters were the opening pattern of steel beam webs and the settings of shear keys.The steel beams are welded unequal flange steel beams,and the floor slabs are prefabricated concrete hollow slab.The steel grade is Q345B,the floor concrete is C35,and the steel bar is HRB400.The calculated length of the test piece is 3800 mm,and the geometric length is 4000 mm.Through experiments,the bearing capacity,ductility,deformation performance,crack development,stress and strain development of the new steel-concrete composite flat beam were studied.On the basis of experimental research,a simplified assumption for the calculation of the ultimate bending capacity of prefabricated concrete hollow slab is proposed,and the calculation formula of the ultimate bending capacity of the prefabricated concrete hollow slab is derived based on the failure strength theory.The following conclusions were obtained through theoretical analysis and experimental research:1)The composite slim beam with concrete hollow slab has excellent bearing capacity and ductility.When the deflection span ratio of the specimen reaches 1/32,the bearing capacity of the specimen has not decreased significantly,and the specimen exhibits the characteristics of ductile failure.2)When the bottom flange of the steel beam and the tensile steel bar yield,the test piece reaches the yield bearing capacity;when the steel beam full-section yields,the tensile and compression steel bar yields,and the concrete in the compression zone collapses,the test piece reaches the ultimate bearing capacity.Before the peak load,the strain distribution of the concrete and steel beam sections is approximately linear,and the flat section assumption can be used.3)The calculation formula of the bending capacity of the composite slim beam with concrete hollow slab based on the failure strength theory is in good agreement with the test results and is safe.