钢—混凝土组合桁架梁抗弯性能研究

发布时间：2018-08-05 11:39

【摘要】：钢-混凝土组合桁架梁是由钢桁架与混凝土板组合而成的受弯构件，这种组合梁具有优越的空间利用性能和显著的工程经济效益。钢-混凝土组合桁架梁目前在我国的研究还处于起步阶段，相关的理论和试验研究尚欠不足，尤其是缺乏适合我国工程设计需要的组合桁架结构承载性能及设计方法的研究。由于钢-混凝土组合桁架梁类型多样，受力性能亦较复杂，论文选取结构形式相对典型，在我国部分地区已开始初步使用的圆钢管组合桁架梁为研究对象，通过试验研究、有限元数值模拟、参数分析以及理论推导，研究钢-混凝土组合桁架梁的抗弯承载性能及其影响因素。论文首先采用试验方法研究了钢-混凝土组合桁架梁的抗弯承载能力。设计了4根编号为CB1、CB2a、CB2b和CB3的钢-混凝土组合桁架梁试件进行抗弯试验，详细介绍了试件单调加载静力试验的全过程情况，包括组合梁的破坏形态、变形性能、控制截面应变、滑移等。以CB2b试件为例，分析了混凝土受压翼缘板的应变及应力分布、荷载-挠度曲线以及抗弯极限承载力的变化特点。试验结果表明：钢-混凝土组合桁架梁的整个截面应变基本符合平截面假定；钢-混凝土组合梁的混凝土受压翼缘存在较明显的剪力滞后效应；钢-混凝土组合桁架梁具有较高的受弯承载能力和一定的延性性能。在试验研究的基础上，论文以4个试件为例分别建立了符合工程实际的钢-混凝土组合桁架梁的有限元模型。通过计算分析，了解了组合桁架梁的应力变化特点、组合梁的荷载-位移关系、荷载-滑移关系以及组合桁架梁的极限承载力，并与试验结果进行了对比。分析表明：从弹性刚度来看，4个试件有限元计算的弹性刚度均大于试验弹性刚度；从承载力来看，有限元得到的构件极限承载力与试验结果较接近，变形性能与试验结果基本吻合。为了便于设计应用，论文对钢-混凝土组合桁架梁受压混凝土翼板的有效宽度进行了大量的计算分析，并将分析结果与我国现行钢结构设计规范有关组合梁有效宽度的规定做了比较。论文对上述4个组合桁架梁试件混凝土翼板的应力分布情况分析表明：组合桁架梁在荷载作用下，随着作用荷载的增加，有效宽度系数变化较为复杂，但总体上呈增大的趋势。当其他条件不变时，组合梁的宽跨比（b/l）越大，有效宽度系数e越小。增大组合梁混凝土翼板宽度时，混凝土板上的应力分布不均匀程度会增大，剪力滞后效应加剧。因此，设计计算时应适当限制组合梁的宽跨比（b/l），使混凝土翼板充分发挥承载能力。设计计算时，如对梁的宽跨比不加区分，完全按照钢结构设计规范的规定取值，则有可能高估宽跨比较小的组合梁的极限承载力，导致偏于不安全的结果。在极限承载力状态下，组合桁架梁有效宽度的计算结果不低于现行钢结构规范的取值，对于不同高跨比的钢-混凝土组合桁架梁，设计计算时，可以完全按照钢结构设计规范的规定取值，计算组合梁的极限承载力。为了便于设计应用，论文最后还给出了便于工程应用的有效宽度简化计算公式。论文对组合梁的混凝土板厚度和宽度、腹杆截面尺寸、桁架梁上弦托板宽度以及栓钉抗剪连接程度等参数进行了分析，研究这些设计参数对组合桁架梁抗弯性能的影响特点。研究表明：当其他参数不变时，组合梁腹杆截面径厚比增加时，组合梁的初期刚度、后期刚度以及极限承载力均无明显变化。因此设计时适当考虑采用较厚且较宽阔的混凝土翼板，既可以提高组合梁承载力又能改善组合梁的变形性能。另外，上弦托板的宽度和栓钉抗剪连接程度都会在一定范围内提高组合梁的承载能力。为能从理论上更好地把握组合桁架梁的抗弯性能，论文推导了钢-混凝土组合桁架梁受弯承载力理论分析的基本假定和计算公式，总结组合桁架梁极限承载力的实用计算方法并与试验研究和有限元分析得到的数据结果进行了对比。研究表明：对于部分抗剪连接的桁架组合梁（CB1），有限元计算值和理论值几乎一致，而试验值比理论值偏小5%。对于完全抗剪连接的桁架组合梁（CB2a、CB2b和CB3），试验值比理论值平均偏大7%，有限元计算值比理论值偏大约19%。可见设计时采用理论推导的实用公式是偏于安全的。论文提出了一种新型双钉头型栓钉剪力连接件形式，，并进行了推出试验有限元模拟分析，在此基础上讨论了影响新型栓钉连接件抗剪承载力的主要因素，并结合有关规范公式提出了设计建议，最后还分析了采用新型栓钉的钢-混凝土组合桁架梁的抗弯承载力。研究表明：当其他参数不变时，采用新型栓钉的组合梁极限承载力明显提高，后期刚度有所提高，变形能力显著增强。
[Abstract]:Steel concrete composite truss beams are flexural members composed of steel trusses and concrete plates. This composite beam has superior spatial utilization performance and significant engineering economic benefits. The research of steel concrete composite truss beams in China is still in its infancy, and the related theory and test research are still insufficient, especially the lack of it. Study on bearing capacity and design method of composite trusses suitable for engineering design in China.
Because of the variety of the steel and concrete composite truss beam and the complicated force performance, the paper selects the structure form relatively typical. The circular steel tube composite truss beam which has been initially used in some areas of our country is the research object. Through the experimental study, the finite element numerical simulation, the parameter analysis and the theoretical deduction, the steel concrete composite truss is studied. Bending bearing capacity of beam and its influencing factors.
In this paper, the flexural bearing capacity of steel concrete composite truss beam is studied by experimental method. 4 steel concrete composite truss beams, named CB1, CB2a, CB2b and CB3, are designed for bending test. The whole process of monotonic loading test is introduced in detail, including the failure form, deformation performance and control of the composite beams. In the case of CB2b specimen, the strain and stress distribution, load deflection curve and flexural ultimate bearing capacity of concrete compression flange are analyzed. The experimental results show that the whole section strain of steel concrete composite truss beam is basically conformed to the assumption of flat section; and the coagulation of steel concrete composite beams is coagulated. There is obvious shear lag effect on the compressed flange of soil, and the steel-concrete composite truss beam has higher flexural bearing capacity and certain ductility.
On the basis of the experimental research, the finite element model of the steel concrete composite truss beam which is in line with the engineering practice is set up with 4 specimens as an example. Through the calculation and analysis, the stress variation characteristics of the composite truss beam, the load displacement relation of the composite beam, the load slip relation and the ultimate bearing capacity of the composite truss beam are obtained. The results of the test are compared. The analysis shows that the elastic stiffness of the finite element calculation of the 4 specimens is greater than the elastic stiffness from the elastic stiffness. From the bearing capacity, the ultimate bearing capacity of the finite element is close to the test results, and the deformation performance is in agreement with the experimental results.
In order to facilitate the design and application, the effective width of the compression concrete wing plate of the steel concrete composite truss beam is calculated and analyzed. The analysis results are compared with the provisions of the current steel structure design specification of our country on the effective width of the composite beams. The stress of the concrete wing plate of the 4 composite truss beams is analyzed in this paper. The analysis of cloth situation shows that the effective width coefficient changes more complicated with the increase of loading load on the composite truss beam, but on the whole it is increasing. When the other conditions are constant, the wider span ratio (b/l) and the effective width coefficient e are smaller when the other conditions are constant. The uneven degree of force distribution will increase and the shear lag effect intensifies. Therefore, the width span ratio (b/l) of the composite beam should be limited in design and calculation to make the concrete wing board fully play the bearing capacity. In the design calculation, if the width span ratio of the beam is not distinguished, it is possible to overestimate the wide span and span according to the specification of the steel structure specification. The ultimate bearing capacity of composite beams leads to unsafe results. In the state of ultimate bearing capacity, the calculation results of the effective width of the composite truss beam are not less than the values of the existing steel structure specifications. For the design and calculation of the steel concrete composite truss beams with different high span ratio, the design calculation can be taken according to the specification of the steel structure design specification. The ultimate bearing capacity of composite beams is calculated. In order to facilitate the design and application, a simplified formula for calculating the effective width of composite beams is given.
The paper analyzes the thickness and width of the concrete slab of the composite beam, the section size of the abdominal rod, the width of the upper chord plate of the truss beam and the shear connection degree of the stud, and studies the influence characteristics of these design parameters on the flexural performance of the composite truss beam. There is no obvious change in the initial stiffness, late stiffness and ultimate bearing capacity of the composite beams. Therefore, the proper consideration of the use of a thicker and wider concrete wing plate in the design can not only improve the bearing capacity of the composite beams but also improve the deformation performance of the composite beams. In addition, the width of the upper chord plate and the shear connection degree of the stud can be in a certain range. The bearing capacity of the composite beam is improved.
In order to better grasp the flexural performance of the composite truss beam theoretically, the basic hypothesis and calculation formula of the theoretical analysis of the flexural bearing capacity of the steel-concrete composite truss beam are derived, and the practical calculation method of the ultimate bearing capacity of the composite truss beam is summarized and compared with the data obtained from the experimental study and the finite element analysis. The results show that for the truss composite beams (CB1) with partial shear connection, the calculated values are almost the same as the theoretical values, and the test values are smaller than the theoretical values 5%. for the fully shear connection truss composite beams (CB2a, CB2b and CB3), the experimental values are 7% larger than the theoretical values, and the finite element calculation value is about 19%. to the theoretical value of the visual design. The practical formula for derivation is partial to safety.
In this paper, a new type of double nail head type stud shear connector is proposed, and the finite element simulation analysis is carried out. On this basis, the main factors affecting the shear bearing capacity of the new type stud connector are discussed, and the design suggestions are put forward with the relevant standard formulas, and the steel concrete group with new studs is analyzed at the end of the paper. The study shows that the ultimate bearing capacity of composite beams with new studs is obviously improved when the other parameters are constant, and the later stiffness is improved and the deformation capacity is greatly enhanced.
【学位授予单位】：郑州大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU398.9

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