用弹性及非弹性分析识别现浇板对钢筋混凝土梁的增强效应

发布时间：2018-04-28 21:35

本文选题：强柱弱梁 + 现浇楼板　；参考：《重庆大学》2014年硕士论文

【摘要】：我国的抗震规范利用“能力设计”原理来保证按多遇水准地震效应设计的结构在更高水准地震作用下的抗震性能。“强柱弱梁”这一抗震措施就是“能力设计”原理在工程设计中的应用之一。 “强柱弱梁”的目的是使框架结构在强震下形成具有较好抗震性能的稳定的屈服后塑性耗能机构，并避免结构形成同层所有柱端均同时出现同一转动方向塑性铰的层侧移机构。然而，实际震害表明，受到不同程度损伤或损毁的钢筋混凝土框架结构，几乎全是以柱端塑性铰区的形式出现。与纵向梁平行的现浇楼板钢筋会参与抵抗负弯矩，这就使得现行的梁板分离式设计严重低估了梁端实际抗负弯矩能力，这是“强柱弱梁”的目的不能实现的重要原因之一。国内外众多研究者对这一问题进行了试验或模拟分析研究，提出了用有效翼缘宽度来量化现浇板钢筋对梁端负弯矩承载力的增强效应，但有效翼缘宽度的建议取值方案不尽相同。这些研究部分是对带现浇楼板的节点进行试验或数值模拟，然而，节点不具有实际框架中板的边界约束条件，故以此来定量研究梁板协同工作是不可取的。以框架结构为对象的研究中，只有少量研究者采用试验方法或用三维实体单元对其进行精细化的非弹性模拟分析，但是这些研究者提出的有效翼缘宽度取值方案都不尽完善，或是没有考虑足够的节点类型，或是没有考虑诸如梁跨度和梁截面高度这类因素的影响。目前，我国工程设计界对有效翼缘宽度的取值没有统一的标准，，该问题还处于研究阶段。针对上述实际情况，本论文在阅读了大量文献的基础上，采用三维实体单元（模拟混凝土）和三维桁架单元（模拟钢筋）对水平荷载作用下的框架结构进行精细化的弹性及非弹性分析。本论文的主要工作及成果简述如下： ①运用ABAQUS程序对带楼板和无楼板钢筋混凝土单层单跨空间框架结构进行弹性分析，并且对比分析结果。结果表明，现浇楼板增强了框架结构抵抗水平位移的能力，并且增强了纵向梁的抗弯刚度和抗弯强度。针对带楼板的框架结构，改变其现浇楼板厚度、混凝土强度等级、纵向梁刚度和横向梁刚度，通过与原结构对比楼板钢筋的应变来研究这些因素对板筋参与梁端抗弯程度的影响。得到结论，纵向梁刚度对板筋参与梁端抵抗负弯矩的程度影响最大，其次是横向梁刚度，再次是楼板厚度，最后是混凝土强度等级（只提高一级），并且这几个因素的影响方式也各不相同。 ②运用ABAQUS程序对带楼板和无楼板钢筋混凝土单层单跨空间框架结构进行非弹性分析，并且对比分析结果。结果表明，现浇楼板增强了框架结构抵抗水平位移的能力，也增强了纵向梁的抗弯刚度和抗弯强度，特别是增强了梁负弯矩区的抗弯强度，并且这种增强效应在结构受力响应的非弹性程度越深的时候表现得越明显。所以，现浇楼板对框架梁乃至整个框架结构的影响是不容忽视的。 ③针对带楼板的单层单跨空间框架结构，详细研究结构不同水平位移下楼板钢筋应力的横向（垂直于水平荷载作用方向）分布。结果表明，楼板钢筋的应力随着与纵向梁距离的增大而减小，板顶钢筋的拉应力整体上比板底钢筋的大，楼板钢筋的应力在整体上随结构水平位移的变大而增大，当结构的层间位移角达到1/35，楼板钢筋的应力整体上趋于稳定。 ④将ABAQUS的分析模型从单层单跨空间框架结构扩展到包含更多节点类型的单层两跨空间框架结构，继而发展到涵盖所有常见节点类型的两层两跨空间框架结构。得到不同结构中不同节点处楼板钢筋应力的分布规律。通过对比这些规律可知，节点类型对楼板钢筋应力的大小及分布影响较大，即对有效翼缘宽度的影响较大，应该将分析模型选定为包含节点类型全面的结构。 ⑤针对两层两跨空间框架结构，通过改变其纵向梁跨度和截面高度来研究这两个因素对有效翼缘宽度的影响。结果表明，随着纵向梁跨度的增加，有效翼缘宽度增大；纵向梁截面高度对有效翼缘宽度的影响没有较好的规律。于是，将纵向梁跨度作为基本参数来描述结构层间位移角为1/35时各节点的有效翼缘宽度。
[Abstract]:The seismic behavior of our country uses the principle of " ability design " to guarantee the seismic behavior of the structure under the action of higher standard seismic effect . The seismic design of " strong column weak beam " is one of the application of " capability design " principle in engineering design .

The purpose of the " strong column weak beam " is to make the frame structure form a stable yielding plastic energy dissipation mechanism with better seismic performance under strong earthquake , and to avoid the formation of the lateral displacement mechanism of plastic hinge at the same time . However , the actual earthquake damage indicates that the reinforced concrete frame structure with different degree of damage or damage appears in the form of plastic hinge area at the end of the column . The cast - in - place floor steel bar parallel to the longitudinal beam can participate in the resistance to negative bending moment , which makes the existing beam plate separation design seriously undervaluation the actual negative bending moment capacity of the beam end , which is one of the important reasons why the purpose of the " strong column weak beam " cannot be realized .

In this paper , it is not advisable to quantify the bearing capacity of cast - in - place slabs with effective flange width . However , it is not advisable to quantify the effective flange width .

In view of the above - mentioned practical situation , this paper is based on a large number of literatures , and adopts three - dimensional solid unit ( simulated concrete ) and three - dimensional truss unit ( simulated steel bar ) to carry out fine elastic and inelastic analysis on the frame structure under the action of horizontal load . The main work and results of this paper are as follows :

The results show that the cast - in - place floor slab enhances the frame structure ' s ability to resist horizontal displacement and enhances the flexural rigidity and bending strength of the longitudinal beam .

The results show that the cast - in - place floor slab enhances the flexural rigidity and bending strength of the longitudinal beam , especially the bending strength of the beam negative bending moment area , and the reinforcement effect is more obvious when the non - elastic degree of the structural stress response is deeper . Therefore , the influence of the cast - in - situ floor on the frame beam and the whole frame structure cannot be ignored .

( 3 ) According to the single - layer single - span spatial frame structure with floor slab , the transverse ( perpendicular to horizontal load acting direction ) distribution of the floor steel bar stress at different horizontal displacement is studied in detail . The results show that the stress of the slab reinforcement decreases as the distance from the longitudinal beam increases , and the stress of the reinforced bar of the slab increases as the displacement of the horizontal displacement of the structure increases . When the displacement angle between the layers of the structure reaches 1 / 35 , the stress of the floor steel bar is stabilized .

In this paper , the analysis model is extended from single - layer single - span spatial frame structure to single - layer two - span spatial frame structure containing more node types , which is then developed to two - layer two - span spatial frame structure covering all common node types .

The influence of these two factors on the effective flange width is studied by changing its longitudinal beam span and cross section height for two - layer two - span spatial frame structure . The results show that the effective flange width increases with the increase of the span of the longitudinal beam ;
The effect of the longitudinal beam cross - section height on the effective flange width is not good . Then , the longitudinal beam span is used as the basic parameter to describe the effective flange width of each node when the displacement angle between the structural layers is 1 / 35 .

【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU375.1

【参考文献】