MODELLING OF REALISTICALLY SIZED AND LOADED FRP CONFINED RECTANGULAR REINFORCED CONCRETE COLUMNS

该建议旨在开发一个实用的通用模型，用于分析使用frp加固的实际尺寸和荷载矩形柱。加固圆形混凝土柱可以通过包裹FRP（纤维增强聚合物）来实现。这限制了混凝土，并可能导致负载和应变能力增加超过100%。然而，大多数柱在横截面上是正方形或长方形的。主要在小型矩形柱上进行的试验表明，强度的增加幅度较小，但仍高达50%。基于这些小规模试验，已经开发了一些简单的经验模型来预测强度的增加。然而，由于尺寸效应，在试验中使用的柱的有限尺寸提供了很少的理由使用这些模型在实践中发现的较大尺寸的矩形柱。因此，为了提供可靠的行为模型，需要进行基本的调查。为了建立这样一个一般的行为模型，有三个基本问题没有得到很好的理解，也没有定义限制，因此需要解决；尺寸效应、纵横比和载荷偏心。矩形柱的约束是通过FRP中的应变在柱的角部产生力，从而产生有效的约束十字形区域。当FRP与柱表面之间的粘结破坏时，FRP不再有效地锚定在柱的两侧，最终必须从一个角落到另一个角落应变，导致大柱的约束力低于边长较小的小柱。出于类似的原因，还必须考虑宽高比。此外，随着宽高比的增加，已知约束的有效性降低。最后，大多数柱被偏心加载或有弯曲和轴向组合载荷。这导致截面上的应变分布不均匀，因此每个角落的围合力不相等，导致非十字形封闭区域。考虑到这三个问题，将通过对大型矩形柱进行一系列仪器和监测测试（与现有的小规模测试结果进行比较），以及定性有限元建模来确定有效受限区域形状的演变，从而确定其行为。这些信息，连同合适的粘结-应力-滑移和混凝土破坏模型，将用于开发基于行为力学的矩形柱强化分析模型，而不是通过拟合实验结果。

The proposal aims to develop a practical generalised model for analysing realistically dimensioned and loaded rectangular columns strengthened using FRPs. Strengthening circular concrete columns can be achieved by wrapping with FRP (fibre reinforced polymer). This confines the concrete, and can result in increases in load and strain capacity of over 100%. However, most columns are square or rectangular in cross section. Tests, mainly on small-scale rectangular columns, have shown a lower increase in strength, but still up to 50%. A number of simple empirical models have been developed to predict the increase in strength, based upon these small-scale tests. However, , due to size effect, the limited size of columns used in the tests provide little justification for using these models for the larger size rectangular columns found in practice. Thus, a fundamental investigation is required in order to provide a reliable model of behaviour. In order to establish such a general behavioural model there are three fundamental issues which are not well understood, nor limits defined, and therefore need addressing; size effect, aspect ratio and load eccentricity. Confinement of rectangular columns occurs by generating forces at the corners of the column through strain in the FRP, resulting in an effectively confined cruciform region. When the bond between the FRP and the face of the column breaks down, the FRP is no longer effectively anchored to the sides of the column and, ultimately, must strain from corner-to-corner resulting in lower confinement forces for large columns than for small columns with a small side length. For similar reasons, aspect ratio must also be considered. Additionally, as aspect ratio increases, the effectiveness of confinement is known to reduce. Finally, most columns are loaded eccentrically or have combined bending and axial loads. This results in uneven strain distribution across the section and, therefore unequal confining forces at each corner, resulting in a non-cruciform confined area. The behaviour, considering these three issues, will be ascertained via a series of instrumented and monitored tests on large-scale rectangular columns (for comparison with existing small scale test results), together with qualitative finite element modelling to establish the evolution of the shape of the effectively confined area. This information, together with a suitable bond-stress-slip and concrete failure models, will be used to develop an analytical model for strengthening of rectangular columns based upon the mechanics of the behaviour rather than by fitting experimental results.