Transformation of Singular Joint Deformations in Concrete Elements into Plural Cracks

混凝土构件中单一节点变形转化为多重裂缝

• 批准号: 511403551
• 负责人: Professor Dr.-Ing. Rolf Breitenbücher
• 金额: --
• 依托单位: Institut für Massivbau
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/511403551?language=en
• 关键词: Transformation; Singular; Joint; Deformations; Concrete

Joints are integral part of slab-shaped concrete components, e.g. industrial areas, parking and traffic areas, retaining walls, etc., in order to avoid undesired cracking. Thermally or hygrically induced deformations in the concrete component are concentrated in these joints. Simultaneously, joints must be tight. The durability of conventional joint sealants is limited to only a few years, resulting in high maintenance costs. Therefore joints are inherent weak points in this system. In the research project applied, an alternative concept shall be investigated in which the joints in unreinforced / only weakly reinforced concrete components are covered with thin, carbonreinforced concrete layers (CRC). The basic idea is that the relatively large singular joint movements in the base component are converted into plural, considerably smaller cracks in the covering layer. Such thin CRC-layers are subjected to special stresses in this application, both in the axial direction due to the joint movement and perpendicular to it, e.g. due to earth pressure or traffic loads. For this purpose, the bond must be interrupted at both sides of the joint for a defined distance in order to create corresponding expansion ranges in which the fine cracks can develop. In order to evaluate the suitability of such CRC-layers for bridging joints, on the one hand the crack development in CRC-layers at correspondingly high straining, and on the other hand the bond behaviour of this layer on the base component under the relevant exposures shall be investigated. It should be taken into account that the stresses in such slabs / layers are of two-axial nature and that tensile as well as compressive stresses can occur in the CRC-layer as a result of the joint movements. In concrete terms, following studies are intended: • At the CRC layers: – Load-bearing and deformation behaviour of CRC-layers under biaxial tensile and compressive stresses – Modelling of the biaxial bond between carbon reinforcement and concrete • At the composite system in the joint area: – Formation of micro-cracks in the CRC-layer in composite bodies under tensile stress (opening joint) with variations in bond braking – Stability of the CRC-layer under compressive stress (closing joint) with variations in bond braking – Risk of progressive delamination in case of cyclic stresses in this area.

接缝是板状混凝土构件的组成部分，例如工业区、停车场和交通区、挡土墙等，以避免混凝土构件中的热或湿引起的变形集中在这些接缝中。传统接缝密封剂的耐用性仅限于几年，因此维护成本很高，因此在该系统的研究项目中采用了替代方案。应研究这样的概念，其中无筋/仅弱筋混凝土构件中的接缝被薄的碳纤维混凝土层（CRC）覆盖。其基本思想是将基础构件中相对较大的单一接缝运动转换为多个、相当小的接缝运动。在这种应用中，这种薄的 CRC 层会因接头运动而在轴向上受到特殊的应力，例如由于土压力或交通载荷。必须在接头两侧中断一定的距离，以产生相应的扩展范围，在该范围内可以形成细裂纹。为了评估此类 CRC 层对于桥接接头的适用性，一方面， CRC 层在相应高应变下的裂纹发展，另一方面，应研究在相关暴露下该层在基础部件上的粘合行为，应考虑到此类板/层中的应力。双轴性质由于接头运动，CRC 层中可能会产生拉应力和压应力。 具体而言，旨在进行以下研究： • 在 CRC 层： – CRC 层在其作用下的承载和变形行为。双轴拉伸和压缩应力 – 碳纤维增强材料和混凝土之间的双轴粘合建模 • 在接头区域的复合材料系统中： – 在变化的拉伸应力（开口接头）作用下，复合材料体的 CRC 层中形成微裂纹粘合制动 – CRC 层在压应力（闭合接头）下的稳定性，随着粘合制动的变化 – 在该区域出现循环应力的情况下存在逐渐分层的风险。