Shyamala G, Hemalatha B, Devarajan Yuvarajan, Lakshmi Chairma, Munuswamy Dinesh Babu, Kaliappan Nandagopal
Department of Civil Engineering, SR University, Warangal, India.
Department of Civil Engineering, St Peter's Institute of Higher Education and Research, Chennai, Tamilnadu, India.
Sci Rep. 2023 Oct 13;13(1):17392. doi: 10.1038/s41598-023-43882-5.
Beam-column joints are crucial load transmission zones because they face concentrated forces from both the beams and the columns. High shear and axial stresses caused by these concentrated forces in the area of the joint may result in decreased joint strength. This article proposes a new beam-to-column connection developed for precast concrete-resisting frames. Concrete mixtures are enhanced mechanically by adding nano silica as it increases compressive strength, flexural strength, and abrasion resistance. Within the concrete, it creates a solid, gel-like matrix that fills voids and strengthens the whole construction. In this study, three reinforced concrete beam-column joint specimens were cast with fly ash, the other three with nano-silica and fly ash, and one sample with nano-silica and a control mix without admixtures was cast. Specimen cast using fly ash and nano-silica is subjected to cyclic loading after 28 days of curing. A load capacity of 100 kN was imposed on the column during testing. It was observed that a gradual increase in fly ash decreased the compressive and flexural strength of the beam-column joints. This decrease in strength was addressed by adding 2.5% nano-silica. Nano silica acts as a nucleus to bond tightly with cement particles during hydration. The results showed that the flexural strength equivalent to that of a controlled specimen can be achieved by adding nano-silica at 2.5% and fly ash at 60%. The highest loading of 38.1 kN can be applied to the specimen with nano-silica without fly ash. Although a higher axial compression ratio can improve the bearing capacity and initial stiffness, it can also reduce deformation capacity and flexibility.
梁柱节点是至关重要的荷载传递区域，因为它们承受来自梁和柱的集中力。这些集中力在节点区域引起的高剪应力和轴向应力可能导致节点强度降低。本文提出了一种为预制混凝土抗震框架开发的新型梁与柱连接方式。通过添加纳米二氧化硅来机械增强混凝土混合物，因为它能提高抗压强度、抗弯强度和耐磨性。在混凝土内部，它形成一种固体的、凝胶状的基质，填充孔隙并增强整个结构。在本研究中，浇筑了三个掺粉煤灰的钢筋混凝土梁柱节点试件，另外三个掺纳米二氧化硅和粉煤灰，还浇筑了一个掺纳米二氧化硅的试件以及一个不掺外加剂的对照混合料试件。使用粉煤灰和纳米二氧化硅浇筑的试件在养护28天后进行循环加载。试验期间对柱施加100 kN的荷载。观察到粉煤灰用量的逐渐增加会降低梁柱节点的抗压和抗弯强度。通过添加2.5%的纳米二氧化硅解决了强度降低的问题。纳米二氧化硅在水化过程中作为核心与水泥颗粒紧密结合。结果表明，添加2.5%的纳米二氧化硅和60%的粉煤灰可实现与对照试件相当的抗弯强度。对于不掺粉煤灰的纳米二氧化硅试件，可施加高达38.1 kN的最大荷载。虽然较高的轴压比可以提高承载力和初始刚度，但也会降低变形能力和延性。
