Seismic assessment and strengthening of 3D beam-column joints

• Applicants: Dr.-Ing. Josipa Bosnjak; Professor Dr.-Ing. Harald Garrecht, since 1/2022
• Subject Area: Structural Engineering, Building Informatics and Construction Operation
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445697424

The primary goals of this project are (i) to develop practical and reliable models for realistic performance assessment of 3D beam-column joints of NSD structures while taking into account the influence of slabs and transverse beams, and (ii) to develop a low-invasive, high-effective strengthening solution for 3D beam-column joints and the corresponding models for their performance assessment. The existing research work has primarily been focused on the planar 2-dimensional beam-column joint sub-assemblies without considering the influence of transverse beams or slabs. Limited studies existing in literature clearly brought out the significant influence of slabs and transverse beam as well as bi-directional loading on the seismic performance of beam-column joints especially of NSD structures. For the strengthening of insufficient planar beam-column joints, fully fastened haunch retrofit solution (FFHRS) has been investigated by the applicant and other researchers and is shown to be a practically viable and effective strengthening method provided the fasteners used to connect the haunch element to the structural members perform well. The effectiveness of the retrofit solution is largely dependent on the relative stiffness of the connecting members, the haunch element and the stiffness of post-installed anchors. The participation of slab in a beam-column joint can significantly modify these relative stiffness values and therefore, the existing data on 2D joints is insufficient to develop a reliable strengthening solution. With the above-mentioned primary goals in sight, in this project, experimental investigations will be performed on full-scale beam-column joints to clearly and step-by-step bring out the influence of (i) transverse beam, (ii) monolithic slab, and (iii) bi-directional loading on the seismic performance of beam-column joints of NSD structures. Experiments will be augmented by a detailed numerical investigation and parametric study to quantify the influence of various parameters. Further experimental investigations on full-scale beam-column joints after strengthening using FFHRS will be carried out. However, tests will first be performed on anchorages under cyclic loading to: (i) identify the most suitable anchor type for connecting the haunch elements to frame members, and (ii) provide information on the load-displacement and hysteretic behavior of the anchors. A new displacement based protocol will be used for these tests. Based on the experimental and numerical investigations carried out within the framework of the project, multi-spring models will be developed that can be used for the performance assessment of as-built joints as well as the joints retrofitted with FFHRS while taking into account the influence of the slabs, transverse beam, bi-directional loading and anchorage behavior.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Akanshu Sharma, until 12/2021