STUDY OF HYSTERETIC BEHAVIOR OF COUPLING BEAMS USING FINITE ELEMENT MODELING

• Main Author: Tjahyadi Tjandra Lukas, Ferdy
• Format: Theses
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/55912
• Institution: Institut Teknologi Bandung

According to the design code of ACI 318-14, coupling beams with shear span less than 2.0 adopt diagonal reinforcement layout with each group of diagonal bars consist of a minimum of four bars in two or more layers, while coupling beams with intermediate span (2.0 ? ???????????????? ? 4.0) can adopt either diagonal or conventional layout. Coupling beams reinforced using diagonal layout provides higher ductility and capacity. However, the diagonally placed bars also create constructability problems, especially at the intersection of diagonal bars and special boundary element. The aim of this study is to identify the possibility to reduce the usage of diagonal bars in one group into a minimum of two bars in only one layer (partial layout). In order to achieve the main goal, this study consists of three parts, i.e., (1) modeling and verification of finite element, (2) investigation of the role of diagonal reinforcement and load transfer mechanism, and (3) identification of diagonal bars reduction using ACI 318-14 strut-and-tie method (STM). Eight reinforced concrete coupling beam specimens with different shear span and diagonal bars configuration available in the literature were studied and modelled using finite element. Concrete material behavior is modelled using concrete damaged plasticity with damage parameter input, while inelastic steel material behavior is modelled using kinematic hardening. Plane stress with reduced integration (CPS4R) was chosen as the element type of the model, neglecting its out of plane behavior. Finite element analysis was performed using ABAQUS Explicit/ CAE. The analysis shows that the ratio of stiffness and ultimate load of the model to the experimental results is quite close, with the range of the ratios being 0.95 – 1.35 and 0.83 – 1.22, respectively. Meanwhile the drift ratio at ultimate load and UDR of the model to the experiment has a lower value with the range of the ratios being 0.12 – 1.08 and 0.13 – 1.38, respectively. The cumulative energy dissipation of the model has a higher value than the experiment because it is assumed as fully embedded reinforcement, so that pinching and slip is neglected in the models. This assumption causes the value of the energy dissipation of models is always higher than experimental result, with the ratio always being more than 1. The analysis also shows that coupling beam with shear span of 1.0 develops a single diagonal direct strut, while coupling beams with shear span of 2.0 and 3.0 develop a diagonal fan strut as the load transfer mechanism.