Computational investigation of the behavior of precast hybrid beam-column connections

The objective of this research is to study the behavior of the joint systems in precast hybrid frames. 3-D nonlinear finite element (FE) model was developed to study the response and predict and validate experimental results for a 1/3 scale model of a prototype precast concrete building subjected to cyclic loads. The experiments were conducted at the National Institute of Standards and Technology (NIST) (PRESSS program).; The low-cycle fatigue behavior of ASTM A706 and ASTM A615 Grade 60 deformed reinforcing steel bars used at the joints was studied experimentally and analytically. Although this study was initiated to evaluate the low-cycle fatigue of reinforcing bars in precast hybrid frame connections, the conclusions presented here also apply to other relevant applications. Tests were performed under strain-controlled cyclic axial loading with non-zero mean strains. The deformed bars were subjected to constant-amplitude sinusoidal strains ranging from zero to peak strains that varied between 2% and 8% in different tests. All tests were performed on unmachined bar specimens. This study demonstrated that the low-cycle fatigue responses of A706 and A615 mild steel bars were similar even though their monotonic ductility ratios were very different. The proposed low-cycle fatigue relationships for both A706 and A615 mild steel bars could be used to calculate maximum permissible strains in applications such as precast hybrid frames. The prediction of bar fracture due to low-cycle fatigue is believed to be an important consideration in the design of precast hybrid frames, but is currently not being considered in design.; Simplified design procedures for precast hybrid frames were developed. A set of new non-dimensional parameters and procedures for the design of hybrid frame were developed. Parametric studies were performed using the developed non-dimensional formulation. These involved solving optimization problems to achieve zero residual drift while ensuring that the moment capacity of the section is equal to the applied design moment. The results of these studies were used to generate non-dimensional design charts and simplified equations. Design examples representing low and high seismic zones were developed in detail. The results of PRESSS procedures, proposed design charts, and proposed design equations were compared. Very close agreement was found in all cases. (Abstract shortened by UMI.)...