In steel moment resisting frames, the region of the column located within the beam-column joint is known as the panel zone. When a steel moment resisting frame is subjected to lateral load, due to wind or seismic loads, the panel zone is subject to high shear. In some cases, the shear in the panel zone is sufficiently high that the panel zone must be reinforced to increase its stiffness and/or strength. This is normally accomplished by welding doubler plates to the column in the panel zone region. Doubler plates can be a costly feature in steel moment resisting frames because of the substantial amount of welding involved. There has been a large amount of past research that has investigated the required shear strength and stiffness of the panel zone region to establish a basis for sizing doubler plates. However, very little past research has investigated the details of attaching doubler plates to columns. These attachment details can have a significant influence on the structural performance of panel zone and on cost. The overall goal of this research was to conduct preliminary finite element studies that provide insight into several key issues related to the attachment of doubler plates to columns and to identify issues that require further research. The research involved finite element modeling of a simplified representation of beam-to-column joint subjected to monotonic loading. A total of twenty-one analysis cases with different doubler plate attachment details were studied. Issues that were investigated included the effect of welding different edges of the doubler plate to the column (horizontal edges only, vertical edges only, and all four sides), the effect of extending the doubler plate beyond the panel zone region, and the effect of providing two thinner doubler plates of equivalent total thickness on both sides of the column web instead of one thick doubler plate on one side of the column web. In addition, the forces developed in the doubler plate welds were computed from the finite element analysis and compared with current building code requirements for the design of these welds. Observations and preliminary design recommendations on these issues are provided in this thesis, along with recommendations for further research. / text

The effect of panel zone (PZ) flexibility and yielding on the stiffness and strength of steel moment resisting frames (SMRF) has been the topic of numerous papers over the past thirty years. When properly detailed, the PZ is an excellent source of energy dissipation, even under large inelastic deformations. Due to these large inelastic deformations, the PZ region may also be a weak link in steel moment frame behavior. Because of the importance of PZ deformation in the behavior of steel frames, accurate modeling of this region is critical. Two of the most commonly used mathematical models for representing PZ behavior are investigated. They are referred to herein as the Krawinkler model and the Scissors model. From the literature review conducted at the beginning of this study, it was determined that there were no PZ models available that accounted for the elastic drift associated with PZ flexure which could be used in computer representations using commercial software that is currently available. This thesis details the analytical work used to establish the estimated elastic drift associated with PZ flexure and a method to include this estimated drift and the contribution of continuity plates in the Krawinkler and Scissors models. This study is initially focused on elastic deformations of individual structural subassemblages. First, formulas are derived to account for each major elastic component of drift in an individual subassemblage. The results from these derivations were implemented into a computer program named PANELS to allow for rapid calculation of the estimated drifts. Then, the properties (elastic and inelastic) for the Krawinkler and Scissors models are derived in their entirety. The Krawinkler model's results are compared to the results from PANELS, neglecting the PZ flexural component in PANELS and any inelastic contributions in the Krawinkler model. Since the Krawinkler model does not include PZ flexure, this established that the derived formulas accounted for all the remaining sources of elastic strain energy, assuming that the Krawinkler model is accurate. The results from PANELS are compared to those from finite element models developed using ABAQUS. Using the ABAQUS results, a method for determining the elastic drift associated with PZ flexure in PANELS is presented. A detailed inelastic study of the Krawinkler and Scissors models is then conducted both on the subassemblage level and on full structural frames to determine any differences associated with them. First, the two models are compared to each other on a subassemblage level to ensure that they both give the same results. Then, both PZ models are included in multiple full structural frames using various design configurations and loading conditions to ascertain their differences. Initially it was believed that there would be a large disparity between the two models. This study shows that there is actually little difference between the two models, although the kinematics of the Scissors model is still questionable. Elastic and inelastic comparisons between the PANELS formulas (elastic) and the ABAQUS models (elastic and inelastic) and data collected from tests performed at Lehigh University by Dr. James Ricles are then presented. This was done to show that the ABAQUS models and the PANELS formulas (including the PZ flexural component) give an accurate estimation of the drift of a subassemblage. The results from these comparisons show that the modeling techniques used are accurate and not including PZ flexural component of drift will cause the overall drift estimate to be unconservative. Finally, a method of including the elastic component of drift attributed to PZ flexure and continuity plates in both models is presented. The Ricles' Lehigh test data is again used in an inelastic comparison between the original Krawinkler and Scissors models and their updated counterparts. These comparisons show that including this component enables both the Krawinkler and Scissors models to more accurately estimate the total drift of an individual subassemblage. / Master of Science

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22431号 / 工博第4692号 / 新制||工||1732(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 大崎 純, 教授 西山 峰広, 准教授 聲高 裕治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Panel zone is one of the significant parts of beam-column connections in steel structures. Until the 1994 Northridge Earthquake, a few experimental research and parametric studies had been carried out to understand the behavior of the panel zones. However, after the Northridge Earthquake, it was observed that beam-column connections were unable to show presumed seismic performance. Therefore, current design codes needed to be revised to improve seismic performance of connections in general and panel zones in particular. In this research, panel zone deformation demands are examined using explicit three dimensional finite element models and considering different parameters. For this purpose, a frame model with two different beam-column configurations was developed in order to observe the effects of beam depth, the axial load level and the level of seismicity. The frame models were analyzed under twenty different ground motion records. Local strain demands at the panel zones as well as the global frame deformation demands are evaluated. Analysis results revealed that AISC Specification designs allowed panel zone yielding / however, panel zones designed according to FEMA 355D showed minimal yielding for both shallow and deep beam configurations. Based on the analysis results, local shear strain demands in panel zones were expressed as a function of interstory drifts and normalized panel zone thicknesses.

A number of recent research studies have investigated the performance of panel zones in seismic-resistant steel Special Moment Resisting Frames (SMF). These recent studies investigated various options for attaching doubler plates to the column at beam-column joints in SMF for purpose of increasing the shear strength of the panel zone. This previous work was primarily focused on doubler plates that extend beyond the top and bottom of the attached beams, and considered cases both with and without continuity plates. As an extension to this previous research, this thesis explores the situation when a doubler plate is fitted between the continuity plates. The objective of this research was to evaluate various options for welding fitted doubler plates to the column and continuity plates through the use of finite element analysis, and to provide recommendations for design. The development and validation of the finite element model are described, along with the results of an extensive series of parametric studies on various panel zone configurations and attachment details for fitted doubler plates. Based on the results of these analyses, recommendations are provided for design of welds used for attaching fitted doubler plates in the panel zone of SMF systems. / text