• Steel and Composite Structures
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• v.25 no.1
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• pp.1-17
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• 2017

Seismic performance of hybrid steel frames defined as mixture of rigid and semi-rigid connections is investigated in this paper. Three frames with 10, 15 and 20 stories are designed with fully rigid connections and then with 4 patterns for semi-rigid connection placement, some of beam to column rigid connections would turn to semi-rigid. Each semi-rigid connection is considered with 4 different moment capacities and all rigid and semi-rigid frames consisting of 51 models are subjected to 5 selected earthquake records for nonlinear analysis. Maximum story drifts, roof acceleration and base shear are extracted for those 5 earthquake records and average values are obtained for each case. Based on numerical results for the proposed hybrid frames, story drifts remain in allowable range and the reductions in the maximum roof acceleration of 22, 29 and 25% and maximum base shear of 33, 31 and 54% occur in those 10, 15 and 20-story frames, respectively.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.375-385
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• 2000

The required connection ductility has been evaluated, considering geometric, material and connection nonlinearity, for 6-story unbraced and 20-story braced steel structures subjected to ultimate lateral load. For material nonlinearity, section moment-curvature relationship and member stiffness matrix have been derived utilizing fiber model and linear flexibility distribution model. In 6-story structure with semi-rigid connections for rigid connection, the required connection ductility is less than that for rigid connection. In 20-story structure, the required connection ductility for semi-rigid connection is almost the same as that for shear connection and the required ductility for rigid connection is larger than that for semi-rigid or shear connection.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.121-131
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• 1996

Semi-rigid frames are frames for whcih the connections joining the beam and column are neither fully rigid nor perfectly pinned. In reality, all steel frames are semi-rigid in nature as all connections exhibit a certain degree of flexibility under loads. For semi-rigid frmaed structures, it is tended to reduce more rigidity of the member for the nonlinear behavior of connections and the P-delta effects of framed structure. To predict the actual behavior of semi-rigid steel frames, a more realistic analysis methods which explicitly takes into account the effect of connection flexibility should be used. In this research, the effect of connection flexibility in the semi-rigid structure has been investigated. To predict the response of flexibility connected frames, the algorithm of semi-rigid steel frame is developed using connection model having nonlinear spring on end of beam.

• Steel and Composite Structures
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• v.34 no.5
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• pp.625-641
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• 2020

The realistic modeling of the beam-column semi-rigid connection in steel frames attracted the attention of many researchers in the past for the seismic analysis of semi-rigid frames. Comparatively less studies have been made to investigate the behavior of steel frames with semi-rigid connections under different types of earthquake. Herein, the seismic behavior of semi-rigid steel frames is investigated under both far and near-field earthquakes. The semi-rigid connection is modeled by the multilinear plastic link element consisting of rotational springs. The kinematic hysteresis model is used to define the dynamic behavior of the rotational spring, describing the nonlinearity of the semi-rigid connection as defined in SAP2000. The nonlinear time history analysis (NTHA) is performed to obtain response time histories of the frame under scaled earthquakes at three PGA levels denoting the low, medium and high-level earthquakes. The other important parameters varied are the stiffness and strength parameters of the connections, defining the degree of semi-rigidity. For studying the behavior of the semi-rigid frame, a large number of seismic demand parameters are considered. The benchmark for comparison is taken as those of the corresponding rigid frame. Two different frames, namely, a five-story frame and a ten-story frame are considered as the numerical examples. It is shown that semi-rigid frames prove to be effective and beneficial in resisting the seismic forces for near-field earthquakes (PGA ≈ 0.2g), especially in reducing the base shear to a considerable extent for the moderate level of earthquake. Further, the semi-rigid frame with a relatively weaker beam and less connection stiffness may withstand a moderately strong earthquake without having much damage in the beams.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.78-87
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• 1998

In this study, semi-rigid light-weight framed structures analysis model (SERIFS) was developed by advancing the LEIFS model. This model enables us to analyze simultaneous effects of large deflection and semi-rigid connection by computing unbalanced load occurring in the process of repeated loading through equalization of bending moments and torsion. This model is also able to handle the effect of the semi-rigid connection and large deflection by modifying the elastic stiffness matrix using moment-rotation behavior of connection. Moment-rotation behavior of the semi-rigid connection was adopted from the experimental results of load-vertical displacement of frame element In conclusion, this model achieves to analyze the nonlinear and large deflection behavior on the semi-rigid and light-weight steel frame connection.

• Steel and Composite Structures
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• v.18 no.6
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• pp.1405-1421
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• 2015

Semi-rigid connections are the actual behavior of beam-to-column connections in steel frames. However, the behavior of semi-rigid connections is not taken into account for the simplicity in the conventional analysis and design of steel frames. A computer-based analysis and design has been studied for the three-dimensional steel frames with semi-rigid connections. The nonlinear analysis which includes the effects of the flexibility of connections is used for this study. It is designed according to the buckling and combined stress constraints under the present loading after the joint deformations and the member end forces of the space frame are determined by the stiffness matrix method. The semi-rigid connection type is limited to the top and bottom angles with a double web angle connection. The Frye-Morris polynomial model is used to describe the non-linear behavior of semi-rigid connections. Various design examples are presented to demonstrate the efficiency of the method. The results of design and analysis of unbraced semi-rigid frames are compared to the results of unbraced rigid frames under the same design requirements.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.483-492
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• 2009

In this study, nonlinear analysis of steel plane frame was performed using the refined plastic hinge method of advanced analysis techniques. In deterioration of stiffness in plastic zone, influences by flexural bending, residual stress, geometrical non-linearity, and semi-rigid connection are considered. And also, further reduced tangent modulus was used for geometrical non-linearity, top and seat angle were chosen for semi-rigid connection. Furthermore, 3 parameter power model was used for moment-rotation behaviour of beam to column connection. The loading conditions are combined with axial and lateral force and the inverse triangle distribution of lateral and eight type of analytical models were used in analysis. The results of analyses were compared with semi-rigid and rigid connection on behaviour of numerical analysis models. And also, the behaviors of frame with changes of semi-rigidity were analyzed by using the results obtained from MIIDAS-GENw.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.313-324
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• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. An inelastic time history analysis of structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of semi-rigid connections were used for the models. A fiber model was utilized for the moment-curvature relationship of a steel beam and a column, a three-parameter power model for the moment-rotation angle of the semi-rigid connection, and a three-parameter model for the hysteretic behavior of a steel beam, column, and connection. The base-shear force, top displacement, story drift, required ductility for the connection, maximum bending moment of the column, beam, and connection, and distribution of the plastic hinge were investigated using four earthquake excitations with peak ground acceleration for a mean return period of 2,400 years and for the maximum base-shear force in the pushover analysis of a 5% story drift. The maximum base-shear force and story drift decreased with the outer vertical distribution of the semi-rigid connection, and the required ductility for the connection decreased with the higher horizontal distribution of the semi-rigid connection. The location of the maximum story drift differed in the pushover analysis and the time history analysis, and the magnitude was overestimated in the pushover analysis. The outer vertical distribution of the semi-rigid connection was recommended for the base-shear force, story drift, and required ductility for the connection.

• Steel and Composite Structures
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• v.4 no.6
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• pp.453-469
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• 2004

In this article, a genetic algorithm based optimum design method is presented for non-linear steel frames with semi-rigid connections. The design algorithm obtains the minimum weight frame by selecting suitable sections from a standard set of steel sections such as European wide flange beams (i.e., HE sections). A genetic algorithm is employed as optimization method which utilizes reproduction, crossover and mutation operators. Displacement and stress constraints of Turkish Building Code for Steel Structures (TS 648, 1980) are imposed on the frame. The algorithm requires a large number of non-linear analyses of frames. The analyses cover both the non-linear behaviour of beam-to-column connection and $P-{\Delta}$ effects of beam-column members. The Frye and Morris polynomial model is used for modelling of semi-rigid connections. Two design examples with various type of connections are presented to demonstrate the application of the algorithm. The semi-rigid connection modelling results in more economical solutions than rigid connection modelling, but it increases frame drift.

• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.35-46
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• 2003

Conventional analysis and design of steel structures are performed using the assumption of a either fully rigid or pinned. However, every steel connection lies in between fully rigid and pinned connection. So, It is important to consider the connection for steel structure design. In this paper Computer-based second-order elastic analysis is used to calculate one story two bay and two story three bay for steel structures with semi-rigid connection. Genetic Algorithms(GAs) and Sequential Unconstrained Minized Technique(SUMT) dynamic programming is used to the method for optimum design of steel structures. The efficiency and validity of the developed continuous and discrete optimum design algorithm was verified by applying the algorithm to optimum design examples.