Fixity of column base connection plays a major role in overall behavior of steel structures. Several parameters influence the real behavior of the column base connections, among them base plate thickness, anchor bolts and stiffeners details can be mentioned. A nonlinear three dimensional finite element method has been utilized for numerical studying of the behavior of the column base connection. Thickness of the base plate and stiffeners and also sizes and numbers of the anchor bolts were changed in a number of models to determine their effects on the nonlinear behavior of the regular column base connection. It was observed that column base connection characteristics such as its moment-rotation behavior, yielding pattern of base plate and anchor bolts and local stress concentration of the connection elements can be significantly affected by changing any detail of the connecting elements. The effects of each parameter on the behavior of column base connection were categorized and presented in this paper.

Conventional column bases are fundamental components of the steel frame. Their behavior has been proved to have a significant effect on the overall building seismic response. Base connections, flexibility largely affect the period of the building and the lateral displacement of the stories. In this research, a new type of connection at the steel column bases has been proposed. the main purpose of proposing this connection is to decrease residual displacement and minimize repair time and disruption of the building serviceability after a strong earthquake. Therefore, to be able to evaluate and compare the seismic performance of this connection with seismic lateral force resisting systems which have developed recently, a self-centering concentrically braced frame (SC-CBF) has been selected from Hasan’s research and analyzed and validated. Also, the performance of the system with the proposed column base is evaluated using numerical analysis. The results show that in the proposed system, the amount of residual drift in the structure is equal to 2.2×10-14%. Therefore, it can be concluded that the proposed connection satisfies the main purpose of the research well, which is to eliminate residual drifts in the system. they also have higher energy dissipation and stiffness than the SC-CBF system that has been developed so far. While the post-tensioned bars are not used.

Column base connections are commonly used to connect steel columns to concrete foundations in seismically designed Steel Moment Resisting Frames (SMRFs). These connections are economical for mid-to high-rise frames in which exposed base plate connections (affixed to the footing with anchor) are impractical owing to the necessity of thick base plates and numerous anchor rods. The bolts are cast into the concrete base in location tubes or cones and fit anchor plates to prevent pullout. High-strength grout is poured into the space below the plate. Column base connections are one of the most critical structural connections. Understanding the behavior and performance of these connections come in handy for designing this type of connections, especially in the seismic design of the structures. Such column bases are often only subject to axial compression and shear. However, uplift and horizontal shear may be a design case for column bases in braced bays. The way in which horizontal shear forces are transferred to the foundation is not well researched. Some designers check the resistance of the holding down bolts, and ensure that they are adequately grouted. This practice has been successfully followed for portal frame bases, which carry a significant shear. In column base connection, it can be said that the rotational stiffness is the only feature that links uncertainty in column base connection to structures such that a change in them can change rotational stiffness and, as a result, change the dynamic characteristics and seismic response of structures. In the present study, by considering the sensitivity mentioned above, the effects of rotational stiffness and the strength capacity of column base connection on behavior and seismic performance of steel moment frame have been evaluated by Modal Pushover Analysis (MPA) and Nonlinear Dynamic Analysis (NLDA) methods. The results show that the rotational stiffness of the column base connection effects on the dynamic properties of structures such as pushover curve, story drift, and ductility as well as the analysis of models together with different rotational stiffness showed that structures in combination with semi-rigid rotational stiffness are much better in designs.

In recent earthquakes some beam-column joints have shown undesirable brittle mode of failure by developing a fracture line at their welded connection between the beam and the column. The main reason for this type of behavior is the formation of dominate three dimensional state of tension stresses around the connection lines. Such confinement at weld materials reduces the ductility of the weld and provides the condition for brittle fracture at the connection line. The onset of fracture is, therefore entirely dependent on the magnitude of the state of stress. As a remedy, many researchers propose to reduce the distance far from the face of the column. In this study, a new type of beam-column joint with the same rational is developed. While possessing all the required features for such connections, it is considered a practical solution for beam-column joints by solving some other related issues surrounding the problem. Analytical and experimental studies, carried out in this work, verified the potential of the proposed beam, column connection in preventing brittle mode of failure. The joint has also shown a remarkable cycle behavior by representing a large number of loops with low rate in degradation of sectional properties.

In concrete slabs, due to the absence of support beams, three-dimensional shear stresses are created around the slab-column connection area, leading to radial shear cracks and punching shear in the column-slab connection area. In this article, for evaluating the strengthening of the slab-column connection using CFRP sheets under the conditions of punching shear and seismic loading, the numerical method has carried parametric studies out. Therefore, considering 5 variables: loading conditions, number of fiber layers in the sheet, angle of fiber placement, sheet thickness, and dimensions of CFRP sheets, parametric studies have been carried out in the form of 33 separate models by Abaqus finite element software. Validation of the numerical model was evaluated based on the modeling of the laboratory sample. The results showed that the average error of numerical modeling was 5.2% compared to the laboratory sample, indicating the numerical model's acceptable accuracy. Also, the results showed that the two parameters of sheet thickness and dimensions are the main parameters in strengthening the RC slab-column connection, so considering the optimal values of about 98% reduces the damage to the concrete slab. The results of this research can be used as a comprehensive model for the design and application of CFRP sheets in strengthening the concrete column-slab connection.

This article tries to create a comprehensive view of new government concept especially its role in complex, important and wide interaction between industry and University with presenting an operational definition of live government and its examples in all countries in the world.This article also has explained the role of live government according to each society properties and at the end has presented a native model for Iran.The researcher tries to create a new picture of concept of government and its role in national maturity, excellence and hilarity and also participation toward more clear future with consideration to the newest theories and scientific samples.

Some considerable damage to steel structures during the Hyogo-ken Nanbu Earthquake occurred. Among them, many exposed-type column bases failed in several consistent patterns, such as brittle base plate fracture, excessive bolt elongation, unexpected early bolt failure, and inferior construction work, etc. The lessons from these phenomena led to the need for improved understanding of column base behavior. Joint behavior must be modeled when analyzing semi-rigid frames, which is associated with a mathematical model of the moment–rotation curve. The most accurate model uses continuous nonlinear functions. This article presents three areas of steel joint research: (1) analysis methods of semi-rigid joints; (2) prediction methods for the mechanical behavior of joints; (3) mathematical representations of the moment–rotation curve. In the current study, a new exponential model to depict the moment-rotation relationship of column base connection is proposed. The proposed nonlinear model represents an approach to the prediction of M-q curves, taking into account the possible failure modes and the deformation characteristics of the connection elements. The new model has three physical parameters, along with two curve-fitted factors. These physical parameters are generated from dimensional details of the connection, as well as the material properties. The M-q curves obtained by the model are compared with published connection tests and 3D FEM research. The proposed mathematical model adequately comes close to characterizing M-q behavior through the full range of loading/rotations. As a result, modeling of column base connections using the proposed mathematical model can give crucial beforehand information, and overcome the disadvantages of time consuming workmanship and cost of experimental studies.

The importance of welded connections on the behavior of steel moment resisting frames was the reason of researchers focus on welding details. In this paper result on 32 pilot tests indicate moment connection behavior are presented. In this experimental research, in order to connection strength evaluation, complete joint penetration (cjp) weld strength with different welding procedure, double side fillet weld out of plane strength, one side fillet weld out of plane strength and amperage intensity effect on welding quality, have been studied. Also in order to connection rehabilitation, rib stiffener effect on connection strength, T-stiffener effect on connection strength, electrode toughness effect on welding quality and grinding and rewarding effect on welding quality have been studied. Maximum strength of cjp weld is observed in welding with backing. Out of plane strength of double side and on side fillet weld have been determined. Connection strength increase amount with stiffener strengthening of connection have been proposed. It has also been proposed constructional recommendations about electrode toughness, rewelding and amperage intensity.

This paper proposes a new geometry for the moment connection between I-beams and double-I built-up columns. The beam flanges are usually connected directly to the column cover plate by T-joint full penetration groove weld. The column cover plate will be quite flexible. The groove weld will also become a weak point and lead the connection to premature failure. We have studied the possibility of using full-depth side plates to modify the connection geometry. This new geometry eliminates brittle behavior and all other uncertainties that are intrinsic with the use of complete penetration groove weld. Using the side plates also eliminates all uncertainties about the deformation and buckling of double-I column cover plate. A series of five non-linear, three dimensional finite element models were developed to study the behavior of moment connection of I-beams to double-I built-up column under cyclic loadings. The results obtained from our numerical analysis indicate that this new connection geometry has sufficient strength and ductility to be classified as a SMF connection.