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.

In this paper, different methods of analysis are studied for the column base plates. Comparison is made between the experimental results and the effective and practical method proposed in here. This method uses the contact problem approach. Application of the prepared design monograms is illustrated using a simple practical problem.

In this paper, analysis of column base plates have been done by using the methods of contact problem. The result of this analysis on different Specimens, have been compared with the results of current method with is done by presuming uniform stress under plate.

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.

In this study, the ratio of rotations created in beam and column members of reinforced concrete flexural frames, relative displacements of floors at the functional levels of uninterrupted serviceability, life safety and failure prevention have been investigated by considering different ratios for the weak beam-strong column criterion in the optimal design process within the framework of the performance-based design approach. For the purpose of performance-based optimization, the center of mass meta-exploration algorithm has been used in this study. The philosophy of the performance-based design approach and even traditional design methods allow the structure to suffer damage when exposed to strong and relatively strong earthquakes. Therefore, in order to estimate the safety of the structure against earthquakes, the use of seismic safety quantification indices and structural collapse capacity seems necessary. In this study, the relative displacements of floors and the ratio of existing to permissible rotations of beam and column members of each optimal structure have been calculated using time history analysis under earthquakes far and near the fault. Two examples of 3 and 6 stories are the frames studied in this research, which are designed by considering coefficients of 0.8, 1.2 and 1.6 to control the weak beam-strong column criterion in the performance-based optimization process. According to the obtained results, it is observed that increasing the weak beam-strong column ratio to control the aforementioned criterion in the optimization process leads to a decrease in the rotation ratio created in the beams and columns of the structure.

Esthetic is a natural necessity among all human beings, and the reconstruction of the natural features of prosthesis is considered an important aspect in dentistry. Reconstruction of the natural features in removable prosthesis by characterization of denture base is one of the most important factors. In this regard esthetic, in removable prostheses, is achieved through different techniques such as: tooth selection and arrangement, designing the denture base and acrylic base color. The final goal for all these effects is to achieve a natural appearance for denture. However, other factors such as treatment limitations, different personal needs and general health principles, should be taken into consideration. This article not only reviews the natural appearance of oral mucosa that is replaced by the denture base, but also discusses about the materials used in tinting acrylic denture base and their application techniques.

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.