جستجوی مقالات مرتبط با کلیدواژه « کمانش موضعی » در نشریات گروه « عمران »

So far, a lot of research has been done on concrete filled tubes (CFT) columns and their connections in different countries and several alternatives have been proposed for their connections, however, most of the proposed connections are associated with executive problems and have not been able to create rigid connection conditions. For steel moment frames that columns are of CFT type, new and suitable methods have been proposed to improve the behavior of their fixed connections. Among them are bidirectional bolted connections that in this study, the effect of strengthening this type of connection using haunch plated is surveyed. In these models, the main variables are haunch plates and column plate thickness. The results showed that by examining the formation of the position of the plastic hinge, it can be said that in the model without the haunch plate, plastic hinges and maximum strains are formed almost at the connection and on the face of columns. In most models retrofitted by haunch plates, however, the location of plastic hinge is in the off-connection area, approximately 20 cm side of the column. It has been seen that the CFT connections retrofitted by haunch plates, energy absorption has increased by 22.62% and the moment capacity bearing has increased by 3%. In addition, increasing the thickness of the column plate in the retrofitted connection has a greater effect on increasing the bearing capacity and energy absorption than increasing the thickness of the haunch plate.

In current international practice, composite construction is gaining importance in industrial buildings and in particular in high-rise buildings. Partially encased composite (PEC) columns are one of the recent developments in composite column. Using composite columns have several advantages such as an increased speed of erection compared to reinforced concrete (RC) columns, a more cost-effective design, smaller cross-section dimensions for similar axial resistance, and a better resistance to fire and local buckling than for steel only columns in compare with traditional RC or steel only columns. One of the proper sections for columns is a cross-sectional shape that can be used in these columns. In this paper, experimental and numerical studies are carried out on three PEC columns under pure compression load. The main difference between the specimens is in the reinforcement details of the concrete. Parameters studied in numerical work, details of reinforcement, failure mode, width to thickness ratio of steel flange and distance and transverse link diameter. The results are presented in the form of axial load-displacement curves. Also, the values of experimental work were compared with the relations between the two European and Canadian regulations, which indicated that the Canadian code was conservative. The results were developed in a numerical section after validation with a laboratory specimens and the load-bearing capacity and deformation were evaluated. The evident buckling pattern in the specimens was the kind of rupture of the welds of the links and the local buckling of the flange plate between the two links. Also, the bigger interval between the two links caused an early local buckling in the specimen.

Effect of elevated temperatures on the mechanical properties of steel, brings the importance of investigating the effect of fire on the steel structures anxiously. Columns, as the main load-carrying part of a structure, can be highly vulnerable to the fire. In this study, the behavior of steel gravity columns with box cross section exposed to fire has been investigated. These kinds of columns are widely used in common steel structures design in Iran. In current study, the behavior of such columns in fire conditions is investigated through the finite element method. To perform this, the finite element model of a steel column which has been previously tested under fire condition, was prepared. Experimental loading and boundary conditions were considered in the model and was analyzed. Results were validated by experimental data and various specimens of gravity box columns were designed according to the Iran’s steel buildings code, and modeled and analyzed using Abaqus software. The effect of width to thickness ratio of column plates, the load ratio and slenderness on the ultimate strength of the column was investigated, and the endurance time was estimated under ISO 834 standard fire curve. The results revealed that an increase in width to thickness ratio and load ratio leads to reduction of endurance time and the effect of width to thickness ratio on the ultimate strength of the column decreases with temperature increase.

The performance of connections has a significant importance in a steel structure. Designing and executing of connections without adequate accuracy can cause failure not only on the connection but even on the connection members. As a result this may have destructive effects on the whole structure. So an accurate perception of connection behavior is necessary for a safe and economical design. In this paper, static and seismic behavior of recommended splice Iran National Code is examined and contrast with behavior common splices. With finite element software, static and seismic behavior three types of splices including bearing, covering with filler plate and covering with section transfer and the collapse performance, the way of connection fracture, cyclic and static resistance of connected column are considered in this paper. The results of investigation show that recommended column splice mentioned in the 10th, has the most Focus stress of transfer part and low resistance than spliced column with filler plate and covering plate. The collapse performance of examined columns is of local buckling in transfer plate or other part of columns.

The seismic behavior of cable stayed bridge with 1255 meter span has been studied in this paper. A Finite Element model (FEM) has generated and the behavior of the bridge under ground motion has investigated, considering large deformation. The torsion can be occurred in the deck and other components of the bridge due to collision of seismic waves in direction expect of orthogonal directions of the bridge. Thus in this study, the effect of collision of seismic waves to the piers and abutment with different angle, has studied using the explicit dynamic analysis. Due to long distance of towers from each other seismic waves in from of uniform and nonuniform ground motion of the supports, have applied to the model. Moreover, local post-buckling behavior of the deck for different seismic loads has studied on the basis of geometric nonlinearity,. The results show that the top and bottom steel plates of the box girder, experience the post-buckling behavior and different responses can be obtained due to different strike angle with uniform and non-uniform support excitations. It shown that the study of long-span cable-stayed bridges under different strike angle of earthquake waves has necessity, and more economic sketch can be obtained with use of post buckling capacity.

The prediction of local stability of thin plates under compression has become increasingly important in structural design.
Numerical methods are employed to overcome the difficulties of exact solution for partial differential equations of plate’s stability. Spline Finite Strip Method is one of these numerical methods and different elastic supports attached to the plate may be handled using this method. In the present paper, local buckling of orthotropic plates resting on elastic supports are studied and results are compared with known solutions. It is shown that rapid convergence of the solution is obtained.
Local buckling coefficients of plates are calculated for various effective parameters. The optimum position of the elastic supports with specific stiffness is proposed in order to maximize the local buckling coefficients for plates subjected to in-plane loading.