Advanced Materials Research Vol. 1020

Abstract: The calculation of the structure's hardness is of special importance in calculation of possibility of existing splits' distribution in account of ensuring the reliability of the problem's solution. It is known that the structure's crumbly deterioration is dangerous not only for its unexpectedness but also because it takes place in the conditions of operating voltages of such magnitude, which are obviously smaller than the calculating ones. This means that the actual supply of structure's hardness, which is defined by the usual calculating methods of hardness, without taking into account the existence of splits, will be significantly smaller than the provided. If the existence of splits are not taken into account, then the local overvoltage occurs around them and ultimately unprecedented crumbly deterioration of structure takes place. In the work the independence of magnitudes of splits' spread and the measure of length of splits existing in the flatness of the base of concrete gravitation dam having been built on hard basement is got. The problem is solved by variational method by application of minimum principle of theory of elasticity. The obtained results are compared with the obtained problems applicated by approximate formula. A range is found out where it is possible to get used of the application of comparatively easy and considerably reliable methods of giving good results in sections.

Abstract: Almost all high-rise buildings have been constructed in the Republic of Armenia for past twenty-five years are Reinforced Concrete (RC) shear wall–frame structures, where shear walls provide most of the stiffness of buildings. The walls in these buildings are designed to sustain earthquake and wind loads. Vulnerability of them during earthquake action depends on many different factors. Some of them are the openings and its location in the walls. Usage of ground stories as parking and garages is demanded large openings in shear walls therefore determination of ultimate sizes of openings is important problems for designers. In this paper, FEM (Finite Element Method) models are used for investigation of stress-strain state of RC wall–frame buildings with various openings in the walls under action of seismic forces. Limitation of size and position of openings are considered in the paper taking into account of building code of Armenia. Various schemes of openings are considered in the article. The existing experimental data of shear walls were performed in various laboratories have been compared with our numerical investigation of RC models based on nonlinear computer analyses. Dynamic analyses of structures using accelerograms are showed sequence of damages in RC wall-frame models. The recommendations for limitation of ratio area of an opening to the whole area of a wall are proposed at the end of the article.

Abstract: Aghjots Monastery was built in IX - XIII centuries within the Khosrov State Reserve in Armenia. It takes a vantage point in the slope and is featured with beauty and unique carvings. Aghjots Monastery consists of the Saint Stephan church, which is the cruciform inscribed in a rectangle externally rectangular church with a cruciform interior, a single apse and four corner - chambers (two-story side-chapels in each corner), the church of Saints Peter and Paul, is the single naved hall-type church with no freestanding pillars and no dome and a gavit adjacent [1,2]. Aghjots Monastery experienced some strong earthquakes which resulted in its almost complete destruction. This article presents a description of the existing state of the Aghjots monastery and importance of the detailing geometrical survey, decay and material mapping. Stress-strain state of main church at seismic action including dynamic behavior of Saint Stephan church is considered in the article. The bearing system is modeled by using shell finite elements by software based on finite element methods. This proves to be an important feature to understand the damage mechanisms, solve the conservation and reconstruction problems.

Abstract: Problems on contact interaction between continuous or discontinuous infinite stringer or with a stringer of finite length with an elastic semi-infinite plate, having a finite crack, which vertically comes out to the lower bound of the stringer, are considered. The edges of the crack are loaded by vertical to them symmetric forces, and the upper bounds of the stringers are loaded by symmetrically distributed tangential forces.

Abstract: In the current design of the traditional eccentrically braced steel frame systems, the link is a portion of the floor beam. The link damages because of absorbing energy firstly during an earthquake, therefore, the ability to repair the floor beam is very different, disruptive and costly and may affect the normal use of buildings because of the long repairing time. In addition, it is difficult to assess the extent of its damage, so we don't know whether the structure can survive under another earthquake. To solve these drawbacks, on the basis of this traditional eccentrically braced steel frame, the paper proposed a concept of the replaceable shear link which consisting of two channel sections bolted on either side of the web of the connecting floor beam (which called the new replaceable shear link thereinafter). The advantages and working mechanism of the new replaceable shear link were introduced in this paper, energy dissipations of the replaceable shear link and hysteretic behaviors of the eccentrically braced steel frame with replaceable shear links were analyzed under the cyclic loading by the finite element analysis software of ABAQUS. From the results of the analysis we can see, the new replaceable shear link has good seismic performance and deformation performance.

Abstract: The extradosed cable-stayed bridge is a new type of bridge developed in recent year. The main girder bears most of the load with its great stiffness, while the cable tension can improve the force state of the girder. So it is really necessary to optimize the cable force to determine the internal force of extradosed cable-stayed bridge under the rational completion state. But the optimization methods commonly used are based on the cable-stayed bridge and not entirely suit for the extradosed cable-stayed bridge. The paper puts forward a new optimization method, which includes applying the unknown coefficient functions aided by MIDAS/CIVIL, taking the reasonable feasible range of dead moment solved by stress balanced method as the constraint condition, making the square of unknown coefficients as objective function, and solving the cable force based on the effect matrix method thus to determine the cable force in reasonably completion state. This new method is verified with favorable effect, the internal force of this structure appear significant improvement. And finally, the results show better cable force obtained under the method in this paper compared with the cable force under other constraint conditions and objective functions.

Abstract: In this paper, the overlong frame structure established by software ETABS was analyzed to find out its mechanical characteristics under the working condition of overall cooling temperature. The columns at the ends of the bottom storey, the beams and slabs in the middle of the first floor were the important components affected by temperature action. Various column cross-section sizes and forms as well as the storey heights to the reaction of the important components were analyzed through a series of finite element models. The key to reduce the temperature effects on overlong frame structure was reasonable design of frame columns at the end of the bottom storey, which are the smaller the cross-section stiffness, and the higher the bottom storey, the smaller the internal forces caused by overall cooling temperature in structural components. Some detailing structural measures were put forward to decrease the negative temperature effects.

Abstract: The article presents a way of reinforcing concrete beams with innovative composite materials in the form of basaltic-epoxy bars. Considering the carrying the element out in the technology of the prefabrication, the main assumptions and aims of the method and economic conditioning were described. Examples of domestic, modern engineering objects made in the prefabricated structure were expressed. The particular attention was devoted to the issue of the cover of the composite reinforcement conditioning the permanence of the ready element. In the part of the article devoted to the numerical analysis of the new construction, is characterized the most important mechanical and physical parameters of used composite bars and presented the assumptions of the method of the numerical modeling of beams subjected to clean bending. For the optimum evaluation of the element a research set was prepared in the form of the reinforced beam by composite bars, and another one by steel rods and concrete beam without the reinforcement - enabling evaluation of the correctness of the method. The analysis is opening the doors for the more accurately research on the usefulness of the composite reinforcement of the concrete prefabrication to the modern construction.

Abstract: A rod composed of two different prismatic rods built-up with rectilinear orthotropic materials is studied. Composite parts of the prismatic rods are connected entirely by their common surface. The anisotropy axis is perpendicular to the cross-section plane. The problem has been solved in Cartesian coordinate system. The functions of stresses are presented by the sums of solutions corresponding to positive eigenvalues of homogeneous boundary problems and partial solutions of inhomogeneous boundary problems. From condition of existence of the non-trivial solution of the homogeneous boundary problem an equation in respect to eigenvalues is derived of which roots are real and different. If there are roots in (0; 1) interval, then the stresses tend to infinity at the vertex of the cross-section of the composite rod have a feature with the order equal to where - is the smallest root in the interval (0, 1).

Abstract: The problem of fracture mechanics concerning contact interaction between elastic infinite plate and elastic compound semi–space is investigated. Plate and semi–space are weakened by finite through cracks, which are perpendicular to surface of heterogeneity in the same plane. Assuming that structure is deformed in antiplane deformation state it is required to determine the contact stress distribution and fracture stress intensity factors dependence of structure heterogeneity and geometrical parameters. Using the Fourier integral transform the problem is reduced to find the solutions of system of two singular integral equations. System solutions behavior at integration domain endpoints is investigated for all cases. In some special cases of cracks location, equations kernels can also contain fixed singularities. An efficient numerical method to solve such equations is suggested. Numerical calculations are done and results are shown in tables and graphs, which express contact stresses and stress intensity factors dependence on problem parameters and simultaneously reveal dangerous cases of fracture of the structure.