فصلنامه رویکردهای نوین در مهندسی عمران
سال سوم شماره 4 (زمستان 1398)

The seismic behavior assessment of structures is carried out to estimate the damages caused by the earthquake. In recent years, with the advances of earthquake engineering, knowledge enhancement and experience in the seismic behavior of structures, novel methods have been proposed for evaluating the seismic behavior of structures and it needs to be defined as damage index. Which report the failure rate quantitatively and qualitatively. In many cases, the damage indices are dimensionless parameters whose amplitude is usually between zero for the no-damage state and one for the structural collapse state, and the values between these two are different failure states. Until now, various damage indices have been proposed based on various structural criteria such as: ductility, deformation, displacement, rotation, curvature, stiffness, softness, period, frequency, hysteresis energy or combined. Considering the characteristics of each one, selecting the appropriate damage index is a fundamental question for the design and suitability of the structure to estimate the failure rate with high reliability. In this study, in order to investigate the performance of deformation and energy parameters individually and in combined state (Park-Ang) in evaluation of seismic damage indices of steel structures, 6 moment steel frames with special ductility, regular geometry and 4, 7, 10, 15, 20 and 25 story were designed in SAP2000 software and nonlinear time history analyses were performed under near-fault records using OpenSees software. Then the values of the damage indices are calculated based on the deformation, energy and combined parameters. The results provide a quantitative assessment of the damage of the frames, stories and the role of these two parameters in numerical values of damage indices. The results show that the more effective role of the deformation of the elements in the seismic failure rate.

In solution of many engineering problems, including problems related to flow modeling in civil engineering, the use of mesh-less methods is common due to the provision of the potential field along with continuous and accurate velocity. Methods using basis functions are among the mesh-less techniques that use a set of basic functions that necessarily satisfy the homogeneous form of the equation, which is a major limitation. The equilibrated basis functions are capable of dissolving that defect by approximately satisfying the homogeneous equation in the form of a weighted residual integration, while still providing the continuity of the solution function and its derivatives throughout the domain. In the present study the weak weighted residual form, in which lower derivation orders appear than the strong form, will be implemented. The relations are expanded in a polar coordinate system. To demonstrate the efficiency of the method in engineering problems, the potential flow around a cylindrical barrier will be examined.

One of the most important parameters in dynamic analysis and design of structures is the lateral displacements caused by loading and incitement instigations to the structure which is very important in the process of computation calculation and determination of the structure sections and dynamic parameters of the structure. In the past, in the process stage of structural analysis and determination of forces and stresses tensions and the response of the structure to existing investigations stimulus, soil and foundation and structure  systems were investigated and studied and analyzed with districted and separated forms and numerous great simplifications. These studies were modeled and analyzed by with considering consideration of placing the structure on a rigid solid foundation on a soil with sufficient resistance to resist the session’s summits and forces, which is transmitted from the structural   foundation of the structure to it. Field studies and the results and observations obtained by from visiting the damaged and damaged areas of the earthquake, showed that, even at a certain location and among similar structures for in terms of shape and geometry and dynamic characteristics, the damage caused by the earthquake can could be very different, and this can only be due to the effect attributed to the impact of structure interaction - soil and foundation and such as that. The next Subsequent studies showed that the interaction of soil and foundation and structure themselves are highly strongly influenced by many parameters such as environmental factors, mechanical properties of material and soil, and the seismic characteristics form of foundation and gender, and the depth of soil and substrate seismicity of the zoning of the site of the structure and the geotechnical characteristics of the structure specifications and the like.In this study research, it tries by investigating of the is attempted to investigate these two parameters and modeling it them in the powerful software  “Abaqus” software  and considering the sufficient taking into account the number of required models needed that in each of them, One of the parameters under investigation changes, the value of their effect on the dynamic response of the structures are should be  studied.

Buckling Restrained Braces are typically made of a steel core that is encased in a steel sheath filled with concrete. The steel core is designed based on axial strength with the potential for compressive and tensile yields, regardless of fracture, and provides steel and concrete sheaths of sufficient axial and flexural strength to prevent overall buckling of the braces. In this study, the effect of geometric shape and steel material of connection plate on cyclic performance of buckling restrained brace is investigated using finite element simulation. 6 types of rectangular and curved connection plates are modeled ST37 and ST52 with and without holes in with finite element ABAQUS software and the results are presented in the form of damage modes and the force-displacement hysteresis curves are studied and compared. In this study, in order to confirm the modeling method and used assumptions, an experimental specimen buckling restrained brace is tested in finite element ABAQUS software. The results of this study indicate the considerable effect of geometric shape of the connection plate and its steel material on the cyclic performance of frames with buckling restrained braces.

Nowadays, due to increasing construction in the country, especially in metropolises and problems arising during the implementation of construction projects, there is a need for coordination between the architect in design, the structural engineer in the design of the structure and the installation engineer in the design of the installation phases and Collaboration with these engineers in different phases is increasingly felt. In many parts of the world, all phases of architecture, structures, and installations continue to work as part of a design team and along with the implementation phase, to address deficiencies, while there is less coordination in our country. And once the drawings of each phase have been finalized, the relevant phase engineer imagines his work to be completed and no longer assumes responsibility for his design work at runtime. In the meantime, the Supervisor Engineer and the Project Development Team, due to the lack of access to the Design Engineers, have a taste for the problems that may arise, sometimes causing greater engineering and safety damage. This study attempts to show some of the discrepancies between the phases and the discrepancies between engineers at the time of project implementation and some performance issues.

The rock masses have naturally a large number of cracks and discontinuities which cause to be prone to damage under dynamic loading. The earthquake as a kind of dynamic loading may propagate the inherent cracks in rock masses and leads to failure of the rock structures such as mines, oil and gas wells, tunnels, dams, etc. Therefore, the fracture of rock masses due to cracks under earthquake should be considered by civil, mining and even mechanical engineers and researchers. Fracture mechanics as a branch of mechanical engineering science has been frequently employed for investigating the fracture behaviour of cracked rock structures. According to the orientation of crack relative to applied load, the cracked parts may be subjected to pure or combined mode loading I, II and III. The underground rock masses are often subjected to a compressive loading due to the pressure of upper rock masses. In the first sight, the crack flanks under compression are pressured together and the geometry discontinuity is vanished. However, the crack faces may be subjected to sliding loading and the vulnerability of cracked rock masses is still remained. Therefore, the fracture analysis of cracked rock masses under compression-shear loading should be investigated. Similar to the mixed mode I/II loading, there are several studies in the literature investigated the fracture of cracked specimens under compression-shear loading both experimentally (Al-Shayea, 2005) and theoretically (Li et al., 2009). From the theoretical viewpoint, the compression is considered as a compressive stress in the stress field around the crack tip and then the fracture criteria based on new stress field is utilized for predicting the fracture resistance of cracked specimens. The aim of this paper is to present a new approach for predicting the fracture load of cracked rock samples under compression-shear loading. The new approach is based on the maximum tangential stress (MTS) criterion which is one of the classical fracture criteria in fracture mechanics.