The Sungun Copper Mine is located in a highly hazardous seismic area. Most recently, the Ahar-Varzeqan earthquake, M 6. 2, occurred on August 11, 2012; at a distance about 40 kilometers away from the mine. Nevertheless, the seismic stability of the final pit wall was not comprehensively reviewed. In this research, the southwestern wall of Sungun’ s final pit was investigated through pseudo-static, Newmark and numerical methods. Moreover, some of the difficulties in accomplishing and interpreting the results in dynamic analyses of a mining slope is explained. Pseudo-static analyses revealed that the final pit wall is not safe against the design earthquake, and it is highly prone to failure. The results of Newmark analysis proved that a large failing region would form in the case of design earthquake. Based on a dynamic numerical analysis on the pit wall, continuous forward and downward earthquake-induced movements were observed, as well, which might be a sign of pit wall instability. The effect of underground water drainage on stability of the pit wall was investigated in the numerical model. Resulted time histories of displacements in the drained pit wall proved that only water drainage is sufficient for protecting the pit wall against the design earthquake.

This study is devoted to tracing the equilibrium path of structures with severe nonlinear behavior. A new displacement increment is suggested to do the analysis. Moreover, the increment of the load factor is obtained by minimizing the residual displacement. To evaluate the capabilities of the presented method against existing ones, a comparison study is performed. In this process, five benchmark frame and truss problems are solved. Each of the structures is analyzed more than 600 times, and the outcomes are compared with each other. According to the results, the authors' scheme is more competent than the methods of residual load minimization, normal plane, updated normal plane, cylindrical arc length, work control, residual displacement minimization, generalized displacement control and modified normal flow.

The combination of horizontal drilling along with hydraulic fracturing has significantly improved the production of hydrocarbon reservoirs and made it possible to extract the relatively impermeable and uneconomical reservoirs. The production rate of oil and gas wells increases proportional to hydraulic fracture aperture or crack opening displacement (COD). This is an important parameter in fracture mechanics literature and hydraulic fracturing of hydrocarbon reservoirs. Despite the significance of COD there are a few analytical solutions for the estimation of COD under certain conditions. In this paper the effect of various parameters on COD is investigated semi-analytically. A higher order displacement discontinuity method is used to consider the effects of different parameters (Young’ s modulus, Poisson’ s ratio, internal pressure, maximum and minimum horizontal stresses, crack half-length and its inclination with maximum horizontal stress) on the COD in a hydraulic fracturing process under arbitrarily conditions. The coefficient of determination and standard error of the estimate were 94. 35% and 4. 37×10-4 respectively, showing a good agreement between the fitted equation and the numerical results. The effect of propagation and well radius on the maximum COD was also investigated. The results showed that COD increases almost linearly with the crack propagation and increase of well radius of hydraulic fractures (HFs). These effects are more significant when HFs are propagating in the direction of maximum horizontal stress. The proposed equation and the results from propagation of hydraulic fractures can be used in early stages of a hydraulic fracturing design.

Conventional experimental techniques like, quasi-static, effective force and shake-table techniques are generally being adopted to evaluate the seismic response of a civil engineering structure under earthquake loading. Among these techniques, shake-table technique has a merit over the other techniques due the fact that it realistically simulates all the three basic dynamic force parameters namely inertial, damping and elastic forces in the test structure. However this technique needs a sophisticated shake-table driven by servo hydraulic actuators with excellent control electronics. In the absence of such an expensive shake-table, it is possible to simulate the three dynamic force parameters using a static actuator through application of an equivalent pseudo-dynamic force system by computation of inertial forces in the back-ground. Such a hybrid Pseudo-dynamic (PsD) technique needs a specialized algorithm based on an appropriate mathematical model for the off-line time integration and computation of inertial forces such that the dynamic displacements/forces are applied statically through static actuators. Restoring forces offered by the structure are experimentally measured on-line at each time step and reflects the actual in-elastic and energy dissipation characteristics of the tested structure. The paper presents the mathematical formulation of a 'predictor-corrector' method using Newmark implicit relations and its implementation in PsD technique for seismic response evaluation of structures. In the proposed method displacement iterations are made in the corrector phase in achieving the implicit displacement which is an improvement over the conventional method where displacement iterations are made to achieve the explicit displacement resulting in lesser accuracy. To experimentally verify this improved PsD technique, the seismic response quantities including base shear, roof displacement and energy dissipation of a model steel frame structure subjected to a simulated earthquake predicted using PsD technique were calibrated with seismic responses evaluated using standard shake-table technique. The paper also presents the causes for the deviation in the predicted seismic responses using PsD technique and highlights its merits and demerits over shake-table technique.

In recent years, Pseudo-dynamic (PsD) technique is being adopted as an alternate to conventional shake-table technique to evaluate the seismic performance of structures. The shake-table technique has the merit of simulating all the three force parameters namely inertial, damping and elastic forces in the tested structure realistically; however the technique needs sophisticated shake-table driven by servo controlled actuators with appropriate control electronics. On contrary, PsD technique simulates the three force parameters by using a static actuator through application of an equivalent pseudo-dynamic force system with computation of inertial forces in the back-ground. Such a hybrid technique needs specialized algorithm based on an appropriate mathematical model for the off-line time integration and computation of inertial forces. Several time integrals have been proposed for application in PsD testing and majority of them are derived from Newmark-b family of algorithms. The traditional PsD testing uses constant acceleration version of Newmark time integral in explicit form for mathematical simplicity. This simplified explicit formulation results in numerical damping leading to considerable amplitude error in PsD testing, limiting its application to simple structures. However, for complicated structures improvement is needed in the time integral form leading to unconditional stability and zero numerical damping. This paper presents an improved form of Newmark implicit time integral for PsD testing. The improvement is based on the inclusion of an additional term in displacement predictor, which not only renders the algorithm more consistent, but also eliminates numerical damping and makes the algorithm unconditionally stable. The paper presents the analytical study carried out on the stability and energy dissipation properties of the improved time integral by evaluating its spectral characteristics for verifying its suitability in PsD testing.

This study proposes an e cient technique called displacement method of analysis and applies three metaheuristic algorithms, namely Colliding Bodies Optimization (CBO), Enhanced Colliding Bodies Optimization (ECBO), and Vibrating Particles System (VPS), to perform the simultaneous analysis and optimal design of trusses. The proposed method was applied to the minimum weight design of some planar and spatial truss structures. To investigate the accuracy and e ectiveness of the presented method, the problems were designed using the same metaheuristic algorithms through pure force and pure displacement methods as analysis tools (non-simultaneous). Then, the resulting structural weights were compared.

Purpose– analysis of non-prismatic beams has been focused of attention due to wide use in complex structures such as aircraft, turbine blades and space vehicles. Apart from aesthetic aspect, optimization of strength and weight is achieved in use of this type of structures. The purpose of this paper is to present new shape functions, namely 3-node Basic displacement Functions (BDFs) for derivation of structural matrices for general non-prismatic Euler-Bernoulli beam elements. Design/methodology/approach– Static analysis and free transverse vibration of non-prismatic beams are extracted studied from a mechanical point of view. Following structural/mechanical principles, new static shape functions are in terms of BDFs, which are obtained using unit-dummy-load method. All types of cross-sections and cross-sectional dimensions of the beam element could be considered in this method. Findings– According to the outcome of static analysis, it is verified that exact results are obtained by applying one or a few elements. Furthermore, it is observed that results from both static and free transverse vibration analysis are in good agreement with the previous published once in the literature. Research limitations/implications– The method can be extended to structural analysis of curved and Timoshenko beams as well as plates and shells. Furthermore, exact dynamic shape functions can be derived using BDFs by solving the governing equation for transverse vibration of beams. Originality/value– The present investigation introduces new shape functions, namely 3-node Basic displacement Functions (BDFs) extended from 2-node functions, and then compares its performance with previous element.