Determination of non-hazardous areas in terms of seismic effect for the use of explosives in the open pit in safe conditions

In addition to the technical and economic advantages of blasting rocks from open-pit mining, this method of extraction can produce effects with a direct impact in the area near the open pit. Blasting works generates effects such as seismic waves that cause vibrations, rock throws, noise and toxic gases. When their intensity and scope are not systematically evaluated and analysed, blasting works can cause serious consequences for people, civil / industrial buildings, the environment, thus affecting the health of the population and the stability / integrity of the buildings / slopes in the vicinity of the mining operations. The paper presents design / determination methods of areas where explosives may / may not be used in conditions of maximum safety in terms of seismic intensity, thus protecting the population and the civil / industrial objectives in the area of the mining work. The obtained results are extracted from a research study carried out for the opening in operation of a new mining deposit, having as reference calculations and theoretical interpretations related to the conditions established for the development of the blasting works.

Seismic Performance of RC Column Using Fiber Hinge Concept with Time Integration Method

Recent seismic events showed the importance of understanding the structural performance of RC column that can be predicted numerically. The accuracy of column performance depends on type of the analysis and representation of seismic effect. Therefore, in this paper a nonlinear time history analysis has been performed to assess the seismic performance of bridge column using fiber hinge concept with time integration method using sap2000 software. A long bridge RC column is utilized and subjected to seismic excitation. The column has been divided into different size and numbers of fiber to assess the accuracy of the analysis and time consuming to analyze each case of fiber hinges. In addition, this paper used three-time integration methods, Newmark, Hilber-Hughes-Taylor, and Chung & Hulbert to predict the most suitable method to be used in column seismic analysis. The time history displacement and base shear in addition to moment rotation of the column are the most important factors to evaluate the column seismic performance. The analysis results demonstrated that the most suitable time integration method is Hilber-Hughes-Taylor for such type of the analysis since it gives more stable base shear result than other two methods. Furthermore, the results indicated that the accuracy of seismic performance increased by number of fibers incremental. Moreover, the number of steel fibers should be equal to the number of bars with same area and location. The unconfined and confined concrete should be divided into small areas to get accurate prediction of column seismic performance.

Numerical Performance of Energy Dissipation Slotted Plate for Bridge Unseating Prevention

Recently, the bridge unseating prevention devices are widely used in active seismic zones. These devices are stiffness dependant, velocity dependant and energy dissipation devices. The energy dissipation devices are designed to overcome the energy that transfers from bridge substructure to superstructure. However, the current devices are not controlled to function with different ground motion intensities and should be replaced after yielding. Therefore, this research introduced a slotted plate energy dissipation device with three parts, each part function in known deformation range. The slotted plate behavior has been evaluated numerically by finite element method. Displacement control and load control analysis has been done, and then the effect of steel grade is studied to predict the suitable steel properties for designing the plate. Moreover, the slotted plate behavior is applied in 3D bridge seismic analysis to assess the multi-level performance and the ability to overcome the seismic effect on the bridge in longitudinal direction. The results approved the capability of the plate to dissipate energy in multi-stage of deformation. The lower steel grade is suitable for low to moderate earthquake zone and the high grade can be used in severe ground motion areas. Furthermore, the bridge longitudinal behavior has enhanced with different steel grades of the slotted plate.

MIDDLE URAL EARTHQUAKE on October 18, 2015, ML=4.7, I0=6

Instrumental and macroseismic data on the earthquake of 18.10.2015 at 21h44m UTC, ML=4.7, I0=6 in the Sverdlovsk region, near the village of Sabik (Middle Urals) are presented. A significant amount of macroseismic data made it possible to build a map of the macroseismic field, taking into account the anisotropic nature of the propagation of the seismic effect. Taking into account the decision of the focal mechanism, the tectonic position of the source was substantiated.

Improving Technical-Economical Performance at Praid Saline Way of Rock Salt Roadheader Mechanized Mining

Increasing the mining depth at Praid Saline and implicitly the state of stresses and strains determines an increase in the dimensions of resistance structures (pillars and ceilings). Furthermore, the seismic effect generated by the detonation of explosives contributes to the degradation of resistance structures. In order to reduce the destructive effect of drilling-blasting technology a proposal is made for the implementation of mechanized salt cutting technology which makes use of a roadheader. This article emphasizes the technical-economical implementation advantages of exploitation from the lower horizons of the New Sector, those of mechanized mining with a roadheader as opposed to the classical technology of drilling-blasting.

Dynamic Performance of Vehicle–Guideway Bridge Systems for Low–Medium-Speed Maglev Trains Under Earthquakes

This paper developed a numerical model for predicting the seismic responses of vehicle–guideway bridge systems for low–medium-speed (LMS) maglev trains. Each vehicle was characterized as a multi-rigid-body with 50 degree of freedoms (DOFs), and the guideway bridge was modeled by the finite element method. The actively controlled electromagnetic forces were considered in simulating the vehicle–guideway interaction relationship. Subsequently, the equations of motion for the vehicle–guideway coupled system under earthquake were, respectively, established in relative and absolute coordinate systems to quantify the effect of structural pseudo-static components, so that the seismic effect can be taken into account. Case study was then conducted to thoroughly discuss the seismic responses of the vehicle–guideway coupled system in both time and frequency domains. Furthermore, parametric study was carried out to determine the effect of key parameters (i.e. vehicle speed, stiffness of guideway) on the system’s responses. The results show that the conventional seismic analysis method relative motion method (RMM) (ignoring the structural pseudo-static component) will considerably underestimate the seismic responses of the coupled system, especially of the vehicle. It is suggested that the formulation be established in the absolute coordinate system (i.e. using direct solution method, DSM) for more actual prediction. The frequency responses indicate that the vibrations of vehicle–guideway coupled system under earthquake relate significantly to the natural frequencies of vehicle and bridge, while the same is not true for the vehicle-induced excitation.

Seismic behavior of the main girder of a bridge with viscoelastic dampers

Introduction. The seismic stability of bearing structures is one of the main objectives of design and construction of structures in earthquake areas. The co-authors have analyzed the effect of a damper, located at the intersection of structural elements, on the seismic response of the main girder of a steel-concrete bridge exposed to the seismic impact. The purpose of this study is to select optimal values of viscous and elastic elements to ensure the seismic resistance of the bridge. Materials and methods. The finite element method was used to simulate the geometric characteristics of the bridge. The model of the bridge has rod elements to simulate girders and viscous elastic elements to simulate dampers. In the study, different values of elastic and viscous characteristics of the damper were used in pairs. The nonlinear problem statement helped to analyze the bridge structure using the direct dynamic method. Results. As a result, we obtained a graphic chart describing the relationship between horizontal displacements and the time for each pair of values of elastic and viscous characteristics of the damper for Maxwell and Kelvin – Voigt models. The effect of changes in the values of stiffness and damping parameters on the values of the period and eigenfrequencies of this superstructure was also investigated. Conclusions. The co-authors chose the damper parameters to minimize seismic displacements of the bridge girder and optimally suppress the dynamic interaction between the bridge elements. Viscoelastic elements of the Kelvin – Voigt type provide more regular values of horizontal displacements of the girder when the direction of the seismic effect changes. We also recommend to select the pair of values equal to 20 000 kN/m, 800 kN s/m, and to use the Kelvin – Voigt model in the design of a viscoelastic damper.

Investigation on the Seismic Performance of High-Strength Bolt-Rubber (HSBR) Connection in a Steel Frame

The existing buildings can be improved under the seismic effect by adding rubber to the bolts in the connection. The buildings when maintenance work is happening there is a problem many times and it should be evacuated and requires high cost. This study aims to maintain the building without having to remove it and at a very low cost compared to other methods. This study includes six models divided into two groups. The two groups differ in terms of the number of bolts in the contact area between the column and the beam in the steel frame. The first group models contain four bolts in the connection area and the second group forms contain five bolts in the contact area. Each group includes three models representing the first form of a reference model that has not rubber material around the bolts in the connection area, the second model contains 150% rubber than a bolt diameter around one bolt of the connection area, and all the bolts in the connection area in the third model are warped with rubber. The presence of rubber around one bolt gave a load, displacement, drifting, damping ratio, ductility index energy dissipation close to models where all contact bolts are warped with rubber material