In existing research, the correlation between the resilience performance of the self-centering post-tensioned (SCPT) steel beam-column connections and the inelastic response of the required energy dissipation (ED) system was not addressed. For this purpose, a compact circular hollow steel tube (CHST) is proposed as a replaceable ED system. In the light of existing experimental results, a detailed three-dimensional finite element modeling (3D-FEM) was carried out to identify the response of the compact CHST under half cyclic loading. A lot of numerical work is concluded with the extraction of design charts to determine the axial strain (ΔL/L) of the ED system prior to encountering post-yield buckling. Therefore, in the numerically validated reference SCPT connection, several ED systems predesigned according to the design charts emphasized the capability of design charts to predict and control the resilient response of the connections. The optimum selection of proper inherent depth to thickness (D/t) ratio and length to depth (L/D) ratio of the CHST-ED system can increase the resilience of modern self-centering steel structures.
Soil flexibility had an obvious effect on damage of buildings during past seismic events. When a structure is subjected to earthquake, its foundation undergoes three modes of deformation, namely vertical, sliding, and rocking. Indeed, the present practice of structural design assumes that buildings are fixed at their base as a simulation of the connection between columns and foundation. However, in reality, the supporting soil flexibility especially, under the raft foundation system permits extra lateral deformation to their natural deformation. So, implementing soil-structure interaction (SSI) modeling enables the designer to assess the actual inelastic seismic performance and base shear capacity of the structural system during seismic event. In this study, three-dimensional finite element (FE) models of multi-story moderate-rise buildings of moment resisting frame (MRF) are idealized using ETABS to analyze the effects of soil flexibility underneath raft foundation on the performance based seismic design (PBSD). Winkler model spring is used for soil-structure interaction’s simulation in both vertical and horizontal directions. Comparison is carried out between different methods of soil subgrade modulus’s calculation such as FEMA, NIST, and ECP-202. Also, the results obtained for models with various soil types, and raft thickness are compared to those corresponding to fixed-base support. The findings demonstrate that numerical models using flexible (soft) soil, using ECP-202 equations, or less raft thickness have extra time period, lateral deformation, and inter-story drift (ISD) than that with fixed base or even with stiff soil. Also, the capacity curve, global ductility ratio, overstrength ratio, and damage index have evident variation of inelastic seismic performance as a result of SSI.
Structural damage identification has recently become one of the most important topics for engineering structures due to its benefits in enhancing safety, reducing life-cycle cost and providing guidance for system construction and maintenance. This research investigates the accuracy of using displacement influence lines (DILs) and their derivatives (slope and curvature) for structural damage characteristics (location and severity). The method is based on static structure response, which can be measured using single or multi sensors. The study includes an analytical investigation of damage detection of single and multiple damages in a simply supported beam. The measuring point positions are also discussed in this paper. Furthermore, the advantages and disadvantages of using displacement influence lines in structural damage detection are also discussed.
Concrete-filled steel tube (CFST) beam-column joints are susceptible to brittle premature failure due to concentrated local stresses at the tips of the beam tension flange. In order to reduce the outward deformation of the steel tube wall, this paper addresses the influence of setting the steel beam at the corner of the CFST column on the connection performance. Therefore, two specimens represented the details of the common connection and the new proposed connection of exterior joint configuration were sub-assembled and examined experimentally under lateral monotonic loading. Compared with the flexible initial stiffness attained by the common connection, the results showed that the initial stiffness of the proposed connection was relatively rigid up to yielding of the middle region of the width of the beam compression flange under high bearing stresses. The connection strength also increased up to the expected design strength of the connecting beam, while the common connection strength was close to half of the beam design strength. Moreover, after the strength of the beam connection was achieved and at a total rotation of 0.025rad, the failure of the proposed connection was a significant buckling of the beam compression flange propagated to its web and associated with section warping.
Disposal of mining wastes (tailings) is one of the most severe issues related to groundwater contamination. Therefore, a properly selected disposal site helps to prevent the leakage of dissolved materials in the tailings to groundwater, especially in the karstic area. Where the karstic environment is one of the challenges facing groundwater environmental and engineering issues, for instance, groundwater exploration, vulnerability assessment, and hazard estimation. In this study, the resistivity method with a high-resolution surface data survey was carried out to investigate the pond location selection for mining tailings disposal at El Mochito mine site, northwest Honduras. The results of the two-dimensional (2-D) inversion for sixteen surveyed lines revealed that many low resistivity zones. These zones are related to water/clay-bearing zones that are structurally weak. From lines 8-12, the limestone underneath the surface is the most compact, and this is the best location in the survey area for tailings pond construction. The resistivity method has provided insight into the subsurface information and locating hydraulically conductive zones, so it can be useful for selecting the site of mining tailings.
To detect water seepage and ensure the safety of Pumped Storage Power Station (PSPS) facilities, we apply the electrical resistivity method to evaluate the leakage when the water level is on the rise. We check whether there is a leakage channel near the cavern group of the underground powerhouse. We conduct the field survey and integrate the results with regional geological data to determine the distribution of faults and large cracks. Granite intrusions generate a variation of high and low resistance phases, representing granite porphyry and tuff, respectively. The interface between the two lithologies is the location of the fault zone. In general, the apparent resistivity of two does not change much, indicating that the rock masses are relatively stable. The internal fractures of the rock masses are not developed, and there is no visible water content. However, from the location of the lithological contact interface, the rock mass is broken. Therefore, we recommend that before constructing the lower reservoir, anti-seepage treatment should be carried out.
Sulfide minerals are a group of compounds with the presence of sulfur. This group’s most abundant and economically members are pyrites, pyrrhotite, chalcocite, galena, sphalerite, and the group of copper sulfides minerals. Resistivity and Induced Polarization (IP) methods, which play an essential role in mineral exploration, showed great success in sulfide exploration. This paper started on reviewing sulfide formation by giving details which help to understand their genesis better. To make the reader understand the procedures and appropriate mineral exploration methods, we have briefly covered the theory, the basic principles of resistivity and IP methods, and different investigation techniques using one, two, and three-dimensional surveys. Based on many electrical surveys, we discussed with examples of resistivity and IP methods applied to the exploration of sulfide deposits: the data inversion and interpretation of the geophysical signatures of most of the sulfide deposits in various geological environments were analyzed and end by showing both successful surveys and limitations of the methods.
The geoelectrical tomography survey was carried out to explore and characterize a (Zn-Pb-Ag) sulphide deposit in Nash Creek (NC), New Brunswick province, Canada. The exploration strategy has been conducted by the 2-D survey for a well-cut grid consisting of twelve surface lines (profiles) each around 2 km long, and 300 m apart, for the total area around 9.5 km2. The datasets (resistivity and induced polarization) were acquired using the Iris El-Rec Pro system with pole-dipole electrodes array spaced 50 m apart, and ten levels of data datum. The results of the 2-D inversion revealed that the underground resistivity and chargeability values in the exploration area have a range of (5 to 1300 Ωm) and (0-9.5 mV/V), respectively. The sulphide mineralization zones in the exploration area are characterized by moderate resistivity values (150-300 Ωm) and moderate to low chargeability values (>5.5 mV/V), with a depth of around (90140 m) from the surface. The 3-D visualization model clearly reveals that three main zones of sulphide mineralization are present in the exploration area. The predicted geological reserve of the sulphide ore in the exploration area was calculated. The inverted models revealed a good agreement with the existing geological features in the exploration area.
