Journal of Seismology and Earthquake Engineering
Volume:23 Issue: 1, Winter 2021

Earthquakes are one of the most important environmental hazards, which have usually been associated with the human and financial damages. In addition to its effects on residential areas, earthquake causes displacements and changes in the ground's surface. Iranian plate is located in the convergence zone of the Arabian plate in the southwest and the Eurasian plate in the northeast; therefore, it is a tectonically unstable area. The earth's deformation and the subsidence resulting from the destructive earthquake occurrence have been as the most important natural hazards in this plate.Several methods are used to study the effects of natural hazards on the land and settlements. Radar interference technique is one of the practical methods in investigating and measuring the amount of displacement. In recent years, many space sensors have been collecting data from the surface of the earth, one of the most successful of which is the Sentinel project. Sentinel-1 is the radar section of the Sentinel project, which captures images of the Earth's surface at intervals of several days and is therefore suitable for monitoring surface changes and estimating the amount of earth movement using the radar interferometry method. In this article, the deformation related to the March 16, 2022 Kookhord-Bastak earthquake (Mw6) in the Hormozgan province is measured. The results show 19 cm of subsidence and 14 cm of uplift along the fault plane and around area during the earthquake.

Degree of saturation of soil is an important factor in preparing specimens of soil in the laboratory. The moisture content of the specimen affects its behavior, especially in undrained loading, either by change of the structure of soil or by change of effective stress path. Even though special equipment is required to measure the change of unsaturated specimen’s geometry, they are not provided in many engineering laboratories due to economic and technical reasons. One alternative for a precise measurement is to saturate the specimens. We show herein that apart from such expensive measurements and saturating the specimens even though it is not saturated in the field, estimating the change of specimen size by simplifying the relevant assumptions and resembling the degree of saturation of the field in the laboratory is to be preferred. Two case studies of monotonic and cyclic triaxial tests are reported herein to show this priority based on field tests and image processing results. It is concluded that given the variation of the degree of saturation of the soil in the field, as well as its volumetric behavior while being sheared, that is, either being compressional or dilative, are essential to make the optimal decision on the selection of the proper degree of saturation at the laboratory.

Development of different scales and methods to evaluate and compare research performance of individuals, institutes and universities has a significant role to enhance scientific policy-making procedures. Unfortunately, thematic evaluation as a tool for qualitative evaluation, has not received much attention for high-level policy-making of science and technology in the world. It seems that monitoring research trends (in specific research centers) and their similarity with those of top research institutes in the world presents a new perspective to research policy-makers and is essentially effective to find strengths and weaknesses of research approaches and future policies. In this research, the articles of the three years (2018-2019-2020) of the top 5 universities (in the 2021 QS ranking) and Ferdowsi University of Mashhad in the field of Civil and Environmental Engineering are extracted from the Scopus database. The priority of research topics is analyzed and compared based on several indicators for five top universities and Ferdowsi University of Mashhad. To validate the thematic-comparison process, researches of London College (as the sixth top research institute in the field of Civil Engineering) are also included. The results show that research topics (and their priorities) of London College, compared to Ferdowsi University, are much closer to those of the top five universities of the world. Also, in order to better evaluate the research compatibility, thematic comparison of Ferdowsi University's researches with those of the top five universities has been examined for different subfields of Civil Engineering separately. The results show that inconsistency in some sub-disciplines is very high, and research policy reconsideration is earnestly recommended.

The effect of aftershocks on structures are not usually considered in seismic design codes. In addition to mainshock events, aftershocks can cause major damage to structures, especially to mainshock-damaged structures. Analysis of the characteristics of the mainshock, foreshocks, and aftershocks reveal differences in the ground motion parameters. Structures may undergo a variety of seismic waves with different characteristics that can increase the chance of seismic amplification. The present study examined the effects of aftershock as well as foreshocks events on the response of single degree-of-freedom (SDOF) systems with nonlinear behavior. This allowed inclusion of possible differences during calculation of the response spectrum for cases having foreshock and aftershock effects and those excluding these effects. To this end, 38 mainshocks from different seismic regions with moment magnitudes (Mw) greater than 3.5 were used. More than 168 time acceleration histories from mainshock, aftershock, and foreshock events were applied to evaluate the effects of aftershocks and foreshocks on the response spectrum. The parameters of post-yield stiffness ratio (hardening and softening), ductility factor, period, and site classification were taken into account during 121,000 nonlinear analyses on 60 SDOF models. The results show that the aftershocks as well as foreshocks have a significant effect on the response spectrum, increasing the structural response. Consequently, the effect of aftershocks must be considered in the development of design spectra in seismic codes and guidelines.

In this work a value-based design approach is used to rationalize the structural design procedure in terms of initial investment and structural performance as well as other related parameters like design life span and economical conditions of the region. In this approach, at first a definition for design value is introduced in which the structural performance is converted to cost equivalent and based on this definition a value design curve for the structural system is found. Then, an optimality criterion is adapted to find a rational design point for the structural system. The results of such studies for residential occupancy shows the fact that a sub-optimal value design point for a base-isolated structural system requires much lower design shear force than the one usually recommended by code-based design approaches. According to the results, the base isolation system does not provide a strong justification to be used instead of the fixed-base system even in economies with high discount rates.

Ground-supported cylindrical tanks are used to store a variety of liquids, e.g., water for drinking and fire-fighting, crude oil and liquefied natural gas. Tanks are critical components of modern industrial facilities and life-line systems, and must be designed to withstand safely the earthquakes to which they are subjected. The failure of such systems may lead to environmental hazard, loss of valuable contents, and disruption of fire-lighting elements following destructive earthquakes. Water storage tanks in particular, are important to the continued operation of water distribution systems in the event of earthquakes. Recent earthquakes have shown liquid storage tanks to be vulnerable to damage. Elasto-plastic shell buckling which is called “Elephant’s Foot” Buckling (EFB) has been the critical aspect in the earthquake resistant design or retrofit of steel, cylindrical tanks. In this paper, an innovative method based on using seismic energy absorbing connection at the base of tank wall is introduced to protect the liquid storage tank against seismic loads. In this method, the tank wall is fully disconnected from the base plate and the special connection is provided at the bottom of the tank. The connection is supported by a ring of rigid foundation and the base plate is supported directly on the ground. The seismic performance of the method is numerically examined for one broad and one slender steel tank. It is shown that this method can prevent the EFB of the tank wall by using the plastic deformation of the connection. Numerical results confirm the efficient performance of the proposed system to reducing seismic vulnerability of shell tanks.