Earthquakes Of Different Intensities Research Articles

Seismic performance of prefabricated replaceable graded-yielding energy-dissipating connectors

In conventional reinforced concrete and assembled monolithic concrete frame structures, considerable damage typically occurs in the beam–column joint zone under strong seismic activity. To improve seismic performance and earthquake resilience, a novel replaceable graded-yielding energy-dissipating connector (RGEC) for prefabricated concrete beam–column joints is proposed. In these joints, RGECs are assembled on the upper and lower sides of the beam end. These connectors enable the concentration of plastic deformation on their bending–shear components (BSCs) and buckling segment (BS). Consequently, structural seismic performance can be rapidly restored by replacing the RGECs after an earthquake. An RGEC can realize graded-yielding energy dissipation under earthquakes of different intensities with the successive yielding of BSCs and BS. Mechanical models of the BSC and BS are developed, and a series of tests is performed on 11 specimens. The tests examine the effects of key design factors (such as core plate thickness, width–thickness ratio of the BS, limit gap width, yield stress contour height ratio, and height–width ratio of the BSC) on the seismic behavior of the proposed damper. Results indicate that the RGEC exhibits excellent seismic performance in terms of strength capacity, deformation capacity, energy dissipation capacity, and stiffness degradation. The RGEC can effectively achieve energy dissipation through graded yielding under loads of multilevel intensities. Additionally, based on finite element models validated using available test data, the deformation behavior of the RGEC is analyzed by considering the influences of the yield stress contour height ratio and height–width ratio of the BSC, width–thickness ratio of the BS, and out-of-plane restraint gap width.

Experimental investigation of the seismic performance of caisson foundations supporting bridge piers

Allowing the transitory attainment of bearing capacity of caisson foundations supporting bridge piers during strong seismic events can lead to substantial optimisation in their design and major cost savings. If the approach of capacity design is applied to geotechnical systems, the temporary triggering of plastic mechanisms may be permitted if the resulting permanent displacements are smaller than given threshold values. To validate this design approach, the seismic performance of caisson foundations was assessed through dynamic centrifuge testing on reduced-scale models. This paper presents the results of two tests in which a caisson–pier–deck system was embedded in a typical alluvial deposit and subjected to a series of earthquakes of different intensities. The caissons were founded on soft and very soft clay, to either avoid or induce the attainment of plastic soil behaviour under the same seismic inputs. It is shown that both yielding and failure of the layer of very soft clay limit inertial forces transmitted to the superstructure, validating the design approach and some useful empirical relations available in the literature. In contrast, inelastic soil behaviour implies accumulation of permanent rotation and settlement of the system, which must be carefully evaluated to check for fulfilment of performance requirements.

A novel energy dissipation damper for multi-level earthquakes

This paper presents a novel energy dissipation damper for multi-level earthquakes. The dampers possess two obvious yield points by using the preset gaps, so the dampers can realize graded yielding energy dissipation under earthquakes of different intensities. Firstly, the working mechanism and configuration details were introduced. Secondly, the cyclic loading tests were carried out on four specimens with different parameters. Subsequently, the ABAQUS program was used to simulate the deformation development process of the damper. Finally, the quadrilinear kinematic hardening model of the damper was proposed by the theoretical analysis. The test results show that the dampers possess stable energy dissipation behavior and can effectively achieve graded yielding energy dissipation under earthquakes of the multi-level intensities, the simulation results are in good agreement with the experimental results, indicating that the established finite element model can simulate the hysteretic behavior of the dampers well. The calculation results of quadrilinear kinematic hardening model are in good accordance with test results, demonstrating that the proposed restoring force model can reasonably predict the cyclic response of the damper.

Hybrid self-centering rocking core system with fiction spring and viscous dampers for seismic resilience

This research presents a novel aseismic system, the hybrid self-centering rocking core (HSRC) system, for obtaining better seismic resilience in steel buildings. Two hybrid self-centering dampers are introduced in the HSRC system to control structural and nonstructural damage. A rocking core, i.e., a steel braced frame with pinned base is included in the HSRC system to facilitate uniform inter-story drift responses under earthquakes. The steel braces in the rocking core can also work as a reserve energy-absorbing mechanism against structural collapse subjected to extreme seismic events whose intensities are more significant than those of the maximum considered earthquakes in design codes. The desired nonlinear responses of the HSRC system were analyzed. Direct displacement-based design steps were developed for the HSRC system. Three-story and six-story HSRC systems were designed following the proposed design method. Nonlinear dynamic analysis results indicate that the designed HSRC systems can show desired nonlinear responses and achieve the expected performance objective under earthquakes. Moreover, seismic fragility analyses were also conducted based on the incremental dynamic analysis results to assess the performance in controlling structural and nonstructural damages of the HSRC system under earthquakes of different intensities. The results confirm that the proposed HSRC system has excellent capacity in resisting structural collapse, achieving reliable post-earthquake recoverability, and controlling structural and nonstructural damage under rare seismic events.

Damage Assessment of Reinforced Concrete Structures: A Review

Damage may be assessed using several damage indices with values associated with different structural damage states. The usefulness of a variety of current response-based damage indices in seismic damage assessment is addressed and critically assessed. A novel rational damage assessment method is provided, which measures the structure’s physical reaction characteristics. A practical method based on various analyses is given to evaluate the damaged structures in earthquakes of different intensities. This paper provides an overview of previous research works on the damage assessment of the reinforced concrete structures. This study may be helpful for easy understanding about the damage assessment of reinforced concrete structures and reduce the impacts of disaster and surrounding structures.

Damage Assessment of Reinforced Concrete Structures: A Review

Damage may be assessed using several damage indices with values associated with different structural damage states. The usefulness of a variety of current response-based damage indices in seismic damage assessment is addressed and critically assessed. A novel rational damage assessment method is provided, which measures the structure’s physical reaction characteristics. A practical method based on various analyses is given to evaluate the damaged structures in earthquakes of different intensities. This paper provides an overview of previous research works on the damage assessment of the reinforced concrete structures. This study may be helpful for easy understanding about the damage assessment of reinforced concrete structures and reduce the impacts of disaster and surrounding structures.

Effects of soil-structure interaction on the damage of bridge piers subjected to earthquakes

When an earthquake occurs, interaction between soil and a structure is obvious. However, the effect of this interaction is often neglected in most of the design of structures because of its simplicity, but this simplicity can be unsafe for the structures. This paper analyzes the influence of soil-structure interaction on the damage index of reinforced concrete (RC) bridge piers subjected to earthquakes. To achieve this aim, an RC bridge pier, which was constructed and tested in practice, was selected for analyses. The selected RC bridge pier was modelled using nonlinear hysteretic elements. The model of the RC bridge pier was verified by comparing the results obtained from the model with the experimental results. Time-history nonlinear analyses of the RC bridge pier subjected to earthquakes of different intensities were performed. The results of these nonlinear analyses were used for damage analyses. The results of damage analyses were compared to draw some conclusions as follows. The comparison results showed that the soil-structure interaction hardly changed the damage index of the bridge pier when the earthquakes were of moderate and weak intensity. However, the soil-structure interaction significantly increased the damage index when the pier was subjected to strong earthquakes. Therefore, instead of being ignored, the soil-structure interaction should be carefully analyzed when designing reinforced concrete piers subjected to earthquakes.

Seismic performance of Al-wand earth dam: numerical analysis

The seismic can be threatened the stability of the flexible body of the earth dam and can cause completely damaged or deformation on their embankment. Therefore, a geotechnical engineer needs to know the effect of earthquakes on earth structures. The change in the seismic zone that recently Iraq affected is the reason for this research, in general, in 2017, the whole of Iraq, and in particular the region, where the Al-Wand earth dam (the subject of the study) is located, was exposed to several earthquakes. This research project mainly aims to study the behavior of Al-Wand earth dam under seismic load in different conditions by simulating Al-Wand earth dam through numerical modeling and study the influence of water reservoir level, earthquake peak acceleration, and duration. This paper includes an analytical study of the effect of this earthquake on Al-wand earth dam, using the quake/w program, which is a sub-program of geo-studio, also the stability of the dam was studied under the influence of earthquakes of different intensity, and a review of the impact of different water levels on the stability of the body dam. Where the response of the Al-wand dam was analyzed to earthquakes at the normal and the maximum water level, and by using a quake that may have been exposed to Iraq in 2017 and used the time of 100 seconds and using an acceleration of 0.02g, 0.03g, 0.05g measured by units of ground acceleration to identify the behavior of displacements, effective stress and pore water pressure during the earthquake.

Seismic performances of a structure equipped with a large mass ratio multiple tuned mass damper

SummaryThis paper focuses on improvement of structural seismic performance under earthquakes of different intensities using a large mass ratio multiple tuned mass damper (LMTMD). A thermal power plant was taken as the example, and the plant was modeled using the finite element software ABAQUS. Coal buckets, which comprised 29.2% of the total mass of the structure, were used as the mass of the LMTMD. Thus, a large mass ratio was easily achieved without adding any extra mass. Incremental dynamic analysis was used to investigate the seismic fragility of the structures, and the seismic performances of the structure equipped with the LMTMD and the original structure were compared. The damping effectiveness and the control reliability of the LMTMD were evaluated. The fragility curves show that under rare earthquakes, the LMTMD reduced the probability of the moderate damage limit state by 43.9%, and under extremely rare earthquakes, the LMTMD exhibited good control robustness and reduced the probability of the severe damage limit state by 25.1%. Furthermore, the LMTMD could control the deformation pattern of the structure and effectively reduced concentrated damage, especially under high‐intensity ground motions; specifically, it reduced the average value of the interstory drift ratio by 1.2%–12% and reduced the standard deviation of the interstory drift ratio by 15%–62%. These results indicate that the LMTMD significantly improved the seismic performance of the structure with satisfactory reliability.

NATURAL DISASTERS AND NATURAL DISASTER PERCEPTION IN THE STATE OF ASSYRIA

Tarih boyunca her coğrafyada insanoğlu çeşitli doğal afetler ile karşı karşıya gelmiştir. Felaketler, doğal kaynaklı olduğu gibi insan ihmalinin sonucunda da gerçekleşebilir. Beklenmedik zamanda ve aniden meydana gelen, önlem alınmadığı zaman can ve mal kaybına neden olan afetler toplumlar için çok üzücü olmuştur. Bu çalışmamızda Asur Devleti’nde meydana gelen doğal afetler ile Asur halkındaki afet algısını ortaya koymaya çalıştık. İncelemiş olduğumuz belgelerden; depremler, sel baskınları, kuraklık, kıtlık, salgın hastalıklar, haşere istilaları ve yangınlar konusunda bilgiye ulaştık. Asur tarihi boyunca farklı şiddetlerde depremler olduğu anlaşılmaktadır. Mevsimlere göre sel baskınlarının gerçekleştiği zamanlar ya da kurak dönemler yaşanmıştır. Kuraklık, haşere istilası ve nüfusun artması gibi durumlarda kıtlık ortaya çıkmıştır. Elimizdeki mevcut bilgilerden anlaşıldığına göre, özellikle Asur ordusunun başına gelen en büyük felaket salgın hastalıklardır. Asur Devleti’nde insan ihmalinin bir sonucu olan yangınlar da meydana gelmiştir. Asurlular başlarına gelen felaketleri tanrının ikazı olarak telakki etmişler ve doğal afetleri tanrıların oluşturduğunu düşünmüşlerdir. Olayların dini yönü ağır bastığı için bilimsel tekniklerle önlem almak yerine kötülüğe karşı dinsel ayinlere yönelmişlerdir. Bu sebeple krallar kötü alametleri ortadan kaldırmak için ritüeller düzenlemişlerdir. Ayrıca tanrıların kendileriyle ilgili kararlar verdiğine inanan Asurlular, insanlara verilmek istenen mesajları öğrenmek için göksel kehanetlere başvurmuşlardır. Gökyüzünde olumsuz gördükleri kehanetleri, yeryüzünde olacak kötü olayların işareti şeklinde yorumlamışlar ve kehanetlere göre tedbir almışlardır.

Shaking table tests on shaft-tunnel junction under longitudinal excitations

Shaking table tests are conducted to study the discrepant responses of shaft-tunnel junction. The cases with transverse excitations are introduced in a previous paper, while the current paper mainly addresses the responses under longitudinal excitations. A brief introduction is provided on the design of the tests. Data of accelerations, dynamic strains, and circumferential-joint extensions are presented in four cases. Two white-noise cases are conducted to evaluate dynamic characters of the model system as well as examine repeatability of the test results. Two synthetic-earthquake-motion cases are conducted to study the seismic responses of the shaft-tunnel junction under natural earthquakes of different intensities. As revealed by the acceleration data, the shaft and the tunnel have exhibited quite different dynamic characters under longitudinal excitations. The extent of shaft-tunnel discrepancy is statistically quantified by correlational method. Although transverse strains of the tunnel are slightly elevated at the shaft-tunnel junction, absolute values of the strains remain in a lower range which is below 65 με. However, the discrepant responses have caused tensile deformations of the tunnel, which eventually lead to significant circumferential-joint extensions near the shaft. A simplified analytical model is proposed to establish the relationship between the discrepant responses and the longitudinal deformations of the tunnel. At the end, testing data from the transverse-excitation and the longitudinal-excitation cases are compared. In both cases, the shaft-tunnel relative displacement and the soil-tunnel relative stiffness are considered as the two key factors.

Study of an innovative graded yield metal damper

Metal dampers have been widely used to improve the seismic performance of the building structure. However, conventional metal dampers only possess one yield point and cannot protect the structure efficiently under earthquakes of different intensities. A new type of metal damper composed of two annular metal dampers with different sizes is proposed in this paper. It is a graded yield metal damper having two yield points, which can be used to reduce the responses of the structure efficiently under earthquakes of different intensities. Firstly, the mechanical properties of single annular metal damper, such as the failure mechanism, hysteretic behavior and anti-fatigue performance, are investigated by cyclic loading tests. The test results show that the annular metal dampers possess large deformation capacity and energy-dissipation capacity as well as excellent anti-fatigue performance. The calculation formulae are derived to determine major mechanical parameters of the damper. The theoretical results obtained by using the proposed calculation formulae are in good agreement with experimental results. Cyclic loading tests are carried out on the graded yield metal damper. The yielding process of the graded yield metal damper is simulated using the ABAQUS program. The trilinear kinematic hardening model is adopted to simulate the hysteretic behavior of the damper. Nonlinear time history analyses are carried out to compare the responses of a conventional reinforced concrete (RC) moment-resisting frame structure with that of the structure installed with the graded yield metal dampers under three levels of earthquakes using SAP2000. The results indicate that the seismic performance of the structure installed with the graded yield metal dampers under all levels of earthquakes is improved significantly. The graded yield metal dampers are more effective in displacement control of reinforced concrete moment-resisting frame structure in comparison with single yield point metal dampers.

Метод анализа риска аварий на магистральных газопроводах в зонах активных тектонических разломов

The considerable part of the Russian Federation’s territory is characterized by high seismic activity. More than 20% of the territory belongs to earthquake zones where earthquake shocks exceeding 7 on the Richter scale are possible, about 5% of the territory is vulnerable to seismic impact with intensity up to 8–9. Beside that the intensive development of mining industry and also hydroelectric development can lead to technogenic earthquakes. During strong earthquakes sometimes emerge faults (breaks) of land constituting essential danger to engineering constructions, in particular to the main pipelines in active tectonic fault zones, where soil displacements up to several meters are possible. In this work a method of failures risk assessment for main gas pipelines in zones with active tectonic faults has been presented. The method is based on correlation dependence of accident risk on the frequency of earthquake in the considered area and probability for exit of seismic fault to the surface during earthquakes of different intensity. The dependence of accident probability on a gas pipeline from the seismic event intensity has been proved. Accident frequency was defined with due regard to gas pipelines’ accidents intensity for the last 10 years, and frequency of earthquakes near constructions. Earthquakes incidence was accepted according to the maps for general seismic zoning OSR‑97. The need for fault existence accounting has been confirmed by statistical data’ calculation and analysis. The example for risk calculation on a main gas pipeline has been presented. The considered method can be used at the main pipelines design in seismically dangerous areas, and also for assessment the efficiency of actions for decreasing the risks indicators for extended linear objects in zones where these ones cross over active tectonic faults.

Dynamic soil-structure interaction: A three-dimensional numerical approach and its application to the Lotung case study

This paper presents a three-dimensional non-linear finite element (FE) approach to analyse the dynamic soil-structure interaction (SSI) phenomena observed at the Lotung Large-Scale Seismic Test (LSST) site. The numerical study is carried out in the time domain by a commercial FE code, taking into account the non-linear behaviour of soil and the multi-directional nature of real seismic events. The soil response is simulated by an isotropic hardening elasto-plastic hysteretic model (HSsmall) implemented in the material model library of the code. This model allows to describe the non-linear cyclic response ranging from small to large strain amplitudes and to account for the variation of the initial stiffness with depth.In the paper, the FE numerical approach is first validated through a series of parametric analyses simulating simplified cases (i.e. linear visco-elastic structures founded on a homogeneous linear visco-elastic soil deposit) for which analytical solutions exist. Then, it is adopted to back-analyse the behaviour of the 1/4-scale nuclear power plant containment structure constructed at the Lotung LSST site which was shook by several earthquakes of different intensities and frequency contents. The FE results are thus compared to the recorded in-situ free-field and structural motions, highlighting the satisfactory performance of the numerical model in replicating the observed response. The overall outcome of this research proves that nowadays complex dynamic SSI phenomena can be tackled by direct approach, overpassing the strong simplifications of the well-established substructure approaches.

Minimum life-cycle cost-based optimal design of yielding metallic devices for seismic loads

The yielding metallic devices have been used to improve the performance of building structures at design level intensities. They dissipate large levels of vibration energy through yielding of disposable steel plate elements but they may also enhance acceleration response related damage of mechanical and electrical components. This paper addresses the optimal design of these devices that minimizes the expected life-cycle object cost considering the story drift and acceleration related damages over the entire spectrum of seismic intensities that can occur on a building site. Genetic algorithm is used to calculate the optimal design parameters of the devices. The uncertainties associated with the frequency of occurrence of earthquakes of different intensities and random characteristics of the structural response are included in the life-cycle failure cost and the object cost calculations. It shown that these devices can be used effectively to reduce the overall life-cycle object cost and can be considered as good protective investment for structural designs in seismic regions.

DEPENDENCE OF DISTRIBUTION FUNCTION OF COMMERCIAL DAMAGES DUE TO POSSIBLE EARTHQUAKES ON THE CLASS OF SEISMIC RESISTANCE OF A BUILDING

Objectives To determine the damage probability of earthquakes of different intensities on the example of a real projected railway station building having a framework design scheme based on the density function of damage distribution. Methods Uncertainty, always existing in nature, invalidates a deterministic approach to the assessment of territorial seismic hazards and, consequently, seismic risk. In this case, seismic risk assessment can be carried out on a probabilistic basis. Thus, the risk will always be there, but it must be minimised. The task of optimising the reinforcement costs is solved by using the density distribution function for seismic effects of varying intensity, taking into account the degree of building responsibility. Results The distribution functions of the expected damage for a building with a reinforced concrete frame located in a highly seismic region with a repetition of 9-point shocks every 500 years and 10-point shocks once every 5000 years are constructed. A significant effect of the seismic resistance class of a building on the form of the distribution functions is shown. For structures of a high seismic resistance class, not only is the seismic risk reduced, but also the variance of the expected damage. From the graphs obtained, it can be seen that the seismic resistance class significantly affects the damage distribution. At a probability of 0.997, the expected damage for a non-reinforced building will exceed 43%; for a reinforced one it is only 10%. It also follows from the graphs that the variance of the damage magnitude decreases with the growth of the seismic resistance class of the building. This fact is an additional incentive for investing in antiseismic reinforcement of buildings. Conclusion The study shows the expediency of working with the damage density distribution function when managing seismic risk. In this case, it becomes possible to strengthen the building with a specified probability of damage exceeding the acceptable level during the operation of the construction. This takes into account not only seismic risk (mathematical expectation of damage), but also the dispersion of the expected magnitude of the damage. With the growth of seismic resistance class of the construction, it is possible to reduce both the risk and dispersion of possible losses.

A new method to assess damage to RCMRFs from period elongation and Park–Ang damage index using IDA

Despite a significant progress in loading and design codes of seismic resistant structures and technology improvements in building structures, the field of civil engineering is still facing critical challenges. An example of those challenges is the assessment of the state of damage that has been imposed to a structure after earthquakes of different intensities. To determine the operability of a structure and its resistance to probable future earthquakes, quick assessment of damages and determining the operability of a structure after an earthquake are crucial. Present methods to calculate damage to structures are time consuming and do not accurately provide the rate of damage. Damage estimation is important task in the fields of structural health monitoring and decision-making. This study examines the relationship between period elongation and the Park–Ang damage index. A dynamic non-linear analysis is employed with IDARC program to calculate the amount of damage and period of the current state. This new method is shown to be a quick and accurate technique for damage assessment. It is easy to calculate the period of an existing structure and changes in the period which reflects changes in the stiffness matrix.

Experimental Study on Behaviors of Adaptive-slit Shear Walls

In order to meet the needs of performance-based seismic design, a new type of adaptive-slit shear wall that is easy to construct and behaves well under cyclic loading is introduced to improve the seismic performance of conventional shear wall structures. The seismic damage of an adaptive-slit shear wall develops gradually and it transforms from integral wall into slit wall. The mechanical characteristics of adaptive-slit shear walls suggest that such walls are adaptive to various seismic requirements under earthquakes of different intensities. Compared with conventional shear walls, the new wall is highly ductile and is advantageous in controlling the seismic damage process.

Nonlinear analysis of out‐of‐plane masonry façades: full dynamic versus pushover methods by rigid body and spring model

SUMMARYThe paper proposes a systematic comparison between two methods of analysis that are well established in the field of earthquake engineering: nonlinear dynamic analysis and nonlinear static procedure (NSP), applied to the out‐of‐plane seismic response of two masonry façades representative of many ancient Italian churches. The comparison is based on extensive numerical analyses, which focus on the flexural and torsional mechanisms, while the in‐plane damage mechanisms and the possible detachment between the façade and the lateral walls because of a poor connection have been presently disregarded. The computations, both in the static and in the dynamic field, are based on a rigid body and spring model specifically implemented for this issue, computationally efficient and equipped with a realistic model of damage and hysteresis at the mesoscale. An innovative aspect of this study is the heuristic modelling of three‐wythe masonry, to include some typical texture effects on the macroscale nonlinear response. For each façade, two different masonry textures were considered, performing extensive dynamic analyses that offered a detailed overview about the performance under earthquakes of different intensities. In parallel, NSP and the classical N2‐based seismic assessment were applied. A critical discussion and comparison of the results of the two methods is presented to rationally appraise limits and opportunities. In particular, flexural and twisting out‐of‐plane mechanisms were clearly appraised in the dynamic field, whereas NSPs were not always able to describe the collapse, because they missed the partial failures determined by higher vibration modes, as could be expected. Copyright © 2012 John Wiley & Sons, Ltd.

Drift analysis due to earthquake load on tall structures

Earthquake is one of the destructive events in the world. Prediction of earthquake is not feasible at all. In the horizon, earthquakes of different intensities and magnitudes occurred. So it is a threat to all especially the tall structures of the mega cities. Due to shaking of ground surface, the substructure as well as the superstructure is vibrated. During earthquake, there will be a drift on the high rise structures. Then it can be included that the more the height, the more the drift. The drift of the structure decreases with increase in the width of the structure. So our concern is to calculate the drift of tall structures due to the vibration of ground. Hand calculation and programming with C (version C++ 4.5) is used to calculate the drift. Key words: Earthquake, drift, tall building, lateral deflection, laterals forces.