Earthquake Energy Research Articles

Experimental study of Pipe-Fuse Damper for passive energy dissipation in structures

This study presents a novel passive metallic damper, Pipe-Fuse Damper (PFD), to improve the seismic response of structures with dissipation of the earthquake energy. The Fuse Damper (FD) was recently introduced by using steel bars as fuses, Bar-Fuse Damper (BFD), and its performance was evaluated experimentally. The Fuse Damper (FD) is built using common cross-sections found in engineering structures, such as square hollow sections (SHS) and U-shaped sections as well as metal sheets. As a special feature, the Fuse Damper (FD) uses replaceable components as an energy-absorber part with both flexural and tensile energy dissipating mechanisms. In this study, the Fuse Damper (FD) was evaluated with components of steel pipes experimentally and numerically. To assess the individual performance of this damper, the Pipe-Fuse Damper (PFD), a series of monotonic and cyclic experiments were conducted on real-scale specimens. The studied parameters for this replaceable element in the experiments were the number of pipes and their diameter, length, and thickness. The results indicate that, in addition to demonstrating a stable hysteretic behaviour and considerable energy dissipation within an appropriate displacement reversal, the proposed damper offers the easy replacement of pipe components after each failure. Moreover, the Pipe-Fuse Damper (PFD) showed less pinching effects on its hysteresis and a higher energy dissipation compared to the Bar-Fuse Damper (BFD) under the same conditions.

Model Of Precast Beam-Column Connection Towards Structure Rigidity By Using Steel Plate Causes By Cyclic Load

Precast connection system in structure element must be designed in such way to result in required behaviour, such as plastic hingesmust be well-planned to be able to shed earthquake energy and to limit seismic loading that goes inside the structure. This research is experimental study that precast beam connection which is modeled using steel plate. The result of this model design use to compare the occurence of structure deformity rigidity in monolith concrete construction (BN) and precast concrete (BP1 and BP2). The testing dimension consists of column with the size 300x300 mm and height 3300mm, beam 200x300 mm and width 3300 mm, with steel plate 200x400x8 mm and 300x400x8. This study resulted in monolith testing material (BN) produces average value 47.8 % from its previous rigidity, BP1is 57.13% from its previous rigidity, and BP2 is 52.22% from its previous rigidity.

Seismic status in Bangladesh

Seismic status in Bangladesh

Radiated seismic energy of earthquakes in the south–central region of the Gulf of California, Mexico

Radiated seismic energy of earthquakes in the south–central region of the Gulf of California, Mexico

Equivalent Energy Design Procedure for Earthquake Resilient Fused Structures

It has been observed in recent earthquakes worldwide that even countries with modern building codes suffer significant structural damages because earthquake energy is dissipated through inelastic deformation of structural components. Unrecoverable damages and prolonged downtime can be minimized using earthquake resilient structures, where earthquake energy is dissipated using specially designed and detailed structural fuses. Fuses are decoupled from gravity system and can be replaced efficiently. Earthquake-resilient fused structures cannot be routinely designed unless there is a simple design procedure. This paper presents an equivalent energy design procedure (EEDP) for the seismic design of fused structures. EEDP allows designers to select different performance objectives at different earthquake shaking intensities. EEDP also allows engineers to select structural members to achieve the desired structural period, strength, and deformation with simple hand calculations without iterations. This practical and efficient design procedure is illustrated via an earthquake resilient fused truss moment frame (FTMF). The nonlinear dynamic analysis result shows that the prototype FTMF can have controlled failure mechanism and drifts selected by the engineer at multiple earthquake shaking intensities.

Using surface wave amplitude spectra to estimate the source depth of Sichuan Jiuzhaigou <italic>M</italic>7.0 earthquake

The accurate source depth of earthquake is important for understanding plate-tectonic processes and structure of seismic faults, identifying natural earthquake and non-natural earthquake. The amplitude formula of seismic surface wave shows that the amplitude of surface wave is closely related to the focal mechanism, the azimuth from epicenter to station and the source depth. When the focal mechanism and the observation position are determined, the excitation energy of surface wave is sensitive to source depth. The surface wave amplitude spectrum can be applied to determine the focal depth. The amplitude energy of shallow earthquake shows the “notch” phenomenon in band of frequency between 0.01 and 0.08 Hz in amplitude spectra, i.e. the attenuation of amplitude energy. The position of the frequency-dependent “notch” is related to the source depth. In this study, the relationship between the position of the “notch” and the source depth is analyzed by theoretical seismogram. We obtain the amplitude spectrums of the far-field at different source depths and then locate the source depth by means of comparing with observed seismic waveforms. By the amplitude spectrum of theoretical surface wave, small changes in the source depth can cause the variation of the amplitude spectrum so that the source depth of shallow earthquake can be accurately determined. The focal mechanism is coupled with the source depth. In order to analyze the influence of the disturbance of source mechanism to source depth determination, the focal mechanism of Jiuzhaigou earthquake was inversed, with disturbance of 10 degrees to strike, dip and rake. The results show only rather small changes in locating depth. In order to eliminate the influence of low frequency noise, shear wave and surface wave of short-period on amplitude spectra, this study adopts the AK135 velocity model to remove the dispersion. In this study, the seismic source depth of the Jiuzhaigou M 7.0 earthquake of 8 August 2017 in Sichuan province, China, was determined at 8.2 km by the energy attenuation characteristics of Rayleigh amplitude spectrum.

Calculating the Station Corrections to Earthquake Energy Class and the Acoustic Impedance for Kamchatka Stations

This paper describes a method for calculating the station corrections to earthquake energy class and the acoustic impedance based on records of earthquake codas in the 0.8–1.8 Hz frequency band. The calculation is based on measurements of the relative coda level at two stations, with one of the two being used as the reference. The data were recorded by digital seismometers: CMG-3TB (GURALP), CMG-5TD (GURALP), CMG-6TD (GURALP), and GMS-AC-73i HHV (GeoSIG). We present estimates of class corrections for the Kamchatka network of seismic stations.

LANDSLIDES TRIGGERED BY THE 2015 GORKHA, NEPAL EARTHQUAKE

Abstract. The 25 April 2015 Gorkha Mw 7.8 earthquake in central Nepal caused a large number of casualties and serious property losses, and also induced numerous landslides. Based on visual interpretation of high-resolution optical satellite images pre- and post-earthquake and field reconnaissance, we delineated 47,200 coseismic landslides with a total distribution extent more than 35,000 km2, which occupy a total area about 110 km2. On the basis of a scale relationship between landslide area (A) and volume (V), V = 1.3147 × A1.2085, the total volume of the coseismic landslides is estimated to be about 9.64 × 108 m3. Calculation yields that the landslide number density, area density, and volume density are 1.32 km−2, 0.31 %, and 0.027 m, respectively. The spatial distribution of these landslides is consistent with that of the mainshock and aftershocks and the inferred causative fault, indicating the effect of the earthquake energy release on the pattern on coseismic landslides. This study provides a new, more detailed and objective inventory of the landslides triggered by the Gorkha earthquake, which would be significant for further study of genesis of coseismic landslides, hazard assessment and the long-term impact of the slope failure on the geological environment in the earthquake-scarred region.

Seismic Study of Application of Lead Rubber Bearings in Kutai Kartanegara Steel Arch Bridge

The basic concept of the application of base isolation is by extending the natural period of the structure in order to provide lower seismic acceleration. The paper focuses on the investigation of application of lead rubber bearings (LRBs) instead of pot bearings in a new Kutai Kartanegara steel arch bridge located in East Kalimantan province. Even though the bridge is known located in Seismic Zone 1 (the zone with the least seismic risk as per RSNI 2833-201X), the study was extended for other higher risk seismic zones, namely Seismic Zones 2, 3, and 4. With the aid of Midas software, the analyses of the bridge structures were carried out and it can be concluded that the higher the seismic risk, the more effective the use of LRBs in dissipating the earthquake energy before transmitting to the bridge superstructure. The reduction of seismic base shears obtained from the analyses were between 23.10 and 44.67 percent and 17.07 and 31.47 percent in the longitudinal and transverse directions, respectively. However, the application of LRBs has a consequence of increasing the horizontal displacements of the bridge, which can be solved by introducing either larger expansion joints or passive dampers. Furthermore to validate the seismic responses, the bridge was analyzed using Time History Analysis (THA) by imposing seven earthquake ground motions, which were scaled to spectral design of Padang as a requirement by Indonesian code.

Seismic Moment, Seismic Energy, and Source Duration of Slow Earthquakes: Application of Brownian slow earthquake model to three major subduction zones

AbstractTectonic tremors, low‐frequency earthquakes, very low‐frequency earthquakes, and slow slip events are all regarded as components of broadband slow earthquakes, which can be modeled as a stochastic process using Brownian motion. Here we show that the Brownian slow earthquake model provides theoretical relationships among the seismic moment, seismic energy, and source duration of slow earthquakes and that this model explains various estimates of these quantities in three major subduction zones: Japan, Cascadia, and Mexico. While the estimates for these three regions are similar at the seismological frequencies, the seismic moment rates are significantly different in the geodetic observation. This difference is ascribed to the difference in the characteristic times of the Brownian slow earthquake model, which is controlled by the width of the source area. We also show that the model can include non‐Gaussian fluctuations, which better explains recent findings of a near‐constant source duration for low‐frequency earthquake families.

Hysteretic Energy Demand in SDOF Structures Subjected to an Earthquake Excitation: Analytical and Empirical Results

In energy-based seismic design approach, earthquake ground motion is considered as an energy input to structures. The earthquake input energy is the total of energy components such as kinetic energy, damping energy, elastic strain energy and hysteretic energy, which contributes the most to structural damage. In literature, there are many empirical formulas based on the hysteretic model, damping ratio and ductility in order to estimate hysteretic energy, whereas they do not directly consider the ground motion characteristics. This paper uses nonlinear time history (NLTH) analysis for energy calculations and presents the distribution of earthquake input energy and hysteretic energy of single-degree-of-freedom (SDOF) systems over the ground motion duration. Seven real earthquakes recorded on the same soil profile and three different bilinear SDOF systems having constant ductility ratio and different natural periods are selected to perform NLTH analyses. As results of nonlinear dynamic analyses, input and hysteretic energies per unit masses are graphically obtained. The hysteretic energy to input energy ratio ( E H / E I ) is investigated, as well as the ratio of other energy components to energy input. E H / E I ratios of NLTH analysis are compared to the results of empirical approximations related E H / E I ratio and a reasonable agreement is observed. The average of E H / E I ratio is found to be between 0.468 and 0.488 meaning nearly half of the earthquake energy input is dissipated through the hysteretic behavior.

Earthquake behavior of steel cushion-implemented reinforced concrete frames

The earthquake performance of vulnerable structures can be increased by the implementation of supplementary energy-dissipative metallic elements. The main aim of this paper is to describe the earthquake behavior of steel cushion-implemented reinforced concrete frames (SCI-RCFR) in terms of displacement demands and energy components. Several quasi-static experiments were performed on steel cushions (SC) installed in reinforced concrete (RC) frames. The test results served as the basis of the analytical models of SCs and a bare reinforced concrete frame (B-RCFR). These models were integrated in order to obtain the resulting analytical model of the SCI-RCFR. Nonlinear-time history analyses (NTHA) were performed on the SCI-RCFR under the effects of the selected earthquake data set. According to the NTHA, SC application is an effective technique for increasing the seismic performance of RC structures. The main portion of the earthquake input energy was dissipated through SCs. SCs succeeded in decreasing the plastic energy demand on structural elements by almost 50% at distinct drift levels.

Earthquake Damping Device for Steel Frame

Structures such as buildings, bridges and towers are prone to collapse when natural phenomena like earthquake occurred. Therefore, many design codes are reviewed and new technologies are introduced to resist earthquake energy especially on building to avoid collapse. The tuned mass damper is one of the earthquake reduction products introduced on structures to minimise the earthquake effect. This study aims to analyse the effectiveness of tuned mass damper by experimental works and finite element modelling. The comparisons are made between these two models under harmonic excitation. Based on the result, it is proven that installing tuned mass damper will reduce the dynamic response of the frame but only in several input frequencies. At the highest input frequency applied, the tuned mass damper failed to reduce the responses. In conclusion, in order to use a proper design of damper, detailed analysis must be carried out to have sufficient design based on the location of the structures with specific ground accelerations.

INVESTIGATION OF STRONG COLUMN – WEAK BEAM RATIO IN MULTI-STOREY STRUCTURES

It is expected that the engineering constructions should carry the vertical and horizontal loads during the service within the determined safety margin. Basic principal of having strong column weak beam preference is essential for earthquake resistant structures for all construction types including concrete, steel, wood and prefabricated. The major criteria for having earthquake resistant structure is to ensure that the columns are stronger and carry the most load than the beam in the nodes. This criterion has been widely adopted in earthquake codes in Europe, USA, Japan and India. It is possible to absorb and consume the earthquake energy via beam plastic joint hinges if the columns are constructed to be more durable than the beams. For this, it is foreseen that the ratio of the ultimate strength of the upper and lower columns to the right and left beams (β) should be greater than one (β = 1.2) in the beam-column joints as stated in the Turkish Earthquake Code. This coefficient is usually greater than 1.2 in the earthquake codes adopted in the world. It was observed that many structures were damaged or collapsed due to not meeting the coefficient criteria stated above. This criterion is the most effective one among many to prevent the damage in the structure under seismic action. In this study, the effect of the change in the coefficient on the column and beam moments is investigated under the Turkish Earthquake Code. Different numerical examples are presents for the coefficient of 10. The results of the investigation highlighted that irregularity in the strong column weak beam composition may negatively affect the other irregularities in the structure.

MIGRATIONS OF RELEASED SEISMIC ENERGY IN VARIOUS GEODYNAMIC CONDITIONS

The properties of slow seismic activity migration have been revealed by the space-time analysis of the total earthquake energy (LgE sum ). Our study of seismic activity covers the fragments of the Central Asian, Pacific and Alpine seismic belts: the Baikal rift system (BRS, Russia), the San Andreas fault zone (California, USA), the Christchurch fault (New Zealand), the North and East Anatolian faults (Turkey), the Philippine subduction zone, and the central fragment of the Mid-Atlantic oceanic ridge. The chains of LgE sum clusters mark the propagation of the maximum stresses front in the weaker crust areas, the zones of fault dynamic influence, and the regions of conjugated tectonic structures. The migration process is characterized by a periodicity, changes in direction, and similar modular values of the migration rates within a single fault segment (or a fault zone), which is probably related to the mechanical and rheological crust and upper mantle properties. The data analysis shows that a strong earthquake source may occur at a location wherein the front of seismic activity propagates with periodical changes in direction, and such a source can develop within a period that is multiple of the migration fluctuations, probably associated with the influence of external periodic factors. The main periods of migration fluctuations (2–4 years, and 9–13 years, in different ratios) are present in the seismic regimes of different seismic belts. The migration rate, as well as the propagation velocity of the maximum stresses front, directly depends on the velocity of movements between the plates in the region.

The mechanism of earthquake

The physical mechanism of earthquake remains a challenging issue to be clarified. Seismologists used to attribute shallow earthquake to the elastic rebound of crustal rocks. The seismic energy calculated following the elastic rebound theory and with the data of experimental results upon rocks, however, shows a large discrepancy with measurement — a fact that has been dubbed as “the heat flow paradox”. For the intermediate-focus and deep-focus earthquakes, both occurring in the region of the mantle, there is not reasonable explanation either. This paper will discuss the physical mechanism of earthquake from a new perspective, starting from the fact that both the crust and the mantle are discrete collective system of matters with slow dynamics, as well as from the basic principles of physics, especially some new concepts of condensed matter physics emerged in the recent years. (1) Stress distribution in earth’s crust: Without taking the tectonic force into account, according to the rheological principle of “everything flows”, the normal stress and transverse stress must be balanced due to the effect of gravitational pressure over a long period of time, thus no differential stress in the original crustal rocks is to be expected. The tectonic force is successively transferred and accumulated via stick-slip motions of rock blocks to squeeze the fault gouge and then exerted upon other rock blocks. The superposition of such additional lateral tectonic force and the original stress gives rise to the real-time stress in crustal rocks. The mechanical characteristics of fault gouge are different from rocks as it consists of granular matters. The elastic moduli of the fault gouges are much less than those of rocks, and they become larger with increasing pressure. This peculiarity of the fault gouge leads to a tectonic force increasing with depth in a nonlinear fashion. The distribution and variation of the tectonic stress in the crust are specified. (2) The strength of crust rocks: The gravitational pressure can initiate the elasticity–plasticity transition in crust rocks. By calculating the depth dependence of elasticity–plasticity transition and according to the actual situation analysis, the behaviors of crust rocks can be categorized in three typical zones: elastic, partially plastic and fully plastic. As the proportion of plastic portion reaches about 10% in the partially plastic zone, plastic interconnection may occur and the variation of shear strength in rocks is mainly characterized by plastic behavior. The equivalent coefficient of friction for the plastic slip is smaller by an order of magnitude, or even less than that for brittle fracture, thus the shear strength of rocks by plastic sliding is much less than that by brittle breaking. Moreover, with increasing depth a number of other factors can further reduce the shear yield strength of rocks. On the other hand, since earthquake is a large-scale damage, the rock breaking must occur along the weakest path. Therefore, the actual fracture strength of rocks in a shallow earthquake is assuredly lower than the average shear strength of rocks as generally observed. The typical distributions of the average strength and actual fracture strength in crustal rocks varying with depth are schematically illustrated. (3) The conditions for earthquake occurrence and mechanisms of earthquake: An earthquake will lead to volume expansion, and volume expansion must break through the obstacle. The condition for an earthquake to occur is as follows: the tectonic force exceeds the sum of the fracture strength of rock, the friction force of fault boundary and the resistance from obstacles. Therefore, the shallow earthquake is characterized by plastic sliding of rocks that break through the obstacles. Accordingly, four possible patterns for shallow earthquakes are put forward. Deep-focus earthquakes are believed to result from a wide-range rock flow that breaks the jam. Both shallow earthquakes and deep-focus earthquakes are the energy release caused by the slip or flow of rocks following a jamming–unjamming transition. (4) The energetics and impending precursors of earthquake: The energy of earthquake is the kinetic energy released from the jamming–unjamming transition. Calculation shows that the kinetic energy of seismic rock sliding is comparable with the total work demanded for rocks’ shear failure and overcoming of frictional resistance. There will be no heat flow paradox. Meanwhile, some valuable seismic precursors are likely to be identified by observing the accumulation of additional tectonic forces, local geological changes, as well as the effect of rock state changes, etc.

Seismic Analysis of Low and High Rise Building Frames Incorporating Metallic Yielding Dampers

There are many passive energy dissipating devices designed to dissipate earthquake energy in a structure. Metallic yielding dampers is one of these devices which are very efficient as they dissipate seismic input energy through hysteretic behavior. This research used ETABS software to analyze the performance of three metallic yielding dampers; X-shaped damper, Double X-Shaped and Comb Teeth Damper. The storey response data obtained from the analysis is storey shear. Each damper has three types of material; A992 steel, A36 steel and Aluminium. Concentrically braced steel frames with Chevron bracing were used and the dampers were placed in brace to beam orientation in each frame. The two types of frames analyzed were; low rise building with five storeys and a high rise building with twenty storeys. The site locations for both structures were in the region of California in the United States of America. The structures were analyzed by subjecting them to two earthquakes Loma Prieta and San Fernando as they were two of the major earthquakes that struck California in the nineties.

Experimental Test of Welded Wide Flange Fuses

Metallic dampers are one of the most prevalent structural components that are used to dissipate earthquake energy. A novel metallic damper, named Welded Wide Flange Fuse (WWFF), is proposed in this paper. WWFF utilizes commonly available welded wide flange sections to dissipate the earthquake energy through shear yielding of the web in the longitudinal direction, which makes the WWFF easy to be fabricated and efficient in providing high elastic stiffness and stable energy dissipation capacity. In this paper, a detailed experimental study was conducted to examine the influence on the design parameters (such as aspect ratios and slenderness ratios) on the component response (such as yielding force and elastic stiffness). The result shows that the WWFF has stable energy dissipation capacity which can be used as an efficient and robust metallic damper.

Thermal Alteration of Pyrite to Pyrrhotite During Earthquakes: New Evidence of Seismic Slip in the Rock Record

AbstractSeismic slip zones convey important information on earthquake energy dissipation and rupture processes. However, geological records of earthquakes along exhumed faults remain scarce. They can be traced with a variety of methods that establish the frictional heating of seismic slip, although each has certain assets and disadvantages. Here we describe a mineral magnetic method to identify seismic slip along with its peak temperature through examination of magnetic mineral assemblages within a fault zone in deep‐sea sediments cored from the Japan Trench—one of the seismically most active regions around Japan—during the Integrated Ocean Drilling Program Expedition 343, the Japan Trench Fast Drilling Project. Fault zone sediments and adjacent host sediments were analyzed mineral magnetically, supplemented by scanning electron microscope observations with associated energy dispersive X‐ray spectroscopy analyses. The presence of the magnetic mineral pyrrhotite appears to be restricted to three fault zones occurring at ~697, ~720, and ~801 m below sea floor in the frontal prism sediments, while it is absent in the adjacent host sediments. Elevated temperatures and coseismic hot fluids as a consequence of frictional heating during earthquake rupture induced partial reaction of preexisting pyrite to pyrrhotite. The presence of pyrrhotite in combination with pyrite‐to‐pyrrhotite reaction kinetics constrains the peak temperature to between 640 and 800°C. The integrated mineral‐magnetic, microscopic, and kinetic approach adopted here is a useful tool to identify seismic slip along faults without frictional melt and establish the associated maximum temperature.

Experimental Investigation on Seismic Behavior of Steel Truss-RC Column Hybrid Structure with Steel Diagonal Braces

This paper aims to provide an experimental support on seismic performance evaluation of the steel braced truss-RC (reinforced concrete) column hybrid structure, which could be applied as the air-cooled supporting structural system in large-capacity thermal power plants located in strong earthquake prone regions. A series of pseudo-dynamic tests (PDTs) and quasi-static tests (QSTs) were performed on a 1/8-scaled sub-structure. The dynamic characteristics, lateral deformation patterns, deterioration behavior, hysteretic behavior and failure mechanisms were investigated. Test results showed that the first vibration mode is torsion, which is caused by the small torsional stiffness of this kind of hybrid structure. The lateral deformation shape is shear mode, and the drift ratio of the structure above the corbel is significantly less than that of the column below the corbel. Earthquake energy is mainly dissipated by the RC pipe columns where cracks mainly occurred at the bottom of column and lower part of corbel. The failure mechanisms were identified indicating that the steel braces improved the global stiffness and modified the load transfer mechanism. This study affirms that the steel braced truss-RC column hybrid structure has the sufficient ductility and good energy dissipation capacity to satisfy the design requirements in high seismic regions.