Large Horizontal Displacements Research Articles

Volcanic deformation and flank instability due to magmatic sources and frictional rheology: the case of Mount Etna

SUMMARY The overall picture of Mount Etna deformation emerging since a couple of decades of geodetic surveys shows effects of magma accumulation, characterized by inflation/deflation cycle, accompanied by a sliding instability of the southeast flank, whose manifestation is an increase in the horizontal deformation away from the volcano summit. This is a very interesting case to test whether advanced models, taking into account topography, internal structure and frictional rheology, may contribute to a better understanding of the complex interplay among mechanical response, magmatic activity and gravitational load occurring in a volcanic system. Using finite element numerical models we make predictions of surface displacements associated with a simple expansion source and with a dike-like vertical discontinuity. A new methodology is developed to initialize the lithostatic stress field according to the material and geometrical complexities of the models considered. Our results show that, while an amplification of the horizontal displacement can be easily obtained up to a maximum distance of 10 km from the source, we have not been able to find any configuration to extend further this signal. For the case of Mount Etna this suggests that the large horizontal displacements observed in the east flank along the coast cannot be directly related to magma accumulation below the volcano’s summit.

Parallel Interactions at Large Horizontal Displacement in Pyridine–Pyridine and Benzene–Pyridine Dimers

A study of crystal structures from the Cambridge Structural Database (CSD) and DFT calculations reveals that parallel pyridine-pyridine and benzene-pyridine interactions at large horizontal displacements (offsets) can be important, similar to parallel benzene-benzene interactions. In the crystal structures from the CSD preferred parallel pyridine-pyridine interactions were observed at a large horizontal displacement (4.0-6.0 Å) and not at an offset of 1.5 Å with the lowest calculated energy. The calculated interaction energies for pyridine-pyridine and benzene-pyridine dimers at a large offset (4.5 Å) are about 2.2 and 2.1 kcal mol(-1), respectively. Substantial attraction at large offset values is a consequence of the balance between repulsion and dispersion. That is, dispersion at large offsets is reduced, however, repulsion is also reduced at large offsets, resulting in attractive interactions.

The Dynamic Response Analysis of Piled Wharf System under Seismic Excitation

In order to study the behavior of piled wharf system under seismic excitation, numerical analyses are conducted by employing the Newmark’s time-integration algorithm. In the computational model, both nonlinearity of subsoil and the contact behavior between pile-soil interfaces are considered. The numerical results show that the horizontal displacement extremum of all piles in time history increase with the pile height under horizontal seismic excitation. Especially, the side pile of wharf system in the bank slope appears larger horizontal displacement compared with the other piles. Furthermore, the extremum variation of horizontal acceleration and bending moment of the side pile displays a non-monotonic characteristic. Based on computational results and theoretical analyses, several conclusion remarks are drawn, which can provide valuable and referable experience to some extent for related engineering practice and design.

연직배수공법이 적용된 연약지반 상에 도로성토로 인한 측방유동의 특성

연직배수공법이 적용된 연약지반의 측방유동 특성을 조사하기 위해 우리나라 해안지역에서 계측관리가 실시된 13개 연약지반 현장의 자료를 수집하여 조사 분석을 실시하였다. 먼저 성토규모가 연약지반의 측방유동에 미치는 영향을 분석하였다. 연약층의 두께와 상대적 도로성토규모가 클수록 연약지반 속의 수평변위는 크게 발생하였다. 특히 연약지반이 두꺼우면 도로성토저면폭에 대한 연약층의 두께의 비인 상대적 성토규모도 자연 커지므로 수평변위량은 크게 발생하였다. 또한 도로성토속도가 빠르면 연약지반의 수평변위량이 크게 발생하였다. 그 밖에도 연약지반의 두께와 비배수전단강도, 지반계수 및 안정수는 연약지반의 측방유동에 영향을 미치는 중요한 요소로 나타났다. 즉 연약지반의 비배수전단강도와 지반계수가 작을수록 그리고 안정수가 클수록 연약지반의 최대수평변위량은 크게 발생하였다. 도로성토로 인하여 연약지반 속에 전단변형이 발생되지 않는 안전한 상태에서는 안정수가 3이하가 되고 지지 안전율이 1.7이상이 되었다. 그러나 연약지반 속에 전단파괴가 발생되는 불안전한 상태에서는 안정수가 5.14이상이 되고 지지안전율이 1.0이하가 되었다. 도로성토로 인하여 연약지반 속에 전단변형이 발생하는지 여부를 판단할 수 있는 허용최대수평변위량의 기준은 50mm로 정하는 것이 바람직하며 연약지반에 전단파괴가 발생됨이 없이 도로성토를 실시할 수 있는 연약지반의 수평변위량 기준은 100mm로 정하는 것이 바람직할 것이다. Field monitoring data for embankments in thirteen road construction sites at coastal area of the Korean Peninsula were analyzed to investigate the characteristics of lateral flow in soft grounds, to which vertical drain methods were applied. First of all, the effect of the embankment scale on the lateral flow was investigated. Thicker soft soils and lager relative embankment scale produced more horizontal displacements in soft grounds. Especially, if thick soft grounds were placed, the relative embankment scale, which was given by the ratio of thickness of soft ground to the bottom width of embankments, became larger and in turn large horizontal displacement was produced. And also higher filling velocity of embankments induced more horizontal displacements in soft grounds. The other major factors affecting the lateral flow in soft ground were the thickness and undrained shear strength of soft grounds, the soil modulus and the stability number. Maximum horizontal displacement was induced by less undrained shear strength and soil modulus of soft grounds. Also more stability numbers produced more maximum horizontal displacements. When the shear deformation does not develop, the stability number was less than 3.0 and the safety factor of bearing was more than 1.7. However, if the stability number was more than 5.14 and the safety factor of bearing was less than 1.0, the unstable shear failure developed in soft ground. 50mm can be recommended as a criterion of the allowable maximum horizontal displacement to prevent the shear deformation in soft ground, while 100mm can be recommended as a criterion of the allowable maximum horizontal displacement to prevent the shear failure in soft ground.

Utilization of object-oriented programming, design patterns and java for simulating earthquake-induced poundings of base-isolated buildings

Base-isolated buildings experience large horizontal relative displacements during strong earthquakes due to the excessive fl exibility that is purposely incorporated, through seismic bearings, at their bases. When the available clearance around a base-isolated building is limited, there is a possibility of the building pounding against the surrounding moat wall or adjacent structures. Considering the nonlinearities involved in this structural impact problem, it is evident that the effects of potential pounding on the overall seismic response of base-isolated buildings during earthquake excitations should be investigated numerically through appropriate simulations. Object-oriented programming (OOP), design patterns (DPs), and the Java programming language have been utilized in order to design and implement a fl exible and extendable software application that can be effectively used to perform the necessary numerical simulations and parametric studies of base-isolated buildings that may experience structural poundings during earthquake excitations. The aim of this paper is twofold: (i) to explain the signifi cant advantages of utilizing OOP, DPs, and Java in structural analysis software and (ii) to use the developed software to study earthquake-induced poundings of base-isolated buildings.

Critical load of slender elastomeric seismic isolators: An experimental perspective

One of the most important aspects of the seismic response of elastomeric isolators is their stability under large shear strains. The bearing capacity of elastomeric isolators, indeed, progressively degrades while increasing horizontal displacement. This may greatly influence the design of elastomeric isolators, especially in high seismicity regions, where slender elastomeric isolators subjected to large horizontal displacements are a common practice. In the current design approach the critical load is evaluated based on the Haringx theory, modified to account for large shear strains by approximate correction factors.In this paper the critical behavior of a pair of slender elastomeric devices is experimentally evaluated at different strain amplitudes, ranging from approximately 50% to 150%. The experimental results are then compared to the predictions of a number of semi-empirical and theoretical formulations.The main conclusion of this study is that current design approaches are overly conservative for slender elastomeric seismic isolators, since they underestimate their critical load capacity at moderate-to-large shear strain amplitudes.

Large submarine landslides in the Japan Trench: A new scenario for additional tsunami generation

We describe in detail possible large submarine landslides, several tens of kilometers in length and width, on the trench landward slope of the Japan Trench on the basis of high‐resolution topographic surveys and detailed seafloor observations. These slides stopped at the toe of the trench slope. After initial movement of the toe along a basal decollement or thrust of the trench landward slope wedge during an earthquake, the basal frictional condition(s) might change drastically from static to dynamic, thus reducing the frictional strength. As a result, rapid submarine landsliding push downward on the toe, generating large horizontal displacements for tsunamis. This hypothesis should explain suitably the relation between large displacement of the thrust fault and tsunami generation by the 2011 Tohoku earthquake as well as tsunami generation by the 1896 Tohoku earthquake.

Shaking Table Tests of the Smart Restorable Sliding Base Isolation System (SRSBIS)

This article reports on the experimental investigation of the Smart Restorable Sliding Base Isolation System (SRSBIS), proposed for the earthquake-resistant design of structures. SRSBIS is composed of steel-PTFE Flat Sliding Bearings (FSBs), supporting gravity loads while allowing large horizontal displacements, and superelastic Shape Memory Alloy (SMA) wires, providing the necessary horizontal stiffness and restoring capability. Three different configurations can be alternatively considered based on the arrangement of the SMA elements in vertical, bracing, and horizontal directions. A model scale test-structure has been set up for the system with the SMA wires arranged in vertical direction, representing the isolation units that can be practically used under each column of base-isolated buildings. A shaking table test program has been then conducted on the model structure. The experimental outcomes clearly showed that SRSBIS can be reliably used for the passive control of the seismic vibrations of buidlings and other structures.

Dynamic response control of multi-story structures by isolators with multiple plane sliding surfaces: A parametric study

Recently, a type of simple and cost effective sliding isolator, namely the uplifting sliding bearing (UPSS), had been developed for ensuring the seismic performance of multi-span continuous bridges. The objective is to control the large horizontal displacement of the conventional rubber bearings using this new sliding device which has a high potential in reducing the horizontal displacement due to the uniqueness of its geometrical configuration. The UPSS device consists of multiple sliding surfaces connected together, based on the PTFE and SUS interface; one horizontal and two inclined surfaces. This paper aims to investigate the efficiency of using the multiple-slider bearing based on the concept of UPSS to isolate multi-story shear type structures. The principles of operation and force displacement relationship for the isolator are introduced. The seismic behavior of the base isolated building by the multiple-slider bearing subjected to seismic excitation is investigated, comparing with conventional rubber bearing and pure friction slider isolating systems. Moreover, extensive parametric investigations are performed in order to achieve an optimum performance of the isolator with respect to three main properties which define the device: clearance length, the inclination angle and the friction coefficient. The results show the effectiveness of the multiple-slider bearing in minimizing the damage from earthquakes. The multiple-slider bearing proves to have a high potential in minimizing the effect of the ground displacement pulses through its operation mechanism and its unique feature that permits the use of different set of friction coefficients on each sliding surface. In addition, a principle to define the optimum value of the friction coefficient is developed.

Model Test Study on the Effect of Horizontal Load on the Vertical Bearing Capacity of Disk Pile

A group of model tests were designed to study the effect of horizontal load on the vertical bearing capacity of disk pile. Three double-disk piles were used in the test, and the distance of the two disks is 5 times as the disk diameter. Drew a horizontal load H=100N/200N/300N on the top of pile1/2/3 respectively, and put on the vertical load stage by stage, then studied the differences of three piles’ bearing properties such as changes of the pile bending moment, the horizontal and vertical deformation on the top, and soil pressure around the pile. Experiment showed that when the horizontal load is quite small, the existence of horizontal load has little to do with vertical bearing capacity. When the load reached a certain level, the p-∆ effect under the vertical load will significantly affect the vertical bearing capacity of the pile. Especially during the initial time while there is a large horizontal displacement or rotation generated by the horizontal load, the pile’s bearing capacity is controlled by the horizontal displacement.

A Practical Numerical Method for Earthquake-Induced Horizontal Displacement of Submarine Slope

Earthquake shakes the soil and induces modulus softening and liquefaction of non-cohesive soil, which causes instability of the slope. A practical numerical method is proposed for predicting large deformation and horizontal displacement of submarine gentle slope due to earthquake. The new method take normal wave loads as pseudo-static steady pressure and initial excess pore water pressure. Using 2-D nonlinear effective stress finite element method, dynamic response and liquefaction analysis are conducted with an infinite submarine slope model. Regarding the seismic motion of soil skeleton as process of softening gradually, softened soil modulus is attained during earthquake. Deformation analysis is performed with the modulus of liquefied and softened soil and the process of lateral movement is obtained. Compared with other related researches, the proposed method shows that gives reasonable results for the conditions indicated. The influences of non-liquefied surface layer, liquefied layer thickness and slope angle on horizontal displacement are studied by series of cases.

Crustal Deformation due to Atmospheric Pressure Loading in New Zealand

Crustal Deformation due to Atmospheric Pressure Loading in New ZealandWe investigate atmospheric pressure loading displacements in New Zealand using global and regional air-pressure data collected over a period of 50 years (1960-2009). The elastic response of the Earth to atmospheric loading is calculated by adopting mass loading Love numbers based on the parameters of the Preliminary Reference Earth Model (PREM). The ocean response to atmospheric loading is computed utilising a modified inverted barometer theory. The results reveal that the atmospheric loading vertical displacements are typically smallest along coastal regions, while gradually increasing inland with the maximum peak-to-peak displacement of 13.1 mm for this study period. In contrast, the largest horizontal displacements are found along coastal regions, where the maximum peak-to-peak displacement reaches 2.7 mm. The vertical displacements have a high spatial correlation, whereas the spatial correlation of the horizontal displacement components is much smaller. A spectral decomposition of the atmospheric loading time series shows that the signal is a broad band with most energy between 1 week and annual periods, and with a couple of peaks corresponding to approximately annual forcing and its overtones. The largest amplitudes in the atmospheric loading time series have an annual and semi-annual period.

Water/Aromatic Parallel Alignment Interactions. Significant Interactions at Large Horizontal Displacements

Analysis of crystal structures from the Cambridge Structural Database (CSD) and high level ab initio calculations reveals that the water/aromatic parallel alignment interactions, where the water molecule or one of its O–H bonds is parallel to the aromatic ring plane, can be significantly strong at large horizontal displacements. We found out that the strongest energies of the interactions are calculated for the water position with the large horizontal displacements, out of the aromatic ring and out of the C–H bond region. For calculated systems, normal distances were decreasing with increasing the horizontal displacement, in accord with the data found in crystal structures. The calculated energies of the interactions are significant, up to ΔECCSD(T)(limit) = −10.25 kJ/mol (at a horizontal displacement of 2.6 A), and comparable with the energy of the slipped-parallel benzene/benzene dimer. Both dispersion and electrostatic components of the interaction energy are important. The calculated interaction energ...

Transform faults and large horizontal displacements of the ocean floor

The evidence concerning the existence of transform faults and the occurrence of sea-floor spreading is reviewed and discussed. Available fault-plane solutions indicate that the direction of motion along some oceanic fracture zones is opposite to that which would be expected in case of transcurrent faults. The support for the sea-floor spreading hypothesis comes mainly from magnetic investigations. The problem, however, presents formidable dynamic and rheological aspects, and is far from being completely solved.

Numerical investigation of potential mitigation measures for poundings of seismically isolated buildings

During very strong earthquakes, seismically isolated buildings may experience large horizontal relative displacements, which may lead to poundings if an insufficiently wide clearance is provided around the building. This paper investigates, through numerical simulations, the effectiveness of using rubber bumpers, which could be attached at locations where it is likely to have impacts, in order to act as shock-absorbers. For the simulation of the dynamic behavior of such rubber bumpers during impacts, a nonlinear force-based impact model, which takes into account the finite thickness of the rubber bumpers, has been developed. Subsequently, a series of parametric analyses are performed to assess the effect of the gap size, the earthquake characteristics and the thickness, compressive capacity and damping of the bumpers. The stiffness of the moat wall is also parametrically considered during poundings of a seismically isolated building, as another potential mitigation measure for poundings of seismically isolated buildings.

Updating Thai Reference Frame to ITRF2005 Using GPS: Diversion Between ITRF2000 and 2005 in Southeast Asia

The Thai geodetic network has been regularly observed with Global Positioning System (GPS) since 1994 through several collaborative EU-ASEAN projects such as GEODYSSEA, SEAMERGES and RTSD-Delft. This geodetic network has long been served as a reference frame for Thailand. Previous realisations of the Thai coordinate reference frame were therefore tied to the global International Terrestrial Reference Frame (ITRF) at epochs 1994, 1996 and 2000. After the occurrence of the 9.2 Mw Sumatra-Andaman earthquake on the 26th December 2004, horizontal displacements were evident at different magnitudes in many surrounding countries. The geodetic network within Thailand was also significantly deformed during the earthquake at the centimetre to decimetre level. Large co-seismic horizontal displacements were observed in the southern part of Thailand, while moderate and small displacements were seen in the central and northern parts of Thailand. The Royal Thai Survey Department (RTSD) has been carrying out multiple GPS field campaigns to monitor the post-seismic displacements. This paper will analyse the GPS observations obtained from the RTSD GPS campaigns up to the end of 2008 using the Precise Point Positioning (PPP) strategy of the GIPSY-OASIS II software. It has been demonstrated that by employing the state of the art PPP technique, the users could achieve mm-level of repeatability in the horizontal components and centimetre precision in the vertical direction, for a 24-hr data span from a static site occupied by a geodetic-quality receiver. Coordinate results obtained from each campaign are then mapped to ITRF2000 and ITRF2005 using a number of well-determined global International GNSS service (IGS) sites. By comparing coordinate results between ITRF2000 and ITRF2005, it is evident that there is a significant diversion in the north component at a rate of 1.7 mm per year over Southeast Asia region. Finally, ITRF2005 coordinate results obtained from the latest RTSD GPS campaign (November 2008) will be served as a new coordinate reference frame for Thailand.

New nonlinear anti‐seismic steel device for the increasing the seismic capacity of multi‐storey reinforced concrete frames

SUMMARYIn order to increase the seismic capacity of multi‐storey planar reinforced concrete (r/c) frames, a new metal frictional device, which the capacity of a restricted rotation around the horizontal axis perpendicular to the vertical frame plane, is presented. The proposed steel device is joined to the four joints of the vertical floor span of the frame via four diagonal steel dual‐hinge bars. During the above restricted rotation, frictional forces develop, due to a suitable synthetic material that is inserted into the rotational frictional connections. When the horizontal relative floor displacement, between two floors, exceeds a desired specific value, then the proposed device locks and the diagonal steel bar becomes fully activated to tension, adding significant additional strength to the frame. This device is installed in a vertical floor span, but it is worth noting that the devices can be placed at floor spans that are not on the same vertical line. The nonlinear numerical (static/dynamic) analyses carried out in the present article, shows that the proposed devices contribute in increase of the lateral stiffness of the frame, the lateral strength of the frame in the inelastic area and the absorption of the inserted seismic energy. Furthermore, this device protects the diagonal steel bars from the buckling or from premature failure of compression. In addition, the proposed device is designed in a way that allows it to operate effectively under large horizontal relative floor displacements due to the cyclic dynamic loads, and can be used instead of the structural r/c walls. Copyright © 2010 John Wiley & Sons, Ltd.

Smart restorable sliding base isolation system

A modern base isolation system is proposed for the aseismic control of structures. It is composed of steel-Teflon Flat Sliding Bearings, to support the gravity loads while allowing large horizontal displacements, and simply connected Shape Memory Alloy (SMA) truss elements, to provide the necessary horizontal stiffness as well as a proper restoring capability. The system is referred to as Smart Restorable Sliding Base Isolation System (SRSBIS). Depending on the arrangement of the auxiliary SMA elements, SRSBIS can exhibit a geometric nonlinearity in addition to the nonlinearity of materials. In this paper, the dynamic characteristics of SRSBIS are first examined in terms of the force-displacement behavior, effective period of vibration, and equivalent damping. After that, the earthquake response of buildings equipped with SRSBIS, designed in accordance with a direct displacement-based approach, is evaluated through extensive nonlinear time-history analyses. The effects of the design parameters on the system behavior are then investigated within a comprehensive parametric study and the seismic performances of SRSBIS are finally compared to those of similar practical isolation systems. Based on the results, it is shown that SRSBIS can be suitably used for the seismic protection of structures.

Coeval extension and compression in Late Mesozoic–Recent thin-skinned extensional tectonics in central Anatolia, Turkey

The central Anatolian crust is composed of high-grade metamorphic rocks covered by Tertiary shallow marine to continental sedimentary rocks, with a Middle Miocene-Recent volcanic activity in Cappadocia. After the Late Cretaceous closure of the Tethyan Ocean and following plate collision, core complexes formed in Niğde and Kırşehir regions of central Anatolia. Recent geophysical studies indicate the presence of low seismic velocity zones beneath central Anatolia, interpreted as regionally thinned and/or hot mantle lithosphere, or asthenospheric upwelling. We present new structural data covering a ∼300 km WSW–NNE trending transect between Konya and Yozgat cities to suggest that central Anatolian Cenozoic tectonic regime is extensional and the narrow fold/thrust zones once taken as evidence of crustal convergence resulted from gravitational movements. Curie point depths map of central Anatolia shows a large-scale (diameter >140 km) upwarping (c. 15 km) of the regional crust we interpret as due to asthenospheric upwelling. These considerations suggest that (1) the central Anatolian crust deforms by extension. Transcurrent faults like the Central Anatolian Fault Zone accommodate the crustal stretching by transfer faulting; (2) post-Late Cretaceous crustal extension favored the placement of hot and low density asthenospheric material in Cappadocia by processes that may be explained by Rayleigh–Taylor instability phenomenon; (3) In central Anatolia, large post-Eocene horizontal crustal displacements (we estimate a minimum of 50 km) are not achieved by crustal contraction as previously proposed but thin-skin extensional tectonics and (4) Tethyan suture lines need to be reviewed since their traces may be modified by later extensional displacements.

Change of strain rate in Thailand after the 26 December 2004 and 28 March 2005 earthquakes using GPS measurements

During the period 1994–2004, before the Mw 9.3 Sumatra-Andaman earthquake of 26 December 2004, Thailand was moving horizontally constantly eastward with an average rate of approximately 33.2±1.1 millimeters per year in ITRF2000. The magnitude of the horizontal strain rate was less than 30 nanostrain per year, which was considered small but significant. After the occurrence of the mega thrust earthquake, a horizontal movement to the southwest direction is evident at different rates all over the Thai region. Large co-seismic horizontal displacements were observed in the southern part of Thailand, while moderate and small displacements were seen in the central and northern parts of Thailand. The Royal Thai Survey Department (RTSD) carried out multiple Global Positioning System (GPS) field campaigns to monitor the post-seismic displacements. However, their efforts were complicated by the second mega thrust (Mw8.7) earthquake, which occurred at Nias, Sumatra on 28 March 2005. This study focuses on the use of GPS data, collected between 1994 and 2006, gathered from six GPS stations located at Phuket, Chumporn, Chonburi, Uthaitani, Srisaket and Lampang in Thailand and an additional station located in the northern part of Malaysia to derive changes in the strain rate. Here we find that today’s deformation in Thailand is dominated by SW-NE trending extension. This feature is in agreement with post-seismic relaxation occurring on the Sumatran trench.