Top PDF Earthquake-Induced Soil Pressures on Structures

Earthquake-Induced Soil Pressures on Structures

Earthquake-Induced Soil Pressures on Structures

45 • • • 53 Force and moment on smooth rigid wall for one-g static horizontal body force 54 2.7 Finite element mesh for static solutions 57 2.8 Pressure distributions on rigid wall for o[r]

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Seismic earth pressures on reinforced soil retaining walls

Seismic earth pressures on reinforced soil retaining walls

Civil engineering constructions play a very important role in our life. Especially in the case of public concerned civil engineering constructions, it is very important to proper designing. Because in case of any failure of these structures may lead to great devastation. Soil retaining structure (ex. bridge abutment, anchored bulkhead, mechanically stabilized wall) is one of the public concerned structures. They are frequently used for various infrastructure projects like high way, bridges, port harbor transportation system, and at other civil engineering constructions. There are various types of retaining structures are in practice for different applications. Over the time, the classical gravity retaining walls transitioned into reinforced concrete cantilever walls, with or without buttresses and counter forts. These were then followed by a variety of crib and bin-type walls. All these walls are externally stabilized walls or conventional gravity retaining walls. Earthquake may cause negligible to severe deformation which may cause failure of these structures. For proper design of the structure we should also consider the seismic aspects.
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Some important considerations in analysis of earthquake-induced landslides

Some important considerations in analysis of earthquake-induced landslides

Similar to the MDR, the effect of multidirectional shaking on the excess pore pressure is expressed in terms of the multidirectional pore pressure ratio (MPR), which is the percent increase in the magnitude of pore pressure developed under multidirectional shaking over that of one-directional shaking at a given depth. Figure 12 presents the average value of MPR for the four ground motions investigated for the 20 m and 100 m soil profiles with slope angles of 0, 5, and 10 degrees. The 100 m deep soil profile shows that multidirec- tional shaking causes a 30 % increase in pore pressure generation near the bottom of the profile, which re- duces to 0 % at around a depth of 10 m before increas- ing again to 10 % near the surface. These results are similar to those found by Su and Li (2003). The excess pore pressures generated at depth by multidirectional shaking could propagate to the surface and cause fail- ure long after earthquake shaking has stopped. The slope angle appears to have a negligible effect on ex- cess pore pressure generation. For the 20 m soil pro- file, the MPR value varies from 20 % to 40 % over all depths. Based on these results, unidirectional site response analyses could give unconservative results.
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Earthquake hazard and damage on traditional rural structures in Turkey

Earthquake hazard and damage on traditional rural structures in Turkey

With just a few exceptions all the different rural structural types used a timber joist system of varying degrees of complexity to support the soil roof covering. The load carrying timber most widely used in the roof was Kavak- Poplar (Figure 17). In some stone and earthen (kerpic) structures, wooden roof beams are supported by vertical wooden logs. In all but the newest of structures beams and columns were round or sub-round in section. This column logs can be placed within the wall or out of the walls but in the rooms (Figure 18). The connections of column logs with roof beams are not adequate. The beams were supported on columns which were flat topped or in a few cases hollowed out to form a saddle bearing surface. In no cases were rigid fixing mechanisms between columns and beams observed. The trunks are generally without its bark. This made connections and good bearing surfaces between them virtually impossible, for example, where two horizontal beams cross at right angles and one of them simply rests upon the other. Round sectional beams were prone to roll off the other during the earthquake induced motions. Also, the round beam-ends point loaded (to an excessive degree) the supporting walls beneath (Hughes, 2000). Also there is no diagonal bracing exist. The lateral drift of the frame is limited if there exist masonry wall in between frame bays. If the column logs are located out of the wall, as shown in Figure 18-b, lateral rigidity of the frame is low.
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Evaluation of Seismic Induced Wall Pressures for Deeply Embedded NPP Structures

Evaluation of Seismic Induced Wall Pressures for Deeply Embedded NPP Structures

The stiffness characteristics of the internal equipment are not included in the model. However, the mass of the equipment is lumped with the mass of the cylindrical shell; the combined weight is 92,202 kN. The weights of the basemat and roof are 40,474 kN and 4,450 kN, respectively. The weights have been reduced to some extent from the actual weights to obtain structural frequencies that are likely to be interactive with the SSI frequencies. In the detailed finite element models developed using the SASSI 2000 program, the portion of the structure below the ground surface is modeled with explicit finite elements (e.g., 3-D bricks and shells), while the superstructure above the ground surface is represented with simple lumped masses and 3-D beams. The models are developed for the four different embedment conditions, ranging from shallow embedment to full burial. A typical SASSI DEB model is shown in Fig. 1. As shown in this figure, the basemat is modeled with brick elements and the sidewalls and internals are modeled with shell elements. The base of the superstructure is connected to the sidewalls by rigid links to simulate the rigid diaphragm of the floor expected to exist at grade level. Two layers of solid soil elements are placed radially outside the structure so that soil pressures may be evaluated.
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Dimensional analysis of the earthquake-induced pounding between inelastic structures

Dimensional analysis of the earthquake-induced pounding between inelastic structures

The impact of many SDOF oscillators in a row has been studied by Anagnostopoulos [6] and Athanassiadou et al. [13] with emphasis on buildings, and by Jankowski et al. [14] with emphasis on multi-span bridges. Further studies on the impact of bridge segments have been presented by DesRoches & Muthukumar [15] who examined the impact response of elastic and inelastic oscillators including the event of adjacent structures restrained with cables. That study concludes that among the dominant parameters which govern the pounding response are the stiffness ratio of the neighboring oscillators together with the ratio of the natural period of one of the oscillators and the dominant period of the excitation. A further conclusion of the DesRoches & Muthukumar [15] work is that when the natural frequency and the excitation frequency are separated the one-sided impact is accentuated, whereas, impact suppresses the response of the oscillators at resonance. At about the same time an analogous study was conducted in Japan by Ruangrassame & Kawashima [16] who proposed the so-called ‘relative displacement response spectrum with pounding effect’. Contrary to the work of DesRoches & Muthukumar the work of Ruangrassame & Kawashima concluded that in addition to the stiffness ratio and the period ratio, the mass ratio of the two oscillators governs appreciably the response.
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A Survey On soil capable on bearing the load structures

A Survey On soil capable on bearing the load structures

Soil tainting is made out of either strong or fluid unsafe substances blended with the normally happening soil. More often than not, contaminants in the dirt are physically or synthetically joined to soil particles, or in the event that they are not appended, are caught in the little spaces between soil particles. The worry over soil sullying stems basically from wellbeing dangers, from coordinate contact with the tainted soil, vapors from the contaminants, and from auxiliary tainting of water supplies inside and hidden the soil. Soil defilement is caused by the nearness of anthropogenic (human-made) chemicals or other change in the regular soil condition. This kind of defilement ordinarily emerges from the break of underground stockpiling tanks, utilization of pesticides, and permeation of defiled surface water to subsurface strata, oil what's more, fuel dumping, draining of squanders from landfills, or direct release of mechanical squanders to the dirt. The most widely recognized chemicals included are oil hydrocarbons, solvents, pesticides, lead, and other substantial metals. This event of this wonder is associated with the level of industrialization and forces of compound use. Soil-squander cooperation influences all
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Effect of Earthquake Load on Column Forces  in Concrete Frame Structures with Different Type of  RC Shear Walls  under  Different  Type  of  Soil Condition

Effect of Earthquake Load on Column Forces in Concrete Frame Structures with Different Type of RC Shear Walls under Different Type of Soil Condition

The seismic weight of building is the sum of seismic weight of all the floors. The seismic weight of each floor is its full dead load plus appropriate amount of imposed load, the latter being that part of the imposed loads that may reasonably be expected to be attached to the structure at the time of earthquake shaking. It includes the weight of permanent and movable partitions, permanent equipment, a part of the live load, etc. While computing the seismic weight of columns and walls in any storey shall be equally distributed to the floors above and below the storey. Earthquake forces experienced by a building result from ground motions (accelerations) which are also fluctuating or dynamic in nature, in fact they reverse direction some what chaotically. The magnitude of an earthquake force depends on the magnitude of an earthquake, distance from the earthquake source(epicenter), local ground conditions that may amplify ground shaking (or dampen it), the weight(or mass) of the structure, and the type of structural system and its ability to with stand abusive cyclic loading. In theory and practice, the lateral force that a building experiences from an earthquake increases in direct proportion with the acceleration of ground motion at the building site and the mass of the building (i.e., a doubling in ground motion acceleration or building mass will double the load).This theory rests on the simplicity and validity of Newton’s law of physics: F = m x a, where ‘F’ represents force, ‘m’ represents mass or weight, and ‘a’ represents acceleration. For example, as a car accelerates forward, a force is imparted to the driver through the seat to push him forward with the car(this force is equivalent to the weight of the driver multiplied by the acceleration or rate of change in speed of the car). As the brake is applied, the car is decelerated and a force is imparted to the driver by the seat-belt to push him back toward the seat.Similarly, as the ground accelerates back and forth during an earthquake it imparts back-and-forth(cyclic) forces to a building through its foundation which is forced to move with the ground. One can imagine a very light structure such as fabric tent that will be undamaged in almost any earthquake but it will not survive high wind. The reason is the low mass (weight) of the tent. Therefore, residential buildings generally perform reasonably well in earthquakes but are more vulnerable in high-wind load prone areas. Regardless, the proper amount of bracing is required in both cases.
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Effect of Earthquake Load on Column Forces  in Concrete Frame Structures with Different Type of  RC Shear Walls  under  Different  type  of  Soil Condition

Effect of Earthquake Load on Column Forces in Concrete Frame Structures with Different Type of RC Shear Walls under Different type of Soil Condition

According to IS-1893(Part-l): 2002, high rise and irregular buildings must be analyzed by response spectrum method using design spectra shown in Figure 4.1. There are significant computational advantages using response spectra method of seismic analysis for prediction of displacements and member forces in structural systems. The method involves only the calculation of the maximum values of the displacements and member forces in each mode using smooth spectra that are the average of several earthquake motions. Sufficient modes to capture such that at least 90% of the participating mass of the building (in each of two orthogonal principle horizontal directions) have to be considered for the analysis. The analysis is performed to determine the base shear for each mode using given building characteristics and ground motion spectra. And then the storey forces, accelerations, and displacements are calculated for each mode, and are combined statistically using the SRSS combination. However, in this method, the design base shear (V B ) shall be compared with a base shear
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An efficient order reduction strategy in earthquake nonlinear response analysis of structures

An efficient order reduction strategy in earthquake nonlinear response analysis of structures

imum speed up factor of about 2 compared to the Newmark algorithm is achieved. However, it has to be added that for this type of nonlinearity, the Newmark integration scheme appears to have a relative slow convergence rate. As a consequence, the computational time by applying the Newmark method can exceed to a period of time, which is comparable if the full central difference integration scheme is applied or even to infinite period of time, if there is no conver- gence. Following, the new integration strategy gains the benefit of both of the two algorithms, i.e. central difference and Newmark, which is stability without requiring iteration algorithms. The red dashed line in Figure 9 (response to the Bam excitation) shows the response obtained by the new POD strategy, which approximates the full Newmark response accurately. This is not surprising as the snapshots are taken in equidistant time intervals spread over this whole response history. The derived POD transformation matrix, which is the set of POD modes, is now applied to reduce the order of the set of equations for the structure excited by the rest of the presented earthquake events presented in Table 1. It means that the time integration in the full (physical) space no longer has to be performed. As for the next transformations into the POD space only one transformation matrix is applied. This strategy is here called universal POD method. Now this approach unveils its similarities to the method of modal truncation, which is mainly applicable to linear systems. Figures 11, 12, 13, 14 and 15 compare the displacement responses applying the new MOR strategy and the Newmark scheme.
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Shaking table tests on strengthening of masonry structures against earthquake hazard

Shaking table tests on strengthening of masonry structures against earthquake hazard

Structures located in the seismically active zones are far from possessing qualities that would ensure satisfactory seis- mic performance (Ozcebe et al., 2003). Developing countries commonly have poor and under educated population living in self-constructed masonry houses, which are at high risk if they are located on seismically active regions. The be- havior of the masonry buildings during the earthquakes is poorly understood and appropriate tools to analyse them are now urgently required. On the other hand, numerical mod- eling of the seismic behavior of masonry structures repre- sents a very complex problem due to the constitutive char- acteristics of the structural material and its highly physical and geometrical nonlinear behavior when subjected to strong ground motion (Bayraktar et al., 2007). The structural vul- nerability and damage-failure patterns of unreinforced ma- sonry (URM) were studied by many researchers (Korkmaz, 2010; Bruneau, 1994; Tornabvie, 1997; Benedetti et al., 1998; Abrams, 2001; Paquette and Bruneau, 2003; Doherty et al., 2002). Of the methods considered, injection grouting, insertation of reinforcing steel, prestressing, jacketing, use of FRP and various surface treatments were the most common (Albert et al., 2001). The difficulties in performing advanced testing of this type of structures are quite large due to the in- numerable variations of masonry, the large scatter of in situ material properties and the impossibility of reproducing it all in a specimen (Zucchini and Lourenco, 2004).
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Approximate Dynamic Analysis of Structures for Earthquake Loading Using FWT

Approximate Dynamic Analysis of Structures for Earthquake Loading Using FWT

Two examples are analysed for the El Centro Earthquake record (S-E 1940). The Haar wavelet is used for the FWT. The number of points of the El Centro is 2688, and the time interval is 0.02 seconds. The exact response of structure is calculated by the Newmark beta method. A personal computer Pentium 4 is used and the computing time is calculated by clock time. The analysis is carried out by the following methods:

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Off-Axis Underground Soil Pressures from Surface Impact Loads

Off-Axis Underground Soil Pressures from Surface Impact Loads

superposed wave types, the relative contributions of which are unknown. In addition to the general unavailability of appropriate solutions for direct comparison and benchmarking of the present result, other factors limit such comparisons. These factors include the necessity to incorporate horizontal restraints on the z-axis boundary when using the axisymmetric modeling technique. The on-axis location, which is where the benchmarking is performed, will have the least reliable responses, due to the spurious effects produced, locally, by this boundary condition. Another factor, is the desirability, for this investigation, to realistically consider the missile as a rigid impacting element, imposing the applied load by displacing a rigid massless disc at the surface (rather than applying a true, uniformly distributed load) as was done in the cited references. These two methods for application of the impulse load show marked time history response differences within 3 or 4 diameters of the loading footprint. The comparison in Figure 4(a) shows good agreement between the analytical and finite element soil responses at the surface. From Figure 4(b), and other similar comparison plots not shown, it can be concluded that the on-axis stress responses correlate reasonably well at distance from the applied loading. However, due the availability of alternative approximate formula for the on-axis subsurface response to impact [Mayne and Jones (1983)], and the uncertainty of the depth at which the finite element solution has acceptable accuracy, it is recommended that the finite element results of Figure 6 for φ = 0 not be used in design.
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Life Cycle Evaluation Of Rehabilitation Of Residential Structures, Subjected to Earthquake

Life Cycle Evaluation Of Rehabilitation Of Residential Structures, Subjected to Earthquake

Residential Structures, subjected to earthquake." The rehabilitation of any structure is essential, when the potential strength, as on the date, of the structural element or the global strength, found less than the designed, thereby reducing the factor of safety provided. The reduction in factor of safety alarms the danger signal during the event of crises especially like earthquake. The ageing of the material / s of the building components, environmental effects on the materials, repeated excessive or the change in the pattern of stresses reduces the potential strength. The change of use causing undesired change in nature and or of quantity of loading, change made in seismic zone, by the national authority, are the other factors also contribute in reduction of potential strength of the building. The estimation of potential strength is thus a cyclic process and in turns the process of rehabilitation. The evaluation of strength, of rehabilitated building, is the process contributed by the materials used, the methodology adapted, the workmanship, and the required rehabilitated strength. In this paper focus, and emphases, placed on explaining efficient, economical, eco-friendly and optimistic use these factors. Devastative earthquake that rock the Gujarat region in 2001, selected to collect the information about the current scenario, in respect of above referred factors and the awareness level among the affected citizens. The information collected from technical professionals, the implementers, and the end users, by method of personal interviews, and analyzed by using IBMSPSS software. Three case studies conducted, the first one explains the advantage of retrofitted building in the form of higher safety level for users, and extended longevity of the serviceable life of the building. Further, maintaining lower level of carbon emission, and ratable value for the tax calculation of the building. The second case study of survey in Gujarat for assessment, of current intensity level of implementation of the changes made in Buy laws, rules, and regulations and in specific acceptance and awareness in the construction industry and end users. The awareness level about the safety of occupants and the building is rising and has come to forth as against in the past. The third case study reveals how the decision-making governed by the influence of
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Inelastic earthquake response and design of multistorey torsionally unbalanced structures

Inelastic earthquake response and design of multistorey torsionally unbalanced structures

The response values of model 6B30 are the highest when the UBC static torsional provisions are adopted due to the low total strength of the model when designed according to the st[r]

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Earthquake-induced disasters: limiting the damage

Earthquake-induced disasters: limiting the damage

While it is impossible to prevent an earthquake, it is possible to prepare for one, as well as to take mea- sures to safeguard both populations and property against potential damage, death and destruction. With this in mind, NATO member and partner countries have together taken a number of concrete steps in this direction, ranging from civil emergency planning to research and development in the field of earthquake sciences. Initiating programmes to help reduce the effects of earthquakes in addition to pro- viding assistance after an earthquake contribute to maintaining security and stability in what is a poten- tially perilous environment.
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The Influence of Earthquake Magnitude on Hazard Related to Induced Seismicity

The Influence of Earthquake Magnitude on Hazard Related to Induced Seismicity

‘ interest ’ have focussed on those easily recordable on national networks (e.g., M ≳ 3) or teleseismic networks (e.g., M ≳ 5). This then corresponds to where magnitude scales tend to be broadly consistent (i.e., M ≳ 3–5). In terms of moni- toring induced seismicity, and the estimation of seismic hazard based on these observations, we must therefore fully consider not only the influence of measured earthquake magnitude, but also the magnitude scale itself.

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Fine Root Mortality Increased by Earthquake Induced Landslides

Fine Root Mortality Increased by Earthquake Induced Landslides

This study determined the effects of earthquake induced landslide on fine root mortality. It is useful to understand underground soil process after earthquake. We established 9 plots at each of non-moved and landslide site in Cupressus funebris and Cryptomeria fortunei forest stands near the fault belt of the Wenchuan Earthquake. Fine roots were sampled at 0 - 10 and 10 - 15 cm soil layer using aluminum cylinders (100 cm 3 ). We found that earthquake induced landslide signifi-

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Changes in groundwater levels or pressures associated with the 2004 earthquake off the west coast of northern Sumatra (M9 0)

Changes in groundwater levels or pressures associated with the 2004 earthquake off the west coast of northern Sumatra (M9 0)

The changes in groundwater levels or pressures with the Sumatra earthquake were observed at 38 of the 45 observa- tion stations and 52 of the 62 observation wells. A major part of the changes in groundwater levels or pressures were dynamic oscillations due to the seismic wave. At YSK, the maximum amplitude of the oscillation in groundwater pres- sure was 0.05 MPa, equivalent to the groundwater level of 5 meters (Fig. 2). Short-period oscillation of groundwater pressure was more clearly detected than that of groundwa- ter level. In the case of an open well, the change in ground- water level needs a groundwater flow between an aquifer and well. Therefore, it is difficult for the groundwater level in an open well to reflect the short-period oscillation in the pore pressure of an aquifer. The effect is called the wellbore storage effect. Therefore, the wellbore storage effect affects
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Mathematical modelling of earthquake induced vibrations on multistory buildings

Mathematical modelling of earthquake induced vibrations on multistory buildings

Logically, the taller building will be collapsed with a small period. We will give the reason in mathematical ways according to our study. The ability to make predictions about the vibrations from the earthquake could enable scientist to evaluate or plans and may have a significant effect on the period of time for the building collapsed. The modelling of unforced and forced vibrations on multistory buildings are used as a tool to study the mechanisms of vibration that caused by an earthquake. Both models are used to calculate the natural frequencies, w and period, P of the building vibrations. Furthermore, the maximal amplitude of the building vibrations also can be analysed. For this research, eight, eleven and fifteen floors building have been applied. In our analysis, eigenvalues method is used via Maple 13 package. The graph of forced frequency versus amplitude and period versus maximal amplitude are plotted and discussed.
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