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Project "e-defense" Introduction of E-defense

K. Ohtani, N. Ogawa, T. Katayama and H. Shibata

Considering the lessons learnt from Hanshin-Awaji Earthquake, NIED plan to construct "E-Defense", a system which will be able to simulate the processes of the destruction of structures under real strong earthquake motions. The basic performance of "E-Defense" involves a maximum loading capacity of 1,200 tons, a maximum velocity of 200 cm/s and a maximum displacement of 2 m for horizontal excitation and a maximum velocity of 70 cm/s and a maximum displacement of 1m for vertical excitation in order to simulate destructive ground motion. The construction work of "E-Defense" began in early 2000, and will be completed at the beginning of 2005. We are conducting the construction work of the facility at Miki-city, and the manufacturing of actuators, oil-pressure supply system and other major parts of the shaking table at the MHI. "E-Defense" is one of the largest scale high performance testing facilities in the world. "E-Defense" will also be aimed for common use internationally. For the international collaboration and the dissemination of research results, the Earthquake Engineering Network ("EE-net") will also be constructed up until the completion of "E-Defense". EE-net will connect major earthquake engineering research organizations worldwide through high performance Internet links. We hope that "E-Defense" and EE-net will prove to be one of the major cooperative research organizations for earthquake disaster mitigation worldwide.

Paper 039: [Read] 

Keywords: 3-D shaking table, Failure mechanism of structures, Full scale testing, Network of Earthquake Engineering

Project "e-defense" Technical Development of Mechanical Components

T. Harada, A. Koike, M. Uchida, K. Ohtani and N. Ogawa

To realize “E-Defence (3-D Full-Scale Earthquake Testing Facility)”, we were faced with some technical developments of the hardware, such as the hydraulic actuators and the three-dimensional link.

Since the specifications of the hydraulic actuators required a rated power of 450ton, a maximum speed of 2m/sec and a stroke of +/-1m, the physical scale of the facility became very large. Therefore, the hydraulic actuators could not be designed using traditional methods. This is because of the bending effect of the piston rod due to its own weight, the lateral load and the large bearing capacity required to resist the large dynamic lateral loads. In addition, it was important to minimise the friction between the piston rod and the bearings. To solve these problems, a new bearing system and sealing system were developed.

A new bearing system was also developed for the three-dimensional link, to accommodate the wide rotation and the large capacity required.

Eight prototype actuators and three-dimensional links were manufactured, assembled and installed in the test facility to verify the newly designed systems. The verification tests were started in 1995 and successfully completed at the end of 1998.

The prototype actuators and three-dimension links are currently in position at Project “E-Defence”, which is due for completion in January 2005.

Paper 040: [Read] [Print]

Keywords: E-Defence, earthquake testing facility, hydraulic actuator, three-dimensional link

Project “e-defense”, Control System Architecture

O. Rood, K. Ohtani and E. Yoshida

Project “E-Defense” now under construction in Miki, Japan will be the world’s largest 3 Dimensional seismic simulation table when completed in 2005.  The scale of the shaking table requires 44 of the world’s largest servovalves powering 24 enormous actuators.

This paper describes the real time control architecture consisting of six separate and specialized controllers that was developed to meet the significant controller challenges of the Project “E-Defense” shaking table. Five of the real time controllers communicate through a fibre optic shared memory system. The primary controller is the 3 Dimensional (6 DOF) table controller that utilizes the latest table control methodologies. It communicates with the table through three specialized servovalve controllers located nearer the table that also collect the actuator feedbacks. The fifth controller is a specialized data output controller while the sixth controller is a totally separate data logger that records selected actuator and servovalve signals while also monitoring table operation to insure that the large scale shaking table remains stable within its operating parameters.

Paper 041: [Read] [Print]

Keywords: "Project E-Defense", Shaking Table, Control Methodology, Controller Design

A Simplified Evaluation Method for the Seismic Performance of Underground Common Utility Boxes

T. Nishioka and S. Unjoh

This paper presents a simplified evaluation method for the seismic performance of underground common utility boxes (CUBs) with rectangular cross section. Since the seismic deformation of underground structures is primarily the shear deformation in terms of the whole cross section, the proposed method is based on the shear deformation capacity. The shear deformation capacity is studied through the non-linear frame analyses of five types of standard CUBs. In the evaluation method, the seismic performance is checked by the difference between the ground strain criterion and the peak ground strain on the structure's underground level. The proposed method is applied to the CUB located at Kobe in Japan that was subjected to the 1995 Hyogoken-nanbu earthquake. The results show that the CUB has enough ductility with respect to the shear deformation, which coincides with the fact that the CUB suffered little damage from that earthquake.

Paper 055: [Read] [Print]

Keywords: simlified evaluation method, seismic performance, underground common utility boxes, ground strain criterion

Computer-aided Strengthening of Steel and Reinforced Concrete Telecommunication Poles

E. Kalkan and A. Pamuk

The absence of explicit guidelines for the rehabilitation of existing pole structures was the motivation to investigate the effectiveness of steel jacketing for the retrofitting of self-supporting steel and reinforced concrete telecommunication poles. The present study describes a numerical simulation of pre- and post-retrofitted conditions of the pole structures subjected to seismic hazards. By this way, effects of superstructure flexibility, variable damping on dynamic response, significance of flexural period on base shear amplification and overall effectiveness of retrofitting against base excitation are assessed on two reinforced concrete and two steel poles through the application of modal analyses, and by utilizing a modal superposition technique and response spectrum approach based on a set of strong motion accelerograms recorded during the 1994 Northridge earthquake. Analysis of results shows that steel jacketing has more remediation on reinforced concrete poles than steel poles for decreasing their seismic vulnerability.

Paper 052: [Read] [Print]

Keywords: telecommunication pole, finite elements, seismic retrofitting, steel jacketing, response spectrum analysis, earthquake

Lateral Dynamic Soil Stiffness for Partially Embedded Foundations in Heterogeous Soils

T.N. Nogami and M.A.S. Mahbub

The first author has recently developed the differential equation cell method to formulate the dynamic soil stiffnesses for partially embedded foundations in homogeneous soils. In this paper, this method is further extended to foundations in heterogeneous soils. The expressions for soil responses are obtained in simple closed forms, and the computation process requires iterations. The developed formulation for the lateral stiffness is demonstrated for computations of rigid foundations partially embedded in heterogeneous soils. The computations are found to generally converge with very little iteration for the cases analyzed. The developed final expression for the stiffness is simple yet produces the results very close to those computed by the much more elaborated method.

Paper 163: [Read] [Print]

Keywords: partially embedded foundation, stiffness, heterogeneous soil, frequency domain

Seismic Stability of Mt. Frederick Sidecast

C.W. Krumdieck and S.J. Woods

As a part of Solid Energy’s progressive rehabilitation of the Stockton Mine, it was determined that significant rehabilitation of the existing Mt Frederick Sidecast would be required to ensure the long-term stability of the sidecast. The site is located in an area of high seismicity with a number of known active faults. The stability of the existing sidecast is largely governed by the presence of loose unconsolidated materials within the sidecast, the presence of soft saturated and potentially liquefiable sediments that underlie the toe of the existing slope, and the potential level of ground shaking and seismically-induced deformations that may occur during future seismic events. The goal of this rehabilitation is to reshape the existing stockpile into a more stable slope configuration, and the construction of a comprehensive stormwater collection and discharge system. The reconfigured slopes will facilitate the final revegetation of the exposed surfaces and the management of surface and groundwater discharges from the area. This paper briefly describes the specific details of the project and the significance of seismic conditions on the long-term stability of the reconfigured stockpile.

Paper 117: [Read] [Print]

Keywords: seismic stability, slope stabilty, mine rehabilitation

H_infinity Direct Output Feedback Control of Structures

C-C Lin, M-C Pan and J-Y Wei

In this paper, a Hinfinity direct output feedback control algorithm, is developed to reduce the structural responses due to seismic loads. It is done through minimizing the entropy, a performance index measuring the trade-off between Hinfinity optimality and H2 optimality. The control forces are calculated directly from the multiplication of output measurements by a precalculated time-invariant feedback gain matrix. In real active control, control force execution time delay cannot be avoided. This study derives explicit formulas to calculate the maximum allowable delay time, tdmax, to assure system stability. tdmax can be increased with increasing structural original damping or by appropriately selecting control parameters. Fewer sensors and controllers and simple on-line calculations make the proposed control algorithm favorable to real implementation.

Paper 018: [Read] [Print]

Keywords: H_infinity Control, Direct Output Feedback, Time Delay, Earthquake Engineering

Hybrid Steel-concrete Connections under Reversed Cyclic Loading

B. Li, W.K. Yip and C.L. Leong

The aim of the test was to develop a preliminary guideline for the overall design and construction of precast concrete structures for lateral load resistance. Specimens were tested under reversed cyclic loading to evaluate their ductility, strength and energy dissipation capacity characteristics. Four beam-column joint with slab specimens were tested and the results are presented. MJ1 & MJ2 were monolithic specimens while their precast counterparts CJ1 & CJ2 were constructed using the proposed hybrid steel-concrete connections for a precast concrete frame. Although the structural behaviour was generally similar, a different cracking pattern was found. The results indicate that the proposed hybrid steel-concrete connections for precast concrete frame are conceptually sound but can be refined in design detailing for enhanced performance. It was found that the discontinuity in the bottom reinforcement of the precast beams caused the formation of a lower lever arm, which eventually led to a lower moment capacity of the specimens. The precast specimens however, behaved similarly to their monolithic counterparts and showed consistent hysterisis loops characteristics throughout the test

Paper 126: [Read] [Print]

Keywords: precast, beam-column joints, hybrid, strength, beam-to-column connection

Structural Uplift Induced by Near-source Earthquakes

Y. Naito and N. Chouw

The study addresses the influence of near-source earthquakes on uplift response behaviour of the main structure as well as secondary structures inside the main structure. In the investigation the soil-structure interaction is taken into account. The considered earthquakes are the 1995 Kobe earthquake and the 1999 Turkey earthquake. The result shows that uplift potential of structures does not only depend on the relationship between the characteristic of the ground excitation and the natural frequencies of the structure. It is also determined by the slenderness of the structure. An approach to reduce the uplift potential of secondary structures is also presented.

Paper 103: [Read] 

Keywords: structural uplift, near-source earthquakes, FEM-BEM, SSI, reduction approach

The Relationship between Overstrength and Members Ductility of RC Moment Resisting Frames

M. Mahmoudi

Overstrength is the strength in excess of seismic code requirements. According to the seismic codes the buildings are allowed to use overstrength to survive strong earthquake. Overstrength depends on the various factors, the most important of them is ductility. Only the ductile structures exhibit overstrength.
This paper investigates the relationship between overstrength and members ductility of various R.C. moment resisting frames having one, two, three, four, five, six, eight, ten and fifteen stories. They were loaded on the basis of the Iranian seismic code (standard no. 2800) and designed according to ACI-318 code.

This investigation was carried out using DRAIN_2DX computer program by applying the monolithically increasing horizontal loading (pushover analysis) to all frames. In each step of loading overstrength of frames and local ductility of members (beams and columns) were determined and their relationship was shown on curves.

The results indicate that the overstrength depends on members ductility considerably.

Paper 026: [Read] [Print]

Keywords: overstrength factor, members ductility factor, pushover analysis, R/C moment resisting frame

Stiffness-strain Relationship of Singapore Residual Soils

E.C. Leong, H. Rahardjo and H.K. Cheong

Residual soils are formed from the in-situ weathering of rock formations. In Singapore, residual soils occupy about two-thirds of the total land area. Cyclic triaxial tests were performed on three saturated residual soil samples from the Singapore Jurong formation. The soil samples were tested at strain levels from ± 0.005% to ± 1% for 40 loading cycles at a frequency of 0.5Hz and then sheared to failure. From the stress-strain loading curves, shear modulus and damping ratio at each strain level can be determined. The shear moduli increase slightly and the damping ratios decrease slightly with increasing number of loading cycles. The shear moduli and damping ratios reported in the literature are mainly for saturated sands and clays. The trends of the shear modulus and damping ratio with shear strain amplitude for the Jurong formation residual soils are similar to those reported in the literature. However, the stiffness-strain relationships suggested for saturated sands and clays in the literature were found to overestimate the shear moduli and damping ratios of the residual soils. A general stiffness-strain relationship was found to provide a reasonable fit to the shear modulus curve of the residual soils.

Paper 160: [Read] [Print]

Keywords: shear modulus, damping ratio, strain, cyclic, triaxial test and residual soils

In-situ Measurement of Shear Wave Velocities at Two Soft Soil Sites in Singapore

E.C. Leong, S. Anand, H.K. Cheong and T.C. Pan

In-situ measurement of shear wave velocities provides information on soil stiffness at very low strain, typically less than 10-3%. It is now widely recognised that low strain stiffness should be determined as part of the site investigation for seismic problems. However depending on the measurement method, there are some differences in the wave velocities. In-situ measurement of shear wave velocities using the down-hole technique and continuous surface wave technique were performed at two soft soil sites in Singapore. In the down-hole technique, a single borehole, a horizontally polarised surface source and a down-hole geophone were used. The continuous surface wave technique uses a continuous vibrating source placed on the ground surface. Surface waves of various frequencies from 5 to 100 Hz were generated and the waves were picked up by a series of geophones placed collinear with the source. The surface wave test measures the Rayleigh wave velocities. The down-hole tests were able to provide information to a great depth whereas the surface wave tests were only able to provide information down to a depth of about 12 m. The measured shear wave velocities found from the down-hole test and computed shear wave velocities found in the surface wave tests show differences of about ±10%. The difference is not due to the assumed Poisson’s ratio used in the computation of the shear wave velocities from the Rayleigh wave velocities alone, but is also attributed to the differences in wave source.

Paper 161: [Read] [Print]

Keywords: in-situ, shear wave, rayleigh wave, soft soil, stiffness and low strain

A Simple Method for Stochastic Dispersion of Earthquake Waves

J. Wang, A.J. Carr, N. Cooke and P.J. Moss

The analyses of the dynamic response of extended structures to asynchronous earthquake input motions need more than one input motion. The recently developed theoretical framework of conditional random field simulation of ground motion is too complex to be used by engineers. In this paper, a simple method to generate ground motions with dispersion from original seismic waves is proposed. The proposed method is based on the two assumptions that in the time domain the components of discretized space-time random field {ft1(x), ft2(x), …­, ftn(x)}, are mutually uncorrelated, and only the correlation of the predominant frequency of the earthquake is considered for the frequency dependent spatial correlation function of the ground motion field. With the aid of these assumptions, the modified Kriging method for multi-variate Gaussian random fields can be easily performed in the time domain. A description of an algorithm for the simulation of ground motions at M locations conditioned by the recorded time-histories from n locations is presented. A numerical example to generate the input ground motions for several bridge support points from one specified time-history is given and some results are presented.

Paper 051: [Read] [Print]

Keywords: conditional simulation, kriging method, dispersion, asynchronous earthquake input motions

Stationarity of Seismic Noise and Spac: Results of a New Approach

F.J. Chávez-García, M. Rodríguez and W.R. Stephenson

The SPAC method to analyse ambient noise vibration was introduced many years ago by Aki (1957). This method makes recourse to a spatial averaging (through cross-correlation functions) of microtremor measurements using an array of stations. This idea has popped up repeatedly, but no significant modifications have been contributed to the original technique. In this paper we propose a fresh look at the SPAC method, introducing the idea of exploiting temporal stationarity as a substitute for spatial averaging. This idea has several advantages from which we cite the two most important: there is no need for simultaneous recordings using an array of stations, whose locations must obey a very rigid scheme; we can obtain results for a large number of closely spaced distance intervals. Our proposal is tested using data from the Parkway, Wainuiomata, temporary array, which operated for almost two months in 1994. The results are excellent.

Paper 038: [Read] [Print]

Keywords: SPAC, Parkway, stationarity, noise

Responding to Earthquake Hazard Effects: Promoting Household Resilience and Preparedness

D. Paton, L. Smith, M. Johnston, D. Johnston and K. Ronan

Central to contemporary emergency planning is the development of individual/ household resilience to hazard effects. Drawing upon work conducted in New Zealand on risk perception and preparedness for volcanic hazards, this paper outlines a model, derived from Protection Motivation Theory and the Theory of Planned Behaviour to predict the causal relationship between certain social cognitive variables and individual preparation for natural hazard effects. Core elements in the model include outcome expectancy, risk perception, self-efficacy and action coping. The role of earthquake anxiety was also examined. From this a tentative model of individual risk reduction behaviour is proposed. Data from the members of four communities in New Zealand were collected to test the model. Structural equation modelling was used to fit the data to the model in regard to preparedness for earthquake hazards. The implications of this model for developing key performance indicators for personal resilience and for intervention planning is discussed. In regard to the latter, by linking these findings to earlier work the opportunities for developing intervention strategies by incorporating them within a community empowerment process is discussed, as is the capability of the model to operate within an all-hazards management framework.

Paper 166: [Read] [Print]

Keywords: community resilience, preparedness, public education

A Constitutive Model for Concrete Cylinder Confined by Steel Reinforcement and Carbon Fiber Sheet

Y-F Li, T-S Fang and C-C Chern

In this paper, we modify the L-L model (Li et al., 2002) and extend the application of this model to concrete cylinders confined, respectively, by steel reinforcement only, by carbon fiber reinforced plastic (CFRP) only, and by both steel reinforcement and CFRP. Thirty-six concrete cylinders with dimensions of a 30cm diameter and 60cm height were tested to verify the effectiveness of the Modified L-L model. The design parameters of the concrete cylinders include the different confinement types of the steel reinforcement (such as spiral and circular hoop) and the number of layers of CFRP. The experimental test results show that different types of steel reinforcement have a great effect on the compressive strength of concrete cylinders confined by steel reinforcement, but the different types of steel reinforcement have very little effect on concrete cylinders confined by both steel reinforcement and CFRP. Compared with the stress-strain curves of confined concrete cylinders, we can conclude that the Modified L-L model can provide more effective prediction than Kawashima models.

Paper 167: [Read] [Print]

Keywords: constitutive model, confined concrete, steel reinforcement, carbon fiber reinforced plastics

Fragility Curves for Seismically Retrofitted Concrete Bridges

S-H Kim

This study presents the development of fragility curves of the Caltrans bridges. The bridges were seismically strengthened following the 1994 Northridge earthquake by the retrofitting of steel jacketing of bridge columns and restrainers at expansion joints. Monte Carlo simulation is performed to study nonlinear dynamic responses of the bridges before and after retrofit. Fragility curves in this study are represented by lognormal distribution functions with two parameters (fragility parameters consisting of median and log-standard deviation) and developed as a function of peak ground acceleration (PGA). The sixty ground acceleration time histories for Los Angeles area developed for FEMA SAC project are used for the dynamic analysis of the bridges and a computer code is developed to calculate hysteretic parameters of bridge columns before and after steel jacketing. The effect of retrofit is expressed in terms of the increase of the median value of the fragility curve for retrofitted bridge from that of the bridge before retrofit. The comparison of fragility curves of the bridges before and after column retrofit demonstrates that the improvement of the bridges with steel jacketing on the seismic performance is excellent for the damage states defined in this study.

Paper 168: [Read] [Print]

Keywords: Fragility Curves, Concrete Bridges, Retrofit, Steel Jacketing

Artificial Neural Network (ANN) Modeling for Earthqauke Damage Detection in Water Distribution System

S. Takada, N. Hassani and R. Rasti

The artificial neural networks (ANN) as a non-parametric system identification approach present a robust and efficient way to simulate the nonlinear behavior of engineering systems. In this paper an artificial neural network, a general back error propagating perceptron, is used to detect damage in pipelines in water distribution systems which are involved in earthquakes. Since the pipes are buried underground, it is possible that their damage may not be found, even through extensive excavation.  The failure point or points were obtained by using the amount of water discharge from the tanks. The states of probable failures then have to be computed. The amount of output discharge from the tanks is obtained by direct analysis for different states of pipe failure. Through a parametric study, different geometries, shapes, diameters and pressures of the water network are surveyed and the best network architecture for each case is obtained. The peak responses and phase delays are assumed to be the network outputs. Another feature is that the network can be operated in a supervised manner. The study shows the efficiency and capability of the ANN to model the observed nonlinear behavior.

Paper 169: [Read] [Print]

Keywords: artificial neural network, back error propagation, water distribution system, back analysis

Estimation of Shear Strength of Reinforced Concrete Interior Beam-column Joints by using Database of Experimental Results

T. Kusakari and O. Joh

Effective factors on shear resistance of R/C interior beam-column joints were analyzed using experimental data including 303 specimens tested in Japan and abroad from 1971 to 2000.  These specimens could be classified into four types of failure mode: 1)shear failure in joints without beam or column yielding (J-type), 2)shear failure after beam or column yielding (BJ and BJf-type), 3) flexural failure in beam ends without joints failure (B-type), 4) flexural failure in column ends without joints failure (C-type). The number of specimens in the four failure types is 55, 180, 64, 4, respectively. A reliable equation to evaluate the joint shear strength was proposed using the regression analysis of the shear strength and three factors: concrete strength, column axial stress and bond index which was consisted of joint reinforcement and beam bar bond stress in the joint. The failure modes in joint shear and in beam/column flexure can be easily distinguished by this equation.

Paper 036: [Read] [Print]

Keywords: reinforced concrete, beam-column joint, strength, shear resistance mechanisms

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