Instrumentation de barrages par accélérographes

1995 ◽  
Vol 22 (1) ◽  
pp. 150-163
Author(s):  
Georges R. Darbre
Keyword(s):  
Key Words ◽  
Dynamic Behaviour ◽  
Dynamic Properties ◽  
Free Field ◽  
Strong Motion ◽  
Gravity Dams ◽  
Arch Dams ◽  
Embankment Dams ◽  
Technical Specifications

A better understanding of the dynamic behaviour of dams requires strong-motion instrumentations. In particular, it is necessary to observe the free-field motions at the dam sites and the effective motions along the abutments, and to determine the dynamic properties of dams and their response to severe earthquakes. Instrumentation schemes are developed for arch dams, gravity dams and embankment dams, considering specific observational needs and objectives. The technical specifications to be satisfied by the accelerographs and the arrays are developed. Four arrays, which have been installed in Swiss dams ranging in height from 120 to 285 m, for a total of 29 triaxial accelerographs, are also presented. Key words: earthquakes, strong motions, instrumentation, accelerographs, dams.

Three-dimensional dynamic response analyses of Cogswell Dam

1995 ◽  
Vol 32 (3) ◽  
pp. 452-464 ◽  
Author(s):  
Ross W. Boulanger ◽  
Jonathan D. Bray ◽  
Scott M. Merry ◽  
Lelio H. Mejia
Keyword(s):  
Dynamic Response ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Strong Motion ◽  
Topographic Effects ◽  
Embankment Dams ◽  
Rockfill Materials ◽  
Wide Range ◽  
Sierra Madre

The recorded strong motions at Cogswell Dam during the 1987 Whittier Narrows and 1991 Sierra Madre earthquakes provide a valuable opportunity to evaluate the applicability of established engineering procedures for evaluating the dynamic response of dams with highly three-dimensional geometries. In addition, these records provide an opportunity to back-calculate the dynamic properties of rockfill materials, which cannot be easily measured in the laboratory or in situ. Peak transverse crest accelerations of 0.15 g and 0.42 g were recorded during the Whittier Narrows and Sierra Madre earthquakes, respectively. Combined with analyses of the trailing portions of these strong motion records, the field data cover a wide range of induced shear strains. Two-dimensional and three-dimensional dynamic response analyses were performed using established engineering procedures, and their results are compared with the recorded responses. Dam–canyon interaction and topographic effects appear to have influenced the seismic response of the dam significantly. Estimates of the in situ dynamic rockfill properties, including the modulus degradation relationship, are presented. Key words : rockfill, dynamic properties, embankment dams, earthquake response.

Soil-Structure Interaction in Buildings from Earthquake Records

1990 ◽  
Vol 6 (4) ◽  
pp. 641-655 ◽  
Author(s):  
Gregory L. Fenves ◽  
Giorgio Serino
Keyword(s):  
Soil Structure ◽  
Dynamic Properties ◽  
Strong Motion ◽  
Longitudinal Direction ◽  
Soil Structure Interaction ◽  
Base Shear ◽  
Foundation Soil ◽  
Soil System ◽  
Structure Interaction ◽  
Building Foundation

An evaluation of the response of a fourteen story reinforced concrete building to the 1 October 1987 Whittier earthquake and 4 October 1987 aftershock shows significant effects of soil-structure interaction. A mathematical model of the building-foundation-soil system provides response quantities not directly available from the records. The model is calibrated using the dynamic properties of the building as determined from the processed strong motion records. Soil-structure interaction reduces the base shear force in the longitudinal direction of the building compared with the typical assumption in which interaction is neglected. The reduction in base shear for this building and earthquake is approximately represented by proposed building code provisions for soil-structure interaction.

Seismic Response of Embankment Dams Based on Recorded Strong-Motion Data in Japan

2019 ◽  
Vol 35 (2) ◽  
pp. 955-976 ◽  
Author(s):  
DongSoon Park ◽  
Tadahiro Kishida
Keyword(s):  
Time Series ◽  
Seismic Response ◽  
Prediction Models ◽  
Strong Motion ◽  
Dynamic Responses ◽  
Design Stage ◽  
Ground Acceleration ◽  
Motion Data ◽  
Embankment Dams ◽  
Strong Motion Database

It is important to investigate strong-motion time series recorded at dams to understand their complex seismic responses. This paper develops a strong-motion database recorded at existing embankment dams and analyzes correlations between dam dynamic responses and ground-motion parameters. The Japan Commission on Large Dams database used here includes 190 recordings at the crests and foundations of 60 dams during 54 earthquakes from 1978 to 2012. Seismic amplifications and fundamental periods from recorded time series were computed and examined by correlation with shaking intensities and dam geometries. The peak ground acceleration (PGA) at the dam crest increases as the PGA at the foundation bedrock increases, but their ratio gradually decreases. The fundamental period broadly increases with the dam height and PGA at the foundation bedrock. The nonlinear dam response becomes more apparent as the PGA at the foundation bedrock becomes >0.2 g. The prediction models of these correlations are proposed for estimating the seismic response of embankment dams, which can inform the preliminary design stage.

Shear modulus reduction and damping ratio curves for earth core materials of dams

2019 ◽  
Vol 56 (1) ◽  
pp. 14-22 ◽  
Author(s):  
DongSoon Park ◽  
Tadahiro Kishida
Keyword(s):  
Shear Modulus ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Empirical Relationship ◽  
Embankment Dams ◽  
In Situ Data ◽  
Earth Core ◽  
Dynamic Analyses ◽  
Modulus Reduction ◽  
Core Materials

It is essential to obtain shear modulus reduction and damping ratio curves to perform dynamic analyses of earth-cored embankment dams. Many studies have been performed for dynamic properties of clayey soils, but they have been limited for earth core materials of dams. This study conducted resonant column tests to obtain shear modulus reduction (G/Gmax) and damping ratio (D) curves for 31 specimens (17 undisturbed and 14 remolded specimens) from 13 earth-cored embankment dams. Empirical G/Gmax and D curves are proposed for dynamic properties of clayey earth core materials. Fitting curves are provided by using the functional forms of the Ramberg–Osgood and Darendeli models. The observation shows that the undisturbed earth cores yield relatively higher G/Gmax and lower D curves than the remolded cores. G/Gmax curves of compacted earth cores are relatively higher than those of Vucetic and Dobry curves for a similar level of plasticity index. Uncertainty and bias are calculated by performing residual analysis, which shows that there is no clear bias in predicting G/Gmax and the uncertainties between undisturbed earth core materials and natural deposits are at a similar level. A proposed empirical relationship of G/Gmax and D curves for earth core materials can be utilized for dynamic analyses of embankment dams for cases where there is insufficient in situ data.

scholarly journals Numerical Modelling of Structures Adjacent to Retaining Walls Subjected to Earthquake Loading

Geosciences ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 486
Author(s):  
Xiaoyu Guan ◽  
Gopal S. P. Madabhushi
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Retaining Wall ◽  
Free Field ◽  
Retaining Walls ◽  
Earthquake Loading ◽  
Bending Moments ◽  
Sheet Pile ◽  
Novel Approach ◽  
Active Zones

In an urban environment, it is often necessary to locate structures close to existing retaining walls due to congestion in space. When such structures are in seismically active zones, the dynamic loading attracted by the retaining wall can increase. In a novel approach taken in this paper, finite element-based numerical analyses are presented for the case of a flexible, cantilever sheet pile wall with and without a structure on the backfill side. This enables a direct comparison of the influence exerted by the structure on the dynamic behaviour of the retaining wall. In this paper, the initial static bending moments and horizontal stresses prior to application of any earthquake loading are compared to Coulomb’s theory. The dynamic behaviour of the retaining wall is compared in terms of wall-top accelerations and bending moments for different earthquake loadings. The dynamic structural rotation induced by the differential settlements of the foundations is presented. The accelerations generated in the soil body are considered in three zones, i.e., the free field, the active and the passive zones. The differences caused by the presence of the structure are highlighted. Finally, the distribution of horizontal soil pressures generated by the earthquake loading behind the wall, and in front of the wall is compared to the traditional Mononobe-Okabe type analytical solutions.

scholarly journals Variations between Foundation-Level and Free-Field Earthquake Ground Motions

2000 ◽  
Vol 16 (2) ◽  
pp. 511-532 ◽  
Author(s):  
Jonathan P. Stewart
Keyword(s):  
Free Field ◽  
Low Frequency ◽  
Strong Motion ◽  
Dimensionless Frequency ◽  
Spectral Acceleration ◽  
Ground Acceleration ◽  
Attenuation Relations ◽  
Ground Motion Selection ◽  
Motion Data ◽  
Embedded Foundations

Strong motion data from sites having both an instrumented structure and free-field accelerograph are compiled to evaluate the conditions for which foundation recordings provide a reasonably unbiased estimate of free-field motion with minimal uncertainty. Variations between foundation and free-field spectral acceleration are found to correlate well with dimensionless parameters that strongly influence kinematic and inertial soil-structure interaction phenomena such as embedement ratio, dimensionless frequency (i.e., product of radial frequency and foundation radius normalized by soil shear wave velocity), and ratio of structure-to-soil stiffness. Low frequency components of spectral acceleration recorded on shallowly embedded foundations are found to provide good estimates of free-field motion. In contrast, foundation-level peak ground acceleration (both horizontal and vertical) and maximum horizontal velocity, are found to be de-amplified. Implications for ground motion selection procedures employed in attenuation relations are discussed, and specific recommendations are made as to how these procedures could be improved.

Soil-Foundation-Structure Behavior at the Oakland Outer Harbor Wharf

1996 ◽  
Vol 1546 (1) ◽  
pp. 100-111
Author(s):  
G. Norris ◽  
R. Siddharthan ◽  
Z. Zafir ◽  
S. Abdel-Ghaffar ◽  
P. Gowda
Keyword(s):  
Pile Foundation ◽  
Free Field ◽  
Strong Motion ◽  
Structural Failure ◽  
Loma Prieta ◽  
Soil Foundation ◽  
Batter Piles ◽  
Foundation Structure

The California Strong Motion Instrumentation Program's Loma Prieta records at Oakland Outer Harbor Wharf maybe used to study the free-field motions, the possible softening of soils surrounding the piles supporting the instrumented wharf, the determination of the motion on the instrumented wharf using free-field motion input and deflection-compatible lateral and vertical pile foundation stiffnesses, and conditions under which a soil-foundation interaction failure or structural failure of the batter piles might have developed.

scholarly journals Influence of ground motion duration on ductility demands of reinforced concrete structures

2019 ◽  
Vol 11 (4) ◽  
pp. 503-517 ◽  
Author(s):  
Eric De Jesus Vega ◽  
Luis A. Montejo
Keyword(s):  
Reinforced Concrete ◽  
Short Duration ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Concrete Structures ◽  
Strong Motion ◽  
Reinforced Concrete Structures ◽  
Inelastic Demand ◽  
Long Duration

Abstract This article investigates the level of influence that strong motion duration may have on the inelastic demand of reinforced concrete structures. Sets of short-duration spectrally equivalent records are generated using as target the response spectrum of an actual long-duration record. The sets of short-duration records are applied to carefully calibrated numerical models of the structures along with the target long-duration records. The input motions are applied in an incremental dynamic analysis fashion, so that the duration effect at different levels of inelastic demand can be investigated. It was found that long-duration records tend to impose larger inelastic demands. However, such influence is difficult to quantify, as it was found to depend on the dynamic properties of the structure, the strength, and stiffness degrading characteristics, the approach used to generate the numerical model and the seismic scenario (target spectrum). While for some scenarios, the dominance of the long record was evident; in other scenarios, the set of short records clearly imposed larger demands than the long record. The detrimental effect of large strong motion durations was mainly observed in relatively rigid structures and poorly detailed flexible structures. The modeling approach was found to play an important role in the perceived effect of duration, with the lumped plasticity multilinear hysteretic models suggesting that the demands from the long records can be up to twice the inferred from distributed plasticity fiber models.

scholarly journals An Interactive Tool for Automatic Predimensioning and Numerical Modeling of Arch Dams

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
D. J. Vicente ◽  
J. San Mauro ◽  
F. Salazar ◽  
C. M. Baena
Keyword(s):  
Computer Aided Design ◽  
Complex Geometry ◽  
Design Procedure ◽  
Software Tool ◽  
Gravity Dams ◽  
Detailed Model ◽  
Arch Dams ◽  
Double Curvature ◽  
Aided Design ◽  
Mass Volume

The construction of double-curvature arch dams is an attractive solution from an economic viewpoint due to the reduced volume of concrete necessary for their construction as compared to conventional gravity dams. Due to their complex geometry, many criteria have arisen for their design. However, the most widespread methods are based on recommendations of traditional technical documents without taking into account the possibilities of computer-aided design. In this paper, an innovative software tool to design FEM models of double-curvature arch dams is presented. Several capabilities are allowed: simplified geometry creation (interesting for academic purposes), preliminary geometrical design, high-detailed model construction, and stochastic calculation performance (introducing uncertainty associated with material properties and other parameters). This paper specially focuses on geometrical issues describing the functionalities of the tool and the fundamentals of the design procedure with regard to the following aspects: topography, reference cylinder, excavation depth, crown cantilever thickness and curvature, horizontal arch curvature, excavation and concrete mass volume, and additional elements such as joints or spillways. Examples of application on two Spanish dams are presented and the results obtained analyzed.

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