Genie Civil

Analytical expressions for the determination of hydro-seismic forces acting on a rigid dam with irregular upstream face geometry in presence of a compressible viscous fluid are derived through a linear combination of the natural modes of water in the reservoir based on a boundary method making use of complete sets of complex T-functions. The formulas obtained for distributions of both shear forces and overturning moments are simple, computationally effective and useful for the preliminary design of dams. They show clearly the separate and combined effects of compressibility and viscosity of water. They also have the advantage of being able to cover a wide range of excitation frequencies even beyond the cutoff frequencies of the natural modes of the reservoir. Key results obtained using the proposed analytical expressions of the hydrodynamic forces are validated using numerical and experimental solutions published for some particular cases available in the specialized literature.

Analytical expressions for the determination of hydro-seismic forces acting on a rigid dam with irregular upstream face geometry in presence of a compressible viscous fluid are derived through a linear combination of the natural modes of water in the reservoir based on a boundary method making use of complete sets of complex T-functions. The formulas obtained for distributions of both shear forces and overturning moments are simple, computationally effective and useful for the preliminary design of dams. They show clearly the separate and combined effects of compressibility and viscosity of water. They also have the advantage of being able to cover a wide range of excitation frequencies even beyond the cutoff frequencies of the natural modes of the reservoir. Key results obtained using the proposed analytical expressions of the hydrodynamic forces are validated using numerical and experimental solutions published for some particular cases available in the specialized literature.

Analytical expressions for the determination of hydro-seismic forces acting on a rigid dam with irregular upstream face geometry in presence of a compressible viscous fluid are derived through a linear combination of the natural modes of water in the reservoir based on a boundary method making use of complete sets of complex T-functions. The formulas obtained for distributions of both shear forces and overturning moments are simple, computationally effective and useful for the preliminary design of dams. They show clearly the separate and combined effects of compressibility and viscosity of water. They also have the advantage of being able to cover a wide range of excitation frequencies even beyond the cutoff frequencies of the natural modes of the reservoir. Key results obtained using the proposed analytical expressions of the hydrodynamic forces are validated using numerical and experimental solutions published for some particular cases available in the specialized literature.

Une analyse automatique du comportement des structures hyperstatiques compte tenu des déformations élastiques du support (sol élastique ou appuis élastiques) par la méthode matricielle des raideurs est présentée. Une méthode d'analyse globale d'interaction statique sol-structure est utilisée en utilisant le modèle de Winkler comme modèle physique représentatif du support élastique. la validité des résultats d'analyse sont confrontés aux résultats des méthodes analytiques de Hetenyi et Simvoulidi.

Proper characterisation of the mechanical properties of unbound granular materials (UGM) is an essential issue in the analysis and design of flexible pavements. In particular, the resilient modulus of aggregates is a key input parameter in UGM characterization and prediction of pavement structural performance. In the present work, three UGM constitutive models are implemented within an axi-symmetric finite element code developed to simulate the nonlinear behaviour of pavement structures including two local aggregates of different mineralogical nature, typically used in Algerian pavements. The performance of these mechanical models is examined with regards to their capability of representing adequately, under various conditions, the granular material non-linearity in pavement analysis. In addition, deflection data collected by falling weight deflectometer (FWD) are incorporated into the analysis in order to assess the sensitivity of critical pavement design criteria and pavement design life to the three constitutive models. Finally, conclusions of engineering significance are formulated.

This paper describes the main results of an experimental program that was carried out to assess the mechanical properties of two local aggregates for construction purposes in road pavement. The scope of the experimental study consisted of three main stages: (1) to evaluate engineering characteristics in accordance with empirical classification and relevant tests standards, (2) to evaluate the resilient deformations characteristics of the local aggregates under cyclic loading and to assess the effect of non-linear stress dependency on their resilient behaviour for road pavement design, and (3) to determine from repeated load triaxial (RLT) tests, the parameters of a constitutive model to be used at a later stage in non-linear finite element analysis of flexible pavement structures. It is found, in accordance with empirical ranking, that the local aggregates of basaltic origin exhibit better impact and abrasion resistance than the local limestone aggregates. However, from the RLT tests results and values of the model parameters, it is clearly shown that limestone aggregates exhibit higher stiffness than aggregates of basaltic origin, contrary to the results issued from empirical ranking tests. In addition, the effects of geological origin, density and moisture content on the resilient behaviour of the studied aggregates are also investigated.

A data windowing approach is developed to estimate the evolutionary power spectra of strong motion earthquakes. The main properties and the engineering significance of the evolutionary power spectrum of seismic accelerations are first presented. Specific guidelines for optimal windowing to be used in time dependent spectrum analyses of transient signals are then formulated. Based on these guidelines, three moving data window functions and their characteristics are examined with the perspective of studying their effects on both the spectral resolution and the stability of spectral estimates of earthquake strong ground motions. Specific parameter values for which particular data window functions are more suitable to be used in order to obtain reliable estimates of the evolutionary spectral amplitudes are discussed.

The problem of seismic soil amplification is of particular importance in relation to the assessment of local soil condition effects on seismic motions characteristics in soil deposits. Most of the practical studies have been limited to 1-D amplification of vertically propagating SH-waves considering essentially the problem in the frequency domain. In this paper, the approach is extended to an investigation of the effects of incident angles on 2-D amplification of obliquely propagating shear waves based on a discrete–time wave propagation formulation. Simple analytical models of seismic site amplification with respect to bedrock for obliquely propagating shear waves in both elastic and viscoelastic soil deposits overlying bedrock are derived. Emphasis is placed on the significance of incidence angle effects on seismic site amplification, considering different values of rock – soil impedance ratios. Sensitivity analyses are performed utilizing the soil profile model of the site of El–...

This paper summarises the preliminary results of an investigation aimed at identifying the effects of ground motion phase content modelling of both earthquake ground acceleration simulation and non linear structural response. The influence of these effects is analysed by applying three phase simulation techniques to two earthquake ground motion models characterised by time invariant and time varying frequency contents. Time histories of typical quantities of interest such as artificial accelerations, intensity envelopes, input cumulative energy functions, instantaneous ground motion frequencies, non-linear displacement response and instantaneous stiffness degradation, have been examined. Moreover, a moving resonance based validation procedure that allows to select the most appropriate earthquake ground motion model to be used in order to obtain reliable time history earthquake response of non linear structures is proposed.

Seismic design of common engineering structures is based on the assumption that excitations at all support points are uniform or fully coherent. However, in lifeline structures with dimensions of the order of wavelengths of incident seismic waves, spatial variation of seismic ground motions caused by incoherence effects and stochasticity in the characteristics of the surface layers may introduce significant additional forces in their structural elements. The main objective of this paper is to provide estimates of coherency functions of spatially variable ground motion at the free surface of a layered stochastic soil sites in the epicentral region of the El-Asnam Earthquake in Algeria. Lagged coherency functions at bedrock have been estimated in [1] by simulating ground motion field (around Sogedia Factory) corresponding to the 1980 El-Asnam Earthquake. Considering randomness in the thickness of soil layers overlying the bedrock in the study area, an analytical approach proposed by Z...

Studies of non linear structural response subjected to earthquake accelerograms have contributed significantly to the improvement of our understanding of the degradation process of structures during strong motion earthquakes. The knowledge of this degradation process can be used with efficiency in order to assess the time history response and the aseismic design of critical structures such as dams, nuclear power plants and other important facilities. The objective of this study is to identify the effects of the frequency nonstationarity, on the nonlinear structural response, by using a nonstationary stochastic model based on the concept of physical spectrum and simple inelastic structural models.The nonstationary stochastic model is used to simulate, two sets of artificial earthquakes compatible with a real ground acceleration record and exhibiting similar phases distribution [6] and different frequency contents. The first group presents a time varying frequency content and the seco...

The main objective of this paper is to provide estimates of coherency functions of strong ground motion at engineering bedrock within the El-Asnam region (North-West Algeria). Due to lack of recorded array data, the so-called Empirical Green’s Function (EGF) method is used to simulate ground acceleration at different points in the engineering bedrock of the study area. The event being simulated is the 10 October 1980, Ms 7.2 El-Asnam Earthquake. Ground motion recorded at the Sogedia factory station during the 8 November 1980 aftershock with local magnitude 5.6 was used as empirical Green’s function. Lagged coherency functions estimated from simulated motions indicate significant loss of coherence with increasing frequency and separation distance. Since the EGF method, when used with Green’s function at a single station, can primarily model source effects, which are interpreted as the main reason behind the observed loss of coherency. The results also indicate that source effects are...

The present paper deals with the structural design optimization of reinforced concrete rectangular sections under ultimate design loads. An analytical approach of the problem, based on a minimum cost design criterion and a reduced number of design variables, is developed. It is shown, among other things, that the problem formulation can be cast into a non linear mathematical programming format. A typical example is presented to illustrate the applicability of the formulation in accordance with the current French design code BAEL-99. The results are then confronted to those derived from current design practice. The optimal solution shows clearly that significant savings can be made in the predicted absolute costs of the construction materials to be used.

In the present article, 3D Finite Element Model (FEM) of a bridge structure under load dynamics is performed in order to assess the sensitivity study of Load-Dependant Ritz vectors (LDR) on modal and seismic responses of cable stayed bridges. In this context, two techniques are examined in the present study for solving structural dynamics problems; the Traditional Modal Superposition (TMS) technique and that of Load-Dependent Ritz orthogonal vectors (LDR). The latter is based on a very efficient algorithm allowing the systematic generation of Load-Dependent Ritz orthogonal vectors (LDR), the accuracy of this method is significantly influenced by the selection of LDR vectors used for the modeling of the structural behavior. The cable-stayed bridge connecting two districts in eastern Algeria, characterized by an expected Peak Ground Acceleration (PGA) equal to 0.275g in accordance with Algerian seismic design code is selected in order to perform critical modal properties such as, freq...

This article presents the main results of three-dimensional (3-D) numerical investigation of asphalt pavement structures behaviour using a coupled Finite Element-Mapped Infinite Element (FE-MIE) model. The validation and numerical performance of this model are assessed by confronting critical pavement responses with Burmister's solution and FEM simulation results for multi-layered elastic structures. The coupled model is then efficiently utilised to perform 3-D simulations of a typical asphalt pavement structure in order to investigate the impact of two tire configurations (conventional dual and new generation wide-base tires) on critical pavement response parameters. The numerical results obtained show the effectiveness and the accuracy of the coupled (FE-MIE) model. In addition, the simulation results indicate that, compared with conventional dual tire assembly, single wide base tire caused slightly greater fatigue asphalt cracking and subgrade rutting potentials and can thus ...

This article presents the main results of a numerical investigation on the uncertainty of dynamic response of structures with statistically correlated random damping Gamma distributed. A computational method based on a Linear Statistical Model (LSM) is implemented to predict second order statistics for the response of a typical industrial building structure. The significance of random damping with correlated parameters and its implications on the sensitivity of structural peak response in the neighborhood of a resonant frequency are discussed in light of considerable ranges of damping uncertainties and correlation coefficients. The results are compared to those generated using Monte Carlo simulation techniques. The numerical results obtained show the importance of damping uncertainty and statistical correlation of damping coefficients when obtaining accurate probabilistic estimates of dynamic response of structures. Furthermore, the effectiveness of the LSM model to efficiently pred...

Analytical expressions for the determination of hydro-seismic forces acting on a rigid dam with irregular upstream face geometry in presence of a compressible viscous fluid are derived through a linear combination of the natural modes of water in the reservoir based on a boundary method making use of complete sets of complex T-functions. The formulas obtained for distributions of both shear forces and overturning moments are simple, computationally effective and useful for the preliminary design of dams. They show clearly the separate and combined effects of compressibility and viscosity of water. They also have the advantage of being able to cover a wide range of excitation frequencies even beyond the cutoff frequencies of the natural modes of the reservoir. Key results obtained using the proposed analytical expressions of the hydrodynamic forces are validated using numerical and experimental solutions published for some particular cases available in the specialized literature.