Asterios A. Liolios

A computational approach for the earthquake response of cable-braced reinforced concrete structures under environmental actions

A numerical treatment for the seismic response of reinforced concrete structures containing cable elements is presented. The cable behaviour is considered as nonconvex and nonmonotone one and is described by generalized subdifferential relations including loosening, elastoplastic - fracturing etc. effects. The problem is treated incrementally by double discretization: in space by finite elements and piece-wise linearization of cable - behaviour, and in time by the Newmark method. Thus, in each time - step an incremental linear complementarity problem is solved with a reduced number of problem unknowns.

A NUMERICAL APPROACH FOR ESTIMATING THE EFFECTS OF MULTIPLE EARTHQUAKES TO SEISMIC RESPONSE OF STRUCTURES STRENGTHENED BY CABLE-ELEMENTS ∗

Abstract The behaviour of reinforced concrete (RC) frames, which have been strengthened by cable elements and are subjected to multi- ple earthquakes, is numerically investigated. The purpose is to estimate damage indices in order to compare the seismic response of the structures before and after the retrofit by cable element strengthening and to select the optimum strengthening version

Pounding Effects on the Earthquake Response of Adjacent Reinforced Concrete Structures Strengthened by Cable Elements

Abstract A numerical approach for estimating the effects of pounding (seismic interaction) on the response of adjacent Civil Engineering structures is presented. Emphasis is given to reinforced concrete (RC) frames of existing buildings which are seismically strengthened by cable-elements. A double discretization, in space by the Finite Element Method and in time by a direct incremental approach is used. The unilateral behaviours of both, the cable-elements and the interfaces contact-constraints, are taken strictly into account and result to inequality constitutive conditions. So, in each time-step, a non-convex linear complementarity problem is solved. It is found that pounding and cable strengthening have significant effects on the earthquake response and, hence, on the seismic upgrading of existing adjacent RC structures.

Tall RC Buildings Environmentally Degradated and Strengthened by Cables Under Multiple Earthquakes: A Numerical Approach

A numerical investigation is presented for the seismic analysis of tall reinforced concrete (RC) Civil Engineering structures, which have been degradated due to extreme environmental actions and are strengthened by cable elements. The effects of multiple earthquakes on such RC building frames are computed. Damage indices are estimated in order to compare the seismic response of the structures before and after the retrofit by cable element strengthening, and so to elect the optimum strengthening version.

A Computational Approach for the Seismic Sequences Induced Response of Cultural Heritage Structures Upgraded by Ties

The seismic upgrading of Cultural Heritage structures under multiple earthquakes excitation, using materials and methods in the context of Sustainable Construction, is computationally investigated from the Civil Engineering praxis point of view. A numerical approach is presented for the seismic response of Cultural Heritage industrial buildings of reinforced concrete (RC), which are seismically strengthened by using cable elements (tension-ties). A double discretization, in space by the Finite Element Method and in time by an incremental approach, is used for the system of the governing partial differential equations (PDE). The unilateral behaviour of the cable-elements, as well as the other non-linearities of the RC frame-elements, are strictly taken into account and result to inequality problem conditions. A non-convex linear complementarity problem is solved in each time-step by using optimization methods. The seismic assessment of the RC structure and the decision for the optimal cable-strengthening scheme are obtained on the basis of computed damage indices.

A computational approach for the seismic damage response under multiple earthquakes excitations of adjacent RC structures strengthened by ties

Civil Engineering systems of adjacent reinforced concrete (RC) structures, which have been environmentally degraded, are considered in order to be seismically strengthened by cable-elements (ties). A numerical approach for estimating the effects of pounding (seismic interaction) on the response of such adjacent structures under multiple earthquakes excitation is presented. For the system of the governing partial differential equations (PDE) a double discretization, in space by the Finite Element Method and in time by a direct incremental approach, is used. The unilateral behaviors of both, the cable-elements and the interfaces contact-constraints, are strictly taken into account and result to inequality constitutive conditions. So, in each time-step, a non-convex linear complementarity problem is solved. The decision for the optimal cable-strengthening scheme is obtained on the basis of computed damage indices. It is found that pounding and cable strengthening have significant effects on the earthquake response and, hence, on the seismic upgrading of existing adjacent RC structures.

A Numerical Approach to the Non-convex Dynamic Problem of Steel Pile-Soil Interaction under Environmental and Second-Order Geometric Effects

The paper deals with a numerical approach for the dynamic soil-pile interaction, considered as an inequality problem of structural engineering. So, the unilateral contact conditions due to tensionless and elastoplastic softening/fracturing behaviour of the soil as well as due to gapping caused by earthquake excitations are taken into account. Moreover, soil-capacity degradation due to environmental effects and second-order geometric effects for the pile behaviour due to preexisting compressive loads are taken into account. The numerical approach is based on a double discretization and on mathematical programming. First, in space the finite element method (FEM) is used for the simulation of the pile and the unilateral contact interface, in combination with the boundary element method (BEM) for the soil simulation. Next, with the aid of Laplace transform, the equality problem conditions are transformed to convolutional ones involving as unknowns the unilateral quantities only. So the number of unknowns is significantly reduced. Then a marching-time approach is applied and finally a nonconvex linear complementarity problem is solved in each time-step.

A numerical approach for obtaining fragility curves in seismic structural mechanics: a bridge case of Egnatia motorway in northern Greece

Fragility curves for Civil Engineering structures represent a critically important step in seismic damage estimation process. In the present article, a numerical methodology for the evaluation of such curves for bridges is presented. The methodology is based on the Finite Element Method, combines the nonlinear static pushover procedure with the capacity spectrum method and is applied for establishing fragility curves for an existing reinforced concrete bridge with seismic stoppers in the Krystalopigi - Psilorahi section of Egnatia Motorway, in the county of Epirus, northern Greece.

Numerical analysis of the sinuous instability of a viscous capillary jet flowing down an immiscible nonviscous fluid

The sinuous instability of a viscous jet flowing down an inviscid fluid is studied. On the basis of the 3D Navier-Sokes equations for the jet the full dispersion equation of the small disturbances is derived. Numerical results are shown, illustrating both the effect of viscosity and ambient density.

A Numerical Approach for a Hemivariational Inequality Concerning the Dynamic Interaction between Adjacent Elastic Bodies

A numerical treatment of an dynamic hemivariational inequality problem in structural mechanics is presented. This problem concerns the elastoplastic-fracturing unilateral contact with friction between neighboring civil engineering structures under second-order geometric effects during earthquakes. The numerical procedure is based on an incremental problem formulation and on a double discretization, in space by the finite element method and in time by the ?-Wilson method. The generally nonconvex constitutive contact laws are piece-wise linearized, and in each time-step a nonconvex linear complementarity problem is solved with a reduced number of unknowns.