Pierre Pegon

• Ingénieur, Docteur Ingénieur, Docteur ès-Science Physique
• Active Senior former Responsible for ELSA and Hoplab Laboratory Activities at European Commission

The paper describes the results of an experimental campaign on the seismic behaviour of a full-scale concentrically braced steel frame designed according the EC8 and equipped with different types of passive fire protection. In this respect, fire protection boards made of calcium silicate and mineral spray-based fire protections were applied to diss...

This paper discusses the results of a series of hybrid earthquake tests on a full‐scale reinforced concrete (RC) building with masonry infills. The prototype was a five‐story structure representing the vulnerable part of a typical RC building in Southern Europe, with beams stronger than the columns and masonry infill walls weaker than the surroundi...

This paper presents an overview of the developments performed at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre of European Commission concerning the new generation of servo-hydraulic real-time digital controller/acquisition system adopted in large scale experiments. The hardware architecture is based on Ether...

Full-scale testing of a two-storey flat slab structure is reported, undertaken in the SlabSTRESS research project; the construction and testing were planned and carried out at the ELSA laboratory of the European Commission's Joint Research Centre. The dimensions are three bays by two, spans 4.5 and 5 m, slab thickness 0.2 m, interstorey height 3.2...

The SlabSTRESS project investigated the behaviour of a full-scale Reinforced Concrete flat slab building under both gravity loads and seismic lateral actions. The two-storey structure had 9.0 m × 14.5 m plan dimensions, three bays in the loading direction and two orthogonally. This layout enabled to test simultaneously three types of slab-column co...

This work introduces a method for the identification of linear stiffness and viscous damping parameters from a one-degree-of-freedom force-displacement cycle. Using an original approach, the stiffness parameter is derived by a least-square formula from the discrete input force-displacement point coordinates of the loop. The damping ratio is obtaine...

The European Commission‘s Joint Research Centre (JRC) gives leading researchers from across Europe and beyond access to its world-class facilities and laboratories, enabling state-of-the-art experimental research, collaboration and capacity building with a European dimension. It does so through the programme for open access to JRC research infrastr...

Flat slab buildings for commercial, office and residential use are built in many countries. Yet, their behaviour under seismic and gravity actions is still not very well understood. Many studies have been carried out in North America but European research is lagging behind and currently Eurocode 8 does not cover the design of buildings with flat sl...

The EQUFIRE project aims to study the post-earthquake fire performance of steel frame structures and is part of the Transnational Access activities of the SERA project (www.sera-eu.org) at the ELSA Reaction Wall of the European Commission-Joint Research Centre. As it has happened in many historical occasions, after an earthquake, earthquake-induced...

This work introduces a method for the identification of linear stiffness and viscous damping parameters from a one-degree-of-freedom force-displacement cycle. Using an original approach, the stiffness parameter is derived by a least-square formula from the discrete input force-displacement point coordinates of the loop. The damping ratio is obtaine...

This article presents a novel approach to model validation and to the calibration of complex structural systems, through the adoption of heterogeneous (numerical/physical) simulation based on dynamic substructuring (HDS). HDS isolates the physical sub-system (PS) that contains the key region of nonlinear behavior of interest and is tested experimen...

Data are one of the main assets of earthquake engineering. Laboratory experiments can be extremely expensive and time consuming to replicate and, therefore, long-term preservation of experimental data and sharing the data with users has become one of the disciplinary priorities. There is a growing demand for international partnerships, which create...

An upgraded hybrid cyber-physical technique was introduced to assess the seismic response of a reinforced concrete motorway bridge and the effectiveness of the friction-pendulum seismic isolation. The two independent roadway bridge was built in the 1960s in Italy and it spans over twelve couples of portal frame piers. Two of the piers (scale 1:2.5)...

Modern seismic codes allow for inelastic deformation in dissipative zones during design earthquakes, accepting damage to the relevant structural parts to a certain extent. Experience has shown that repair work is needed after moderate to strong earthquakes. The use of structural systems that are easily repairable is therefore beneficial in seismic...

The response of 13 reinforced concrete shear walls submitted to successive seismic tests has been postprocessed to produce time histories of secant stiffness and displacement oscillation amplitude. For every wall an envelope curve of displacement amplitude versus stiffness is identified which is fairly modelled by a straight line in double logarith...

The SAFE experimental programme consists of a series of 10 specimens of shear walls, with different reinforcement ratios, tested until their ultimate capacity under seismic input motion by the pseudo dynamic method. A unique input signal is used, calibrated for controlling the seismic demand. Its input central frequency is selected so that for some...

The unpredictable consequences of earthquakes have proven the necessity to study the shear mechanism of low-rise reinforced concrete walls further. Experimental testing remains the preferred approach to gather insight into the workings of the material and structural elements as the complex behavior of reinforced concrete does not lend itself to wid...

In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a co...

In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a co...

The European scientific community is currently highly fragmented, with each laboratory holding experimental data, stored in some cases in a non-structured way. As a consequence, dissemination and use of experimental results outside the laboratory where they are produced can be problematic. This leads to wasteful duplication of tests and ultimately...

This paper deals with the assessment of the seismic response of an old reinforced concrete (RC) viaduct and the effectiveness of friction-based retrofitting systems. Emphasis has been paid to an old bridge not properly designed for seismic action consisting of twelve portal piers which support a thirteen-span bay deck for each independent roadway....

RETRO project aims at studying the seismic behaviour of existing reinforced concrete (RC) bridges and the effectiveness of innovative retrofitting systems. A typical as-built RC highway viaduct, which was designed primarily for gravity loads, has been analysed experimentally. The objective of the laboratory test program is twofold: 1) improve the k...

The assessment of the seismic performances of an old concrete bridge was conceived within the RETRO Transnational Activity funded by the SERIES research project. The installation of a couple of isolation devices -one per column- for each pier portal frame interposed between the cap beam and the deck was proposed as seismic retrofit, which fully com...

Hybrid Simulation with Dynamic Substructuring (HSDS) defines a class of hybrid numerical-experimental techniques capable of simulating the nonlinear response of a dynamic system. As far as complexity of emulated structures grows, the role of integration algorithms becomes more and more crucial. In fact, today control systems run at sampling times o...

Conventional seismic design philosophy is based on dissipative structural response, which implicitly accepts damage of the structure under the design earthquake and leads to significant economic losses. Repair of the structure is often impeded by the permanent (residual) drifts of the structure. The repair costs and downtime of a structure hit by a...

In common with many scientific disciplines, earthquake engineering research is increasingly focusing on large international collaborations to address complex problems. Data integration is a key requirement to facilitate joint research efforts and improve experimental outcomes. Development and implementation of a novel virtual database is presented,...

This paper addresses the strength and deformation capacity of stiff squat shear wall subjected to monotonic and pseudo-static cyclic loading using experiments and analysis. Reinforced concrete squat shear walls offer great potential for lateral load resistance and the failure mode of these shear walls is brittle shear mode. Shear strength of these...

The RETRO project aims at studying the seismic behaviour of existing reinforced concrete bridges (RC) and the effectiveness of innovative retrofitting systems. Emphasis has been paid on old bridges generally not properly designed for seismic action. On the basis of a previous experimental campaign consisting of cyclically imposed displacements on 1...

Within the frame of the European project IRIS, five reinforced concrete walls have been tested in shear at the ELSA. The thickness of the wall was exceptionally large (40cm) for this kind of test. The testing setup was able to apply quasistatically a shear force of up to 12 MN by means of four horizontal actuators and the vertical load and rotation...

The “Retro” project funded by the European commission within the Series-project aims at studying numerically and experimentally the seismic behaviour of an old existing reinforced concrete bridge with portal frame piers and the effectiveness of different isolation systems. An experimental test campaign is performed at ELSA Laboratory of JRC (Ispra,...

At the beginning of the project, the access and exchange of data within the European scientific community was highly fragmented and the diffusion of information among laboratories was not sufficient. The outcome of an inquiry performed among partner laboratories at the beginning of SERIES showed that data storage in an unstructured way was the comm...

The European Laboratory for Structural Assessment performs tests of full-size specimens of civil engineering structures and contributes to the scientific knowledge on the behaviour of different structural typologies. Many of the testing campaigns are oriented to the improvement of design standards such as the Eurocode8, which is the European standa...

Experimental methods such as hybrid or pseudo-dynamic tests are always subjected to experimental errors which effect on the obtained response is important to assess. An analytical linear model formulated on state-space equations has been developed for a multi DoF hybrid testing system including the components of the control and the specimen. For an...

The European Laboratory for Structural Assessment (ELSA) is involved in the development of advanced control strategy for improving the performances of the servo-control systems used for pseudo-dynamic testing on large civil structures or on subcomponents using substructuring method. Two research lines are pursued: advancing of control algorithm and...

The present paper focuses on the research activities, namely networking activities and pseudo-dynamic test projects, being carried out at the European Laboratory for Structural Assessment (ELSA) of the Joint Research Centre of the European Commission (EC), as part of the Seismic Engineering Research Infrastructures for European Synergies (SERIES) p...

In the IRIS project (European 7 th framework program) we have designed an original experimental setting for assessing the structural fragility of thick shear-walls. The main motivation is to improve the understanding of the non-linear behaviour under seismic loads of structures typical for the existing NPPs. In this context it is not only important...

By comparison of dynamic and pseudo-dynamic tests, it is shown that conventional construction materials exhibit pure hysteretic damping and consequently, when quasistatic restoring forces are measured directly, the addition of viscous damping in the equation of motion must be avoided unless it is intended to reflect missing physical elements. Equal...

The classic step-by-step Pseudo-dynamic (PsD) method is relatively easy to implement, including the case of substructuring, but obliges to a very low execution speed of the test. A big improvement is introduced by the continuous PsD method that allows for a faster execution and improves the quality of the results by making a more effective use of t...

The classic step-by-step Pseudo-dynamic (PsD) method is relatively easy to implement, including the case of substructuring, but obliges to a very low execution speed of the test. A big improvement is introduced by the continuous PsD method that allows for a faster execution and improves the quality of the results by making a more effective use of t...

A novel partitioned algorithm able to solve ODEs arising from transient structural dynamics is presented. The spatial domain is partitioned into a set of disconnected subdomains owing to computational or physical considerations, and continuity conditions of velocity at the interface are modelled using a dual Schur formulation, where Lagrange multip...

A general approach to the definition and assessment of response errors in dynamic and pseudo-dynamic tests is presented. By use of complete measurements during the test, the characteristics of the experimental and the prototype system can be estimated by means of a linear ideal representation. This allows comparing quantitatively in terms of eigenf...

The deleterious effect of control errors in the obtained response for shaking-table, pseudo- dynamic and hybrid tests can be quantified in a standard way by assessing the frequency and damping distortion in the obtained response as identified from equivalent linear models. The identified linear models are based only on the measurements done during...

Real-time testing with dynamic substructuring (RTDS) is a novel form of hybrid numerical-experimental testing technique used to simulate structures subjected to seismic loadings. By imposing compatibility and equilibrium conditions at the interface between the numerical substructure and the physical substructure, respectively, the substructures are...

In order to predict the dynamic response of a complex system decomposed by computational or physical considerations, partitioned procedures of coupled dynamical systems are needed. This paper presents the convergence analysis of a novel parallel interfield procedure for time-integrating heterogeneous (numerical/physical) subsystems typical of hardw...

This work presents the development and implementation of a domain decomposition approach for solving dynamics problems involving continuous testing with analytical substructuring in the non-linear range. This approach implements an inter-field parallel time integration procedure suitable to work with an explicit experimental synchronous process usi...

The ELSA laboratory is equipped with a large reaction-wall facility and has acquired its best expertise on the development and implementation of innovative experimental techniques mainly related to testing large-scale specimens by means of the pseudo-dynamic method. Relevant achievements within the testing techniques, such as the continuous pseudo-...

Real-Time Hardware-in-the-loop (RTHIL) is a novel form of heterogeneous numerical-experimental testing capable of assessing the behaviour of structures subjected to dynamic loadings. The technique involves splitting the emulated structure being tested into two parts: the Physical Substructure (PS), which contains a key region of interest and is exp...

During the last decade, the European Laboratory for Structural Assessment (ELSA) has played a major role in Europe in the execution of seismic tests on large structural models. Most of the tests performed at ELSA have been developed in collaboration with many research centres and have produced results of great value for the validation of several ch...

In order to meet the objectives of earthquake risk mitigation worldwide and progress towards performance based seismic design and assessment, there is also a need for experimental facilities capable of handling complex structures and systems, to understand real effects of phenomena like soil-structure interaction and to combine physical and numeric...

The ELSA laboratory is provided with a large reaction-wall facility and has acquired its best expertise on the development and implementation of innovative experimental techniques mainly related to testing of large-scale specimens by the pseudodynamic method. Important examples are represented by the bidirectional tests performed on multi-storey bu...

Pseudo-dynamic tests on a large-scale model of an existing six-pier bridge were performed at the ELSA laboratory using the substructuring technique. Two physical pier models were constructed and tested in the laboratory, while the deck, the abutments and the remaining four piers were numerically modeled on-line. These tests on a large-scale model o...

Structure sous seismes: expérimentation en laboratoire

This paper describes the principles of continuous pseudodynamic testing as it is currently implemented at the ELSA laboratory as a seismic testing technique for large-size specimens. Then, by means of a linear model, the effect of the control error on the test response is characterised mainly as a decrease on the apparent damping of the structure....

Within the VAB research program, pseudodynamic tests on a large-scale model of an existing bridge were carried out in the reaction wall of the ELSA laboratory of the Joint Research Centre, applying the substructuring method. Asynchronous input motion, generated for the bridge site, was considered at the base of the piers and abutments. Non-linear s...

Palavras Chave: Ensaios Sísmicos, Ensaios Pseudo-dinâmicos, Avaliação, Reforço RESUMO O Laboratório ELSA (Laboratório Europeu de Avaliação Estrutural), do Centro Comum de Investigação (CCI) da Comissão Europeia, em Ispra, Itália, desenvolve desde 1992 uma intensa actividade de investigação de carácter experimental e numérico no domínio do comportam...

A representative model of built cultural heritage structure was designed using 2D and 3D numerical modelling in order to test at the laboratory and its behavior was also characterized. Large blocks assembled with mortar and masonary were used to make the structures. The results revealed that the deformation and damage patterns can be predicted accu...

This work presents an alternative definition of the numerical angular frequency and numerical damping ratio, within the framework of direct time integration of second-order differential equations. The classical approach, based on the amplification matrix concept, deals with the ability of the numerical schemes to deliver an accurate response in tim...

The paper describes the distinctive features of the pseudo-dynamic test method as implemented at the ELSA reaction-wall facility. Both hardware and software aspects are considered. Particular attention is devoted to the digital control system and to a coupled numerical–experimental substructuring technique allowing realistic earthquake testing of v...

77 Abstract The ELSA laboratory is provided with a large reaction-wall facility and has acquired its best expertise on the development and implementation of innovative experimental techniques mainly related to testing of large-scale specimens by the pseudo-dynamic method. Important examples are represented by the bidirectional tests performed on mu...

: The results of the seismic tests on several reinforced-concrete shear walls and a four-storey frame are analysed in this paper. Each specimen was submitted to the action of a horizontal accelerogram, with successive growing amplitudes, using the pseudodynamic method. An analysis of the results allows knowing the evolution of the eigen frequency a...

The seismic performance of civil engineering structures may be estimated by using two levels of modelling. At the local level, each constituent has its own constitutive law and geometric finite element support. The main phenomena such as the cracking and the crushing of concrete and masonry could be reproduced by using the continuous damage or plas...

This document presents the implementation of a fully automatic algorithm for the meshing of structures made of blocks connected together by joint interfaces. Starting from the definition of the corner nodes of the blocks, the algorithm is able to produce the mesh of each block in such a way the faces that are in contact are topologically identical....

In this paper, two different time-domain methods are proposed. Both have been successful in the identification of the natural frequencies, damping ratios and mode shapes of large structures seismically tested by using the pseudodynamic method. The first method is formulated as a spatial model in which the stiffness and damping matrices are directly...

In this paper, we discuss procedures for computing the mesh movement in staggered FSI-simulations. The mesh movement is divided into a global and a local level. The global level is based on the solution of an incremental linear-elastic solid model using the structure movement as Dirichlet boundary conditions, and error estimates to guide the node r...

This paper illustrates the modelling strategy that has been pursued at ELSA for the last eight years. Some representative examples of the results obtained to date are described and shortly discussed. Emphasis is put on the complementary character of local and global modelling and on the importance of working in an integrated computer environment ra...

This paper presents the current state of development of a system designed to perform fast substructure pseudodynamic tests, which opens the way for accurate testing of the earthquake response of structures outfitted with various components and devices having velocity dependant restoring forces. The objective of the research is to create a dynamic t...

. This work focuses on the modelling of nonlinear response of reinforced concrete structures by means of the finite element method. A new technique which employs a variable mesh in order to reduce the computational cost of classical approaches is presented. For some piecewise linear constitutive models which are widely employed for the modelling of...

Object-oriented programming has already shown to provide numerical scientists with adequate means for improving modularity in basic linear finite element codes. It is demonstrated here that this holds for nonlinear analysis, provided that the right types of objects with adequate capabilities are defined for handling nonlinear behaviours. In order t...

One of the major reasons why finite element codes are difficult to keep clean and maintainable is that operations involving nodal information (and in particular, boundary conditions) show up in many sections of the programs and in many different contexts. The matter is further complicated by the inadequacy of the unstructured procedural programming...

This paper presents the state-of-the-art of the hybrid simulation method with substructuring developed at the European Laboratory for Structural Assessment (ELSA) at JRC-Ispra. The Continuous Pseudo Dynamic (PsD) test method is implemented by means of a synchronous process with short control period (2 ms) and small time step. This introduces some c...

Two algorithms for the stress update (i.e., time integration of the constitutive equation) in large-strain solid mechanics are compared from an analytical point of view. The order of the truncation error associated to the numerical integration is deduced for each algorithm a priori, using standard numerical analysis. This accuracy analysis has been...

Various levels of modelling of reinforced concrete beams are presented and compared. Their complementary character is outlined in some simple cases. Further studies are proposed.

The Pseudodynamic (PSD) test method combines the numerical integration of the motion equations of a structure condensed at selected degrees-of-freedom (d.o.f.) with the on-line measurement of the reaction forces needed to impose this computed motion. The results obtained with this testing method can be strongly corrupted by the spurious propagation...

See paper@http://www.lib.ncsu.edu/resolver/1840.20/31938. This work presents an alternative definition of the numerical angular frequency and numerical damping ratio, within the framework of direct time integration of second-order differential equations. The classical approach deals with the ability of the numerical scheme to deliver an accurate r...

See paper@http://www.lib.ncsu.edu/resolver/1840.20/32357. The distinctive features of the pseudo-dynamic test method as implemented at the largest reaction-wall facility are described. Software aspects are considered. Particular attention is devoted to a coupled numerical-experimental substructuring technique allowing realistic earthquake testing o...

See paper@http://www.lib.ncsu.edu/resolver/1840.20/32225

The homogenization theory for periodic media is used for deriving the in-plane macroscopic non-linear behaviour of masonry. Two different assumptions are envisaged: plane stress and generalized plane strain. Assuming a continuum damage modelling for the brick and the mortar, the two-dimensional boundary value problem associated with the homogenizat...

Making a finite element code easier to maintain is achieved by further modularizing it. Due to its two levels of modularity (of procedures and data), object-oriented programming is the method of choice. Its potential is investigated in two bottlenecks of finite element programming where so far it has not proved significantly more successful than cl...

Abstract— Two scalar parameters relating to stored energies are defined along an arbitrary cyclic loading path for an isotropic elastic-plastic continuum. The definitions of the parameters are introduced in the one-dimensional case. The tensorial generalization is developed firstly under the mechanical point of view and secondly focusing attention...

Analysis methods and modelling techniques for monumental structures are discussed. In particular, a review of the non-linear models is made. Aspects such as: identification of model parameters, monotonic and cyclic behaviours, as well as tension and compression behaviours, are discussed. Furthermore, the results of preliminary non-linear numerical...

Dans plusieurs pays européens, les structures de bâtiments sont surtout constituées de portiques en béton armé et de mures de remplissage en maçonnerie. Ces panneaux de remplissage sont souvent considérés comme des elements non-structuraux, ont une influence non négligeable sur le comportement sismique des portiques, par exemple en les rigidifiant....

This paper highlights a theoretical limitation of the classical Rayleigh damping which may lead to inconsistent results, in particular when non-uniform seismic loading is considered in a dynamical analysis. Another proportional damping, able to work consistently with a description of motion, in an absolute frame is proposed in alternative. This alt...

The paper describes the distinctive features of the pseudo-dynamic test method as implemented at the largest European reaction-wall facility. Both hardware and software aspects are considered. Particular attention is devoted to the digital control system and to the time integration algorithms. A test-restart procedure well suited for stiff/brittle...

This note explains how to realize PSD testing with substructuring when the ground acceleration (earthquake loading) is no longer spatially uniform.

Despite its texture as a periodic composite material, masonry is generally modelled as a ‘concrete-like’ material, so that its anisotropic nature is not taken into account. A way to derive an enhanced constitutive model for masonry, closely related to the behaviour of its constituent materials (mortar and bricks) and to its geometry (bond pattern,...

Six large-scale (1:2.5) bridge specimens have been constructed and are being tested pseudodynamically at the ELSA laboratory. The tests are being conducted in the framework of the activities of the integrated European programme of the pre-normative research in support of Eurocode 8 involving eighteen research institutions from the European Union. T...

This paper presents some computations performed in order to analyse the behaviour of frame structures infilled by hollowed masonry panels. after a brief presentation of the fixed-crack model used for the modelling of the masonry material, the paper focussed on the study of the eventual differences of behaviour between the masonry infill panel in an...

The paper presents an overview of the testing activity at large scale performed at the ELSA reaction wall, in the framework of an integrated European program of pre-normative research in support of Eurocode 8. Furthermore, the main lines of a new European network research programme are indicated.

A series of pseudodynamic tests were conducted on a full-scale four-storey reinforced concrete building designed according to Eurocodes 2 and 8. The building was 10 m long by 10 m wide, and was 12.5 m high.. It was designed as a ductility class High structure, for typical live loads and for a peak ground acceleration of 0.3 g and medium soil condit...

The homogenization theory for periodic media is used for deriving the in-plane macroscopic non-linear behaviour of masonry. Two different assumptions are envisaged: plane stress and generalized plane strain. Assuming a continuum damage modelling for the brick and the mortar, the twodimensional boundary value problem associated with the homogenizati...