EU Science Hub

European Laboratory for Structural Assessment: Reaction Wall facility

The ELSA reaction wall is a facility of unique dimensions and capabilities in Europe and worldwide, capable of conducting experimental tests on near to full-scale specimens for the safety assessment of structures against earthquakes and other natural and man-made hazards.

By means of computer controlled hydraulic actuators it is possible to expose full scale structures to loads of dynamic strong forces and control the resulting movements with high precision. The wall and the floor are designed to resist the forces, typically several MN, which are necessary to deform and seriously damage the full-scale test models of structures.

The ELSA Reaction Wall is the largest facility of its kind in Europe and one of the largest in the World - only exceeded in Japan.

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Transnational Access to ELSA

The Joint Research Centre 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. Access of users to the ELSA Reaction Wall is regulated by the framework for access to Joint Research Centre physical research infrastructures.

The Joint Research Centre offered recently transnational access to the ELSA Reaction Wall within the Horizon 2020 project SERA (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe).

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Technical capacity

ELSA operates a 16 m-tall, 21 m-long reaction wall, with two reaction platforms of total surface 760 m2 that allow testing real-scale specimens on both sides of the wall. The actuators control system is designed in-house to perform tests with the continuous pseudo-dynamic method with substructuring, that permits testing elements of large structures, bidirectional testing of multi-storey buildings, and testing of strain-rate dependent devices.

Dimensions of ELSA Reaction Wall

Reaction wall Reaction floor Anchors
Bending moment: 200 MNm Bending moment: 240 MNm Axial force: 500 kN
Base shear: 20 MN    


Hydraulic system Actuators
Flow: 25 l/sec Load: 0.2 - 3 MN
Pressure: 210 bar Stroke:± 0.125 - 1.0 m

Areas of research

ELSA has been supporting research related to the structural/seismic safety of structures, including:

  • reference tests on reinforced concrete buildings with and without infill wall panels;
  • reference and pioneering tests on full-scale bridges, including irregular configurations, isolation and asynchronous input motion using the PsD method with non-linear substructuring;
  • tests on models of parts of monuments for the development of assessment methods and protection techniques;
  • reference tests on concrete-steel composite structures;
  • experimental tests on fibre-reinforced concrete composite structures;
  • reference tests on models representative of existing vulnerable structures for the development of conventional or novel techniques and the calibration of European codes for assessment, strengthening and repair;
  • development of the continuous PsD method, allowing more efficient seismic testing of large-scale specimens; development of base isolation and energy dissipation systems;
  • experiments on active and semi-active control of wind- or traffic-induced vibrations.

The pseudo-dynamic test technique

In addition to static and cyclic tests on large structures and components, the facility is equipped for the so-called pseudo-dynamic test (PSD) technique. The PSD enables the simulation of earthquake loading of full-scale buildings.

The structure to be tested is fixed to the horizontal floor. Once the ‘test structure’ is in place, the force that an earthquake would generate is applied through hydraulic jacks acting between the structure and the vertical wall, subjecting the structure to loads equivalent to those caused by the earthquake . For the purposes of testing the ‘earthquake’ experiment takes place in extreme slow motion, one to two hours rather than the 10 to 30 second duration of a real earthquake, allowing progressive damage and structural deformations to be accurately observed and recorded.

International collaboration

The ELSA facility is used within the framework of European Union wide integrated research programmes and is also available to external customers for performing demonstration and qualification tests on large-scale prototypes and/or validation innovative constructions. This offers a major opportunity to the European construction industry to enhance its competitive position in world-wide markets, especially in countries with high seismic risk.

Thanks to its recognition as a large-scale facility through the HCM, TMR and IHP programmes, the ELSA laboratory has been able to host a large number of users in the framework of European programmes. Around 100 international users benefit every year from the ELSA infrastructure and users from new Member States have had increased access to ELSA during FP7. In the FP7 SERIES project, ELSA hosted 30 users from nine European countries. 25 users from seven countries were hosted for the Horizon 2020 SERA project.

ELSA established scientific co-operation agreements with leading international research institutions in the field (China, Japan, Korea, Taiwan, USA, etc.). These activities create a stimulating environment for exchanging knowledge and expertise and gives the opportunity to users of ELSA to establish contacts and collaborations, as well as broad exposure to the most prominent scientific developments at European and world level.