The ELSA reaction wall is a facility of unique dimensions and capabilities in Europe and worldwide, capable of conducting experimental tests on 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 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.
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.
Recent projects
SlabSTRESS: Slab structural response for seismic European design
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 interior, edge and corner slab-column connections. The test campaign included pseudo-dynamic tests at the serviceability and ultimate limit states and quasi-static tests with increasing cyclic displacement. SlabSTRESS provided an in-depth understanding of the role of individual slab-column joints and their interaction with the overall response of the structure to different levels of lateral actions.
EQUFIRE: Multi-hazard performance assessment of structural and non-structural components subjected to seismic and fire following earthquake
The EQUFIRE project studied the post-earthquake fire performance of a four-storey three-bay steel frame with concentric bracings in the central bay, with a view to improving existing design guidelines and future standards. Tests were performed at the ELSA Reaction Wall and at the furnace of the Federal Institute for Materials Research and Testing (BAM). The experimental activities at the ELSA Reaction Wall comprised pseudo-dynamic tests on a full-scale specimen of the first storey of the building, while the upper three storeys were numerically simulated. Conventional and earthquake-resistant fire protection systems were tested.
SERFIN: Seismic retrofitting of RC frames with RC infilling
The SERFIN project studied the effectiveness of seismic retrofitting of multi-storey multi-bay reinforced concrete frame buildings by converting selected bays into new walls through infilling with reinforced concrete. A full-scale model, consisting of two four-storey (12m tall) three-bay (8.5m long) parallel frames with the central bay infilled with a reinforced concrete wall, was tested with the pseudo-dynamic method. The frames were designed and detailed for gravity loads only and were typical of similar frames built in Cyprus in the 1970’s. Different connection details and reinforcement percentages for the two infilled frames were used in order to study their effects on the structural response.
RETRO: Assessment of the seismic vulnerability of an old RC viaduct with frame piers and study of the effectiveness of different isolation systems through pseudo-dynamic test on a large scale model
The RETRO project aimed at studying the seismic behaviour of existing reinforced concrete bridges and the effectiveness of innovative retrofitting systems. Two specimens (scale 1:2.5), a frame pier of 2 levels (height 5.8 m) and a frame pier of 3 levels (height 10.3 m), have been built and tested using the continuous pseudo-dynamic method with the non-linear substructuring technique, including the modelling of the remaining entire viaduct to which they belong. Two test configurations have been considered: 1) retrofitted viaduct using friction pendulum isolators, and an 2) as-built configuration.
DUAREM: Full-scale experimental validation of dual eccentrically braced frame with removable links
Conventional seismic design is based on dissipative structural response, which implicitly accepts structural damage under the design earthquake, thus leading to significant economic losses. The DUAREM project aimed at reducing the repair costs and downtime of a structure hit by an earthquake through the concept of removable dissipative members and re-centring capability of the structure. The concept was implemented in a dual structure that combined i) steel eccentrically braced frames with removable bolted links and ii) moment resisting frames. The feasibility of the concept was validated through pseudo-dynamic tests of a full-scale model.
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.
| 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 pseudo-dynamic 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 pseudo-dynamic 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 pseudo-dynamic test technique that 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. 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 of innovative constructions. This offers a major opportunity to the European construction industry to enhance its competitive position in world 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.