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Following the L’Aquila earthquake, a research team coordinated by Italian engineering consulting company D’appolonia redoubled their efforts to design protection solutions for buildings exposed to natural disasters. The project focuses on an intelligent composite “seismic wallpaper” for the reinforcement, strengthening, monitoring and management of civil infrastructure vulnerable to earthquakes.
(Published on April 2010 – JEC Magazine #56)
The Spring 2009 earthquake in L’Aquila (central Italy) killed some 300 people and destroyed 15,000 houses.
Following the catastrophe, the job of the civil engineers was to assess the state of the buildings that were still standing and to decide how to reinforce them. The engineers elected to use engineered carbon- or glass-fibre fabrics as reinforcement.
The Polytect project
In the Venice area, 500 kilometres away from the earthquake’s epicentre, a research centre has been tasked under the European Polytect research project with designing textiles for the future – in this case, materials capable of protecting buildings that are vulnerable to natural catastrophes such as earthquakes or landslides The technology goes even further, as the materials are equipped with sensors capable of assessing any damage.
One of the engineers at the centre, Thomas B. Messervey, explains: “The idea is simple. You have to manage to make the buildings resemble the human body more, and build a skin for them. So, by cross-referencing the information obtained from the sensors, the state of the building can be monitored over the long term and a sort of structural model can be built. All this can be used to try to find the answers to four questions:
One of the various products that have been designed along these lines is a composite seismic wallpaper, which is the winner of the 2010 JEC Award in the Building and Construction category.
The composite seismic wallpaper
The composite seismic wallpaper consists of the following components: fibre-optic sensors, multiaxial, warpknitted glass and polymer fibres, nanoparticle-enhanced coatings for the textile fabric, nanoparticle-enhanced mortar to bond the textile to the structure, the structure to be reinforced, and an interrogation system to acquire data from the sensor-textile fibre material type, orientation and density were optimised for the large forces and complex material behaviour associated with civil infrastructure, masonry, and earthquakes. Multiaxial textile structures are superior in this regard.
The textile was then coated for durability and to enhance the textilemortar bond interface. The specific nanoparticle-enhanced polymer coatings for the innovation were produced by the team members. The textiles were then applied to a structure using a mortar compound. This mortar compound was also enhanced by nanoparticle polymer additives. Embedded sensors were then routed to receptacles to create common interrogation points. Permanent or portable interrogation units could then be utilized to collect and store data for engineering analysis.
The composite seismic wallpaper is intended as a full-coverage or widearea reinforcing solution for unreinforced masonry buildings and structures. This avoids stress concentrations that occur at the boundaries of where there is and where there is not a reinforcing composite. The solution is simple, cost effective and easy to apply. When applied as a full-coverage solution and tested in large-scale laboratories that conduct national standardisation testing for Germany, this solution provided over 200% increases in structural strength (max. load) and over 200% increases in structural ductility (max.deformation). Walls vulnerable to brittle behaviour and collapse were being held together even after they cracked.
Reinforcing is only half of the benefit of the seismic wallpaper. This composite features embedded sensors so that measurements can be taken before, during, and after seismic events. These measurements can be static or dynamic (high frequency).
Engineers utilize such data to control new construction, to assess and quantify the benefit of retrofit actions, and to help manage the structure over time.
State of development
The development phase lasted 4 years, involving material optimization, manufacturing, material testing, laboratory testing, numerical modelling and verification, and field testing.
As a full system, the composite seismic wallpaper was tested on over 120 smallscale (1.5 m x 1.5 m) and large-scale (2.5 m x 2.5 m) test pieces to evaluate,
optimize and characterize system performance. At the end of 2009, the company was in the final preparation stage for an experiment on a two-storey stone building being tested at the European Centre for Training and Research in Earthquake Engineering (EUCENTRE) in Pavia, Italy. During the test, a full-scale multi-storey structure will be subjected to failure on a shaking table and the results with and without the composite reinforcing system will be compared. All parts of the composite solution will be evaluated during the test: sensors, fibres, manufacturing, coatings, mortars, interrogation, data processing and data interpretation.
Individual components of the composite system are now market products. Partner SMARTEC has added two project-developed fibre-optic sensors to its product catalogue. Partner SAFIBRA has launched its lowcost fibre-optic interrogation system. Partner BGP Polymers is now selling its nanoparticle-enhanced coatings and mortars and SELCOM has the sensorembedded textile SENTEX 8300 (sensorized textile) ready for sale.
As the composite system developer, D’Appolonia has partnered with SMARTEC, SELCOM and the EUCENTRE to get these materials to be part of the repair and reconstruction efforts ongoing in the L’Aquila area. Through SMARTEC’s SHMLive service, data measurements can be uploaded to the internet for remote assessment and management.
This innovation was initially intended for the construction of houses, buildings and engineering works. However, the instrumented skin concept could be applied to any structure incorporating composite materials, such as boats, wind turbines and all sort of vehicles, including aircraft.