Civil engineering and construction-management students from Galway-Mayo Institute of Technology (GMIT) visited the recently constructed Human Biology Building (HBB) in NUI Galway and took part in a load test on a concrete slab with embedded sensors. The HBB is a four-storey building over basement and roof-level plant enclosure with a gross floor area of 8200m2 (Figure 1) and was constructed by BAM Ireland. The HBB is primarily constructed using precast concrete elements, including the building frame, twinwall system, hybrid concrete lattice girder slabs and hollowcore slabs, which were designed, manufactured and installed by Oran Pre-Cast Ltd in Galway. [caption id="attachment_35458" align="alignleft" width="663"]Figure 2 Figure 2[/caption] During the construction phase, a variety of sensors (vibrating wire (VW) strain gauges, electrical resistance strain gauges, thermistors – Figure 2) were embedded in the floor structure (lattice girder flat slab) to allow real-time monitoring of the structural and environmental performance of the concrete floor during the construction and operational phase of the building. [caption id="attachment_35459" align="alignleft" width="663"]Figure 3 Figure 3[/caption] The weight of students was used to apply a specified load to a concrete walkway in stages (Figure 3). The 250mm thick walkway slab is approximately 1.5m wide and spans 6m over the atrium in the HBB and consists of a 65mm thick precast lattice girder plank and 185mm insitu concrete topping. The walkway has VW strain gauges embedded at approximately 1.5m centres along the walkway. At each location, there are three VW gauges positioned through the depth of the slab (one in the precast plank and two in the in-situ topping) so that the strain and temperature profile through the slab could be measured (Figure 4). [caption id="attachment_35609" align="alignleft" width="663"]EIJ_Fig 4_RevA Figure 4[/caption]

Built2Spec European project

The embedded sensors are part of a research project in which they are being used to study the behaviour of the floor during the manufacture, construction and operational phase of the building. This project is part of the Built2Spec European project in which the structural and environmental performance of buildings are continuously monitored using smart sensor-embedded construction elements (smart building components). The HBB project is one of a number of projects which forms part of a measurement framework strategy developed at NUI Galway to continuously monitor the structural and environmental performance of buildings during construction and operation [1]. The load test is great way for students to develop a greater understanding of structural behaviour and an appreciation of the response of structures to load. Following the load test, the students are able to analyse the data and compare the actual behaviour of the floor with the predicted behaviour using design standards (such as Eurocode 2). [caption id="attachment_35461" align="alignleft" width="663"]Figure 5 Figure 5[/caption] The walkway was designed for an imposed load of 4.0kN/m2 and the load test was designed to apply an imposed load of 3.0kN/m2 in 1.0kN/m2 increments. In Figure 5, an example of the measured strain data from one of the vibrating wire strain gauges located in the precast plank (bottom of the slab) at approximately midspan in the walkway is plotted during the load test. The strain data, which was recorded every three minutes during the load test, clearly shows the incremental change in strain in response the self-weight of the students. This strain data can then be converted to bending moments and used by students to study the response of the walkway to their own self-weight. These moments derived from measured strains are compared by the students to the linear elastic finite element model developed by Oran-Precast, which is used to highlight differences between assumed and actual behaviour of the floor structure to students. It is very beneficial for students to explore the reasons for differences between actual and modelled behaviour of structures because of the increasing use of software in engineering.

'Living laboratories’ used for teaching

This load test, undertaken by the students from GMIT, is similar to the approach adopted in NUI Galway in which a number of educational buildings are used as ‘living laboratories’ [2] through the use of embedded instrumentation as a teaching tool for students to investigate a wide variety of engineering concepts. Dr Jamie Goggins, senior lecturer in civil engineering at NUI Galway and principal investigator responsible for the materials and structures research area in the Centre for Marine and Renewable Energy (MaREI), noted: “It’s envisaged that the rich data from the embedded sensors in the HBB and other demonstrator buildings in NUI Galway will be stored for many years and will be available to students and professionals for teaching and research applications. “This is the third building on the NUI Galway campus that we’ve developed as a ‘living laboratory’ – the first two being the Alice Perry Engineering Building, completed in 2010, and the Institute for Lifecourse and Society Building, completed in 2014,” he continued. “Not only are they are fantastic resources to help our students better understand building physics and structural engineering, they’re also being used in a number of European Commission Horizon 2020 and other collaborative research projects with industry and academic partners to develop and test technologies and approaches that drive design, construction and the performance of future buildings and retrofits,” Goggins concluded. In addition to the teaching applications of the embedded sensors, real-time monitoring offers potential benefits in relation to optimisation of structural components by understanding the actual behaviour of components in use and the possibility to develop and calibrate numerical models that predict structural performance. The authors would like to acknowledge the assistance of Oran Pre-Cast and BAM contractors during the HBB project. Authors: Shane Newell, lecturer and chartered engineer, Galway-Mayo Institute of Technology (shane.newell@gmit.ie) Dr Jamie Goggins, senior lecturer and chartered engineer, NUI Galway (jamie.goggins@nuigalway.ie) References [1] Newell, S., Goggins, J., & Hajdukiewicz, M. (2016). Real-time monitoring to investigate structural performance of hybrid precast concrete educational buildings. Journal of Structural Integrity and Maintenance, 1(4), 147-155. [2] Goggins, J., Byrne, D., & Cannon, E. (2012). The creation of a living laboratory for structural engineering at the National University of Ireland, Galway. The Structural Engineer, 90(4), 12-19. The Built2Spec project has been funded through the European Commission Horizon 2020 programme (2015-2018) as part of the Built2Spec project ‘Tools for the 21st century construction site’ (H2020 EeB2014 637221).