Selective demolition should permit the recovery of a large volume of reusable and recyclable material unlike conventional demolition. It is therefore necessary to assess the attributed economic and environmental impact first. HISER project has developed a Building Information Modelling for Smart Demolition (BIM-SD) tool to support the collection and management of information of materials through smart processing of data in the pre-demolition stage. The software interface has been oriented to laptops and touch screen systems. It can be used in almost any portable device supporting WebGL. The expected benefits include improved reliability of calculation, easier traceability of materials and quicker evaluation of alternative demolition/recovery options.
This tool is being demonstrated in several demolition projects through four case studies including a range of geographical situations and building typologies. For each project, the demolition planning is carried out by means of (a) traditional practices (e.g. inventory based on visual inspection, etc.) and (b) definition of BIM geometric model, identification and quantification of waste materials, data processing by means of the BIM-SD tool and automatic generation of waste management documents. After the execution of the selective demolition, time and cost for each alternative are compared.
One of the case studies concerns the demolition project of an old train station in Durango (Spain). The building includes offices, warehouses, bathrooms and housing. In general, the structure is made of reinforced concrete (pillars, beams and floor slabs) and ashlar and stone masonry for the facades, brick walls for the interior partitions, wooden floors and wood and tiles roofs.
Ihobe and Tecnalia, HISER beneficiaries, together with the Public Manager of the railway infrastructure of the Basque country (ETS), agree to validate the HISER BIM-SD tool in this demolition project. The budget for this demolition project with built surface of 1700m2 is 1.19M€. The pre-demolition activity starts with a mapping of the building and an onsite survey for identification of elements and hazardous materials. This is done by traditional practices and by using laser scanning technology and HISER BIM-SD tool.
The first method implies the review of the existing drawings (from the construction stage and not updated), the identification of main constructive typologies and materials and the location and quantification of hazardous materials (asbestos panels in an annex roof). The generic information about the building (built surface, typology, main use, construction year, etc.) is used to estimate the amount of expected waste materials. These activities, including the reporting, take approximately 3 working days (25 person-hours).
The second option implies the scanning of the interior and exterior of the building with a portable laser scanner device, the obtaining of the points clouds and the generation of the BIM file (IFC format). This file contains a simple architectural model of the building with basic information about the types of elements, their location and geometry. Then HISER BIM-SD tool is used to inventory all the elements, defining the typology (from local databases) and the properties for component materials quantification (thickness, density, reinforcement ratios, etc. among other parameters). Some additional debugging of the tool code has been necessary to obtain the correct quantities. Then the tool automatically generates the corresponding report. These activities take about 2 weeks (80 person-hours) in a non-optimized procedure. The complete pre-demolition audit costs about 10,000€ (including the service of the scanner equipment and software licenses), which is about five times the cost of the traditional simplified audit. However, it is still under the 1% of the demolition project budget and it can better support the selective demolition process. In this case, additional revenues can be obtained in case of an appropriate market return of the recovered fractions, reduced taxes of some C&DW clean fractions landfilling and partial onsite recycling of the materials for the next construction project.
Final economic evaluation and accuracy of the materials amounts estimation will be seen in the next newsletter. Keep visiting HISER website!
Building of the old train station (left) and screen capture of the inventory of elements (right)
