Projects / Programmes
Pultruded orthotropic joint of the building envelope
| Code |
Science |
Field |
Subfield |
| 2.05.03 |
Engineering sciences and technologies |
Mechanics |
Numerical modelling |
| Code |
Science |
Field |
| T230 |
Technological sciences |
Building construction |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
curtain wall facades, pultrusion, orthotropy, bending stiffness, thermal conductivity, constitutive models, topological optimization, numerical FEM analyses
Researchers (11)
Organisations (1)
Abstract
Glass curtain wall facades are used in more than 80% of the high-raised buildings. Unfortunately, high heat transfer coefficient (U) values are associated with such systems. Average U values below 1 W/m2K appear unreachable due to architectural and glazing limitations. Nowadays, national codes for efficient energy usage require U values to be generally lower than 0.3 W/m2K.
CBS institute in cooperation with Trimo (parent company of CBS Institute) and Faculty of mechanical engineering (University of Ljubljana) have developed a new product Qbiss Air. Its U value ranges from 0.12 to 0.25 W/m2K at relatively low overall thicknesses (140–180 mm) which is architecturally acceptable.
The insulation panel Qbiss Air, which is implemented at Trimo’s series production, is in the field of facades a complete novelty. There is an insulative core (?=0,008 – 0,015 W/mK) between the outside and inside boards which has no capacity to carry external mechanical loads. To gain stiffness that enables self load carrying of the panel, provides appropriate mechanical resistance against wind load and prevents excessive heat bridging, it was therefore necessary to add a joining element (joint). Structural design of the present extruded thermoplastic joint provides Qbiss Air panel with required heat and sound insulation, mechanical load service and utility limit states (SLS and ULS), water ingress resistance, tightness and durability. But extruded thermoplastic composite is not optimal solution. Namely:
• thermoplastic composites readily burn and form fire spreading droplets;
• highest bending modulus reachable is at 7000 MPa. As the joint is a key contributor to the overall panel stiffness, the amount of material needed to build it depends both on the cross section shape and elastic modulus;
• lowest thermal conductivity (?) in transversal direction (the direction of actual heat loss) is 0.28 W/mK. Heat conduction through this thermoplastic composite represents great 30% of the overall building envelope heat losses.
An alternate technological process to extrusion by which present joint is being manufactured is pultrusion. Pultrusion enables design with complex internal reinforcement matrix layouts. Pultrusion thermosetting polymer matrices are poorly combustible and form no fire spreading drops. Bending modulus of up to 25000 MPa are accessible, while transversal thermal conductivity remains in range of 0.25 W/mK.
The aim of our proposed project is to develop a new pultruded joint having:
• highly orthotropic properties;
• customized stiffness in longitudinal direction – at least 10000 MPa;
• low transversal thermal conductivity (less than 0.25 W/mK);
• self extinguishing and/or no flammability.
Polymer composites are used in façade systems to break heat bridging and to increase panel's structural stiffness. Since limiting heat losses through composites themselves has not been technically addressed yet, while considering high portion of heat lost in such systems through such polymer joints, e.g. aluminum windows and curtain walls in hi-raised buildings, we propose this applied research in which improvement in heat flow could be attained at almost same production and maintenance cost.
Taking benefit of such technical solution Trimo would undoubtedly enter with enhanced Qbiss Air into large hi-raised building market, which is market Slovenia has not been present on with its own products yet. Though process of façade renewal in terms of thermal insulation improvements is currently taking place in the world there is no adequate technical solution on the market. Such research also has deep ecological impact (reduction of heat loss) and is important for regional development. From scientific standpoint this would lead to an entirely new thermo-mechanical rheological model based on micro/macro response. Implementation of the model into a commercial FEM code would enable its further use for complex structures analyses.
Significance for science
Polymer composites are used in fasade systems to break heat bridging and to increase panel's structural stiffness. Since limiting heat losses through composites has not been technically addressed yet, while considering high portion of heat lost in such systems through such polymer joints, e.g. aluminum windows and curtain walls in hi-raised buildings, we performed this applied research in which improvement in heat flow could be attained at almost same production and maintenance cost. From scientific standpoint this research would lead to an entirely new thermo-mechanical rheological model based on micro/macro response. Implementation of the model into a commercial FEM.
Significance for the country
Indirect benefits for society are to bring up excellent applied research personnel in Slovenia, and its promotion through co-financers novel products.
Most important scientific results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
