Daia Zwicky

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• Dr. sc. techn. (PhD), dipl. Bauing. ETH (MSc)
• Professor at School of Engineering and Architecture of Fribourg

Accurate prediction of concrete properties, such as compressive strength, is essential for ensuring structural performance. Particle size distribution (PSD) and nature of aggregates are key components of concrete mixtures, significantly influencing their final compressive strength. This paper presents a novel approach that leverages embedding vecto...

Highlights • Investigation on the deformation rate response of steel-timber shear connections with screws. • The stiffness increases with deformation rate and the strength is largely constant. • Numerical models predict the stiffness and peak load. • Modified stiffness and strength equations validated for practical application. • Full closed-form c...

Based on interview with D. Zwicky >> pages 22/23 To be found at https://drive.switch.ch/index.php/s/VUFOWqvThvcF0gS

This study explored the potential of using high-calcium grate ash and fly ash from wood combustion in combination with metakaolin and limestone as a replacement material for cement in low-clinker binders. Three products were investigated: sand mortars and lightweight mortars , as well as pellets in order to obtain lightweight, low-clinker, and wast...

Can be downloaded fore free from https://www.aramis.admin.ch/Texte/?ProjectID=53407

p>The use of lightweight concrete could overcome some of the disadvantages of normal-weight concrete. However, the fabrication of lightweight aggregates is energy intensive and considerably draws on non-renewable resources. The positive consequences from lighter weight on supporting structural components’ dimensions are frequently outrun by the inc...

Targeting urban and sub-urban building archetypes, generic but practice-oriented materializations of basic construction elements (slabs and walls) and their combinations were conceived for heightening of existing buildings by two to four floors. The developed concepts considered numerous construction materials and requirements from architecture, st...

Presentation of the ConDensUrbEN project at internal event

The reported research explored the feasibility of cold bonding as a method to produce low-embodied-energy lightweight aggregates from locally available biomass wastes (wood sawdust and ashes) and cement, using response surface methodology to model the effect of raw material proportions on the properties of the product. The empirical exploration com...

Presentation of the ConDensUrbEN project @ Smart Living Lunch (Smart Living Lab)

The reported research explored the feasibility of cold bonding as a method to produce low-embodied-energy lightweight aggregates from locally available biomass wastes (wood sawdust and ashes) and cement, using response surface methodology to model the effect of raw material proportions on the properties of the product. The empirical exploration com...

This study presents the evaluation of various structural analysis approaches to theoretically determine the bending resistance of flexural reinforced concrete elements strengthened with textile-reinforced mortar (TRM), which are gaining more and more attention as external strengthening layers. To assess the increase in capacity due to strengthening...

The study presented here aimed at improving mechanical properties of wood-cement compounds, basically consisting of Portland cement and of up to 60% of untreated sawdust, through an aggregate skeleton made of organic aggregates (fruit pits, crushed nut shells) and lightweight aggregates (expanded clay and glass). Experimental results show that work...

According to Swiss code SIA 262 "Concrete structures", stirrups of reinforced concrete beams must "surround the tensile longitudinal reinforcement" and must "be anchored to mobilize the static height of internal forces". For existing concrete structures, Swiss code SIA 269/2 provides stirrup detailing requirements while limiting these directives fo...

It is difficult to compete with normalweight concrete: it is pourable, usually self-compacting, hardening reasonably fast, cheap and locally available in large quantities. Its excellent fire protection and good acoustic insulation for airborne sound are further advantages in construction. But, regular concrete is very heavy, being disadvantageous f...

Probabilistic assessment of existing structures can be a powerful tool for efficiently prioritizing the necessity of maintenance interventions within usually limited budgets available for this activity of ever increasing importance – spend the limited money where it is the most effective. However, structural engineers in practice usually have neith...

When strengthening reinforced concrete slabs with textile reinforced mortars (TRM), the "correct" consideration of the global bond behaviour between textile and cementitious matrix is identified as the main challenge in determining the most appropriate global analytical model. The first model evaluated here is based on classical assumptions for str...

Article can be found here: http://blog.allplan.com/de/holzbeton

Based on interview with D. Zwicky

Keynote given at 62. BetonTage 2018 in Neu-Ulm

Holz-Zentralblatt Nr. 42, 20.10.2017, p. 973

Glass fibre reinforced polymers (GFRP) were developed in the first half of the 20th century. They have high strength (especially for tensile stresses), low density, high resistance in corrosive environments, and free formability. Despite these advantages, GFRP materials are not widely used in construction yet. The main reasons are low stiffness of...

Telefoninterview mit D. Zwicky zu seinem WooCon-Projekt : http://soundcloud.com/dlf-wissenschaft/schweizer-forscher-entwicklen-holzbeton-dlf-interview-dr-daia-zwicky

Interview with D. Zwicky on his WooCon project : http://www.rts.ch/play/tv/19h30/video/construction-a-base-de-sciure-le-beton-fait-sa-revolution?id=8928797

Interview with. D. Zwicky on his WooCon project : http://m.srf.ch/play/tv/tagesschau-spaetausgabe-wochenende/video/tagesschau-vom-17-09-2017-2200?id=0b3b871f-2a7c-4659-8c30-b35a3a450566

Based on interview with D. Zwicky

Zeitungsartikel zu Interview mit D. Zwicky

ARGUS results on press release on "WooCon" project

The Institute of Construction and Environmental Technologies (iTEC) of the School of Engineering and Architecture Fribourg (HEIA-FR) is active in research on structural applications of FRP composites since almost 20 years, initially guided by Prof. em. René Suter and since 10 years by the author. Several R&D projects explore different possibilities...

Students' day enigma / snw (students' associations of material sciences of EPFL and ETHZ), given at their visit to the Smart Living Lab Fribourg

For the advancement of sustainable, cement-based construction of buildings, composite elements made of timber and wood-cement compound (WCCs) are developed at iTEC since 2012. Earlier research on recipe development, workability, mechanical properties and recyclability trough combustion of WCCs shows that this material is usable as construction mate...

Story-high, prefabricated concrete façade elements with 6-8 cm thick outer layers were frequently used in building construction in the 1960/70s. In current construction and rehabilitation, they are much thicker (12-15 cm) or economically non-competitive, due to significantly increased concrete cover or the required use of stainless steel reinforcem...

Cement-bonded wood products are used in construction since the beginning of the 20 th century. Until today, however, they are essentially applied as non-structural finishing layers, e.g. as support for stucco, as fire protection or acoustic insulation panels, providing good fire resistance, thermal and acoustic insulation properties with a relative...

Wood-cement compounds (WCCs) are composite materials made of wooden ag-gregates and mineral (cement) binders. These materials are widely used as prefabricated panels in the construction industry. A main obstacle for using casted WCC in construction elements is high shrinkage of the young product and frequently difficult workability of the mixes. Th...

Cement-bonded wood-based materials (Wood-Cement Compound: WCC) are used in construction since the beginning of the 20th century already. Until today, however, they are chiefly used as non-structural finishing layers where their good fire resistance, thermal and acoustic insulation properties are combined with a relatively low and thus, structurally...

Cement-bonded wood-based materials (wood-cement compounds, WCCs) are used in construction since more than 100 years. Until today, they are chiefly used non-structurally where their good fire resistance, thermal and acoustic insulation and thermal mass are combined with a relatively low density. Main application forms of WCCs are prefabricated panel...

Wood-cement compounds (WCCs) have been being used in construction since the beginning of the 20 th century, mostly as a secondary structure or finishing layers such as sound or thermal insulation elements. However, WCCs' stiffness and strength are rather low, therefore WCCs should be combined with timber or a similar lightweight structural material...

Timber construction has become more and more competitive by adapting efficient prefabricated construction methods and by recent changes in fire protection norms. Until recently, multy-story buildings had to contain an escape route built in non-combustible materials. Nowadays, the fire protection rules veer towards performance-oriented criteria, as...

The most widely used construction material is reinforced concrete which is heavy, has rather high embedded carbon, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building-physical properties. A high potential for a more sustainable development of building construction is located in timber-based compo...

Wood-cement compounds (WCCs) contain 30% to 40% combustible matter. Consequently, it is essential to determine if this kind of material is able to burn and produce energy as a way of recycling. Therefore, explorative combustibility tests were performed on three different WCCs. The ignition temperature is around 210°C, independently of the WCC recip...

The Chillon Viaduct, built by prestressed box girder segmental construction, was constructed in the late 1960s. Recent examination of structural performance showed that punching of wheel loads through the deck slab is prevailing, though structural safety requirements currently can be fulfilled. Furthermore, the box girder concrete is prone to alkal...

Recent examination of structural performance of the Chillon Viaduct in Switzerland built in 1969, showed that punching failure mode of the deck slab is prevailing, though structural safety requirements currently can be fulfilled. Since the concrete is prone to alkali aggregate reaction (AAR), the viaduct was strengthened by adding a layer of ultra-...

The roofing of an office building partially collapsed after being in use for almost twelve years. The author was appointed as an independent structural expert to investigate the damage event, by approval of all involved parties, i.e. owner, building insurer and roof constructor. The expert report should give answers to several questions related to...

Presentation @ autumn assembly of Union des Fabricants des Produits en Béton

1st Conference of COST Action FP1303 Performance of bio-based building materials

Accepted for publication

Discussion of full-scale tests on bridge deck slabs strengthened with UHPC for punching and flexure

The structural potential of applying glass fiber reinforced polymers (GFRP) as shear panels, i.e. slender structural elements loaded primarily in in-plane shear, is far from being exploited. Current design proposals only consider the resistance up to elastic buckling, leading to a relatively low economic competitiveness of such structural elements....

The structural performance of timber beams in bending could be considerably improved if the behavior of the flexural tension face were enhanced. This paper reports on an experimental and analytical study on the structural behavior of full-scale beams made of glued laminated timber, reinforced with flax fiber sheets. Two 5m-span beams were strengthe...

The potential of glass fibre reinforced polymers (GFRP) as structural shear panels, i.e. slender elements loaded primarily in in-plane shear, is far from being exploited. Current design proposals only consider the resistance up to elastic panel buckling, leading to a relatively low economic competitiveness of such structural elements. This paper re...

In today's building construction tenderings, ecological aspects are often taken into consideration. Therefore, it is of vital importance that all stakeholders – architects, structural engineers, owners, constructors etc. –, have an idea on the eco-balance of different construction methods, in order to choose the one being the most appropriate for t...

Construction and operation of buildings has an important environmental impact. The most widely used construction material is concrete; which is heavy, has rather high embedded energy, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building-physical properties with regard to thermal insulation and sto...

Check out the Extended Abstract available for download

Check out the Extended Abstract available for download

Check out the Extended Abstract available for download

Check out the Extended Abstract available for download

Check out the Extended Abstract available for download

Check out the Extended Abstract available for download

Applying simplified design code provisions for the shear assessment of existing concrete girders may result in unnecessary strengthening, justifying the effort to apply more refined approaches. Based on the cross-sectional analysis for continuous girder zones (B-regions), this paper discusses the theoretical influences of transverse reinforcement d...

Presentation @ atelier GiulianiHönger / FürstLaffranchi (visit to HEIA-FR)

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localizatio...

This paper reports on a new strengthening system for concrete elements, being composed of carbon-fiber reinforced polymer fabrics (CFRP fabrics) embedded in shotcrete. The strengthening system was evaluated in a test series on full-scale single span slab strips of 6 m length, on a non-strengthened reference specimen and two slab strips with differe...

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localizatio...

In the beginning of 2011, the Swiss Society of Engineers and Architects (SIA) edited the new code series SIA 269 for existing structures. The author of this paper was involved in the preparation of the sub-code SIA 269/2 treating concrete structures. A particular issue in the formulation of the provisions of this sub-code concerned the assessment o...

In new concrete structures, bond properties being influenced by construction details can easily be attained through suitable code requirements; in existing structures, however, such requirements may not be necessarily fulfilled. The new Swiss code SIA 269/2 (2011) for existing concrete structures therefore provides directives for the refined determ...

Composite materials are distinguished from other construction materials by their light weight and high resistance. The most common type of composites is glass fibre reinforced polymer (GFRP), due to the facility of element production in pultrusion and the competitive price of glass fibres. The potential of this quite new construction material is fa...

Tests on masonry walls strengthened with CFRP sheets for seismic action

This paper presents the results of tests conducted on glulam-concrete mixed structures with the goal to provide a plastic design method for multispan girders. Therefore, a new type of notch connectors has been developed. Compression tests on glulam timber samples have been conducted in order to develop a constitutive law considering the plastic beh...

The walkways between two wings of the College of Engineering and Architecture of Fribourg exhibit clearly perceptible vibrations, especially in the longitudinal direction, experienced by people on the walkway when other pedestrians cross. The dynamic behavior of these walkways was investigated in a Bachelor thesis, by step-wise refinement of theore...