This guide is a review of the most recent European results from reports which shared experience and knowledge on how to introduce circularity in procurement documents. It also contains the authors’ own conclusions and proposes a business model and a list of possible requirements that could be introduced in procurements by municipalities.

It refers to the definition of circular building, to the principles behind it. It shows how to use the valuable experience of sustainability and how to pass from a sustainable procurement (Green public procurement) to circular procurement.

The guide is meant to be a reference, a supporting document for public decisions-makers when choosing criteria for procurement document of new constructions.

This work proposes a multi-Fickian method to analyse the hygro-thermal behaviour of timber bridge elements under Northern Europe climates. A temperature-dependent wood hysteresis is included in the model and the thermal effects due to temperatures above and below zero are taken into account. As a case study, the model is used for the hygro-thermal simulation of a glulam beam of Älsvbacka bridge in North of Sweden that was monitored by using wireless sensors in a previous study. The model, implemented in Abaqus FEM code, is able to predict the states of moisture and temperature in protected parts of the beam by using as external loads the relative humidity and temperature of the air provided by in-situ measurements. Furthermore a simplified model using a wood hysteresis independent of temperature is found to provide similar results and appears easier to implement in finite element codes.

This work presents a numerical model to analyse the hygro-thermal behaviour of wooden bridge members. A multi-Fickian hygro-thermal model, previously implemented by some of the authors, is extended by including the dependency of wood sorption on temperature above and below zero degrees Celsius to predict moisture, temperature and relative humidity in wood under Northern European climates. The performance of the model in the presence of protective paints is particularly investigated. The finite element analysis based on the proposed model simulates the hygro-thermal behaviour of a glue-laminated beam of Älsvbacka Bridge located in Skellefteå (North of Sweden). The beam, coated by paints and claddings, was monitored by using wireless sensors in a previous research. Comparisons with the available measurements reveal that the numerical model is able to predict the moisture content in locations sheltered from rain and sun with moisture levels below the fibre saturation point. A study of the influence of different protective paints shows that the maximum and minimum moisture content at various depths along horizontal paths of the beam cross section, as well as the moisture gradients in different seasonal periods, are strongly affected by the type of paint. The proposed numerical approach is a promising tool to facilitate sensor-based monitoring techniques and to optimize the choice of protective paints for improved performance of timber bridges and other wooden structures under variable climates.

Durability is essential for outdoor structures to minimize life cycle costs. Timber beams and columns can get decay and cracks due to dimensional changes through shrinking and swelling by moisture changes during exposure. Cracks can lead water into wood and thereby increase the risk for decay and reduce strength and service life. This project deals with the assessment and prediction of development for timber structures with cracks. More than 100 test specimens are included in an outdoor test, glulam beams and columns made of Scots pine (Pinus Silvestris) or Norway spruce (Picea abies). Most specimens are placed in the north of Sweden, but also some in the southwest of Sweden. The project started during 2007. The beams and columns are measured regularly concerning cracks and surface treatment, moisture content and modulus of elasticity on-site. Weather is measured. This paper describes tests and measurements and reports some initial results. The results so far show that cracks develop for every year. Some beams, preferable the oil treated ones, have already after three years lots of cracks while some of the painted are rather intact. The moisture content and modulus of elasticity is relatively unchanged. The research will continue.

Conference proceedings from the conference ICTB 2017, the 3rd International Conference on Timber Bridges, 26-29 June 2017 in Skellefteå, Sweden. Content of the conference is presented in the Conference programme included in these proceedings on pages 3-10.  Papers presented at the conference were distributed on USB to participants at the conference.

The conference contained 5 Keynote presentations and 45 Technical papers presented in 10 sessions, and also a technical visit to wooden buildings and bridges in Skellefteå.

A pre-tour included visit to several timber bridges between Skellefteå and Umeå, and the pretour programme is included in these proceedings on pages 11-15.

The aim of this work was to present a solution of design, manufacture and assemble prefabricated infill walls with good quality. The rapport is based on information from Holland. The aim is that designers, manufacturers and contractors and others must have a working basis for how to build and design infill walls with high prefabrication grade in a efficient and quality controlled process. The report also deals with aspects of the wall function and practical observations that are important to consider.

The design of details is an important aspect in durability design of rain-exposed timber structures. Joints are considered the weak-points of these structures as they accumulate moisture and facilitate deterioration by decay. The present study aims to study the influence of detail design, and its effect on the service life, by estimating the decay rate in a number of rain-exposed timber components and joints, typically found in timber bridges. A test-setup was exposed outdoors over a period of one year while the moisture content was measured in specific measuring points. The test-setup included groups of beams, columns and joints commonly found in timberbridges. For the beams and columns, the effectiveness of typical protective measures was also tested. The annual decay rate was estimated using two different decay prediction models. Compared to a reference beam, the results show that structural protection reduced the risk of decay while joints and end-grain tended to be at increased risk. The lowest service life, estimated to 3-4 years, was found close to end-grain where drying was hindered but moisture could accumulate. In general, the discrepancy between the two decay models was large for low to medium exposure and decreased with increasing exposure.

Moisture safety of tall timber facades

The main purpose of the project was to facilitate safe design of sustainable and cost-effective solutions for wood facades of high-rise buildings. Studies have been carried out of different designs of the wall itself and of different details in the wall. Direct and indirect consequences of moisture damage have been considered but mainly risk of mould or decay. Façade details with high risk were identified e.g. window and balcony, and the types of damage that may occur, and what the consequences may be. Based on this, some damage scenarios were selected where detailed solutions were analysed more carefully. Details were also compared with modified designs with improvements such as addition of a sealing strip or plate covering. LCA and LCC have been calculated for some damage scenarios to show consequences of damages and the importance of well-executed designs and details.

The use of timber structures in tall buildings increases the demand of moisture safety in facades. Moisture in the facade could result in unwanted consequences such as mold, decay and distortions in wood materials. This might have impact on the indoor climate and the building quality. The aim of this study was to evaluate the moisture safety regarding the composition of the façade and connection details such as windows and balconies. Scenarios with possible damages were evaluated with LCC (Life Cycle Cost) and LCA (Life Cycle Assessment). The scenarios were developed based on experiences from manufacturers and insurance companies and on research investigations of damages. LCC and LCA includes replacement of damaged building materials, transports of new materials and damaged materials for recycling or energy recovery and the use of energy for drying of moisture in the structure. Both light frame structures and CLT (Cross Laminated Timber) structures were included. Improvements of detail connections to increase moisture safety were also evaluated regarding risk of damage, costs and environmental impact. The results show that even small and inexpensive improvements will increase the moisture safety and significantly reduce the risk of damage.

The hypothesis is that a good cladding system in wood should be characterized by a homogeneous dimensional behaviour with minimal variation between individual panel boards to minimize maintenance, i.e. repainting or, in the worst case, replacement of whole panels. Four different types of cladding panels were tested: a regular spruce panel, a quality-sorted P-marked spruce panel, a regular panel of pine heartwood and a spruce glulam panel, 50 panels of each type. The objective was to study the dimensional changes under changing moisture conditions in order to find the cladding material with the smallest possible dimensional and distortion movements. The shape stability of the panels was measured and expressed in terms of bow, spring, twist and cupping. The spruce glulam panels showed the best shape stability, proven significantly different in comparison to the other two spruce panel systems. Panels of pine heartwood showed a tendency greater dimensional stability than the spruce panels, but not enough to be considered statistically significantly different in this study.

The construction sector faces the challenge of mitigating climate change with urgency. Life cycle assessment (LCA), a widely used tool to assess the climate impacts of buildings, is seldom used for bridges. Material-specific phenomena such as concrete carbonation and biogenic carbon storage are usually unaccounted for when assessing the climate impacts from infrastructure. The purpose of this article is to explore the effects these phenomena could have on climate impact assessment of road bridges and comparisons between bridge designs. For this, a case study is used of two functionally equivalent design alternatives for a small road bridge in Sweden. Dynamic LCA is used to calculate the effects of biogenic carbon storage, while the Lagerblad method and literature values are used to estimate concrete carbonation. The results show that the climate impact of the bridge is influenced by both phenomena, and that the gap between the impacts from both designs increases if the phenomena are accounted for. The outcome is influenced by the time occurrence assumed for the forest carbon uptake and the end-of-life scenario for the concrete. An equilibrium or 50/50 approach for accounting for the forest carbon uptake is proposed as a middle value compromise to handle this issue. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Buller är störande, oönskat ljud från t ex trafik. För att minska spridningen av trafikbuller kan bullerskärmar sättas upp längs vägen. De kan lämpligen utföras av trä, som är ett lätt, starkt och formbart material. Bullerskärmar av trä kan anpassas till de flesta miljöer, och träbyggande har en tradition i det svenska landskapet. Trä är också ett material som de flesta uppskattar i sin närmiljö. Bullerskärmar av trä kan utformas så att de får god funktion, lång hållbarhet och blir lätta att underhålla.

This report presents a result of the work in the part project "Long span timber bridges" in the frame of the Nordic Timber Bridge Project. Mainly the cable stayed bridge has been investigated.

Timber bridges can be designed with advanced computer models, but to get reliable results from for example a finite element analysis it is very important to have correct input values. At design of timber bridges it can be hard to know which desgn values for the material properties to use, as wood is a material with many variable properties and qualities. This report is part of the Nordic Wood Project "Timber Bridges, part 3".

Snedstagsbroar har utvecklats sedan andra världskriget. De kan utformas på många olika sätt, med olika antal och anordning av stagen. Utformningen av stagsystemet bestämmer broarnas egenskaper. Utvecklingen har gått från få till många stag, och brodäcken blir då i huvudsak en tryckt konstruktionsdel eftersom längsböjningen blir liten. Tvärböjningen kan dimensionera brodäcken vid breda broar. Snedstagsbroarna är stabilare än hängbroar, eftersom stagen har olika längder och därmed får olika egenfrekvenser och dämpning. De är därför inte lika vindkänsliga som hängbroar, och kravet på aerodynamiskt urformade brodäck är inte lika stort.

Ett växande marknadssegment, som passar för träbroar, är gång- och cykelbroar som korsar stora vägar t ex motorvägar, samt järnvägar och vattendrag. Dessa broar kräver ofta långa spännvidder och stora vertikala öppningar under broarna. Hängbroar och snedstagsbroar är många gånger attraktiva alternativ, eftersom fackverks- och bågbroar inte alltid kan användas. Häng- och snedstagsbroar är slanka konstruktioner som är känsliga för svängningar som orsakas av vind och trafik.

Bearing capacity for timber parts with cracks Timber parts with cracks can be found now and then at the inspections of timber bridges. The question is how the bearing capacity should be calculated and judged for these parts, as well as how the cracks will develop under different circumstances. Cracks are a consequence of varying moisture content in the wood, and occur most often when the wood is exposed to sun and rainfall. The bearing capacity of timber is usually not directly affected by small cracks. The cracks have primarily influence on the moisture intrusion in the wood, which in course of time can affect durability and bearing capacity. The resistance of joints in timber structures can also be influenced by cracks in the wood. Structural parts in timber bridges can be protected against direct sunshine and rain by coverings, but in some bridges the wood is protected with surface treatment. Glulam structures with surface treatments that are exposed to weather often receive cracks on the surface, usually close to the glue lines. The cracks make the treatment less tight, which opens the way for water and fungi. A tight treatment makes it difficult for moistture in the wood to dry, and the influence of different treatments on the development of cracks and durability should also be investigated. The aim of this pilot project is to study the crack formation in timber parts and influencing factors in order to decide the bearing capacity and durability. The project work consists of a literature study, calculations, tests and evaluations of some beams. The result from the study will be presented in a report. The ambition is to form the basis for a continued more comprehensive research project.

Denna handbok visar hur trä kan användas för att bygga hållbara väg-, gång- och cykelbroar. Träbroar har flera fördelar. De kan prefabriceras, är lätta att transportera och går snabbt att bygga. Tekniken att bygga träbroar har utvecklats mycket under de senaste åren. Boken ger exempel på hur man kan konstruera och dimensionera träbroar på ett hållbart sätt, som minimerar underhållet och ger lång livslängd. Den är ett hjälpmedel och en inspirationskälla i första hand för yrkesverksamma konstruktörer och projektörer, men vänder sig också till beställare, entreprenörer och studerande vid tekniska universitet och högskolor.

This report has been prepared within the project DuraTB - Durable Timber Bridges. The

goal of the project is to develop sustainable timber bridges by developing guidelines for

moisture design and developing new and improved bridges and bridge details. This report

describes the results from a subproject with the participation of SP Technical Research

Institute of Sweden, Martinsons Byggsystem AB, Moelven Töreboda AB and the

Swedish Transport Administration. Also waterproofing contractors and entrepreneurs

participated in the work. The purpose of the subproject was to investigate primers and

waterproofing and to improve the edge details of Swedish timber bridges with stresslaminated

decks made of spruce. This report contains a summary of follow-up of

blistering on wooden decks, tests of bitumen primers with regard to adhesion and water

resistance and tests of new edge solutions for wooden bridges.

A review of inspection results from more than one hundred inspected Swedish timber

bridges with asphalt pavement on stress-laminated decks showed that about 30 % had

some remarks about the pavement. The most common damages were cracks especially at

deck ends in connection to abutments. Bridges with blisters at the time of inspection were

few. Laboratory tests of adhesion were carried out which showed that the primer can

contribute to the adhesion of the waterproofing bitumen sheet to the wood, although both

tensile and tear tests gave large variations in the results so it is difficult to draw firm

conclusions. The tests showed that both water-based and solvent-based primer can be

used. Timber bridge manufacturers want to use the more environmentally friendly waterbased

primer in the factory and the more weather resistant and quick drying solvent-based

at the building site. The tests showed, however, also some adhesion of waterproofing

sheets to a wood surface without primer, even to a damp or dirty surface. Testing of water

resistance of primer on wood surfaces showed that the primer provides some moisture

protection which is favorable for the wood. The penetration of moisture was less than for

untreated wood, but the primer was not completely waterproof. An untreated moist wood

surface, however, dried out relatively quickly. At the testing of edge details with

installations of edge steel angels on wooden deck specimens, the steel angels showed a

tendency to deform under the effect of heat from welding of the waterproofing bitumen

sheet. To get a robust solution with little deformation also mechanical fixings to the wood

deck was tested and is recommended.

Several parties are involved in the construction process, so there is a need for detailed

descriptions for the work. This subproject has contributed to some new sections in the

Swedish AMA (General material and work descriptions) used by the construction

industry, to improve the information about timber bridges and assist the construction of

durable timber bridges.

Many modern timber bridges have been built in Sweden during the last ten years. This report is about Swedish timber bridges and methods for the inspection of the bridges. It also includes reports from some inspections of timber bridges. The relatively new timber bridges are in good condition. The most frequent problems and corrective actions regarding the bridges have been related to railings, surface treatments and connections. At close inspections of some timber bridges no serious damages were found that will reduce the performance during the next ten years. Timber bridge design has been improved throughout the years, and some of the defects found depended on shortcomings in details in the early bridges. Several bridges were not sufficiently maintained. Periodic cleaning is important for keeping the wood clean and dry to ensure a long life of the bridges. Defects of the inspected bridges were mainly related to cracks and delaminations, surface treatments, moisture contents, steel coatings, connections, pre-stressed steel bars, connections to abutments and pavings. The principally used field measuring method is the resistive moisture meter, as moisture is the most critical parameter for the decay of wood. The resistive moisture meter has good accuracy and is almost non-destructive, as the electrodes only cause small holes in the wood. Rot on the outside of beams can be found with a knife and on the inside with a drill. Less destructive methods for rot surveys are the Pilodyn for outer rot and Resistograph for inner rot, but they sometimes give measures that can be hard to interpret as wood is an inhomogeneous material with large natural variations. Key words: timber bridge, inspection, wood moisture meter, Pilodyn, Resisiograph

Undersökningar på platser där man haft jordbävningar visar att trähus ofta klarat sig bra. Trähusen har flera fördelar, genom att trämaterialet är lätt i förhållande till sin styrka och har hög hållfasthet vid korttidslast. Trähus består också ofta av många konstruktionsdlear som är hopsatta med skruv- eller spikförband, vilket gör byggnaderna flexibla och energiabsorberande. Trähus passar därför bra i jordbävningsdrabbade regioner.

Denna rapport innehåller anvisningar för inspektion av träbroar. Rapporten är en svensk bearbetning av rapporten "Inspection of Timber Bridges" från Nordic Wood-projektet "Broar av trä". I Sverige har under de senaste 10 åren byggts nästan 500 nya träbroar. Rapporten har tagits fram för att ge inspekörer av träbroar ett stöd, samt kännedom om vilka hjälpmedel som finns till hands vid inspektion av träbroar. I rapporten har inte tagits ställning till hur ofta en inspektion av en träbro bör utföras, eller hur omfattande den bör vara.

Stress-laminated bridge decks in Sweden are usually made of glulam beams of spruce and it is therefore crucial to avoid moisture as the wood has no impregnation that can protect it from decay. Typically the protection of the deck consists of a waterproof bitumen sheet under the asphalt layers on the top surface and of claddings along the edges. The aim of this work was to study the risk of damages and how to ensure the function of the deck plates. The adhesion of bitumen sheets and the effect of different primers was studied. The design at the edges was studied and an improved solution with a steel angle along the deck edge was developed and tested. The improved design should be robust and easy to install to always assure a correct performance. The new design has been developed within the European research project DuraTB - Durable Timber Bridges and is now included in general recommendations for timber bridges in Sweden.

This is the final report from the project DuraTB - Durable Timber Bridges. The goal of the project was to contribute to the development of sustainable timber bridges by making guidelines for moisture design and developing new and improved bridge concepts and details in terms of durability and maintenance aspects.

In this report the analyzes, surveys, results and guidelines are described. More detailed descriptions are referred to the many publications that the project has delivered.

The research leading to these results has received funding from the WoddWisdom-Net Research Programme which is a transnational R&D programme jointly funded by national funding organisations within the framework of the ERA-NET WoodWisdom-Net 2.