245-RTE: Reinforcement of Timber Elements in Existing Structures

Organizers / Managers

Technical Committee 245-RTE

General Information

Chair: Dr. Jorge BRANCO
Deputy Chair: Dr. Philipp DIETSCH
Activity starting in: 2011
Activity ending in: 2019
Cluster E

Subject matter

The last decades were marked by a significant widening in the range of structural application of timber. There is, however, a growing need for the maintenance and upgrading of existing buildings for economic, environmental, historical and social concerns. Worldwide, a large proportion of the existing building stock is more than 50 years old; many of these buildings need to be adapted for more sophisticated present and future requirements. The need for structural reinforcement of timber buildings may become necessary from motivations such as change of use, changes in regulatory specifications, interventions to increase seismic resistance, deterioration due to poor maintenance, or exceptional damaging incidents.

Recent developments related to structural reinforcement can be grouped into three categories:
(i) addition of new structural systems to support the existing structure;
(ii) configuration of a composite system; and
(iii) incorporation of elements to increase strength and stiffness.

In the latter category, the options range from mechanical fasteners like glued-in rods and self-tapping screws, adhesive systems, steel straps and plates, ever more widely fibre-reinforced polymers, and most recently nanotechnology. These methodologies, however, are often not adapted for their use in-situ nor depending on whether the structure is part of the regular building stock or belongs to cultural heritage.

The objectives of the proposed RILEM TC are:
• To improve the reinforcement practice timber structural elements;
• To disseminate up-to-date results to the industry, policy makers and society;
• To optimise collaboration of involved stakeholders in research and industry.

Terms of reference

The TC will focus on structural applications of timber in existing buildings of all ages and uses; other materials, non-structural timber applications, and product development are excluded.
• The scientific focus of this TC is the improvement of existing techniques for reliable reinforcement of structural timber; the development of new methods is not anticipated.
• The proposed membership will include leading experts in the field. Collaboration between the industry members, practitioners and academia is anticipated. It is expected that such collaboration will result in joint workshops, case studies and active participation in conferences.
• The proposed membership has on-going research programs in the area and the TC will facilitate stronger research coordination, eliminate duplication and permit faster dissemination of new methods.
• The expected timeframe for the proposed TC to reach the above goals is 5 years. Yearly evaluation of progress will take place at the TC annual meetings. It is anticipated that this TC may generate potential new TCs related to timber since it is becoming a more important structural material due to its renewability and the continuing aging of existing timber structures.

Detailed working programme

The scientific focus of this TC is the improvement of existing techniques for the reinforcement of structural timber. Activities will focus on consolidating current knowledge and answering the following questions:
• What is the current state of the art regarding methods and techniques?
• What techniques and methods from other materials and systems can be adapted to timber structures?
• Where is coordinated research required to develop new techniques and methods?

The scientific activities range from experimental to numerical and analytical approaches to study technologies for in-situ strengthening of wood structural members and will contain following tasks:
• Analysing approaches of different research groups and evaluating methods in terms of applicability, expenditure of time/cost, validity of results and constraints;
• Facilitating the decision-making process for choosing an appropriate reinforcement method with consideration of cultural heritage aspects;
• Creating practical tools with an immediate applicability in the construction sector;
• Establishing common practices and harmonized recommendations and disseminating thereof.

Research on the following reinforcement systems will be evaluated:
• Timber and timber based products (e.g. densified and cross-laminated timber)
• Composite system (e.g. timber-concrete, or timber-steel and timber-timber)
• Adhesive systems (considering on-site application and durability issues)
• Mechanical fasteners (e.g. glued-in or pre-drilled and screwed-in rods or self-tapping screws)
• Fibre reinforced polymers and natural fibres also applied in combination with adhesives
• Nanotechnology (e.g. carbon nanotubes with polymeric resins)

The following operative milestones are proposed to be scheduled:
• MS1 - Initial committee meeting: Allocation of tasks, summarising existing and planned national research, identifying research needs, coordination of joint research activities (2012)
• MS2 - Development of State-of-the-art report (2013)
• MS3 - Workshop on state-of-the-art reinforcement methods (2014)
• MS4 - Development of harmonized guidelines (2015)
• MS5 - Workshop on harmonized guidelines (2016)

Technical environment

Research on timber structural elements has been coordinated by the COST Action E55 “Performance of Timber Structures” and RILEM TC AST-215 “In-situ assessment of structural timber”. Valuable information in form of a State-of-the-Art report and a guideline on the assessment of timber structures was provided. The proposed RILEM TC will build on these findings, target existing shortcomings in regard to reinforcements, benefit from multidisciplinary views and innovative solutions by the involved stakeholders, enable synergies between them, and provide an effective way of discussing and disseminating results from on-going projects.

The reinforcement of timber is an active research domain: COST Action FP1004 “Enhance mechanical properties of timber” deals with techniques to develop innovative reinforcing techniques for timber products targeting large structures and COST Action FP1101 “Assessment, Reinforcement and Monitoring of Timber Structures“ deals with the on-site application of reinforcement methods in existing structures; typically smaller and mainstream buildings which constitute the largest proportion of the existing building stock.

It is foreseen to establish a liaison between the proposed RILEM TC and these two COST Actions and foster the exchange of knowledge through joint activities. These interactions can be in the form of co-organising conferences, and joint meetings and workshops. Several of the proposed experts are involved in these COST Actions or other research programmes and will facilitate collaboration. The TC will also liaise with general engineering societies and forest product specific societies. Reinforcement techniques are also used in other materials such as concrete or masonry. Some of the techniques are equally applicable to several materials, therefore collaboration between the pertinent RILEM TCs from all material domains is valuable and members of the corresponding TCs will be invited to participate in the activities of the proposed TC.

Expected achievements

Knowledge and harmonized methods, approaches and technologies that enhance the reliable reinforcement of timber structural elements will be developed and disseminated. To be successful, the stakeholders need good knowledge of what can be achieved and realised with reinforcement solutions and also guidelines for handling and implementing these in a professional way. Following achievements are expected:
• The TC will create a basis for exchange of ideas and research data, and a database of case studies;
• The TC will provide information on its website and write joint articles for peer reviewed journals;
• The TC will write a state-of-the art report;
• The TC will propose harmonised recommendations;
• The TC will provide training to young researchers and practitioners through two international workshops, possibly in cooperation with COST;
• The TC will organize special sessions on reinforcement of structural timber at international events, e.g. the World Conferences in Timber Engineering;
• The TC will attempt to develop collaborative research proposals that will be submitted to national and international national funding agencies.

Group of users

The target groups and end users of the Action are all involved stakeholders:
• Representatives of the timber construction and building industry (architects and engineers);
• Product developers in the sector of reinforcement technologies;
• Authorities and companies related with the conservation of building heritage;
• Policy makers at national and international levels;
• Research community, relevant standardization bodies and code writers;
• Lecturers and students of structural design at engineering and architectural schools.

Specific use of the results

The results will be used in and have an impact on:
• The comprehensive in-situ reinforcement of timber members in existing structures;
• The planning of reinforcement methods in weak zones of timber structural elements;
• The decision-making process in the restoration of historic structures;
• The costs of restoration and rehabilitation measures;
• Acceptance and safety of existing timber structures.

This TC will create scientific, technological, economic and social benefits. Improving the reinforcement of timber structural elements is a research domain with large-scale activity which requires the exchange of information and identification of new research ideas (scientific benefit). Increased knowledge of retrofitting techniques will help architects and engineers to make timber a viable option for more applications and new opportunities in design (technological and economic benefits). Reliably reinforcing timber structures, avoids failures and unnecessary decommissioning, and leads to safer structures and better use of resources (social and economic benefits). Using the genuinely renewable construction material timber and replacing non-renewable materials will increase economic incentives for sustainable forestry (environmental benefit).