A new R/D national program on timber structures in B.R.I, Japan -Research and development on hybrid timber structural system-

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1 A new R/D national program on timber structures in B.R.I, Japan -Research and development on hybrid timber structural system- Isoda, H 1 Okada,H 2 Kawai,N 3 Yamaguchi,N 4 ABSTRACT Timber is a traditional construction material that has relationship to our country s unique construction techniques and culture, but under the previous Building Standard Law, various specification codes have limited the scale of structures. However, a revision of the Building Standard Law in June 1998 with its prescriptions on performance codes has potential to accept large-scale and high-rise timber buildings. This research project develops following items by utilizing element of technologies including newly-developed engineered wood (industrialized timber structure materials such as glued laminated timber etc. 1) Hybrid timber members consisting of timber and other materials 2) High-performance joints to connect timber and other materials 3) Hybrid timber structures combining timber with other types of structures, such as reinforced concrete or steel frame. The results of this research will help promote building of houses with locally produced timber suited to the local climate, thus contributing to an improvement in regional identity and revitalization of the region. The results of this research will also help stem global warming, because the production minimizes emission of carbon dioxide and growing trees fix the amount of carbon dioxide in the atmosphere. INTRODUCTION In Japan timber structures have applied to low-rise and small-scale building such as a detached house. Recently engineered woods like a glued laminated timber with a big dimension spread and then big dome structures that represent large-scale building constructed. But those construction methods are unique, therefore due to peculiarity and high-cost it is difficult for those to spread generally. The objective of this project is to generalize middle-rise building, large-scale building made of timber. In order to put those buildings into practice, the following three items will be developed. 1) Develop high performance hybrid timber members consisting of timber and other materials 2) Develop high performance joints to connect timber members,and between timber and other materials 3) Develop hybrid timber structures incorporating timber with other types of structures such as reinforced concrete or steel frame. It is recognized that the results of this research will help promote building of houses with locally produced timber suited to the local climate, thus contributing to an improvement in regional identity and revitalization of the region. The results of this research will also help stem global warming, because the production minimizes emission of carbon dioxide and growing trees fix the amount of carbon dioxide in the atmosphere. 1 Senior Research Engineer, Structure Division, Building Research Institute, 1 Tatehara, Tsukuba, Ibaraki , Japan 2 Director, Dept. of Structural Engineering, Building Research Institute, 1 Tatehara, Tsukuba, Ibaraki , Japan 3 Head, Evaluation System Division, Building Research Institute, 1 Tatehara, Tsukuba, Ibaraki , Japan 4 Senior Research Engineer, Aerodynamics Division, Building Research Institute, 1 Tatehara, Tsukuba, Ibaraki , Japan

2 RESEARCH PLAN AND ORGANIZATION 2-1 Research Organization Organization of research program at the present is shown in table of 1. After discussing in this first fiscal year the restructuring suitable for research and development will be carried out. Placement of committee and sub-committee is as follows. The research committee is composed of members of experience or academic standing, structural engineer, and Ministry of Construction. This committee adjusts and unifies all research items of each sub-committee into theme of project. This committee can establish the technical committee that consists of knowledgeable people to summarize the opinion on the appropriate developmental policy. The sub-committees carry out concrete research and development on the hybrid timber buildings under the research committee. The working groups will be established in order to efficiently solve each item of research and development. The cooperative research promotion committee will be established in order to carry out promotion and adjustment of the cooperative research among the industry university government. In the first fiscal year, the research committee, the sub-committee on the member and joint, and on the structural system have been organized and discussed. The working groups under the subcommittees and the sub-committee for the fireproof will be organized in fiscal The sub-committee for construction may be added at the final stage when target members, joints and construction are decided. Table 1: Research organization

3 2 Research Plan and Outline The annual plan in the every fiscal year is shown at table of 2. In the first fiscal year several investigations have been carried out for confirming the realization and social standing of this project. Survey items and their outline are described in the following. The investigation of a demand for the wood-based middle-rise building For a local public body, the interests on utilizing wood-based material for buildings and demand of the timber middlerise and large-scale buildings for city hall, school building and so on. This investigation is useful to clarify social background and necessity of this project. The investigation of the current composed wood-based members, joints and structures The examples of hybrid timber members, joints and structures in Japan and oversea are collected, classified and arranged. This investigation is useful to grasp the current situation and to consider the new hybrid timber buildings. The investigation of oversea standards and codes For the following standards and codes, the text and provisions relating to hybrid timber members, joints and structures are collected, classified and arranged. Euro-code, UBC, BOCA, NBC, SBC, IBC, CSA, AS, NZS This investigation will be utilized for considering international harmonization of standards on hybrid timber buildings. The arrangement of Japanese Building Standard Law with its prescriptions performance codes for timber buildings Application range of the current regulation and reason of the regulation for the timber building are arranged. Especially, the fireproof is arranged, while referring to the movement of the performance-based code. This arrangement is utilized, when the reality of the development object is examined. 3. Final results 3.1 The outline of the final results of the sub-committee on the member and joint Development of the high-performance and high-reliable hybrid timber members and joints Development of the general evaluation and test procedure for hybrid timber members and joints 3.2 The outline of the final results of the sub-committee on the structural system Development of the rational and efficient hybrid timber structures. Timber hybrid structures mean, for example, the structure that consist of rational hybrid timber members and joints that will be developed in the sub-committee on member and joint, the structure combined reinforced concrete shear wall system and timber frame that resist only vertical load, and the structure combined steel rigid frame and timber frame. Development of the structural design method and performance evaluation procedure with the generality for hybrid timber structural system.

4 Table 2: Research plan ITEMS Development of hybrid timber members and joints 1) Investigations of current situation 2) Research of mechanical behavior 2-1) Tests for creep behavior ) Tests for mechanical behavior 2-3) Evaluation of mechanical behavior 3) Development and Analyses 3-1) Proposal of the basic concept 3-2) Design of practical members and joints 3-3) Tests and analyses for performance evaluation 4) Research of fireproof performance 4-1) Specification of required performance 4-2) Performance evaluation of developed members and joints 5) Proposal of design method 5-1) Making basic concept 5-2) Proposal of design method Development of hybrid timber 1) Investigations of current situation 2) Decision of target structural 2-1) Enumeration of hybrid structural 2-2) Case study for enumerated 2-3) Decision of target structural 3) Development and Analyses 3-1) Basic analysis for case study 3-2) Basic tests for case study 3-3) Real scale test for target 4) Research of fireproof performance 4-1) Specification of required performance 4-2) Performance evaluation of developed members and joints 5)Proposal of design method 5-1) Making basic concept 5-2) Proposal of design method

5 CURRENT ACTIVITIES 1 Sub-committee on members and joint In the first fiscal year the main theme of this sub-committee is to know the current hybrid timber members and joints. And then performance evaluation method, experimental specification and so on for typical hybrid timber members and joints will be examined. Figure 2 shows the example of hybrid timber material. In addition to this feasibility studies creep tests for control specimens have started. Metal Glulam Lam inated Timber Bolts Glulam Lam inated Tim ber Bolts Reinforcement (CFRP, Metal, etc) Hybrid Timber Members Figure 2: Image of Hybrid Timber Members 2 Sub-committee on structural system The for case study discussed in the sub-committee are the followings 1) The structure that consists of hybrid timber members and joints developed by the sub-committee on member and joint. 2) The structure that consists of reinforced concrete sheer wall or rigid frame and timber frame that dose not resist shear load 3) The structure that consists of steel rigid frame and timber frame resisting shear load 4) The structure that consists of reinforced concrete or steel structure at the low stories and timber structure 5) The structure that consists of the external reinforced concrete or steel super structure and the internal timber frame 6) The structure that consists of beams and columns made of reinforced concrete or steel and timber floor and wall system 7) The structure that consists of timber structure except reinforced concrete or steel column

6 Figure 3: Concept of hybrid Timber Structure The samples of are shown in figure of 3. In addition to this discussion research items of hybrid have been discussed. The research items and the outline of results are shown the following. In the future, analysis and tests for the above case study structures will be conducted 1) The floor system Th evaluation procedure for timber floor is proposed The illustration of sound insulation countermeasure method is shown The problem for deformation and deflection of floor is arranged The illustration of control method for deformation and deflection is shown The limit value that the rigid floor can be assumed is shown The analysis method, evaluation procedure, evaluation example and the problem of flexible floor is shown 2) The joint of timber frame to other structure In the sub-committee on structural system the research for joint examine only for beam-column joint. Thus the connections of timber to reinforced concrete and of timber to steel are handled. The outline of the results is that the detail of rigid joint, semi-rigid joint and pin joint will be shown. As for semi-rigid joint the performance of mechanical behavior and performance evaluation procedure will be shown. The mechanical performance means stiffness, yield point maximum strength, energy absorption performance and so on. In other words, they mean load-deformation relationship and restoring force characteristics. Additionally the mechanical behavior changing the load velocity speed will be handed. 3) The hybrid system The evaluation method for hybrid system is proposed. This method is based on theory of probability and includes fracture mode control. The evaluation procedure of the damping for hybrid system is proposed. It means the evaluation of timber damping and added timber damping in other structural system. The methods of the deformation adaptation for long-term load and drying contraction are proposed. The part replacement considering its service life are proposed.

7 CONCLUSIONS The building Research Institute, Ministry of Construction, Japan initiated a research and development program on hybrid timber structural system in 1999 as a five-year project. This paper described the organization, and the research items and plans. This research and development project aims to construct middle-rise and large-scale timber structure in general. The results of this research will also help stem global warming, because the production minimizes emission of carbon dioxide and growing trees fix the amount of carbon dioxide in the atmosphere. ACKNOWLEDGEMENT This work has been carried out under the development project on hybrid timber structural. The authors would like to acknowledge Prof. I. Sakamoto chairperson of committee and sub-committee on the structural system, Prof. Y. Hirashima, chairperson of sub-committee on member and joint and all members of the project for their useful advice and suggestions.