Mamoru Iwata

Passive damping technology for buildings in Japan

This paper first reviews the concept of the damage-controlled structure (DCS) which is a kind of passive damping technology, proposed before the Hyogoken-Nanbu Earthquake in Japan and the Northridge Earthquake in the USA. The philosophy, the necessity and the potential of the damage-controlled structure are stated in the first two sections of this paper. Second, a modified shear-bending beam model and a rational dynamic analysis method of three-dimensional frame for the damage-controlled structure with passive energy dissipation devices are reviewed. Thirdly, a series of dynamic loading test results of modeled damage-controlled steel frame with hysteretic dampers are presented. Finally, a number of actual example building projects which exemplify the current seismic design trend using the passive damping technology in Japan are reviewed.

Reuse Dismantling and Performance Evaluation of Reusable Members

The reuse system mentioned in this paper is an overall system for realizing a reuse business in a cyclic process of design, fabrication, construction, maintenance, dismantling, and storage. Here, we propose reuse dismantling to minimize the damage to structural members for future reuse, and performance evaluation of reusable members focusing on rolled H-sections. Structural members obtained by reuse dismantling or conventional demolition are evaluated by visual inspection, dimensional inspection, mechanical property tests, chemical component tests, and degradation inspection. For structural members to circulate as reusable members in the existing distribution system, two industries are needed: one responsible for production and product supply, which has already been established, and the other facilitating disposal, recycling, and reusing of the products resulting from the former. The authors define the former as the arterial industry, and the latter, as the venous industry, showing the size and importance of both industries.

Bending Test of the Composite Steel-Timber Beam

In the field of building construction, mass consumption of wood materials contributes to reforestation and becomes the environmental burden reduction. However, an application to conventional timber structures only such as house has a quantitative limit. A newly developed timber structure that is able to make a large-scale building is expected. A composite steel-timber structure will be one of the effective methods to expand the structural variations. In this paper, the bending test of composite steel-timber beam classified typical joint methods is conducted to grasp basic structural performance.

The System Truss as a Building System

A space structure means a structure, such as a space truss, suspended structure, or air supported structure. The space truss is a suitable system for industrial use or constructing systematized structure because it can be divided into simple components. Modern technology has made dramatic progress in the past decade, but the advanced technologies have not yet had a strong impact on architecture. The aim of this paper is to prove that the space truss can be both systematized and industrialized through the use of such advanced technologies as C.I.M. (Computer Integrated Manufacturing), and that the system truss (systematized space truss) will be able to provide infinite possibilities for, architects to create space structures.

Verification of Clearance and Gap for Fabricating the Buckling-Restrained Brace Using Steel Mortar Planks

The buckling-restrained brace must be able to provide the designed structural performance in actual use. In other words, the buckling-restrained brace must retain its initial quality in during the fabricating process. In this study, for the purpose of ensuring the initial quality of the buckling-restrained brace using steel mortar planks (BRBSM), quality control values at the time of fabrication are set and conduct verification testing on clearance and gap.

Performance Evaluation of Buckling-Restrained Braces Installed in a Mid-Rise Steel Structure

The authors have continuously studied buckling-restrained braces using steel mortar planks (BRBSM). The performance of energy absorption and fatigue against cyclic loading has been evaluated. Although past studies have clarified the structural performance of BRBSM as single member, it is necessary to study not only the performance of BRBSM as single member but also the performance of BRBSM installed in a building structure. In this paper, a frame model of mid-rise steel structure with BRBSM subjected to earthquake motions with various characteristics is analyzed. Comparing the results of the analysis and the past tests, the seismic behavior of a structure is discussed. Especially, the seismic performance of BRBSM installed in the building structure is evaluated. In addition, the seismic performance of two types of BRBSM; basic and developed high-performance types, is compared and evaluated about cumulative plastic strain energy ratio and cumulative fatigue. As a result, the performance capacities of the both types of BRBSM exceed the required values of BRBSM under severe earthquake motions about cumulative plastic strain energy ratio and cumulative fatigue. The basic-type BRBSM has the fatigue capacity against 2 to 5 times severe earthquake motions. The required values of high-performance-type BRBSM are about a half of accumulated fatigue capacity compared with the basic-type one. The high-performance-type BRBSM is applicable against quite many cyclic loadings of low strain amplitude, and able to be used for long-term service.

Simulation study on energy conservation performance for integrated external louver facades

The authors previously proposed integrated-facade-systems comprising different types of external louvers integrated with buckling restraint braces. The systems can be applied to both new and existing buildings, paying attention to the building’s appearance, upgraded structural performance and indoor environment. The authors have studied indoor daylight conditions with louver facades and a research paper was published in this journal (Misawa, Hikone, Nakamura, Iwamoto, Iwata, 2014). This research study reports on the energy conservation performance of louver facades and proposes an External Shading Coefficient (ESC) for external louver systems. Situations with five external louver facades and no louvers, facing three facade orientations (East, South and West) are examined. The year-round ESC is simulated every hour using Radiance software for transient solar radiation calculations. Furthermore, by using the proposed ESC, case studies for typical Japanese offices are carried out to verify reduction effects on the annual thermal load and electrical energy consumption of an air source heat pump for each louver set-up. Simulation results are calculated in hourly increments using TRNSYS software; the results show that both thermal loads and electrical energy consumption are reduced regardless of louver types and facade orientations when integrated external louver facades are installed.

CO2 Fixation Using a Composite Steel Timber Structure

One approach to promote forest growth is the pruning and thinning of trees. In the field of building structure, it is necessary to use thinned woods as timber positively. However, timber is too weak to apply to the large-scale buildings. Research and development of a building system to use timber are demanded. Authors propose composite steel-timber structure aiming to spread wood to building construction field considering the global environment. First, distribution volumes of planted forest of each age forest class in Japan and its CO2 fixation are shown, investigating forest resources. Finally, the specific example of a composite steel-timber structure is shown and CO2 fixation at building structure model using a composite steel-timber structure is estimated.

A PROPOSAL OF FACADE PANEL SYSTEM SUITABLE FOR THE SUSTAINABLE BUILDING STRUCTURE SYSTEM

To reduce the global environment load, a sustainable building structure system (SBS), which is one of the damage control structures, has been researched and developed. However it is difficult for this system to apply conventional facade panels in case of a huge earthquake. In this study, the authors propose a new facade panel system that suits to large story deformation angle of the SBS. Basic performance of the proposed system is confirmed by experiments using scale-down model that have rotational pin and slipping connections.

EXPERIMENTAL STUDY ON BUCKLING RESTRAINED BRACES USING STEEL MORTAR PLANKS WITH INITIAL IMPERFECTIONS

This paper describes static cyclic loading tests of buckling restrained braces using steel mortar planks with initial imperfections. Experimental parameters are initial deflection of core plates due to uneven of mortar face and direction of core plates. Tests are conducted by applying increasing loads alternately in positive and negative directions. As results, the energy absorption capacity of specimens with initial imperfection is lower than that without initial imperfection; however, the absorption capacity is larger than that of required value.