US-JAPAN COOPERATIVE RESEARCH PROJECT ON
Building Research Institute, Japanese Ministry of Construction, initiated a 5-year research and development project of "Smart Materials and Structural Systems" in 1998 as part of U.S.-Japan cooperative research efforts. U.S. Counterpart is National Science Foundation. Smart Structural Systems (also called as Auto-adaptive Media) are defined as systems that can automatically adjust structural characteristics, in response to the change in external disturbance and environments, toward structural safety and serviceability as well as the elongation of structural service life. The research and development of (1) Concept and performance evaluation method of smart structure system, (2) Sensing of structure performance, and (3) Development and evaluation of structural elements using smart materials will be conducted.
A conventional structural system is designed to achieve a set of intended
functions under pre-selected loads and forces. Such a conventional system
can not successfully develop its ability against unexpected loads and forces
unless a large safety factor is provided for safety limit states to take
into account various uncertainties in load and force amplitudes and structural
response. Furthermore, since seismic design requirements have been improved
after each bitter lessons learned through past earthquake disasters, the
safety level of old buildings is always inferior to new buildings as evidenced
in many past earthquake disasters, e.g., the 1995 Kobe earthquake disaster.
Strengthening or removal of those old buildings becomes necessary to protect
Smart Structural Systems are defined as structural systems with a certain-level of autonomy relying on the embedded functions of sensors, actuators and processors, that can automatically adjust structural characteristics, in response to the change in external disturbance and environments, toward structural safety and serviceability as well as the elongation of structural service life.
The research and development are conducted focusing on the following issues.
To achieve research objectives, following three sub-committees have been
formed under Technical Coordinating Committee of the project.
The research organization is illustrated in Figure 1. The Building Contractors Society, the Housing and Urban Development Cooperation, the Building Center of Japan, and several materials and sensors makers participate in this R/D project.
6-8, January, 2000
US-JAPAN Workshop on Smart Structural Systems - the first JTCC of US-Japan cooperative research project -
7-9, December, 2000
The Second Joint Technical Coordinating Committee Meeting - U.S.-Japan Cooperative Research on Auto-adaptive Media (Smart Structural Systems) -
18-19 October, 2002
Workshop on Smart Structural Systems organized for U.S.-Japan Cooperative Research Programs on Smart Structural Systems (Auto-adaptive Media) and Urban Earthquake Disaster Mitigation
The Third Joint Technical Coordinating Committee Meeting
Sub-committee on Structural System
The basic concept and strategies for the development of smart structural systems should be established, and, the followings are the main targets of research and development:
1. Definition and categorization of smart structural systems
2. Summary of the required performance of smart materials or devices to realize the smart structural systems
3. Performance verification of proposed smart structural systems by computer simulations and experiments
4. Established of guideline for the performance evaluation of smart structural systems
The following three systems are currently under consideration as the smart structural systems:
1. Autoadaptive structural systems
2. Reinforced concrete (RC) structural systems with damage fuses
3. Innovative life safety systems
The each system is researched and developed by the corresponding working group.
1. WG for Auto-adaptive Structural System
Autoadaptive structural systems can adjust structural characteristics, in response to the change in external disturbance and environments. These systems are expected to show higher performances relying on the embedded functions of sensors, actuators or processors than the conventional structural systems.
In last fiscal year, some autoadaptive structural systems such as the smart rocking systems, the base isolated systems with adaptive dampers and the frame systems with the adaptive dampers or SMA devices were proposed. In this fiscal year, the performance of the proposed structural systems will be investigated using analytical and experimental simulations. And performance evaluation guidelines for autoadaptive structural systems will be discussed.
2. WG for High Performance Structural System
The main objective of this working group is to develop the performance based design/assessment methods using the damage control concept for reinforced concrete buildings with damage fuses such as energy absorbing devices, damage concentrating devices and damage sensor for the devices. The development of repairing and replacing techniques for the damage fuses is also included in the scope of research objectives. Investigated in this fiscal year was the possibility of applying the existing performance based seismic evaluation method such as the Capacity Spectrum Method, the Energy Input Rate Spectrum Method and so on for RC buildings with damage fuses.
3. WG for Smart Seismic Rehabilitation System
Our group is examining the performance and resistance of seismic reinforcement on low-rise inferior structures. We have also conducted a survey for academic authorities, graduates and engineers. They have presented our group with new plans with smart device and/or system for reinforcement or life safety. The ideas that were collected were summarized into the following four methods; 1)The lifting structures, 2)The supporting structures, 3)The base-isolation system, 4)The adaptive structures.
We are discussing verification method of performance of our final methods. Shaking table test will be conducted at the final stage to verify their performance.
Sub-committee on Sensing and Monitoring Technology
1. WG for Structural Performance Evaluation
Final target of this working group is to develop technology for evaluating seismic and serviceability performance. At first contribution of non structural elements for their performance was made clear analytically. Target structure of analysis is real building built in the site of building research institute. The building has eight stories and one basement, and the structure consists of steel and reinforce concrete. As the result of analysis vibration model for evaluating performance were proposed. In addition to this analysis, damaged parts of this building against big earthquake were made clear using
push over analysis
2. WG for Structural Health Monitoring
Sensing and monitoring are the key features of smart structural systems, our main target is Structural Health Monitoring. Identification methods for detecting structural damage such as yielding, cracks, etc. using sensors are developed. This year, we discussed pre-analytical study on damage detection tests of five-story steel frame with simulated damages. Fiber brag grating (FBG) sensors, accelerometers and strain gauges will be installed in this frame. From the results of pre-analytical study, we can estimate which story is damaged from the change of natural period or mode shape to some extent. Damage identification method using modal analysis is shown here. Damage detection methods from local information will be also examined, and various identification methods will be also applied.
Exterior of Test Frame
3. WG for Information System with Sensors
The result outline of Sensor Network WG is shown below.
The sensor net work is to detect the damage of buildings and also is to inspect a damage degree in cities. Moreover, it is to transmit the signal to operate effectors to prevent from damage.
This WG classified a sensor network into three types of "the network for the small scale buildings", "the network for the large scale buildings" and "the network for the cities", according to the scale of the buildings. As for each network, the necessary data and the utilizing method of them are investigated.
Research organization of sensing and monitoring technology sub-committee has been restructured since the fiscal year 2000. Reconstruction means that performance evaluation working group and damage detection have been integrated and new working group is named health monitoring working group. Smart sensing working group has been established. Research and development Items in this working group are the survey of new sensor, application technologies of new sensors and so on.
Sub-committee on Effector Technology
1. WG for Shape Memory Alloy (SMA)
Plan of SAM working group in 2000
In this physical year, the three experiments, i.e., tension tests, compression tests and buckling tests, will be carried out to obtain basic data about the mechanical properties such as stress-strain relation under cyclic loading of SMA wires and bars, buckling strength and post buckling behavior of SMA braces. Some analytical models on stress-strain relation of SMA material will be proposed from these data. Usage of SMA wires or bars to brace elements or base isolation ones will be discussed and developed, and their seismic performance will be estimated by analysis.
By T. Fukuta in BRI
2. WG for Engineered Cementitious Composites
Issue of development in the Cementitious Composites WG is damage tolerant structural systems utilizing High Performance Fiber Reinforced Cementitious Composites (HPFRCC) materials and elements.The purpose of this research is to develop high performance cementitious energy dissipation devices and steel-HPFRCC composite elements to achieve the damage tolerant R/C structural system as a smart structural system. Those systems will have much merit not only in sturctural performance but in durability, workability, environmental efficiency and cost effectiveness. Feasibility study on the other types of cementitious material, element and system like self-repairing material is also included in this research. In the fiscal year of 1999, the detailed research plan of each item was discussed. Also, structural efficiency of the steel-HPFRCC system was clarified through a structural test of column elements.
3. WG for Electro/Magneto Rheological (ER/MR) Fluids
Electro/magneto rheological fluid WG develops adaptive structure by electro/magneto rheological fluid. In 2000, the WG is working on the following research items.
1) Development and improvement of MR fluid
2) Research for performance evaluation of MR fluid
3) Research for modeling and evaluation method of MR dampers
4) Improvement of the technical data for the performance of MR dampers
5) Analytical study of base-isolated structure controlled by MR dampers
6) Parametric study of the SI (skeleton-infill) concepts by MR dampers
7) Study for application of MR dampers to real scale building model
4. WG for Induced Strain Actuators (ISA)
Induced Strain Actuators (ISA) can change their own shapes according to external electric/magnetic fields, and vice versa. Recently these materials have been widely used for the small/precision machines because of some advantages from viewpoint of small sizes, rapid reaction, high power, high accuracy etc.
The objectives in this study are to develop smart members for building and to realize the smart, comfortable and safe structures. Designing guidelines of ISA materials/devices are also discussed.
The research items and example images are as follows:
・Experimental study of ISA materials
・Development of smart structural members using ISA devices
・Using ISA as sensor materials
・Improvement of acoustic environments
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