BRI Research Paper


No.101

Techniques for Large Scale Testing at BRI Large Scale Structure Test Laboratory.

S.Okamoto*1, T.Kaminosono*2, M.Nakashima*2, H.Kato*3; March, 1983. 38p.

Abstract

Study on the behavior of building structures has greatly been progressed. Tests of structural members and assemblies and scale models of buildings have been conducted extensively all over the world.Numerical techniques for analysis of structures have also been developed a great deal thanks to innovation of digital computers. While many findings obtained from these studies have been reflected to various design practices, one problem remains as to how effectively they have been interpreted. Many engineering judgements are needed to incorporate member and assembly test data into structural design. Assumptions and simplifications are inevitably employed in numerical analysis. In order to evaluate the validity of these judgements and assumptions and to examine ultimately the overall behavior of building structures, one needs to execute tests of building structures on a large scale.

This paper introduces the structural test laboratory at the Building Research Institute, Ministry of Construction, Tsukuba, Japan.The laboratory has various facilities specially designed for large scale testing. They include the large test floor, loading system, data processing system and computer supervised testing system.

The laboratory has an open space of 30 meters by 60 meters in plan and 40 meters in height. In the middle of the laboratory, a 25 meter high wall is built to provide reaction to horizontally installed actuators with which earthquake forces are to be simulated. The capacity of the wall is 40 MN and 720 MN x m in allowable shear and bending moment. Either of two test floors, one on each side of the wall, can accommodate a building specimen of as much as 300 m floor area and 25 meter height.

Servo-controlled actuators are prepared for load application,having capacity of } 1000 kN in force and } 1000 mm in stroke. The needed power is provided by hydraulic pressure, and the actuators are controlled by@electronic servo-controllers.

Various types of displacement transducers (DLT's) are provided for the measurement of large displacements. Specially designed digital type DLT's are unique. They are magnetic response type and can measure displacements up to } 1000 mm with accuracy of 0.01 mm. Signals of these DLT's are completely noise free.

For systematic loading, data processing, and safety check, two computers are introduced. One serves for servo-control. During the test, the computer keeps supervising the motion of actuators for accurate command control and for safety check. The other computer, on line with data acquisition units, is used for data processing. This computer is linked to the servo-control computer. Commands for servo-controllers can then be created in this data processing computer and sent to the servo-control computer.

These two computers, servo-controllers, actuators, measuring instruments, and data acquisition units constitute one closed loop test system. This closed loop system, involving minimized manual operation,enables us to perform a new test method developed for simulation of building response under earthquake motions, referred to as the pseudo-dynamic (PSD) test method. This paper also introduces large scale tests conducted at the laboratory by means of this new method.


*1 Director, Production Department
*2 Research Engineer, Production Department
*3 Assistant Research Engineer, Production Department





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