Development of a Tri-Axial Seismo-Accelero-Crackometer for Earthquake Ground Motion and Structural Damage Detection A. Adnan, S.M. Razak & M. Azimi Faculty of Civil Engineering, Universiti Teknologi Malaysia, Malaysia M.R. Abas Malaysian Meteorological Department ABSTRACT: Monitoring of earthquake ground motions required separate use of seismometer and accelerometer, to measure magnitude and distance, and intensity of the earthquake respectively. However, systems currently available are expensive, limiting user’s monitoring capability. This paper presents the development of tri-axial Seismo-Accelero-Crackometer for earthquake ground motion and structural damage detection. The system which consists of a spring-mass damper with sinusoidally forced eight identical linear springs, is developed such that the mass absolute motions and motion relative to base can be measured when force arising from base excitation imposed to the system. Similar concept of ground motion detection is applied locally to detect the wave or force released by the crack, indicating initiation of structural damage. Apart from measuring the three components of ground motions, Seismo-Accelero-Crackometer would also able to detect structural damage, hence providing economically practical solution for structural monitoring against earthquakes and damages, currently not practiced in most developing countries. Keywords: Earthquake. Crack, Structural Health Monitoring 1. INTRODUCTION Earthquake ground motions often induce severe structural damage. It is vital to monitor the structure to determine the location and severity of structural damage. For concrete structures, the structural damage began with crack initiation, followed by crack propagation and acceleration. Multi-site damage and hidden cracks in locations with difficult access are among major flaws encountered in the structural system. Structural integrity and reliability are concerns for civil and industrial structures, especially for essential civil structures such as hospitals, emergency facilities, communication and operation centers, petrochemical industries and nuclear power plants (Curadelli, O. and Ambrosini, D, 2011). Without proper structural health monitoring measures and subsequent corrective actions, the flaws in the aging or damaged structures could eventually lead to catastrophic failures (Zhang, Y., 2006). Visual inspection on its own provides no useful information until visible defects starts to appear in the structural members. For example, the presence of crack can offer valuable information, but they will not appear until late into the fatigue life of the structure (Adnan, A. et al., 2006). By definition, structural health monitoring is a scientific procedure comprising of several non-destructive processes including identification of operational and environmental loads acting on the structural component, recognition of the mechanical damage caused by that loading, and observation of damage growth as the structural component operates (Radzienski, M. et al., 2011). From security and economic point of view, the initial diagnostic has significant consequences. For instance, after an earthquake, it is important to determine the current serviceability of the affected structure to ensure safe operation in the present condition, and the remaining service life. In the case where small damage detected, the structure may be returned to operational condition, thereby reducing the economic impact whereas if substantial damage detected, the structure may require repair and rehabilitation works (Rytter, A., 1993).