Innovative instrumentation to study the behaviour of a high-rise building

Paper presented at 1st Distinguished Civil Engineer Symposium , Singapore , 31/3-1/4 1997.Standing at 280 m, the 66-storey Republic Plaza building is one of the tallest buildings in Singapore. The structural system of the building comprises a reinforced concrete core wall and a structural steel frame. The steel tube columns, filled with concrete, form an external ring, while the horizontal steel frame systems simply supported at the core wall support a composite slab at each floor. A large number of stress and strain gauges were embedded inside the core wall and the concrete filled tube (CFT) columns. At selected floors, strain gauges were mounted in the steel beams. During construction, the trends observed in stress and strain measurements of the core wall and the CFT columns are generally consistent with the increasing dead loads, while the tends in strain data for the floor beams are more complex. An ambient vibration survey (AVS) was conducted after the completion of the structure. From the AVS measurements of dynamic lateral response, natural frequencies and mode shapes for lower lateral and torsional modes have been obtained. Results of the finite element models for the core wall/steel framing system agree reasonably well with the measured translational fundamental frequencies. However, without a high level of refinement, the finite element models cannot reflect the torsional behaviour. There is no evidence that the curtain wall system affects stiffness or damping properties of the structure at low excitation levels

Response of tall buildings to weak long distance earthquakes

This is the peer reviewed version of the article, which has been published in final form at DOI 10.1002/eqe.32. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.In the last decade, two tall buildings in Singapore were instrumented with accelerometers and anemometers for the original purpose of identifying the characteristics and effects of wind loading. During the monitoring it became clear that the largest acceleration responses should result from ground motions due to earthquakes having magnitudes between 6 and 8 and epicentres at least 350 km distant. The paper describes the strategy for identifying and capturing the signals from distant tremors, which depends on tracking the RMS response levels in the second vibration mode. Characteristics of some recorded signals are given. While response levels are generally small, the frequency content coincides with the range of fundamental mode frequencies for high rise residential buildings. The validity of using a tall building as a ‘weak-motion’ seismograph is discussed by considering the mode shape of the building and the measured transfer function between basement and roof responses

Identifying loading and response mechanisms from ten years of performance monitoring of a tall building

Author version of article. The final published version is available from the publisher website via: doi:10.1061/(ASCE)0887-3828(2008)22:1(24)© 2008 ASCEIn 1993 Shimizu Corporation provided the opportunity to record manually readings of stress and strain gauges they had embedded at the 18th storey of a 65-storey office tower under construction in Singapore. Static readings continued during construction and long after, and capitalising on access to the building and assistance of both contractor and owner, monitoring systems for tracking wind, acceleration and deflection were installed and progressively upgraded. Further, a comprehensive ambient vibration survey and finite element model updating exercise provided a thoroughly validated analytical model of the structure. This model has been used in parallel with the analog wind and tremor ‘super-sensor’ of the building itself to provide direct evidence and characterization of the seismic and wind loadings on the building. This paper describes the evolution of the monitoring system and its capabilities together with some of the insights the system provided into structural and loading mechanisms during its operational life until early 2005.

Effects of infill walls and floor diaphragms on the dynamic characteristics of a narrow-rectangle building

This is the peer reviewed version of the following article: Pan, T.-C., You, X. and Brownjohn, J. M. W. (2006), Effects of infill walls and floor diaphragms on the dynamic characteristics of a narrow-rectangle building. Earthquake Engineering and Structural Dynamics, 35: 637–651. .which has been published in final form at: doi:10.1002/eqe.550Most buildings in Singapore are lightly reinforced concrete structures which are manly designed for gravity loading only, because Singapore is an island country located in a low to moderate seismic region. The dynamic properties of a typical high-rise residential building with a long, narrow rectangular floor plan are studied using both experimental and numerical methods. The effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the building are discussed in detail. The results from the ambient vibration tests are correlated with the numerical results of three different finite element models with different levels of sophistication. They include a bare frame model, a frame model with brick infill walls, and a frame model with both brick infill walls and flexible diaphragms. The dynamic properties of the third model match very well with the measured results in terms of both the natural frequencies and the mode shapes. The correlation results demonstrate the respective effects of the brick infill walls and the flexible diaphragms on the dynamic characteristics of the narrow-rectangle building structure