Buildings: Building concrete columns

Case study: SOFO System

High-rise building monitoring
Concrete column monitoring
Separation of concrete strains
SOFO Pro Concrete Analyser used

Project Description

Summary: Load and deformation monitoring in concrete columns during construction and in the long term

Clients: HDB

Place: Singapore (Singapore)

Period: 2001 - N/A

Installation: SOFOTEC

Structure's short description: Singapore is a cosmopolitan city-state often described as a gateway to Asia with a city landscape of tall buildings. The Housing and Development Board (HDB), as Singapore's public housing authority, has an impressive record of providing a high standard of public housing for Singaporeans through a comprehensive building program. As part of quality assurance of new HDB tall buildings, it was decided to perform long-term structural monitoring of a new building of a project at Punggol East Contract 26. This monitoring project is considered as a pilot project with two aims: to develop a monitoring strategy for column-supported structures such as buildings, and to collect data related to the behavior of this particular building providing rich information concerning their behavior and health conditions. The monitoring is to be performed during whole lifespan of the building, from costruction to the in use. Thus, for the first time the sensors are used in a large scale life cycle monitoring of high-rise buildings. The Punggol EC26 project consists of six blocks founded on piles, and each block is a nineteen-storeys tall building, consisting of 6 Units and supported on more than 50 columns at ground level. The block called 166A has been selected for monitoring.

Aim of monitoring: The aims of monitoring are (1) increase of knowledge concerning the real structural behavior, (2) control of construction process, (3) increase of safety during the service, (4) enchance maintenance activities and (5) evaluation of structural condition after risky events such as earthquake, strong wind or terrorist attack. The monitoring is performed at (1) local, column level and (2) global, structural level. The ground columns have been selected for monitoring, being the most critical elements in the building. Total of ten sensors per block were installed by embedding. For aestetical reasons, small connection box protecting the sensors was also embedded in the columns. During the construction the readings were taken manually, while after the completition all the sensors will be centralized and interrogated from a control room.

Number of sensor: 120

Main Results: The use of fiber-optics sensors on such a large scale for monitoring of high-rise buildings is a first in Singapore and is directions that will help designers better understand the behavior of tall buildings during its life cycle from construction to service conditions. Such pioneering effort have already yielded results from the insights gained from enlarged knowledge concerning the real column behavior during construction and including the unexpected behavior of column C9 which will help research into the accurate modeling of complex structures. The detailed analysis of column behaviour was performed using SOFO Pro software and notably Concrete Analyser macro-sensor. It was possible to separate different parts of measured total strain such as elastic strain, creep and shrinkage. The employed monitoring strategy and the selected SOFO monitoring system have successfully responded to the design criteria. The monitoring strategy has shown high performance in spite limitations imposed by design criteria (limited number equipped columns, lack of temperature measurement, lack of accurate shrinkage and creep coefficients, uncertainty concerning the real load during campaigns of measurement, etc.).

Building during construction

Embedding of sensor and connection box, and reading of measurements during construction

Measurements carried out during the construction

Total strain monitoring and separation of elastic strain, creep and shrinkage using the SOFO Pro Concrete Analyser macro-sensor

Bibliography:

Monitoring of building columns during construction , Branko Glisic, Daniele Inaudi, Kee Ching Hoong, Joo Ming Lau, 5th Asia Pacific Structural Engineering & Construction Conference (APSEC), 26-28 August 2003, Johor Bahru, Malaysia, pages 593-606, 2003

Long-term monitoring of high-rise buildings using long-gage fiber optic sensors , B. Glisic, D. Inaudi, J.M. Lau, Y.C. Mok, C.T. Ng, 7th International conference on multi-purpose high-rise towers and tall buildings, Dubai, UAM, December 10-11, 2005

Finite Element Structural Monitoring Concept , Glisic B., Inaudi D., The 2nd fib International Congress June 5-8, 2006, Naples, Italy, on conference CD, ID 17-18, 2006

Continuous monitoring of concrete bridges during construction and service as a tool for data-driven Bridge Health Monitoring , D. Inaudi, B. Glisic, IABMAS'06 The Third Int'l Conference on Bridge Maintenance, Safety and Management, 16 - 19 July, Porto, Portugal, 2006

Large Scale Lifespan Monitoring of High-Rise Buildings Using Long-Gage Fiber Optic Sensors OPTIC SENSORS , Branko Glisic, Daniele Inaudi, Lau Joo Ming, Yap Tiem Yew, Ng Chun Tat, The 3rd International Conference on Structural Health Monitoring of Intelligent Infrastructure - SHMII-3, November 13-16, On conference CD, 2007

Fibre Optic Methods for Structural Health Monitoring , Branko Glisic and Daniele Inaudi, Johh Wiley & Sons, Ltd, 2007