Chee Ghuan Tan

Monitoring Corrosion Process of Reinforced Concrete Structure Using FBG Strain Sensor

A Major factor that affects the durability of a concrete structure is cracks formation induced by expansion of reinforcement corrosion. Therefore, monitoring and evaluating the corrosion level of the structure is essential for its safety. In order to monitor corrosion, an innovative methodology based on Fiber Bragg Grating (FBG) sensing technique was developed and tested in this paper. The method uses the volume of corrosion products to detect the evolution of corrosion. The corrosion process was accelerated by impressed current technique. A correlation between the FBG wavelength shift and corrosion percentage of reinforcement was found.

External CFRP repairing of pretested beams reinforced using prestress rebars

This paper presents experimental and theoretical investigations on flexural CFRP strengthening/repairing of pretested (i.e., damaged) beams reinforced using prestress rebars. Six beams were fabricated and tested under a four-point bending system to failure. The internal longitudinal tensile and transverse steel reinforcements of these beams were reinforced using prestress and mild steel rebars, respectively. After the application of load, these pretested (i.e. damaged) beams were repaired and tested using externally bonded Carbon Fibre Reinforced Polymer (CFRP) reinforcement. This study investigated the effects of number of CFRP plies, three different grades of concrete, and wrapping layouts. The results confirm that the CFRP repaired beams reinforced with prestress rebars efficiently increased the flexural capacity, however the trend of ductility was inadequate as in damaged-unstrengthened beams. Experimental results show that the flexural capacity of the repaired beams increased to a maximum enhancement of 172.4% over the damaged-unstrengthened beam. It was experimentally observed that CFRP repaired beams with low grade of concrete could provide better performanceas compared to higher grades of concrete. The comparison of experimental and theoretical results had good agreement for higher grades of concrete, whereas, in case of low grade concrete, the experimental results were relatively greater than the theoretical results.

Site Characterization of Marine Clay Deposits in South Seberang Prai, Penang using Combined Active and Passive Multichannel Analysis of Surface Wave (MASW)

The multichannel analysis of surface wave (MASW) has drawn considerable interest in subsoil investigation and characterization. This method has been studied and improved in the last few decades, thereby leading to several combinations of existing active and passive methods. This study aims to identify the presence of marine clay layer using combined active and passive MASW methods. The shear wave velocity profile obtained interpreting clay layer within the range of 70-150 m/s and sand layer within the range of 100-300 m/s. Results suggest that the combined MASW method significantly improves shear wave velocity profiling in shallow and deep soil layers and the results are validated using the cone resistance and shear wave velocity estimated from cone penetration test.Introduction

Effects of Site Classification on Empirical Correlation between Shear Wave Velocity and Standard Penetration Resistance for Soils

In seismic engineering, the dynamic property of the soil is one of the most important aspects in ground response analysis. Dynamic property is significantly affected by local soil deposits. Shear wave velocity (Vs) of soil is one of the main parameters in determining the amplification factor on ground surface. It is not economically feasible to measure Vs for all sites. Therefore, a reliable empirical correlation between Vs and standard penetration resistance (Nspt) will be useful since Nspt data are easily obtainable in construction industry. This study aims to develop an empirical correlation between Vs and Nspt for all soils by considering the effect of site classification according to the Uniform Building Code. New empirical correlations for all soils are presented in this study and well compared with the previous study to evaluate prediction capability. Results show that site classification has a significant impact on the Vs estimation, and that the proposed correlations are the most appropriate for estimating the Vs profile in the studied area compared with existing correlations.

Soft storey effects on plastic hinge propagation of moment resisting reinforced concrete building subjected to Ranau earthquake

On 5th June 2015, a moderate earthquake with Mw 5.9 hit Ranau, resulted in damages of the existing nonseismically designed buildings, such that 61 buildings, including mosques, schools, hospitals and Ranau police headquarters were suffered from different level structural damages. Soft storey irregularity is one of the main reasons of the building damage. This study is to investigate the soft-story effect on the propagation path of plastic hinges RC building under seismic excitation. The plastic hinges formation and seismic performance of five moment resisting RC frames with different infill configurations are studied. The seismic performance of building is evaluated by Incremental Dynamic Analysis (IDA). Open ground soft storey structure shows the lowest seismic resistance, collapses at 0.55g pga. The maximum interstorey drift ratio (IDRmax) in soft storey buildings ranging from 0.53% to 2.96% which are far greater than bare frame ranging from 0.095% to 0.69%. The presence of infill walls creates stiffer upper stories causing moments concentrate at the soft storey, resulting the path of plastic hinge propagation is dominant at the soft storey columns. Hence, the buildings with soft storey are very susceptible under earthquake load.

Site-specific empirical correlation between shear wave velocity and standard penetration resistance using MASW method

In seismic engineering, dynamic property of the soil is one of the most important aspects in ground response analysis. It is significantly affected by the presence soil deposits of the site. Generally, the average shear wave velocity at top 30 m (Vs30) of soil deposit is used to represent stiffness of the soil and is one of the important parameters to determine the soil amplification factor on the ground surface and site classification. Vs30 is usually determined by carry out wave propagation test on the field. However, it is not economically feasible to conduct test at all sites. Therefore, a reliable empirical correlation between shear wave velocity and standard penetration resistance (Nspt) would be useful since the ease of obtaining the Nspt from site investigation report. Although there are quite a number of these empirical correlations available in literature, but they are region specific and cannot be applicable to all region. In this study, Multichannel Analysis of Surface Wave (MASW) is employed to obtain the shear wave velocity profile of site which needed to develop the empirical regression equations between Vs and Nspt for sand, silt and clay. MASW test has been carried out on the twenty sites which posses of Nspt profiles around Penang Island. The empirical regression equations developed by the study area are exhibit good prediction performance. It can be used for the area which consist of soft to stiff clay and silt and loose to dense sand.