Reinforced concrete (RC) box girders are a common structural member for road bridges in modern construction. The hollow cross-section of a box girder is ideal in carrying eccentric loads or torques introduced by skew supports. This study employed acoustic emission (AE) monitoring on multicell RC box girder specimens subjected to laboratory-based torsion loading. Three multicell box girder specimens with different cross-sections were tested. The aim is to acquire AE analysis data indicative for characterizing torsion fracture in the box girders. It was demonstrated through appropriate parametric analysis that the AE technique could be utilized to effectively classify fracture developed in the specimens for describing their mechanical behavior under torsion. AE events localization was presented to illustrate the trend of crack and damage propagation in different stages of fracture. It could be observed that spiral-like patterns of crack were captured through AE damage localization system and damage was quantified successfully in different stages of fracture by using smoothed b-value analysis.
Matched MeSH terms: Construction Materials/standards*
The present study examines the use of collars and geobags for reducing local scour around bridge piles. The efficiency of collars and geobags was studied experimentally. The data from the experiments were compared with data from earlier studies on the use of single piles with a collar and with a geobag. The results showed that using a combination of a steel collar and a geobag yields the most significant scour reduction for the front and rear piles, respectively. Moreover, the independent steel collar showed better efficiency than the independent geobag below the sediment level around the bridge piles.
Matched MeSH terms: Construction Materials/standards*
The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system.
Matched MeSH terms: Construction Materials/standards*
Malaysia has partially banned the use of asbestos. The prohibition of asbestos building materials in schools, clinics, and hospitals built by government started in 1999. Since 2005, prohibition has also been applied to all government buildings. However, asbestos construction materials such as roof and ceiling tiles are still sold in the market. There are no acts or regulations prohibiting the use of asbestos in private buildings in Malaysia. Asbestos was first used for industrial purposes in Malaysia in the 1960s and the first regulations related to asbestos have been around since the 1980s. Non-governmental organizations have been pushing the government to impose a total ban since the 1980s. Asbestos is still used in the manufacturing sector under the "control use" concept. The study found difficulties in established and validated medical record data on asbestos-related diseases. This paper reviews existing asbestos-related regulations and guidelines in Malaysia and discusses the urgency for a total ban in the use of asbestos in building materials in the country. In the meanwhile, stricter enforcement of occupational safety and health regulations related to the use and exposure of asbestos among workers in the manufacturing, construction, maintenance, and demolition sectors has been in place.
Matched MeSH terms: Construction Materials/standards*