FRP STRUCTURE DESIGN METHOD BASED ON THE STIFFNESS EQUIVALENCE: CASE STUDY AND PRACTICE
Article history: Received 08.05.2012. Received in revised form 20.07.2012. Accepted 03.09.2012. Nowadays, fiber reinforced polymer materials are getting widely used in civil engineering. They have some advanced engineering characteristics like high stiffness-to-weight ratio, high strength-toweight ratio, anti-electromagnetic interference, electrical isolation and their long term durability. Metal and concrete, two main kinds of construction materials, are prone to failure during their structure service lives because of environmental adverse effects and atmospheric weathering. Those harsh attacks/impacts are oxidization, acidification, high temperature and alkali corrosion. After various maintenance methods like isolating the attacks or protecting plastic skins, an interface crack between protections can easily propagate and cause some durability concern. Fiber reinforced polymer emerges in a new era of civil engineering and can surely be added to traditional materials and/or traditional materials can surely be substituted by this material. This paper sets out to unfold a case study on how fiber reinforced polymer works in civil structures.
Concrete crack potential predictions with the aid of a novel plastic ring, electrical resistivity and setting time
Hydration and restrained shrinkage crack behaviours of different concrete grades were independently monitored using a non-contact electrical resistivity apparatus and a novel plastic ring mould respectively. The electrical resistivity curve trend is similar for all the concrete samples, in which the lowest concrete grade has the highest resistivity until reaching acceleration point which was then overtaken by the highest concrete grade. Four different hydration periods were identified upon which the hydration process can be based; these periods are classified into dissolution, induction, acceleration and deceleration periods. Also, initial and final setting times for the samples were examined, which confirmed that the decreasing rate of resistivity development for the lower concrete grade corresponds to its initial setting time range. Restrained shrinkage crack result shows that the highest concrete grade propagated cracks earlier than the lowest concrete grade and thereby the higher cracking potential of higher strength mixture was confirmed. Linear fitting was then developed to estimate concrete crack potential based on its electrical resistivity. Hence, both electrical resistivity measurement and novel plastic mould (which is very cheap, user-friendly and fast filled) are hereby proposed as a convenient alternative means of assessing concrete cracking potential.
Life-cycle performance model for composites in construction
Abstract Fiber reinforced polymer (FRP) composites have become popular in recent years both in the construction of new facilities and in the renewal of existing structures owing to their technical advantages and economic benefits over traditional materials. However, there is a concern in the civil engineering industry over the lack of information on the long-term durability and life-cycle performance of composite materials used for infrastructure applications. The model proposed in this paper predicts infrastructure deterioration based on the material degradation by considering the environmental exposure, operation conditions, material durability, and the effect of maintenance actions on the structure over time. The analytical framework is generic and can be used to model the life-cycle performance of different types of structures and is applicable to different material types and exposure conditions. It is proposed as being particularly suitable for composite applications in civil engineering for which historical performance data are not available. A complete description of the modeling framework is presented here along with a hypothetical example case to illustrate the procedure.