Rahimah Muhamad

The Tension Stiffening Mechanism in Reinforced Concrete Prisms

Tension stiffening is an important phenomenon in reinforced concrete because it controls not only deflections but also crack spacings, crack widths and the formation of multiple cracks. It is now common practice to study the effects of tension stiffening in concentrically loaded prisms, which is the subject of this paper, and use these behaviours as guidance for the effects of tension stiffening in reinforced concrete beams. As tension stiffening is a mechanism for stress transfer between the concrete and reinforcement, the interface bond stress-slip (τ–δ) properties are of utmost importance. In this paper, partial interaction theory is used to develop generic closed form solutions for crack spacings and widths, the load to cause primary, secondary cracks and subsequent cracks. Four different types of interface bond characteristics (τ–δ) are considered: a linear ascending bond slip which is useful at serviceability; a linear descending bond slip which is useful at the ultimate limit state; a nonlinear bond slip characteristic which closely resembles material bond slip behavior at all limits; and the CEB-FIP Model Code 90 (CEB 1992).

FRP-Reinforced Concrete Beams: Unified Approach Based on IC Theory

In general, steel-reinforced concrete involves a ductile steel material and a very strong and ductile bond between the steel reinforcement and concrete, so that debonding rarely governs the design. In contrast, fiber-reinforced polymer (FRP) reinforcement is a brittle material with a weak and brittle bond, making debonding a major issue. Consequently, there has been an extensive amount of research on FRP debonding and in particular intermediate crack (IC) debonding. This paper shows that the very good research by the FRP research community on the mechanics of IC debonding can be applied to a wide range of apparently disparate reinforced concrete behaviors to produce a unified approach. Hence, a single mechanism, or unified approach, based on IC debonding is proposed in this paper for dealing with moment rotation, tension stiffening and deflections, member ductility and moment redistribution, shear capacity, confinement, and fiber concrete for FRP RC beams.

Our obsession with curvature in RC beam modelling

Much of the early research in reinforced concrete dealt with steel reinforcement that was both ductile and had a very strong bond with the concrete. Hence partial-interaction, that is slip between the reinforcement and concrete and subsequently debonding, has not been a major issue. This has allowed researchers to develop the two-dimensional full-interaction moment-curvature approach to model the three-dimensional behaviour of reinforced concrete. It is shown in this paper that this two-dimensional full-interaction moment-curvature approach relies on a large amount of empirical calibration to ensure a safe design. Furthermore, it is shown that a three-dimensional partial-interaction moment-rotation approach can lead to more advanced structural mechanics models of reinforced concrete behaviours and subsequently better accuracy and more versatile models.

Health stress amongst engineering lecturer in Politeknik Sultan Salahuddin Abdul Aziz

Changes in Polytechnic Education Officer Scheme (PPPS) to Higher Education Officer Scheme (PPPT) in 2008 give impacts on the roles and responsibilities of the polytechnic lecturer. Therefore, it is substantial to identify the health stress amongst polytechnic lecturers, particularly the engineering lecturers due to these additional workloads by using Hazard Identification (HAZID) method with the stress level. This quantitative study is carried out by using random sampling via data collection of questionnaire survey from 145 lecturers at Department of Civil Engineering, Electrical Engineering and Mechanical Engineering, Politeknik Sultan Salahuddin Abdul Aziz. Revised personal stress inventory, Circular Services No 33 for year 2007 and Guideline of High Education Officer Version 3 are used as the references for the conceptual framework development. The findings of this paper show that the levels of health stress amongst the engineering lecturers in Politeknik Sultan Abdul Aziz due to over workload is low. The findings of this paper is expected to provide sufficient information related to health stress amongst engineering polytechnic lecturer.

FRP Design using structural mechanics models

The application and expansion of FRP reinforced concrete has been hindered and obstructed through the misconception and misunderstanding that empirically derived rules developed for steel reinforced concrete in cracked regions can be used either directly or as a guidance for FRP reinforced concrete. This assumption is incorrect because the empirical rules developed for steel reinforced concrete in cracked regions, as with all empirical rules, should only be used within the bounds of the testing regimes from which they were developed, which for steel reinforced concrete is normal strength concrete with high ductile steel that has very good bond. As these bounds do not apply to FRP reinforced concrete, the steel RC empirical rules for cracked concrete are of little or no help for FRP RC. In fact, they are often misleading and as such prevent the widespread use of FRP reinforcement. It will be shown and illustrated in this presentation that generic mechanics based rules can be developed at all load conditions for RC beams that applies to both steel and FRP reinforcement. And, furthermore, that these generic mechanics based design rules allay many of the misconceptions inferred by the empirically based RC design rules such as that moment redistribution cannot occur with brittle FRP reinforced concrete which is simply not the case.