Quantifying moment redistribution in FRP-strengthened RC beams

Consideration of moment redistribution (MR) in the design of continuous reinforced concrete (RC) beams results in an efficient and economical design. Adding fibre-reinforced polymer (FRP) materials to reinforced structures to enhance flexural capacity leads to a reduction in ductility, such that design standards severely limit use of the MR in their design. This has forced engineers to use elastic analyses for strengthening design, which can lead to FRP wastage. To overcome this, complicated or empirical solutions have been applied to solve the problem of MR in strengthened concrete members, with limited success. This paper presents a novel theoretical strategy for quantifying and tracking MR in such members by employing basic structural mechanics without any need for estimating rotation capacity or ductility. Fully non-linear flexural behaviour of continuous strengthened members can be predicted and any geometry, loading arrangement and strengthening technique or configuration can be considered. The numerical model is validated against existing experimental data from the literature. Good agreement is shown between the experimental and numerical data, with the significance of this work being that, potentially, for the first time MR could credibly and confidently be incorporated into design guides for FRP strengthening of RC structures.The authors gratefully acknowledge funding provided by the Engineering and Physical Sciences Research Council (EPSRC EP/K019015/1) and the project partners (Concrete Repairs Ltd, Fyfe, Highways England, WSP/Parsons Brinckerhoff and Tony Gee and partners) for this research project

Analysis of Buried Pipes Under Traffic Loading Accounting For SOIL-Structure Interaction

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Male Rat Offspring Are More Impacted by Maternal Obesity Induced by Cafeteria Diet than Females-Additive Effect of Postweaning Diet.

Maternal obesity increases the risk of health complications in offspring, but whether these effects are exacerbated by offspring exposure to unhealthy diets warrants further investigation. Female Sprague-Dawley rats were fed either standard chow (n = 15) or 'cafeteria' (Caf, n = 21) diets across pre-pregnancy, gestation, and lactation. Male and female offspring were weaned onto chow or Caf diet (2-3/sex/litter), forming four groups; behavioural and metabolic parameters were assessed. At weaning, offspring from Caf dams were smaller and lighter, but had more retroperitoneal (RP) fat, with a larger effect in males. Maternal Caf diet significantly increased relative expression of ACACA and Fasn in male and female weanling liver, but not CPT-1, SREBP and PGC1; PPARα was increased in males from Caf dams. Maternal obesity enhanced the impact of postweaning Caf exposure on adult body weight, RP fat, liver mass, and plasma leptin in males but not females. Offspring from Caf dams appeared to exhibit reduced anxiety-like behaviour on the elevated plus maze. Hepatic CPT-1 expression was reduced only in adult males from Caf fed dams. Post weaning Caf diet consumption did not alter liver gene expression in the adult offspring. Maternal obesity exacerbated the obesogenic phenotype produced by postweaning Caf diet in male, but not female offspring. Thus, the impact of maternal obesity on adiposity and liver gene expression appeared more marked in males. Our data underline the sex-specific detrimental effects of maternal obesity on offspring

Prediction of Capacity for Moment Redistribution in FRP-Strengthened Continuous RC T-Beams

Because of the premature debonding of fiber-reinforced polymer (FRP) materials that results in a reduction in ductility, the problem of how to exploit moment redistribution (MR) in FRP-strengthened continuous reinforced concrete (RC) structures is unresolved. To date, limited research has been conducted into MR in such structures; a reliable and rigorous solution for quantifying MR throughout the loading cycle remains elusive. This paper aims to quantify MR and predict the capacity at reasonable accuracy, to encourage the use of FRP for the strengthening of existing continuous RC structures. Experiments conducted on 12 continuous T-beams are reported, and the findings are discussed. Strengthening configuration and anchorage scheme are the main variables. A new analytical strategy is described for quantifying MR, and the analytical results are then validated against the experimental results. Both experimental and analytical results confirm that there is no reason to restrict MR into strengthened zones. More importantly, MR, out of FRP-strengthened zones, can indeed occur, provided that the FRP is sufficiently anchored; reliable exploitation of this is now possible.Research funding provided by the Engineering and Physical Sciences Research Council (EPSRC: EP/K019015/1; United Kingdom) and the project partners (Concrete repairs Ltd, Fyfe, Highways England, WSP/Parsons Brinckerhoff and Tony Gee and partners) is acknowledged with appreciative thanks

Feasibility study on promoting the value of large-scale construction projects using the combination of value engineering and the ANFIS method

Value Engineering (VE) enables project managers to discover the size and location of problems in a project and to mitigate any potential backwardness. The current research aimed to find major impressive criteria and to measure their impact level on promoting the value of large-scale/mega projects using VE concepts. The hindrance and obstacles available in the application of VE in construction engineering were considered to ensure the accuracy. The main research objective was to forecast the effect of quality, cost, and time factors on the project value using an adaptive neuro fuzzy inference system (ANFIS) model. To create the ANFIS model, the required data were collected through a five-point scale Likert questionnaire, by which the expert opinions were obtained, and pairwise comparisons of the items were accomplished. The model was created using MATLAB. The statistical population was adopted from the experts and managers working in a large-scale project who were familiar with the concepts and details of VE and project management. According to the literature, more than 50 VE criteria were found, which were then reduced to 25 criteria based on experts’ opinions. These final criteria were categorized into three groups: cost, time, and quality. Afterwards, the data collected via the questionnaires were analyzed by the ANFIS model. Before completing the calculations, validity and reliability of the analytical model were investigated to ensure that the results are both valid and reliable enough for further use. The results showed that the criterion entitled ‘proper programming …’ had the highest impact on promoting the projects value, while the criterion entitled ‘prevention of work and responsibility interference …’ had the least influence. Both of the mentioned criteria were situated in the group of cost, indicating the higher importance of this group than that of the other groups

Effect of fiber-reinforced polymer strengthening on moment redistribution in reinforced concrete members

A reduction in ductility after applying fiber-reinforced polymer (FRP) materials to strengthen existing reinforced concrete (RC) structures has been reported in previous research. Consequently, design standards worldwide employ cautious guidance for the design of FRP strengthening systems, which limits the exploitation of moment redistribution in continuous structures. This paper aims to experimentally investigate and quantify moment redistribution within FRP-strengthened continuous RC members. Innovative tests conducted on four continuous slabs and six continuous T-section beams are described, and the findings are presented and discussed. The main variables in each group include strengthening configurations and anchorage schemes. All strengthened specimens failed through FRP debonding at different ultimate strains. Significantly, the experiments confirmed that there should be no artificial restriction placed on allowing moment redistribution into strengthened zones. Additionally, moment redistribution out of strengthened zones was also achieved and quantified

Moment redistribution in "anchored" FRP-strengthened continuous RC beams: A theoretical study

The problem of ductility and moment redistribution in FRP-strengthened continuous Reinforced Concrete (RC) structures is still unresolved, although the use of FRP as an effective technique to improve their strength and load capacity has become common place. As such, national standards have some limited and conservative guidance on redistribution of moments for designing of strengthened beams. This uncertainty is due to the brittle nature of FRP materials and the premature failure mechanisms in FRP-strengthened beams. This paper is a theoretical study, using a model, to investigate the ability of an anchored FRP-strengthened RC beam to redistribute moments both into and out of strengthened zones. The model examines the variations of flexural stiffness within the beam by considering the precise relationship between moment and curvature. This research has particularly focused on the influence of anchorage on moment redistribution. The analytical results show that there is indeed the possibility of redistribution of moments in RC members strengthened with FRP and anchorage, if applicable, increases the level of redistribution to some extent. This improvement occurs to different degrees, depending upon the position and amount of FRP materials used for strengthening. © 2013, NetComposite Limited

Experimental study of moment redistribution in reinforced concrete slabs strengthened with CFRP sheets

Due to the elastic behaviour and brittle nature of CFRP composite materials, and also their tendency to debond from the surface of Reinforced Concrete (RC) members before their tensile capacity is reached, moment redistribution is often not permitted in design codes for FRP-strengthened RC flexural structures. In this study, the moment redistribution capacity of RC slabs is examined by testing seven two-span slabs with externally bonded CFRP sheets. The specimens were designed to have an upper-bound original 30% redistribution capacity before FRP strengthening. Various strengthening configurations and anchoring schemes for the CFRP fabric were used in the specimens. The experimental results showed that it is feasible to redistribute a high proportion of bending moment into FRP-strengthened zones. It was also found that the level of moment redistribution exhibited out of these FRP-strengthened zones can be significant, depending on the quantity and anchorage of the CFRP composite material used