Applied Mechanics and Materials Vol. 147

Abstract: This study reported the results of adding furfural on mechanical properties of Ordinary Iraqi cement. Furfural was used at four different ratios (1%, 2%, 3%, and 5 %) by weight to the mix of Iraqi Portland cement (Um- Quasar factory cement). The effect on the plasticizing and fluidity by table flow test for cement paste and slump test of fresh concrete were studied. The obtained results showed that added furfural is acting as super plasticizer. Effective relation was found between fluidity and ratio of added through effecting time of flow where the most effect additive ratio was found to be 3% .The radius of cement paste circle is linearly dependence which is a indicate of high workability. Obtained results explained in term of electrical charges on cement particles. Also found that adding furfural increasing the dispersion work between cement paste particles and preventing coarse agglomerated. The using of furfural with concrete indicates two kinds of concrete behavior. These behaviors were strongly dependence on furfural ratio .The critical value of added furfural was 1% and after which a plasticizing effect obtained. Splitting and flexural tensile test were conducted. Three types of curing methods include dry, moisture and water curing. The obtained results showed that the moisture curing was better than other curing methods due to good results obtained with splitting tensile (6.18 N/mm2) for 5% ratio and water curing is preferred for flexural tensile (7.05 N/mm2 at 2% wt% of furfural ). Finally, we compared our results with AL-Abraaj Kuwait cement and we found that the Iraqi cement (Um Quasar factory cement) was better.

Abstract: Reducing stress concentration is mainly done by fillets. However, new concepts toward better material properties lead designers and engineers to use these materials in their design, still changing in geometrical shape of desired models can help us in reducing stress concentration factors. New devices, including fast computers, reliable numerical methods (FEM), and numerical optimization approach can bring special devices for better designing besides considering design limitations in special industries. In this paper we focus on geometrical change (rounded groove) in the sudden changed section of the rounded shaft to reduce stress concentration in the most dangerous section. By optimizing this proposed change in the geometry of shaft we reduce the stress, so using of fillets can be neglected in the future designs to prevent metallurgical and design limitations.

Abstract: The shear behavior of prestressed self-compacting concrete (SCC) beams has been investigated in this study. The effect of compressive strength of SCC on the shear strength has been taken into account in test program. Based on the experimental data, the failure mechanism of the prestressed SCC beams was discussed and the shear transfer mechanism of the RC beam after the flexure-shear cracking was also analyzed.

Abstract: A finite element reinforced concrete model has been analyzed by the author with ANSYS 9 finite element program for both unstrengthened and CFRP-strengthened beams using concrete element model 25x25x25mm and discrete and smeared steel distribution with openings exist. The CFRP has been modeled using Solid46 element, which has orthotropic properties. The deflection results have been compared with an experimental and other finite element model which are performed by Mohamed [4], in which using 100x42.5x42.5 mm concrete element, smeared steel distribution with the same opening sizes, and modeling CFRP with ANSYS 5 finite element program using Link10 element which has a uniaxial properties. These results show that the author's model is much better than the Mohamed's [4] model comparing with the experimental one. A parametric study has been done on the proposed model for obtaining the maximum strains values for concrete and steel at failure loads, for different opening sizes and comparing them with the experimental one. This study show a good agreement between the proposed and experimental model results for strains values which indicate the efficiency of the proposed model for analyzing the unstrengthend and strengthened reinforced concrete beams.

Abstract: This paper is concerned with finite element analysis of corbels. Analyses were carried out on 254 × 405 × 254-mm reinforced concrete corbels. In this study 24 reinforced concrete corbels were considered. Variables considered in this investigation are: number, position, and different arrangement of secondary reinforcement. The results show that arrangement of the secondary reinforcement affects both strength and ductility of corbels.

Abstract: This research is to verify and propose the practical use of recycled aggregate concrete which is one of the recycling methods of construction wastes. This is because domestic construction industries have been more sustainably developed, and renovation and redevelopment of buildings for increasing the quality of life have been actively performed because the necessity of efficient management of construction wastes has been increased. In addition, the possibility of increased quality focused on recycled aggregate concrete with mixed polypropylene fiber was proposed on this research through material experiments basedon compressive and split tension strength.

Abstract: This paper studies the behaviors of carbon fiber reinforced plastics (CFRP) confining concretes exposed to fire, acid or alkaline environments. The concrete specimens wrapped with CFRP were exposed to different high temperatures or submerged to acid or alkaline solutions with different concentrations. All the specimens were then loaded under uni-axial compression test. The strength and ductility of concrete specimen were evaluated. The environmental influences on the confining effects of CFRP were also investigated. The results indicate that CFRP reinforcements can provide good confinements for concrete specimens, so both the strength and ductility of concrete specimens can be significantly increased. But CFRP confining concrete specimens exposed to fire environments over 300°C will lose some of the confinements and the strength and ductility are significantly decreased. When adhered by fireproof material, CFRP confining concrete specimens exposed to fire environments will not lose all the confinements and still retain most of their original strengths and strains. The fireproof material can really protect CFRP confining concretes from high temperatures. The fire resistance effect of fireproof material depends on its thicknesses and the fire environments. The results also show that CFRP confining concrete specimens when submerged into acid or alkaline environments will lose some of the confining effect of CFRP. The higher the concentration or the longer the soaking period of acid or alkaline environments, the more the CFRP material is damaged and thus CFRP confining concrete specimens lose some of their strenghs.

Abstract: This investigation was carried out to look the possibility of using chicken rachis as reinforcement in concrete mix. In this study, two different percentage of rachis from chicken feather were added to plain concrete comprises of 1% and 2% from the total weight of cement. Concrete with grade 30 were formed by using chicken rachis as additive material. Selected mechanical test were performed and the results were analysed. The mechanical tests included compressive strength, and splitting tensile strength. Comparison was made of these values and those of control specimen (without chicken rachis). The results showed an increment on strength for all mechanical tests done using concrete added with 1% chicken rachis compared to 2% chicken rachis added and those control specimens.

Abstract: A brief introduction is given about the history and current situation of Chongqing Bridge. Several combination bridges are introduced in detail about structure characteristic and innovation: Chongqing Wushan Yangtze River Bridge--steel tube- concrete composite arch bridge; Twinning of Chongqing Yangtze River Bridge--steel-concrete composite rigid frame bridge; Chaotianmen Yangtze River Bridge --steel truss - arch composite bridge; Caiyuanba Yangtze River Bridge --Rigid Frame - Tied Arch Bridge.