Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 6 Articles
The paper investigated the use of fiberglass-reinforced plastic (FRP) grid for reinforcement in link slabs for jointless bridge decks.\r\nThe design concept of link slab was examined based on the ductility of the fiberglass-reinforced plastic grid to accommodate bridge\r\ndeck deformations. The implementation of hybrid simulation assisted in combining the experimental results and the theoretical\r\nwork. The numerical analyses and the experimental work investigated the behavior of the link slab and confirmed its feasibility.\r\nThe results indicated that the technique would allow simultaneous achievement of structural need, lower flexural stiffness of the\r\nlink slab approaching the behavior of a hinge, and sustainability need of the link slab. The outcome of the study supports the\r\ncontention that jointless concrete bridge decks may be designed and constructed with fiberglass-reinforced plastic grid link slabs.\r\nThis concept would also provide a solution to a number of deterioration problems associated with bridge deck joints and can be\r\nused during new construction of bridge decks. The federal highway administration provided funds to Louisiana Department of\r\nTransportation through the innovative bridge research and development program to implement the use of FRP grid as link slab....
Experimental data are presented for six concrete specimens subjected to displacement reversals. Two specimens were reinforced\r\nlongitudinally with steel bars Grade 410 (60 ksi), two with Grade 670 (97 ksi), and two with Grade 830 (120 ksi). Other\r\nexperimental variables included axial load (0 or 0.2 f \r\nc Ag) and volume fraction of hooked steel fibers (0 or 1.5%). All transverse\r\nreinforcement was Grade 410, and the nominal concrete compressive strength was 41MPa (6 ksi). The loading protocol consisted\r\nof repeated cycles of increasing lateral displacement reversals (up to 5% drift) followed by a monotonic lateral push to failure.\r\nThe test data indicate that replacing conventional Grade-410 longitudinal reinforcement with reduced amounts of Grade-670 or\r\nGrade-830 steel bars did not cause a decrease in usable deformation capacity nor a decrease in flexural strength. The evidence\r\npresented shows that the use of advanced high-strength steel as longitudinal reinforcement in frame members is a viable option\r\nfor earthquake-resistant construction....
A short computer program, fully documented, is presented, for the step-by-step dynamic analysis of isolated cables or couples of\r\nparallel cables of a cable-stayed bridge, connected to each other and possibly with the deck of the bridge, by very thin pretensioned\r\nwires (cross-ties) and subjected to variation of their axial forces due to traffic or to successive pulses of a wind drag force. A\r\nsimplified SDOF model, approximating the fundamental vibration mode, is adopted for every individual cable. The geometric\r\nnonlinearity of the cables is taken into account by their geometric stiffness, whereas the material nonlinearities of the cross-ties\r\ninclude compressive loosening, tensile yielding, and hysteresis stress-strain loops. Seven numerical experiments are performed.\r\nBased on them, it is observed that if two interconnected parallel cables have different dynamic characteristics, for example different\r\nlengths, thus different masses, weights, and geometric stiffnesses, too, or if one of them has a small additional mass, then a single\r\npretensioned very thin wire, connecting them to each other and possibly with the deck of the bridge, proves effective in suppressing,\r\nby its hysteresis damping, the vibrations of the cables....
The aim of this study is to investigate the strengths and drying shrinkage of alkali-activated slag paste and mortar. Compressive\r\nstrength, tensile strength, and drying shrinkage of alkali-activated slag paste and mortar were measured with various liquid/slag\r\nratios, sand/slag ratios, curing ages, and curing temperatures. Experimental results show that the higher compressive strength and\r\ntensile strength have been observed in the higher curing temperature. At the age of 56 days, AAS mortars show higher compressive\r\nstrength than Portland cement mortars and AAS mortars with liquid/slag ratio of 0.54 have the highest tensile strength in all AAS\r\nmortars. In addition, AAS pastes of the drying shrinkage are higher than AAS mortars. Meanwhile, higher drying shrinkage was\r\nobserved in AAS mortars than that observed comparable Portland cement mortars....
The 3D numerical simulation was carried out for an idealized Rankine vortex using nonlinear k-e model (one kind of RANS\r\nmodel) and large eddy simulation (LES) techniques. In this 3D simulation, the vortex flow field was given to rotate with the\r\nvertical axis in a free surface rectangular domain. In order to investigate the predictability of standard (linear) and non-linear k-e\r\nmodels, the decay of a trailing vortex was simulated and compared with previous DNS data. The governing equations for mean\r\nvelocities and turbulent flows were discretized with the finite volume method based on a staggered grid system. It was observed\r\nthat in the growth phase as well as in stabilized phase of turbulence, the decay rate of tangential velocity by RANS model was well\r\ncomparable with LES simulation as well as previous DNS data. However, in the decay phase of turbulence, RANS model showed\r\nslightly faster decay of tangential velocity due to its slower decay of turbulence compared to LES or DNS. The patterns as well as\r\nmagnitudes of secondary currents predicted by RANS and LES models were well comparable to each other....
High density aggregates of iron ore are imported by petroleum sector in Egypt, for utilization in manufacturing of concrete mix used for coating of offshore petroleum pipelines. The heavy aggregates form up to 75% of the concrete mix, depending on the final density desired for the reinforced concrete coating. These aggregates are composed of well graded angular to sub angular grains of high density aggregates, In earlier studies we succeed to found the Egyptian Ilmente ore adequate for concrete weight coating and already utilized for many pipeline projects in Egypt. In this study the evaluation of Um Bogma manganese-Iron ore to be used in subsea pipeline concrete weight coating, meantime the ore by product is available by huge quantities in Sinai Manganese Company. The laboratory and field tests conducted for the manganese ore forming concrete mix, which composed from manganese ore, cement and fresh water according to coating specification requirements, the ore produces a concrete mix of 175-185 pcf (2804-2964 Kg/m3) minimum dry density and compressive strength varying from 40-48 N/MM² (400-480 kg/cm²) which satisfied the standard specification of submarine pipeline coating....
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