Time-Dependent Bearing Capacity Increase of Uniformly Driven Tapered Piles- Field Load Test

This paper describes the results of field load tests on concrete tapered and straight-sided piles driven into a cohesive saturated ground. The piles were driven into a depth of 12 m at a close distance using diesel hammer machine. The soil profile consisted mainly of soft CL and ML in the Unified Soil Classification System. Two piles were tested initially after 35 days from the installation date using maintained load test procedure according to ASTM D1143-81. Then similar tests were performed on two piles after 289 days following the installation date. The results showed the capacities of both piles were roughly identical after 35 days from the installation time. The load-settlement behaviour of tapered showed stiffer than that of the straight-sided pile. After 289 days from the installation date, both piles offered greater bearing capacity values. The long term bearing capacity of a tapered pile was about 80% greater than that of a uniform pile of the same volume and length. In long term, for a given load level applied to the pile heads, the tapered pile offered greater stiffness than the straight-sided pile. This indicates the advantageous use of tapered piles instead of straight sided piles of the same volume and length

The effect of fine and coarse recycled aggregates on fresh and mechanical properties of self-compacting concrete

Today, the use of recycled aggregates as a substitute for a part of the natural aggregates in concrete production is increasing. This approach is essential because the resources for natural aggregates are decreasing in the world. In the present study, the effects of recycled concrete aggregates as a partial replacement for fine (by 50%) and coarse aggregates (by 100%) were examined in the self-compacting concrete mixtures which contain air-entraining agents and silica fumes. Two series of self-compacting concrete mixes have been prepared. In the first series, fine and coarse recycled mixtures respectively with 50% and 100% replacement with air entraining agent were used. In the second series, fine recycled (with 50% replacement) and coarse recycled (with 100% replacement) were used with silica fume. The rheological properties of the self-compacting concrete (SCC) were determined using slump-flow and J-ring tests. The tests of compressive strength, tensile strength, and compressive stress-strain behavior were performed on both series. The results indicated that air-entraining agent and silica fume have an important role in stabilization of fresh properties of the mixtures. The results of tests indicated a decrease in compressive strength, modulus of elasticity, and energy absorption of concrete mixtures containing air entrained agent. Also, the results showed that complete replacement (100%) with coarse recycled material had no significant effect on mechanical strength, while replacement with 50% fine recycled material has reduced compressive strength, tensile strength, and energy absorption

Multi-Hole Waveguide Directional Couplers

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