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Self compacting concrete (SCC) is special type of concrete which is highly flowable and non-segregated and by its own mass, spreads into the formwork without any external vibrators, even in the presence of thick reinforcement. But SSC is also brittle nature like conventional concrete, which results in abrupt failure without giving any deformation (warning), which is undesirable for any structural member. Thus, self-compacting concrete (SCC) needs some of tensile reinforcement to enhance tensile strength and prevent the unsuitable abrupt failure. But fiber increased tensile strength of concrete more effectively than compressive strength. Hence, it is essential to add pozzolanic materials into fiber reinforced concrete to achieve high strength, durable and ductile concrete. This study is conducted to assess the performance of SCC with substitutions of marble waste (MW) and coconut fiber (CFs) into SCC. MW utilized as cementitious (pozzolanic) materials in percentage of 5.0 to 30% in increment of 5.0% by weight of binder and concrete is reinforced with CFs in proportion of 0.5 to 3.0% in increment of 0.5% by weight of binder. Rheological characteristics were measured through its filling and passing ability by using Slump flow, Slump T50, L-Box, and V-funnel tests while mechanical characteristics were measured through compressive strength, split tensile strength, flexure strength and bond strength (pull out) tests. Experimental investigation show that MW and CFs decrease the passing ability and filling ability of SCC. Additionally, Experimental investigation show that MW up to 20% and CFs addition 2.0% by weight of binder tend to increase the mechanical performance of SCC. Furthermore, statistical analysis (RSM) was used to optimize the combined dose of MW and CFs into SCC to obtain high strength self-compacting concrete.

We are interested in modelling and control of a salt gradient solar pond (SGSP) in the south of Tunisia. We developed a model of a Closed Cycle Salt Gradient Solar Pond (CCSGSP) that ensure successful year round operation of the pond. This model was used to study the response of solar pond (SP) to various control technique. It takes into account heat and salt diffusion in the pond and simulates the transient behaviour of a SGSP. Furthermore, we investigated the dynamic process, which involve internal gradient stability, boundary behaviour between gradient zone and convective zones. We thus incorporated the double diffusive processes into the SP model by using the one dimensional stability criterion produced by linear theory. The governing differential equations are solved with a fully implicit technique described by Patankar. The results show that successful operation of a SP requires three things: the maintenance of the storage zone temperature through heat extraction and brine injection, the use of surface washing to control the deepening of the upper mixed layer and a well designed initial salt stratification to prevent the formation of instability within the gradient. Using linear salinity profile as an initial condition, three-year simulations were run using average meteorological data with the result that adequate stability (Rρ > 2 throughout the gradient and Rρ ≅ 10 at the interfaces) was maintained and during the entire year. Numerical results show also that 15 %-30 % efficiency could have been expected if heat extraction is performed routinely especially when one considers that the storage temperature is within 40-80 °C.

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This paper investigates the nonlinear modeling of a smart tensegrity structure of Geiger’s type with active damping using pairs of displacement actuator and force sensor, collocated at the lower end of strings and/or struts. A control strategy based on decentralized collocated integral force feedback is employed. A linear model is first used to optimize the number and the location of the active tendons. A geometric nonlinear dynamic procedure is then used for the analysis of the response of the structure with and without active control. An incremental-iterative solution based on a Newmark direct integration method and a modified Newton–Raphson scheme is adopted for solving the nonlinear equation of motion. For high excitations, the nonlinear dynamic behavior of the smart cable dome is observed and damping is successfully added to the system. The responses with and without control of particular modes are studied in frequency and time domains. The results obtained indicate that the active control strategy presented in this paper is adequate for vibration attenuation of Geiger domes.

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