In this work, polynomial deflection expression was used in the free-vibration investigation of thick rectangular plates with two different boundary conditions; one with its four edges clamped denoted with the acronym (CCCC) and another with two adjacent edges fixed and having simple supports at the other two adjacent edges denoted with the acronym (CCSS). The edge conditions of the various plates were fulfilled and used in generating the stiffness coefficients which were substituted into the analytical equation to obtain the non-dimensional frequency functions for the plates at different span-depth ratio (a/t) and aspect ratio (b/a). It was observed that at the same value of (b/a), there is an increase in the value of the non-dimensional frequency parameter as (a/t) increases. Also, at the same value of (a/t), there is a decrease in the value of the non-dimensional frequency parameter as (b/a) increases. The results obtained for the all edges clamped plate were compared with similar works by other researchers in the literature and were found to follow similar pattern and trend and were quite close.
This work examined the structural properties of concrete obtained bypartially replacing cement with sawdust ash. The sawdust ash which is apozzolan was obtained by burning sawdust which is a waste product fromprocessing of timber in an open air. The burnt ash was passed through a150 µm metric sieve to obtain the ash used. Physical and chemical analysiswere performed on the ash to verify its suitability as a partial substitute forcement in concrete. Chemical analysis was also carried out on the OrdinaryPortland Cement (OPC) sample. Concrete mixes were produced by replacing OPC with 0%, 5%, 10%, 20% and 30% of Sawdust Ash (SDA). Bothfresh and hardened properties of the concrete produced were investigated.The chemical investigation on the ash showed that it contained most ofthe basic compounds found in OPC making it suitable to serve as a partialsubstitute for OPC in concrete. Investigation on the concrete showed thatboth the workability and density of the concrete reduce as the SDA contentincreases. Analysis on the hardened concrete revealed that the compressivestrength of the concrete decreases as the ash content increases for the earlyages of curing. However, from 21 days curing age upwards, the compressive strength decreases as SDA increases up to 10% of SDA at which thecompressive strength jumped to a maximum value, and then starts reducingagain as the percentage SDA increases. Thus, the SDA concrete gained rapid strength at later ages indicating its pozzolanic activity.
This study applied polynomial expressions as displacement and shear deformation functions in the free-vibration study of thick and moderately thick isotropic rectangular plates. Rectangular plates with two different edge conditions investigated in this work are: one with simple supports at three of its edges and with no support at the other edge denoted with the acronym (SSFS) and a rectangular plate with simple supports at opposite edges while the other opposite edges has a fixed support at one edge and no support at the other edge, this is denoted with the acronym (CSFS). The total potential energy of the plate was derived using the general theory of elasticity. The general governing equation of the plate was derived by minimizing the total potential energy equation of the plate. Edge conditions of the SSFS and CSFS plates were met and substituted into the general governing equation to obtain a linear expression which was solved to generate fundamental natural frequency function for the plates with various span-depth proportion (m/t) and planar dimensions proportion (n/m). The results obtained from this research were found to agree favourably with the results of similar problems in the literature upon comparison.
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