Effect of Water-Cement Ratio on the Compressive Strength of gravel - crushed over burnt bricks concrete.

The research was conducted to study the effect of water-cement ratio on the compressive strength of gravel-crushed over burnt bricks concrete. Trial mixes were prepared using the crushed over burnt bricks as coarse aggregates only (control), mixture of crushed over burnt bricks and river wash gravel as coarse aggregates and river washed gravel as coarse aggregates only (control) at water – cement ratios of 0.4, 0.5,0.55 and 0.6. Cubes of concrete were prepared and tested to study the compressive strength in relation to the water-cement ratio. The results indicate that the concrete having over burnt bricks as aggregates may be termed as medium light weight concrete having a density between 2000-2200 kg/m3 and that by reducing the water-cement ratio from 0.6 to 0.4 increases the compressive strength from by more than 30%. Use of broken over burnt bricks as coarse aggregate for structural concrete is recommended when natural aggregate is not easily available, high strength of concrete is not required and the bearing capacity of the soil is low. Key words: Aggregates, concrete, compressive strength, water-cement ratio, crushed over burnt brick

ASSESSMENT OF SEISMIC INPUT ENERGY BY MEANS OF NEW DEFINITION AND THE APPLICATION TO EARTHQUAKE RESISTANT DESIGN

A methodology for assessing the seismic input energy into structure (building) from earthquake (or seismic) excitation is proposed. The procedure is based on the energy balance of the structure and employs the earthquake intensity characteristic known as the specific energy density (SED) to estimate the maximum input energy. This energy is evaluated for the portion of earthquake record (accelerogram) where strong ground motion occurs (the interval between 5-95% accumulations of the Arias intensity). Comparison of the proposed approach in this paper and other proposals for assessing seismic input energy as a basis for energy-based seismic design methodology is presented. Since a critical condition to realize an energy-based seismic design is that the structure should have a rational relationship between damage/energy absorbed, the procedure establishes a relation between the seismic input energy into structure and strain, total cyclic displacement and low cycle fatigue. Seismic input energy obtained using this procedure is compared with results from other methods for assessment of seismic input energy. The procedure can useful especially, at the initial stage of design to provide the desired ductility to structure since it allows for evaluating the maximum input energy into structural system from any seismic excitation without recourse to dynamic analysis