A study on reactivity of four different Circulating Fluidized Bed Combustion (CFBC) fly ashes has been realized in the presence of water. Paste of each ash was prepared and analyzed for its setting time, expansion and strength. The products of hydration, and their evolutions over a period of time were identified by X-ray diffraction and differential thermal analysis. The results of this study show that the reactivity of the CFBC fly ashes is strongly related to their chemical composition, essentially to their quantity of silica, alumina, lime and sulfate, which promote principally the formation of ettringite, gypsum and C-S-H. It is further noted that the intensity and the proportion of these phases determine the hydration behavior of the CFBC fly ashes.

This paper presents a site-specific seismic hazard study to determine the recommended seismic design criteria for Suramadu Bridge. The study is performed using probabilistic seismic hazard approach to determine maximum acceleration and response spectra at bedrock and followed by local site effect analysis to determine maximum acceleration and response spectra at ground surface. The probabilistic seismic hazard analysis (PSHA) is carried out using 3-dimension (3-D) seismic source models (fault source model). Two hazard levels are analysed to represent 150 and 3,300 years return period of ground motion around site location. The local site effect analysis is performed using 1-dimension (1-D) shear wave propagation theory to obtain peak ground acceleration and response spectra at ground surface. Finally, the site-specific surface response spectra with 5 percent damping are developed based on the mean plus one standard deviation concept from the result of local site effect analysis.

Following a 25-1 fractional factorial design concept, an experiment was planned ; sixteen experimental mixes were calculated from a basic mix (cement : sand : aggregates : fly ash = 1 : 1.3 : 2.6 : 0.8 and W/C ratio of 0.37) and determined changes (cement = 0.1 ; sand = 0.1 ; aggregates = 0.2 ; fly ash = 0.04 and changing W/C ratio by 0.01) using Taguchi’s orthogonal array. Samples were made from each data point. Compressive strength and water absorption were determined after each of two curing conditions (a) 28 days in the water, (b) 28 days in the water and 32 days in the air after that. Mix no 12 [Cement : Sand : Gravel : Fly Ash = 0.9 : 1.2 : 2.8 : 0.76] was found to have highest compressive strength and lowest water absorption.

Elastic analysis of continuos composite beams, assumes constant second moment of area constant over the length of the beam, giving hogging moment at internal supports higher than sagging moment at midspan. This certainly is not favorable because the contribution of concrete slab should be ignored in calculating moment resistance at the internal support. Where elastic analysis is used, alternative economic design is achieved with redistribution of moments from the internal support to the midspan. This paper considering the influence of negative moment inertia to moment redistribution shows that moment redistribution is influenced by the ratio of ultimate positive bending moment to positive bending moment capacity (Mu+/Mkap+). The smaller the ratio (Mu+/Mkap+) the bigger the allowed moment redistribution. Some graphs to calculate the amount of moment redistribution that can be allowed are also presented. Abstract in Bahasa Indonesia : Pada perencanaan balok komposit menerus secara elastis momen enersia sepanjang balok dianggap sama, sehingga momen negatif yang terjadi di daerah tumpuan lebih besar daripada momen positif yang terjadi di lapangan. Hal ini tidak menguntungkan karena kontribusi pelat beton pada daerah momen negatif tidak dapat diperhitungan. Salah satu alternatif untuk memperoleh desain yang lebih menguntungkan dilakukan dengan redistribusi momen dari daerah tumpuan ke daerah lapangan. Makalah ini dengan memperhatikan pengaruh momen inersia negatif terhadap redistribusi momen, menunjukkan bahwa besar redistribusi momen yang dapat dilakukan dipengaruhi oleh rasio momen ultimate positif yang terjadi sebelum redistribusi (Mu+) terhadap kapasitas momen lentur positif penampang (Mkap+). Makin kecil rasio (Mu+/Mkap+) makin besar redistribusi yang dapat dilakukan. Tulisan ini juga menyajikan alat bantu berupa grafik untuk menentukan besarnya redistribusi momen.