The use of discontinuous first and second-order mixed boundary elements for 2D elastostatics

In classical higher-order discontinuous boundary element formulation for two-dimensional elastostatics, interpolation functions for different boundary variables (i.e., boundary displacements and tractions) are assumed to be the same. However, there is a derivational relationship between these variables. This paper presents a boundary element formulation, called Mixed Boundary Element Formulation, for two dimensional elastostatic problems in which above mentioned relationship is taking into account. The formulations are performed by using discontinuous first and second-order mixed boundary elements. Based on the formulations presented in this study, two computer softwares are developed and verified through some example problems. The results show that the present formulation is credible

Use and comparison of different types of boundary elements for 2D soil-structure interaction problems

In this study, the usage and the comparison of some discontinuous boundary elements (constant, linear and quadratic) are investigated for 2D soil-structure interaction (SSI) problems. Based on the formulations presented in this study, some general purpose computer programs coded in FORTRAN77 are developed for each type of discontinuous boundary elements for elastic or visco-elastic 2D SSI problems. The programs perform the analysis in Fourier transform space. The results of 2D dynamic SSI problems are compared with those in the literature. Examples studied here indicate that present formulations have sufficient computational accuracy for analyzing 2D SSI problems. As a result of this study, the use of constant element is more sufficient than the other type of elements. © 2009 Elsevier Ltd. All rights reserved

Influence of dry and wet curing conditions on compressive strength of silica fume concrete

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water-cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450 kg/m3) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20±2 °C with 65% relative humidity (RH), and three other cubic samples were cured at 20±2 °C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water-cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased. © 2005 Elsevier Ltd. All rights reserved