The interstellar medium is observed in a hierarchical fractal structure over several orders of magnitude in scale. Aiming to understand the origin of this structure, we carry out numerical simulations of molecular cloud fragmentation, taking into account self-gravity, dissipation and energy input. Selfgravity is computed through a tree code, with fully or quasi periodic boundary conditions. Ene...

This study focuses on the shape optimization of concrete gravity dams considering dam–water–foundation interaction and nonlinear effects subject to earthquake. The concrete gravity dam is considered as a two–dimensional structure involving the geometry and material nonlinearity effects. For the description of the nonlinear behavior of concrete material under earthquake loads, the Drucker–Prager...

The results of tests on fifteen four-column frame specimens subjected to progressive unidirectional ground shaking up to collapse are analyzed. Test structure performance is compared with proposed limits for minimizing P-∆ effects in highway bridge piers. The stability factor is found to have a strong relation to the relative structural performance in this regard. Specimens with θ less than 0.2...

The tight correlation between galaxy bulges and their central black hole masses likely emerges in a phase of rapid collapse and starburst at high redshift, due to the balance of gravity on gas with the feedback force from starbursts and the wind from the black hole; the average gravity on per unit mass of gas is ∼ 2×10−10m sec during the star burst phase. This level of gravity could come from t...

Abnormal loads due to natural events, implementation errors and some other issues can lead to occurrence of progressive collapse in structures. Most of the past researches consist of 2- Dimensional (2D) models of steel frames without consideration of the floor system effects, which reduces the accuracy of the modeling. While employing a 3-Dimensional (3D) model and modeling the concrete slab sy...