Ultra high toughness cementitious composite (UHTCC) usually shows strain hardening and multiple cracking under static tension loads. In practice, structures could be exposed to high strain rates during an earthquake. Whether UHTCC can maintain its unique properties and provide high structural performance under seismic loading rates largely determines whether it can successfully fulfil its intended function. To determine the rate dependence of UHTCC, uniaxial tensile tests with strain rates ranging from 4×10⁻⁶ s⁻¹ to 1×10⁻¹ s⁻¹ were conducted with thin plates. The experimental results showed that UHTCC had significant strain hardening and excellent multiple cracking properties under all the rates tested. The ultimate tensile strain lay in the range of 3.7% to 4.1% and was almost immune to the change in strain rates. The rate of 1×10⁻³ s⁻¹ seemed to be a threshold for dynamic increase effects of the first crack tensile strength, elastic modulus, ultimate tensile strength, and energy absorption capability. When the strain rate was higher than the threshold, the dynamic increase effects became more pronounced. The energy absorption capability was much higher than that of concrete, and the average ultimate crack widths were controlled below 0.1 mm under all rates. Several fitting formulas were obtained based on the experimental results.

The efficiency of a long-span structure relies on how material is locally distributed within a fixed structural shape. In this paper a design procedure for thin plates made of three layers of a depleted material subject to a distributed vertical load is proposed. The investigation is driven by the idea of the optimal material organization and has the objective of maximizing the overall stiffness/weight ratio of the structure. Two microstructural architectures of the media are considered: a porous solid structure and a truss arrangement. For each type of microstructure the flexural stiffness has been correlated to the level of depletion by the use of a power law function by setting very few parameters. Finally, invoking the principles of structural homogenization theory, the global flexural response of the plate has also been calculated. The validity of the method is demonstrated by comparing the analytical results with those obtained by a numerical finite element simulation of the structure based on a detailed model of the media.

Pressure pipes are widely used in modern industry with some in potentially dangerous situations of explosion and impact. The security problems of these pipes when subjected to impact have attracted a lot of attention. A non-linear numerical model has therefore been developed to investigate the dynamic behavior of pressure pipes subjected to high-velocity impact. A high strain rate effect on the pipe response is considered here and the fluid and pipe interaction is modeled to include the coupling effect between the deformation of the pipe and its internal pressure. Low-velocity and high-velocity impact experimental results are used to verify the numerical model, and a reasonable agreement between the numerical and experimental results has been achieved. The effects on the dynamic behavior of the pipes of the nose shape of the projectile, the diameter of the spherical projectile, and the pipe wall thickness and internal pressure, are investigated quantitatively. During high-velocity impacts, the increase of pressure in the pipes decreases their resistance to perforation. A rise in internal pressure increases the elastic resistance of the pipes toward impacts without crack formation.

The pressurized reservoir is a closed hydraulic tank which plays a significant role in enhancing the capabilities of hydraulic driven robotics. The spring pressurized reservoir adopted in this paper requires comprehensive performance, such as weight, size, fluid volume, and pressure, which is hard to balance. A novel interactive multi-objective optimization approach, the feasible space tightening method, is proposed, which is efficient in solving complicated engineering design problems where multiple objectives are determined by multiple design variables. This method provides sufficient information to the designer by visualizing the performance trends within the feasible space as well as its relationship with the design variables. A step towards the final solution could be made by raising the threshold on performance indicators interactively, so that the feasible space is reduced and the remaining solutions are more preferred by the designer. With the help of this new method, the preferred solution of a spring pressurized reservoir is found. Practicability and efficiency are demonstrated in the optimal design process, where the solution is determined within four rounds of interaction between the designer and the optimization program. Tests on the designed prototype show good results.

The traditional laboratory models for the hydroelasticity and seakeeping performance of ships are tested in calm water and in uni-directional, artificially generated waves. A new alternative to the tank model measurement methodology is to conduct experiments using large-scale models in actual sea conditions. To implement the tests, a large-scale segmented self-propelling model and testing system were designed and assembled. A buoy wave meter was adopted to record the coastal waves that the model encountered during the tests. The analysis of the results of waves in sheltered waters by the spectral method shows good agreement with ISSC spectra. To investigate the difference between this new methodology and the traditional towing tank tests, a small-scale model, whose type and configuration are the same as those of the large-scale model ship, was used and tests were conducted in a towing tank. Comparison of the two experimental results shows that there is a remarkable difference in the response characteristics between the large-scale model at sea and the small-scale model in the tank. Numerical simulations of the responses of the ship under equivalent sea states were also carried out. The influence of directional spreading functions on the results was analyzed by a numerical approach. The classical model tests under long-crested waves in the towing tank over-estimate the motion and wave load responses; however, large-scale model tests carried out at sea are more reasonable for ship design and scientific research.

Adding thin compartmental plates near the internal walls of enclosures has been numerically modeled using the lattice Boltzmann method. This practice was found to be an effective way to further suppress the disadvantageous effects of heat leak, along with the application of insulation materials on the external surfaces. A modified extrapolation scheme for handling the thermal boundary of the thin plate was proposed and verified by comparison with the conventional coupled boundary scheme. The simulation of the natural convection during the cooling down processes and at steady states in the enclosure indicates that the existence of the plates leads to a higher cooling rate and a more favorable temperature uniformity. For a typical case, the one with plates takes 6% less time to reach the halfway point of the steady state and has 26% less temperature variance. Effects by the plates’ positions and sizes were parametrically investigated, in order to find an optimal geometrical configuration. In addition, the fluid’s intrinsic characteristics and the relative heat leak by using the Rayleigh number and Nusselt number, respectively, have been discussed in detail through hydrodynamic and convective heat transfer analyses.