Seismic Behaviour of High-rise Frame-core Tube Structures Considering Dynamic Soil-Structure Interaction

As the population grows and land prices rise, high-rise buildings are becoming more and more common and popular in urban cities. Traditional high-rise building design method generally assumes the structure is fixed at the base, because the influence of soil-structure interaction is considered to be beneficial to the response of structures under the earthquake excitation. However, recent earthquakes and studies indicated that SSI may exert detrimental effects on commonly used structural systems. In this study, a numerical soil-structure model is established in Abaqus software to explore the impacts of SSI on high-rise frame-core tube structures. The seismic response of frame-core tube structures with various structural heights, height-width ratios, foundation types and soil types is studied. The numerical simulation results including maximum lateral deflections, foundation rocking, inter-storey drifts and base shears of rigid and flexible base buildings are discussed and compared. The results reveal the lateral displacement and inter-storey drifts of the superstructure can be amplified when SSI is taking into account, while the base shears are not necessarily reduced. Increasing the stiffness of the foundation and the subsoil can generally increase the seismic demand of structures. It has been concluded that it is neither safe nor economical to consider only the beneficial effects of SSI or to ignore them in structural design practice.

Study on shock absorption performance and damage of a new staggered story isolated system

The new staggered story isolated system is developed according to the base isolated system and the mid-story isolated system. Non-linear finite element model of an eighteen stories new staggered story isolated structure is established. For a comparative analysis, the models of a base isolated structure, a mid-story isolated structure, and an aseismic structure are also established, and their shock absorption performances and damages are analyzed for comparison. The results indicate that the new staggered story isolated structure has a small seismic response, good shock absorption performance which is feasible for application. Besides, the shock absorption performance of the new staggered story isolated structure is a little worse than the base isolated structure but slightly better than the mid-story isolated structure. The bottom of core tube and the story below the frame isolated story have large acceleration response which needs to be paid more attention in design.

Analytical Formulas for Dispersion and Effective Area in Hollow-Core Tube Lattice Fibers

In this work, we propose analytical formulas for the estimation of dispersion properties and effective area of the fundamental mode of hollow-core inhibited coupling fibers with a microstructured cladding composed by a ring of dielectric tubes. The formulas are based on a model which has already been successfully applied to the estimation of confinement loss. The model takes into account the effects of the coupling of the fundamental core mode with the cladding modes in the context of the single-tube approximation. Effective index, group velocity dispersion, and effective area of the fundamental mode are estimated and compared with the results obtained from numerical simulations, by considering ten different fibers. The comparison shows a good accuracy of the proposed formulas, which do not require any tuning of fitting parameters. On the basis of the analysis carried out, a scaling law relating the effective area to the core radius is also given. Finally, the formulas give a good estimation of the same parameters of other Hollow-core inhibited coupling fibers, such as nested, ice-cream, and kagome fibers.

Static Behaviors and Applications of Buckling Monitoring Members with Rigid Ends

The buckling of compression members may lead to the progressive collapse of spatial structures. Based on the sleeved compression member, the buckling monitoring member is introduced to control the buckling of compression member and raise buckling alert by sensing contact between the core tube and the restraining tube. Considering the rigid connection among the members in spatial structures, the buckling monitoring member with rigid ends needs to be further analyzed. An experimental test was conducted and finite element analyses were performed with calibrated finite element models. The results indicated that the ultimate bearing capacity and post-ultimate bearing capacity of the core tube were enhanced due to the restraint from the restraining tube. The contact was successfully sensed by pressure sensor, revealing that it sensed the buckling of the core tube. Parametric studies were conducted, indicating that the core protrusion, core slenderness ratio, the gap between the core tube and restraining tube, and the flexural rigidity ratio are the key parameters affecting the bearing capacity and the failure modes of the buckling monitoring member, and some key values of parameters were proposed to obtain good bearing capacity. Based on the parametric studies, the failure modes of buckling-monitoring members are summarized as global buckling and local buckling. The stress distribution and deformation mode of buckling monitoring members are presented in the non-contact, point-contact, line-contact, reverse-contact and ultimate bearing state. The buckling monitoring member is applied in a reticulated shell by substituting the buckling members. It can effectively improve the ultimate bearing capacity of reticulated shell.

NASA Prepares To Drill for the “Oil of Space”

“We’re going to the Moon, and we’re going there to stay this time,” has become a NASA mantra as the US competes with other countries, including China and Russia (https://jpt. spe.org/esa-roscosmos-to-mine-oxygen-water-from-moon-rocks-as-nasa-eyes-first-artemis-lunar-mission), to be the first to put humans on the Moon and Mars. The race will rely heavily on using resources available on the planetary bodies - or in-situ resource utilization (ISRU). Chief among these is water, which has been called “the oil of space.” As NASA prepares for Artemis mission astronauts to land on the Moon in 2024, it will fly at least two preliminary missions to look for water and gather information about the lunar south pole. The Polar Resources Ice-Mining Experiment (PRIME-1) and Volatiles Investigating Polar Exploration Rover (VIPER) missions, which will be launched in late 2022 and 2023, respectively, will be the first missions to study ISRU on another celestial body. They will also mark the first time NASA will robotically sample and analyze for ice from below the surface. And they will use technologies transferred and adapted from oil and gas exploration. Reconnaissance Missions Data from nearly 3 decades of lunar orbiter and impactor missions suggest that the Moon’s “soils,” particularly at its south pole and other regions, could contain hundreds of millions of gallons of water that could eventually be harvested and converted to oxygen, fuel, or drinkable water for human use on the Moon, Mars, and beyond. But, at what concentrations? In what kinds of soils? And is the water in a form that’s accessible? Most of the information we have about the presence of water-ice on the Moon comes from orbital measurements. The only direct evidence acquired to date came in 2009 from a sensing satellite aboard a spacecraft that was purposely crashed in the Cabeus crater. The material ejected as a result of the impact was analyzed with a spectrometer to reveal the presence of 5.6%±2.9% water-ice by mass. The form, distribution, composition, and quantity of the water-ice remain largely uncertain. The only way to reduce this uncertainty is to obtain ground-truth data by drilling exploratory boreholes in the crater. This will be the purpose of the PRIME-1 and VIPER missions. PRIME-1 will last a week to 10 days, during which a robot will deploy a drill and mass spectrometer to harvest and preliminarily evaluate moon-ice for quality and regional heights and to determine how much of the ice is lost to a process known as sublimation, wherein the water transforms directly from solid ice into vapor, rather than first going through a liquid phase. In addition to ice, PRIME-1 will gather samples including rock samples to help date the sequence of impact events on the Moon, core tube samples to capture ancient solar wind trapped in regolith layers (unconsolidated, inorganic rocky material), and paired samples of material to characterize the presence of volatiles and to assess geotechnical differences between materials inside and outside permanent shadows. The samples will be returned to Earth and studied to characterize and document the regional geology, including the small, permanently shadowed regions. The data from the mission will help scientists understand how a mobile robot to be used on the subsequent VIPER mission can search for water at the Moon’s pole, and how much water may be available to use as NASA plans to establish a sustainable human presence on the Moon by the end of the decade (Fig. 1).

Comparison of seismic performance between typical structural steel buildings designed following the Chinese and United States codes

In this study, comparative investigations of a typical steel moment frame and a steel frame-braced core-tube structure, designed following different seismic codes, are conducted to evaluate the significant differences between the Chinese and the United States (US) seismic codes for steel buildings. The study outcomes can enhance the understanding of the differences in steel structure design between two countries, especially the differences in seismic performance. Specifically, the design outputs of the structural components, material consumptions, dynamic characteristics, and seismic loads were analyzed. Subsequently, finite element (FE) models based on the design outputs were established to assess the seismic performance and collapse margin. Furthermore, the local buckling effect of the steel components can be considered in the FE model, which can effectively predict the buckling-induced strength deterioration under excessive deformation. The comparison results reveal that, under the same design conditions in this study, both the strength requirement and deflection limit are critical factors that control the typical buildings design following the Chinese codes. However, the strength requirement is the primary factor that controls the design outcomes following the US codes. Moreover, the collapse resistance of the steel moment frames from both codes are similar, but the material consumption based on the Chinese design code is comparatively higher. In contrast, the material consumption of the steel frame-braced core-tube structures are comparable, but the collapse resistance of the US design code is better. Furthermore, the collapse analyses indicate that the local buckling effect could significantly reduce the collapse resistance.