Study on Parameter Optimization and Mechanism of Rigid-Flexible Coupling Underground Engineering Structure of Steel Panel and Polymer

Polymer grouting is carried out between the steel panel and surrounding soil in underground engineering, and the polymer material consists of isocyanates and polyols. The isocyanate/polyol composite slurry expands rapidly due to chemical reaction and solidifies immediately. Then, a dense impermeable polymer layer is formed after rapid expansion of isocyanate and polyol, which is widely used for ground reinforcement and foundation remediation. Thus, a steel panel-polymer composite structure is developed. Mechanical properties of the steel panel-polymer structure are studied. The results show that the steel panel-polymer structure exhibited excellent mechanical properties. The steel panel and polymer layer should be designed above 3 mm and 10 mm in thickness, respectively. The steel panel showed superior mechanical properties to those of polymer layers. Considering good rigidity of the steel panel and good flexibility of the polymer layer, the steel panel and polymer layer presented perfect interfacial contact. It is concluded that the mechanical properties of the whole structure were increasingly enhanced with the increase of the steel panel thickness and the structural flexibility increased with the thickness of the polymer layer. Besides, the combination of the steel panel and polymer layer could also improve the mechanical properties of this coupling structure. This study provided an initial attempt for investigating the feasibility of applying polyurethane foam to steel panels in underground engineering. The stress analysis along the grouting direction inside the prefabricated wall was conducted. It may lay the foundation for further application of polymer grouting in underground engineering.

Canola Oil based Poly (Ester–Ether–Amide–Urethane) Nanocomposite and Its Anti-Corrosive Coatings

The environmental and health hazards associated with petro-based chemicals have motivated the researchers to replace them partially or wholly with renewable resource-based polymers. Vegetable oils serve as an excellent alternative to this end as they are cost effective, eco-friendly, easily available and rich with functional groups amenable to chemical reactions. The aim of the research work is to prepare Canola oil [CANO] derived poly (ester–ether–amide–urethane) (CPEEUA) nanocomposite coating material using N,N-bis (2-hydroxyethyl) fatty amide [CFA] obtained from CANO, Lactic acid [LA], and reinforced with Fumed Silica [FS]. CPEEUA was obtained by esterification, etherification, and urethanation reactions and its structure was confirmed from FTIR and NMR spectral analyses. CPEEUA/FS coatings were found to be scratch resistant, flexible, well-adhered to mild steel panels, and hydrophobic with 2.0–2.5kg scratch hardness, 150lb/inch impact resistance and >90° contact angle value. They exhibited good corrosion protection in 3.5 wt% NaCl solution as investigated by Potentiodynamic Polarization and Electrochemical Impedance tests. CPEEUA coatings are safe for usage up to 200 °C.

Potential Disruptive Effects of Copper-Based Antifouling Paints On The Biodiversity of Coastal Macrofouling Communities

In recent years, after the ban on tributyltin (TBT)-based antifouling paints, copper-based paints have become the main coatings for boat hulls due to their efficiency and endurance. Copper(I) compounds like Cu2O and CuSCN are used alone or in combination with booster biocides, i.e. Irgarol 1051, chlorothalonil and dichlofluanid. The expanded use of these paints has increased copper leaching into coastal environments, requiring attention and legislative restrictions for potential long-term effects on benthic populations. This study monitored the ecological succession of macrofouling communities on wooden and stainless steel panels immersed for 10 months in the southern basin of the Lagoon of Venice. The development of macrofouling communities on the panels coated with copper-containing antifouling paints was compared with those on the reference (uncoated) and TBT-coated panels. Series of biodiversity descriptors highlighted the preventing activity of the antifouling paints. The most active paints were those containing booster biocides and with self-polishing copolymers in the matrix. The macrofouling communities appeared dissimilar to those on the reference uncoated panels as regards the species richness, the coverage areas, and the biocoenosis structure. Generally, green algae, bryozoans and barnacles were the most tolerant taxa and a negative species selection occurred for sponges, serpulids and ascidians.

The Application of UVC Used in Synergy with Surface Material to Prevent Marine Biofouling

Biofouling is problematic for the shipping industry and can lead to functional and financial setbacks. One possible means of biofouling prevention is the use of ultraviolet-C (UVC) light. Previous studies have investigated UVC with marine coatings, but the synergistic effect with color and surface material, specifically reflectance, has yet to be determined. This study comprised three parts: UVC and color (red vs. white), UVC and reflectance (stainless steel vs. polycarbonate), and UVC and exposure intervals (weekly intervals and 10 min intervals). There was no variance in the biofouling communities for colored surfaces when exposed to 254 nm UVC. Reflectance studies demonstrated that the surface material plays a role in biofouling settlement. Stainless steel panels had significantly greater macrofouling settlement than polycarbonate, specifically among encrusting bryozoan, tubeworms, and tunicate communities. Panels of both surface materials exposed to indirect UVC significantly differed from controls and those exposed directly to UVC. Exposure intervals were also found to reduce biofouling settlement especially with long frequent intervals (i.e., 10 min/day). UVC can be utilized on various colored surfaces and different surface types, but the effectiveness in preventing biofouling is ultimately determined by the duration and frequency of UVC exposure.

Boomerang and Jungle Bridges: Connecting City and Forest

<p>The Boomerang and Jungle pedestrian bridges form part of a new pedestrian and cycle path, passing from the centre of Oslo through an urban forest and over the Outer Ring Road. The main goal for the design team was to integrate the bridges’ architecture within the natural environment and to cause the minimum impact during the construction period. The 85m long Boomerang bridge, named after its shape in plan, crosses the ring road with a 22.5m span, whose traffic was maintained throughout the construction period. In total the bridge comprises of four spans, with a continuous steel box girder of asymmetric cross-section. The bridge and the railings are fabricated from Cor-ten weathering steel to avoid the need for painting and to minimise future maintenance. The Jungle Pedestrian bridge is a simple suspension bridge spanning 36m over a small river. The main structural elements are parabolic, locked coil cables, four at deck level and two at handrail level. The deck is formed from slip-resistant perforated steel panels, supported off a transversely stiff steel framing system. The design intent was to maximize the use of prefabricated lightweight elements to facilitate the bridge erection and minimize the impact on the natural environment. Due to the lightness of the bridge a detailed analysis of the accelerations due to pedestrian-induced vibrations was performed to assess the comfort level for bridge users. The project won in 2017 the Norwegian Steel Construction Award and was nominated for World Architecture News’ Best Bridge Award 2017.</p>

Performance Evaluation of Rigid Braced Indirect Suspended Ceiling with Steel Panels

In Korea, the earthquakes in Gyeongju (2016) and Pohang (2017) have led to increased interest in the seismic design of nonstructural elements. Among these, the suspended ceiling can cause personal injury and property damage. In addition, most suspended ceilings that are used in Korea neither have seismic design details nor meet the current seismic design standards. There are two seismic design methods for suspended ceilings using a perimeter clip and a brace. In the United States and Japan, seismic design of ceilings is typically used, but the concepts of applying and installing braces are different. This is because the typical ceiling systems are different in the United States and Japan. In this study, a brace-applied ceiling system that is suitable for a suspended ceiling with a steel panel was applied in the indirect suspended ceiling mainly used in Korea. In addition, the seismic performance was verified through a shaking table test. All the specimens were applied with anti-falling clips that are designed to prevent the panels from falling, and they satisfy KDS 41 17 00, which is a Korean seismic design life safety standard. Without considering these factors, the performance level is lower than a nonseismic designed ceiling, which is not properly designed or constructed.

Risk evaluation of ballistic penetration by small caliber ammunition of live-fire shoot house facilities with comparison to numerical and experimental results

The development of advanced small caliber weapon systems has resulted in rounds with more material penetration capabilities. The increased capabilities may mean that existing live-fire facilities will no longer be adequate for the training and certification of military and law enforcement personnel. Constraints on training in many live-fire shoot house facilities are already in place, with some allowing only single round impact during training. With little understanding of the probability of perforation, or failure, of existing containment systems, this study evaluates risk by studying the single round impact of small caliber ammunition against live-fire shoot house containment systems constructed from AR500 steel panels with two-inch ballistic rubber covering. An analytical and numerical study was conducted using an existing model for steel penetration developed by Alekseevskii-Tate and the EPIC finite element code. A modified form of the advancing cavity model for the ballistic resistance of the target material was used to account for the relatively unconfined material resulting from the studied impacts. These results are then compared to experimental tests conducted by Goodman for rounds of various small calibers impacting live-fire facility containment systems. Projectile and target characteristics were then modeled as continuous random variables, and Monte Carlo simulations were conducted using the validated analytical model to estimate the probability of a single round impact perforating the live-fire facility containment system. An importance sampling scheme was used to reduce the variance of the solution and provide a more accurate estimate of the probability of failure. The Alekseevskii-Tate model was found to provide accurate estimates of the depth of penetration when compared to experimental and numerical results at ordnance velocities and an estimate of the probability of failure is on the order of 1x10-5. This study provides useful tools for the analysis of existing live-fire facilities against future and existing ammunition, and for the design of new facilities. When coupled with Monte Carlo simulation techniques, a risk-based approach to certify live-fire facilities for use with any variety of small arms ammunition can be applied.