A new small-celled diatom from Brazil - Luticola minutissima sp. nov., with comparison to the type of the Antarctic L. neglecta Zidarova, Levkov & Van de Vijv

The samples for this study were collected from terrestrial mosses and lichens growing on palm tree trunks and concrete walls in the city of Rio de Janeiro, south-eastern Brazil. During the investigation on diatom diversity, a new species from the genus Luticola was found. The new species occurred individually at all sampling sites. The aim of this paper is to provide a morphological and ecological description of Luticola minutissima sp. nov. from an aerophytic environment. The species is characterized by a small valve size (5.2–16.8 μm length and 3.7–4.4 wide) and abruptly hooked proximal raphe endings (ca. 90-degree angle). Additionally for comparison, type material of the most similar species, Luticola neglecta Zidarova, Levkov & Van de Vijver, was studied and new information for the ultrastructure of the latter species is provided as well.

Analytical Model Formulation of Steel Plate Reinforced Concrete Walls against Hard Projectile Impact

Steel plate reinforced concrete (SC) walls can effectively resist projectile impact by preventing the rear concrete fragments flying away, thus attracting much attention in defence technology. This work numerically and analytically investigated the hard projectile perforation of steel plate reinforced concrete walls. Impact resistance theories, including cavity expansion analysis as well as the petaling theory of thin steel plates were used to describe the cratering, tunneling and plugging phases of SC walls perforation. Numerical modeling of SC walls perforation was performed to estimate projectile residual velocity and target destructive form, which were validated against the test results. An analytical model for SC wall perforation was established to describe the penetration resistance featuring five stages, i.e., cratering, tunneling and plugging, petaling with plugging and solely petaling. Analytical model predictions matched numerical results well with respect to projectile deceleration evolution as well as residual velocity. From a structural absorbed energy perspective, the effect of front concrete panel and rear steel plate thickness combinations was also studied and analyzed. Finally, equivalent concrete slab thickness was derived with respect to the ballistic limit of SC walls, which may be helpful in the design of a protective strategy.

Structural grouting of load-bearing precast concrete elements: Issues and solutions

The purpose of this paper is to raise construction industry awareness regarding structural grouting of precast concrete projects in the United States. Incidents related to structural grouting have occurred with both precast concrete systems and other building systems. Designers, architects, owners, insurance carriers, and the construction industry in general are becoming increasingly aware of deficient grouting installation methods and verification procedures. Concerns include the timeliness of grout installation during the erection process, the lack of grout on some components of finished projects, and the poor quality of installed grout. These concerns pertain to horizontal connection joints of critical load-bearing elements between foundations and precast concrete columns and walls, stacked precast concrete columns, and stacked precast concrete walls. Current building codes and standards provide no requirements and limited guidance for the installation or special inspection of these critical horizontal joints. In an effort to address this gap in building codes and standards, as it specifically relates to precast concrete structural products, some precast concrete producers and erectors are implementing several strategies and new procedures, as noted and further developed in this paper.

Shielding Effectiveness and Impact Resistance of Concrete Walls Strengthened by High-Strength High-Ductility Concrete

Following the fourth Industrial Revolution, electronic and data-based technology is becoming increasingly developed. However, current research on enhancing electromagnetic interference (EMI) shielding and the physical protection performance of structures incorporating these technologies is insufficient. Therefore, in this study aiming for the improvement of EMI shielding and structural performance of structures, twelve concrete walls were fabricated and tested to determine their shielding effectiveness and drop-weight impact resistance. Concrete walls strengthened by three thickness types of high-strength, high-ductility concrete (HSDC) have been considered. The test results showed that the shielding effectiveness with strengthening thickness increased by approximately 35.6–46.2%. Specimens strengthened by more than 40% and 10% of the strengthening area ratio of single- and double-layer, respectively, exhibited more than 20 dB of shielding effectiveness. Moreover, the relationship between the damaged area ratio and shielding effectiveness was evaluated by means of the drop-weight impact test. The structural performance and EMI shielding effectiveness improved as the HSDC thickness increased.

Study on sliding stability of porous-concrete retaining wall model test subjected to rainfall infiltration

The common disadvantage of a conventional retaining wall is a heavy object as a block that is difficult to lift and handle conveniently. A drainage pipe is commonly used to displace water from the backfill. In areas with high annual rainfall, the soil could be saturated in a short time and added lateral load significantly. In this study, porous concrete was utilized as a retaining wall material with the advantages of the lighter weight of the block and additional drainage capability due to its high void ratio. A set of a laboratory-scale retaining walls using conventional and porous concrete walls was investigated through three different rainfall modes. To initiate the instability condition, a vertical load was applied then the lateral moving was recorded using LVDT sensors. Soil moisture content sensors recorded hydrologic responses of the saturation process. The loading test results showed that the porous concrete wall model was being displaced less than experienced by the conventional concrete wall. It shows that the porous concrete wall model can withstand the load as the additional lateral load from infiltrated rainwater dissipates rapidly. Therefore, the porous concrete wall has the advantage of being used as a Retaining Wall Material.

The End of the Sea Wall

<p>With climate change becoming more widely understood, we are beginning to see how this phenomenon is impacting on our ability to live coastally. Coastal properties represent some of the most expensive real estate in the country, however these properties are being battered by increasing storm surges causing coastal erosion and decay to the land on which they sit. This is resulting in people fighting to keep their homes out of the water, along with an increasing need for a solution to keep the water out of their homes. In Raumati, sea walls began appearing in the 1950s with people blocking their individual properties from the ocean with wooden log walls. These walls have continued to get larger, higher and more solid until they have become the rock accumulation, stone path and concrete walls that stand today along almost the entire length of the Kapiti Coast. The impact of such walls is that, while they protect the land immediately behind them, they cause greater issues further down the coast, causing sections of the coastline to deteriorate at a far more accelerated rate. The aim of this project will be to put an end to the Kapiti sea wall by addressing the site at the southern end of Raumati where this erosion is becoming increasingly evident. Here, the delicate sand dunes are being eaten away by heightened storm surges and an ever-increasing sea level. Rather than looking at it as a negative effect, this thesis will explore the opportunities that are opened by this decay. The project proposes the reinstating and re-wetting of the once drained wetlands that lie behind the natural dunes. Above these wetlands, a ranger’s hut will act as a home, embassy and church within Queen Elizabeth Park. This allows for a greater sense of custodianship, with more people coming, going and staying within the park. The project outcome will be a building that combines public and private spaces. It will allow for the fluctuation in sea levels to interact with and become a part of the building, rather than being excluded through traditional approaches to dealing with climate change on coastlines. Hence, this ranger’s hut will put an end to the sea wall.</p>