Civil Engineering Commons^™

Wind Flow Characteristics Of Multi-Vortex Tornadoes And Their Wind Effects On Residential Houses, Yi Zhao

Doctoral Dissertations

"Tornadoes strike the USA very frequently, with an average of 1200 reports per year, and the average annual tornado-induced property loss has reached $10B. The devastation from recent tornadoes have prompted a renewed interest in better understanding tornado dynamics, their interactions with the built environment, and the performance of civil structures during tornadoes. In the past, the wind effects caused by single-vortex tornadoes have been widely studied, while the multi-vortex tornadoes were rarely considered. In fact, many previous deadly, costly tornadoes involved multiple vortices. Therefore, it is important to understand the wind flow characteristics of multi-vortex tornadoes in order to …

The Evacuation Simulation Of Wheelchair Users In A Building Fire: An Initial Dynamic Characterization Of Structural Egress Components, Haley Hostetter

All Theses

People with disabilities are one of the most vulnerable groups involved in building fires. According to the U.S. Fire Administration, in the United States alone, an estimated 700 home fires involve people with physical disabilities each year while over 1700 involve those with mental health disorders. Despite this, the current body of literature shows few studies focused on the evacuation of disabled people. This is a direct result of past and present social injustice on people with disabilities and has resulted in high injury and death rates during fires. To combat this, enrich the literature, and improve their experiences in …

A Comparable Analysis Of Civilian And Military Airfield Runway Design Procedures, Jacob Wessel

Open Access Theses & Dissertations

In the United States there are two primary agencies that regulate, approve, and aid in airfield runway designs. These two agencies are the Federal Aviation Administration (FAA) and the Department of Defense (DOD), and they both have different design procedure for design and construction of their prospective airfield runways. It is important to have a closer look at the design procedures, the reliance of software and how these compare to each other. The primary objective of this research was to conduct a sensitivity analysis of the FAA and the DOD airfield design programs used to aid in the design of …

Evaluation Of The Chloride Ions Penetration Into Concrete Structure With The Surface Penetrants Served In Cold Marine Environment For 20 Years, Yanhua Kuang, Yuki Sakoi Associate Professor, Naoto Takashima Postgraduate, Minoru Aba Professor, Yoichi Tsukinaga Professor,

International Conference on Durability of Concrete Structures

The intrusion of chloride ions in concrete served in the marine environment is the leading cause of corrosion of steel bars. This paper examined the result of a long-term survey on the actual structure (the Tomakomai breakwater) treated with a set of penetrants partly. The survey was conducted twice, in the 12th and 20th years after construction.

The results showed that the penetrants could effectively reduce the penetration of chloride ions into concrete. After using the penetrants, the calculated surface chloride ion concentration was decreased by 5.04%/72.18% (the 12th year/the 20th year). As the service years increase, surface chloride ion …

Efficiency Of Bank Filtration In The Removal Of Cyanotoxins Under Different Levels Of Nutrients, Luke Walkenhorst

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Harmful Algal Blooms (HABs) are an increasing concern not only in Nebraska, but across the world. Increasing global temperatures in conjunction with overuse of synthetic fertilizers are leading causes to the increasing frequency and concern of HABs. In the present work, the effectiveness of simulated bank filtration (BF), as an economical water treatment option, to remove cyanotoxins under different levels of nutrients (nitrates and phosphates) was investigated. Vertical flow-through columns pre-acclimated with two levels of nutrients (e.g., nitrate and phosphate—10 vs. 50 mg/L) were exposed to two different levels of cyanotoxins (10 vs. 75 μg/L). Results from the study confirmed …

Autonomous Vehicles On The Smart Roads: Challenges And Potentials, Laura Cristancho, Baleki Campbell, Mahyar Amirgholy

The Kennesaw Journal of Undergraduate Research

Self-driving vehicles and smart roads are not new concepts. These ideas have been discussed for many years but for much of this time, the required technology was not available to make them a reality. Just recently has our technology caught up to our ideas and we are beginning to see progress towards the realization of the automated highway system. As the transition to a complete automated system is still in progress, this leaves many questions that still need to be answered as well as allowing for novel solutions to be presented. Using modern research papers to formulate a sound basis …

Wetland Soil Development Along Salinity And Hydrogeomorphic Gradients In Active And Inactive Deltaic Basins Of Coastal Louisiana, Amanda Fontenot

LSU Master's Theses

Coastal wetlands provide an abundance of ecosystem services that benefit society, such as essential habitat for commercial species, storm protection, nutrient cycling, and carbon storage. Louisiana faces rapid rates of relative sea level rise (natural subsidence and eustatic sea levels) that threaten wetland survival, which are amplified by a reduction of riverine sediment input. An important determining factor of marsh survival is the formation of wetland platform elevation, known as vertical accretion, which is determined by several processes including sediment deposition & erosion, below ground biomass (BGB) productivity, decomposition of organic matter, shallow & deep subsidence, and soil compaction. Feldspar …

The Effects Of Curing Temperature On The Hydration Kinetics Of Plain And Fly Ash Pastes And Compressive Strength Of Corresponding Mortars With And Without Nano-Tio2 Addition., Dan Huang, Mirian Velay-Lizancos, Jan Olek

International Conference on Durability of Concrete Structures

Incorporation of fly ash in cementitious systems containing ordinary portland cement (OPC) increases their long-term strength and durability. However, replacement of cement by fly ash also reduces the heat of hydration of such systems and reduces early-age strength development. The reduced rate of strength development can increase the risk of durability problems, e.g. scaling, in cases when young concrete is exposed to low temperatures and deicing chemicals. This study investigated the potential of nano-titanium dioxide (nano-TiO₂) particles to modify the hydration kinetics of fly ash pastes and compressive strength development of corresponding mortars cured under low (4°C) and …

End Effect Of Corroded Steel Bar In Concrete Specimen During Corrosion Test By Galvanostatic Method, Peng Zhao, Gang Xu, Qing Wang, Xuan Wang

International Conference on Durability of Concrete Structures

The galvanostatic method is a commonly used accelerated corrosion method in studying the durability of concrete structures caused by steel corrosion. If this method is not adequately controlled, the ends of steel bars will be corroded seriously (this phenomenon is called end effect), which is not common in natural corrosion. How to effectively control the end effect during electrified corrosion is helpful to make the characteristics of electrified corrosion more similar to that of natural corrosion. In this paper, experimental and electromagnetic numerical simulation methods are used to study the influence of cathode and corrosion medium coverage area along the …

Investigation Of Chloride Transportation Mechanism In Reinforced Concrete Specimen Subjected To Eccentric Compression, Yong Dong Yan

International Conference on Durability of Concrete Structures

In order to deal with the chloride ion transportation mechanism in eccentric compressive concrete pier and column in marine environment, stress distribution in the section of eccentric compressive concrete specimen was analyzed firstly, relationship between chloride diffusion coefficient and stress level was developed according to porosity varying under different loads, at last a model of chloride diffusion coefficient under varying stress level was developed. Conversion-diffusion equation in COMSOL Multiphysics was used in this paper to calculate the chloride ion transportation process. Three test beams with different mixture were cast and then loaded to different stress level. After that, all of …

Finite Element Modeling Of Thermal Effect On Airport Slabs, Chuanyue Shen

International Conference on Durability of Concrete Structures

A sub-ground tunnel connecting two concourses of a terminal at Chicago O’Hare International Airport suffered from water leakage. The airport engineers suspected that the problem was caused by high stresses impinging on the tunnel structure by the pavement sections above the tunnel, acting to damage joints and waterproofing membranes that should have prevented such leakage. To provide a fundamental solution to this problem while minimizing the interference with airport operation, a repair strategy needs to be determined based on a clear understanding of the root cause. A preliminary field inspection confirmed that the concrete pavement slabs moved significantly when ambient …

Application Of Multi-Environmental Time Similarity Theory Based On Relative Information (Ri-Mets) Theory In Durability Of Concrete Structures In Marine Chloride Environment, Zhang Kai

International Conference on Durability of Concrete Structures

The Multi-environmental time similarity (METS) method is a testing method that establishes the similarity relationship between the indoor test environment and the on-site environment to evaluate the durability and predict service life of the proposed or under-constructed concrete structure. Based on the METS theory, a similarity ratio of chloride ion concentration and diffusion coefficient between the indoor accelerated environment and the on-site natural environment was established. Then the relative information entropy was introduced into the Multi-Environmental Time Similarity based on Relative Information (RI-METS) theory to consider the time variability of the diffusion coefficient and the surface chloride ion mass fraction. …

Durability Assessment Of Repairing Vertical Cracks In Concrete Using Microbially Induced Calcium Carbonate Precipitation Technique, Chunhua Lu

International Conference on Durability of Concrete Structures

No abstract provided.

End Effect Of Corroded Steel Bar In Concrete Specimen During Corrosion Test By Galvanostatic Method, Peng Zhao, Gang Xu, Qing Wang, Xuan Wang

International Conference on Durability of Concrete Structures

Corrosion of steel bars is the main durability problem of concrete structures, which seriously endangers the safety and service life of reinforced concrete (RC) structures. When studying such problems, the electrifying corrosion method is often used to obtain corroded components. How to effectively control the corrosion area of steel bars is the key to improve the applicability of the corrosion method. In this paper, experimental and electromagnetic numerical simulation methods are used to study the influence of cathode and corrosion medium coverage area along the longitudinal direction on the corrosion area of steel bar before concrete protective layer corrosion cracking. …

Ultra- Ductile Waterborne Epoxy-Concrete Composite Repair Material, Bo Pang, Zuquan Jin, Yunsheng Zhang, Xiaoyun Song

International Conference on Durability of Concrete Structures

With the extension of service time, the building structure is in urgent need of repair and reinforcement due to its deterioration in safety and durability with the years. Normal cement concrete exposes shortcomings such as high brittleness and low flexural-tensile strength for which fails to meet the requirement of construction repairing. In this paper, a novel waterborne epoxy-concrete composite repair material (WECM) was prepared by using self-synthesized water-based epoxy resin based on the molecular structure-activity relationship. The key flexural and tensile performance parameters of WECM were accurately obtained.

Effects Of Organic Corrosion Inhibitors On The Performance Of Repair Mortars, Ominda Nanayakkara Dr.

International Conference on Durability of Concrete Structures

Reinforced concrete (RC) structures are severely degraded due to the corrosion of the embedded reinforcing steel, and hence, the upgrading of RC structures is essential. Repairing mortar is widely used to improve durability and strengthen structures; however, further repairing might be required considering the extended life of the structure. The use of inhibitors to protect the reinforcement from corrosion has become of great interest. Therefore, it is vital to study the potential of using corrosion inhibitors in a newly repaired system.

This study investigated the performance of a commercially available polymer-modified mortar with migrating and admixed corrosion inhibitors. The study …

Corrosion Performance Of Embedded Steel Bar In Cl--Contaminated Limestone Calcined Clay Cement (Lc3) At Initial Stage Of Hydration, Weiwen Li, Zuhua Xu, Yaocheng Wang, Xin Wang, Feng Xing

International Conference on Durability of Concrete Structures

Limestone Calcined Clay Cement (LC3) presents brilliant properties in binding Cl^- so that the embedded steel bars are probably protected in Cl^--contaminated condition, which meets the need of sea sand application. However, the corrosion performance of steel bars embedded in LC3 paste with Cl^‑ is unclear, especially in early age hydration. Thus, a series of experiments were carried out to evaluate the corrosion performance of steel bars on initial and hardened stages of hydration, including concentration of OH^- and Cl^- in real pore solution, open circuit potential (OCP) and chemical elements of steel bars. …

Investigation On The Properties Of Calcium Sulfoaluminate Cement Waterproof Repair Mortar Modified With Ethylene-Vinyl Acetate Powder, Dong Dong

International Conference on Durability of Concrete Structures

本文采用乙烯-醋酸乙烯酯（EVA）粉体和CSA水泥制备了防水修复砂浆，并对其水化和性能进行了研究。结果表明，EVA粉体延长了凝固时间，提高了防水修补砂浆的流动性，使其在实际工程中更容易应用。EVA粉提高了防水修复砂浆的不渗透性，降低了吸水性。虽然EVA粉降低了防水修补砂浆的抗弯强度和抗压强度，但它仍然符合JC/T 2381-2016标准对刚性修复砂浆的要求。EVA粉体降低了防水修复砂浆的收缩率，改善了界面过渡区和拉伸粘接强度、弯曲粘接强度等粘接性能。EVA粉末抑制CSA水泥的水合作用6 h，在3 d水化年龄时抑制作用消失。

Influence Of Biological Sulfuric Acid On Corrosion Mechanism Of Alkali-Activated Cement Concrete, 季 韬 教授

International Conference on Durability of Concrete Structures

生物硫酸对碱活化水泥混凝土腐蚀机理的影响

丁方硕、韬骥、潘伟杰

福州大学土木工程系

抽象的

讨论了不同浓度的生物硫酸对碱活化水泥混凝土（AACC）腐蚀的影响，并以化学硫酸为参考。AACC的质量和抗压强度、孔溶液的pH曲线和Ca ²⁺对其释放进行了研究，并通过 ESEM-EDS 和 XRD 揭示了 AACC 的腐蚀机理。结果表明，在不同浓度的化学硫酸和生物硫酸作用下，AACC的腐蚀产物主要是石膏。随着硫酸浓度的增加，AACC的失重率增加，AACC的抗压强度降低。石膏阻碍化学硫酸进入混凝土。然而，石膏为细菌提供了生存环境，细菌很容易渗透到混凝土中，加速了AACC的破坏。与化学硫酸相比，生物硫酸增加了AACC的质量损失率和抗压强度。

参考

荣H，Wu，C.，Ma，G.，Zheng，X.，和Liu，Z，2021。污水环境下混凝土微生物腐蚀研究进展。中国陶瓷学会学报，49（5）：988-999。

Scholz, F., 1997。微生物影响的材料腐蚀：科学和工程方面。固态电化学杂志，1（2）：181-181。

谢毅，林，X.，吉，T.，2019。普通硅酸盐混凝土与碱活化混凝土在生物硫酸侵蚀下的耐腐蚀机理比较。建筑和建筑材料，228（20）：1-12。

Frost Resistance And Pore Structure Properties Of Mortar Containing Air Entraining Agent Combined With Superabsorbent Polymer, Yanqun Xu, Qiang Yuan

International Conference on Durability of Concrete Structures

The air entraining effect of air entraining agent (AEA) is deeply affected by environment, which will further influence its function of improving frost resistance. To solve this problem, a strategy of using AEA combined with superabsorbent polymer(SAP) to improve the frost resistance of mortar was proposed in this study. Mass loss and relative dynamic elastic modulus of mortar were used to characterize frost resistance of mortar. Air void density, spacing factor, air void distribution and air content were measured to analyze its pore structure properties. The results verify that the combined use of AEA and SAP can improve the frost …