Civil Engineering Commons^™

Optimizing Chlorine Disinfection By Chlorine Injection Location And Pipe Diameter Selection In A Water Distribution System, Margaret Neff

Dissertations, Master's Theses and Master's Reports

Due to a variety of factors chlorination is common water disinfectant for community-scale distribution systems. The town of Suyo, Peru was already equipped with a gravity fed water system and drip chlorinator which achieved 4-log inactivation of viruses throughout the town, however, it was not providing 3-log inactivation of giardia cysts at all points of the system.

This project used an EPANET model to determine and compare the potential benefits of changes which could be made to the pre-existing water system in Suyo.

The model was used to compare current operating conditions of the Suyo system, 1.5 mg/L chlorine addition …

การพัฒนาคอนกรีตมวลเบาระบบเซลลูล่าผสมเส้นใยปาล์มน้ำมันและถ่านชีวภาพ, ปาณิศา แสงแก้ว

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้ได้ทำการพัฒนาคอนกรีตมวลเบาระบบเซลลูล่า (Cellular Lightweight Concrete; CLC) โดยใช้วัสดุเหลือใช้ทางการเกษตร 2 ชนิด ได้แก่ เส้นใยปาล์มน้ำมันและถ่านชีวภาพ กลุ่มตัวอย่างทดสอบแบ่งออกเป็น 4 กลุ่ม ได้แก่ คอนกรีต CLC แบบปกติ, คอนกรีต CLC ผสมเส้นใยปาล์ม, คอนกรีต CLC ผสมถ่านชีวภาพ, คอนกรีต CLC ผสมเส้นในปาล์มและถ่านชีวภาพ จากผลการศึกษาพบว่า สัดส่วนเส้นใยปาล์มที่เพิ่มขึ้นส่งผลให้ความหนาแน่น กำลังอัด กำลังดึง การถ่ายเทความร้อนของคอนกรีต CLC สูงขึ้น แต่อัตราส่วนการดูดซึมน้ำลดลง สัดส่วนของถ่านชีวภาพที่เพิ่มขึ้นส่งผลให้ความหนาแน่นเปลี่ยนแปลงเล็กน้อย กำลังอัด กำลังดึง สูงขึ้น อัตราการดูดซึมน้ำและการถ่ายเทความร้อนลดลง งานวิจัยนี้ยังศึกษาความเป็นไปได้ในการใช้งานด้านคุณสมบัติและเศรษฐศาสตร์เบื้องต้น พบว่า กลุ่มตัวอย่างที่เหมาะสมในการนำไปใช้งานมี 2 กลุ่ม ได้แก่ คอนกรีต CLC (โฟมร้อยละ 50) ผสมถ่านชีวภาพร้อยละ 15 และคอนกรีต CLC (โฟมร้อยละ 60) ผสมเส้นใยปาล์มและถ่านชีวภาพร้อยละ 1.5 และ 10 กลุ่มตัวอย่างทั้งสองกลุ่มมีคุณสมบัติผ่านเกณฑ์มาตรฐาน มีความสามารถถ่ายเทความร้อนได้ต่ำ ซึ่งช่วยประหยัดการใช้พลังงานเครื่องปรับอากาศภายในอาคารได้ ในด้านเศรษฐศาสตร์เบื้องต้นสามารถลดต้นทุนในการผลิตได้และมีประโยชน์ในการลดค่าใช้จ่ายในการกำจัดของเสียต่อปี ดังนั้นการนำวัสดุเหลือใช้ทางการเกษตรมาเป็นส่วนผสมในคอนกรีต CLC นั้น จึงช่วยพัฒนาคุณสมบัติบางประการหากใส่ในปริมาณที่เหมาะสม เป็นแนวทางในการกำจัดของเสียและสามารถพัฒนาต่อยอดการผลิตคอนกรีต CLC ได้ในอนาคต

Influence Of Mix Design Parameters On Performance Of Balanced Asphalt Mixtures, Luiza Helena Barros

Open Access Theses & Dissertations

With the popularity of the Balanced Mix Design (BMD) concept, the need for performance tests that can reliably evaluate the cracking and rutting potentials of asphalt concrete (AC) mixes has become more critical. A great deal of effort has been focused on incorporating test methods that can potentially improve the current AC mix-design processes and consequently screen underperforming AC mixes. However, the influence of mix design parameters on the performanceof BMD mixes that provide pavement engineers and designers with thorough guidelines and a reliable and consistent test protocol has not been extensively documented.

This Thesis presents an experimental evaluation of …

Optimization For The Allocation Of Funds For Pavement Maintenance In Pavement Management Systems, Armando Ramirez

Open Access Theses & Dissertations

Pavement maintenance and rehabilitation are critical and costly elements for highway agencies. A challenge for transportation agencies is to preserve roadways in an appropriate condition and extend the pavement service life while maintaining the safety and satisfaction of its users, and maximize the benefits obtained by the repair investments. Pavement maintenance programming is increasing in complexity due to limited resources and increments in traffic and population. Management decisions are usually based on personal judgment by pavement managers and sometimes those decisions are not even supported by previous experience. Research shows that optimization methods can produce significant benefits when transportation agencies …

Investigation Of Ribbed Dome Including Tuned Mass Damper, Ali Parva

Civil & Environmental Engineering Master's Projects

This research report presents the outcome of an investigation of lightweight ribbed steel dome structure. The proposed ribbed dome structure is studied both numerically and experimentally under static, natural vibration, and base excitation conditions. The base excitation is considered in the form of a sinusoidal as well as seismic loading in the form of a scaled-down 1940 El Centro earthquake. A numerical study of the ribbed dome is also conducted including a tuned mass damper (TMD). The performance of the dome is also compared with that of a hexagonal vertical structure showing a superior response of the dome under seismic …

A Quality Control Performance-Based Methodology For Pavement Management Systems, Edgar Daniel Rodriguez Velasquez

Open Access Theses & Dissertations

Transportation Asset Management is a decision-making process, which allocates available resources for operating, maintaining, enhancing, and expanding transportation infrastructure while considering its entire life cycle. Transportation infrastructure includes different types of assets and pavements are one of the main assets due to its social, economic, and environmental impacts to society. Transportation agencies implement Pavement Management Systems to support the pavement management process. While implementing and operating a Pavement Management System, one of the costliest procedures is collecting pavement condition data from the field. Good quality for pavement condition data is required to select the right preservation treatments, estimate the associated …

Understanding The Consequences And Costs Of Climate Change On Texas Pavements, Megha Sharma

Open Access Theses & Dissertations

Over the several centuries, the global temperatures have been rising, and the rate of rising in temperature has increased significantly in the last century. The increase in temperature and precipitation can substantially influence performance life of pavements because of their continuous exposure to climate. The climate parameters like temperature and precipitation are considered in the pavement design to reflect the influence of climate factors on the performance of the pavements. Currently, designers use the historical weather patterns while designing pavements. Since the climate is changing, the estimated service life of the pavement will be reduced significantly if the historical data …

Evaluation Of Orthophosphate Based Corrosion Inhibitors In Treated Water For El Paso Region, Francisco Solis Jr

Open Access Theses & Dissertations

Corrosion is an electrochemical phenomenon that involves the deterioration of a metal by the reaction of itself with its surrounding environment. One of the greatest issues for water utilities around the country is to keep the water quality safe. Corrosion can affect the quality of the water that we use on a daily basis by adding a bad taste, increasing the concentration of heavy metals, and allowing outside contaminants to enter the distribution system. The use of phosphate based corrosion inhibitors was tested in two different metals: iron and copper. The phosphate in the inhibitors react with the calcium in …

Investigating Early Age Behavior Of Portland Cement Concrete In Arid Regions, Evan Wolf

Open Access Theses & Dissertations

The early-age behavior and properties of portland cement concrete change rapidly over time as a result of the hydration process. Comprised of a series of chemical reactions, this process accelerates nonlinearly with the curing temperature. Gaining knowledge and understanding of the phases of the hydration process (i.e., dormant, setting, and hardening) plays an important role in the timely opening of roads, resuming of construction, and achieving long-term performance. Standard tests such as ASTM C403 arbitrarily define the time of initial and final setting of concrete. Despite decades of studies concerning setting times, actual predictions still span hours, while the quality …

Effects Of Gradation And Moisture Content On Resistivity Of Mechanically Stabilized Earth Wall Backfill Materials, Jose Luis Arciniega

Open Access Theses & Dissertations

The service life of mechanically stabilized earth (MSE) walls depends on the corrosion rate of the metallic reinforcement used in their construction. The resistivity of the backfill aggregates needs to be measured accurately in order to estimate realistically the corrosion rate of the reinforcement. Resistivity testing is usually performed using the traditional soil box on the portion of the aggregates that passes a No. 10 or No. 8 sieve to either select or reject the backfill. For a more reasonable characterization of the corrosivity of coarse backfills, it is desirable to use their actual gradations. To that end, several resistivity …

Back Calculation Of Intelligent Compaction Data For Mechanical Properties Of Soil System, Afshin Gholamy

Open Access Theses & Dissertations

For national economy, it is very important to have a reliable infrastructure. Because of this, all over the world, new roads are constantly being built and old roads are being maintained and, if necessary, expanded and/or repaired. Building a good quality road is very expensive, it costs several million dollars per kilometer. It is therefore crucial to make sure that the newly built and newly repaired roads are sufficiently stiff - so that they can withstand the predicted volume of traffic for a sufficient number of years. Current methods of estimating the stiffness are time-consuming and labor-consuming. The most accurate …

Technical Project Management: Union Of Systems Engineering Processes With Project Management Processes, Deyaaldeen M. Abusal

Open Access Theses & Dissertations

Today, most projects in technical fields utilize project management to complete projects as planned, and some of the projects utilize system engineering to cover the project in both technically and commercially. This Thesis investigates the relationship between Project Management (PM) and Systems Engineering (SE) to determine if a suitably professional level of management and level of quality can be achieved. When studying PM and SE separately and make a comparison between both, there is much overlap between these two mature fields. The project could be planned and completed solely by either process. This study combines both fields of Project Management …

Utilization Of Digital Image Correlation Technique In Asphalt Testing, Alejandra Escajeda

Open Access Theses & Dissertations

Over 90% of the roads in the United States are paved with hot mix asphalt (HMA). These asphalt pavements include many mix types, such as permeable friction course (PFC), stone mastic asphalt (SMA) and conventional dense graded mixes. The performance of the HMA is an important factor in pavement design programs used by many departments of transportation. The type of HMA selected not only influences the performance of the pavement structure, but also the pavement's life cycle cost. The performance life of an HMA mix is to be studied further with experimental data in order to contribute and expand on …

Geospatial Relationship Of Intelligent Compaction Measurement Values With In-Situ Testing For Quality Assessment Of Geomaterials, Luis Alberto Lemus

Open Access Theses & Dissertations

The implementation of Intelligent Compaction (IC) in the construction of transportation infrastructure as a tool for quality control of compacted geomaterials has attracted the attention of a number of highway agencies. Compaction quality has been conventionally assessed using density, and to a less extent, modulus-based spot measurements at selected locations along the roadway section. While spot measurements do not provide a thorough rendition of the level of compaction of the roadway, IC technology is effective in meeting full coverage requirements. IC roller measurements are accelerometer-based measurements recording machine-ground interaction assumed to be indicative of the stiffness of the compacted geomaterial. …

Evaluation Of Recycled Gypsum Application Dosages To Enhance The Water Infiltration Rate At Water Retention Ponds, Jorge Luis Navarrete

Open Access Theses & Dissertations

The retention ponds play central role for efficient collection, removal, and drainage of rainfall runoff from surrounding streets to minimize flooding and damage. However, low percolating retention ponds may result in an extended ponding of water, abundance bacteria accumulations, mosquito breeding, environmental hazards, among others. The presence of clayey soils and soil sodicity reduces infiltration rates of retention ponds. To enhance the infiltration rate of ponds, it is proposed to use recycled gypsum (RG), as a soil amendment in retention ponds consisting of clayey soils to enhance low infiltration rates.

To evaluate the influence of RG in clayey soils as …

Collaborative Strategies For Sea Level Rise Adaptation In Hampton Roads, Virginia, Carol Considine, Emily Steinhilber

Engineering Technology Faculty Publications

[Introduction] The Hampton Roads region is located in southeastern Virginia where the Chesapeake Bay meets the Atlantic Ocean. The region includes seventeen municipal governments and has a large federal government presence with 26 federal agencies represented (See Figure 1). The region has a population that exceeds 1.7 million and is home to the deepest water harbor on the U.S. East Coast. Hampton Roads' economy is dependent on the local waterways and houses the world's largest naval facility, the sixth largest containerized cargo complex and supports a thriving shipbuilding and repair industry as well as a tourism industry. However, the region's …

Impact Of Highway Work Zones On Traffic Crashes: A Case Study In Michigan, Qadri Hafez Shaheen

Master's Theses and Doctoral Dissertations

Infrastructure in the US is severely aged and outdated. This presents a seemingly paradoxical problem in the field of construction management: In order to fix and make roads and highways more safe, construction zones must become inherently less safe in the process. There is a high cost to taxpayers and drivers, as work zones experience a significant amount of crashes and fatalities each year. To mitigate some of the factors that contribute to these crashes, this paper attempts to deliver guidelines on how to update relevant crash data, identify relevant factors, and create recommendations accordingly. The research focused particularly on …

Integrity Assessment Of Earthen Dams And Levees Using Cross-Plot Analysis Of Seismic Refraction And Electrical Resistivity Tomograms, Leti Teklu Wodajo

Electronic Theses and Dissertations

Geophysical methods provide a rapid, economical, non-invasive, and spatial coverage of the subsurface in terms of geophysical properties. On the other hand, geophysical methods can generate multiple geophysical anomalies. An anomaly on a seismic refraction or an electrical resistivity tomogram is an area that has different values compared to its surrounding. Geophysical anomalies in dams and levees can be due to the overall heterogeneity of the subsurface, structures such as principal spillways, artifacts of inversion software, or to a true compromised location, such as an air void due to internal erosion or seepage. Therefore, there is uncertainty involved with using …

Investigation Of Rapid Remote Sensing Techniques For Forensic Wind Analyses, Yijun Liao, Richard L. Wood, Mohammad Ebrahim Mohammadi, Peter J. Hughes, J. Arn Womble

Department of Civil and Environmental Engineering: Faculty Publications

Perishable damage data resulting from severe windstorms require efficient and rapid field collection techniques. Such datasets permit forensic damage investigations and characterization of civil infrastructure. Ultimately, observed structural damage serves as a proxy approach to estimate wind speeds for storms that include hurricanes, tornadoes, straight-line winds, etc. One of the more common methods to collect, preserve, and reconstruct three-dimensional damage scenes is the use of an unmanned aerial system (UAS), commonly known as a drone. Onboard photographic payloads permit scene reconstruction via structure-from-motion; however, such approaches often require direct site access and survey points for accurate results, which limit its …

Behavior Of Cold-Formed Steel Metal Industrial Buildings, Adrianna M. Early, Mohammad Ebrahim Mohammadi, Richard L. Wood, Kara D. Peterma

Department of Civil and Environmental Engineering: Faculty Publications

This paper presents research focused on understanding the observed behavior of cold-formed steel (CFS) metal buildings during Hurricane Harvey, which made landfall Friday, August 25, 2017 between Port Aransas and Port O’Connor, Texas. Through the Geotechnical Extreme Event Reconnaissance (GEER) association (funded by the National Science Foundation) a team of structural engineers and researchers performed rapid and detailed assessments of structural damage caused by the hurricane. The National Science Foundation gathered photographs, damage assessments sheets, and three-dimensional laser point cloud data of severely damaged cold-formed steel industrial buildings. The Port Aransas County Airport experienced severe damage to several cold-formed steel …

Post-Earthquake Structural Damage Assessment Through Point Cloud Data, Mohammad Ebrahim Mohammadi, Richard L. Wood

Department of Civil and Environmental Engineering: Faculty Publications

Structural damage assessment following an extreme event can provide valuable information and insight into unanticipated damage and failure modes to improve design philosophies and design codes as well as reduce vulnerability. Oftentimes, structural engineers create finite element models (FEM) of the structure in which numerous model parameters require calibration to simulate the current state. This information may include structural plan details (geometry), material characteristics (strength and stiffness parameters), as well as observed damage patterns (cracks, spalling, etc.). Ground-based lidar (GBL) scans and Structure-from-Motion (SfM) can rapidly capture dimensionally accurate point clouds of the structure or facility of interest. Furthermore, point …

Damage Assessment Of Built-Up Areas Via Uas-Sfm Derived Point Cloud Data, Mohammad Ebrahim Mohammadi, Richard L. Wood

Department of Civil and Environmental Engineering: Faculty Publications

In the aftermath of extreme events (e.g., earthquakes, tsunami, tornados, etc.), rapid and reliable identification of the damage in a built-up area are crucial in to rescue, recovery, and reconstruction operations. While it is critical to conduct efficient emergency response management, lack of classified or tagged damaged regions due to communications and accessibility limitations can further delay recovery operations, rescue efforts, and resource management. Furthermore, critical and perishable damage scenes can also be lost during recovery and cleanup operations immediately following the event. In recent decades, advances in remote sensing technologies demonstrate a great potential to perform rapid reconnaissance and …

Analysis Of Low-Cost Bluetooth-Plus-Wifi Device For Travel Time Research, Ernest Tufuor, Laurence Rilett

Department of Civil and Environmental Engineering: Faculty Publications

MOTIVATION • Collecting real-time travel data via intelligent transportation systems (ITS) rely heavily on technologies that are expensive and challenging to maintain. • Bluetooth and Wi-Fi are the most popular low-cost communication protocols that can give a good understanding of spatial and temporal nature of travel.

USEFULNESS: This will be important for two main reasons: • Allow research to be conducted in a cost effective manner on all types of facilities. • Offers the opportunity to undertake comprehensive empirical studies on link and path travel time distributions especially for arterial roads

gBT COMPONENTS AND COST • A unit of the …

Dynamic Hotspot Identification For Limited Access Facilities Using Temporal Traffic Data, Samer Al Amili

Electronic Theses and Dissertations

Crash frequency analysis is the most critical tool to investigate traffic safety problems. Therefore, an accurate crash analysis must be conducted. Since traffic continually fluctuates over time and this effects potential of crash occurrence, shorter time periods and less aggregated traffic factors (shorter intervals than AADT) need to be used. In this dissertation, several methodologies have been conducted to elevate the accuracy of crash prediction. The performance of using less aggregated traffic data in modeling crash frequency was explored for weekdays and weekends. Four-time periods for weekdays and two time periods for weekends, with four intervals (5, 15, 30, and …

Basic Highway Workzone Safety, Collin Shamberger

Williams Honors College, Honors Research Projects

The purpose of this essay will be to examine, and provide information detailing work zone safety practices, and maximizing safety in construction zones. This report will examine the functionality of components of a work zone and how they work together, the use of standard construction drawings of work zones, personal protective equipment of workers, possible hazards of work zones, minimizing risks and ultimately work zone safety training. Also this report will provide a spreadsheet which can be used to calculate and layout a construction work zone based on a GPS location.

Applying Control Logic To The End Of The Ohio Canal Interceptor Tunnel Based On Downstream Capacity To Reduce Overflow Of Akron’S Wastewater Collection System, William Troyer

Williams Honors College, Honors Research Projects

During the Akron Waterways Renewed Program, the city of Akron is studying ways to improve efficiency in the existing sewer system while also reducing the number and scale of combined sewer overflow (CSO) events. Real time control logic can be developed to reduce CSO events by improving flow and storage capacity. Looking at one point in the system, when the target capacity of the downstream pipe was increased from 20% to 80%, the peak volume of overflow from the Ohio Canal Interceptor Tunnel decreased from 9,067 gallons to 5,965 gallons the total system overflow increased from 10.3 million gallons to …

Scope Management Strategies For Engineering Leaders To Improve Project Success Rates, Kevin Lee Ramage

Walden Dissertations and Doctoral Studies

Civil engineering projects undertaken without successful implementation of scope management strategies by project leaders are approximately 10% more likely to fail than projects undertaken with scope management strategies. Using scope management theory, the purpose of this single case study was to explore scope management strategies used by some project leaders in the engineering field to improve project success rates. Data were collected using semistructured interviews with 3 purposefully selected project leaders in Georgia, and a review of project completion reports, budget reports, government proposals, and scope management documents. Data analysis occurred using Yin's 5-step process of compiling, disassembling, reassembling, interpreting, …

Assessing Exposure To Occupants In An Indoor Space Due To Expirated Aerosols: Application Of Computational Fluid Dynamics, Firoza Binte Omar

Theses and Dissertations

Indoor environment is an important issue for the well-being of the society. In the United States more than 90% people spend their time indoor, indoor air pollution is more culpable than the pollution outside air. Two third of US businesses lose more than $100,000 per year due to workplace related illness. The trend of sharing the work space has an impact on total sick leaves in a company. Infectious particles released by a flu sufferer’s sneezing, coughing or even laughing can be a vital source. A thorough analysis on infectious particles’ transmission and air flow of the space can provide …

Probabilistic Multilevel Constitutive Model Of The Compressive Strength Of Hardened Cement Paste Reinforced With Mwcnts, Yohanna Mejia Cruz

Theses and Dissertations

Constitutive models available in the literature typically describe the compressive strength of ordinary Portland cement paste (OPC) in a deterministic fashion, in some cases as a function of variables such as W/C, porosity, and the clinker chemical composition. The significant effect of the proportion of W/C on the final strength, porosity and density have been reported in several works in material science. Some studies have shown that the addition of MWCNTs can also modify the microstructure of cement significantly, and improve compressive strength and other mechanical and physical properties. In principle, W/C, MWCNTs addition, porosity, density, and compressive strength are …

การวิเคราะห์ปัจจัยที่ส่งผลต่อการเชื่อฟังของผู้ขับขี่ที่มีต่อป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยน, กนกวรรณ ศรีเสาวกาญจน์

Chulalongkorn University Theses and Dissertations (Chula ETD)

งานวิจัยนี้มีจุดประสงค์เพื่อศึกษาการตัดสินใจของผู้ขับขี่ยานพาหนะเมื่อเห็นป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยนและวิเคราะห์ความสัมพันธ์ระหว่างปัจจัยต่างๆและการเชื่อฟังของผู้ขับขี่ที่มีต่อป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยน โดยศึกษาจากกลุ่มผู้ขับขี่รถยนต์ภายในกรุงเทพมหานครจากแบบสอบถามออนไลน์ ตัวแปรที่ใช้ในการศึกษา ได้แก่ คุณลักษณะเศรษฐกิจสังคม คุณลักษณะพฤติกรรมการใช้ความเร็วและคุณลักษณะสถานการณ์การขับขี่ ในการวิเคราะห์ข้อมูลโดยใช้วิธีสถิติพรรณนาและแบบจำลองสมการถดถอยโลจิสติก ผลการวิจัยจากกลุ่มตัวอย่างจำนวน 907 ตัวอย่างพบดังนี้ 1) การตัดสินใจใช้ความเร็วเมื่อพบป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยนส่วนใหญ่ตัดสินใจชะลอความเร็วแต่จะใช้ความเร็วไม่ถึงป้าย 2) การเปลี่ยนช่องจราจรส่วนใหญ่ไม่คิดเปลี่ยนช่องจราจร 3) ความเร็วเฉลี่ยหลังผ่านป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยนที่ตั้งใจใช้อยู่ที่ 93.44 กิโลเมตรต่อชั่วโมง 4) การเชื่อฟังป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยนส่วนใหญ่ตัดสินใจไม่เชื่อฟัง 5) การวิเคราะห์แบบจำลองความถดถอยโลจิสติกพบว่า ปัจจัยที่มีอิทธิพลต่อการเชื่อฟังป้ายขีดจำกัดความเร็วแบบปรับเปลี่ยน ได้แก่ เพศ อายุ การตัดสินใจของยานพาหนะคันหน้า ความเร็วเฉลี่ยที่ใช้ประจำบนทางพิเศษ การได้รับใบสั่งจากการใช้ความเร็วเกินกฎหมายกำหนดและการประสบอุบัติเหตุในช่วง 3ปี โดยปัจจัยที่มีอิทธิพลต่อการเพิ่มการเชื่อป้ายหลักคือ เพศ การได้รับใบสั่งจากการใช้ความเร็วเกินกฎหมายกำหนดแลละการตัดสินใจชะลอความเร็วของยานพาหนะคันหน้าเมื่อเห็นป้ายขีดจำกัดความเร็ว