Determinacy and Stability on the FE Civil Exam

For those taking the FE Civil exam, one of the structural topics one should be familiar with is determinacy and stability. This blog post will provide a brief overview of these concepts, review how basic structures can be evaluated for determinacy, and briefly discuss some of the basic methods for solving the reactions of indeterminate structures.

In this blog,

1. Statically Determinate and Statically Indeterminate Structural Systems

2. Trusses

3. Stability

4. General Approaches to Problem-Solving

5. General Force Method

1. Statically Determinate and Statically Indeterminate Structural Systems

In structural analysis, there are considered to be two different types of stable structural systems: statically determinate and statically indeterminate. A stable structure is one whose forces are in equilibrium (as opposed, for example, to one which is in motion). Those stable structures which are determinate can be solved by statics using the three familiar equations of equilibrium. Namely, these are: The sum of forces in the vertical (or y-axis) direction is equal to zero; the sum of forces in the horizontal (or x-axis) direction is equal to zero; and the sum of moments is equal to zero. Again, such structural problems which can be solved using only these equations are known as statically determinate structures. Statically indeterminate structures, by contrast, are those which cannot be solved by these equations alone. These are also sometimes referred to as redundant structures.

The simple method by which one can determine whether a structure is statically determinate or indeterminate (and if indeterminate, by what degree) is the following: Determine the number of support reactions to solve for, and then compare them to the number of static equilibrium equations, which is three. If the number of support reactions is less than or equal to three, then it is a statically determinate structure. If it contains more than three support reactions to solve for, then it is statically indeterminate. The degree to which a structure is indeterminate is equal to the support reactions minus three.

For example, if a simple beam is supported on one end by a pin support and on the other end by a roller support, the structure can be evaluated for determinacy as follows. The pin support, since it prevents translation in the horizontal and vertical directions (but allows for rotation) has two unknown reaction forces, that of the x-direction and the y-direction. The roller support, since it prevents translation in the vertical direction (but allows for translation in the horizontal direction and for rotation), has one unknown reaction force, that of the y-direction. With a total of three unknown support reactions, which is equal to the number of static equilibrium equations, the structure is statically determinate, and (whatever the loading conditions on the beam) the reactions can consequently be solved for utilizing those three equations alone.

If, however, one were to take the example of a beam which is supported with two pins and a roller, it would be evaluated as follows. Each of the two pin supports would have two unknowns (again, the vertical and horizontal reaction force components), and the roller would have one (again, the vertical reaction force). The total number of the support reaction forces, therefore, is five. As this is in excess of the number of static equilibrium equations by two, the system is statically indeterminate by a degree of two.

Taking one further example - a cantilevered beam with a fixed support connection at one end and a roller at the center, it can be evaluated for determinacy as follows. The fixed support, as it prevents translation in the vertical and horizontal directions and, additionally, as it prevents rotation at the support, is found to have three unknown reaction forces (x-direction, y-direction, and moment about the connection point). Adding these three unknowns to the one unknown of the roller support yields a total of four, and thus the structure is found to be indeterminate to the degree of one.

It should be noted that the above examples relate to what is known as external determinacy (or indeterminacy, as the case may be), but it is also possible to have structures which are internally indeterminate (even if they are externally determinate). One example of an internally indeterminate structure is that of a truss with an excess of members such that the forces within them cannot be calculated using the static equilibrium equations alone.

2. Trusses

In evaluating a truss (within a two-dimensional plan) for internal determinacy, the following method can be used. Count the number of truss members and add this number to the number of support reactions. If this number is greater than the number of joints in the truss multiplied by two, then the structure is indeterminate. If this is the case, the degree to which it is indeterminate would be the difference then between the two numbers.

3. Stability

In terms of stability, while statically determinate structures are stable, a failure at any restraint of any of the supports results in instability of the system. By contrast, indeterminate structures, by virtue of the fact that there are more restraints than necessary for stability, are considered to be redundant systems. That is to say, the overall structure has greater potential to remain stable if a local failure were to occur within the system.

4. General Approaches to Problem-Solving

While exam-takers of the FE exam are unlikely to need to solve for reactions in a full analysis problem of an indeterminate structure, it is worth having knowledge of the general approaches to solving for these types of problems. These include the general force (or unit load) method, Castigliano's method, the moment distribution method, and the slope deflection method. For indeterminate building frames, there are still other methods, including the portal method and the cantilever method. As the general force method is one of the more common basic approaches, a brief overview of the method is provided below.

5. General Force Method

In the general force method, a loaded indeterminate structure is examined such that all support reaction components are identified. Then the structure is reimagined as one in which all redundant support components are removed so that a determinate stable structure remains (that is to say, one with only three support reaction components supporting the structure). This imagined version of the structure is sometimes referred to as the "primary structure" for the method. The primary structure is analyzed under the given loading conditions to determine the displacements which occur at the locations of the redundant support components of the original structure. The next step is to remove the original loading conditions and analyze a "secondary structure" which corresponds to the primary structure along with a unit force load applied at the location of the redundant support of the original structure. The displacement which occurs for this secondary structure is then solved for under this unit force load. This is done individually for each of the structure's redundant support restraints. Finally, through setting up equations in which the sums of the displacements are set to zero, the unknown reaction components of the structure's redundant supports can be solved for.

Conclusion

In summary, exam-takers of the FE Civil exam should be familiar with the concepts of determinacy and stability and be able to determine whether a particular two-dimensional structure is statically determinate or indeterminate and, if indeterminate, by what degree. The above examples describe the approach. While support reactions of determinate structures can be solved for using only the static equations of equilibrium, solving for indeterminate structures is a more involved process. There are a number of methods which have been developed for solving problems involving indeterminate structures. While exam-takers will not be calculating reactions for indeterminate structures on the exam, a general understanding of the most common methods, such as the general force method, aids in an understanding of the general approach to solving for indeterminate structures.

Do you want to pursue a career in civil engineering? Consider partnering with School of PE, one of the leading exam prep providers, to help you succeed with confidence!

About the Author: Adam Castelli

Adam Castelli is a licensed architect and engineer currently practicing in the Pittsburgh area. He holds a master's degree in architecture from the University of Massachusetts Amherst and a bachelor's degree in civil engineering from Villanova University.

Phase Relationships of Soil

Those taking the FE Civil exam should be familiar with the basic concepts in soil mechanics related to the phase relationships of soil. Phase relationships are also covered on the PE exam, regardless of which depth version of the exam is taken. This blog aims to provide an overview of soil phase relationship concepts, terminology, and the basic calculations involved in solving for soil component volumes and weights.

In this blog:

1. Soil Phases

2. Specific Weight of Water and the Specific Gravity of Soil Solids

3. Soil's Five Potential Variables

4. Volume and Weight of Water and Solids

5. Other Terms to Know

6. Dry Unit Weight vs. Saturated Unit Rate

1. Soil Phases

Soil can be understood to have three "phases." Specifically, these are the solids within a soil, the voids between these solids which are occupied by air, and the voids between the solids which are filled with water. The various proportions of these phases within a given soil contribute to its behavior and properties.

2. Specific Weight of Water and the Specific Gravity of Soil Solids

Before discussing concepts and calculations related to the soil phases themselves, it is necessary to understand the specific weight of water and the specific gravity of the solids portion of soils. The constant value known as the specific weight of water can be understood as the weight of water in pounds within a cubic foot of volume of water. Specifically, the value of water's specific weight is 62.4 lb/cubic ft. The constant value known as the specific gravity of soil solids is a dimensionless unit which can be understood as the ratio of the typical density of the soil solids within a soil to the density of water within a unit volume. It is not actually a consistent number but varies by the type of soil being considered, and it is also an average value based on the different types of particles within the soil (it being assumed that the soil is homogenous). It can be taken, however, as typically ranging between 2.6 and 2.85. For some organic soils, however, it can be substantially lower. The value for a particular soil can be determined by performing a specific gravity test on the soil. For the purposes of the exam, if a calculation problem involving soil phases is given, this value would likely be given so that some other value related to the soil composition can be determined.

3. Soil's Five Potential Variables

In terms of phase relationships, soil can be understood to involve five potential variables. Namely, these are the individual volumes of the solids, air (empty voids), and water (filled voids), as well as the weights of the solids and the water. Note that the weight of the air-filled voids is considered negligible. Given the information we have about the specific weight of water and the specific gravity of soil solids, any of the five variables could be solved for if three are given. The exam taker should therefore be familiar with how to solve for any of the variables by understanding the relationships between them, as follows.

4. Volume and Weight of Water and Solids

The volume of water can be calculated by dividing the weight of water by the specific weight of water. The volume of solids can be determined by dividing the weight of solids by the product of the specific gravity of soil solids and the specific weight of water. Likewise, the weight of water can be determined by multiplying the volume of water by the specific gravity of water. The weight of solids can be determined by multiplying the volume of solids by the product of the specific gravity of soil solids and the specific weight of water. Any of the volumes can be found by subtracting two other volume components from the overall volume. For example, the air volume is the difference between the overall volume and the sum of the soil and water volumes. Similarly, the weight of an unknown component (water or solid) can be found by subtracting the overall weight by the known component (water or solid). A phase diagram is a useful tool for visualizing the content of the soil (solids, empty voids, and water-filled voids) and their associated variables by separating them into different regions of the diagram. The above-described calculations can then be done as needed to determine the unknown variables of the diagram.

5. Other Terms to Know

There are a number of other terms related to soil content that the exam-taker should be familiar with which are all defined by particular ratios involving the above-described weights and volumes of a soil. A soil's degree of saturation is defined as the ratio of the volume of water to the overall volume of voids within a soil (filled or not). It is sometimes expressed as a percentage, with 100% being a fully saturated soil containing no air voids. A soil's porosity is defined as the ratio of its volume of voids (filled or not) to its total volume (including solids and voids). A soil's water content can be found by dividing the weight of a soil's water by the weight of its solids. Finally, what is known as a soil's void ratio can be found by dividing the total volume of voids (filled or not) by the volume of solids.

6. Dry Unit Weight vs. Saturated Unit Rate

One should be familiar also with the concept of a soil's dry unit weight as well as its saturated unit weight. A soil's dry unit weight can be understood, in terms of phase relationships, as the unit weight of a soil when there is no water present within the void spaces of the soil. The dry weight can be determined by laboratory test after oven-drying the soil. A saturated unit weight, by contrast, is the unit weight of a soil when the void spaces are entirely occupied by water. Completely dry soil as well as completely saturated soil are sometimes referred to as "two-phased" soils since they are lacking in the water component and the air component, respectively. Because of the necessary arrangement of solids within soils, all soils have at least some number of voids within them. Therefore, it is not possible to have a single-phased soil.

Summary

In summary, FE exam-takers should be familiar with the basic concepts of soil mechanics including those related to phase relationships for soils, how various unknown variables may be solved for given particular information about the soil content, the various terminology related to the ratios of these variables, and the concepts of dry unit weight and saturated unit weight.

About the Author: Adam Castelli

Adam Castelli is a licensed architect and engineer currently practicing in the Pittsburgh area. He holds a master's degree in architecture from the University of Massachusetts Amherst and a bachelor's degree in civil engineering from Villanova University.

Methods of Estimation in Civil Engineering

The estimation of quantities is an important aspect of civil engineering design projects. Estimates are typically provided to a client in the bid package which is prepared by the design team. It involves not only the estimation of the materials of which the completed project is composed, but also the estimation of the construction labor and equipment which is necessary for the completion of the project work.

In this blog,

1. Types of Estimates

2. Approximate or Rough Estimates

3. Detailed Estimates

4. Material Component of Estimation

5. Determining Unit Costs

6. Allowances

7. Non-Material Components

8. Earthwork

1. Types of Estimates

Estimates performed throughout the design process help the project team and owner gain an understanding of project costs and feasibility, keeping the proposed construction within the owner's budget. For this reason, estimates are typically provided at each design submission. Types of estimates include approximate (also known as rough) estimates and detailed estimates. The development of a project typically lends itself to estimation procedures of greater detail and accuracy at the later stages of design.

2. Approximate or Rough Estimates

Schematic level design, for example, lends itself to rough estimates, which can be based on an engineer's previous experience with costs. One might, for example, have a general idea of the typical cost of a parking lot at grade on a square footage basis and apply that number to the particular area which is proposed on a given project. This may not be a very accurate estimate, but it may be good enough to allow the design team to work with a general sense of an item's cost while detail on the design elements has yet to be determined. Given the uncertainties of a design during the early stages of development, design contingencies are typically added to early estimates to reduce the risk of going over the construction budget in the project design at a later stage. This is often provided as a percentage increase in the overall project cost. As the design progresses, the amount of design contingency may be lowered since there is typically less uncertainty about the design as a project progresses.

3. Detailed Estimates

Detailed estimates break down design items into their various components to gain greater accuracy of estimation. This includes separate cost components of material, labor, and equipment. For this reason, detailed cost estimation is sometimes referred to as the unit cost method. The use of unit prices and the components of an estimate which apply to them are discussed below.

4. Material Component of Estimation

The material component of the estimation is often referred to as a "take-off," as it involves the calculation of material quantities based on plans, sections, elevations, or other design drawings. The calculations for an estimation depend upon the typical unit of measure which is used for the material being estimated. This could be based on volume, area, length, unit count, or overall weight, depending on the material. The cost component of an estimation is determined by multiplying the material quantity by the corresponding unit cost to determine the overall cost for the material. For example, a calculated volume of soil in cubic yards would be multiplied by a unit cost defined as cost per cubic yard. Likewise, a calculated number of doors on a project would be multiplied by unit cost defined as a cost per unit to determine the overall cost for the doors on a project. Units of measure for typical items include: units for items such as doors, windows, drains, catch basins, manholes, and plumbing fixtures; feet or meters of length for items such as pipes, guide rails, and striping; square feet or square meters of area for items such as clearing and grubbing, paint, and flooring; cubic yards or cubic meters of volume for items such as concrete, aggregates, earthwork excavation, soil, and backfill; and tons of weight for items such as structural steel and reinforcement.

5. Determining Unit Costs

Unit costs are typically determined from industry estimating databases. Web-based services can provide the most accurate and up-to-date information. Books with published values are also utilized, though less frequently than in the past. Unit costs change over time and location due to factors such as supply and demand, inflation, and labor availability. The databases utilize recent historical data to determine a value for use in estimates. It should be noted that an estimator should review the values found in the databases and evaluate their appropriateness for the project under consideration, as the specifics of the project may warrant an adjustment to the values to gain greater accuracy in the estimate.

6. Allowances

Some items may be indicated in an estimate with an allowance rather than a unit cost basis. The allowance, however, is typically determined based on some type of assumption as to the amount of material or work required, though a precise amount may be unknown whether because of uncertainties in the design or for a lack of sufficient detail in the current stage of design.

7. Non-Material Components

Non-material components of work such as labor typically have a unit of measure in overall labor hours. Multiplication of the labor rate by the anticipate labor hours yields the labor cost. It should be noted that off hours or overtime work may need to be considered as this will increase the unit cost for the labor.

8. Earthwork

Civil engineers should be familiar with the common methods of earthwork calculations related to grading work. Earthwork consists of both cutting and filling operations. The methods of estimation for these include the average method, the block (or grid) method, and the section method, among others. Each may be most appropriate for a given type of project or stage of design.

• Average Method: In the average method, one would first determine the average level of existing conditions, then the average level of the final proposed conditions, and finally multiply this difference by the area of the work. This would roughly determine the overall amount of fill or excavated soil that would be necessary to transport to or from the site. It would be most appropriate to use this method as either a preliminary estimation method or on a smaller scale project.
• Block or Grid Method: In the block (or grid) method, one would divide an area up into smaller areas and determine the amount of difference between the existing and finish grade in each of those areas. One would then multiply the area of each of these blocks by the difference determined from each of these blocks and the sum of these numbers to determine the total amount of cutting or filling. The difference between the two totals would indicate the total soil either required to be brought in or removed. This method would result in more accuracy than the average method.
• Section Method: The section method is most appropriate for infrastructural projects, such as new highways where there is a linear area under consideration. Sections are taken at regular intervals along a path through the project area, such as at the centerline of a roadway. The existing terrain and the proposed terrain shown within these sections allow for the area difference between the two to be calculated using calculation techniques such as the trapezoidal method, wherein complex shaped sectional areas are determined by first breaking them down into simpler areas. These areas would then be multiplied by the distance between the sections taken along the path to determine the volumes of cutting or filling. Computer software is often used to generate these sections once survey data of the terrain is imported into the software.
• Soil Swell: It should also be noted that a given volume of soil, once excavated, typically expands to a larger volume, and this should be taken into consideration when determining the number of vehicle trips required for transporting the soil. This is sometimes referred to as "swell." When soil is brought into a site and then compacted, it occupies a smaller volume of space. This is sometimes referred to as "shrinkage."

Conclusion

In summary, understanding how to do quantity take-offs and determining estimated costs is a key task in civil engineering. In order to develop the most accurate cost estimates, civil engineers should be familiar with the various types of estimates and how they are made. They should also be familiar with the particular methods for estimating common work items in civil engineering such as for earthwork. Accurate quantity and cost estimates are essential for successful projects that are delivered within budget.

Are you figuring out which direction you want to take in life? If you are interested in engineering, School of PE has a comprehensive exam review course to help start you down the path to success! Register today!

About the Author: Adam Castelli

Adam Castelli is a licensed architect and engineer currently practicing in the Pittsburgh area. He holds a master's degree in architecture from the University of Massachusetts Amherst and a bachelor's degree in civil engineering from Villanova University.

Introducing the New FE Civil Exam Review Guide from School of PE

The expert instructors at School of PE created a concise learning tool to provide the most essential information students need to be successful on the FE Civil exam. Our new FE Civil Exam Review Guide is the definitive resource to help you prepare, practice, and pass the exam to earn your licensure. 

At School of PE, we know that studying for the FE Civil exam is no easy task! Our goal with the FE Civil Exam Review Guide is to equip students with the resources needed to pass-nothing more and nothing less. Developed by our highly acclaimed instructors, this book serves as an inclusive, yet concise, guide offering an array of expertise in the field of civil engineering. 

One of the aspects that makes School of PE unique is that we use multiple instructors for our exam review courses who teach only in their specific subject matter expertise to ensure the highest quality material. Having this advantage helped our team put together an exam review guide that offers a streamlined approach to make the most of your study time. 

Our FE Civil Exam Review Guide focuses your efforts on understanding the necessary content, instead of poring over information that may end up being irrelevant on exam day. This review guide follows the official NCEES exam specifications and will transform the challenging FE Civil material into logical, easy-to-understand segments. 

The FE Civil Exam Review Guide teaches civil engineering definitions, examples, and practice problems to help you confidently prepare for the exam. Bring the review guide material to life with unique Augmented Reality (AR) features that enhance your ability to navigate, comprehend, and retain key concepts. With our mobile quizzes and interactive flash cards, you will begin to truly understand the material-not just memorize it! 

School of PE strives to provide as much help as possible to lead students to success. That is why we have also included features such as colored tabs for easy navigation between chapters, wide margins for notetaking, and on-the-go eBook access through our Study Hub mobile app (internet connection required). 

To supplement your studies, School of PE has created additional premium content that is unlockable from your smartphone or tablet to help each examinee match his or her learning style. These premium features are available for each chapter and can be very helpful when preparing for the FE Civil exam! The features include the ability to ask subject-matter experts any questions you have about the material, schedule live online tutoring sessions, and watch video lectures to help you delve deeper into each topic. Simply scan the applicable code in your book with your QR code reader to access these exciting premium features. 

Order your copy of the new FE Civil Exam Review Guide today and take advantage of our bundle deal! The bundle includes both the paperback book and eBook, so you will have access anywhere, anytime, and on any device with an internet connection. 

It's time to prepare, practice, and pass the FE Civil exam with School of PE. We take your education very seriously, and when we say "Your Success is Our Success," we truly mean it!

How Tutoring Increases Chances of Passing Engineering Exams

Various academic studies have been performed to evaluate the effects of online tutoring. Tutoring has been shown to not only increase exam scores but also has been proven to help students grasp difficult topics at a faster rate compared to students who were not tutored on a specific subject, increase confidence while taking an exam, and improve overall studying skills.

It has been proven that online instruction has immensely helped the National Council of Examiners for Engineering and Surveying (NCEES) exam applicants prepare for their engineering exams. For example, the national pass rate for the October 2017 PE Civil exam was 66 percent for first-time takers while School of PE's pass rate was 90 percent.

To provide further exam review assistance to its students, School of PE has launched a new tutoring program for its FE Civil and PE Civil students.

Studies have shown that tutoring, in addition to other routine exam prep methods, has had a significant and positive impact on overall performance. The American Education Research Journal compared findings from various tutor-related studies and concluded that students who were tutored significantly outperformed students who did not participate in tutoring. Nearly 90 percent of the compared studies found that tutoring positively impacted overall exam performance.i

Preparing for an NCEES exam can be overwhelming to many examinees, as many exam applicants attempt to manage working full time and preparing for the exam. Past examinees report spending 200 to 300 hours preparing for NCEES exams, which includes attending exam review courses, reading supplemental material, and taking practice exams. Tutoring has been shown to reduce the average time needed to complete a learning objective by up to 30 percent.ii Learning objectives are completely learner-based but could include understanding a specific concept or being able to solve a problem in a specific amount of time.

Typically when adults place themselves in a learning environment, they tend to lack confidence, experience anxiety, and encounter other barriers that would have detrimental effects on their overall exam preparation approach.iii Tutoring is often believed to be a tool for building confidence and self esteem during studying and test-taking.iv Therefore, tutoring can significantly help adults prepare for NCEES exams and increase their chances of passing.

Tutoring is often viewed as a tool to help students understand and grasp difficult concepts. A well-rounded tutoring program offers more than instructional teaching; it also includes initial diagnostics, study/learning plans, and guidance for strong study habits.v A study performed by the American Society for Engineering Education showed those subjects who participated in a tutoring program rated tutoring 4.17 out of 5 when asked how effective the tutoring was in improving overall knowledge of a subject and 3.56 out of 5 when asked how effective the tutoring was in aiding study skills such as time management and study habits.vi

School of PE has recently launched a new tutoring feature for its FE Civil and PE Civil students in order to provide them with as much guidance and support in exam preparation as possible. Tutoring sessions will be one hour each and will be led by School of PE's instructors. Sessions will revolve directly around a student's exam preparation needs, and the tutor will create a structured, individualized study plan for each student.

Check out our FE and PE Civil tutoring page to further learn how School of PE's review courses and tutoring sessions can help you pass an NCEES exam.

References:

i. VanLehn, K. (2011, Oct 17). "The relative effectiveness of human tutoring, intelligent tutoring systems, and other tutoring systems." Educational Psychologist.

ii. Kuhne, G. Dr. 10 Characteristics of Adults as Learners.

iii. The Power of Tutoring Infographic. Retrieved from https://elearninginfographics.com/power-of-tutoring-infographic/

iv. Lincoln Land Community College. (2014, Oct). Online Tutor Training Module.

v. Cohen, P., Kulik, J., & Lulik, C. Educational Outcomes of Tutoring: A Meta-analysis of Findings.

vi. Paljug, B., DR, & Lampe, L. (2017, Aug.). Assessing usage, satisfaction, effectiveness, and learning outcomes for an engineering peer tutoring program.

Basic Principles and Classifications of Pile Foundations

Table of Contents

1. Introduction

2. Conditions where deep foundations are used

3. Classification of deep foundations

4. Pile foundations

5. Installation of pile foundations

6. Categories of piles

7. Types of piles based on shape and composition

1. Introduction

Shallow and deep foundations signify the relative depth of the soil on which buildings are founded. When the depth of a foundation is less than the width of the footing and is less than ten feet deep, it is a shallow foundation. Shallow foundations are used when surface soils are strong enough to support the imposed loads. If the depth of a foundation is more than the width of the building foundation, it is a deep foundation. Deep foundations are often used to transfer building loads deeper into the ground. 

2. Conditions where deep foundations are used

1. Soil near the surface that has relatively weak bearing capacities (700 pounds per square foot or less)
2. Soils near the surface that contain expansive clays (shrink/swell soils) 
3. Surface soils that are vulnerable to being removed by erosion or scour

3. Classification of deep foundations 

Deep foundations are classified into three categories:

• Pile foundations
• Well foundations
• Caisson foundations

Types of foundations and basic mechanisms involved in the classification of deep foundations are reviewed in our FE Civil exam review course for those preparing to become an engineer in training.

4. Pile foundations

A pile foundation is defined as a series of columns constructed or inserted into the ground to transmit loads to a lower level of subsoil. A pile is a long cylinder made up of a strong material, such as concrete. Piles are pushed into the ground to act as a steady support for structures built on top of them. Piles transfer the loads from structures to hard strata, rocks, or soil with high bearing capacity. The piles support the structure by remaining solidly placed in the soil. As pile foundations are set in the soil, they are more tolerant to erosion and scour.

5. Installation of pile foundations 

Piles are first cast at ground level and then hammered or driven into the ground using a pile driver. A pile driver is a machine that holds the pile vertical and hammers it into the ground. Blows are repeated by lifting a heavy weight and dropping it on top of the pile. Piles should be hammered into the ground until the refusal point is reached, which is the point where a pile cannot be driven into the soil any farther. The method of installing a pile is a major consideration in the structural integrity of pile foundations. The driven-pile method is an ideal option because it least disturbs the supporting soil around the pile and results in the highest bearing capacity for each pile. Since every pile has a zone of influence on the soil around it, piles must be spaced far enough apart from each other so that the loads are distributed evenly.

6. Categories of piles

Depending on their function, piles are classified as bearing piles, friction piles, friction-cum-bearing piles, batter piles, guide piles, and sheet piles.

Based on the composition of materials, piles are classified as timber piles, concrete piles, sand piles, or steel piles. 

1)Bearing piles are driven into the ground until a hard stratum is reached. Bearing piles rest on hard strata and act as pillars to support the structure. Bearing piles allow vertical loads and transfer the building load to the hard stratum underneath. 

2)Friction piles are used when the soil is soft and there are no hard strata available. These piles are long, and the surfaces are roughened to increase surface area and increase frictional resistance. They bear on frictional resistance between their outer surface and the soil in contact. Friction piles do not rest on hard strata. 

3)Batter piles are driven inclined to resist inclined loads.

4)Guide piles are used in the formation of cofferdams to provide stable foundations for under-water construction.

Basic principles of pile foundations and their classifications are recommended topics to review prior to taking the FE Civil exam. 

7. Types of piles based on shape and composition

Historical Background of Roadway Construction for Transportation Engineers

Table of Contents

1. Introduction

2. The Romans' Roadway Construction Technology

3. Roadway Construction Technology Improvement Methods

1. Introduction

Throughout history, humans have constantly been inventing new ways of travel. The oldest mode of travel was by foot but eventually evolved to using animals to help carry both people and materials. When motorized vehicles came along, people realized the dire need for a hard surface to accommodate wheels, which would make traveling smoother. 

These surfaces were constructed in a large scale during the period of the Roman empire with the earliest construction techniques birthing "Roman roads." The Romans, who are considered to be the pioneers of road construction, developed roads in many directions, mainly for military operations. 

2. The Romans' Roadway Construction Technology

During the Roman civilization, many roads were built by stone blocks of considerable thickness. Generally, the total thickness of the road was as thick as 0.75 to 1.2 meters. 

Overall, the required layer thickness of each course of the material depends on the average traffic load. Structural number and layer thickness calculation problems are reviewed in FE exam review courses. 

When examining Roman roads, the cross section typically has a trench of width equal to that of the carriage way. When constructing a road, the trench was excavated up to a depth until a hard stratum was reached. One or two layers of large foundation stones were laid with lime mortar at the bottom, creating a thickness of 10-20 cm for the bottom layer. Vertical curbstones were placed along the edges of the pavement. Then, a second layer of large, broken stones, which were mixed with lime motor, was laid over the bottom course up to a thickness of 25 cm to 40 cm or more depending on the requirement. The wearing course of roadway consisted of dressed large stone blocks set in lime motor at the top; the thickness of wearing course varied from 10 cm to 15 cm. This technique of construction was much stronger than that was required for animal-drawn carts during those days. Pavement design and construction is an interesting topic for professional civil engineers who are engaged in highway engineering infrastructure development projects. Fundamentals of Engineering exam certification will authenticate the design and construction process of roadways.

3. Roadway Construction Technology Improvement Methods 

Tresaguet construction technique 

Pierre Tresaguet, a French Engineer in the 1700s, developed a new method of construction, which greatly enhanced the roadway system. The system he created allowed the road to sustain less wear than the prior system of constructing roads. His method involved a layering system with both small and large stones. When constructing the road, the subgrade was prepared, and a layer of large foundation stones were laid on edge by hand. The corners of these heavy foundation stones were hammered, while the interstices were filled with smaller stones. Broken stones were placed to a thickness of about 8 cm and were compacted. The top wearing course was made of smaller stones and compacted to a thickness of approximately 5 cm at the edge and gradually increased toward the center. The shoulders were also provided with a cross slope to drain the surface water to the side drain.

Macadam construction 

John Macadam developed an entirely new method of construction compared to previous methods. His method included adding multiple steps during pavement construction, such as preparing a subgrade with a cross slope of 1 inch up to the desired width, then compacting it to the required density. Broken stones of high strength passing through a 5-cm size sieve were placed and compacted to a uniform thickness of 10 cm throughout the width of the pavement. The second layer of 3.5 cm stones were placed and compacted to a thickness of 10 cm. The top layer consisted of stones less than 2 cm and were placed and compacted to a thickness of 5 cm. These techniques provided a wide scope of ideas for recent highway engineering projects. Most of the transportation engineering related topics are reviewed in FE and PE exam prep courses for civil engineers.

Journey of Water Distribution Systems - From Water Source to Faucets

Table of Contents

1. Overview of Water Distribution System

2. Infrastructure of a Water Distribution System

3. History of Water Distribution System

4. Treatment of Water

5. Sustainable Supply of Safe Drinking Water

Overview of Water Distribution System

Water is a very important component of the human society. Since the beginning of civilization - cities, towns and communities have been built around reliable water sources. With each passing decade the technologies for bringing water from source to the faucets and eventually to the end user has been improving.

Infrastructure of a Water Distribution System

For a good water distribution system to be effective to provide a reliable and safe water to the end users must have the following:

1. Collection
2. Transmission
3. Treatment
4. Storage
5. Distribution

Within this system the water travels from the source to the distribution point for consumption. But it also undergoes some contamination as it travels through the various underground and above ground channels. So therefore, water must be treated before being distributed for any of the following purposes:

1. For residents
2. For commercial purpose
3. For industrial needs
4. Irrigation
5. Public needs such as Firefighting
6. Potable water for public use

History of Water Distribution System

Shallow Wells: The earliest form of water distribution system was created near the rivers, lakes or springs by digging up Shallow Wells. Later, as the requirement for the water increased these wells became deeper. Shallow wells were mainly found in 2500 BC alongside the growing civilization.

Qanats: A new form of water distribution systems were the Qanats. This system was created by using slightly sloping tunnels driven into hillsides that had groundwater. The origin of this system dates back to ancient Persia about 700 BC. These were very much a live system in Tehran, Iran up until 1933.

Aqueducts: The Romans had been building this water system between 312 BC and 455 AD. They discovered an ingenious way of porting water from lakes or rivers to the central Rome. Some of these aqueducts are still in use. The longest aqueduct constructed is the Aqua Marcia in 144 BC.

Wooden Log Made into Supply Pipes: The first Water Distribution System in America was the bored-out logs made out of hemlock or elm trees. These logs were sometimes joined using bituminous-like pitch or tar to caulk the joist. Boston was the first city to have a waterworks system for their domestic and fire-fighting needs.

Cast-Iron Pipes: During the early 19th century the use of cast-iron pipes was introduced to withstand high pressure. With this new innovative system, it was possible to distribute water to individual homes of the communities.

20th Century Pipelines: In the construction of underground pipelines and tunnels, materials such as cast-iron, reinforced concrete, and steel were used to improve the safe drinking water distribution system thus improving the water quality.

Treatment of Water

As the water travels through the various transmission channels it becomes contaminated. The process of boiling and filtering water to make it disease free was available as a recorded edict in the Sanskrit text in 2000 BC. Later, a German Bacteriologist Robert Koch in Mid-19th Century discovered the cause for diseases to be the infected drinking water. The Germ theory of disease was established at that time. Based on this theory, it became vital to treat drinking water. By the end of 19th Century and very early 20th Century the water was treated to eliminate deadly waterborne diseases and make it a safe drinking water for the communities.

Sustainable Supply of Safe Drinking Water

Water distribution system plays a major role to avoid water scarcity and sometime to create water supply possible even in desert regions. It is not enough to set up the system; but it is equally important that these system needs to be monitored on a regular basis to provide safe drinking water. Singapore - Massachusetts Institute of Technology (MIT) Alliance for Research and Technology (SMART) Centre is coming up with better water supply monitoring systems. Various ways of automated monitoring would ensure that the quality of the water is maintained and enhanced at the distribution point. An undergraduate taking the NCEES Civil Fundamentals of Engineering Exam (FE Exam) can brush up their knowledge of the Water Distribution System and water treatment with the aid of a Review course.