Although not all civil engineers are necessarily material experts, a basic understanding of the material selection process and material behavior is a fundamental requirement for all civil and structural engineers involved in design, construction and maintenance. In addition, one of the tasks of civil engineers is to inspect and control the quality of materials in the construction process.
Since fiber-reinforced polymer composites are more commonly used to retrofit old and partially damaged structures, several examples have been added in the chapter on composites. The lab manual in the appendix has been updated to include two new experiments on creep in polymers and the effect of fiber orientation on the elastic modulus of fiber-reinforced composites.
Acknowledgments
The third sample problem was extended to demonstrate how to determine the modulus of elasticity using the third point bending test. The discussion has been expanded with several new figures to include fibers, materials, laminates and composites used in civil engineering applications.
Acknowledgments for the Global edition
However, transportation can add significantly to the cost of the materials on the construction site. This transport distance roughly doubles the cost of aggregates in the city, putting concrete at a disadvantage compared to steel.
Mechanical properties
The tangent modulus is the slope of the tangent at a point on the stress-strain curve. The amount of deformation retardation depends on the material properties and the temperature.
The mechanisms that contribute to material deterioration vary depending on the characteristics of the material and the environment. Since the rod is fixed at both ends, the length of the rod will not change.
For example, smooth texture of aggregate particles is necessary in portland cement concrete to improve workability during mixing and placing. In contrast, coarse texture of aggregate particles in asphalt concrete mixtures is necessary to provide a stable pavement layer that resists deformation under the action of load.
Also, a certain level of surface texture in the road surface is necessary to provide sufficient frictional resistance and prevent vehicle skidding when the road surface is wet.
In addition to the direct connection to materials and resources, there are other areas of LEED certification that are affected by material selection. It should be noted that the LEED rating system is intended to certify buildings, not the materials used for construction.
Material Variability
The random sample mean and standard deviation are estimates of the population mean and standard deviation, respectively. For example, Figure 1.22 shows a control chart of the compressive strength of concrete samples tested in a ready-mix plant.
For example, the extensometer shown in Figure 1.27 is used to measure the deformation of a gauge length of metal rod during a tensile test. The rod material has a tensile strength of 290 MPa and fatigue resistance as shown in Figure 1.16.
Determine the calibration factor for the LVDT by obtaining the best fit line to the data within the linear range. Knowledge of the bonding and structure of materials at the molecular level allows us to understand their behavior.
Basic Materials Concepts
If there are four valence electrons, three-dimensional covalent bonds can form (for example, the structure of carbon in diamonds) (Jastrzebski, 1987). Metallic bonds are the result of the metal atoms having loosely held electrons in the outer shell.
Metallic Materials
The arrangement of the alloying atoms in the structure can be either random or ordered. In addition, the percentage of the material in the liquid and solid phase can be determined from the phase diagram.
Octahedral holes fit in the center of the octahedron formed by connecting all the face atoms of the FCC unit cell. Tetrahedral holes are located in the center of the tetrahedron formed by connecting a corner atom with the adjacent plane atoms.
Radicals or side groups can be aligned on one side of the chain (isotactic), symmetrically on alternate sides of the chain (syndiotactic), or randomly (atactic). As the material cools, the motion of the molecules decreases and the viscosity increases.
Iron products were widely used in the latter half of the 18th century and the early part of the 19th century. Civil and structural engineers will primarily interact with the service centers to determine the availability of products required for a project, the fabricators for detailed design drawings and preparation of the product, and the fitters on the construction site.
Steel Production
Electric furnaces use an electric arc between carbon electrodes to melt and refine steel. As the steel hardens, oxygen can combine with the carbon to form carbon monoxide bubbles that are trapped in the steel and can act as initiation points for failure.
Iron–Carbon Phase Diagram
At temperatures below 727°C and to the right of the solubility limit line, a ferrite and iron carbide coexist as two phases. Ferrite a will have 0.022% carbon in solution, and iron carbide will have a carbon content of 6.7%.
Heat treatment of Steel
The material is heated to approximately 700 °C and held long enough to allow recrystallization of the ferrite phase. The outer layers are then self-annealed as the internal heat of the beam flows to the surface.
Steel Alloys
Since structural plate has a uniform thickness, normalization is an effective process and leads to a high fracture toughness of the material. The use and control of alloying agents is one of the most important factors in the development of steels with better performance characteristics.
Structural Steel
These shapes are produced in various sizes and are designated by the letters W, HP, M, S, C, MC and L. HP shapes are also wide flange shapes where the flanges and webs are the same nominal thickness and the depth and width are essentially the same.
Cold-Formed Steel
A primary difference is that cold-formed elements are more susceptible to buckling due to their limited thickness. To prevent galvanic corrosion, special care is needed to isolate the cold-formed elements from dissimilar metals, such as copper.
Fastening Products
All cold-formed steel parts are coated to protect steel against corrosion during the storage and transportation phases of construction and throughout the life of the product. The design, manufacture, and use of cold-formed steel frames are governed by standards developed and maintained by the American Iron and Steel Institute along with organizations such as ASTM, and referenced in the building codes.
Reinforcing Steel
To allow easy identification of the different bar types in the field, marker symbols are rolled into the bars as they are produced. Bar size numerical code, this code can be in millimeters or "standard bar numbers" which indicates the number of eighths of an inch of the nominal diameter of the bar.
Mechanical testing of Steel
A curve-fitting procedure can be used to estimate the straight-line portion of the shear stress-strain relationship of Figure 3.21 (ASTM E143). The lateral expansion of the specimen is typically measured after the test using a dial gauge.
Welding
The current creates a protective atmosphere at the arc to prevent oxidation of the molten metal. Zone II—The hardness control method and selected hardness are used to determine the minimum energy input for single pass fillet welds without preheating.
Steel Corrosion
Contaminants deposited on the steel surface affect the corrosion reactions and the rate of corrosion. Such reactive metal (sacrificial anode) experiences oxidation and donates electrons to the steel, protecting the steel from corrosion.
Steel Sustainability
From the graph, determine the Young's modulus of the steel and the deformation corresponding to a load of 150 kN. Determine the toughness of the material (ut) by calculating the area under the stress-strain curve, viz.
Of the approximately 600,000 bridges in the United States, only nine have aluminum primary structural members. While aluminum alloys can be formulated with strength properties similar to steel products, aluminum's modulus of elasticity is only about one-third that of steel.
Aluminum Production
An electric current is passed between carbon anodes and cathodes to separate the aluminum and oxygen molecules. The molten aluminum is shipped to a foundry to be cast into finished products or cast into ingots.
Aluminum metallurgy
- Alloy Designation System
- Temper Treatments
Products cold worked to improve strength after solution heat treatment or where the effect of cold working in flattening or straightening is recognized within the limits of mechanical properties. Products that are not cold worked after solution heat treatment or where the effect of cold working in flattening or straightening is recognized within the limits of mechanical properties.
Aluminum Testing and Properties
The temperature at which the reduction begins and the extent of the reduction depends on the alloy.
Welding and Fastening
Corrosion
Aluminum Sustainability
- lEED Considerations
- Other Sustainability Considerations
If the rod is subjected to a compressive load of 9 kN, what will be the diameter of the rod. Determine the toughness (ut) of the material by calculating the area under the stress-strain curve, viz.
Nominal Maximum Aggregate Size: The largest sieve that retains any portion of the aggregate, but generally not more than 10%. Nominal maximum aggregate size: One sieve is larger than the first sieve to retain more than 10% of the aggregates.
Aggregate sources
The Traditional and Superpave definitions usually yield the same results, but sometimes the differences in the definitions will result in different classifications of the size of a collective inventory. In these cases, the engineer must ensure that the correct specifications and definitions are used for the job requirements.
Potential aggregate sources are usually assessed for the quality of the larger pieces, the nature and amount of fine material, and the gradation of the aggregate. Petrographic studies evaluate the nature of aggregate particles and the amount of detrital material (Meininger and Nichols, 1990).
Aggregate Uses
Cores are examined petrographically for general quality, suitability for various uses and the amount of deleterious materials. The amount of large gravel and cobble sizes determines the need for crushing, while the amount of fine material determines the need for washing.
Aggregate Properties
