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Terrain errors are the least likely type of errors affecting the measured value for a horizontal angle when compared to the other listed error types. The impact of instrument errors can be mitigated by properly adjusting the devices used and by using systematic observation procedures. Environmental errors affecting horizontal angle measurement may be due to temperature differentials and the horizontal refraction of the line of sight. Personnel errors can be prevented through proper training and following standard procedures.
The degree of saturation of a 600 cm3 soil sample with the given volumetric values is 64.3%. Solution: Use the following equation to determine the degree of saturation, S. S = volume of water / volume of voids = Vw / Vv Given Vv = total volume - volume of solids Vv = 600 - 320 = 280 cm3 And Vw = VT - Vv - Vs Vw = 600 - 100 - 320 = 180 cm3 Therefore S = Vw / Vv = (180 cm3 / 280 cm3) x 100 S = 64.3%
Air-entrainment was a significant concrete technology advancement made in the 1930s to provide relief from internal pressure. Entrained air provides tiny areas within concrete into which water can expand when it freezes. Air-entrained concrete is recommended when a concrete structure is exposed to freezing conditions and is achieved by adding surfactants to a concrete mix.
The approximate volume of the material that will need to be excavated between the two cross-sections is 1,393 cubic yards. Solution Use the volume equation averaged over the two cross-sections v = L (A1 + A2)/2 Where L = length = 100 ft A1 = 420 sqft and A2 = 332 sqft V = (100 ft) (420 ft2 + 332ft2) / 2 = 37,600 ft3 = 37,600 ft3 x (1 cubic yard/ 27 ft3) = 1,393 cubic yards (approximate)
An appropriate checklist for rebar inspection is recommended that includes independent testing laboratory reports and approved placing drawings in addition to the listed items. CRSI recommends that a checklist procedure and the minimum requirements for rebar acceptance should be established during the pre-construction conference. These quality control measures will help to ensure that the rebar used will meet specific material standards and the project owner’s requirements.
The basic types of connections for beams, columns, trusses, and joists are pin, roller, and fixed. Roller connections provide only vertical support and allow free horizontal movement and rotation. Pin connections provide vertical and horizontal support and allow rotation. Fixed connections provide vertical and horizontal support and limit rotation.
Of the answers listed, Digital Terrain Modeling is most useful for generating high quality cartographic contours. DTMs are digital representations of a portion of the Earth’s surface. The input data, data models, and algorithms required to generate a digital model of a terrain’s surface are significantly different from those needed to represent planimetric data. For example, most DTM data is derived from a combination of ground surveys, photogrammetric resources, digitized cartographic data, and altimetry data.
The statements regarding concrete used as a building material that are considered to be correct are as follow: - Commonly composed of water, cement, aggregate, and admixtures - Concrete strength is normally tested at 28 days - Concrete mixes vary by specific use requirements ASCE is not recognized as the provider of design criteria for concrete building elements - the American Concrete Institution (ACI) holds that distinction. The ACI building code standards are set in the document ACI 318-05 Building Code Requirements for Structural Concrete.
All of the scenarios listed can be modeled mathematically. With technology available today, engineers and planners are able to model the flow of water, migration of pollutants, and dispersion of particulates through air. Mathematical models can be built using specialized computer software linked to geographic information systems and real-time sampling equipment. These models can be used for predictive forecasting, planning, and mitigation purposes.
The porosity of a 950 g dry soil sample, with an undisturbed volume of 900 cm3 and a particle density of 2.65 g/cm3, is 60%. The porosity of a soil is the ratio of the volume of soil pores to the total soil volume, and the soil porosity values range from 0 to 1. Solution: Use the following equation to determine porosity, n: n = 1 - (bulk density / particle density) = 1 - (Db / Dp) Given Dp = 2.65 Therefore, n = 1 - [(mass of dry soil / volume of solids and pore spaces) / 2.65] = 1 - [(950 g / 900 cm3) / (2.65 g/cm3 x 100)] Porosity = n = 60%
Structural forces originate from the following conditions: - Point loads - Uniform loads - Non-uniformly distributed loads - Moments Structural forces, or loads on a structure, result in stresses on the structural material. There are two types of material stress: compression and tension.
The Principle of Superposition can be described by the following: “If the behavior of a structure is linearly elastic, the forces acting on it may be separated, and the structure analyzed for separate cases. The final results are found by summing the individual results.” This principle is very useful when analyzing different types of forces acting on a structure. The Principle of Superposition can be applied to reactions, shears, moments, stresses, and strains.
The sentence “A good writer will only use big words when necessary.” provides an example of effective diction. Good writers understand that fancy words are often distracting and condescending. Avoid using overblown vocabulary unless you are writing the next Great American novel.
Hooke’s Law of simple harmonic motion can be expressed as spring force = -(spring constant x displacement). Spring force always pushes or pulls a mass towards its original equilibrium position, and as such, is referred to as a restoring force. Hooke’s Law describes the relationship of the restoring force as being directly proportional to the displacement of the mass.
The true length of a line that is measured as 1,200 ft at 98°F is 1,200.23 using a standard tape. Solution Correction = (steel tape coefficient of expansion)(outside temperature - standard temperature)(measured length) Correction = (0.00000645 * 1/°F) (98°F - 68°F) (1,200) = +0.23 ft True length = distance + correction True length= 1,200.00 ft + 0.23 ft = 1,200.23 ft
Use the sum of exterior angles of a polygon equation: S = (n+2) x 180° Where n = 8 S = (8+2) x 180° = 1,800°
The statement “Contour lines are parallel to the direction of maximum slope” is NOT true. Contour lines are perpendicular to the direction of maximum slope. The contour interval for contour lines is the constant vertical distance between adjacent contour lines.
The acceleration of a 2.2 kg object sliding across a smooth surface with a net force of 1.6 N to the right acting on it is 0.73 m/s2 to the right. Solution Use Newton’s Second Law Σ F = ma Where Σ F = net force = 1.6 N to the right m = mass = 2.2 kg a = acceleration Σ F = ma, so a = Σ F/m a = 1.6 N / 2.2 kg 1 N = 1 kgm/s2, so a = (1.6 kg m/s2)/2.2 kg = 0.73 m/s2
When evaluating the progress of a project using the Earned Value Management approach, a project is considered profitable when the actual budget spent is less than or equal to the earned value. A project is considered to be over budget when the actual cost is greater than the earned value. A project is considered to be behind schedule when the billed cost of work performed up to a certain date is less that the budgeted cost of work scheduled to be completed at that date.
The Rankine and Coulomb Theories are used to analyze active and passive lateral earth pressure. The two theories are similar; however, the Rankine Theory assumes there is no adhesion or friction between the wall and the soil, and lateral pressure is limited to vertical walls, while the Coulomb Theory assumes that there is friction between the wall and the soil and that lateral pressure is not limited to vertical walls.
