Materials for Civil and Construction Engineers (4th Edition)
4th Edition
ISBN: 9780134320533
Author: Michael S. Mamlouk, John P. Zaniewski
Publisher: PEARSON
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Chapter 1, Problem 1.45QP
A contractor claims that the mean compressive strength for a concrete mix is 32.4 MPa and that it has a standard deviation of 2.8 MPa. If you break 16 cylinders and obtain a mean compressive strength of 30.3 MPa, would you believe the contractor’s claim? Why? (Hint: Use statistical t-test.)
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A contractor claims that the mean compressive strength for a concrete mix is 5,000 psi and that it has a standard deviation of 400 psi. If you break 20 cylinders and obtain a mean compressive strength of 4,800 psi, would you believe the contractor’s claim? Why? (Hint: Use statistical t-test.)
1.46: A contractor claims that the mean compressive strength for a concrete mix is 5000 psi (μ) and that it has a standard deviation of 400 psi (σ). If you break 20 cylinders (N) and obtain a mean compressive strength of 4,800 psi (m), would you believe the contractor’s claim? Why? (Hint; Use statistical t-test.) Next, what is the maximum number of breaks (N) that could be performed that WOULD make you believe the contractor’s claim? Assume that the results wouldn’t change, i.e. σ = 400 psi and m = 4,800 psi. Recall that the equation to find the lower bound of a one sided distribution is LB = μ - (tσ)* σ/(N^0.5) Because the sample size is relatively small, use the ‘student t test’ to represent the normal distribution. You should have at least 95% confidence in the results. That means that α = 0.05. Keep in mind that this is a one tailed distribution, since we only care about the lower bound (i.e. meaning that we are only concerned about concrete that doesn’t meet our minimum strength…
A contractor claims that the mean compressive strength for a concrete mix is 4,830 psi and that it has a standard deviation of 430 psi obtained from testing 22 specimens. If you break 20 cylinders and obtain a mean compressive strength of 4,450 psi and a standard deviation of 480 psi, would you believe the contractor’s claim? Why? (With a 95% confidence interval)
Chapter 1 Solutions
Materials for Civil and Construction Engineers (4th Edition)
Ch. 1 - State three examples of a static load application...Ch. 1 - A material has the stressstrain behavior shown in...Ch. 1 - A tensile load of 50.000 lb is applied to a metal...Ch. 1 - A tensile load of 190 kN is applied to a round...Ch. 1 - A cylinder with a 6.0 in. diameter and 12.0 in....Ch. 1 - A metal rod with 0.5 inch diameter is subjected to...Ch. 1 - A rectangular block of aluminum 30 mm 60 mm 90...Ch. 1 - A plastic cube with a 4 in. 4 in. 4 in. is...Ch. 1 - A material has a stressstrain relationship that...Ch. 1 - On a graph, show the stressstrain relationship...
Ch. 1 - The rectangular block shown in Figure P1.11 is...Ch. 1 - The rectangular metal block shown in Figure P1.11...Ch. 1 - A cylindrical rod with a length of 380 mm and a...Ch. 1 - A cylindrical rod with a radius of 0.3 in. and a...Ch. 1 - A cylindrical rod with a diameter of 15.24 mm and...Ch. 1 - The stressstrain relationship shown in Figure...Ch. 1 - A tension test performed on a metal specimen to...Ch. 1 - An alloy has a yield strength of 41 ksi, a tensile...Ch. 1 - Prob. 1.21QPCh. 1 - Figure P1.22 shows (i) elasticperfectly plastic...Ch. 1 - An elastoplastic material with strain hardening...Ch. 1 - A brace alloy rod having a cross sectional area of...Ch. 1 - A brass alloy rod having a cross sectional area of...Ch. 1 - A copper rod with a diameter of 19 mm, modulus of...Ch. 1 - A copper rod with a diameter of 0.5 in., modulus...Ch. 1 - Define the following material behavior and provide...Ch. 1 - An asphalt concrete cylindrical specimen with a...Ch. 1 - What are the differences between modulus of...Ch. 1 - Prob. 1.33QPCh. 1 - A metal rod having a diameter of 10 mm is...Ch. 1 - What is the factor of safety? On what basis is its...Ch. 1 - Prob. 1.36QPCh. 1 - Prob. 1.37QPCh. 1 - A steel rod, which is free to move, has a length...Ch. 1 - In Problem 1.38, if the rod is snugly fitted...Ch. 1 - A 4-m-long steel plate with a rectangular cross...Ch. 1 - Estimate the tensile strength required to prevent...Ch. 1 - Prob. 1.42QPCh. 1 - Briefly discuss the variability of construction...Ch. 1 - In order to evaluate the properties of a material,...Ch. 1 - A contractor claims that the mean compressive...Ch. 1 - A contractor claims that the mean compressive...Ch. 1 - Prob. 1.47QPCh. 1 - Prob. 1.48QPCh. 1 - Prob. 1.49QPCh. 1 - Briefly discuss the concept behind each of the...Ch. 1 - Referring to the dial gauge shown in Figure P1.51,...Ch. 1 - Repeat Problem 1.51 using the dial gauge shown in...Ch. 1 - Measurements should be reported to the nearest...Ch. 1 - During calibration of an LVDT, the data shown in...Ch. 1 - During calibration of an LVDT, the data shown in...
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