This set of Pavement Design Multiple Choice Questions & Answers (MCQs) focuses on “Highway Maintenance – Benkelman Beam Deflection Studies – 1”.
1. Who developed the Benkelman beam deflection studies (BBD) and in which year?
a) A.C Benkelman in 1935
b) C.A Benkelman in 1935
c) A.C Benkelman in 1953
d) C.A Benkelman in 1953
Explanation: It was A.C Benkelman who devised the Benkelman beam deflection studies in the year 1953. It was during the AASHO (now AASHTO) road test for the purpose of measuring the deflection of the pavement layers.
2. The Benkelman beam deflection test involves finding the ______ of the pavement.
a) Recurring deflection
c) Rebound deflection
d) Bound deflection
Explanation: The Benkelman beam deflection test finds the rebound deflection of the pavement layers under a standard wheel load and tyre pressure. When the pavement is subjected to moving wheel load, it deflects under that. When the surface comes back to its original state, rebound deflection happens.
3. What is the operating speed of Benkelman beam deflection equipment?
a) 50 km/hr
b) 32 km/hr
Explanation: the operating speed of Benkelman beam deflection equipment is very slow and it can be considered to be crawling speed. The automatic road analyser is the equipment that moves with operating speed between 30 and 100 km/hr. Instrumented car is the equipment that operates at a speed of 32 km/hr.
4. Benkelman beam deflection test is a type of ______
a) Destructive testing for flexible pavement
b) Non-destructive testing for flexible pavement
c) Destructive testing for rigid pavement
d) Non-destructive testing for rigid pavement
Explanation: BBD test is a non-destructive test that is used for the structural evaluation of the flexible pavement. It measures deflection using a deflectometer present in the equipment and it is not destructive in nature. Deflection is an important feature that gives an idea about the condition of flexible pavements.
5. Which IRC code is referred to while performing the BBD studies?
a) IRC 91:1887
b) IRC 81:1887
c) IRC 91:1997
d) IRC 81:1997
Explanation: IRC 81:1997 is used to refer to while conducting the BBD test. It gives the guidelines for the strengthening of flexible road pavements using the BBD studies. The BBD studies can be used to design overlay for the rehabilitation of pavements.
6. What is the length of the slender beam portion of the Benkelman beam?
a) 3.66 m
b) 2.44 m
c) 3.33 m
d) 2.22 m
Explanation: The Benkelman beam consists of a slender beam of length 3.66 m. There is a pivot on the beam at a distance of 2.44 m from the measurement probe end. This assembly is on a datum frame and there are legs to support the same.
7. A loaded truck with a rear axle load of ______ is used for the deflection study.
a) 4880 kg
b) 8770 kg
c) 4085 kg
d) 8170 kg
Explanation: The equipments required for the test are the Benkelman beam, loaded truck, accessories like tyre pressure gauge, measuring tape, thermometer, etc. the loaded truck has the rear axle with weight 8170 kg. The design wheel load is a dual wheel load assembly with a gross weight of 4088 kg.
8. Before starting the test, the pavement stretch is divided into fair, good and poor based on ______
a) General condition of the pavement
b) Ability to carry wheel load
c) Number of cracks
d) Existing deflections due to loading
Explanation: Before starting the test, it is necessary to divide the pavement stretch into groups namely fair, good and poor. This is done based on the general condition of the pavement. This includes a general survey of ruts, cracks, and undulations on the pavement surface.
9. What is the equation to find the rebound deflection if the relationship between intermediate deflection reading Di and the final deflection reading Df is Di-Df<0.025 mm?
Explanation: The equation to find rebound deflection when Di-Df<0.025 mm is given as D=0.02(Do-Df) mm. D=0.02(Do-Df)+0.02k(Di-Df) mm is the equation used when Di-Df>0.025 mm. Do is the initial deflection reading.
10. When Di-Df>0.025 mm ______ correction is applied to the equation for computing rebound deflection.
Explanation: The equation to find rebound deflection is D=0.02(Do-Df) mm. This is applicable when Di-Df<0.025 mm and when Di-Df>0.025 mm, there is a need to modify the equation by introducing terms for leg correction. The equation hence becomes D=0.02(Do-Df)+0.02k(Di-Df) mm.
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