Design of floors for vibration quiz

Please answer the following 10 multiple choice questions, then click 'submit' to check the result. The pass mark for a CPD certificate is 8 out of 10, and you may retake the quiz as many times as you wish, but the questions will vary! Please note that one, two, three or all of the possible answers presented for each question may be right, and to gain a mark for that question all correct answers must be identified.

Good luck

Design of floors for vibration

No floor structure, and no single element within that floor structure, should have a fundamental frequency less than what?

8.4hz
5hz
4hz
3hz

What is a reasonable frequency range caused by walking?

2 Hz to 3 Hz
1 Hz to 2 Hz
2.8 Hz to 3.2 Hz
1.8 Hz to 2.2 Hz

Which of the following statements is incorrect?

If the beams of a floor have a natural frequency of 4Hz or higher, then the floor performance is satisfactory for vibration
The frequency of the system (composed of primary and secondary beams plus slab) should be higher than 3Hz
Both primary and secondary beam mode shapes should be investigated and the mode which gives the higher deflection is more critical
If component frequencies are known then Dunkerley’s equation may be used to calculate the frequency of the system

Why do we calculate the natural frequency of a floor system? (tick all that apply)

To avoid resonant behaviour of the floor plate
To ensure that any dynamic effects do not induce loads greater than the static loads for which the floor plate has been designed
To ensure that the system frequency is sufficiently greater than the forcing or walking pace frequency
To obtain a qualitative prediction of the serviceability performance of the floor plate

For a traditional composite floor system, comprising a slab continuous over a number of secondary beams that in turn are supported by primary beams, what two mode shapes should the designer consider if analysing by hand?

Slab mode
Secondary beam mode
Simply supported beam mode
Primary beam mode

In respect of Vibration Dose Values (VDV’s), which statements are correct?

VDV’s provide a mechanism for taking account of the intermittent nature of vibrations
VDV’s can be used for operating theatres in hospitals
VDV’s are generally used when calculated response factors are within the limits of multiplying factors for continuous vibrations
Guidance on the use of VDV’s can be found in BS 6472 and P354

According to SCI’s P354, “Design of Floors for Vibration: A New Approach”, the recommended response factor or multiplying factor for an office is?

2
4
6
8

The frequency of an element or system is inversely proportional to the square root of the deflection. On what loading is the deflection based in the UK?

Dead load + 30% of the imposed load
Dead load + 10% of the imposed load
Dead load only
Dead load + imposed load

Which of the following statements are true?

The response factors or multiplying factors given in BS 6472 are “for a low probability of adverse comment”
Multiplying factors are for exposure to continuous vibration
Multiplying factors are for a 16 hour exposure period during the day
Multiplying factors are for an 8 hour exposure period during the night

Which statement below does NOT describe a characteristic of a low frequency floor?

Has a fundamental frequency greater than 3 Hz but less than 10Hz
Exhibits a near resonant response
Both steady state and transient response must be checked
Has a fundamental frequency greater than 10Hz