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

A designer has conservatively assessed a floor plate for an office of 18m x 30m. The structural grid is 9m x 7.5m and the plans show a central corridor running the length of the building. The target response factor is 8, but initial calculations indicate a response factor of 9. Which of the following strategies could the designer use to potentially reduce the initial response factor calculated?

The source of excitation (the corridor) is close to the column line, and so a µe value less than 1 is possible
Replace normal weight concrete for the composite slab with lightweight concrete
Reduce the walking path and resonance build-up by introducing doors in the corridor
If the axis of vibration is known use the appropriate frequency weighting curve

Where is the magnitude of damping of most importance?

Floors with low frequency
Floors with low frequency
Resonant floors
Floors subject to group activities

Which of the following descriptions accurately describes primary beam mode?

The primary beams form nodal lines about which the secondary beams vibrate as simply supported members. The slab is assumed to be continuous over the secondary beams and so a fixed-ended boundary condition is used.
The primary beams vibrate about the columns as simply supported members, and the secondary beams and slab are taken to be simply supported
The primary beams vibrate about the columns as simply supported members, and the secondary beams and slab are taken to be fixed-ended
The primary beams vibrate about the columns as fixed-ended members, and the secondary beams and slab are taken to be simply supported

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

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

Which of the following statements is incorrect? Human perception to vibration:

Depends on the frequency of the vibration
Depends on the direction of vibration relative to the spine
Is higher for intermittent vibrations
Is higher with vibrations having a frequency between of 4 and 8 Hz

When assessing the frequency of a floor, which elements of the floor must the designer check?

The slab
The secondary beam
The primary beam
All of the above, both individually and collectively

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 statements below are true with respect to the Variable Dose Value (VDV) method?

VDV’s can be used for hospital operating theatres
They relate the response factor or multiplying factor to the intermittency of vibration
VDV’s are independent of walking path length
Give the number of times that an activity can take place in a given exposure period