ABSTRACT: This paper investigates the vibration serviceability of a steel half turn staircase in a new office building. Based on a finite element model, the vibration serviceability is assessed under moving load conditions simulating walking or running of a single person ascending or descending the stairs. For reference purposes also simulations with stationary loading conditions are performed. The predicted acceleration levels are evaluated using the response factor R, corresponding to the multiplier of the base perception curve of BS6472 for vertical vibration. Response factors significantly higher than 32 are predicted which is the criterion for single person excitation proposed by Bishop et al. to ensure negligible adverse comment for the case of light use in an office environment. To validate the predicted results, measurements are carried out to identify the modal parameters of the staircase and to evaluate the vibration levels under different conditions of usage. KEY WORDS: Human induced vibrations; Vibration serviceability; Staircases. 1 INTRODUCTION The design of slender and lightweight staircases leads to a low stiffness to mass ratio resulting in structures prone to human induced vibrations. Because of this trend, the natural frequencies of structures tend to be in the range of human induced loading frequencies. The phenomena of resonance can cause high acceleration levels in these structures, even under normal circumstances. This can cause comfort problems which contributes to a feeling of insecurity or can lead to damage in the worst case scenario. An increased awareness to these problems during the design stage can prevent these problems and small interventions can make a difference to the vibration serviceability of structures under human induced vibrations. To assess the vibration serviceability, the acceleration response needs to be calculated under different simulations using a moving load, simulating walking or running of a single person ascending or descending the stairs, and also simulations with stationary loading are performed. Kerr and Bishop [1,2] carried out numerous force plate experiments to describe the vertical force in function of time for one person walking on a staircase. According to these measurements, the stationary load that consists of impact footfalls can be described as a Fourier series with two harmonics. The force-time history of a walking force can also be described with a Fourier series as a stationary load, or as a sequence of footsteps [3]. The vibration levels can be predicted using these force models, simulating loading scenarios on a finite element model. The load cases include a realistic scenario of walking or running up- and downstairs of the staircase with one person. Secondly, the vibration levels for a stationary load on a vibration sensitive spot on the structure are investigated as a reference. The ISO Standard for serviceability of buildings and walkways against vibrations [5] provides an evaluation of the maximum vibration levels for staircases using the response factor R. This rating number will be used to define a well- founded judgment about the vibration serviceability of the staircase in this outline of the paper. 2 DESCRIPTION OF THE STAIRCASE Figure 1: Side view staircase The atrium staircase of a new office building consists essentially of steel tube profiles and will reach through three floor levels, with a cantilever landing in between. This steel half turn staircase consists of two flights of nine or ten steps each, connected by a cantilever landing and bolted to the concrete upper and lower floor. A side view of one module of the staircase is shown in figure 1. The U-shaped steps and the platforms between the floor levels contain a concrete infill. Glass panels will be used between the handrails and the stringers. Vibration serviceability assessment of a staircase based on moving load simulations and measurements Charlotte Schauvliege 1 , Pieter Verbeke 2 , Peter Van den Broeck 1,2 , Guido De Roeck 2 1 KU Leuven @ KAHO, Department of Civil Eng., Technology Cluster Construction – Structural Mechanics Gebroeders De Smetstraat 1, B-9000 Ghent, Belgium 2 KU Leuven, Department of Civil Eng., Structural Mechanics Division, Kasteelpark Arenberg 40, B-3001 Heverlee, Belgium email: [email protected], [email protected], [email protected], [email protected]Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 A. Cunha, E. Caetano, P. Ribeiro, G. Müller (eds.) ISSN: 2311-9020; ISBN: 978-972-752-165-4 1043
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ABSTRACT: This paper investigates the vibration serviceability of a steel half turn staircase in a new office building. Based on
a finite element model, the vibration serviceability is assessed under moving load conditions simulating walking or running of a
single person ascending or descending the stairs. For reference purposes also simulations with stationary loading conditions are
performed. The predicted acceleration levels are evaluated using the response factor R, corresponding to the multiplier of the
base perception curve of BS6472 for vertical vibration. Response factors significantly higher than 32 are predicted which is the
criterion for single person excitation proposed by Bishop et al. to ensure negligible adverse comment for the case of light use in
an office environment. To validate the predicted results, measurements are carried out to identify the modal parameters of the
staircase and to evaluate the vibration levels under different conditions of usage.
KEY WORDS: Human induced vibrations; Vibration serviceability; Staircases.
1 INTRODUCTION
The design of slender and lightweight staircases leads to a
low stiffness to mass ratio resulting in structures prone to
human induced vibrations. Because of this trend, the natural
frequencies of structures tend to be in the range of human
induced loading frequencies. The phenomena of resonance
can cause high acceleration levels in these structures, even
under normal circumstances. This can cause comfort problems
which contributes to a feeling of insecurity or can lead to
damage in the worst case scenario.
An increased awareness to these problems during the design
stage can prevent these problems and small interventions can
make a difference to the vibration serviceability of structures
under human induced vibrations.
To assess the vibration serviceability, the acceleration
response needs to be calculated under different simulations
using a moving load, simulating walking or running of a
single person ascending or descending the stairs, and also
simulations with stationary loading are performed.
Kerr and Bishop [1,2] carried out numerous force plate
experiments to describe the vertical force in function of time
for one person walking on a staircase. According to these
measurements, the stationary load that consists of impact
footfalls can be described as a Fourier series with two
harmonics. The force-time history of a walking force can also
be described with a Fourier series as a stationary load, or as a
sequence of footsteps [3].
The vibration levels can be predicted using these force
models, simulating loading scenarios on a finite element
model. The load cases include a realistic scenario of walking
or running up- and downstairs of the staircase with one
person. Secondly, the vibration levels for a stationary load on
a vibration sensitive spot on the structure are investigated as a
reference.
The ISO Standard for serviceability of buildings and
walkways against vibrations [5] provides an evaluation of the
maximum vibration levels for staircases using the response
factor R. This rating number will be used to define a well-
founded judgment about the vibration serviceability of the
staircase in this outline of the paper.
2 DESCRIPTION OF THE STAIRCASE
Figure 1: Side view staircase
The atrium staircase of a new office building consists
essentially of steel tube profiles and will reach through three
floor levels, with a cantilever landing in between. This steel
half turn staircase consists of two flights of nine or ten steps
each, connected by a cantilever landing and bolted to the
concrete upper and lower floor. A side view of one module of
the staircase is shown in figure 1. The U-shaped steps and the
platforms between the floor levels contain a concrete infill.
Glass panels will be used between the handrails and the
stringers.
Vibration serviceability assessment of a staircase based on moving load simulations
and measurements
Charlotte Schauvliege1, Pieter Verbeke
2, Peter Van den Broeck
1,2, Guido De Roeck
2
1 KU Leuven @ KAHO, Department of Civil Eng., Technology Cluster Construction – Structural Mechanics
Gebroeders De Smetstraat 1, B-9000 Ghent, Belgium 2 KU Leuven, Department of Civil Eng., Structural Mechanics Division, Kasteelpark Arenberg 40, B-3001 Heverlee, Belgium