Dynamic analysis and design of steel staircases against vibration from walking induced vibration

Abstract

The architectural trend in commercial buildings comes with light slender staircases and few supports which subsequently leads to structures with light masses and low natural frequency. The vibration serviceability criteria are often the governing in the design for such staircases.

The core of this thesis is case studies of two lightweight existing staircases modelled and designed by FEM software. The output of the FEM models is utilized to assess the vibration design according to the guidance documents Design of Floors for Vibration: A New Approach (SCI-P354) by The Steel Construction Institute. An introduction of fundamentals of dynamics are represented to form a basis for the case study. Additionally, a case study of a staircase in the design stage is mentioned in this thesis. The response factor for that staircase is too high according to SCI-P354 which effects the dynamic behaviour of the staircase. An alternative design is suggested to improve the dynamic behaviour of the staircase.

A field survey was conducted during this thesis to survey the user´s response and feeling while using the staircases. The survey aimed to help making the decision whether the staircase is comfortable or not.

According to the results of this thesis, it is concluded that an under-designed staircases do not fulfil the vibration limits by SCI-P354. The staircases though have not caused any dissatisfaction to the users. The limits do not apply very well in the situation when the natural frequency is outside the excitation region of the input energy level defined in SCI-P354. Because of that, the staircase produces high response factor that contradicted with the field survey obtained during this thesis. The alternative design of the third case study in this thesis brings the importance of coordination between the structural engineer and the architect to bring the issue of vibration to a middle course for the design.