Loading...
3 results
Search Results
Now showing 1 - 3 of 3
- Numerical methods to predict human induced vibrations on low frequency stairs. Part 1: literature review, modellingPublication . Andrade, Pedro; Santos, José; Maia, LinoRecent trends towards slender construction with prominent and exigent architectural requirements often result in low frequency staircases that are significantly flexible and susceptible to unacceptable vibrations, which may promote safety concerns for their users. For structural engineers, however, there is still a lack of understanding, available information and specific design guides for predicting the dynamic behaviour of staircases due to human induced vibrations. To address this problem, this work reviews and applies the main existing numerical methods for predicting vibrations, to evaluate their precision and provide practical guidance when designing flexible staircases. The work developed is presented in a two-part paper. In Part 1, the actual paper, several numerical methods are introduced and a detailed description is given of how these can be employed in a design stage. The distinction between low and high frequency staircases is explained, since it directly influences the structure’s behaviour and, subsequently, the selected method. A description is given of how to simulate walking dynamic loads, which forms the basis of all methods. The group effect is also discussed because it tends to considerably amplify the staircase response. Finally, the different numerical procedures are applied to a practical case and compared. It was observed that, although the four numerical methods were employed with the same staircase, their results were different. The reasons for the higher results of Fourier series walking models are explained. In Part 2, the follow-up paper, the numerical methods are employed on a real staircase, comparing the estimated and experimental results.
- Improvement of staircases vibration serviceability to human ergonomics: a case studyPublication . Andrade, Pedro; Santos, José; Maia, LinoContemporary, slender and lightweight monumental staircases are often highly susceptible to resonance phenomena, due to typically low fundamental frequencies, which can considerably amplify their responses, raising major serviceability problems and causing discomfort and unsafety concerns to its users. This paper presents a case study of a low fundamental frequency steel staircase with known high levels of vibration since the beginning of its construction, in which various improvement solutions were proposed in order to increase its vibration serviceability. In total, six improvement measures were proposed, being tested using the Finite Element (FE) software SAP2000. The initial FE staircase model was first calibrated with the vibrations experimentally measured on the real staircase. Then, the original FE model was modified with the six improvement measures and the resulting vibrations were compared with those initially obtained and the acceptable limits suggested by the design guide SCI P354, to verify their viability. The most efficient numerical improvements were those that increased the staircase fundamental frequency, off the range of frequencies excitable by pedestrians walking.
- Reinforcement measures to reduce the human induced vibrations on stair steps: a case studyPublication . Andrade, Pedro; Santos, José; Maia, LinoThe human induced vibrations seen on stairs are usually a global phenomenon, however in some cases, if the connection between the treads and the rest of the structure has a very low rotational stiffness, a so-called local vibration phenomenon can happen, i.e. the vibrations in the treads may be independent from those verified on the staircase that it supports them. This paper presents a case study of a particular metal staircase in which the local vibrations were high. The objective of this study was to measure the vibrations experimentally and then to propose several reinforcement measures in order to reduce them. A total of eight reinforcement measures were proposed, being tested through the construction of several numerical models using the software SAP2000. The numerical accelerations obtained with each reinforcement measure were compared with those obtained initially and with the design guide SCI P354 to verify their effectiveness. The most effective reinforcement measures were those that significantly increased the stiffness of the treads.