Effect of Free Vibration Frequency on Modeling of Bridge Pier
- PDF / 452,433 Bytes
- 9 Pages / 439.37 x 666.142 pts Page_size
- 6 Downloads / 359 Views
Effect of Free Vibration Frequency on Modeling of Bridge Pier Sushilkumar B Magade 1 & Ramakant K Ingle 2 Accepted: 30 August 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Pile groups are a widely used foundation system to support structures placed over soft soil or when the shallow foundation is not appropriate due to excessive settlement especially for bridges, flyovers, or metro piers. Estimation of appropriate free vibration frequency for a bridge pier in design procedure gives appropriate and more optimized design. The frequencies obtained by considering soil pile interaction are more realistic than considering bridge pier as single degree of freedom (SDOF) system fixed at top of a pile cap. In the present study, the frequency is calculated by modeling the pier as SDOF system as well as by considering the soil-pile interaction effect. It is observed that to evaluate free vibration frequency, pile-soil interaction effect including distributed mass system for pier should be accounted. Keywords Piled foundation (PF) . Bridge pier . Free vibration frequency . SDOF system
1 Introduction The natural frequency of vibration for different structures represents the fingerprint of that structure identifying their dynamic characteristic and controlling their performance and responses (Shirgir et al. 2016). As per various seismic codes and recommendations, the fundamental time period plays a major role in predicting the expected behavior of the structure under dynamic excitation and this is also used to estimate equivalent lateral seismic design force. Presently, there are three common approaches used for calculation of natural frequency: (Duan et al. 1999) simple SDOF method, (IRC6 2016) calculation according to standard empirical formulae suggested by various guidelines, * Sushilkumar B Magade [email protected]
1
Department of Civil Engineering, MIT Academy of Engineering, Dehu Phata, Alandi, Pune, Maharashtra, India
2
Department of Applied Mechanics, Visvesvaraya National Institute of Technology, South Ambazari Road, Abhyankar Nagar, Nagpur, Maharashtra 440010, India
Transportation Infrastructure Geotechnology
and (IS1893-part3 2014) finite element method (Zhao et al. 2010). To calculate the free vibration frequency of the bridge pier supported with piles, the SDOF system is considered because the pier is generally assumed fixed into a pile cap. However, ignoring the soil flexibility effect may alter the frequency of the pier. Spyrakos (1990) attempted to assess the significance of SSI effect on the seismic responses of short-span bridges by implementing a simple representation of a soil-bridge pier system and concluded that safer and more economical bridge designs could be obtained by properly accounting for SSI. The expressions for SDOF system are summarized below, rffiffiffiffi K 2π ω¼ or ω ¼ m T
or
ω ¼ 2πf
where K and m are stiffness and mass, ω is the angular velocity (CPS), T is the time taken to complete one cycle of motion, and f is the frequency or the number o
Data Loading...
