Effects of crowd behavior on dynamic responses of permanent grandstand structure

Abstract

Constructions industry’s novel design and technological development have resulted in an enhanced use of slender structures having low natural frequency. The overwhelming happiness in concert, shows, sporting events etc., potentialize enthusiastic behaviour of people causes dynamic crowd load i.e., synchronized rhythmic movements may excite supporting slender structures such as stadium, grandstands, auditorium, bridges, malls and convention centre. The combination of slender structures with dynamic crowd load makes the structure easily vulnerable to excessive vibrations and dangerously affects the safety and comfort of occupants. Hence the vibration problems due to increased structural slenderness and dynamic crowd excitation have become more common. So studies regarding the behaviour of dynamic crowd load are mandatory. The present work aims to find out the behaviour of permanent grandstand structure under dynamic crowd load. Here we investigate the behaviour of grandstand structure considering load at different frequency of jumpers in the range of 1.5 Hz to 3.5Hz, different types of activity such as normal jumping, high aerobics and low aerobics and various percentage of active crowd with total crowd, also the effects of rake angle on the structure to reduce the vibration. Active dynamic crowd load was analytically developed as taken from BS 6399-Part 1 and generated as time history and applied to the structure. The passive live load as taken 5kN/m2 specified in IS 875 (Part II). A three dimensional finite element model is used to model the grandstand structure. For modelling the grandstand structure and dynamic analysis finite element software, SAP2000 was used. The results obtained are compared in form of horizontal frequency, vertical frequency, acceleration, displacement, shear force and bending moment.