Wind-induced dynamic response of large billboard structures | |
| Author | Ziauddin, S. M. |
| Call Number | AIT Thesis no.ST-15-01 |
| Subject(s) | Billboards Structural dynamics |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Structural Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. ST-15-01 |
| Abstract | Increasing number of billboard collapse during wind storms indicates the vulnerability of this structure subjected to wind force. Though there have been a number of research studies on billboard structure and they are extensively incorporated in design codes but adequate performance of this structure could not be ensured yet. Typical billboard structures have fundamental natural frequency about 1 Hz or higher. It is commonly considered that significant resonant response to wind-induced force occurs when structures have fundamental natural frequency less than 1 Hz. Therefore, all previous studies assumed that the dynamic response of billboard structure is dominated by quasi-static response. However, contribution of resonant response also depends on damping. Billboard structures may contain damping values low enough to provoke significant resonant response. Moreover, dynamic wind load can lead billboard structures to oscillate in the along-wind and torsional direction. Coupling of these two responses may give net stress at the supporting column of billboard structure higher than allowable limit. A typical billboard structure located in Pak Chong district, Nakhon Ratchasima province is selected as a case study to examine the significance of resonant response and lateral-torsional coupled response through a combination of numerical analysis work and wind tunnel model test. As first step, 1:100 scale open terrain boundary layer wind flow was simulated in the TU-AIT wind tunnel. Thereafter, a rigid 1:100 scale pressure model of the selected billboard structure was tested in simulated wind flow and dynamic wind pressure on external surface of the model simultaneously measured at 70 pressure tap locations for wind exposure angles 0° to 80° with 10° increment. After scaling up measured wind pressure to prototype scale, time histories of overall modal loads at translational and torsional modes of vibrations as a function of wind directions are determined by integrating the instantaneous wind pressure over the entire billboard panel with the billboard’s normalized modal deflections as weighting factor. This force measurement technique is called High Frequency Pressure Integration (HFPI). Afterwards, dynamic response of the billboard structure to windinduced drag force and torsion was obtained individually. However, inclusion of numerically obtained aerodynamic damping added new feature to the analysis. Thereafter, significance of resonant response was determined and lateral-torsional coupled displacement response was calculated by numerically joining individual responses. Lastly, equivalent static force for all wind attack angles were applied to finite element model and stress at supporting column was obtained through analysis. The results obtained from this study showed that dynamic response to wind-induced torsion of billboard structure is dominated by resonant response. However, high aerodynamic damping suppressed resonant response to wind-induced drag force. Though, lateral-torsional coupled displacement response is found to be indistinguishable to translational response. Yet, this inconsequential response results in higher net stress than allowable limit at the supporting column of billboard structure. |
| Year | 2015 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. ST-15-01 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai; |
| Examination Committee(s) | Thanakorn Pheeraphan;Punchet Thammarak; |
| Scholarship Donor(s) | Citadel Properties Ltd., Bangladesh ;AIT Fellowship; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2015 |