Civil Insight: A Technical Magazine Volume 2 | Page 22

22
TEACHERS’ SECTION
CIVIL INSIGHT 2018
Calculation of racking ratio (R rec )
Based on the fl exibility ratio, racking ratio can be calculated as (Wang et al.,1993)
ሺ ୰ୣୡ ) ൌ ቈ
ସሺଵି஬ ౣ ሻ
ሺయషర‫כ‬ತౣ ሻ
ቀ
ቁ ାଵ
ూ౨
቉
For Ԃ ୫ = 0.4 and ୰ = 7.567
ሺ ୰ୣୡ ) = 2.02529
Calculation of racking deformation of the structure
Figure 4: Racking ratio between structure and free-fi eld [Wang et al., 1993]
Racking deformation of the structure is
ሺ ୰ୣୡ ) * ¨ free - field = 2.02529 * 5.6212 = 11.385 mm
CONCLUSION
The main objective of this study is to investigate the Racking deformation of cut-and-cover structures with
embedment depth on the seismic behavior of the structures.
• Using analytical method, free-fi eld deformation and racking deformation of the tunnel were 5.4128mm
and 11.385mm respectively.
• Soil-structure interaction effect is obtained from numerical solution.
REFERENCES
[1] J.H. Wood. “Earthquake Design Procedures for Rectangular Underground Structures”. Earthquake
commission research foundation 2004
[2] Wang, J.N. “Seismic Design of Tunnels”, Monograph 7, Parsons Brinckerhoff Quade and Douglas, Inc,
1993
[3] Youssef M.A. Hashash, Jeffrey J. Hook, Birger Schmidt, John I-Chiang Yao. “Seismic design and analysis
of underground structures”. Tunneling and underground space technology16, USA, 2001, pages 247-293.
[4] J.H. Wood. “Earthquake Design of Rectangular Underground Structures”. Bulletin of the New Zealand
Society for Earthquake Engineering, Vol.40, No.1, March 2007.
[5] Hamid Reza Nejati, MortezaAhmadi and Hamid Hashemolhosseini. “An investigation on the ground
motion parameters and seismic response of underground structures”. Earthquake science (2012) 25, 253-
261.