Vahid KHOONDZADE-NOGHABI - M.Sc student, University of Tehran, Tehran, Iran
Khosrow BARGI - Professor, University of Tehran , Tehran , Iran

Generally, in order to reduce the amount of calculations, engineers analyse a nd design the structures using simple force based methods s uch as quasi-static or spectral methods. However, we can use seismic risk assessment to study the damage du e to probable earthquakes, instead of investigatin g force or displacement responses which are the basis of si mple design methods. About the main purpose o f this paper, it should be said that selecting the cable confi guration is always a challenge in cable stayed -bridges designing. It is because of that, the changing cable configuration in a cable - stayed bridge, firstly affects the period and damping of the structure, and secondly changes the forces in other components of the bridge which results in change of their required dimensions . Based on this, it can be concluded that a chang e in cable configuration will result in change in seismic risk, and a change in construction costs. So it is necessary to thoroughly investigate the common cable configurations in order to select the optimal option. In this paper, we will try to perform the seismic design o n a cable - stayed bridge with Semi Fan and two other common configurations. So we will be able to relatively compare the dimensions and c osts of three mentioned schemes. Then, the loss due to probable earthquakes can be obtained for each scheme using the Seismic Risk Assessment process performed in tw o steps: Fragility Assessment and Loss Assessm ent. In the end, by using the proposed Cost-Loss-Benefit (C LB) method and comparative-financial approac h, the construction costs will be investigated simultaneously along with losses due to probable earthquakes. The CLB method will determine the optimal cable config uration by defining the Benefit Ratio (BR) as a profitability measure. Based on BR values, the Fan cable configuration is proposed as the optimal cable c onfiguration for studied bridge.

Lali Cable-Stayed Bridge, Seismic Risk Assessment, Optimal Cable Configuration, Cost– Loss– Benefit (CLB) Method, Structural Damping Ratio