American Journal of Engineering Research (AJER) 2018 American Journal of Engineering Research (AJER) e-ISSN: 2320-0847 p-ISSN : 2320-0936 Volume-7, Issue-1, pp-88-98 www.ajer.org Research Paper Open Access www.ajer.org Page 88 Cyclic Load Behavior of Self-Centering Hammer-Head Bridge Piers Dina M. Fathi 1 , Hussein O. Okail 2 , Hesham A. Mahdi 3 and Amr A. Abdelrahman 4 1 Teaching Assistant, Structural Engineering and Construction Management Department, Future University in Egypt (FUE), Cairo, Egypt. 2 Associate Professor, Structural Engineering Department, Ain Shams University, Cairo, Egypt. 3 Minister of Transportation, Transportation Ministry, Cairo, Egypt. 4 Head of Structural Engineering Department, Ain Shams University, Cairo, Egypt. ABSTRACT:This paper presents an experimental investigation in the cyclic load response of hammer-head bridge piers. The paper specifically investigates hammer-head bridge piers in which precast elements are assembled with unbondedprestressing to provide self-centering capabilities under extreme lateral loading. This technique is beneficial in terms of limiting the expected residual deformations after major seismic events. Five one-fifth scale pier prototypes were designed, fabricated and tested under both gravity and lateral cyclic loading in displacement control. The test matrix was designed to investigate the effect of the construction method (monolithic versus precast), level of initial prestressing in the unbonded tendons and the use of energy dissipation rebars to result in fatter hysteresis loops. Experimental results showed that the proposed construction method is indeed capable of enhancing the cyclic load response characteristics in terms of increased ultimate lateral load capacity, reduced residual displacements, delayed damage states and reasonable energy dissipation capacity. The paper serves as a foundation for the next phase of the research program in which a detailed numerical simulation study will be developed to examine various design considerations related to the seismic behavior of such construction method. Keywords -Bridge Piers, Energy Dissipation, Seismic Behavior, Self-Centering. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 26-12-2017 Date of acceptance: 11-01-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Accelerated Bridge Construction (ABC) has recently gained increasing attention in bridge engineering community. Major advantages of using ABC system include; reduction of traffic disruption specially in urban settings where traffic control for large periods cannot be permitted while maintaining construction quality and reducing life-cycle costs. Also assemblage of ABC system with posttensioning tendons results in structural advantages as the system is kept as one unite during an earthquake achieving less residual displacements after an earthquake occurrence by enforcing bridge pier to re-center; hence the name by self-centering system. Unbonded tendons through the bridge bent are preferred to decrease posttensioning loses and to increase bridge pier self-centering capabilities. Precast self-centering hammer-head bridge piers have been used in many bridge construction projects in regions of low seismicity. Examples include Mid-Bay Bridge, Louetta Road Overpass in Houston, U.S. Highway 183 elevated in Austin, Tex., Varina-Enon Bridge in Virginia (Billington et al. 1999; Figg and Pate 2004). However, segmental column applications in regions of moderate-to-high seismicity are still limited because of the limited knowledge pertaining to the seismic behavior of such type of bridge pier construction.In the past few years, some research activities on the seismic behavior of precast self-centering bridge piers have been carried out as (Laila S. Cohagen, Jason B.K. Pang, John F. Stanton and Marc O Eberhard, 2008) investigated the effect of variable initial prestressing force on the response of a precast concrete bridge bent designed to recenter after an earthquake by testing a prestressed column-foundation joint. It was found that keeping initial prestressing tendons within the proportional limit maximizes the recentering capability of the bridge bent. Also an increase in the posttensioning force led to slight increase in damage at high drift ratios [1].