A computer package for the design of piles under cyclic tensile load E. Sai Baba Reddy a, *, M. O'Reilly b , D.N. Chapman c a Department of Civil Engineering, JNTU College of Engineering, Hyderabad, India 1 b Department of Civil Engineering, Kingston University, London, U.K. c Department of Civil Engineering, University of Nottingham, NG7 2RD, U.K. Received 18 January 1998; accepted 24 April 1998 Abstract The majority of studies on piles are directed towards their behaviour under compressive loads. There is very limited literature available on the behaviour of piles under cyclic tensile loads. With the development of tension leg platform (TLP) technology for deep oshore oil and gas ®elds, there is a growing interest in understanding the behaviour of TLP pile foundations, which are subjected to a static pull-out superimposed by a cyclic tensile force. To design a pile for cyclic tensile loading there is a need to estimate the safe cyclic tensile loads for a pile. This paper presents the details of a computer program developed to estimate the safe cyclic tensile load for a pile. In the program, factors such as load distribution along the pile length, mechanism of pile failure under cyclic loading and the critical cyclic stress level for soil±pile interface have been considered. The details of the program have been presented in the form of an algorithm and ¯owchart. Using the program, an example problem has been solved and the safe cyclic load for a set of ®eld piles has been estimated. With the help of this program a computer package is developed for the design of piles under cyclic tensile load. The details of this package are presented in the form of a ¯owchart and algorithm. # 1998 Elsevier Science Ltd. All rights reserved. Keywords: Computer package; Cyclic tensile loads; Design of piles; Tension leg platform; Oshore structures; Failure mechanism 1. Notation d angle of interface friction P load on pile head q c cyclic tensile load q t tensile capacity of pile s r radial stress t shear stress t limit limiting shear stress t max maximum shear stress TLP tension leg platform 2. Introduction In the recent decades, construction of oshore oil production platforms has increased considerably. As more and more oil ®elds have been identi®ed and developed, it is more likely that the future oil deposits are going to be small in size and available at deeper depths. It is estimated [1±6] that, for the production of oil from deep oshore ®elds, compliant structures such as tensile leg platform (TLP) are more economical than jacket (rigid frame) type structures. Piles are considered to be a suitable type of foun- dation to provide anchorage to the tension legs [7, 8]. The piles used for a TLP are subjected to a static pull- out force superimposed by a cyclic tensile force, keep- ing a net tensile force on the pile at all times [9±13]. There is very limited literature available on the beha- viour of piles under tensile loads, particularly cyclic Computers and Structures 69 (1998) 149±158 0045-7949/98/$ - see front matter # 1998 Elsevier Science Ltd. All rights reserved. PII: S0045-7949(98)00105-9 PERGAMON * Corresponding author. 1 PresentlyÐDivision of Engineering, St. Mary's University, Halifax, Nova Scotia, Canada, B3H 3C3