Impact of Pile Head Rigidity on the Response of Piled Raft in Sand Under Pseudo-Static Loading
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TECHNICAL NOTE
Impact of Pile Head Rigidity on the Response of Piled Raft in Sand Under Pseudo-Static Loading Prasun Halder1
•
Bappaditya Manna1 • Arnab Sur1
Received: 9 September 2019 / Accepted: 3 January 2020 Indian Geotechnical Society 2020
Abstract The 3D finite element simulations are carried out to study the impact of different pile head connection conditions, i.e., rigid and hinged connection on the response of piled rafts in sand subjected to pseudo-static horizontal loading. The time-acceleration histories of Assam (2014), Bhuj (2001), Sikkim (2011) and Uttarkashi (1991) earthquakes are considered to calculate the horizontal pseudostatic loads. Analyses results confirm that pile head connection rigidity greatly influences the behavior of piled raft in many aspects. The horizontal stiffness of piled raft is found to decrease as the rigid pile head connection changes to hinged one. Piles in a piled raft foundation is found to carry about 52–75% of the pseudo-static horizontal load for rigid connection and 32–48% for hinged connection. The horizontal deflection of pile is found maximum at the pile head and becomes negligible along the depth of pile for both cases. For rigidly connected piles, the maximum bending moment occurs at the pile head, whereas piles with hinged connection show zero bending moment at top and maximum value at a certain depth from pile head. Keywords Piled raft Connection rigidity Pseudo-static load Horizontal deflection Bending moment Finite element
& Prasun Halder [email protected] Bappaditya Manna [email protected] Arnab Sur [email protected] 1
Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
Introduction The utilization of piled raft foundation for the high-rise buildings has widely been accepted as an effective and economic foundation solution across the world for the last two and half decades. Such recognition is predominantly because of the facility of simultaneous load sharing between the raft and piles under vertical load. As a result, the settlement of the raft can be reduced to acceptable limit by using the piles as settlement reducers. With the growth of urbanization, the performance evaluation of piled raft subjected to horizontal loading or, seismic loading has become essential in seismic design of piled rafts. In this regard, the connection rigidity of pile heads (rigid and hinged) with the raft plays an important role to influence the behavior of piled raft subjected to horizontal load [1–3]. The complex interaction among the pile, raft and subsoil also contributes in defining the load-settlement behavior, load sharing and the structural responses of piles and raft under horizontal loading. The behaviors of fixed and hinged piled raft are not similar upon loading as they are constructed in a different manner in the field. The fixed piled raft is used for the foundations of medium to high-rise buildings, bridges, etc. The fixed head condition refers to the case when the deflection
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