Conference Papers
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Item Analysis of Cushion Effects in Unconnected Piled Raft Foundation(Springer Science and Business Media Deutschland GmbH, 2022) Amalu, P.A.; Jayalekshmi, B.R.The piled raft foundations are an economical solution as well as a settlement reducer in the construction of high-rise buildings. Unconnected piled raft foundation is an innovative technique where a cushion separates the pile and raft. The cushion takes the load transferred from the raft and safely distributes over the piles beneath. This article analyses the seismic behaviour of connected and unconnected piled raft foundation of a multistorey building using ANSYS software based on the finite element method. An 8 m × 8 m × 1 m raft and 0.4 m × 0.4 m square concrete piles with depth of 12 m resting on a very soft clay stratum were modelled. The soil block of 16 m × 16 m plan dimension with a depth of 16 m was provided with transmitting boundaries at all lateral edges with properties corresponding to shear wave velocity of clay (150 m/s) and was analysed for the response under the ground motion corresponding to El Centro 1940 earthquake. The building load acting on the raft was considered as a uniformly distributed load of 0.2 MPa. The vertical and lateral displacements at the top of the raft were analysed with cushions having different elastic modulus and thickness. An increase in the elastic modulus of cushion tends to reduce the settlement considerably whereas, a positive correlation was observed between the depth of cushion layer and corresponding settlement. It is evident from the results of the numerical analysis that the stiffness of cushion layer and thickness are two important aspects which determine the displacements of unconnected piled raft systems. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item A Review on Behavior of Piled Raft Foundations Under Various Loads(Springer Science and Business Media Deutschland GmbH, 2022) Amalu, P.A.; Jayalekshmi, B.R.Piled raft foundations are a combined system of deep foundation and shallow foundation. In this type of foundation systems, the pile footings are provided beneath a raft or mat footing. Thus, the piled raft foundations can be constructed either by providing raft foundation connected to the pile footings or by providing a cushion layer between raft and pile footings. The first type of piled raft foundation is generally termed as connected piled raft foundations, and the latter piled raft foundations. Piled raft foundations is termed as disconnected can be subjected to different types of loadings, like vertical and inclined loading depending on the type of superstructure, lateral loading induced by earth pressure as well as seismic loads and moments induced by the eccentricity in loadings. Numerous studies have been conducted on the behavior of piled raft foundations under independent and combined effects of these loadings. This article aims to summarize these literature works to review the behavior of piled raft foundations under static and dynamic loadings acting in different directions. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Seismic Analysis of Piled-Raft Foundations in Mid-Rise Buildings on Soft Soil(Springer Science and Business Media Deutschland GmbH, 2024) Amalu, P.A.; Jayalekshmi, B.R.The utilization of piled-raft foundations is prevalent in buildings constructed on soft soil to mitigate settlement and increase bearing capacity. Nevertheless, if dynamic loading is not suitably considered during the design phase, these foundations may fail. This investigation utilizes three-dimensional finite element analyses in OpenSees to explore the seismic behaviour of mid-rise buildings with piled-raft foundations founded on soft soil. The principal focus of this study is on the influence of soil-foundation-structure interactions (SFSIs) under earthquake loadings. For this purpose, the El-Centro 1979 earthquake was used as the base acceleration underneath the soil layer to simulate the seismic conditions. The study scrutinizes the influence of pile flexural rigidity and superstructure configuration (G + 2, G + 4, G + 7) on the responses of mid-rise buildings on piled-raft foundations under earthquake loading. The findings revealed that buildings with a higher number of floors exhibit larger inter-storey drift with consideration of SFSI. Additionally, an increase in pile flexural rigidity significantly diminishes lateral displacements and shear force during earthquake loading. This study highlights that the flexural rigidity of pile and superstructure configuration are two pivotal factors that determine the response of piled-raft foundations of mid-rise buildings under earthquake loading. Proper consideration of these factors during the design phase can help mitigate the risk of failure and improve the performance of buildings with piled-raft foundations founded in soft soil. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.