Nonlinear analysis of post-tensioned timber elements
File(s)
Author(s)
Melchor Placencia, Carlos Javier
Type
Thesis
Abstract
This thesis deals with the numerical simulation of the short- and long-term response of post-tensioned structural elements. It proposes and implements a numerical framework with particular orientation towards timber members and draped tendon profiles. The modelling approach employs beam-column finite elements with a fiber-based approach to incorporate the material nonlinearity and a corotational formulation to address the large displacements of the hosting member. Displacement-based beam-column elements considering traditional and enhanced-strain formulations as well as beam-column formulations with internal nodeless degrees of freedom were included in the proposed modelling approach. The proposed numerical framework incorporates the inelastic and time-dependent behaviour of wood and the prestressing steel. Prior to tackle the time-dependent response of the timber members, a moisture diffusion analysis using a finite difference scheme is carried out to assess the spatial and temporal distribution of moisture inside the members. The intricate behavior of unbonded tendons induce strain incompatibility and second-order effects adding more complexities into the numerical framework. To address these complexities, a constantly updated equivalent load scheme along with a resisting tendon element formulation involving the explicit derivation of a material and geometric tangent stiffness matrix were adopted. Additionally, a robust numerical formulation to assess the equilibrium state just after the prestress transfer is evaluated. As post-tensioned structures can experience sharp variations in their tangent stiffness matrices, robust numerical solvers were adopted to trace the whole global and local responses of interest. After validating the capabilities of the proposed numerical approach and carrying out several simulations to assess the influence of deviator spacing on the short- and long-term response of post-tensioned timber beams, this thesis demonstrates that the proposed modelling approach features versatility, numerical robustness and computational efficiency to a greater extent.
Version
Open Access
Date Issued
2024-04-30
Date Awarded
01/02/2025
License URL
Advisor
Málaga-Chuquitaype, Christian
Sponsor
PRONABEC
Grant Number
4285-201g-MINEDU/VMGT-PRONABEC-OBE
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)