Role of Early-Age Concrete Properties and Construction Loading on Slab Serviceability

Open Access
Author:
Lee, Je Il
Graduate Program:
Civil Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 10, 2007
Committee Members:
  • Andrew Scanlon, Committee Chair
  • Andrea J Schokker, Committee Member
  • Maria Lopez De Murphy, Committee Member
  • Ali M Memari, Committee Member
  • Peggy Ann Johnson, Committee Member
Keywords:
  • slab
  • construction load
  • early-age
  • finite element analysis
  • concrete
  • experiment
Abstract:
The slab is modeled using a shell element in the commercial finite element software package ABAQUS/Standard. To idealize material behavior a user-defined subroutine (UMAT) is developed. Time-dependent creep and shrinkage effects in concrete material are also incorporated to the subroutine. Recently proposed creep and shrinkage models are implemented along with tension stiffening models in a general purpose computer program for analysis of concrete slabs under sustained time-dependent loading. Laboratory tests on nine simply supported one-way reinforced concrete members subjected to sustained load was performed. Each specimen was subjected to immediate full live again after six months. Applied load and mid-span deflections were recorded under immediate live load and sustained load. The test results demonstrated the effect of shrinkage restraint provided by embedded bars on the flexural cracking of the specimens under applied load, as well as effects of early age loading on time-dependent response. Results of an analytical study of reinforced concrete two-way slab systems are also presented. Numerical results which are obtained using the developed time-dependent concrete model were compared with available experimental results. The results show good correlations between analysis and tests in terms of load-deflection and deflection histories. A parametric study is carried out in order to investigate the various factors affecting slab deflections.