ACI 318 CODE PROVISIONS FOR DEFLECTION CONTROL OF TWO-WAY CONCRETE SLABS

Open Access
Author:
Gullapalli, Anusha Venkata Lakshmi
Graduate Program:
Civil Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 13, 2009
Committee Members:
  • Andrew Scanlon, Thesis Advisor
Keywords:
  • parametric study
  • recommendations
  • revision
  • deflection
  • two-way slabs
  • concrete
  • ACI 318
Abstract:
The objective of the study conducted was to identify and address concerns with ACI 318 section 9.5, the deflection specifications for two-way slabs. Its scope includes proposing the inclusion of two new equations: to compute effective moment of inertia by Bischoff (2005) and Bischoff and Scanlon (2007) and to calculate minimum thickness required for a two-way slab by Scanlon and Choi (1999) respectively. For the purpose of studying the merits of using a proposed moment of inertia by Bischoff, as against the existing ACI specified equation, an experimental plan was developed to observe the effect of percentage of reinforcement on the moment resisting capacity and deflection of the section. Parametric studies were conducted to study the effect of percentage reinforcement on the effective moment of inertia of the section by proposed and ACI methods. Studies were also carried out to analyze the effect of various factors including live load, sustained load, span length, long-term multiplier, etc on the minimum thickness requirements of a two-way slab, unsupported by drop panels. Effects of inclusion of boundary condition factor in the proposed hmin equation were studied and justified using SAP2000 software. The results of the experiments and parametric studies were analyzed using the MS-EXCEL software and a characteristic behavior pattern was developed over the range of parameters for each study. The behavior pattern thus obtained was then used to rationalize the use of proposed equations. Finally a detailed analysis is carried out on the studies and experiments and conclusions were drawn. These conclusions are further formatted to satisfy the ACI code language, since they are to be implemented upon approval by the presiding committee, as a modification/addition to the existing deflection control provisions of ACI 318 section 9.5, concerning two-way slabs.