Tapered plate dowels for jointed concrete slabs

Jadallah, Omar Abderahim Omar

Permalink

https://hdl.handle.net/2142/121933 Copy

Description

Title

Tapered plate dowels for jointed concrete slabs

Author(s)

Jadallah, Omar Abderahim Omar

Issue Date

2023-08-18

Director of Research (if dissertation) or Advisor (if thesis)

Roesler, Jeffery R

Doctoral Committee Chair(s)

Roesler, Jeffery R

Committee Member(s)

• Al-Qadi, Imad L
• Henschen, Jacob D
• Garg, Nishant
• Hajj, Ramez M
• Khazanovich, Lev

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Tapered plate dowel
• joints
• slab on grade
• concrete pavement
• Load transfer devices
• modulus of dowel support

Abstract

In jointed concrete slab systems, dowel bars are used to enhance the long-term load transfer efficiency at joints. Plate dowels were introduced in the 1990’s, followed by several additional tapered plate dowel (TPD) geometries. Tapered dowels were first introduced to minimize two-way restraint that can result from prismatic dowels in jointed slabs, particularly in the case of misaligned dowel placement. Plate dowels also provide an alternative to round dowel bars by lower bearing stresses and differential deflections through larger concrete-dowel area. Few published studies exist in the literature on the experimental and theoretical responses and performances of TPDs. In this thesis, a large-scale experimental investigation using a slab-dowel test setup was conducted to compare the performance of three different TPD geometries, the elongated diamond dowel (EDD), the trapezoidal dowel (TRAP), and the hexagonal dowel (HEX). Each geometry was tested at three levels of longitudinal joint offsets, 0-,1-, and 2-inch. Tests showed a maximum difference in deflections between all dowel geometries and offset levels of 20%. The differences in deflections were relatively small given a change in dowel width at joint that ranged from 2 to 3 inches and embedded lengths from 3.65 to 6 inches. Experimental results also showed a large change in the dowel’s ultimate failure capacity (punching shear capacity) as a result of concrete breakout with an 82% maximum difference between dowel type and offset. 2-D and 3-D FEM models were developed to simulate the experimental test setup and estimate the critical dowel responses. The 2-D simulation was composed of shell elements that modeled the steel dowels with proper geometric and material inputs resting on an elastic foundation. This did not produce better deflection responses than beam on elastic foundation analytical solutions, i.e., 1-D Friberg’s analysis. The 3-D FEM model best represented the test setup, load configuration, boundary conditions, and actual slab and dowel geometric and material inputs. Deflection profiles of 3-D models correlated well with the deflection profile of the TPD tests in the service load range, e.g., 2,000 lbf. These simulations showed maximum deflection differences at the dowel-slab face to be approximately 10% between all TPD test cases. In the 3-D FEM models, normal stress and corresponding deflection were extracted at the slab face and used to backcalculate modulus of dowel support, K, for 1-D Friberg’s analysis. Friberg solutions were then used to calculate critical dowel responses of the various TPD cases. The largest variation in the 1-D critical responses was in the bearing stresses between TPD geometries and offsets. The EDD dowels resulted in the largest change in responses between offset levels, while the TRAP showed the least. Additionally, when compared with round dowel, bearing stress levels of TPDs were significantly lower. A method to calculate punch shear capacity (PSC) of TPDs was successfully developed using equations for breakout strength of anchors in precast concrete slabs. The accuracy of the proposed PSC solution was compared with 81 TPD test data taken from this study and others from 2017 that used a similar test setup. The key design inputs for the PSC equation were dowel embedment length, embedded dowel average width, concrete strength, and concrete cover depth. While the geometry of dowels did result in significant changes in PSC, particularly with offset, PSC was much more sensitive to concrete strength and slab thickness. A predictive equation to calculate dowel-concrete support Ks for Friberg analysis using a multivariate linear regression analysis was completed. A total of 24 3-D FEM simulations were used, with variables including dowel dimensions, joint offset level, concrete cover thickness, and concrete elastic modulus. The results of the predictive equation showed an average error level of 5% with an R2 equal to 99.6%. This K calculator allows for rapid estimation of support values for a 1-D dowel analysis for a given set of TPD inputs.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Omar Jadallah

Owning Collections