P14 DESIGN STANDARDS FOR CRCP FOR EACH TEXAS ENVIRONMENTAL REGION Center for Transportation Research The University of Texas at Austin

Overview

Texas Temperature Data Collect annual maximum and minimum air temperature data 21 locations Possible data during last 20 years Divide Texas into 4 environmental zones based on average annual temperature range and geographic location

Selected Locations

Maximum Annual Temperature

Minimum Annual Temperature

Average Annual Temperature Range

Texas Environmental Zone

Concrete Temperatures Concrete Temperatures were calculated for each location and used for input values of CRCP program PavePro software – Use max. and min. annual temp. for input → conservative results – Maximum and zero stress concrete temperatures – Use default setting for mixture design and temperature distribution Equation from previous CTR research – Min. concrete temperature = A T – A T =minimum ambient temperature (deg.C)

Temperature Differential (  T)

Numerical Simulation using CRCP Variables for simulation VariableLevel Thickness 8 – 15 in. (1 in. increment) Thermal coefficient of concrete 4 X /°F 6 X /°F Steel Ratio0.4, 0.5, 0.6, 0.7%  T = zero stress temp – min. concrete temp 80 – 110 °F (5°F increment)

Numerical Simulation using CRCP Total 448 sets of data Use zero-stress temperatures as curing temperatures for simulation Find corresponding crack width for given conditions Provide data set for regression analysis

Regression Analysis Crack width = a X (  T) +b – where   T = temperature differential  a, b = coefficients Max. allowable crack width = in. Interpolate CRCP program output to find corresponding steel ratios for maximum allowable crack width for given conditions – Environmental region (Zone) – Thickness – Coefficient of Thermal Expansion (CoTE) of concrete

Sample Regression Results

Design Table for Longitudinal Reinforcement Design table for longitudinal reinforcement were developed. – Each environmental Zone – Max. allowable crack width = in. – Two CoTE of concrete 4 X /°F and 6 X /°F – Calculated longitudinal bar spacing based on No. 6 bar – Thickness = 8 – 15 in. (1-in. increment) – Assume double steel mat for 14 and 15-in. thick pavement

Longitudinal Steel Design Table: CoTE = 4 X /°F LONGITUDINAL STEEL SLAB THICKNESS REGULAR STEEL BARS AND BAR SIZE SPACING (IN.) THICKNESSBARCOTE**TEXAS ENVIRONMENTAL ZONE (IN.)SIZE( X /°F)1234 8# # # # # # *# *# *: DOUBLE STEEL MAT FOR 14 AND 15-IN. THICKNESS **: COTE = COEFFICIENT OF THERMAL EXPANSION OF CONCRETE

Longitudinal Steel Design Table: CoTE = 6 X /°F LONGITUDINAL STEEL SLAB THICKNESS REGULAR STEEL BARS AND BAR SIZE SPACING (IN.) THICKNESSBARCOTE**TEXAS ENVIRONMENTAL ZONE (IN.)SIZE( X /°F)1234 8# # # # # # *# *# *: DOUBLE STEEL MAT FOR 14 AND 15-IN. THICKNESS **: COTE = COEFFICIENT OF THERMAL EXPANSION OF CONCRETE

Summary The annual maximum and minimum air temperature data were collected from 21 locations in Texas. The State of Texas were divided into 4 environmental zones based on temperature history of selected locations. Maximum crack width were calculated by numerical simulation using maximum temperature differentials for selected locations. The corresponding longitudinal steel ratios were calculated by regression analysis. Design tables for longitudinal reinforcement were provided for each Texas environmental zone.