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From page 302... ... 291 CHAPTER 6 - ANALYSIS RESULTS FOR SPS-2 EXPERIMENT 6.1 INTRODUCTION A summary of findings from all analyses conducted for the SPS-2 experiment is presented in this chapter. The relevant statistical methods and analysis procedures were explained in Chapter 4. Read the entire page →
From page 303... ... 292 6.2 PREVIOUS FINDINGS A review was performed on LTPP studies that have identified factors affecting rigid pavement response and performance. A brief summary of findings from these studies and reports relevant to SPS-2 is presented here. Read the entire page →
From page 304... ... 293 resting on stiff bases. Pavement sections located in freeze zones exhibited more roughness than pavements located in non-freeze zones. Read the entire page →
From page 305... ... 294 • With respect to IRI change, larger mean differences were detected for the PATB sections with "poor" drainage than for PATB sections with "good" drainage, when un-drained and drained sections were compared. The quality of drainage is not a significant factor in the differences observed in IRI increase. Read the entire page →
From page 306... ... 295 0 50 100 150 200 250 0 1 2 3 4 5 6 7 8 9 10 11 12 Age (years) Read the entire page →
From page 307... ... 296 0 50 100 150 200 250 300 0 1 2 3 4 5 6 7 8 9 10 11 12 Age (years) Read the entire page →
From page 308... ... 297 Roughness and Joint Faulting Figure 6 - 5 shows the progression of roughness over time in all the SPS-2 sections except NV (32) Read the entire page →
From page 309... ... 298 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 1 2 3 4 5 6 7 8 9 10 11 12 Age (years) Read the entire page →
From page 310... ... 299 Drainage Issues All the drained sections of the SPS-2 experiment were video taped to assess the condition of the drainage in the project NCHRP 1-34C [11] Read the entire page →
From page 311... ... 300 Table 6- 1 Subjective ratings of drainage functioning for SPS-2 test sections based on video inspection results (Hall et al [11] Read the entire page →
From page 312... ... 301 6.4 SITE-WIDE PERFORMANCE SUMMARIES This section summarizes the performance trends for each site within the SPS-2 experiment based on the latest available data (Release 17 of DataPave) at the time of writing this report. Read the entire page →
From page 313... ... 302 traffic volume is 1903 KESAL/ year. No "noticeable" distress was observed in sections 220, 221 and 223. Read the entire page →
From page 314... ... 303 Colorado, CO (8) This test site is located in Dry Freeze zone and was opened to traffic in November 1993. Read the entire page →
From page 315... ... 304 Transverse cracking, in 6% of slabs, occurred in section 217. Longitudinal cracking, of total length less than 5.0 m, occurred on sections 213, 222 and 224. Read the entire page →
From page 316... ... 305 Measurable faulting occurred at less than 20% of joints in all sections (in the experiment) except 216. Read the entire page →
From page 317... ... 306 Measurable faulting occurred at 20% to 35% of joints in sections 201, 202, 206, and 210. The initial roughness of the sections at this site ranged from 1.1 to 1.6 m/km. Read the entire page →
From page 318... ... 307 Washington, WA (53) This test site is located in Dry Freeze zone and was opened to traffic in November 1995. Read the entire page →
From page 319... ... 308 6.5 SITE-LEVEL ANALYSES This section of the report is a discussion of the results obtained from site-level analyses of the SPS-2 experiment data. The concepts of performance index (PI) Read the entire page →
From page 320... ... 309 In site-level analyses, statistical significance of an effect needs to be interpreted as the significance of the effect's consistency across sites but not necessarily as significance of its effect on the magnitude of distress. In this chapter, the discussion of results for level-A and level-B analyses is presented separately. Read the entire page →
From page 321... ... 310 Figure 6 - 7 Methodology for site-level analyses (SPS-2) Site Level Analysis Level-A Comparisons Level-B Comparisons Effect of Drainage Yes vs. Read the entire page →
From page 322... ... 311 6.5.1 Effect of design features on performance- Comparisons at level-A The discussion of results from level-A analyses is presented here. These results are presented taking one design feature at a time. Read the entire page →
From page 323... ... 312 Table 6-5 is the summary of the effects of base type on faulting and roughness. In general, the trend of faulting suggests higher faulting in the sections built on DGAB. Read the entire page →
From page 324... ... 313 Table 6- 2 Effects of drainage on cracking, based on Level-A analysis Design Factor Performance Measure Effect Comments Transverse cracking Inconclusive (p=0.299) • In 5 of the 14 sites, no cracking occurred and the performance of sections with and without drainage is thus similar. Read the entire page →
From page 325... ... 314 Table 6- 4 Effects of base type on cracking based on Level-A analysis Design Factor Performance Measure Effect Comments Transverse cracking Consistent effect (p= 0.000) • In all the 13 sites with distressed sections, higher cracking was observed in sections built on LCB, compared to other sections. Read the entire page →
From page 326... ... 315 PCC slab thickness A total of 84 sections with 203 mm (8-inch) PCC slab and 83 sections with 279 mm (11inch) Read the entire page →
From page 327... ... 316 Table 6- 6 Effects of slab thickness on cracking, based on Level-A analysis Design Factor Performance Measure Effect Comments Transverse cracking Consistent effect (p= 0.001) • In all sites that have distressed sections (13 sites) Read the entire page →
From page 328... ... 317 PCC flexural strength The performance of test sections with target 14-day PCC flexural strength of 3.8 MPa and test sections with target 14-day PCC strength of 6.2 MPa was compared to study the effect of PCC flexural strength on the performance of SPS-2 sections. A total of 84 sections with 3.8 MPa concrete and 83 sections with 6.2 MPa concrete were compared. Read the entire page →
From page 329... ... 318 Table 6- 8 Effects of flexural strength on cracking, based on Level-A analysis Design Factor Performance Measure Effect Comments Transverse cracking Inconclusive (p=0.400) • In 6 of the 14 sites, lower strength concrete sections exhibited higher cracking than higher strength concrete sections. Read the entire page →
From page 330... ... 319 Lane width The widened lane [4.3 m (14 ft) Read the entire page →
From page 331... ... 320 Table 6- 10 Effects of lane width on cracking based on Level-A analysis Design Factor Performance Measure Effect Comments Transverse cracking Inconclusive (p=0.222) • In 6 of the 14 sites, sections with standard lane exhibited higher cracking than ones with wider lane (4.3 m) Read the entire page →
From page 332... ... 321 6.5.2 Effect of design features- Paired Comparisons at Level-B Level-B comparisons are those in which all possible factors other than the one of interest are controlled. The individual sections that are compared under this analysis were identified in chapter 4. Read the entire page →
From page 333... ... 322 Table 6- 12 Effect of drainage on cracking, based on Level-B analysis Design Factor Performance Measure Effect Comments Transverse cracking Consistent effect (p=0.034) • At 5 of the 7 sites with distresses sections, among sections 203 mm (8") Read the entire page →
From page 334... ... 323 Base Type Sections built on each of the three base types, DGAB, LCB and PATB, were compared at each site by controlling the effects of PCC slab thickness and lane width. A consistent effect of base type on transverse and longitudinal cracking was observed. Read the entire page →
From page 335... ... 324 Table 6- 14 Effect of base type on cracking, based on Level B analysis Design Factor Performance Measure Effect Comments Transverse cracking Consistent effect (p<0.05) • In 9 sites, among thinner slab (203 mm) Read the entire page →
From page 336... ... 325 6.6 OVERALL ANALYSIS The results obtained from statistical analyses performed on the SPS-2 data are presented in this section. Both the performance and response variables were analyzed to study the effects of various design and site-factors on the pavement sections. Read the entire page →
From page 337... ... 326 measure for faulting. ANOVA method could not be applied to transverse and longitudinal cracking as the assumption of constant variance of residuals was violated owing to occurrence of cracking in not more than 30% of test sections. Read the entire page →
From page 338... ... 327 RESULTS FROM ANALYSES The following is a summary of the main findings from each method of analysis, categorized by performance measure and response indicator. Basic statistics pertaining to the extent of occurrence of distresses have been presented along with results to corroborate the results with data. Read the entire page →
From page 339... ... 328 c) PCC Slab Thickness: The percentage of test sections with 203 mm (8-inch) Read the entire page →
From page 340... ... 329 0 10 20 30 40 50 60 70 80 90 100 1 1.25 1.5 1.75 2 IRI, m/km P e r c e n t o f s e c t i o n s a b o v e DGAB LCB PATB (a) Base type 0 10 20 30 40 50 60 70 80 90 100 1 1.25 1.5 1.75 2 IRI m/km P e r c e n t o f s e c t i o n s a b o v e . Read the entire page →
From page 341... ... 330 6.6.2 Frequency-based Methods Two frequency-based methods were used- Linear Discriminant Analysis and Binary Logistic Regression (details in Chapter 4) Read the entire page →
From page 342... ... 331 Table 6- 18 Summary of results from LDA on transverse cracking- Overall Factor Category Factor Effects on transverse cracking p-value Drainage Presence of drainage significantly reduces the chances of occurrence of cracking Yes (0.001) Target PCC thickness Thicker (279 mm) Read the entire page →
From page 343... ... 332 Longitudinal cracking The effect of target PCC thickness, base type and the climatic zone are significant in discriminating between cracked and un-cracked sections. Table 6-20 summarizes the effect of the design and site factors on the occurrence of longitudinal cracking. Read the entire page →
From page 344... ... 333 Table 6- 20 Summary of results from LDA on longitudinal cracking Factor category Factor Effects on longitudinal cracking p-value Drainage No significant effect. Presence of drainage increases the chances of occurrence of cracking. Read the entire page →
From page 345... ... 334 Faulting None of the design or site factors are discriminating between sections with faulting and without faulting, at this point in time. Climate appears to have some effect (p-value= 0.098) Read the entire page →
From page 346... ... 335 Table 6- 22 Summary of LDA on Faulting Factor category Factor Effects on faulting p-value Drainage No significant effect. Presence of drainage decreases the chances of faulting. Read the entire page →
From page 347... ... 336 Table 6- 24 Summary of results from LDA on initial roughness, in WF zone Factor Effects on initial roughness p-value Drainage* No significant effect. Read the entire page →
From page 348... ... 337 Binary Logistic Regression (BLR) The BLR model was used to model the probability of occurrence for the various performance measures. Read the entire page →
From page 349... ... 338 From BLR on data from sections in WF zone, it was found that PCC slab thickness has a slight effect (p = 0.084) on cracking. Read the entire page →
From page 350... ... 339 Table 6- 27 Summary of p-values from BLR for determining the effect of experimental factors on pavement performance measures- Overall Roughness Experimental Factors Transverse cracking Longitudinal cracking Faulting Initial Current Drainage 0.083 (3.4) Read the entire page →
From page 351... ... 340 Roughness The BLR model for initial roughness was significant with a p-value of 0.023. Moreover, 61.5% of the times, the model correctly differentiates sections with "poor" roughness from other sections. Read the entire page →
From page 352... ... 341 6.6.3 Analysis of Variance ANOVA was performed on roughness and faulting of sections in the SPS-2 experiment. The procedure adopted for this analysis is the same as that for analysis of SPS-1 data. Read the entire page →
From page 353... ... 342 • Effect of PCC thickness: Significantly (practically and statistically) higher initial roughness was observed on sections with 279 mm (11") Read the entire page →
From page 354... ... 343 Table 6- 29 Summary of p-values from ANOVA for determining the effects of design factors on pavement performance−Overall Roughness (IRI) Factor Faulting ∆IRI IRIo Drainage 0.477 0.002* Read the entire page →
From page 355... ... 344 Similar ANOVA was performed on data from sections in the WF zone and Table 6- 31 is the summary of results from the analysis. Table 6- 32 shows the back transformed marginal means for all levels of design factors. Read the entire page →
From page 356... ... 345 Table 6- 31 Summary of p-values from ANOVA for determining the effects of design factors on pavement performance−WF Zone Roughness (IRI) Factor Faulting ∆IRI IRIi Drainage 0.420 0.012* Read the entire page →
From page 357... ... 346 Effect of Site Factors on Pavement Performance Given the unbalanced nature of the experimental design with respect to climatic zone, a one-way ANOVA was performed study the main effects of the subgrade soil type (fine-grained versus coarse-grained soils) and climatic zone (wet versus dry, freeze versus no-freeze) Read the entire page →
From page 358... ... 347 Table 6- 33 Summary of p-values from one-way ANOVA for determining the effect of site factors on pavement performance measures Roughness (IRI) Site Factor Faulting ∆IRI IRIi Subgrade Fine-grained vs. Read the entire page →
From page 359... ... 348 Effect of Design Factors on Pavement Performance based on standard deviates As explained before in Chapter 4, the experiment design and the performance of the test sections have rendered the SPS-2 experiment unbalanced (statistical) Read the entire page →
From page 360... ... 349 As mentioned earlier, these comparisons were performed only on roughness, and faulting. The method is not appropriate for cracking because of "low" occurrence of the distresses at this point in time. Read the entire page →
From page 361... ... 350 PCC slab thickness: The effect of PCC slab thickness is significant (statistical and operational) among sections built on fine-grained soils, especially when constructed in WF zone. Read the entire page →
From page 363... ... 352 Table 6- 35 Summary of p-values for comparisons of standard deviates -- Change in roughness By subgrade By climatic zone By subgrade and zone WF WNF DF DNF Design Factor Comparison Overall Fine Coarse WF WNF DF DNF F C F C F C F C Drainage Drainage vs. No-Drainage 0.000 0.009 0.002 0.052 0.024 0.004 0.084 0.071 0.497 0.297 0.048 0.051 0.084 Base type DGAB vs. Read the entire page →
From page 364... ... 353 Faulting The effects of the design and site factors on faulting, in terms of standard deviate, are shown in Figure 6-10. The number of joints that faulted more than 1.0 mm was considered as the performance measure for PI, and the standard deviate is based on PI. Read the entire page →
From page 366... ... 355 Table 6- 37 Summary of p-values for comparisons of standard deviates -- Faulting By subgrade By climatic zone By subgrade and zone WF WNF DF DNF Design Factor Comparison Overall Fine Coarse WF WNF DF DNF F C F C F C F C Drainage Drainage vs. No-Drainage 0.459 0.228 0.796 0.297 0.780 0.296 0.49 0.057 0.315 0.561 0.407 0.989 0.469 Base type DGAB vs. Read the entire page →
From page 367... ... This page is intentionally left blank. Read the entire page →
From page 368... ... 357 6.6.4 Effect of Experimental Factors on Pavement Response As mentioned earlier, the dependent variables that were considered for the ANOVA on pavement response include deflections do, d6, Area Factor (AF) and Effective Stiffness (ES) Read the entire page →
From page 369... ... 358 located in WF zone, those with 203 mm PCC slab have shown significantly higher deflections than those with 279 mm PCC slab thickness. These results imply that the design factors significantly interact over time to affect d0, unlike in the initial conditions where only the main effects of design factors were important. Read the entire page →
From page 370... ... 359 When the effects of design features on final survey AF were studied by blocking the site factors, the main effects of PCC slab thickness (p=0.001) , and PCC flexural strength (p=0.024) Read the entire page →
From page 371... ... 360 Table 6- 39 Summary of p-values for the effects of design factors on rigid pavement response do d6 Area Factor Effective stiffness of PCC slab Design Factor Initial Final Initial Final Initial Final Initial Final Drainage 0.000 0.000 0.002 0.002 0.352 0.922 0.234 0.050 PCC thickness 0.000 0.000 0.000 0.002 0.000 0.001 0.000 0.000 Base Type 0.000 0.000 0.000 0.006 0.387 0.863 0.000 0.016 PCC Flexural Strength 0.948 0.550 0.746 0. 602 0.300 0.024 0.586 0.021 Lane Width 0.425 0.327 0.186 0.941 0.673 0.609 0.570 0.366 Site (blocked) Read the entire page →
From page 372... ... 361 6.7 APPARENT RELATIONSHIP BETWEEN RESPONSE AND PERFORMANCE In this section of the report the observations regarding apparent relationships between rigid pavement response (FWD testing) and performance are presented. Read the entire page →
From page 373... ... 362 Figure 6-11 through Figure 6-16 are examples of bivariate relationships between Effective Stiffness (ES) , Area Factor (AF) Read the entire page →
From page 374... ... 363 y = -3E-06x + 1.9165 R2 = 0.3448 0 0.5 1 1.5 2 0 100000 200000 300000 400000 Effective Stiffness (psi) Read the entire page →
From page 375... ... 364 Table 6- 41 Summary of correlations for deflections and DBPs with IRI State ID State Do AF ES Zone SG 10 DE -0.29 0.53 0.36 WF C 19 IA 0.26 0.18 -0.09 WF F 20 KS -0.38 -0.36 0.24 WF F 26 MI -0.05 -0.38 -0.27 WF F 38 ND -0.44 0.30 0.23 WF F 39 OH 0.41 -0.03 -0.32 WF F 55 WI 0.31 -0.25 -0.42 WF C 5 AR 0.37 0.31 0.00 WNF C 37 NC -0.19 0.53 0.66 WNF F 8 CO -0.37 -0.27 0.02 DF F 53 WA -0.42 -0.55 -0.44 DF F 4 AZ 0.22 -0.43 -0.58 DNF C 6 CA -0.56 0.04 0.04 DNF C (-) Read the entire page →
From page 376... ... 365 6.7.2 Relationship between strain and performance This section is regarding the Dynamic Load Response (DLR) of the instrumented rigid pavement sections in the states of Ohio and North Carolina. Read the entire page →
From page 377... ... 366 6.8 SYNTHESIS OF ANALYSES RESULTS FOR RIGID PAVEMENTS This section of the report summarizes all the findings from various analyses performed on SPS-2 data. The methods employed in this study were explained in Chapter 4 and the results obtained from these analyses were presented in this chapter. Read the entire page →
From page 378... ... 367 The synthesis of results is presented next, separately for each performance measure. A ‘simple' summary of results from all analyses is Read the entire page →
From page 379... ... This page is intentionally left blank. Read the entire page →
From page 380... ... 369 Table 6- 42. The summary is only meant to give the reader an idea about the effects. Read the entire page →
From page 381... ... 370 PCC slab thickness and base type seem to be the most important factors affecting the occurrence of transverse cracking, whereas, drainage seems to have a marginal effect. The occurrence of transverse cracking among pavements with 203 mm (8-inch) Read the entire page →
From page 382... ... 371 The extent of faulting among the test sections is "low", with 62% of the sections having no joints with faulting greater than 1 mm. Only 33% of the sections have 0 to 20% of the joints that faulted more than 1.0 mm, and just 5% of the sections have more than 20% of the joints that faulted more than 1.0 mm. Read the entire page →
From page 383... ... 372 The initial roughness (smoothness) of the pavement sections in the experiment seems to be affected by the PCC slab thickness. Read the entire page →
From page 384... ... 373 The sections constructed on DGAB have shown significantly higher deflections than the ones constructed on PATB. The sections constructed on LCB experienced the least amount of deflections. Read the entire page →
From page 385... ... 374 significantly higher ES values compared to those located in "dry" climate. The sections built on coarse-grained subgrade soil were significantly stiffer than those built on fine-grained soil. Read the entire page →
From page 386... ... 375 Table 6- 42 Summary of effects of design and site factors for rigid pavements Performance Measures Response Measures (initial) Design Factor Transverse cracking Longitudinal cracking Faulting Roughness do d6 AF ES Drainage PCC thickness Base type Flexural Strength Lane Width Climatic Zone Subgrade type Note: This table is solely for the purpose of summarizing some of the effects in a ‘simple' format. Read the entire page →

From page 302...

... 291 CHAPTER 6 - ANALYSIS RESULTS FOR SPS-2 EXPERIMENT 6.1 INTRODUCTION A summary of findings from all analyses conducted for the SPS-2 experiment is presented in this chapter. The relevant statistical methods and analysis procedures were explained in Chapter 4.