Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1403074
Q. Li, A. Stuedlein, A. Marinucci
Steel casing is commonly used in drilled shaft construction to maintain the integrity of the borehole during drilling; however, little guidance regarding the effect of the casing on axial load transfer exists in the literature. To address this aspect of drilled shaft design and construction, this paper presents a study of axial load transfer of drilled shaft foundations using four, full-scale, instrumented drilled shafts: two uncased and two cased drilled shafts. Axial loading tests were performed and used to compare various performance metrics between the cased and uncased shafts, including the axial load-displacement curves, load transfer distributions and back-calculated unit shaft resistance-relative displacement relationships (t-z curves). The uncased test shafts exhibited significantly greater axial shaft resistance compared to the cased test shafts, and data from thermal integrity profiler (TIP) sensors allowed interpretation of the differences in soil-shaft contact conditions and the resulting load transfer. Although the ultimate axial resistance of the uncased test shafts could not be mobilised, sufficient data were developed to allow comparison to the cased test shafts and extrapolation to anticipated ultimate resistance conditions. The back-calculated t-z curves of the uncased test shafts were modelled and used to estimate the anticipated large deformation response. Based on observations in this study and those previously reported, the effects of permanent casing on axial load transfer are summarised to provide an up-to-date reference on the reductions expected based on construction sequencing and installation methods.
{"title":"Axial load transfer of drilled shaft foundations with and without steel casing","authors":"Q. Li, A. Stuedlein, A. Marinucci","doi":"10.1080/19375247.2017.1403074","DOIUrl":"https://doi.org/10.1080/19375247.2017.1403074","url":null,"abstract":"Steel casing is commonly used in drilled shaft construction to maintain the integrity of the borehole during drilling; however, little guidance regarding the effect of the casing on axial load transfer exists in the literature. To address this aspect of drilled shaft design and construction, this paper presents a study of axial load transfer of drilled shaft foundations using four, full-scale, instrumented drilled shafts: two uncased and two cased drilled shafts. Axial loading tests were performed and used to compare various performance metrics between the cased and uncased shafts, including the axial load-displacement curves, load transfer distributions and back-calculated unit shaft resistance-relative displacement relationships (t-z curves). The uncased test shafts exhibited significantly greater axial shaft resistance compared to the cased test shafts, and data from thermal integrity profiler (TIP) sensors allowed interpretation of the differences in soil-shaft contact conditions and the resulting load transfer. Although the ultimate axial resistance of the uncased test shafts could not be mobilised, sufficient data were developed to allow comparison to the cased test shafts and extrapolation to anticipated ultimate resistance conditions. The back-calculated t-z curves of the uncased test shafts were modelled and used to estimate the anticipated large deformation response. Based on observations in this study and those previously reported, the effects of permanent casing on axial load transfer are summarised to provide an up-to-date reference on the reductions expected based on construction sequencing and installation methods.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133822016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1414108
A. B. Cerato, T. Vargas, S. Allred
Helical piles are being used in seismic regions of the U.S. and other countries, yet there remains much confusion regarding the state of practice and building codes for this pile type. Nonetheless, it is anticipated that piles with comparatively small cross-section and high anchoring capacity, such as helical piles, could be beneficial for seismic resistance due to their slenderness, higher damping ratios, ductility, and resistance to tip uplift. In addition, helical piles can be easily implemented as a retrofitting solution for foundations that are found to be deficient according to updated seismic codes. This paper is part of three phase investigation on the use of helical piles for earthquake mitigation. The results of an extensive literature and industry search for previous seismic tests performed on helical piles are highlighted as well as the current design standards used in seismic regions. Existing seismic testing results and current design standards are analysed to make recommendations about how to fill the knowledge gaps and provide quantitative data on the behaviour of helical piles under seismic conditions.
{"title":"A critical review: State of knowledge in seismic behaviour of helical piles","authors":"A. B. Cerato, T. Vargas, S. Allred","doi":"10.1080/19375247.2017.1414108","DOIUrl":"https://doi.org/10.1080/19375247.2017.1414108","url":null,"abstract":"Helical piles are being used in seismic regions of the U.S. and other countries, yet there remains much confusion regarding the state of practice and building codes for this pile type. Nonetheless, it is anticipated that piles with comparatively small cross-section and high anchoring capacity, such as helical piles, could be beneficial for seismic resistance due to their slenderness, higher damping ratios, ductility, and resistance to tip uplift. In addition, helical piles can be easily implemented as a retrofitting solution for foundations that are found to be deficient according to updated seismic codes. This paper is part of three phase investigation on the use of helical piles for earthquake mitigation. The results of an extensive literature and industry search for previous seismic tests performed on helical piles are highlighted as well as the current design standards used in seismic regions. Existing seismic testing results and current design standards are analysed to make recommendations about how to fill the knowledge gaps and provide quantitative data on the behaviour of helical piles under seismic conditions.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"672 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116103541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1420015
Anne Lemnitzer, Timothy C. Siegel
This issue addresses a timely and broad array of pile-related subjects ranging from battered piles in embankments, seismic behaviour of helical piles, cased and uncased drilled shaft behaviour as well as the performance of soil nails for slope stabilisation. Jehu Johnson and his co-authors present the results of numerical simulations of T-walls supported by battered piles within levee embankments. This research resulted, in part, from the heightened awareness of the performance of levee embankments after the failures associated with Hurricane Katrina in New Orleans, Louisiana. The authors performed an extensive amount of numerical two dimensional finitedifference simulations to investigate the effects of various parameters on Settlement-Induced Bending Moment T-walls with batter piles. A specific focus of the study addressed the effect of structural head fixity and associated moment loading. The authors identified a linear relationship between the batter angle and pile bending moment for the conditions and range of batter angles investigated and a reduction of pile bending moment for pile batters when aligning closer to vertical. Qiang Li, Armin Stuedlein, and Tony Marinucci compare the performance of side resistances for drilled shafts with and without casing using four full-scale, instrumented drilled shafts. Such data are vital given the great importance in quantifying the impact of construction techniques during design. The authors utilise data from thermal integrity profiler sensors to interpret the differences in soil-shaft contact conditions and the resulting load transfer. The uncased test shafts exhibited significantly greater axial shaft resistance compared to the cased test shafts. Important performance metrics between the cased and uncased shafts, including the axial load–displacement curves, load transfer distributions, and back-calculated unit shaft resistance–relative displacement relationships (t–z curves) are presented in full detail. Alireza Askari and Arash Gholami conduct 3D numerical parametric studies to investigate the effects of soil nail length and orientation on various segments of a slope. Parametric variations include the slope height and the surcharge pressure. The authors provide recommendations for optimising the nail geometry in the upper, middle and lower parts of the slope and show under which angular orientation the maximum performance can be expected. Amy Cerato, Tatjana Vargas and Shawn Allred close this issue with an in-depth review of the state-of-knowledge on the seismic behaviour of helical piles. Given the growing application of helical piles, Dr Cerato’s paper is well timed to provide needed assistance to designers. This work is part of a three phase investigation on the use of helical piles for earthquake mitigation and identifies future research needs in the light of seismic retrofit requirements. The results of an extensive literature and industry search for previous seismic tests performed on helical
{"title":"Editors’ Note","authors":"Anne Lemnitzer, Timothy C. Siegel","doi":"10.1080/19375247.2017.1420015","DOIUrl":"https://doi.org/10.1080/19375247.2017.1420015","url":null,"abstract":"This issue addresses a timely and broad array of pile-related subjects ranging from battered piles in embankments, seismic behaviour of helical piles, cased and uncased drilled shaft behaviour as well as the performance of soil nails for slope stabilisation. Jehu Johnson and his co-authors present the results of numerical simulations of T-walls supported by battered piles within levee embankments. This research resulted, in part, from the heightened awareness of the performance of levee embankments after the failures associated with Hurricane Katrina in New Orleans, Louisiana. The authors performed an extensive amount of numerical two dimensional finitedifference simulations to investigate the effects of various parameters on Settlement-Induced Bending Moment T-walls with batter piles. A specific focus of the study addressed the effect of structural head fixity and associated moment loading. The authors identified a linear relationship between the batter angle and pile bending moment for the conditions and range of batter angles investigated and a reduction of pile bending moment for pile batters when aligning closer to vertical. Qiang Li, Armin Stuedlein, and Tony Marinucci compare the performance of side resistances for drilled shafts with and without casing using four full-scale, instrumented drilled shafts. Such data are vital given the great importance in quantifying the impact of construction techniques during design. The authors utilise data from thermal integrity profiler sensors to interpret the differences in soil-shaft contact conditions and the resulting load transfer. The uncased test shafts exhibited significantly greater axial shaft resistance compared to the cased test shafts. Important performance metrics between the cased and uncased shafts, including the axial load–displacement curves, load transfer distributions, and back-calculated unit shaft resistance–relative displacement relationships (t–z curves) are presented in full detail. Alireza Askari and Arash Gholami conduct 3D numerical parametric studies to investigate the effects of soil nail length and orientation on various segments of a slope. Parametric variations include the slope height and the surcharge pressure. The authors provide recommendations for optimising the nail geometry in the upper, middle and lower parts of the slope and show under which angular orientation the maximum performance can be expected. Amy Cerato, Tatjana Vargas and Shawn Allred close this issue with an in-depth review of the state-of-knowledge on the seismic behaviour of helical piles. Given the growing application of helical piles, Dr Cerato’s paper is well timed to provide needed assistance to designers. This work is part of a three phase investigation on the use of helical piles for earthquake mitigation and identifies future research needs in the light of seismic retrofit requirements. The results of an extensive literature and industry search for previous seismic tests performed on helical","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115034637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1416569
A. Askari, A. Gholami
In the present paper, a numerical study of optimum soil-nailed layouts under different conditions is performed. Nailed slopes of three geometries under two surcharge scenarios are considered in terms of safety factor and the wall top displacement. Effects of different segments along the height of the slope on safety factor and the wall top displacement are evaluated. In vertical soil-nailed slopes, maximum safety factor is calculated at the nail orientation angles between 0° and 10°. In all soil-nailed slopes, after a specified nail length (reduction point), an increase in the nail’s length will not affect the wall top displacement. The upper one-third of the slope is found to have the largest effects on the wall top displacement, while the lower one-third of the slope has the most significant effect on the safety factor.
{"title":"Effect of nail’s orientation and length on soil-nailed retaining structures’ stability","authors":"A. Askari, A. Gholami","doi":"10.1080/19375247.2017.1416569","DOIUrl":"https://doi.org/10.1080/19375247.2017.1416569","url":null,"abstract":"In the present paper, a numerical study of optimum soil-nailed layouts under different conditions is performed. Nailed slopes of three geometries under two surcharge scenarios are considered in terms of safety factor and the wall top displacement. Effects of different segments along the height of the slope on safety factor and the wall top displacement are evaluated. In vertical soil-nailed slopes, maximum safety factor is calculated at the nail orientation angles between 0° and 10°. In all soil-nailed slopes, after a specified nail length (reduction point), an increase in the nail’s length will not affect the wall top displacement. The upper one-third of the slope is found to have the largest effects on the wall top displacement, while the lower one-third of the slope has the most significant effect on the safety factor.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129316226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1376369
J. Johnson, F. Vahedifard, P. Kokkali, A. Tessari, T. Abdoun, R. J. Varuso
After catastrophic levee failures triggered by the 2005 Hurricane Katrina, concrete T-walls with batter piles are extensively used to enhance the integrity of levees in the New Orleans area. Since the foundation soils in this region typically include soft and compressible clays, T-walls with batter piles should be designed to account for bending moments and stresses induced by settlement. However, the current T-wall design procedure for estimating these settlement-induced bending moments (SIBMs) only takes a limited range of conditions into consideration. This paper presents results from a series of finite-difference numerical simulations to investigate the effects of various parameters on SIBM in pile-supported T-walls. The numerical model was first used to simulate a centrifuge test and upon comparison, a reasonable agreement was observed between the numerical simulation and experimental results. The numerical model was then used to investigate the effects of different parameters including pile connection fixity, batter, and stiffness of the pile on SIBM. The simulation results showed that the fixed connection greatly increases the bending moment compared to the pinned case. The difference in the maximum bending moment due to different pile batters can be approximated linearly. However, the results showed that changes in the maximum bending moment versus pile stiffness do not follow a linear pattern. Findings of this research can be used to validate or identify the need for possible adjustments in the current T-wall modelling and design methodologies.
{"title":"Numerical simulation of T-walls supported by batter piles within a levee embankment","authors":"J. Johnson, F. Vahedifard, P. Kokkali, A. Tessari, T. Abdoun, R. J. Varuso","doi":"10.1080/19375247.2017.1376369","DOIUrl":"https://doi.org/10.1080/19375247.2017.1376369","url":null,"abstract":"After catastrophic levee failures triggered by the 2005 Hurricane Katrina, concrete T-walls with batter piles are extensively used to enhance the integrity of levees in the New Orleans area. Since the foundation soils in this region typically include soft and compressible clays, T-walls with batter piles should be designed to account for bending moments and stresses induced by settlement. However, the current T-wall design procedure for estimating these settlement-induced bending moments (SIBMs) only takes a limited range of conditions into consideration. This paper presents results from a series of finite-difference numerical simulations to investigate the effects of various parameters on SIBM in pile-supported T-walls. The numerical model was first used to simulate a centrifuge test and upon comparison, a reasonable agreement was observed between the numerical simulation and experimental results. The numerical model was then used to investigate the effects of different parameters including pile connection fixity, batter, and stiffness of the pile on SIBM. The simulation results showed that the fixed connection greatly increases the bending moment compared to the pinned case. The difference in the maximum bending moment due to different pile batters can be approximated linearly. However, the results showed that changes in the maximum bending moment versus pile stiffness do not follow a linear pattern. Findings of this research can be used to validate or identify the need for possible adjustments in the current T-wall modelling and design methodologies.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124672466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-01-02DOI: 10.1080/19375247.2017.1309752
{"title":"DFI Journal Underwriters","authors":"","doi":"10.1080/19375247.2017.1309752","DOIUrl":"https://doi.org/10.1080/19375247.2017.1309752","url":null,"abstract":"","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133388414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-04DOI: 10.1080/19375247.2017.1288883
T. Siegel, A. Lucarelli
It is well-accepted within the foundation engineering community that piles in settling soil can be subject to negative skin friction (NSF). Typical causes of soil settlement include surface loads (e.g. new fill, structures), lowering of the water table, and earthquake- or liquefaction-induced compression. From examination of the results of long-term monitoring of piles, Fellenius [1988. Unified design of piles and pile groups. Geotechnical Instrumentation –- Transportation Research Record, 1169, pp.75–82] concluded that essentially all piles in soil develop NSF. There are important fundamental differences in the behaviour of piles with NSF compared to piles without NSF that affect the structural and geotechnical design. The purpose of this study is to introduce a theory to explain the development of NSF for all piles in soil. It is hypothesised that, consistent with the results of long-term pile monitoring, very small soil settlements are sufficient to mobilise the side resistance. Mechanisms causing settlement (common to all piles in soil) include installation effects and consolidation under the permanent (head) load. A numerical model of a hypothetical pile and soil system confirms that settlement from these mechanisms result in NSF consistent with the results of long-term monitoring.
{"title":"Theory and modelling of negative skin friction on a pile in soil","authors":"T. Siegel, A. Lucarelli","doi":"10.1080/19375247.2017.1288883","DOIUrl":"https://doi.org/10.1080/19375247.2017.1288883","url":null,"abstract":"It is well-accepted within the foundation engineering community that piles in settling soil can be subject to negative skin friction (NSF). Typical causes of soil settlement include surface loads (e.g. new fill, structures), lowering of the water table, and earthquake- or liquefaction-induced compression. From examination of the results of long-term monitoring of piles, Fellenius [1988. Unified design of piles and pile groups. Geotechnical Instrumentation –- Transportation Research Record, 1169, pp.75–82] concluded that essentially all piles in soil develop NSF. There are important fundamental differences in the behaviour of piles with NSF compared to piles without NSF that affect the structural and geotechnical design. The purpose of this study is to introduce a theory to explain the development of NSF for all piles in soil. It is hypothesised that, consistent with the results of long-term pile monitoring, very small soil settlements are sufficient to mobilise the side resistance. Mechanisms causing settlement (common to all piles in soil) include installation effects and consolidation under the permanent (head) load. A numerical model of a hypothetical pile and soil system confirms that settlement from these mechanisms result in NSF consistent with the results of long-term monitoring.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121915742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-04DOI: 10.1080/19375247.2017.1295195
Y. Bougataya, A. Stuedlein
In this study, resistance factors for the wave equation analysis of piles (WEAP) and a commonly used static analysis (SA) method are calibrated for use with piles driven in the Puget Sound Lowlands. Resistance factors are calibrated using a database of dynamic pile load test data with 95 piles monitored at the end-of-drive (EOD) condition and 94 piles monitored at the beginning-of-restrike (BOR) condition. Capacities are estimated using stress wave measurements collected with the pile driving analyzer (PDA) and interpreted using the CAse Pile Wave Analysis Program (CAPWAP) signal-matching procedure. The accuracy and uncertainty associated with the selected SA method was evaluated, along with WEAP bearing graph analyses for two alternative approaches for the estimate of per cent shaft resistance: (1) that computed from CAPWAP, and (2) that computed using the selected SA method. In general, the WEAP-based estimates of capacity were relatively accurate on average, with coefficients of variation ranging from 26 to 42%, whereas the selected SA method produced coefficient of variations as high as 85%. When compared to the AASHTO (2014, LRFD bridge design specifications. 7th edn. Washington, DC: AASHTO) recommended resistance factors that are based on a national database, the region-specific resistance factors based on WEAP at EOD increased by about 50% to 0.67 and 0.65 for the CAWAP and SA-based per cent shaft resistances, respectively. The resistance factors calibrated for the WEAP capacity estimates at the BOR condition were 0.53 and 0.46, lower than at EOD in part because of the transformation error associated with the use of dynamic loading tests for a long-term static capacity. Owing to its larger variability, the resistance factors calibrated for the selected SA method were significantly lower. The study described in this paper illustrates the benefit of using a high-quality, region-specific database for calibration of resistance factors.
{"title":"Region-specific calibration of resistance factors for use with static and wave equation analyses of driven piles","authors":"Y. Bougataya, A. Stuedlein","doi":"10.1080/19375247.2017.1295195","DOIUrl":"https://doi.org/10.1080/19375247.2017.1295195","url":null,"abstract":"In this study, resistance factors for the wave equation analysis of piles (WEAP) and a commonly used static analysis (SA) method are calibrated for use with piles driven in the Puget Sound Lowlands. Resistance factors are calibrated using a database of dynamic pile load test data with 95 piles monitored at the end-of-drive (EOD) condition and 94 piles monitored at the beginning-of-restrike (BOR) condition. Capacities are estimated using stress wave measurements collected with the pile driving analyzer (PDA) and interpreted using the CAse Pile Wave Analysis Program (CAPWAP) signal-matching procedure. The accuracy and uncertainty associated with the selected SA method was evaluated, along with WEAP bearing graph analyses for two alternative approaches for the estimate of per cent shaft resistance: (1) that computed from CAPWAP, and (2) that computed using the selected SA method. In general, the WEAP-based estimates of capacity were relatively accurate on average, with coefficients of variation ranging from 26 to 42%, whereas the selected SA method produced coefficient of variations as high as 85%. When compared to the AASHTO (2014, LRFD bridge design specifications. 7th edn. Washington, DC: AASHTO) recommended resistance factors that are based on a national database, the region-specific resistance factors based on WEAP at EOD increased by about 50% to 0.67 and 0.65 for the CAWAP and SA-based per cent shaft resistances, respectively. The resistance factors calibrated for the WEAP capacity estimates at the BOR condition were 0.53 and 0.46, lower than at EOD in part because of the transformation error associated with the use of dynamic loading tests for a long-term static capacity. Owing to its larger variability, the resistance factors calibrated for the selected SA method were significantly lower. The study described in this paper illustrates the benefit of using a high-quality, region-specific database for calibration of resistance factors.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132902799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-04DOI: 10.1080/19375247.2016.1299316
{"title":"DFI Journal Underwriters","authors":"","doi":"10.1080/19375247.2016.1299316","DOIUrl":"https://doi.org/10.1080/19375247.2016.1299316","url":null,"abstract":"","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123015520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-11-04DOI: 10.1080/19375247.2017.1286428
A. Fahmy, M. E. El Naggar
A novel piling system, spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate, is proposed in this study to support solar energy panels. The cyclic lateral performance of the pile is investigated herein. Seven piles were installed using mechanical torque and tested in sand: five SCDI tapered and two steel straight shafts. The cyclic lateral performance of the piles was evaluated and compared to the previously reported monotonic load test results. Effects of prior lateral loading on the piles performance were also assessed. Additionally, three-dimensional finite element simulation of the field tests was carried out to further understand the piles performance characteristics and to evaluate any possible system stiffness change. Straight and tapered shafted helical piles showed a generally satisfactory lateral cyclic performance. Degradation of the system stiffness was observed during testing. The application of prior lateral static tests also had a degrading effect on the cyclic lateral performance of the piles.
{"title":"Cyclic lateral performance of helical tapered piles in silty sand","authors":"A. Fahmy, M. E. El Naggar","doi":"10.1080/19375247.2017.1286428","DOIUrl":"https://doi.org/10.1080/19375247.2017.1286428","url":null,"abstract":"A novel piling system, spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate, is proposed in this study to support solar energy panels. The cyclic lateral performance of the pile is investigated herein. Seven piles were installed using mechanical torque and tested in sand: five SCDI tapered and two steel straight shafts. The cyclic lateral performance of the piles was evaluated and compared to the previously reported monotonic load test results. Effects of prior lateral loading on the piles performance were also assessed. Additionally, three-dimensional finite element simulation of the field tests was carried out to further understand the piles performance characteristics and to evaluate any possible system stiffness change. Straight and tapered shafted helical piles showed a generally satisfactory lateral cyclic performance. Degradation of the system stiffness was observed during testing. The application of prior lateral static tests also had a degrading effect on the cyclic lateral performance of the piles.","PeriodicalId":272645,"journal":{"name":"DFI Journal - The Journal of the Deep Foundations Institute","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127000202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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