Practices for Local Calibration of LRFD Geotechnical Resistance Factors (2023)

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54 A P P E N D I X A Survey Questionnaire

Survey Questionnaire 55   Dear State DOT Engineer, TRB is preparing a synthesis on practices for agency-specific calibration of LRFD geotechnical resistance factors. This is being done for NCHRP, under the sponsorship of AASHTO, in cooperation with FHWA. The AASHTO LRFD specifications for geotechnical design provide state DOTs the opportunity to develop agency-specific resistance factors to account for unique geology, design practice, and construction methods. Many of the AASHTO LRFD resistance factors were developed based on load tests performed across the country, with variable conditions and practices. While many DOTs use these resistance factors, others have developed agency-specific methods or resistance factors, often with considerable improvement in design efficiency. The objective of this project is to document the extent to which state DOTs have developed agency-specific resistance factors, the methods used for development, which factors have been calibrated, and how agency-specific factors have been used. This survey of state DOTs is a primary means of gathering information for the synthesis. We would greatly appreciate a response from your agency. If you are not the appropriate person at your DOT to complete this questionnaire, please forward it to the correct person. Note that DOT survey responses will be shown in the published synthesis report. However, the identity of survey respondents will remain anonymous. Please use the link below to access the survey. If you need to leave the survey at any point, the link below will return you to the page where you left off. <link> Please complete and submit the survey by February 11. We estimate the survey will take approximately 30 minutes to complete, although for some agencies less time will be required. If you have questions, please contact the co-investigator, Andy Boeckmann. Any supporting materials or additional documents that might be useful for this study would be much appreciated and can be sent directly to Andy by email. If you would like to review the questions prior to entering the survey, a PDF of the survey can be downloaded from the link at the very bottom of this message. Thank you for participating in the survey! Andy Boeckmann, Ph.D., P.E. Senior Engineer Dan Brown and Associates Survey PDF: https://danbrownandassociates.egnyte.com/fl/h6ZWJVd9mn

56 Practices for Local Calibration of LRFD Geotechnical Resistance Factors SURVEY INSTRUCTIONS 1. To view and print the entire survey, please use the link from the web address below, or contact Andy Boeckmann. https://danbrownandassociates.egnyte.com/fl/h6ZWJVd9mn 2. Your responses are automatically saved upon advancing from one page of the survey to the next. Please use the link included in the initial email regarding this survey to return to the page where you left off. 3. Although only one response per agency is allowed, it may be helpful to share responsibility for the survey completion among colleagues. To pass a partially completed survey response to a colleague, please forward the initial email and instruct your colleague to use the link included in that message. The initial link will always advance a user to the furthest point reached in the survey. Note that only one person may work on the survey at a time; the survey response should only be active on one computer at a time. 4. To submit the survey, click on "Submit" on the last page. SURVEY USE OF “AASHTO RESISTANCE FACTORS” Throughout this survey, the term “AASHTO resistance factors” is used to refer to the resistance factors specified in the current version of the AASHTO LRFD Bridge Design Specifications. CONTACT INFORMATION Contact information will be collected for the agency’s point of contact for the survey using the survey software.

Survey Questionnaire 57   SURVEY (1) Does your agency use or require use of any geotechnical design method or resistance factors that differ from those specified in the AASHTO LRFD Bridge Design Specifications? o No, all of our design methods and resistance factors align with those specified in the AASHTO specifications. o Yes, our agency requires use of design methods or resistance factors that differ from those specified in the AASHTO specifications. Question (2) will be presented to respondents who indicate in Question (1) that their agency uses all of the AASHTO resistance factors. After responding to Question (2), these respondents will be presented with Question (18) (skipping the questions between). (2) Please indicate the reasons your agency exclusively follows the AASHTO LRFD Bridge Design Specifications for geotechnical design. Please select all that apply. □ AASHTO design methods and associated resistance factors are sufficient for our agency design needs. □ The cost or time associated with developing agency-specific design methods or resistance factors is considered to be too great. □ We do not have the expertise to develop agency-specific design methods or resistance factors. □ The benefits of developing agency-specific design methods or resistance factors are uncertain or unclear. □ Agency leadership has not supported development of agency-specific design methods or resistance factors. □ Our agency is hesitant to stray from AASHTO specifications. □ Other, please specify: _____________________________ All remaining questions will be presented to respondents who indicate in Question (1) that their agency does use agency-specific design methods or resistance factors. (3) What benefits has your agency experienced from using agency-specific design methods or resistance factors? Please select all that apply. □ Improved site characterization practices □ Improved foundation type selection □ Improved design practices □ Improved construction practices □ Site characterization cost savings □ Project cost savings □ Other, please specify: _____________________________ o None of the above o I don’t know.

58 Practices for Local Calibration of LRFD Geotechnical Resistance Factors (4) Have the benefits indicated in the previous question been quantified? o Yes If yes: Please explain: _____________________________ o No o I don’t know. (5) What challenges has your agency encountered during development of agency-specific design methods or resistance factors? Please select all that apply. □ High cost associated with development □ No clear funding source □ Insufficient in-house expertise with agency-specific calibration □ Difficulty convincing agency leadership of benefits □ Reluctance to stray from AASHTO specifications □ Other, please specify: _____________________________ (6) For which geotechnical elements has your agency developed agency-specific design methods or resistance factors? Please select all that apply. □ Spread footings □ Driven piles □ Drilled shafts □ Micropiles □ Continuous flight auger (CFA) piles (aka auger cast piles) □ Cantilever retaining walls □ MSE walls □ Soil nail walls

Survey Questionnaire 59   For each of the design elements selected in Question (6), respondents will be asked to answer Questions (7) through (17). (7) What motivated development of the agency-specific design method or resistance factors? Please select all that apply. □ No suitable method in current AASHTO specifications for common ground conditions □ Use of unique site investigation methods (e.g., Texas cone penetrometer, torque SPT, etc.) □ Considerably different design practices □ Considerably different construction practices □ Use of foundation elements not considered in current AASHTO specifications (e.g., continuous-flight auger piles) <Only if “Other” is selected for Q6.> □ Desire for enhanced design efficiency offered by agency-specific calibration □ Design requirements not addressed in current AASHTO specifications □ Other, please specify: _____________________________ o None of the above o I don’t know. (8) Were agency-specific design methods developed (i.e., an agency-specific method for predicting nominal resistance)? o Yes o No, we use AASHTO for nominal resistance but with an agency-specific resistance factor. o I don’t know. (9) For which limit states do the agency-specific design method or resistance factors apply? Please select all that apply. If survey software permits, responses that appear below will depend on the geotechnical element, as noted. If not, a more generic list will be developed. Spread footing: □ Bearing resistance □ Sliding □ Service limit state (settlement) □ Other, please specify: _____________________________

60 Practices for Local Calibration of LRFD Geotechnical Resistance Factors Driven piles: □ Axial resistance from static methods for strength limit state □ Axial resistance from pile driving formula (for strength limit state) □ Axial resistance from dynamic testing (i.e., CAPWAP) □ Axial resistance based on site-specific load tests □ Downdrag design procedures and resistance factors □ Axial resistance for service limit state □ Lateral resistance for strength limit state □ Lateral resistance for service limit state □ Axial resistance for extreme event limit state □ Lateral resistance for extreme event limit state □ Other, please specify: _____________________________ Drilled shafts: □ Side resistance for strength limit state □ Tip resistance for strength limit state □ Lateral resistance for strength limit state □ Axial resistance for service limit state □ Lateral resistance for service limit state □ Axial resistance for extreme event limit state □ Lateral resistance for extreme event limit state □ Other, please specify: _____________________________ Micropiles: □ Bond strength for strength limit state □ Lateral resistance for strength limit state □ Bond strength for service limit state □ Lateral resistance for service limit state □ Bond strength for extreme event limit state □ Lateral resistance for extreme event limit state □ Other, please specify: _____________________________ Continuous flight auger (CFA) piles: □ Side resistance for strength limit state □ Tip resistance for strength limit state □ Lateral resistance for strength limit state □ Axial resistance for service limit state □ Lateral resistance for service limit state □ Axial resistance for extreme event limit state □ Lateral resistance for extreme event limit state □ Other, please specify: _____________________________

Survey Questionnaire 61   Cantilever walls: □ Sliding resistance □ Overturning resistance □ Settlement □ Global stability □ Compound stability □ Other, please specify: _____________________________ MSE walls: □ Sliding resistance □ Overturning resistance □ Settlement □ Global stability □ Compound stability □ Soil reinforcement rupture □ Soil reinforcement pullout □ Facing-reinforcement connection rupture □ Other, please specify: _____________________________ Soil nail walls: □ Pullout resistance □ Sliding resistance □ Overturning resistance □ Settlement □ Global stability □ Compound stability □ Temporary stability (i.e. between lifts) □ Other, please specify: _____________________________ (10) For which ground conditions do the agency-specific design method or resistance factors apply? Please select all that apply. Please note this question is limited to ground condition constraints only. A separate question will ask about other constraints (e.g., construction practices, structure types, etc.). □ Cohesive soils □ Cohesionless soils □ Weak rock (e.g., shale, sandstone, intermediate geomaterial) □ Hard rock □ Other, please specify: _____________________________

62 Practices for Local Calibration of LRFD Geotechnical Resistance Factors (11) In addition to ground conditions, agency-specific design methods or resistance factors are often applicable only in certain situations. Is use of the design method or resistance factors constrained to specific applications? Please select all that apply. □ Agency-specific construction practices If yes: Please specify: _____________________________ □ Agency-specific foundation testing or control practices If yes: Please specify: _____________________________ □ Specific type of foundation or wall (e.g., concrete piles, CIP shell piles, etc.) If yes: Please specify: _____________________________ □ Structure type or class If yes: Please specify: _____________________________ □ Project magnitude If yes: Please specify: _____________________________ □ Other, please specify: _____________________________ o No restrictions o I don’t know. (12) How were the agency-specific resistance factors developed? Please select all that apply. □ Fitting to historical allowable stress design (ASD) factors of safety. □ Probabilistic calibration (i.e., using statistics). □ Expert elicitation □ Other, please specify: _____________________________ o Not applicable: We use AASHTO resistance factors with our agency-specific design method. o I don’t know. (13) What type of information was used to develop the agency-specific design method or resistance factors? Please select all that apply. □ Project information (e.g., site-specific load tests) □ Dedicated, agency-funded research □ Published research by others (outside the agency) □ Other type of data, please specify: _____________________________ o Not applicable, please explain: _____________________________ o I don’t know. (14) Who developed the agency-specific design method or resistance factors? Please select all that apply. □ Our agency, i.e., by in-house personnel □ An academic partner □ A consulting engineer □ Other, please specify: ______________________ o I don’t know.

Survey Questionnaire 63   (15) What funding mechanism(s) were used to support development of the agency-specific design method or resistance factors? Please select all that apply. □ Dedicated research funding (e.g., State Planning and Research (SP&R) funds) □ Pooled fund study □ State project funding □ Other, please specify: _____________________________ o I don’t know. (16) What were approximate agency costs associated with development of the agency-specific design methods and/or resistance factors? o 0 to $50,000 o $50,001 to $150,000 o $150,001 to $250,000 o $250,001 to $500,000 o $500,001 to $1,000,000 o >$1,000,000 o I don’t know. (17) Is the agency-specific design method and/or its development documented in any agency guidance, publications, specifications, or other means? o Yes o No o I don’t know. If yes: Please provide a link(s) to an online version of the document(s), or upload the document(s) as an attachment below. □ Link to documents (Insert text box) □ Upload documents (Insert upload button) □ Please contact us for more information (Insert text box) □ Documents are not available for sharing

64 Practices for Local Calibration of LRFD Geotechnical Resistance Factors The remaining questions will be asked to all respondents, including those who indicate their agency uses all of the AASHTO resistance factors. (18) For which design conditions would your agency most benefit from having agency-specific beneficial, please select the three that would be most beneficial). o None; our agency is satisfied with AASHTO resistance factors. (If respondent selects this, he or she will not be able to select any other responses.) □ Spread footing bearing resistance □ Spread footing sliding □ Spread footing service limit state □ Driven pile static resistance □ Driven pile resistance based on pile driving formula □ Driven pile resistance based on dynamic testing (i.e., CAPWAP) □ Driven pile resistance based on site-specific static load tests □ Driven pile lateral resistance □ Driven pile group axial resistance □ Driven pile group lateral resistance □ Driven pile service limit state □ Drilled shaft side resistance (from empirical methods) □ Drilled shaft tip resistance (from empirical methods) □ Drilled shaft resistance based on site-specific load tests □ Drilled shaft lateral resistance □ Drilled shaft group axial resistance □ Drilled shaft group lateral resistance □ Drilled shaft service limit state □ Micropile bond strength □ Reuse of foundations □ Other, please specify: _____________________________ (19) Does your agency maintain a database of geotechnical information (e.g., subsurface investigation results, foundation load tests, performance monitoring results, etc.)? o Yes o No o I don’t know. Questions (20) and (21) will be asked of participants who select “Yes” in response to Question (19). (20) What types of information are included in the database? Please select all that apply. □ Subsurface investigation results (e.g., boring information, lab tests, CPT results, etc.) □ Foundation load tests □ Performance monitoring results □ Other, please specify: _____________________________ resistance factors? Please select up to three responses (i.e., if more than three would be

Survey Questionnaire 65   (21) Is the database publicly available? o Yes o No o I don’t know. Before submitting, respondents will be asked to confirm they are ready to submit. END OF SURVEY Thank you for completing the survey. Your responses are important, and your feedback is welcome. If you have questions or comments, please contact the co-investigator: Andrew Boeckmann, Ph.D., P.E.