Agenda 1 Overview of AASHTO LRFD 2 Culvert

Agenda 1. Overview of AASHTO LRFD 2. Culvert Design by LRFD 3. ETCulvert Overview 4. Interface Walk-thru 5. Common Design Questions 6. Advanced Topics 7. Questions 1

Starting a new problem Built-in problems n Start with either rebar or mesh n 2

Starting a new problem Initialize using a seed file n Create a library of problem types n 3

Open an Existing Problem Standard Windows open file dialog n Double click on ETCulvert data files n 4

Select Code and Agency Code selection will change some of the options available in the input windows n Agency selection sets some input automatically n 5

Select Program Operation n Typically start with Design Mode for new files 6

Mode and Selected Code are shown in the Status Bar 7

Input Dimensions of the Culvert Number of Cells (up to 4) n Clear span, clear height, lay length n 8

Identify Fill Depths to Check one fill depth or a range of fill depths n If range includes 1. 99’, this value will be inserted n 9

Range of Fill Depths Text report shows controlling fill depth n Different reinforcement locations may be controlled by different fill depths n 10

Wall and Slab Dimensions Some agencies may have minimum thicknesses for walls and slabs n Program will select minimum thickness if no agency selected n 11

Material Properties Most of the time you will probably only change the concrete strength n Good place for seed files, as the next item that changes the most are covers n 12

Bar Diameter Used in Design Mode for calculating d when reinforcement is not yet sized n Should reduce if using mesh n 13

Assign Loads Live Load – select/define the truck here n Can share truck files with others n 14

Defining Trucks Variable axle spacing and magnitude n Also define lane and tandem loads n 15

Defining Trucks Variable axle spacing and magnitude n Also define lane and tandem loads n 16

Defining Trucks n Don’t forget to specify the combination of truck loads and lane loads 17

Retrieving and Saving Trucks Retrieve a previously saved truck file n Or Save the current one n 18

Assign Loads Lane Load can be turned off here n When switching codes, trucks are NOT switched as well n 19

Dead Loads Can apply either distributed or concentrated dead loads n Loads are applied to a 1’ strip n 20

Lateral Soil Loads Program uses equivalent fluid pressure method n Soil weight is used for vertical loads n 21

Lateral Soil Loads (AREMA) n Here the weight of the soil is used for both vertical and horizontal loads 22

Load and Resistance Factors n Probably will not change these factors very often 23

Analysis Options Member thicknesses can be either variable or fixed in Design Mode n Not available during Analysis Mode n 24

Analysis Mode n After initial run in Design Mode, switch Analysis Mode to ‘tweak’ culvert design 25

Switching Reinforcement Types n Must be done in Design Mode 26

Permit Loads n Remember to change to Strength II load factors on Analysis Options page 27

Permit Loads n Also remember that only the operating is applicable 28

Shear Reinforcement Can add shear reinforcement in either Design or Analysis Mode n Will only calculate Vs in Analysis Mode n 29

Recent Changes to ETCulvert Added support for AREMA n Mesh can be any size (to one decimal point) n Changes to Text Report as requested by ACPA n Added support for pipe flexure equation n New Version Available (V 2. 50) n 30

Output Options Main View n Text Report n Graphs n 3 D Viewer n Results Grid n 31

Text Report Input Data n Reinforcement Schedule n Unfactored Moments n Serviceability Check n Critical Section Tables (includes ratings) n Factored Results n 32

Questions? 33

Agenda 1. Overview of AASHTO LRFD 2. Culvert Design by LRFD 3. ETCulvert Overview 4. Interface Walk-thru 5. Common Design Questions 6. Advanced Topics 7. Questions 34

Common Design Questions Skewed Culverts n How are # of Lanes Determined n Pinned/Roller Supports n Single Layer of Reinforcement n 35

Skewed Culverts: Case 1 n Only the Exterior Culvert is Skewed § Skew angle is < 15 degrees § Skew angle is > 15 degrees 36

Skewed Culverts: Case 1 n Only the Exterior Culvert is Skewed § Skew angle is < 15 degrees § Skew angle is > 15 degrees 37

Skewed Culverts: Case 1 a n Straight culverts, skewed roadway § Skew angle is < 15 degrees § Skew angle is > 15 degrees 38

Skewed Culverts: Case 1 a n Straight culverts, skewed roadway § Skew angle is < 15 degrees § Skew angle is > 15 degrees 39

Skewed Culverts: Case 2 n All Culverts are Skewed § Magnitude of Skew is not Important § Use the Skew dimension as the Clear Span 40

Common Design Questions Skewed Culverts n How are # of Lanes Determined n Pinned/Roller Supports n Single Layer of Reinforcement n 41

How are # of Lanes Determined? n Traffic is Parallel to Main Reinforcement § Less than 2 foot of fill depth § Greater than 2 foot of fill depth § 5 cases, with a maximum of 4 lanes § 2 lane case is checked twice 42

How are # of Lanes Determined? n Traffic is Parallel to Main Reinforcement § Less than 2 foot of fill depth § Greater than 2 foot of fill depth § 5 cases, with a maximum of 4 lanes § 2 lane case is checked twice 43

How are # of Lanes Determined? n Traffic is Perpendicular § Code gives no guidance here § 10 foot lanes are used, rounded up § May be overly conservative § Can limit maximum number of lanes 44

Number of Lanes Primarily used for perpendicular traffic n May be overly conservative in number of lanes selected n 45

Common Design Questions Skewed Culverts n How are # of Lanes Determined n Pinned/Roller Supports n Single Layer of Reinforcement n 46

Pinned/Roller Supports n 3 -Sided Culverts § Default Support Conditions 47

Pinned/Roller Supports n 3 -Sided Culverts § Alternate Support Conditions If Span/Depth Ratio > 4 48

Common Design Questions Skewed Culverts n How are # of Lanes Determined n Pinned/Roller Supports n Single Layer of Reinforcement n 49

Single Layer of Reinforcement Cover Dimensions n Main Reinforcement n Temperature and Shrinkage Steel for Walls n Distribution Steel + T & S Steel for Top and Bottom Slabs n Check that Main Reinforcement satisfies T & S steel n 50

Cover Dimensions Set Cover Dimensions such that Layers line up n Coordinate with Bar Diameter n 51

Main Reinforcement A 1, A 2, A 100, A 200 and B 2 Bars only n Program assumes singly reinforced n 52

Temperature and Shrinkage Steel for Walls Can use the C 1 bars in bar schedule n May be better to use calculated required n 53

Distribution Steel + C 1 Bars for Top and Bottom Slabs Need greater of Distribution Steel (C 100 and C 200) + C 1 Bars or 2 * C 1 Bars n May be better to check required column n 54

Final Check n Check that Main Reinforcement satisfies Temperature and Shrinkage requirements 55

Questions? 56

Agenda 1. Overview of AASHTO LRFD 2. Culvert Design by LRFD 3. ETCulvert Overview 4. Interface Walk-thru 5. Common Design Questions 6. Advanced Topics 7. Questions 57

Advanced Topics Loads n Load and Resistance Factors n Analysis Options n Longitudinal Steel n 58

Loads – Traffic Direction Traffic can be applied either parallel or perpendicular to main reinforcement n Most of the time it will be parallel n 59

Loads – Number of Lanes Important for perpendicular traffic n Program looks for worst case, but in some situations cannot be overridden n 60

Loads – Track Width (AREMA) Accessible due to uncertainty n Truck gage width is not used for AREMA calculations n 61

Load and Resistance Factors for LRFD P-M Diagram n Phi for moment is not used unless axial load is ignored n 62

Ignore Axial Thrust P-M diagram will not be used n Program assumes pure flexure n 63

Use Pipe Equation Use pipe equation from LRFD n Mimics BOXCAR (1 of 3) n Multiplier available for Nu n 64

Skew Effects Skew effects must be accounted for, but LRFD does not say how n When skew is greater than 15 degrees, will set traffic to perpendicular n 65

Combine Axles that Overlap LRFD language demands that axles be combined when they overlap n We believe that this may be unconservative for short spans n 66

Combine Axles that Overlap n Live Load distribution when not selected 67

Combine Axles that Overlap n Live Load distribution when selected 68

Always Distribute Wheel Loads When fill depth is < 2’, will still treat wheel loads as distributed, not point n Mimics BOXCAR (2 of 3) n 69

Haunches in Structural Model Re-distributes slab moment from positive region to negative region n Mimics BOXCAR (3 of 3) n 70

Bottom Node on Roller (3 -sided) Suggested when span to depth ratio is greater than 4 n Has effect of converting top slab to simple span n 71

Consider Haunches in Location of Critical Section Used to locate the critical sections for flexure and shear n 3 possible locations for flexure n 2 possible locations for shear n 72

Illustration of dv vs d 73

Haunches not considered: 74

Haunches considered: 75

Extended beyond haunches: 76

Use Maximum Moment with Maximum Shear For use with those equations for Vc that use an interaction between V and M n Forces the program to use the moment at the flexural critical section n 77

Always Check Iterative Beta Forces program to always check general case (Appendix) for shear resistance n Will use largest value of Vc found n 78

Upper Limit on As For use with Design Mode n Iterative beta method can produce very large member thicknesses n 79

Always Include Distribution Both Design and Analysis Modes n Fill depths greater than 2’ n 80

Longitudinal Steel For non-distribution longitudinal steel n Follow specification recommendations n Only use % of cross section area n Only use temperature/shrinkage n 81

Future Plans for ETCulvert Include support for more sophisticated structural analysis options n Add soil-structure interaction n Add support for Canadian Highway Bridge Code n Allow access to reinforcement size/spacing pair library n Add wingwalls, footings, appurtenances n Additional user requests and agencies n Support for AASHTOWare 82 n

Questions? 83

Agenda 1. Overview of AASHTO LRFD 2. Culvert Design by LRFD 3. ETCulvert Overview 4. Interface Walk-thru 5. Common Design Questions 6. Advanced Topics 7. Questions 84