DESIGN GUIDE for midas Civil AASHTO LRFD Prestressed Concrete Girder Design Steel Composite Girder Design Steel Composite Bridge Load Rating dŚĞŽďũĞĐƟǀĞŽĨƚŚŝƐĚĞƐŝŐŶŐƵŝĚĞŝƐƚŽŽƵƚůŝŶĞƚŚĞĚĞƐŝŐŶ ĂůŐŽƌŝƚŚŵƐǁŚŝĐŚĂƌĞĂƉƉůŝĞĚŝŶŵŝĚĂƐŝǀŝůĮŶŝƚĞĞůĞŵĞŶƚ analysis and design system The guide aims to provide ƐƵĸĐŝĞŶƚŝŶĨŽƌŵĂƟŽŶĨŽƌƚŚĞƵƐĞƌƚŽƵŶĚĞƌƐƚĂŶĚƚŚĞ ƐĐŽƉĞ͕ůŝŵŝƚĂƟŽŶƐĂŶĚĨŽƌŵƵůĂƐĂƉƉůŝĞĚŝŶƚŚĞĚĞƐŝŐŶ features and to provide relevant references to the clauses in the Design standards The design guide covers prestressed concrete girder design, steel composite girder design and steel composite ŐŝƌĚĞƌďƌŝĚŐĞƌĂƟŶŐĂƐƉĞƌ^,dK>Z&͘ It is recommended that you read this guide and review corresponding tutorials, which are found on our web site, ŚƩƉ͗ͬͬǁǁǁ͘DŝĚĂƐhƐĞƌ͘ĐŽŵ͕ďĞĨŽƌĞĚĞƐŝŐŶŝŶŐ͘ĚĚŝƟŽŶĂů ŝŶĨŽƌŵĂƟŽŶĐĂŶďĞĨŽƵŶĚŝŶƚŚĞŽŶůŝŶĞŚĞůƉĂǀĂŝůĂďůĞŝŶ the program’s main menu DISCLAIMER Developers and distributors assume no responsibility for the use of MIDAS Family Program (midas Civil, midas FEA, midas FX+, midas Gen, midas Drawing, midas SDS, midas 'd^͕^ŽŝůtŽƌŬƐ͕ŵŝĚĂƐE&y͖ŚĞƌĞŝŶĂŌĞƌƌĞĨĞƌƌĞĚƚŽĂƐ “MIDAS package”) or for the accuracy or validity of any results obtained from the MIDAS package Developers and distributors shall not be liable for loss of ƉƌŽĮƚ͕ůŽƐƐŽĨďƵƐŝŶĞƐƐ͕ŽƌĮŶĂŶĐŝĂůůŽƐƐǁŚŝĐŚŵĂLJďĞ caused directly or indirectly by the MIDAS package, when used for any purpose or use, due to any defect or ĚĞĮĐŝĞŶĐLJƚŚĞƌĞŝŶ͘ĐĐŽƌĚŝŶŐůLJ͕ƚŚĞƵƐĞƌŝƐĞŶĐŽƵƌĂŐĞĚƚŽ fully understand the bases of the program and become familiar with the users manuals The user shall also independently verify the results produced by the program Foreword dŚĞŽďũĞĐƟǀĞŽĨƚŚŝƐĚĞƐŝŐŶŐƵŝĚĞŝƐƚŽŽƵƚůŝŶĞƚŚĞĚĞƐŝŐŶĂůŐŽƌŝƚŚŵƐ ǁŚŝĐŚĂƌĞĂƉƉůŝĞĚŝŶŵŝĚĂƐŝǀŝůĮŶŝƚĞĞůĞŵĞŶƚĂŶĂůLJƐŝƐĂŶĚĚĞƐŝŐŶ ƐLJƐƚĞŵ͘dŚĞŐƵŝĚĞĂŝŵƐƚŽƉƌŽǀŝĚĞƐƵĸĐŝĞŶƚŝŶĨŽƌŵĂƟŽŶĨŽƌƚŚĞƵƐĞƌƚŽ ƵŶĚĞƌƐƚĂŶĚƚŚĞƐĐŽƉĞ͕ůŝŵŝƚĂƟŽŶƐĂŶĚĨŽƌŵƵůĂƐĂƉƉůŝĞĚŝŶƚŚĞĚĞƐŝŐŶ features and to provide relevant references to the clauses in the Design standards The design guide covers prestressed concrete girder design, steel ĐŽŵƉŽƐŝƚĞŐŝƌĚĞƌĚĞƐŝŐŶĂŶĚƐƚĞĞůĐŽŵƉŽƐŝƚĞŐŝƌĚĞƌďƌŝĚŐĞƌĂƟŶŐĂƐƉĞƌ ^,dK>Z&͘ It is recommended that you read this guide and review corresponding ƚƵƚŽƌŝĂůƐ͕ǁŚŝĐŚĂƌĞĨŽƵŶĚŽŶŽƵƌǁĞďƐŝƚĞ͕ŚƩƉ͗ͬͬǁǁǁ͘DŝĚĂƐhƐĞƌ͘ĐŽŵ͕ ďĞĨŽƌĞĚĞƐŝŐŶŝŶŐ͘ĚĚŝƟŽŶĂůŝŶĨŽƌŵĂƟŽŶĐĂŶďĞĨŽƵŶĚŝŶƚŚĞŽŶůŝŶĞ help available in the program’s main menu Organization dŚŝƐŐƵŝĚĞŝƐĚĞƐŝŐŶĞĚƚŽŚĞůƉLJŽƵƋƵŝĐŬůLJďĞĐŽŵĞƉƌŽĚƵĐƟǀĞǁŝƚŚ ƚŚĞĚĞƐŝŐŶŽƉƟŽŶƐŽĨ^,dK>Z&͘ ŚĂƉƚĞƌϭƉƌŽǀŝĚĞƐĚĞƚĂŝůĞĚĚĞƐĐƌŝƉƟŽŶƐŽĨƚŚĞĚĞƐŝŐŶƉĂƌĂŵĞƚĞƌƐ͕ h>^ͬ^>^ĐŚĞĐŬƐ͕ĚĞƐŝŐŶŽƵƚƉƵƚƐƵƐĞĚĨŽƌƉƌĞƐƚƌĞƐƐĞĚĐŽŶĐƌĞƚĞ ŐŝƌĚĞƌĚĞƐŝŐŶƚŽ^,dK>Z&͘ ŚĂƉƚĞƌϮƉƌŽǀŝĚĞƐĚĞƚĂŝůĞĚĚĞƐĐƌŝƉƟŽŶƐŽĨƚŚĞĚĞƐŝŐŶƉĂƌĂŵĞƚĞƌƐ͕ h>^ͬ^>^ĐŚĞĐŬƐ͕ĚĞƐŝŐŶŽƵƚƉƵƚƐƵƐĞĚĨŽƌƐƚĞĞůĐŽŵƉŽƐŝƚĞŐŝƌĚĞƌ ĚĞƐŝŐŶƚŽ^,dK>Z&͘ ŚĂƉƚĞƌϯƉƌŽǀŝĚĞƐĚĞƚĂŝůĞĚĚĞƐĐƌŝƉƟŽŶƐŽĨƚŚĞĚĞƐŝŐŶƉĂƌĂŵĞƚĞƌƐ͕ h>^ͬ^>^ĐŚĞĐŬƐ͕ĚĞƐŝŐŶŽƵƚƉƵƚƐƵƐĞĚĨŽƌƐƚĞĞůĐŽŵƉŽƐŝƚĞďƌŝĚŐĞ ůŽĂĚƌĂƟŶŐƚŽ^,dK>Z&Z͘ Contents Chapter Prestressed Concrete Girder Design ;^,dK>Z&Ϳ 01 Strength Limit States Flexural resistance 03 Shear resistance 16 Torsion resistance 28 Serviceability Limit States ϭ͘^ƚƌĞƐƐĨŽƌĐƌŽƐƐƐĞĐƟŽŶĂƚĂĐŽŶƐƚƌƵĐƟŽŶƐƚĂŐĞ 34 Ϯ͘^ƚƌĞƐƐĨŽƌĐƌŽƐƐƐĞĐƟŽŶĂƚƐĞƌǀŝĐĞůŽĂĚƐ 40 Tensile stress for Prestressing tendons 44 ϰ͘WƌŝŶĐŝƉĂůƐƚƌĞƐƐĂƚĂĐŽŶƐƚƌƵĐƟŽŶƐƚĂŐĞ 47 Principal stress at service loads 49 Principal stress at service loads 51 Check crack 52 ŚĂƉƚĞƌϮ͘ Steel Composite Girder Design ;^,dK>Z&Ϳ 55 /ŶƚƌŽĚƵĐƟŽŶ ϭ͘^,dK>Z&ϬϳĂŶĚϭϮ^ƚĞĞůŽŵƉŽƐŝƚĞ 57 Ϯ͘ŽŶƐŝĚĞƌĂƟŽŶƐ^ƚĞĞůŽŵƉŽƐŝƚĞĞƐŝŐŶ 59 ϯ͘ĂůĐƵůĂƟŽŶŽĨWůĂƐƟĐDŽŵĞŶƚĂŶĚzŝĞůĚDŽŵĞŶƚ 59 Modeling and Design Variables Modeling Design Variables 67 ƉƉůŝĐĂƟŽŶŽĨ^,dK>Z&ϭϮ ϭ͘/'ŝƌĚĞƌ^ĞĐƟŽŶ 87 Ϯ͘ŽdžͬdƵď'ŝƌĚĞƌ^ĞĐƟŽŶ 111 Shear Connector 127 ϰ͘^ƟīĞŶĞƌ 131 ϱ͘ŝīĞƌĞŶĐĞĞƚǁĞĞŶ^,dKͲ>Z&ϰƚŚ(2007) and 6th(2012) 135 ^ƚĞĞůŽŵƉŽƐŝƚĞĞƐŝŐŶZĞƐƵůƚ ϭ͘^ƚƌĞŶŐƚŚ>ŝŵŝƚ^ƚĂƚĞZĞƐƵůƚ 138 Ϯ͘^ĞƌǀŝĐĞ>ŝŵŝƚ^ƚĂƚĞZĞƐƵůƚ 141 ϯ͘ŽŶƐƚƌƵĐƟďŝůŝƚLJZĞƐƵůƚ 142 ϰ͘&ĂƟŐƵĞ>ŝŵŝƚ^ƚĂƚĞZĞƐƵůƚ 145 ϱ͘^ŚĞĂƌŽŶŶĞĐƚŽƌZĞƐƵůƚ 146 ϲ͘^ƟīĞŶĞƌZĞƐƵůƚ 147 Span Checking 148 Total Checking 149 Chapter ^ƚĞĞůŽŵƉŽƐŝƚĞƌŝĚŐĞ>ŽĂĚZĂƟŶŐ ;^,dK>Z&Ϳ 151 /ŶƚƌŽĚƵĐƟŽŶ ϭ͘^,dK>Z&ZϮϬϭϭƌŝĚŐĞ>ŽĂĚZĂƟŶŐ 153 Ϯ͘>ŽĂĚZĂƟŶŐ>ĞǀĞůƐ 155 ϯ͘WƌŽĐĞƐƐŽĨ>ŽĂĚZĂƟŶŐ 157 Modeling and Design Variables Modeling Design Variables 158 ƉƉůŝĐĂƟŽŶŽĨ^,dK>Z&Zϭϭ ϭ͘ZĂƟŶŐ&ĂĐƚŽƌĂůĐƵůĂƟŽŶ 171 Ϯ͘^ƚƌĞŶŐƚŚ>ŝŵŝƚ^ƚĂƚĞ 178 ϯ͘^ĞƌǀŝĐĞ>ŝŵŝƚ^ƚĂƚĞ 180 ϰ͘&ĂƟŐƵĞ>ŝŵŝƚ^ƚĂƚĞ 181 ƌŝĚŐĞ>ŽĂĚZĂƟŶŐZĞƐƵůƚ ϭ͘ZĞƐƵůƚdĂďůĞƐ 186 Ϯ͘ZĂƟŶŐĞƚĂŝůdĂďůĞ 191 ϯ͘>ŽĂĚZĂƟŶŐZĞƉŽƌƚ 194 Chapter Prestressed Concrete Girder Design AASHTO LRFD 7th (2014) Chapter Prestressed Concrete Girder Design ;^,dK>Z&ϭϰͿ Prestressed concrete box girders and composite girders need to be designed to ƐĂƟƐĨLJƚŚĞĨŽůůŽǁŝŶŐůŝŵŝƚƐƚĂƚĞƐ͘ hůƟŵĂƚĞ>ŝŵŝƚ^ƚĂƚĞƐ &ůĞdžƵƌĂůZĞƐŝƐƚĂŶĐĞ ^ŚĞĂƌZĞƐŝƐƚĂŶĐĞ dŽƌƐŝŽŶZĞƐŝƐƚĂŶĐĞ Serviceability Limit States ^ƚƌĞƐƐĨŽƌĐƌŽƐƐƐĞĐƟŽŶĂƚĂĐŽŶƐƚƌƵĐƟŽŶƐƚĂŐĞ ^ƚƌĞƐƐĨŽƌĐƌŽƐƐƐĞĐƟŽŶĂƚƐĞƌǀŝĐĞůŽĂĚƐ Tensile stress for Prestressing tendons WƌŝŶĐŝƉĂůƐƚƌĞƐƐĂƚĂĐŽŶƐƚƌƵĐƟŽŶƐƚĂŐĞ Principal stress at service loads Check crack Chapter Prestressed Concrete Girder Design:AASHTO-LRFD 7th (2014) Strength Limit States Flexural resistance The factored flexural resistance shall satisfy the following condition, Mu ≤ΦMn Where, Mu : Factored moment at the section due to strength load combination ΦMn : Factored flexural resistance 1.1 Resistance Factor AASHTO LRFD14 (5.5.4.2.1) Resistance factor Φ shall be taken as follow [Fig.1 1] Resistance Factor I 0.75 I 0.583  0.25 I 1.0 if H t d 0.002 dt c if 0.002  H t  0.005 (1.1) if H t t 0.005 Where, dt : Distance from extreme compression fiber to the centroid of the extreme tension steel element c : Distance from the extreme compression fiber to the neutral axis εt : Net tensile Strain In midas Civil, εt is applied as strain of a reinforcement which is entered at the extreme tensile fiber Chapter Prestressed Concrete Girder Design - AASHTO LRFD 2014 Input reinforcements to be used in the calculation of resistance in the dialog box below ೛ Model>Properties>Section Manager>Reinforcements Rebar coordinate at the section Entered rebar data [Fig.1 2] Input Longitudinal reinforcement Once reinforcement is entered at the PSC section, the rebar which is placed at the closest position to the extreme compression fiber will be used to calculate the strain In short, the rebar at the bottom most is used under the sagging moment And the rebar at the top most is used under the hogging moment Input tendon profile to be used in PSC design in the dialog box below ೛ Load>Temp./Prestress>Section Manager >Tendon Profile Tendon position which is placed at the closest position to the extreme tensile fiber will be used to calculate the strain     [Fig.1.3] Tendon Profile         Design Guide for midas Civil  Load Rating Levels The LRFR methodology consists of three distinct levels of evaluation: (1) Design load rating (2) Legal load rating (3) Permit load rating The result of each evaluation serve specific purpose and also inform the need for further evaluations The important factors of each load rating level are summarized as shown below [Fig.3.1] Load Rating Levels Each of these three levels of rating are discussed in detail in immediately following sections 2.1 Design Load Rating Design load rating is a first level assessment of bridges It is a measure of the performance of existing bridge to current LRFD bridge design standards (1) Live Load At Design load rating level, the HL-93 live-load model of the LRFD is applied, using dimensions and properties of the bridge in its present as inspected condition (2) Limit States Under this check, bridges are screened for the strength limit state at the LRFD design level of reliability Evaluation at a second lower evaluation level of reliability is also an option The rating also considers all applicable LRFD serviceability limit states (3) purpose Design load rating can serve as a screening process to identify bridges that should be load rated for legal loads Bridges the pass the design load check (RF൒1) at the Inventory level will have satisfactory load rating for all legal loads that fall within the LRFD exclusion limits (4) Level of Design Load Rating There are two levels of the Design Load Rating: 1) Inventory Rating level The Inventory rating level generally corresponds to the rating at the design level of reliability for new bridges in the AASHTO LRFD Bridge Design Specifications, but reflects the existing bridge and material conditions with regard to deterioration and loss of section Load ratings based on the Inventory level allow compressions with the capacity for new structures and, therefore, result in a live load, which can safely utilize an existing Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 155  structure for an indefinite period of time 2) Operation Rating level Load rating based of the Operation rating level generally describe the maximum permissible live load to which the structure may be subjected Generally corresponds to the rating at the Operating level may shorten the life of the bridge 2.2 Legal Load Rating This second level rating provides a single safe load capacity (for a given truck configuration) applicable to AASHTO and State legal loads The Previous distinction of Operating and Inventory level ratings is no longer maintained when load rating for legal loads Legal load rating provides a level of reliability, corresponding to the operating level reliability for redundant bridges in good condition (1) Live Load Live load is categorized into the two types according to AASHTO LRFR 2011 as: 1) AASHTO Legal loads, as specified in Article 6A.4.4.2.1a 2) The Notional Rating Load as specified in Article 6A.4.4.2.1b or State legal loads (2) Limit States Strength is the primary limit state for load rating; service limit states are selectively applied (3) purpose Bridges that not have sufficient capacity under the design-load rating shall be load rated for legal loads to establish the need for load posting or strengthening 2.3 Permit Load Rating This third level of rating should only be applied to bridges having sufficient capacity for legal loads In other words, Permit load rating should be used only if the bridge has a rating factor greater than 1.0 when evaluated for AASHTO legal loads (1) Live Load The actual permit vehicle’s gross vehicle weight and axle configuration will be the live load used in the permit-load evaluation The MBE(Manual for Bridge Evaluation) categorizes permit loads into two classes: 1) Routine/annual permits, and 2) Special permits (2) Limit States Permits are checked using the Strength II limit-state load combination with the Service II limit-state load combination optional for steel bridges to limit potential permanent deformations (3) purpose Permit load rating checks the safety and serviceability of bridges in the review of permit application for the passage of vehicles above the legally established weight limitations  156 Design Guide for Midas Civil  Process of Load Rating Flow Chart AASHTO LRFR 11 ( APPENDIX A6A) [Fig.3.2] Flow Chart of Load Rating The process starts with a bridge first being rated at the Design Inventory level under HL- 93 load model If the bridge is found to be satisfactory at this level of rating, it’s considered not to require posting for “AASHTO legal loads and state legal loads within the LRFD exclusion limits”, and hence the bridge can be evaluated directly for permit load vehicles However if the rating factor at the Design Inventory level is found to be less than 1.0, the bridge must be evaluated under either the Design Operating level or the Legal load level At these levels of rating if the bridge is found to be satisfactory it is considered not to require posting for “AASHTO legal loads and state legal loads having only minor variations form the AASHTO legal loads”, and the bridge can be evaluated for permit load vehicles If, however, the bridge is found to be not satisfactory, load posting will be required for legal loads and no permit analysis is allowed There is however the option for higher forms of evaluation, such as load testing of the bridge or the use of finite element modeling, for when a bridge is found to be unsatisfactory at the Legal load level and the engineer feels the bridge may not require posting Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 157 Chapter Steel Composite Bridge Load Rating : AASHTO-LRFR 2nd (2011) Modeling and Design Variables  Modeling Design Variables In this chapter, the design variables, the meaning behind the design requirements, and the design process for Steel Composite Load Rating in midas Civil are explained 1.1 Design Parameters for Steel Composite Load Rating In this section, the application of load rating and input method and meaning of the related variables are explained %QPVGPVU
1.1.1 Rating Design Code ೛ Rating > Bridge Rating Design > Steel Design> Rating Design Code 'ZRNCPCVKQP
1.1.1 Rating Design Code The program performs the load rating based on the code selected in this dialog box [Fig.3.3] Rating Design code 1.1.2 Steel Bridge Load Rating Parameters ೛ Rating > Bridge Rating Design > Steel Design> Rating Parameters 1.1.2 Steel Bridge Load Rating Parameters (1) The system factor is inputted according to the System Factor, ߮௦ , provided in AASHTO LRFR 2011 (Table 3.6) The system factor is multiplied to the flexural strength (Mn) and shear strength (Vn) and, therefore, applied to all elements (2) Strength Resistance Factor Strength Resistance Factor is defined The resistance factors are automatically set to the default values defined in AASHTO LRFR 12 The values also may be modified or entered manually (3) Girder Type for Box/Tub Section If the Single Box Section option is selected, the  158 Design Guide for Midas Civil  sections are considered as noncompact section; if the Multiple Box Section option is selected, the sections are considered as compact sections □ Consider St.Venant Torsion and Distortion Stress If the Multiple Box Section option is selected, lateral bending stress is considered in accordance with St Venant Torsion and Distortion Stress If the Single Box Section option is selected, the lateral bending stress is not considered (4) Options For Strength Limit State □ Appendix A6 for Negative Flexure Resistance in Web Compact/Noncompact Sections If this option is checked, Appendix A6 is applied for the flexural strength of straight composite Isections in negative flexure with compact/noncompact webs □ Mn≤1.3RhMy in Positive Flexure and Compact Sections(6.10.7.1.2-3) If this option is checked, Mn value is restricted to 1.3RhMy under positive flexure □ Post-buckling Tension-field Action for Shear Resistance (6.10.9.3.2) If this option is checked, post buckling resistance due to tension field action is considered in the nominal shear resistance of an interior stiffened web panel according to AASHTO LRFD 12 If not, Vn is taken as CVp (5) Service Limit State □ Service Limit State If this option is checked, the service limit is verified according to AASHTO LRFR 2011 6A.6.4 [Fig.3.4] Load Rating Parameters Dialog Box If Auto-Calculation is selected, the RF is calculated automatically according to LRFR standards For more details, please refer to "Application of AASHTO LRFD 12 in Midas Civil" Section 3.3 If User Input is selected, the capacities, parameters calculated for the verification of the RF, can be manually inputted The allowed compressive stress and tensile stress of the concrete need to be inputted. The compressive and tensile stresses inputted for Design Load and Legal Load are applied for the verification of the Design Load Rating and Legal Load Rating, respectively (6) Fatigue Limit State □ Fatigue Limit State Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 159  If this option is checked, the program checks the Fatigue Limit State according to AASHTO LRFR 11 6A.6.4 Also, the Load Test Measurement for the Application of Diagnostic Test Result can be selected between Strain and Displacement 1.1.3 Unbraced Length 1.1.3 Unbraced Length ೛ Rating > Bridge Rating Design > Steel Design> Unbraced Length The Unbraced Length for steel composite section is considered The value input here has higher priority than the value calculated from Span Group (1) Lb The Lateral Unbraced Length is used to calculate the lateral torsional buckling resistance for the compression flange of I-Girders If the Lateral Unbraced Length is not applied, the span information, if defined, is used for the calculation If the span information is not defined, element lengths are applied as the lateral unbraced length [Fig.3.5] Unbraced Length Dialog Box   1.1.4 Shear Connectors 1.1.4 Shear Connectors Studs are used as shear connectors and the following parameters are used for the calculation: (1) Category Category defined by 75yr-(ADTT)SL equivalent to Infinite Life ೛ Rating > Bridge Rating Design > Steel Design> Shear Connectors (2) Fu Shear Resistance of Shear Connector (3) Shear Connector Pane meters  160 Design Guide for Midas Civil  [Fig.3.7] Shear Connector Parameters (4) Length between Max.Moment and Zero Moment The length of the sections where shear connectors need to be considered is inputted for the calculation of the pitch at the strength limit state [Fig.3.6] Shear Connector Dialog Box     (5) Nominal Shear Force Calculation The type of nominal shear force calculation is determined for the calculation of the Nominal Shear Force, P, which his used to calculate the minimum number of shear connector, n, at the strength limit state Based on the calculation type selected, the equations used to calculate P are differed    1.1.5 Fatigue Parameter ೛ Rating > Bridge Rating Design > Steel Design> Fatigue Parameter 1.1.5 Fatigue Parameter (1) Category Category defined by 75yr-(ADTT)SL equivalent to infinite life (Table 6.6.1.2.3-2) (2) (ADTT)SL Number of trucks per day in a single-lane averaged over the design life (3.6.1.4.2) Value can be manually calculated as per 3.6.1.4.21 (3) n Number of cycles per truck passage Value can be taken from Table 6.6.1.2.5-2 (4) Longitudinal Warping Stress Range For the verification of fatigue, flexure stress is calculated as the summation of Longitudinal Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 161  Bending Stress Range and Longitudinal Warping Stress Range By choosing the Auto-Calculation option, fatigue vertical bending moment is simply increased by 10% for the longitudinal warping stress If the User Input option is selected, longitudinal bending stress range is summated with the inputted value of the Longitudinal Warping Stress Range for top or bottom flange depending upon the flexure condition at the section [Fig.3.8] Fatigue Parameters Dialog Box        1.1.6 Curved Bridge Information ඖ Rating > Bridge Rating Design > Steel Design> Curved Bridge Info 1.1.6 Curved Bridge Information Once the girder radius value of the element units in the steel composite section is entered, the corresponding elements are categorized as curved bridges The inputted girder radius is used for the following equations (1) Radius is used for the review of flange lateral bending moment caused due to the curvature (N is taken as 10.) M lat Ml NRD (LRFD 2012 c4.6.1.2.4b-1) where, Mlat : flange lateral bending moment M : major-axis bending moment l : unbraced length R : girder radius D : web depth  [Fig.3.9] Curved Bridge Information Dialog Box  162 Design Guide for Midas Civil N : a constant taken as 10 or 12 in past practice  [Table3.3] Convex and Concave Convex Concave (2) Radius is used for the review of shear connector's pitch and the moment of inertia of area for the longitudinal stiffener attached to web (3) Curve Type - Convex, Concave If Convex is selected, Left Stiffener is on the side of the web away from the center of curvature and Right Stiffener is on the side of the web toward the center of curvature If Concave is selected, the opposite case of the convex is applied The Left and Right are determined based on the progressing direction of the cross section Please refer to the table below for the equations applied to each case [Table3.4]Curvature Correction Factor for Longitudinal Stiffener Case Convex Concave Equation Left Stiffener E Right Stiffener E Left Stiffener E Right Stiffener E Z 1 Z 1 12 Z 1 12 Z 1 (6.10.11.3.3-3 (6.10.11.3.3-4 (6.10.11.3.3-4 (6.10.11.3.3-3 Where, ߚ : Curvature correction factor for longitudinal stiffener ܼ : Curvature Parameter 1.1.7 Diagnostic Test Result ೛ Rating > Bridge Rating Design > Steel Design!Diagnostic Test Result 1.1.7 Diagnostic Test Result Variables that are used to verify the load carrying capacity for the diagnostic test result are inputted in this dialog box (1) Auto calculation Deflection and impact factor are inputted for the diagnostic test (2) User Input The Adjustment Factor, K, is inputted by users K is used to calculate the load-rating factor for the live-load capacity based on the load test result, RFT Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 163  K  K a K b (8.8.2.3.1-1) where, Ka : accounts for both the benefit derived from the load test, if any, and consideration of the section factor (area, section modulus, ect.) resisting the applied test load Kb: accounts for the understanding of the load test results when with those predicted by theory [Fig.3.10] Diagnostic Test Result Dialog Box  1.2 Design Material Data In this section, the material property information input method for the Steel Composite Load Rating is explained %QPVGPVU 1.2.1 Rating material ೛ Rating > Bridge Rating Design > Steel Design> Rating material (1) Rating material 'ZRNCPCVKQP 1.2.1 Rating material In this dialog box, the Material Properties can be modified for the calculation of the structure capacity The material utilized for composite sections are provided in the SRC material properties The material should be defined as SRC Type (1) Modify Composite Material This dialog box is used to input material characteristics for the steel composite section design The material property values entered will have a priority over the values entered in Material Data dialog box 1) Steel of the Steel Girder Section □ Hybrid Factor Hybrid Factor is considered in the case where flanges and web have different material properties  164 Design Guide for Midas Civil  2) Concrete of the Concrete slab 3) Steel Rebar of the Concrete slab [Fig.3.11] Rating Material Dialog Box (2) Hybrid Factor (2) Hybrid Factor(Rh) When the check box for Hybrid Factor is selected, icon on the right is activated The different materials for the top and bottom flanges and web of the steel girder can be defined Hybrid Factor (Rh) is determined based on these material information [Fig.3.12] Hybrid Factor Dialog box Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 165  1.3 Settings for Load Rating In this section, how to define which part of the structure the load rating is performed and factors and rating levels for each part are explained %QPVGPVU 'ZRNCPCVKQP 1.3.1 Rating Group Setting 1.3.1 Rating Group Setting ೛ Rating > Bridge Rating Design > Steel Design> Rating Group Setting The Bridge Rating Group Setting Dialog allows users to apply Condition Factors per different groups defined already and i- and j-end check positions (1) Inputting different Condition Factors and other design features are faster with the elements defined in Groups Selected Groups are targeted for the design of the Rating Factor Structure Group is defined in Define Structure Group at: ೛ Tree Menu > Group> Structure Group>New [Fig.3.13] Rating Group Setting Dialog Box [Fig.3.14] Structure Group Dialog Box (2) Different values of Condition Factor, ࣐ࢉ , can be applied to different Structure Groups of elements In the program, the Condition Factor is internally multiplied to Nominal Flexural Strength, Nominal Flexural Resistance, Nominal Shear Strength and Nominal Fatigue Resistance to calculate the Road Factor For more details, please refer to [Table 3.7] and [Table 3.8] (3) The Check Position, i- and/or j- end, is considered and selected for the Groups selected for the design  166 Design Guide for Midas Civil  1.3.2 Define Rating Case ೛ Rating > Bridge Rating Design > Steel Design> Define Rating Case 1.3.2 Define Rating Case In Define Rating Case Dialog, Load Factor is defined for each of the Service Limit State, Strength Limit State and Fatigue Limit State (1) For the Fatigue Limit State calculation, Unfactored dead load should be selected (2) Default Load Factors are automatically inputted for each Load Type (DC, DW, ) as per LRFR 2012 and can be manually modified by users Maximum and Minimum Load Factors are inputted for DC(Before), DC(After), and DW The default maximum and minimum values are provided according to LRFR 2011 Table 6A.4.2.2-1 and LRFD 2012 Table 3.4.102 Only one load factor is inputted for the Temperature Load, but the load factor is used as positive and negative (+, -) for the calculation DC(Before) is for the state before the concrete deck is activated DC(After) is for the state after the concrete deck is activated DC(After) considers the Erection load case, if defined by user, and the stress caused by the time dependent material property, Creep & Shrinkage Per different Load Type, Load Cases can be additionally inputted per different Load Type and reflected in the Load Rating Factor calculation [Fig.3.15] Define Rating Case Dialog Box (3) For different Load Types, different Load Cases are selected Member forces before the composite state are applied to Dead Load (CS) and member forces after the composite state are applied to Erection Load Static Load case is defined at: ೛ Load > Load Type > Create Load Cases > Static Load Cases Information inputted in the Load case internally generates the 12 Types results (Fx-max, Mymin) per nodes in the calculation For each node, Max/Min forces are calculated per total degree of freedom (DOF) for each node (4) Live Load and Load Factor are inputted Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 167  separately for the Primary Vehicle and Adjacent Vehicle When is clicked, the load combinations and corresponding Load Factors are generated When the load combination is clicked, the load combination and load factors are inputted in the Rating Case Dialog Box Each Live Load should be inputted prior in Moving Load Cases at: ඖLoad > Load Type > Moving Load > Moving Load Analysis Data > Moving Load Cases) [Fig.3.16] Live Load Factor for Rating Dialog Box (5) Evaluation Live Load Model Load Rating flow as per LRFR standard is explained in [Fig.3.2] The program does not automatically follow the flow of [Fig.3.2] In this Live Load Factors for Rating Dialog, rating level needs to be defined as well as the load cases In the "Introduction" Chapter, Section 2.2 and Section 2.3, different purposes and applications of performing Legal Load Rating level and Permit Load Rating level are explained However, in this dialog box, the Legal Level and Permit Level both needs to be selected because the same LRFD Load Factors are used in the two level checks 1.3.3 Position for Rating Output ೛ Rating > Bridge Rating Design > Steel Design ! Position for Rating Output 1.3.3 Position for Rating Output In this Dialog, the Position for Rating Output is inputted (1) Users can select Groups in the Filters for Load Rating Summary and define the Position for Rating Output (2) When Apply is clicked in this dialog box, the elements to be printed in the output is defined and saved [Fig.3.17] Position for Rating output Dialog Box  168 Design Guide for Midas Civil  1.3.4 Rating Design Tables 1.3.4 Rating Design Force/Moment Tables ೛ Rating > Bridge Rating Design > Steel Design!Rating Design Tables > Design Force/Moment For the selected load combinations, design member force (longitudinal-direction moment (My), transverse-direction moment (Mz), shear (Vu)) are calculated at different part(s) of the elements per construction stages [fig.3.18] Rating Design Force/Moment Tables Dialog Box 1.4 Composite Section Data Steel composite section is composed of steel girder and concrete slab Additional stiffeners may be arranged in the steel girder; longitudinal and sub reinforcement rebars may be arranged in the concrete slab In this section, Steel Composite Load Rating features and functions and related section input method and design variables are explained $POUFOUT
1.4.1 Longitudinal Reinforcement ೛ Rating > Bridge Rating Design > Steel Design> Longitudinal Reinforcement ([SODQDWLRQ
1.4.1 Longitudinal Reinforcement In a steel composite section, the longitudinal reinforcements are arranged within the concrete deck The strength is calculated as shown in the below table [Table3.5] Material Application for Strength Calculation Positive Flexure Negative Flexure Concrete Slab Apply None Reinforce -ment None Applied Case Figure [Fig.3.19] Longitudinal Reinforcement Dialog     Chapter 3.Steel Composite Bridge Load Rating - AASHTO LRFR 2011 169 ... responsibility for the use of MIDAS Family Program (midas Civil, midas FEA, midas FX+, midas Gen, midas Drawing, midas SDS, midas 'd^͕^ŽŝůtŽƌŬƐ͕ŵŝĚĂƐE&y͖ŚĞƌĞŝŶĂŌĞƌƌĞĨĞƌƌĞĚƚŽĂƐ MIDAS package”) or... (Concrete) (1 ) Calculate Ts, Cs (Reinforcement) (2 ) Calculate Tps (Tendon) (3 ) (4 ) Cc+Cs-(Ts+Tps)=0? NO YES Get neutral axis depth, c [Fig.1 4] Flow chart to calculate neutral axis depth, c (1 )... tension  20 Design Guide for midas Civil AASHTO LRFD14 (5 .8.3.4.2) (Eq 5.8.6.5-3) K 1 f pc (1 .35) 0.0632 f c ' AASHTO LRFD14 (5 .8.6.3) (Eq 5.8.6.3-3) In midas Civil, the value of K is calculated