• Codes
  • Features

    Features Overview

    Go to features
    Reference

    Reference.

    A reliable and up-to-date source of codes.
    Research

    Research.

    Rapidly and efficiently calculate project parameters.
    Collaboration

    Collaboration.

    Get everyone on the same page and streamline code research.
    Workflows
    Architects General Contractor Building Official & Plans Examiner Inspectors Owner Subcontractors Code Consultants
  • Pricing
  • Login
  • Sign Up
Sign Up
Login
  • Code Library
  • Features
  • Pricing
  • About
  • Careers
  • Help
  • Contact
  • Terms
  • Privacy
Sign Up
Upgrade to Premium
Code calculators: Code Calculators automatically generates a detailed list of requirements.
REFERENCE
Amendment Styling
Industry-leading search
Suggested code sections
Code diagrams
RESEARCH
Code calculators
Filter by topic
Code compare
Code sheet exports
COLLABORATION
Team projects
Bookmarks
Comments
START 2 WEEK FREE TRIAL
Have an account? Sign in
// CODE SNIPPET

Article 4 Procedures for Moment-Resisting Systems

California Administrative Code 2019 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems
JUMP TO FULL CODE CHAPTER

4.0 Introduction

Moment frames develop their resistance to lateral forces through the flexural strength and continuity of beam and column elements. Moment frames may be classified as special, intermediate and ordinary frames.

For evaluations using these regulations, it is not necessary to determine the type of frame in the building. The issues are addressed by appropriate acceptance criteria in the specified procedures. For determination of element capacities, see Article 2, Section 2.4.9.

4.1 Frames With Infill Walls

4.1.1 Interfering Walls

All infill walls placed in moment frames are isolated from structural elements.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is an inappropriate connection of the wall to the frame. Evaluate the relative strength and stiffness of the walls and frames, considering the nature and size of the joint or connection between the wall and the frame. If the strength of the walls is not commensurate with the stiffness, the building should be treated as Type 7 or Type 10 (Article 2, Section 2.2.3 "Common Building Types"), a frame with infill walls. If the infill walls do not extend the full story height and are not properly isolated from the frame columns, evaluate the column shear demand and capacity, based on a column height equal to the clear distance from the top of the wall to the bottom of the slab or beam above, amplifying the design forces in the short column by Cd/2, but not less than 1.5. The shear demand need not exceed the shear capacity corresponding to flexural capacity of the column, based on a column height equal to the clear distance from the top of the wall to the bottom of the slab or beam above.

4.2 Steel Moment Frames

Welded steel moment frames may be subject to detailed frame joint evaluation requirements, as outlined in this section. The purpose of this joint evaluation is to determine if the building has experienced joint damage in strong ground shaking.

4.2.0.1 Preliminary Screening

All welded steel moment frame structures shall undergo a detailed frame joint evaluation if the building is located at a site that has experienced the following:

  1. An earthquake of magnitude greater than or equal to 6.5 that produced ground motion in excess of 0.20 g; or
  2. An earthquake that generated ground motion in excess of 0.30 g.

The ground motion estimates shall be based on actual instrumental recordings in the vicinity of the building. When such ground motion records are not available, ground motion estimates may be based on empirical or analytical techniques. All ground motion estimates shall reflect the site-specific soil conditions.

4.2.0.2 Additional Indicators

A detailed frame joint evaluation of the building shall be performed if any of the following apply:

  1. Significant structural damage is observed in one or more welded steel moment frame structures located within 1 km of the building on sites with similar, or more firm, soil properties;
  2. An earthquake having a magnitude of 6.5 or greater, where the structure is located within 5 km of the trace of a surface rupture or within the vertical projection of the rupture area when no surface rupture has occurred;
  3. Significant architectural or structural damage has been observed in the building following an earthquake; or
  4. Entry to the building has been limited by the building official because of earthquake damage, regardless of the type or nature of the damage.

4.2.0.3 Connection Inspections

Detailed frame joint evaluations shall be performed in accordance with the procedures in the Interim Guidelines: Evaluation, Repair, Modification and Design of Welded Steel Moment Frame Structures, FEMA 267, August 1995.

4.2.1 Drift Check

The building satisfies the Quick Check of the frame drift.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. Check drift using the procedures in Section 2.4.7.1 against the prescribed limit. If the drift exceeds the limiting drift at any story level, the structure shall be evaluated with full-frame analysis using the anticipated distribution of lateral forces to the moment-resisting frames and including P-delta effects. Check the other statements using the demand from this analysis.

4.2.2 Compact Members

All moment-frame elements meet the compact section requirements of the basic AISC documents.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the member capacities. Check member capacities, using member demands obtained from a frame analysis. Calculate member capacities using appropriate criteria for noncompact sections. Check the member capacities using appropriate R values (e.g., noncompact members require use of the R value for ordinary frames).

4.2.3 Beam Penetrations

All openings in frame-beam webs have a depth less than one-fourth of the beam depth and are located in the center half of the beams.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the shear capacity of the beam. Check that the shear capacity of the beam is sufficient to develop the flexural plastic hinge. If the shear capacity is insufficient to develop the flexural capacity of the member, use the R value for ordinary frames.

4.2.4 Moment Connections

All beam-column connections in the lateral-force-resisting moment frame have full-penetration flange welds and a bolted or welded web connection.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the connection. Check the connection on the basis of its strength. Check the member capacities using appropriate R values. Connections that do not develop the flexural capacity of the member require use of the R value for ordinary frames.

4.2.5 Column Splices

All column splice details of the moment-resisting frames include connection of both flanges and the web.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the bolts or welds in the connection. Check the adequacy of the splice connection for all gravity and seismic loads. Amplify the seismic load for partial-penetration welded splices by the factor Cd/2.

4.2.6 Joint Webs

All web thicknesses within joints of moment-resisting frames meet AISC criteria for web shear.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the web. Calculate the joint shear capacity using formulas given in the AISC provisions and compare it to the demand from an equivalent lateral force analysis or the average column shear, Vc, calculated for the Quick Check for drift.

4.2.7 Girder Flange Continuity Plates

There are girder flange continuity plates at joints.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the joint. Check joints without such plates using AISC provisions, using the R value for ordinary frames.

4.2.8 Strong Column/Weak Beam

At least one half of the joints in each story are strong column/weak beam (33 percent on every line of moment frame). Roof joints need not be considered.

The deficiency is excessive ductility demand and displacement in a single story. Compare beam and column moment capacities, including the effect of axial force. The evaluator may consider this condition mitigated if the joints in the building meet the provisions of Section 2710(g)5 of the 1992 edition of Part 2, Title 24. Conforming buildings which do not meet those provisions shall be placed in SPC 4.

4.2.9 Out-Of-Plane Bracing

Beam-column joints are braced out-of-plane.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the stability of the beam-column joint. Verify the joint bracing by visual observation.

4.2.10 Pre-Northridge Earthquake Welded Moment Frame Joints

Welded steel moment frame beam-column joints are designed and constructed in accordance with recommendations in FEMA 267, Interim Guidelines: Evaluation, Repair, Modification and Design of Welded Steel Moment Frame Structures, August 1995.

For buildings constructed under permit issued after October 25, 1994, the evaluator may consider this condition as mitigated. The deficiency is in the ductility of the beam-column joint. The following procedures shall be used for categorizing buildings with welded steel moment frame joints.

Procedure for conforming buildings: Conforming buildings located in Seismic Zone 4 of 1995 California Building Code (CBC) or later version of the CBC, within a zone designated as being potentially subject to near field effects in strong ground shaking, shall be placed in SPC 3.

All other conforming buildings shall be placed in SPC 4.

Procedure for nonconforming buildings: Nonconforming buildings shall be placed in SPC 2.

4.3 Concrete Moment Frames

The details covered in evaluation statements in Sections 4.3.4 through 4.3.14 will be found in frames that have been designed and detailed for ductile behavior. If any one detail is not present, the frames are not considered to meet life-safety goals, and nonconforming buildings shall be placed in SPC 1. For conforming buildings, see the appropriate evaluation statement. For buildings designed and constructed in accordance with the 1989 or later editions of Part 2, Title 24, the building may assume "true" responses to all evaluation statements in this section.

4.3.1 Shearing Stress Check

The building satisfies the Quick Check of the average shearing stress in the columns.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. Perform a quick estimation of the average shearing stress in the columns according to the procedure specified in Section 2.4.7.2. If the average column shear stress is greater than 60 psi, a more detailed evaluation of the structure shall be performed. This evaluation shall employ a more accurate estimation of the level and distribution of the lateral loads; use the procedures outlined in Section 2.4.

4.3.2 Drift Check

The building satisfies the Quick Check of story drift.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. Check drift using the procedures in Section 2.4.7.1 against the prescribed limit. If the drift exceeds the limiting drift at any story level, the structure shall be evaluated with full-frame analysis using the anticipated distribution of lateral forces to the moment-resisting frames and including P-delta effects as found in Section 2.4.1. Check the other statements using the demand from this analysis.

4.3.3 Prestressed Frame Elements

The lateral-load-resisting frames do not include any prestressed or post-tensioned elements.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the frames during inelastic straining. Check the capacity of the members and joints using all of the mild steel reinforcing that is available and bonded prestressing when appropriate. The R value used for evaluation shall reflect the ductility and damping of the system. Where better information is not available, multiply the R value selected on the basis of mild reinforcement by 0.75 to account for the effect of prestressing.

4.3.4 Joint Eccentricity

There are no eccentricities larger than 20 percent of the smallest column plan dimension between girder and column centerlines.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is in the strength of the frame, either the members or the joints or both. Evaluate the frames considering the additional shear stresses caused by the joint torsion.

4.3.5 No Shear Failures

The shear capacity of frame members is greater than the moment capacity.

For conforming buildings, the evaluator may consider this condition as mitigated, and no calculations are necessary. The deficiency is inadequate shear capacity in the columns or beams. Compare Ve with the member shear capacity, ϕVn, calculated in accordance with ACI 318 Appendix. The ratio Ve / ϕVn shall be less than or equal to 1.0.

4.3.6 Strong Column/Weak Beam

The moment capacity of the columns is greater than that of the beams.

The deficiency is in column capacity. Compare the sum of the beam moment capacities to that of the column capacities. Include the participation of the slab in the beam capacities. The moment capacity to be compared is the plastic moment, Mpr. The ratio of the sum of the Mpr for the columns to the sum of the Mpr for the beams is required to be not less than 1.2. Conforming buildings which do not meet this criteria shall be placed in SPC 4.

4.3.7 Stirrup and Tie Hooks

The beam stirrups and column ties are anchored into the member cores with hooks of 135 degrees or more.

The deficiency is in the shear resistance and confinement of the member. Determine if beam stirrups and column ties are appropriately anchored into member cores with hooks of 135 degrees or more. Conforming buildings which do not meet this criteria shall be placed in SPC 4.

4.3.8 Column-Tie Spacing

Frame columns have ties spaced at d/4 or less throughout their length and at 8 db, or less at all potential plastic hinge regions.

The deficiency is in the shear capacity of the column. Report this condition as a deficiency. Conforming buildings which do not meet this criteria shall be placed in SPC 4.

4.3.9 Column-Bar Splices

All column bar lap splice lengths are greater than 35 db, long and are enclosed by ties spaced at 8 db, or less.

The deficiency is in the strength and ductility of the column. Compare the splice length provided with that required by Sections 12.2 and 12.15 of the ACI 318 provisions. Conforming buildings which do not meet this criteria shall be placed in SPC 4.

SEE MORE

Related Code Sections


Article 4 Seismic Evaluation Procedures for Hospital Buildings, Procedures for Moment-Resisting Systems
Moment frames develop their resistance to lateral forces through the flexural strength and continuity of beam and column elements. Moment frames may ...
California Administrative Code 2019 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems
Article 4 Seismic Evaluation Procedures for Hospital Buildings, Procedures for Moment-Resisting Systems
Moment frames develop their resistance to lateral forces through the flexural strength and continuity of beam and column elements. Moment frames may ...
California Administrative Code 2016 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems
4.4 Seismic Evaluation Procedures for Hospital Buildings, Precast Concrete Moment Frames
-force-resisting system can develop the capacity of the connected members. For conforming buildings, the evaluator may consider this condition ...
California Administrative Code 2016 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems > 4.4 Precast Concrete Moment Frames
4.0 Seismic Evaluation Procedures for Hospital Buildings, Introduction
Moment frames develop their resistance to lateral forces through the flexural strength and continuity of beam and column elements. Moment frames may ...
California Administrative Code 2019 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems > 4.0 Introduction
4.0 Seismic Evaluation Procedures for Hospital Buildings, Introduction
Moment frames develop their resistance to lateral forces through the flexural strength and continuity of beam and column elements. Moment frames may ...
California Administrative Code 2016 > 6 Seismic Evaluation Procedures for Hospital Buildings > 4 Procedures for Moment-Resisting Systems > 4.0 Introduction
Help Contact Us Privacy Terms
Shared projects
Shared projects
Projects provide a dedicated space to collaborate on code research.
Search
Search
Don't miss relevant code. Quickly locate sections across your jurisdiction.
Code diagrams
Code diagrams
Unpack the code through illustrations and descriptions.
View thousands of relevant UL Certified products and assemblies that help achieve code compliance
View thousands of relevant UL Certified products and assemblies that help achieve code compliance
Access to UL product and system certification information.
Code sheet exports
Code sheet exports
Generate a code sheet that integrates with your drawing set.
Code Compare
Code Compare
Highlight differences between any two building codes.
Code Calculators
Code Calculators
Code calculators automatically generate a detailed list of requirements.
UpCodes Premium
Leverage the most sophisticated code compliance platform.
TRY FREE FOR TWO WEEKS VISIT PRICING
Join the waitlist
We are looking to gauge the level of interest in linking UL product and system certification information alongside related code sections.

Let us know your email and we’ll ping you once it’s ready! Learn more.

Thank you for your interest!

If you’re open to it, we would love to jump on the phone to make sure we’re building this in the best way possible for your workflow. Any insight or advice would be greatly appreciated. We’ve sent you an email with a calendar link to book at time with us.


Cancel
Get Early Access
UpCodes Premium
Leverage the full code compliance platform.
START 2 WEEK FREE TRIAL LEARN MORE