K2Cyclic tests for qualification of beam-to-column and link-to-column connections

K2.3a Sources of Inelastic Rotation

The inelastic rotation shall be computed based on an analysis of test specimen deformations. Sources of inelastic rotation include, but are not limited to, yielding of members, yielding of connection elements and connectors, yielding of reinforcing steel, inelastic deformation of concrete, and slip between members and connection elements. For beam-to-column moment connections in SMF, IMF, C-SMF, and C-IMF, inelastic rotation is computed based upon the assumption that inelastic action is concentrated at a single point located at the intersection of the centerline of the beam with the centerline of the column. For link-to-column connections in EBF, inelastic rotation shall be computed based upon the assumption that inelastic action is concentrated at a single point located at the intersection of the centerline of the link with the face of the column.

Inelastic rotation shall be developed in the test specimen by inelastic action in the same members and connection elements as anticipated in the prototype (in other words, in the beam or link, in the column panel zone, in the column outside of the panel zone, or in connection elements) within the limits described in the following. The percentage of the total inelastic rotation in the test specimen that is developed in each member or connection element shall be within 25% of the anticipated percentage of the total inelastic rotation in the prototype that is developed in the corresponding member or connection element.

K2.3b Members

The size of the beam or link used in the test specimen shall be within the following limits:

• (a) The depth of the test beam or link shall be no less than 90% of the depth of the prototype beam or link.
• (b) For SMF, IMF, and EBF, the weight per foot of the test beam or link shall be no less than 75% of the weight per foot of the prototype beam or link.
• (c) For C-SMF and C-IMF, the weight per foot of the structural steel member that forms part of the test beam shall be no less than 75% of the weight per foot of the structural steel member that forms part of the prototype beam.

The size of the column used in the test specimen shall correctly represent the inelastic action in the column in accordance with the requirements in Section K2.3a. In addition, in SMF, IMF, and EBF, the depth of the test column shall be no less than 90% of the depth of the prototype column. In C-SMF and C-IMF, the depth of the structural steel member that forms part of the test column shall be no less than 90% of the depth of the structural steel member that forms part of the prototype column.

The width-to-thickness ratios of compression elements of steel members of the test specimen shall meet the width-to-thickness limitations as specified in these Provisions for members in SMF, IMF, C-SMF, C-IMF, or EBF, as applicable.

Exception: The width-to-thickness ratios of compression elements of members in the test specimen are permitted to exceed the width-to-thickness limitations specified in these Provisions if both of the following conditions are met.

• (1) The width-to-thickness ratios of compression elements of the members of the test specimen are no less than the width-to-thickness ratios of compression elements in the corresponding prototype members.
• (2) Design features that are intended to restrain local buckling in the test specimen, such as concrete encasement of steel members, concrete filling of steel members, and other similar features, are representative of the corresponding design features in the prototype.

Extrapolation beyond the limitations stated in this section is permitted subject to qualified peer review and approval by the AHJ.

K2.3c Reinforcing Steel Amount, Size, and Detailing

The total area of the longitudinal reinforcing bars shall not be less than 75% of the area in the prototype and individual bars shall not have an area less than 70% of the maximum bar size in the prototype.

Design approaches and methods used for anchorage and development of reinforcement, and for splicing reinforcement in the test specimen, shall be representative of the prototype.

The amount, arrangement, and hook configurations for transverse reinforcement shall be representative of the bond, confinement, and anchorage conditions of the prototype.

K2.3d Connection Details

The connection details used in the test specimen shall represent the prototype connection details as closely as possible. The connection elements used in the test specimen shall be a full-scale representation of the connection elements used in the prototype for the member sizes being tested.

K2.3e Continuity Plates

The size and connection details of continuity plates used in the test specimen shall be proportioned to match the size and connection details of continuity plates used in the prototype connection as closely as possible.

K2.3f Steel Strength for Steel Members and Connection Elements

The following additional requirements shall be satisfied for each steel member or connection element of the test specimen that supplies inelastic rotation by yielding:

• (a) The yield strength shall be determined as specified in Section K2.6a. The use of yield stress values that are reported on certified material test reports in lieu of physical testing is prohibited for the purposes of this section.
• (b) The yield strength of the beam flange, as tested in accordance with Section K2.6a, shall not be more than 15% below $R_{y} F_{y}$ for the grade of steel to be used for the corresponding elements of the prototype. $R_{y} F_{y}$ shall be determined in accordance with Section A3.2.
• (c) The yield strength of the columns and connection elements shall not be more than 15% above or below $R_{y} F_{y}$ for the grade of steel to be used for the corresponding elements of the prototype.

User Note: Based upon the preceding criteria, steel of the specified grade with a specified minimum yield stress, $F_{y}$, of up to and including 1.15 times $R_{y} F_{y}$ for the steel tested should be permitted in the prototype. In production, this limit should be checked using the values stated on the steel manufacturer's material test reports.

K2.3g Steel Strength and Grade for Reinforcing Steel

Reinforcing steel in the test specimen shall have the same ASTM designation as the corresponding reinforcing steel in the prototype. The specified minimum yield stress of reinforcing steel in the test specimen shall not be less than the specified minimum yield stress of the corresponding reinforcing steel in the prototype.

K2.3h Concrete Strength and Density

The specified compressive strength of concrete in members and connection elements of the test specimen shall be at least 75% and no more than 125% of the specified compressive strength of concrete in the corresponding members and connection elements of the prototype.

The compressive strength of concrete in the test specimen shall be determined in accordance with Section K2.6d.

The density classification of the concrete in the members and connection elements of the test specimen shall be the same as the density classification of concrete in the corresponding members and connection elements of the prototype. The density classification of concrete shall correspond to either normal weight, lightweight, all-lightweight, or sand-lightweight as defined in ACI 318.

K2.3i Welded Joints

Welds on the test specimen shall satisfy the following requirements:

• (a) Welding shall be performed in conformance with welding procedure specifications (WPS) as required in AWS D1.1/D1.1M. The WPS essential variables shall satisfy the requirements in AWS D1.1/D1.1M and shall be within the parameters established by the filler-metal manufacturer. The tensile strength and Charpy V-notch (CVN) toughness of the welds used in the test specimen shall be determined by tests as specified in Section K2.6e, made using the same filler metal classification, manufacturer, brand or trade name, diameter, and average heat input for the WPS used on the test specimen. The use of tensile strength and CVN toughness values that are reported on the manufacturer’s typical certificate of conformance, in lieu of physical testing, is not permitted for purposes of this section.
• (b) The specified minimum tensile strength of the filler metal used for the test specimen shall be the same as that to be used for the welds on the corresponding prototype. The tensile strength of the deposited weld as tested in accordance with Section K2.6c shall not exceed the tensile strength classification of the filler metal specified for the prototype by more than 25 ksi (170 MPa).

CYCLIC TESTS FOR QUALIFICATION OF BEAM-TO-COLUMN

AND LINK-TO-COLUMN CONNECTIONS

User Note: Based upon the criteria in (b), should the tested tensile strength of the weld metal exceed 25 ksi (170 MPa) above the specified minimum tensile strength, the prototype weld should be made with a filler metal and WPS that will provide a tensile strength no less than 25 ksi (170 MPa) below the tensile strength measured in the material test plate. When this is the case, the tensile strength of welds resulting from use of the filler metal and the WPS to be used in the prototype should be determined by using an all-weld-metal tension specimen. The test plate is described in AWS D1.8/D1.8M, clause A3, and shown in AWS D1.8/D1.8M, Figure A.1.

• (c) The specified minimum CVN toughness of the filler metal used for the test specimen shall not exceed that to be used for the welds on the corresponding prototype. The tested CVN toughness of the weld as tested in accordance with Section K2.6c shall not exceed the minimum CVN toughness specified for the prototype by more than 50%, nor 25 ft-lb (34 J), whichever is greater.

User Note: Based upon the criteria in (c), should the tested CVN toughness of the weld metal in the material test specimen exceed the specified CVN toughness for the test specimen by 25 ft-lb (34 J) or 50%, whichever is greater, the prototype weld can be made with a filler metal and WPS that will provide a CVN toughness that is no less than 25 ft-lb (34 J) or 33% lower, whichever is lower, below the CVN toughness measured in the weld metal material test plate. When this is the case, the weld properties resulting from the filler metal and WPS to be used in the prototype can be determined using five CVN test specimens. The test plate is described in AWS D1.8/D1.8M, clause A3, and shown in AWS D1.8/D1.8M, Figure A.1.

• (d) The welding positions used to make the welds on the test specimen shall be the same as those to be used for the prototype welds.
• (e) Weld details such as backing, tabs, and access holes used for the test specimen welds shall be the same as those to be used for the corresponding prototype welds. Weld backing and weld tabs shall not be removed from the test specimen welds unless the corresponding weld backing and weld tabs are removed from the prototype welds.
• (f) Methods of inspection and nondestructive testing (NDT), and standards of acceptance used for test specimen welds, shall be the same as those to be used for the prototype welds.

User Note: The filler metal used for production of the prototype may be of a different classification, manufacturer, brand or trade name, and diameter if Sections K2.3i(b) and K2.3i(c) are satisfied. To qualify alternate filler metals, the tests as prescribed in Section K2.6e should be conducted.

K2.3j Bolted Joints

The bolted portions of the test specimen shall replicate the bolted portions of the prototype connection as closely as possible. Additionally, bolted portions of the test specimen shall satisfy the following requirements:

• (a) The bolt grade (for example, ASTM F3125/F3125M Grades A325, A325M, A490, A490M, F1852, F2280) used in the test specimen shall be the same as that to be used for the prototype, except that heavy hex bolts are permitted to be substituted for twist-off-type tension control bolts of equal specified minimum tensile strength, and vice versa.
• (b) The type and orientation of bolt holes (standard, oversized, short slot, long slot, or other) used in the test specimen shall be the same as those to be used for the corresponding bolt holes in the prototype.
• (c) When inelastic rotation is to be developed either by yielding or by slip within a bolted portion of the connection, the method used to make the bolt holes (drilling, sub-punching and reaming, or other) in the test specimen shall be the same as that to be used in the corresponding bolt holes in the prototype.
• (d) Bolts in the test specimen shall have the same installation (pretensioned or other) and faying surface preparation (no specified slip resistance, Class A or B slip resistance, or other) as that to be used for the corresponding bolts in the prototype.

K2.3k Load Transfer Between Steel and Concrete

Methods used to provide load transfer between steel and concrete in the members and connection elements of the test specimen, including direct bearing, shear connection, friction, and others, shall be representative of the prototype.

K2.4a General Requirements

The test specimen shall be subjected to cyclic loads in accordance with the requirements prescribed in Section K2.4b for beam-to-column moment connections in SMF, IMF, C-SMF, and C-IMF, and in accordance with the requirements prescribed in Section K2.4c for link-to-column connections in EBF.

Loading sequences to qualify connections for use in SMF, IMF, C-SMF, or C-IMF with columns loaded orthogonally shall be applied about both axes using the loading sequence specified in Section K2.4b. Beams used about each axis shall represent the most demanding combination for which qualification or prequalification is sought. In lieu of concurrent application about each axis of the loading sequence specified in Section K2.4b, the loading sequence about one axis shall satisfy requirements of Section K2.4b, while a concurrent load of constant magnitude, equal to the expected strength of the beam connected to the column about its orthogonal axis, shall be applied about the orthogonal axis.

Loading sequences other than those specified in Sections K2.4b and K2.4c are permitted to be used when they are demonstrated to be of equivalent or greater severity.

K2.4b Loading Sequence for Beam-to-Column Moment Connections

Qualifying cyclic tests of beam-to-column moment connections in SMF, IMF, C-SMF, and C-IMF shall be conducted by controlling the story drift angle, θ, imposed on the test specimen, as specified below:

• (a) 6 cycles at $\theta=0.00375$ rad
• (b) 6 cycles at $\theta=0.0005$ rad
• (c) 6 cycles at $\theta=0.0075$ rad
• (d) 4 cycles at θ = 0.01 rad
• (e) 2 cycles at $\theta=0.015$ rad
• (f) 2 cycles at $\theta=0.02$ rad
• (g) 2 cycles at θ = 0.03 rad
• (h) 2 cycles at $\theta=0.04$ rad

Continue loading at increments of $\theta=0.01$ rad, with two cycles of loading at each step.

K2.4c Loading Sequence for Link-to-Column Connections

Qualifying cyclic tests of link-to-column moment connections in EBF shall be conducted by controlling the total link rotation angle, $\gamma_{\text {total }}$, imposed on the test specimen, as follows:

• (a) 6 cycles at $\gamma_{\text {total }}=0.000375$ rad
• (b) 6 cycles at $\gamma_{\text {total }}=0.0005$ rad
• (c) 6 cycles at $\gamma_{\text {total }}=0.00075$ rad
• (d) 6 cycles at $\gamma_{\text {total }}=0.01$ rad
• (e) 4 cycles at $\gamma_{\text {total }}=0.015$ rad
• (f) 4 cycles at $\gamma_{\text {total }}=0.02$ rad
• (g) 2 cycles at $\gamma_{\text {total }}=0.03$ rad
• (h) 1 cycle at $\gamma_{\text {total }}=0.04$ rad
• (i) 1 cycle at $\gamma_{\text {total }}=0.05$ rad
• (j) 1 cycle at $\gamma_{\text {total }}=0.07$ rad
• (k) 1 cycle at $\gamma_{\text {total }}=0.09$ rad

Continue loading at increments of $\gamma_{\text {total }}=0.02$ rad, with one cycle of loading at each step.

K2.6a Tension Testing Requirements for Structural Steel Material Specimens

Tension testing shall be conducted on samples taken from material test plates in accordance with Section K2.6c. The material test plates shall be taken from the steel of the same heat as used in the test specimen. Tension-test results from certified material test reports shall be reported but shall not be used in lieu of physical testing for the purposes of this section. Tension testing shall be conducted and reported for the following portions of the test specimen:

• (a) Flange(s) and web(s) of beams and columns at standard locations
• (b) Any element of the connection that supplies inelastic rotation by yielding

K2.6b Tension Testing Requirements for Reinforcing Steel Material Specimens

Tension testing shall be conducted on samples of reinforcing steel in accordance with Section K2.6c. Samples of reinforcing steel used for material tests shall be taken from the same heat as used in the test specimen. Tension-test results from certified material test reports shall be reported, but shall not be used in lieu of physical testing for the purposes of this section.

K2.6c Methods of Tension Testing for Structural and Reinforcing Steel Material Specimens

Tension testing shall be conducted in accordance with ASTM A6/A6M, ASTM A370, and ASTM E8/E8M, as applicable, with the following exceptions:

• (a) The yield strength, $F_{y}$, that is reported from the test shall be based upon the yield strength definition in ASTM A370, using the offset method at 0.002 in./in. strain.
• (b) The loading rate for the tension test shall replicate, as closely as practical, the loading rate to be used for the test specimen.

K2.6d Testing Requirements for Concrete

Test cylinders of concrete used for the test specimen shall be made and cured in accordance with ASTM C31/C31M. At least three cylinders of each batch of concrete used in a component of the test specimen shall be tested within five days before or after of the end of the cyclic qualifying test of the test specimen. Tests of concrete cylinders shall be in accordance with ASTM C39/C39M. The average compressive strength of the three cylinders shall be no less than 90% and no greater than 150% of the specified compressive strength of the concrete in the corresponding member or connection element of the test specimen. In addition, the average compressive strength of the three cylinders shall be no more than 3,000 psi (21 MPa) greater than the specified compressive strength of the concrete in the corresponding member or connection element of the test specimen.

Exception: If the average compressive strength of three cylinders is outside of these limits, the specimen is still acceptable if supporting calculations or other evidence is provided to demonstrate how the difference in concrete strength will affect the connection performance.

K2.6e Testing Requirements for Weld Metal Material Specimens

Weld metal testing shall be conducted on samples extracted from the material test plate, made using the same filler metal classification, manufacturer, brand or trade name, and diameter, and made using the same average heat input as used in the welding of the test specimen. The tensile strength and CVN toughness of weld material specimens shall be determined in accordance with Standard Methods for Mechanical Testing of Welds (AWS B4.0 or AWS B4.0M). The use of tensile strength and CVN toughness values that are reported on the manufacturer’s typical certificate of conformance in lieu of physical testing is not permitted for use for purposes of this section.

The same WPS shall be used to make the test specimen and the material test plate. The material test plate shall use base metal of the same grade and type as was used for the test specimen, although the same heat need not be used. If the average heat input used for making the material test plate is not within ±20% of that used for the test specimen, a new material test plate shall be made and tested.