Proceedings of the 2016 24th International Conference on Nuclear Engineering ICONE24 June 26-30, 2016, Charlotte, North Carolina
ICONE24-60960
OUTLINE OF SPECIFICATION FOR COMPOSITE SC WALLS IN NUCLEAR FACILITIES Saahastaranshu R. Bhardwaj Purdue University West Lafayette, IN, USA
[email protected]
Amit H. Varma Purdue University West Lafayette, IN, USA
[email protected]
Taha Al-Shawaf AREVA Inc. Naperville, IL, USA
[email protected] ABSTRACT Appendix N9 to AISC N690s1 presents the design provisions for steel-plate composite (SC) walls in safety related nuclear facilities. AISC N690s1 is Supplement No. 1 to AISC N690-12 specification for safety related steel structures in nuclear facilities and was published in October 2015. This paper discusses the outline of Appendix N9 as well as how the appendix can be used for the design of SC wall structures. Appendix N9 establishes the minimum requirements that SC walls need to meet in order for the specification to be applicable. The requirements include minimum and maximum wall thickness and steel reinforcement ratio. Detailing requirements for SC wall panel sections are also discussed. The faceplate slenderness requirement to prevent the limit state of buckling before yielding is provided. Steel anchor requirements are based on developing adequate composite action, and preventing interfacial shear failure. Requirements for tie bars connecting the steel plates (faceplates) are provided to prevent splitting failure and out-of-plane shear failure. The detailing and design provisions for regions around openings in SC walls are also included. Appendix N9 provides a method of checking the design of SC walls for impactive and impulsive loads. A discussion of the analysis requirements for SC walls is presented. The provisions include effective stiffnesses, accident thermal loading and model parameters for analysis. The design strength equations for axial tension, axial compression, out-of-plane shear, out-of-plane flexure, in-plane shear, and for combined in-plane forces and out-of-plane moment demands are parts of the provisions of the appendix. The provisions also include interaction equations for evaluating tie bars resisting demands due to combination of out-of-plane and
interfacial shear forces. Performance requirements for the anchorage of SC walls to concrete basemat, SC wall-to-wall connections and SC walls to floor slab connections are given in the appendix. The provisions also include requirements for fabrication, inspection, and quality control of SC walls constructed for safety-related nuclear facilities. INTRODUCTION Modular SC construction consists of composite concrete walls. Each wall consists of two faceplates that are anchored to concrete using steel anchors. The faceplates are connected to each other using tie bars. There are no reinforcing bars such as in regular reinforced concrete (RC) buildings. Modular SC construction reduces the project schedule and labor requirements significantly. Faceplates eliminate the requirement of external formwork and reduce congestion in comparison to RC walls by acting as equivalent reinforcement. A typical SC wall section is shown in Figure 1. The lack of a US based design code for SC construction was a major impediment in the adoption of SC construction in US. American Institute of Steel Construction (AISC) formed a subcommittee in 2006 to develop a specification for design of modular SC walls in safety-related nuclear facilities. Over the last nine years, the committee has worked to finalize this specification as an appendix in AISC N690-12 [1]. This appendix (Appendix N9) has been issued as a part of N690s1 [2], which is Supplement No. 1 to AISC N690-12.
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FIGURE 1. TYPICAL SC WALL SECTION [1]
N9.1.1 General Provisions: An SC section needs to satisfy these requirements in order for the provisions to be applicable. These provisions include upper and lower limits for SC wall thickness (tsc), reinforcement ratio (ρ), and material strengths. SC behavior requirements (e.g., ensuring composite action) that need to be satisfied are mentioned in this subsection.. Provisions for steel ribs and splices are also provided in this sub-section. In case any of these provisions is not satisfied, the appendix is not applicable. However, the commentary to the appendix does provide alternate design methodologies for cases where the appendix is not applicable.
Appendix N9 is applicable to the design of SC walls and their connections and anchorages. The experimental database that forms the basis of the provisions is discussed in the commentary to Appendix N9. The appendix is limited to SC walls with two faceplates on exterior surfaces and no additional reinforcing bars. General requirements of the appendix specify the conditions necessary for applicability of the provisions. SC wall section detailing requirements address SC specific limit states of local buckling, interfacial shear failure and section delamination. This paper discusses the organization of the appendix and briefly mentions its provisions. Additionally, the paper aims to facilitate the usage of the appendix by presenting a flowchart. The design procedure for SC walls using Appendix N9 is discussed by means of the flowchart.
N9.1.2 Design Basis: This sub-section provides provisions for dividing the SC walls (for design purposes) into interior regions and connection regions, determination of required strength and considering second-order effects of structures.
LAYOUT AND ORGANIZATION OF APPENDIX N9 Appendix N9 is organized into four major sections. These sections are further organized into sub-sections. The sections and sub-sections of the Appendix are discussed below.
N9.1.3. Faceplate Slenderness Requirement: The provisions of this sub-section limit the spacing of ties and steel anchors to ensure the SC specific limit state of faceplate buckling does not occur before faceplate yielding. The requirement is based upon experimental database and is discussed in the commentary to Appendix 9 based on Zhang et al. [3]
N9.1 Design Requirements This section provides limits of SC parameters for which the provisions of the appendix are applicable. It discusses the design basis and the detailing requirements governed by SC specific limit states. The design and detailing requirements are based on experimental database, or mechanics. The basis of these requirements, and relevant research literature are discussed in the commentary to Appendix N9. The sub-sections under design requirements are as follow.
N9.1.4. Requirements for Composite Action: This subsection provides basis for classifying steel anchors as yielding or non-yielding shear connectors. It also limits the spacing of steel anchors to develop the yield strength of faceplates and prevent interfacial shear failure before out-of-plane shear failure as discussed in Zhang et al. [3].
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N9.1.5 Tie Requirements: This sub-section limits the spacing of tie bars, classifies ties as yielding or non-yielding shear reinforcement and provides the expression for minimum tensile strength of tie bars to prevent delamination failure of SC walls. The development of these requirements is explained in the commentary to the appendix.
N9.2.5 Determination of Required Strengths: The subsection provides limits of averaging of demands obtained from elastic finite element analysis. The required flexural, axial and shear strengths for SC panel sections are discussed briefly. N9.3
DESIGN OF SC WALLS This section provides expressions for determining the available strengths of SC panel sections for different demand types. Tensile strength contribution of concrete and contribution of steel ribs are ignored. The basis of expressions for available strengths for individual demand types is discussed in corresponding sections of the commentary.
N9.1.6 Design for Impactive and Impulsive Loads: The provisions for checking the design of SC walls for impactive and impulsive loads are presented in this sub-section. Permissible dynamic increase factors for materials, as well as ductility ratio demands for flexure controlled, shear controlled or axial compressive loads are given. Methodologies for determining the response of SC walls to impulsive loads are also discussed. The commentary to the appendix discusses rational methods of design for impactive loading [4, 5].
N9.3.1 Uniaxial Tensile Strength: This sub-section refers Chapter D of specification for structural steel buildings, AISC 360 [8]. The provisions ensure than faceplates yield before rupturing.
N9.1.7 Design and Detailing around Openings: The section classifies openings in SC walls as small or large openings. For each type of opening, design and detailing provisions are provided to either consider the opening with free edge or consider the opening edge as fully developed. The treatment of a bank of small openings is also discussed.
N9.3.2 Compressive Strength: The provisions to determine compressive strength of SC panel sections refer to Section I2.1b of AISC 360, with faceplates replacing the steel shape. The definitions mentioned in this section replace those in AISC 360. The compressive strength of SC wall panel is discussed in detail in the commentary based on Zhang et al. [3].
N9.2
ANALYSIS REQUIREMENTS This section provides the parameters for analysis of the SC wall for design loads. These include modeling parameters for the SC panel section, consideration of thermal loads and required strength determination. The commentary to the appendix discusses these requirements in detail based on Varma et al. [6]. . The sub-sections for analysis requirements are briefly discussed below
N9.3.3 Out-of-Plane Flexural Strength: The expression for design flexural strength of SC walls is based on limit state of yielding of faceplates. The flexural strength of SC wall panel is discussed in detail in the commentary based on Sener et al. [9]. N9.3.4 In-Plane Shear Strength: The provision for determining the design in-plane shear strength of SC walls corresponds to limit state of yielding of faceplates. The in-plane shear strength of SC wall panel is discussed in detail in the commentary based on Varma et al. [10] and Ozaki et al. [11].
N9.2.1 General Provisions: Parameters for analysis such as the type of finite elements to be used, damping ratio to be used for seismic analysis, second order effects and accident thermal loads are discussed in this sub-section.
N9.3.5 Out-of-Plane Shear Strength: The out-of-plane shear strength of SC panel sections is determined by project-specific large scale tests, applicable test results or the provisions of this section. The available strength has contributions from steel and concrete and depends on the spacing between the shear reinforcement and type of shear reinforcement (yielding or nonyielding type). The out-of-plane shear strength of SC wall panel is discussed in detail in the commentary based on Sener & Varma [12].
N9.2.2 Effective Stiffness for Analysis: Determination of effective flexural and shear stiffness by taking into consideration cracking of concrete due to accident thermal conditions. The effect of concrete cracking due to accident thermal is discussed in detail in the commentary based on Booth et al. [7]. N9.2.3 Geometric and Material Properties for Finite Element Analysis: Geometric and material properties of the equivalent elastic finite element are defined in this sub-section. These include poisson’s ratio, thermal expansion coefficient, thermal conductivity, model section thickness, material elastic modulus, material density and material specific heat.
N9.3.6 Strength under Combined Forces: This section provides expressions to limit the interaction of out-of-plane shear and interfacial shear forces. For interaction of in-plane forces and out-of-plane moments, interaction equations are provided in principal stress space. Alternatively, the interaction of these forces and moments can also be checked using the inplane membrane forces directly. The interaction of in-plane forces and out-of-plane moments of an SC wall panel is discussed in detail in the commentary based on Varma et al. [13].
N9.2.4 Analyses Involving Accident Thermal Conditions: This sub-section outlines the procedure for performing accident thermal analysis. The results from heat transfer analysis serve as input loads for structural analysis.
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NB3. DESIGN BASIS A reference to Appendix N9 has been added in the main text for design of SC walls for impactive and impulsive loads.
N9.3.7 Strength of Composite Linear Members in Combination with SC walls: Linear composite members can be used with SC walls. The design has to be as per Chapter I of AISC 360 [8]. N9.4 DESIGN OF SC WALL CONNECTIONS This section specifies the types of SC connections possible and addresses the design requirements for these connection types. Connection design philosophy and required and available strengths of the connections are presented in this section.
NM2. FABRICATION AND CONSTRUCTION Provision for welding of SC wall elements to ASME Class MC components have been added. Dimensional tolerances for SC walls during fabrication, fit up, erection of modules, before concrete placement and after concrete curing have been provided in this section.
N9.4.1 General Provisions: The provisions of this subsection discuss when a connection is to be treated as fixed or pinned. Permissible connector types are also discussed. The section also establishes permissible force transfer mechanisms.
NN6. MINIMUM REQUIREMENTS FOR INSPECTION OF COMPOSITE CONSTRUCTION Inspection requirements for SC walls before and after concrete placement have been provided in this section.
N9.4.2 Required Strength: The required strength of the connection is based on the connection design philosophy. The required strength of connections is determined as: a) 125% of the smaller of the corresponding nominal strengths of the connected parts or, b) 200% of the required strength due to seismic loads plus 100% of the required strength due to non-seismic loads (including thermal loads).
DESIGN OF SC WALLS USING APPENDIX N9 In order to facilitate the use of Appendix N9, a flowchart has been provided in the commentary to Appendix N9. The flowchart has been reproduced in Figure 2 and Figure 3, and discussed briefly below. In order to design an SC wall structure using Appendix N9, the designer needs to first ensure that the SC wall parameters comply with the requirements of Section N9.1.1. Once these requirements are met, faceplate slenderness requirements of Section N9.1.3 are checked. Steel anchor and tie bar detailing requirements of Sections N9.1.4 and N9.1.5 are then checked. For determining the demands for the SC wall, analysis is performed based on provisions of Section N9.2. The required strengths are compared with available strengths determined per the provisions of Section N9.3. SC wall connections are designed per Section N9.4. The design of SC wall is then checked for impactive and impulsive loads per Section N9.1.6. The detailing and fabrication tolerances for SC walls are specified as per Sections N9.1.7 and Chapter NM of AISC N690. The quality assurance and control of the constructed SC wall is as per Chapter NN of AISC N690.
N9.4.3 Available Strength: This sub-section references the applicable provisions for determining the available connector strength for different types of connectors. ADDITIONS TO N690-12 In order to incorporate Appendix N9 into AISC N690, additions or updates have been made to some chapters of N69012. These modifications are briefly discussed in this section. NA2. REFERENCED SPECIFICATIONS, CODES AND STANDARDS American Concrete Institute (ACI), American Society of Mechanical Engineers (ASME) and ASTM International (ASTM) specifications cited in Appendix N9 have been added to this section.
SUMMARY This paper presented the outline and organization of the specification for deign of modular steel plate composite (SC) construction. The publication of the Supplement No. 1 to N69012 provides an ANSI standard for design and construction of SC wall structures. This specification is a valuable tool in the implementation of modular composite construction in nuclear facilities. AISC is currently in the process of developing a design guide to further enable the use of this specification. This design guide will explore the provisions of this specification in detail and discuss different possible design methodologies.
NA3. MATERIAL ASTM materials cited in Appendix N9 have been added to this section. NB2. LOADS AND LOAD COMBINATIONS This section contains the updated load combinations to consider fluid and soil loads. Load factors for some loads have also been updated based on RG1.142 [14]
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Begin design of structure with SC walls
1.
Check that SC section thickness, reinforcement ratio, faceplate thickness, and steel and concrete grades satisfy the limitations of Section N9.1.1. 2. Check that applicable requirements of Section N9.1.1 are satisfied.
Are the requirements of N9.1.1 satisfied?
No
Appendix N9 is not applicable.
Yes Check that faceplate is nonslender (Section N9.1.3)
Provide composite action using steel anchors. Classify connectors as yielding or nonyielding type using Section N9.1.4a. Check spacing of steel anchors using Section N9.1.4b
Provide structural integrity using ties. Check tie spacing using Section N9.1.5. Check tie spacing in regions around openings using Section N9.1.7. Classify ties as yielding or nonyielding using Section N9.1.5a. Ties contribute to out-of-plane shear strength of SC walls according to Section N9.3.5 Calculate minimum required tension strength for ties using Section N9.1.5b. Develop elastic finite element (EFE) model according to Sections N9.2.1 and N9.2.3. Analyze EFE model for load and load combinations from Section NB2. 1. Model openings using Section N9.1.7. 2. Model flexural and shear stiffness of SC walls using Section N9.2.2. 3. Loading due to accident thermal conditions will be as per Section N9.2.4. 4. Model second-order effects using Section N9.1.2b.
5.
Talk
Continued in Figure 3
FIGURE 2. FLOWCHART TO FACILITATE USE OF APPENDIX N9-PART 1 [2]
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Continued from Figure 2
Perform EFE analysis to calculate design demands and required strengths. Identify interior and connection regions using Section N9.1.2
1. 2.
1. 2. 3. 4.
Design Process for SC Walls: Required strengths ≤ Available strengths Calculate required strengths for each demand type using Section N9.2.5 Calculate available strengths for each demand type using Section N9.3. The sub-sections are: a) Available uniaxial tensile strength using Section N9.3.1 b) Available compressive strength using Section N9.3.2 c) Available out-of-plane flexural strength using Section N9.3.3 d) Available in-plane shear strength using Section N9.3.4 e) Available out-of-plane shear strength using Section N9.3.5 f) Check available strength for combined forces using Section N9.3.6 1. Combined out-of-plane shear demands using Section N9.3.6a 2. Combined in-plane membrane forces and out-of-plane moments using Section N9.3.6b Design Process for SC Wall Connections Select connection design philosophy and design force transfer mechanisms for connections as per Section N9.4.1. Calculate connection required strength in accordance with Section N9.4.2 Calculate connection available strength using Section N9.4.3 Check connection required strength ≤ connection available strength
Check SC wall design for impactive and impulsive loads in accordance with Section N9.1.6
1. 2.
Fabrication, Erection and Construction Requirements Specify detailing for regions around openings using Section N9.1.7 Specify dimensional tolerances for fabrication of SC wall panels, sub-modules, and modules using Chapter NM
Specify quality assurance/quality control requirements for SC walls in accordance with Chapter NN
End design of structure with SC walls
FIGURE 3. FLOWCHART TO FACILITATE USE OF APPENDIX N9-PART 2 [2]
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[9] Sener, K., Varma, A.H., and Ayhan, D., 2015, “SteelPlate Composite SC Walls: Out-of-Plane Flexural Behavior, Database, and Design.” Journal of Constructional Steel Research, Elsevier Science, Volume 108, May 2015, pp. 46–59 http://dx.doi.org/10.1016/j.jcsr.2015.02.002 [10] Varma, A.H., Zhang, K., Chi, H., Booth, P.N., and Baker, T., 2011, “In-Plane Shear Behavior of SC Composite Walls: Theory vs. Experiment.” Transactions of the 21st International Conference on Structural Mechanics in Reactor Technology (SMiRT 21), New Delhi, India, Paper ID 764, North Carolina State University, Raleigh, NC, pp.1-10. http://engineering.purdue.edu/~ahvarma/Publications/p764.pdf [11] Ozaki, M., Akita, S., Oosuga, H., Nakayama, T. and Adachi, N., 2004, “Study on Steel Plate Reinforced Concrete Panels Subjected to Cyclic In-Plane Shear,” Nuclear Engineering and Design, Vol. 228, pp. 225244. [12] Sener, K.C. and Varma, A.H., 2014, “Steel-Plate Composite Walls: Experimental Database and Design for Outof-Plane Shear,” Journal of Constructional Steel Research, Elsevier Science, Volume 100, pp. 197-210. http://dx.doi.org/10.1016/j.jcsr.2014.04.014 [13] Varma, A.H., Malushte, S.R., Sener, K.C. and Lai, Z., 2014, “Steel-Plate Composite (SC) Walls for Safety Related Nuclear Facilities: Design for In-Plane Forces and Out-of-Plane Moments,” Nuclear Engineering and Design, Special Issue on SMiRT-21 Conference, Elsevier Science, Volume 269, pp. 240249, http://dx.doi.org/10.1016/j.nucengdes.2013.09.019. [14] NRC, 2001, “Safety-Related Concrete Structures for Nuclear Power Plants (Other Than Reactor Vessels and Containments),” Regulatory Guide 1.142, U.S. Nuclear Regulatory Commission, Washington, DC.
REFERENCES [1] ANSI/AISC N690, 2012, “Specification for SafetyRelated Steel Structures for Nuclear Facilities”, American Institute of Steel Construction, Chicago, IL. [2] ANSI/AISC N690s1, 2015, “Specification for SafetyRelated Steel Structures for Nuclear Facilities Supplement No. 1”, American Institute of Steel Construction, Chicago, IL. [3] Zhang, K., Varma, A.H., Malushte, S., and Gallocher, S., 2014, “Effects of Shear Connectors on the Local Buckling and Composite Action in Steel Concrete Composite Walls.” Nuclear Engineering and Design, Special Issue on SMiRT-21 Conference, Vol. 269, pp. 231-239, Elsevier Science. http://dx.doi.org/10.1016/j.nucengdes.2013.08.035 [4] Bruhl, J., and Varma, A.H., 2015, “Missile Impact Behavior and Design of Composite SC Walls.” International Journal of Impact Engineering, Elsevier Science, Vol. 75, pp. 7587, http://dx.doi.org/10.1016/j.ijimpeng.2014.07.015. [5] Bruhl, J. C., Varma, A. H., and Kim, J. M., 2015, “Static Resistance Function for SC Walls Subjected to Missile Impact.” Nuclear Engineering and Design, Special Issue of SMiRT-22 in San Francisco: Improving Safety and Reliability of Nuclear Energy, Elsevier Science, Vol. 295,pp. 843–859 http://dx.doi.org/10.1016/j.nucengdes.2015.07.037 [6] Varma, A.H., Malushte, S.R., Sener, K., Booth, P.N., 2012, “Analysis Recommendations for Steel-Composite Walls for Safety-Related Nuclear Facilities.” Proceedings of the ASCE Structures Congress, Proceedings, ASCE, Reston, VA, pp. 18711880. http://dx.doi.org/10.1061/9780784412367.164 [7] Booth, P.N., Varma, A.H., Malushte, S., and Johnson, W., 2007, “Response of Modular Composite Walls to Combined Thermal & Mechanical Load,” Transactions of the 19th International Conference on Structural Mechanics in Reactor Technology (SMiRT-19), Paper # H01/4, Toronto, Canada, IASMIRT, North Carolina State University, Rayleigh, NC, pp. 18,http://www.iasmirt.org/transactions/19/H01_4.pdf [8] AISC 360, 2010, “Specification for Structural Steel Buildings”, American Institute of Steel Construction, Chicago, IL.
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