| = 4.4 — Structural system and load paths | |
| == 4.4.1 The structural system shall include (a) through (g), | |
| as applicable: | |
| (a) Floor construction and roof construction, including | |
| (b) Beams and joists | |
| (c) Columns | |
| (d) Walls | |
| (e) Diaphragms | |
| (f) Foundations | |
| (g) Joints, connections, and anchors as required to transmit | |
| forces from one component to another | |
| == 4.4.2 Design of structural members including joints and | |
| connections given in 4.4.1 shall be in accordance with | |
| Chapters 7. through 18. | |
| == 4.4.3 It shall be permitted to design a structural system | |
| comprising structural members not in accordance with 4.4.1 | |
| and 4.4.2, provided the structural system is approved in | |
| accordance with 1.10.1. | |
| == 4.4.4 The structural system shall be designed to resist the | |
| factored loads in load combinations given in 4.3 without | |
| exceeding the appropriate member design strengths, considering | |
| one or more continuous load paths from the point of | |
| load application or origination to the final point of resistance. | |
| == 4.4.5 Structural systems shall be designed to accommodate | |
| anticipated volume change and differential settlement. | |
| = R4.4 — Structural system and load paths | |
| == R4.4.1 Structural concrete design has evolved from | |
| emphasizing the design of individual members to designing | |
| the structure as an entire system. A structural system | |
| consists of structural members, joints, and connections, each | |
| performing a specific role or function. A structural member | |
| may belong to one or more structural systems, serving | |
| different roles in each system and having to meet all the | |
| detailing requirements of the structural systems of which | |
| they are a part. Joints and connections are locations common | |
| to intersecting members or are items used to connect one | |
| member to another, but the distinction between members, | |
| joints, and connections can depend on how the structure | |
| is idealized. Throughout this chapter, the term “members” | |
| often refers to “structural members, joints, and connections.” | |
| Although the Code is written considering that a structural | |
| system comprises these members, many alternative arrangements | |
| are possible because not all structural member types | |
| are used in all building structural systems. The selection types | |
| of the members to use in a specific project and the role or | |
| roles these member types play is made by the licensed design | |
| professional complying with requirements of the Code. | |
| == R4.4.2 In the chapter for each type of structural member, | |
| requirements follow the same general sequence and scope, | |
| including general requirements, design limits, required | |
| strength, design strength, reinforcement limits, reinforcement | |
| detailing, and other requirements unique to the type | |
| of member. | |
| == R4.4.3 Some materials, structural members, or systems | |
| that may not be recognized in the prescriptive provisions of | |
| the Code may still be acceptable if they meet the intent of the | |
| Code. Section 1.10.1 outlines the procedures for obtaining | |
| approval of alternative materials and systems. | |
| == R4.4.4 The design should be based on members and | |
| connections that provide design strengths not less than the | |
| strengths required to transfer the loads along the load path. | |
| The licensed design professional may need to study one | |
| or more alternative paths to identify weak links along the | |
| sequence of elements that constitute each load path. | |
| == R4.4.5 The effects of column and wall creep and | |
| shrinkage, restraint of creep and shrinkage in long roof and | |
| floor systems, creep caused by prestress forces, volume | |
| changes caused by temperature variation, as well as potential | |
| damage to supporting members caused by these volume | |
| changes should be considered in design. Reinforcement, | |
| closure strips, or expansion joints are common ways of | |
| accommodating these effects. Minimum shrinkage and | |
| temperature reinforcement controls cracking to an acceptable | |
| level in many concrete structures of ordinary proportions | |
| and exposures. | |
| Differential settlement or heave may be an important | |
| consideration in design. Geotechnical recommendations to | |
| allow for nominal values of differential settlement and heave | |
| are not normally included in design load combinations for | |
| ordinary building structures. | |
| American Concrete Institute – Copyrighted © Material – www.concrete.org | |
| 52 ACI 318-19: BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE | |
| No further reproduction or distribution is permitted. | |
| == 4.4.6 Seismic-force-resisting system | |
| === 4.4.6.1 Every structure shall be assigned to a Seismic | |
| Design Category in accordance with the general building | |
| code or as determined by the building official in areas | |
| without a legally adopted building code. | |
| === 4.4.6.2 Structural systems designated as part of the | |
| seismic-force-resisting system shall be restricted to those | |
| systems designated by the general building code or as determined | |
| by the building official in areas without a legally | |
| adopted building code. | |
| === 4.4.6.3 Structural systems assigned to Seismic Design | |
| Category A shall satisfy the applicable requirements of this | |
| Code. Structures assigned to Seismic Design Category A are | |
| not required to be designed in accordance with Chapter 18. | |
| === 4.4.6.4 Structural systems assigned to Seismic Design | |
| Category B, C, D, E, or F shall satisfy the requirements of | |
| Chapter 18 in addition to applicable requirements of other | |
| chapters of this Code. | |
| === 4.4.6.5 Structural members assumed not to be part of the | |
| seismic-force-resisting system shall be permitted, subject to | |
| the requirements of 4.4.6.5.1 and 4.4.6.5.2. | |
| ==== 4.4.6.5.1 In structures assigned to Seismic Design Category | |
| B, C, D, E, or F, the effects of those structural members | |
| on the response of the system shall be considered and accommodated | |
| in the structural design. | |
| ==== 4.4.6.5.2 In structures assigned to Seismic Design Category | |
| B, C, D, E, or F, the consequences of damage to those | |
| structural members shall be considered. | |
| ==== 4.4.6.5.3 In structures assigned to Seismic Design Category | |
| D, E, or F, structural members not considered part of | |
| the seismic-force-resisting system shall meet the applicable | |
| requirements in Chapter 18. | |
| == R4.4.6 Seismic-force-resisting system | |
| === R4.4.6.1 Design requirements in the Code are based on the | |
| seismic design category to which the structure is assigned. In | |
| general, the seismic design category relates to seismic risk | |
| level, soil type, occupancy, and building use. Assignment of | |
| a building to a seismic design category is under the jurisdiction | |
| of a general building code rather than this Code. In the | |
| absence of a general building code, ASCE/SEI 7 provides | |
| the assignment of a building to a seismic design category. | |
| === R4.4.6.2 The general building code prescribes, through | |
| ASCE/SEI 7, the types of structural systems permitted as part | |
| of the seismic-force-resisting system based on considerations | |
| such as seismic design category and building height. The | |
| seismic design requirements for systems assigned to Seismic | |
| Design Categories B through F are prescribed in Chapter 18. | |
| Other systems can be used if approved by the building official. | |
| === R4.4.6.3 Structures assigned to Seismic Design Category | |
| A are subject to the lowest seismic hazard. Chapter 18 does | |
| not apply. | |
| === R4.4.6.4 Chapter 18 contains provisions that are applicable | |
| depending on the seismic design category and on | |
| the seismic-force-resisting system used. Not all structural | |
| member types have specific requirements in all seismic | |
| design categories. For example, Chapter 18 does not include | |
| requirements for structural walls in Seismic Design Categories | |
| B and C, but does include special provisions for Seismic | |
| Design Categories D, E, and F. | |
| === R4.4.6.5 In Seismic Design Categories D, E, and F, structural | |
| members not considered part of the seismic-forceresisting | |
| system are required to be designed to accommodate | |
| drifts and forces that occur as the building responds to an | |
| earthquake. | |
| American Concrete Institute – Copyrighted © Material – www.concrete.org | |
| PART 1: GENERAL 53 | |
| 4 Struct. Systems | |
| No further reproduction or distribution is permitted. | |
| === 4.4.6.6 Effects of nonstructural members shall be | |
| accounted for as described in 18.2.2.1 and consequences of | |
| damage to nonstructural members shall be considered. | |
| === 4.4.6.7 Design verification of earthquake-resistant | |
| concrete structures using nonlinear response history analysis | |
| shall be in accordance with Appendix A. | |
| == 4.4.7 Diaphragms | |
| === 4.4.7.1 Diaphragms, such as floor or roof slabs, shall be | |
| designed to resist simultaneously both out-of-plane gravity | |
| loads and in-plane lateral forces in load combinations given | |
| in 4.3. | |
| === 4.4.7.2 Diaphragms and their connections to framing | |
| members shall be designed to transfer forces between the | |
| diaphragm and framing members. | |
| === 4.4.7.3 Diaphragms and their connections shall be | |
| designed to provide lateral support to vertical, horizontal, | |
| and inclined elements. | |
| === 4.4.7.4 Diaphragms shall be designed to resist applicable | |
| lateral loads from soil and hydrostatic pressure and other | |
| loads assigned to the diaphragm by structural analysis. | |
| === 4.4.7.5 Collectors shall be provided where required to | |
| transmit forces between diaphragms and vertical elements. | |
| === 4.4.7.6 Diaphragms that are part of the seismic-forceresisting | |
| system shall be designed for the applied forces. In | |
| structures assigned to Seismic Design Category D, E, and F, | |
| the diaphragm design shall be in accordance with Chapter 18. | |
| = 4.5 — Structural analysis | |
| == 4.5.1 Analytical procedures shall satisfy compatibility of | |
| deformations and equilibrium of forces. | |
| == 4.5.2 The methods of analysis given in Chapter 6 shall be | |
| permitted. | |
| === R4.4.6.6 Although the design of nonstructural elements for | |
| earthquake effects is not included in the scope of this Code, | |
| the potential negative effects of nonstructural elements on the | |
| structural behavior need to be considered in Seismic Design | |
| Categories B, C, D, E, and F. Interaction of nonstructural | |
| elements with the structural system—for example, the shortcolumn | |
| effect—had led to failure of structural members and | |
| collapse of some structures during earthquakes in the past. | |
| == R4.4.7 Diaphragms | |
| Floor and roof slabs play a dual role by simultaneously | |
| supporting gravity loads and transmitting lateral forces in | |
| their own plane as a diaphragm. General requirements for | |
| diaphragms are provided in Chapter _12, and roles of the | |
| diaphragm described in the Commentary to that chapter. | |
| Additional requirements for design of diaphragms in structures | |
| assigned to Seismic Design Categories D, E, and F are | |
| prescribed in Chapter 18. | |
| === R4.4.7.5 All structural systems must have a complete load | |
| path in accordance with 4.4.4. The load path includes collectors | |
| where required. | |
| [ Lanjut Ke 4.5—Structural analysis ... ] | |
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