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Introduction to Structural Design

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Presentation on theme: "Introduction to Structural Design"— Presentation transcript:

1 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Introduction to Structural Design Architecture has recorded the great ideas of the human race. Not only every religious symbol, but every human thought has its page in that vast book Victor Hugo Project Lead The Way, Inc. Copyright 2010

2 Structure of a Building
Introduction to Structural Design Structure of a Building Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures The primary function of a building structure is to support and transmit the building loads and forces to the ground. Photos courtesy Tilt-up Concrete Association Project Lead The Way, Inc. Copyright 2010

3 Characteristics of a Structure
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Characteristics of a Structure Strength Stability Economic Value Strength is the capacity of a structure to carry the loads applied to it. Stability means the structure can maintain its shape when loads or forces are applied. Loads and disturbances to the structure should not produce large movements or failure. The economic value or cost effectiveness of the structural design depends on choices made regarding how the structure will carry loads, the structural systems used, and the materials chosen. Project Lead The Way, Inc. Copyright 2010

4 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural System Made up of many smaller structural sub-systems that work together to provide a strong, stable, and cost-effective structure. Examples of these smaller structural sub-systems include: Roof Framing Walls Foundations Floors Structural engineers design these structural systems. Project Lead The Way, Inc. Copyright 2010

5 Structural Sub-System
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Sub-System Made up of many structural elements that work together to provide a strong, stable, and cost-effective system. Basic structural elements include: Beam Arch Column Vault Truss Dome Structural engineers design these structural systems. Project Lead The Way, Inc. Copyright 2010

6 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Forces and Loads A force is any action that causes a change in the shape or motion of an object. A load is a force that is supported by a structural element. The terms force and load are often used interchangeably. Each structural element is subjected to at least one type of load. Loads include people, furniture, equipment, wind, snow, earthquakes, floods, and soil pressure. SNOW WIND Project Lead The Way, Inc. Copyright 2010

7 Structural Member Forces
Introduction to Structural Design Structural Member Forces Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Tension – A force that stretches or pulls apart a member, resulting in the member elongating. Compression – A force that squeezes or presses a member together, resulting in the member shortening. Shear – A force that acts perpendicular to the axis of the member, causing the internal particles of the member to slide against each other. The loads applied impose member forces in the structural elements. Three types of force that we will analyze in structural elements are tension, compression, and shear. Project Lead The Way, Inc. Copyright 2010

8 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Beam A structural element that carries a load that is applied transverse (perpendicular) to its length. Usually a horizontal member that carries a vertical applied load. The top fibers of a beam are in compression; the bottom fibers are in tension. Many structural members within a structure are technically beams but are called something else. For example, joists, girders, and elevated slabs act as beams. Project Lead The Way, Inc. Copyright 2010

9 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Cantilever Beam A special type of beam that is supported only at one end The top fibers of the cantilever are in tension; the bottom fibers are in compression Project Lead The Way, Inc. Copyright 2010

10 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Column A vertical structural element that carries an axial force in compression An axial force is a force along the length of the member. COLUMN Project Lead The Way, Inc. Copyright 2010

11 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Truss A structural element that is composed of smaller structural members typically configured in triangular arrangements Some truss members carry a tension force; others carry a compression force Project Lead The Way, Inc. Copyright 2010

12 Introduction to Structural Design
Arch Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures A curved structural element that spans over an open space In stone arches, the last stone to be placed at the top is called the keystone KEYSTONE Project Lead The Way, Inc. Copyright 2010

13 Introduction to Structural Design
Vault Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures A continuous arch that forms a ceiling or roof Project Lead The Way, Inc. Copyright 2010

14 Introduction to Structural Design
Dome Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures A structural element that is made up of arches that radiate around a center point to create a half sphere Project Lead The Way, Inc. Copyright 2010

15 Introduction to Structural Design
Hybrid Forms Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures An infinite number of combinations of these forms exist A space frame combines a 3D truss in the form of a dome. [click] This structure combines curved beams with metal roofing to form a vault. Project Lead The Way, Inc. Copyright 2010

16 Introduction to Structural Design
Design Process Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures The same design process used by engineers and designers in other disciplines can be used to design structural systems. Each structural element – each beam, each column, each truss – must be individually designed to carry the applied loads. Architects and engineers use an iterative design process to define, analyze, and solve the problem of creating a strong, stable, and cost-effective structure. The same process used by engineers in other disciplines can be applied to the design of structures. Remember that a design process is never linear. If at any time you discover new information (or new constraints are placed on the design, or you come up with a better idea), you may need to return to an earlier step to incorporate the new information. Project Lead The Way, Inc. Copyright 2010

17 Architectural Program
Introduction to Structural Design Architectural Program Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Establishes overall concept and design philosophy Includes Location of building on site Architectural style Interior space planning Design elements Construction materials Building systems Encompasses the first four steps of the design process For most commercial projects, an architectural program is created by an architect or by a design team that may include many design professionals. The architectural program is the foundation on which the design of the building is defined.  This program establishes the overall concept, philosophy, and design approach for the building.  The specific building design problem is established. Ideas for the building are brainstormed. Research is performed on existing building solutions and new technologies that can inform the decisions for this project. The specific criteria and constraints for the building are defined. The architectural program is in essence a design brief for the design of the project and typically includes preliminary drawings. This architectural program is shared with other professionals involved with the design, including the structural engineer, who will design the structural system to support the building design. Project Lead The Way, Inc. Copyright 2010

18 Structural Design Process
Introduction to Structural Design Structural Design Process Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures An architectural program establishes preliminary structural systems. The structural engineer must analyze the structural systems and provide a strong, stable, and cost-effective design. The architectural program typically identifies the general structural system(s) that will be used to support the building. For instance, the architectural program will establish the types of walls, floors, roof, and often the structural frame of the building. The structural engineer has the responsibility of designing the specific elements of the system(s) to safely and effectively support the building and the loads that will be applied to the building. Project Lead The Way, Inc. Copyright 2010

19 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Identify Criteria and Constraints Additional criteria needed: Types and magnitudes of applied loads Load path that each load will follow to the ground Once the architectural program is established, a structural engineer must further define the loading criteria for the structure. The structural engineer must know exactly what types and magnitudes of loads to consider in the design of the structure and how each load will be carried and transferred through the structure to eventually be resisted by the ground. Project Lead The Way, Inc. Copyright 2010

20 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Explore Possibilities Consider alternate structural configurations, materials, and spacing to improve the design or reduce costs Once the loading to each structural member has been established, options to resist the loads can be explored. For instance, you may want to explore the possibility of using both hollow core precast panels and composite concrete floors. If structural steel floor framing is to be used, you may want to consider both open web steel joists and structural steel I-beams. There is the opportunity to adjust spacing of structural members such as floor joists and columns if necessary to improve the design or reduce costs. Project Lead The Way, Inc. Copyright 2010

21 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Select an Approach Based on structural performance, compatibility with the architectural program, and cost Based on the possibilities explored, select the optimal design A design must be selected for every structural element in the structural system. Project Lead The Way, Inc. Copyright 2010

22 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Develop a Design Proposal Create a preliminary structural design incorporating the selections for all structural elements A design must be selected for every structural element in the structural system. Project Lead The Way, Inc. Copyright 2010

23 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Model or Prototype Create a model to represent your structural design Sketches Structural analysis software 3D architectural software For structural designs, prototypes are not often practical. However, structures are very often modeled in structural analysis software and/or 3D architectural programs to check structural behavior and compatibility with other building systems. Project Lead The Way, Inc. Copyright 2010

24 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Test and Evaluate Reanalyze structure based on element selections Structural analysis software 3D architectural software Simply choosing a structural element slightly different from that originally assumed may change the loading conditions and affect the structural performance of an element. Therefore, you should always reanalyze each design to ensure its strength and stability if new conditions are present. For example, assume that you choose joists that weigh 20 lb/ft of the member for the preliminary analysis of a floor system. However, that preliminary member did not provide adequate strength to carry the applied loads. You therefore revise your selection and choose a member that weighs 25 lb/ft. The increased weight will affect the design, and the member should be reanalyzed to make sure it can carry the additional weight. Structural analysis software can check the strength and stability of a structural system, including all of the individually designed structural elements. 3D architectural models can include many building systems and equipment such as mechanical (HVAC), electrical, and plumbing systems. If all of the systems are included in one model, interferences can be identified and corrected before construction. Project Lead The Way, Inc. Copyright 2010

25 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Refine Revise the design as necessary to correct problems with strength, stability, and compatibility with other systems Project Lead The Way, Inc. Copyright 2010

26 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Create or Make Based on the final design after revisions Create working drawings of the structural design Project Lead The Way, Inc. Copyright 2010

27 Structural Design Process
Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Communicate Results Distribute the drawings Include in bid package Include in construction drawings Project Lead The Way, Inc. Copyright 2010

28 Introduction to Structural Design
Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Image Sources Tilt-up Concrete Association (www.tilt-up.org) Project Lead The Way, Inc. Copyright 2010


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