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 Civil Engineering and Architecture © 2010 Project Lead The Way, Inc.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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. This design process was developed based on the University of Maryland - College Park - IRB Research Project Project Lead The Way, Inc. Copyright 2010

Architectural Program Introduction to Structural Design Architectural Program Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Defines the Problem Establishes overall concept and design philosophy Includes Location of building on site Architectural style Interior space planning Design elements Construction materials Building systems 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 based – it specifically defines the problem to be solved.   The architectural program is in essence a design brief for the design of the project. 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

Architectural Program Introduction to Structural Design Architectural Program 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. Additional criteria needed: Types and magnitudes of applied loads Load path that each load will follow to the ground 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. 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

Structural Design Process Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Generate Concepts 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

Structural Design Process Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Generate Concepts 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

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

Structural Design Process Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Construct and Test Prototype Create a model to represent your structural design Structural analysis software 3D architectural software Physical model Test model 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. In some special cases, physical models are created in order to perform structural tests – for example, an unusually shaped high rise may be modeled and tested in a wind tunnel to assess wind loads in its urban environment. 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. Structural analysis software can check the strength and stability of a structural system, including all of the individually designed structural elements. Be aware that even small changes in the structure or it’s environment 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 or are present or structural elements are changed. Project Lead The Way, Inc. Copyright 2010

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

Structural Design Process Introduction to Structural Design Civil Engineering and Architecture Unit 3 – Lesson 3.2– Structures Structural Design Process Present the Solution If the proposed design solves the problem Document the project Create working drawings and specifications for the structural design Communicate the project Project Lead The Way, Inc. Copyright 2010

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