OBJ 3.2B Structural Choices Flashcards
Choose systems with simple floor and roof framing that are fabricated mostly on-site
Which structural system do you choose if you have a highly irregular form? (4)
- Sitecast concrete using any slab system without beams or ribs, 2. Light Gauge Steel Framing 3. Platform frame 4. Masonry construction with either concrete slab or wood light floor framing
Expose the structure while retaining a high fire resistance rating (3)
- All concrete systems (although ribbed systems may require added thickness in the ribs or slab, or applied fireproofing) 2. Heavy timber frame 3. Mill construction
Use systems that do not include beams or joists in the floor and roof structure
Allow column placements that deviate from a regular grid (2)
- Sitecast concrete two-way flat plate or flat slab, 2. Metal Space frame
Thinnest floor systems are concrete slabs without ribs, preferably prestressed
Minimize floor thickness (3)
- Sitecast concrete two-way flat plate or flat slab, especially when post tensioned 2. Precast prestressed hollow core or solid slab 3 Post tensioned one-way solid slab
Long span structural systems:
Minimize the area occupied by columns or bearing walls (9)
- Heavy wood trusses 2. Glue-laminated wood beams 3. Glue-laminated wood arches 4. Steel frame 5. Open-web steel joists 6. Single-story rigid steel frame 7. Steel trusses 8. Sitecast concrete one-way joist or waffle slab, particularly when post-tensioned 9. Precast concrete single or double tees Specialty type: Specially fabricated steel beams, suspended systems, arches, vaults, and shells
Consider short-span one-way systems that permit easy structural modification
Allow for changes in the building over time
- Light gauge or conventional steel frame 2. Any wood system 3. Sitecast concrete one-way solid slab or one-way joist construction, excluding posttensioned 4. Precast concrete solid or hollow core slabs
System that doesn’t depend on on-site processes and that can be erected quickly
Permit construction under adverse weather conditions
- Any steel system 2. Any wood system 3. Precast concrete systems, particularly those that minimize the use of sitecast concrete toppings and grouting
Choose column and beam systems supported on point footings, thereby minimizing excavation/Choose systems that rely on a high degree of off-site prefabrication to minimize construction activities on site
Minimize site disturbance
: 1. Heavy timber 2. Steel frame Choose longspan systems that minimize bearing elements, such as: 3. heavy wood trusses 4. glue-laminated wood beams 5. glue-laminated wood arches 6. open-web steel joists 7. steel trusses Choose systems that rely on a high degree of off-site prefabrication to minimize construction activities on site, such as: 8. single-story rigid frames 9. Any precast concrete system
Consider systems in which the building is constructed on-site from easily formed, relatively unprocessed materials
Minimize off-site fabrication time
- Any sitecast concrete system 2. Light gauge steel framing 3. Platform frame 4. Any masonry system
Consider systems using highly preprocessed, prefabricated, or modular components
Minimize on-site erection time
- Single-story rigid steel frame 2. Steel frame, particularly with hinge connections 3. Any precast concrete system 4. Heavy timber frame
Consider systems that are lightweight and easy to form, or prefabricated and easy to assemble, such as:
Minimize construction time for a one- or two-story building
- any steel system 2. Heavy timber frame 3. Platform frame
The absence of lead time for the prefab of components in sitecast concrete systems allows construction of the building to begin on-site at the earliest time
Minimize construction time for a 4- to 20-story building
- Precast concrete 2. Steel frame Once those above systems are prefabricated, on-site erection proceeds quickly. 3. Any sitecast concrete system The absence of lead time for the prefab of components in sitecast concrete systems allows construction of the building to begin on-site at the earliest time
System that is strong, lightweight, prefab, and easy to assemble:
Minimize construction time for a building 30 stories or more in height
- Steel frame 2. Precast and sitecast are economical alternatives to steel frame construction
capability of economically forming rigid joints
Avoid the need for diagonal bracing or shear walls
- Any sitecast concrete system, particularly those with beams, or deepened slabs around the columns 2. Steel frame with welded rigid connections 3. Single-story rigid steel frame When depending on a rigid frame for lateral stiffness, the sizes of the frame members often must be increased to resist the added bending stresses produced in such systems
Consider lightweight or short-span systems:
Minimize the dead load on a foundation
- Any steel system 2. Any wood system