Structure Engineering 101 For Mechanical Engineers

Class outline Structural systems IBC 2006 Seismic provisions Information your structural engineer needs Coordination Building Information Modeling

Structural Systems Foundations –Drilled piers and pier caps –Driven piles –Footings –Mat footings –Perimeter grade beams –Basement walls –Tie beams –Post-Tensioned slabs on grade

Drilled pier video Yes I know the video is side ways….I am just a structural engineer…

So what does a mechanical engineer need to know about a drilled pier? Underground coordination Top of pier elevation is critical Trenches and excavations next to piers undermine piers capacity Pier caps and tie beam coordination Electrical grounding Piers are bigger then shown on structural Piers are not the ideal place to put the geo-exchange system….

Driven piles

Electrical Grounding Driven Pile

Screw Piles

Mat Foundations

Foundation grade beam

How do foundation problems effect the mechanical engineer? Expansive soils Soil settlement Void forms Crawl spaces and molds

Void form

Foundation heave/ settlements

Structural Systems Steel Frame –Beams and columns –Gussets –Acoustical –Vibration

Slab thickness… see schedules and details Beam depth… see plan Camber… not to worry… Beam reactions… does not effect you Dimensions… not something a mechanical engineer uses…..

Steel Beam Sizes Link to steel section properties look up table: Commonly used steel beam sizes: SizeDepth (d)Width (bf) W10x1910”4” W10x3010”6” W12x2212”4” W12x3512”7” W14x2614”5” W14x3814”7” W14x5314”8” W16x3116”6” W16x5716.5”7” W18x4618”6” W18x7018.5”7 1/2” W21x5721”6 1/2” W21x6821”8 1/4” W24x6224”7” W24x8424”9” W27x9427”10” W30x9930”10 1/2” W33x13033”11 ½” W36x16036”12”

Cutting the metal deck……

Floor drains in the metal deck……

Hydronic Heating

Joists and joist Girders

Structural Systems Cast-in-place concrete frame –Wide beams center on columns Concrete slabs that generally can be readily sleeved for piping Mechanical shafts and chases Sleeves and floor sinks.. electrical conduits…

Structural Systems Cast-in-place concrete core walls –Avoid locating telecom and electrical rooms inside of closed in concrete core walls –Locate shafts at ends of cores –Coordination of openings Mechanical ducts Stair pressurization Piping sleeves Electrical conduits Fire house cabinets Recessed drinking fountains

Do you make site visits during structural construction? Ask to go along with your structural engineer sometime… It is a lot of fun…check this video out

Structural Systems Post-tensioned Cast-in-place concrete –Most common on Residential and Hotels –Flat thin slab –Highly stressed cables embedded in slab –Sleeves around columns are critical to design –Drilled in hanger inserts limited to about 1 inch in depth. –Pipe sleeves by columns

Structural Systems Precast concrete –Tee stems spaced at 4’-0” or 5’-0” and 6-inches wide at the top. –Field concrete topped and pre-topped tees (no electrical conduit in pre- topped tees) –Mechanically hang from tee flanges if hangers are drilled in inserts, do not drill stems. Pre-stress tendons are located in stems.

Light gage cold formed steel (Studs)

Masonry

Structural Systems-Wood

Roof mechanical stacks SMACNA provisions. Guyed stacks –Performance specifications »Wind loads »Anchoring locations and requirements »Tensioning load criteria

Roof mechanical stacks Large Tall Stacks….design and detail stacks and connections to structure or retain a structural engineer. Stack design is generally not a part of your structural engineers scope of service.

IBC 2006 SECTION 1613 EARTHQUAKE LOADS Scope. Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with ASCE 7, excluding Chapter 14 and Appendix 11A.

ASCE Chapter 13 SEISMIC DESIGN REQUIREMENTS FOR NONSTRUCTURAL COMPONENTS 13.1 GENERAL Scope. This chapter establishes minimum design criteria for nonstructural components that are permanently attached to structures and for their supports and attachments Seismic Design Category. For the purposes of this chapter, nonstructural components shall be assigned to the same seismic design category as the structure that they occupy or to which they are attached.

ASCE Component Importance Factor. All components shall be assigned a component importance factor as indicated in this section. The component importance factor, Ip, shall be taken as 1.5 if any of the following conditions apply: 1. The component is required to function for life-safety purposes after an earthquake, including fire protection sprinkler systems. 2. The component contains hazardous materials. 3. The component is in or attached to an Occupancy Category IV structure and it is needed for continued operation of the Facility or its failure could impair the continued operation of the facility. All other components shall be assigned a component importance factor, Ip, equal to 1.0.

ASCE Exemptions. The following nonstructural components are exempt from the requirements of this section: 1.Architectural components in Seismic Design Category B other than parapets supported by bearing walls or shear walls provided that the component importance factor, Ip, is equal to Mechanical and electrical components in Seismic Design Category B. 3.Mechanical and electrical components in Seismic Design Category C provided that the component importance factor, Ip, is equal to Mechanical and electrical components in Seismic Design Categories D, E, and F where the component importance factor, Ip, is equal to 1.0 and either: a. Flexible connections between the components and associated ductwork, piping, and conduit are provided. b. Components are mounted at 4 ft (1.22 m) or less above a floor level and weigh 400 lb(1780 N) or less. 5. Mechanical and electrical components in Seismic Design Categories D, E, and F where the component importance factor, Ip, is equal to 1.0 and a. Flexible connections between the components and associated ductwork, piping, and conduit are provided. b. The components weigh 20 lb (89 N) or less or, for distribution systems, weighing 5 lb/ft (73 N/m) or less.

Information needed Schematics –Conceptual requirements of mechanical systems, including preliminary location and equipment weight –Non “Standard” criteria Vibration Acoustical separation Under floor mechanical systems

Take care of your structural engineer…spend time coordinating during DD! Or this could happen on your next job…lets watch

Information needed Design Development –Establish Story height …… Ceiling height, structural depth and mechanical space requirements –Equipment size and weight –Identify heavy hanging loads due to piping mechanical, boiler rooms, mechanical corridor arenas and stadiums –Vibration / acoustical isolation of equipment –Structural supports for Mechanical equipment cooling towers, generators, chillers, boilers, roof top ducts, stacks

Information needed Design Development –Major shaft openings in floors and roof –Major wall penetrations – shear walls and structural exterior walls –Roof top mechanical penthouses, platforms, mezzanines and catwalks

Information needed Construction Documents.. getting down to the Nitty Gritty dimensions and details –Confirmation of mechanical equipment weights from DD –House keeping pad locations and thickness –Openings in floors and roof – ducts, roof drains, water lines, conduit, bus ducts, grease traps, floor sinks, etc –Openings in exterior foundation walls and grade beams –Beam web penetrations/notches –Ducts running through bar joists –Buried tanks –Plumbing inverts /elevations coordinated with footings –Sump pits –Trench drains

Information needed Roof top mechanical equipment screen wall coordination… Bracing of screen walls to equipment and equipment that has an architectural screen attached. Louver back up structure requirements

Information needed Early Structural construction packages….. ….Project specific……..But in simple terms we need everything that effects structural by the end of DD….

Construction Administration Dimensions not set during design….Contractor and MEP supplier to coordinate equipment specific opening dimension….Always an issue…How can you help? Lets structural engineer know if contractor proposes to switch equipment before the Owner accepts the change…weight, size and opening requirements may change and require re-design…be conservative during design…no savings in structure for equipment weights.

Coordination “…….I do not believe it is possible for a mechanical or electrical engineer to fully meet the expectations of the contractor (and structural engineer) when it comes to coordination ……but we would appreciate your effort….” Ralph Rempel

Coordination List Structural depth and MEP systems Construction tolerances, structure deflection, fire proofing and the wrap on the Mechanical ducts and pipes Floor and roof openings Dimensioned opening size and dimensioned to grids Beam flange widths for telecom and electrical risers and pipes and wall locations. Concrete wall openings For concrete shear walls structural engineer needs to show everything that penetrates the wall. Foundation walls not as critical structural engineer generally has typical details Roof slopes Locate drains near columns Floor drains Coordinate with beam locations

Coordination List –House keeping pads –Fire protection beam penetrations –Louver back up frame dimensions –Perimeter drains –Pipes through perimeter grade beams –Floor drains –Embedded pipes and electrical conduits

Coordination List Slabs…embedded electrical conduits –Slabs on metal deck; space 1 ½” OD conduits at 18” for slabs on metal deck unless Structural designs and details the slab for the conduit. –Spacing can be reduced to 12 inches with minimal design effort. –Spacing tighter than 12 inches will require additional engineering and may cause the slab thickness to increase.

Coordination List Embedded electrical boxes in concrete columns (power and fire alarm) …….try to avoid Avoid electrical conduits and boxes embedded in cast in place concrete columns… Why? Coordination intensive.. Difficult to build at construction joint interfaces. Electrical boxes need to be on structural column details Rebar fire-protection cover to be maintained.

Coordination List Specifications –Embedded electrical conduit In general prohibit embedded conduit “unless as shown on the drawings”. For embedded conduit specify under the submittals section that the contractor shall prepare shop drawing showing the location of the conduit. You may want to also specify that if the conduits are moved in the field that the record drawings show the changes.

Coordination List Specifications cont. –Hung piping »Hang heavy pipes with a trapeze from structural members »Hanging smaller pipes from the slab generally ok »Drilled in inserts »Cast in hangers »Supporting piping from the floor below

Architects and BIM 64% of architects use BIM 71% 3 years or more SEAC 3/2010 survey

Building Information Modeling Interoperable software Shared coordinates Coordination First do it the standard old fashion way Second fly through techniques (navisworks) Last Clash detection.