ENGINEER S DESIGN GUIDELINES

Transcription

1 ENGINEER S DESIGN GUIDELINES Contained herein, for your convenience, are a few of the most frequently used design items. For a more detailed list of code compliant design requirements, refer to AISC supplement No.2 or our prequalifica on report ESR1275 by ICCES. Use of Deeper Frame Columns: In order to achieve the most economical steel moment frame system possible in terms of lowest possible steel tonnage and steel fabrica on costs, it is usually best to select a frame column that is propor oned like a rectangular sec on (e.g. deeper column like W21x or W27x) versus a square (e.g. W12x or W14x), especially at the perimeter edges of the building. Doing so results in a column that has the same structural s ffness when compared to a W14x column, but for half of the steel weight resul ng in 1-3 lbs/square foot in overall steel tonnage savings or about $1 - $3/SF in construc on cost savings. Since the majority of moment frame columns occur around the perimeter of a building, the great majority of columns in the interior space will be gravity load resis ng and can be sized appropriately (e.g. Square tube columns, W12x or W14x). However, depending on the overall building configura on and number of frame columns available in each direc on, occasions do arise where interior moment frame columns are required. Such columns can be a combina on of both deep and shallow without sacrificing economy. When deeper columns are oriented perpendicular to the slab edge such as at corners, it typically is prudent to locate such column several inches off the main grid line as shown below. Pg 1 of 12

2 Edge of Slab Location:!" "!" Welded (FRAME): When deciding the appropriate distance from the center line of perimeter steel framing to the edge of slab, it is important to keep in mind the thickness of the side plates (i.e. ranges from ½ 2 ½ ) as well as the horizontal extension of the bo!om cover plate beyond the face of the side plate (i.e. ranges from 1-2 ½ ) that occur at the perimeter beamto-column joints so that exterior curtain wall systems are not interrupted by the presence of the side plate connec"on itself. Bolted: When deciding the appropriate distance from the center line of perimeter steel framing to the edge of slab, it is important to keep in mind!" "!" the thickness of the side plates (i.e. ranges from ½ 1 ½ ) as well as the horizontal extension of the top angle beyond the face of the side plate (i.e. ranges from 3 1/2-4 ) that occur at the perimeter beam-to-column joints so that exterior curtain wall systems are not interrupted by the presence of the side plate connec"on itself. For an"cipated project specific side plate connec"ons, call SidePlate Systems for more informa"on. Extension of Side Plates: The side plates typically extend horizontally beyond the face of column flange approximately 80% of the frame beam depth (e.g. typical ranges from ). Welded (FRAME): The side plates no longer extend ver"cally below the bo!om of frame beam as they once did. Hence, the only physical item that extends below the bo!om of the beam is the thickness of the bo!om cover plate which is typically no thicker than 1. Bolted : The side plates do extend ver"cally below the bo!om of frame beam by 3 1/2-4. Slab Depressions at Moment Frame Columns: For slab depressions adjacent to a SidePlate connec"on, it s important to keep in mind that the side plates typically have a ver"cal extension of about 3/4 (Bolted) or (Welded) above the top of steel for an average horizontal distance of approximately 80% of the depth of the moment frame beam from the face of column flange. Shorter ver"cal extensions may be possible with the use of a slightly thicker side plate. Refer to graphic on the le&. Please contact SidePlate Systems for details. For more information: Toll Free Tel Pg 2 of 12

3 Steps in Floors at Moment Frame Columns: For steps in floors adjacent to a SidePlate connec on, it s important to keep in mind that the side plates may be tapered as shown in the detail below as required per the architectural design. As such, these areas need to be coordinated between the structural engineer and the architect. Refer to sample detail below. Please contact SidePlate Systems for details. # %& Column - Beam Relationship: Create the lateral model as customary for any project using steel moment frames. When selec ng preliminary lateral beam and columns sizes, it is important to keep in mind the following two rules: $ # #& #& WELDED GEOMETRIC COMPATIBILITY: b bf + 1.1t bf + 1/2 b cf Background: The SidePlate connec on typically consists of cover plates at the beam ends to bridge the difference between the beam flange width and the wider column flange width. The cover plates are fillet welded to the beam flange edges of which the top cover plate is detailed to be approximately the same width as the column flange width. BOLTED GEOMETRIC COMPATIBILITY: b bf + 1 1/2 b cf Background: The SidePlate connec on typically consists of a cover plate and angles at the beam ends. The cover plate is fillet welded to the beam flange edges. STRONG COLUMN WEAK BEAM COMPLIANCE FOR R=8 SMF DESIGNS ONLY: (Z x,col ) > 1.7* (Z x,bm ) for 1-12 stories (rule of thumb) Background: The above equa on takes into account the latest Seismic Provisions equa on for SCWB compliance of SMF connec ons, including an approximate allowance for reduc on in column capacity due to axial loads as well as the pushing out of the plas c hinge into the beam. Pg 3 of 12

4 Computer Modeling Tips: To appropriately represent the connecon sffness properes of SidePlate, the computer model must reflect the following two items: 100% PANEL ZONE RAM FRAME (v14.04+) Automacally incorporated when SidePlate is assigned as the Frame Beam Connecon Type (see below) RAM FRAME (v14.03 and older) assign all frame beam and columns with a rigid end zone of a 0% reducon (refer to Connecon Sffness Implementaon Procedure for RAM v12 & v13 ) ETABS & SAP 2000 Assign all frame beams and columns with a Rigid End Offset of r=1 RISA Assign Rigid End Offsets = 1.0 CONNECTION PROPERTIES BEYOND COLUMN FLANGE The SidePlate connecon typically extends horizontally beyond the face of column flange approximately 80% of the nominal frame beam depth (e.g. typical ranges from ). The connecon properes are different for high seismic (inelasc) applicaons versus wind (elasc) and low seismic applicaons. For R=8 designs, seismic displacement will typically govern the size of the lateral beams and columns. For R=3 designs, wind displacement will typically govern. For seismic displacement controlled lateral members, modify the properes of the beam ends for a distance DIM A (use typical 77% of beam depth): Ix = 3*Ix of frame beam Depth = nominal frame beam depth + 3 (e.g. SidePlate depth) Sx = (2*(3*Ix))/(Depth of SidePlate) Zx = 1.15*Sx value (above) RAM FRAME v Under Criteria, select SidePlate Seismic Displacement (this automacally incorporates the appropriate properes). Then assign the moment connecon type as SidePlate using the Assign Beams - Connec!on command refer to the PDF Specifying and Designing SidePlate Moment Frames in the RAM Structural System ETABS use built-in feature by assigning all frame beams to use SidePlate beam type Note: The modified Sx poron is not included in the ETABS version 9 or 13 built-in feature. If overstresses of 1.25 or less are encountered in the beams, the beams may not be overstressed when checked at the end of the side plates. In order to confirm this, nonprismac beams will need to be ulized refer to PDF Connecon Sffness Implementaon Procedure for ETABS/ SAP RISA/SAP 2000 Insert a node along the ((*+ 456'7451 (-7#! # Pg 4 of 12

5 frame beam located at approximately (½*frame column depth + 77% frame nominal beam depth). Assign a new member between centerline of frame column and new node that has the properes above. For wind displacement controlled lateral members, modify the properes of the beam ends for a distance DIM A (use typical 77% of beam depth): Ix = 1*Ix of frame beam Depth = nominal frame beam depth + 3 (e.g. SidePlate depth) Sx = (2*(1*Ix))/(Depth of SidePlate) Zx = 1.15*Sx value (above) RAM FRAME v Under Criteria, select SidePlate Wind Displacement (this automacally incorporates the appropriate properes). Then assign the moment connecon type as SidePlate using the Assign Beams - Connec!on command refer to the PDF Specifying and Designing SidePlate Moment Frames in the RAM Structural System ETABS create a non-prismac beam to create properes above refer to PDF Connec!on S!ffness Implementa!on Procedure for ETABS/SAP RISA/SAP 2000 Insert a node along the frame beam located at approximately (½*frame column depth + 77% frame nominal beam depth). Assign a new member between centerline of frame column and new node that has the properes above. ((* (-7#! # "#$%"#&' (&&& &)*+,%! Pg 5 of 12

6 Moment Frame Protected Zone (for IMF & SMF Applications Only): AISC Seismic Provisions prohibit certain aachments in the protected zone for all Special and Intermediate Moment Frame applica ons. If required, the protected zone will be iden fied in the SidePlate details. SidePlate s protected zone is iden fied as shown below: ))* '(." + '* +,, - "!"'!"!"!" Lateral Bracing of Beams (for IMF & SMF Applications Only): EOR shall provide lateral bracing of the frame beam s boom flange in accordance with the latest AISC Seismic Provisions, where the length of the beam is defined as the distance between the ends of the side plates. Supplemental top and boom flange bracing at the expected hinge is not required since lateral bracing of the beam at or near the plas c hinge is provided by the side plates as proven by full-scale tests. Lateral Bracing at Beam-to-Column Connections (for SMF Applications Only): The SidePlate connec on is composed of two parallel side plates that are welded to the outside edges of the column flanges for the full depth of each beam plus a certain length above. In addi on, horizontal shear plates are welded to the inside edges of the column web at the top and boom of each side plate. This configura on creates a 100% rigid panel zone and prevents the column flanges from buckling at the levels of top and boom beam flanges and beyond. The connec on also provides the adequate 2% lateral bracing at these levels. All of the full-scale tests were completed without bracing of the column flange at top or boom beam flange and all configura ons had SCWB << 2.0. Test results showed no flexural yielding or lateral-torsional buckling in the column. Hence, the SidePlate moment connec on system is considered to be a Braced Connec on in accordance with AISC Seismic Provisions. Pg 6 of 12

7 0, - Attaching to Face of Side Plate: (for IMF & SMF Applications only): It is acceptable to weld to the face of the side plates in the area indicated using the project approved minimum preheat. / Curved Moment Frames: Due to the inherent torsional robustness of the SidePlate connec!on, curved moment frames are easily achievable without compromising performance by u!lizing one of the following typical methods: 1. A skewed moment frame beam is shop cut into three pieces, their ends mitered to create the required beam skew angle and then complete joint penetra!on (CJP) shop welded back together. Typical skew angles range between 2-15 degrees without requiring any special analysis. Field installa!on is the same as straight beams using fillet welds. In order to resist the out-of-plane force in the beam due to the skew, appropriate lateral bracing of the bo#om beam flange must be provided within 12 of the mitered joint refer to detail below. For angles greater than 15 degrees and up to 30 degrees, contact SidePlate Systems for addi!onal solu!ons. 2" " 1 / / Pg 7 of 12

8 2. A skewed moment frame beam with bent side plates is the same concept as the skewed moment frame beam in op!on 1) where the beam can be a series of 3 straight segments, but instead the curvature begins just passed the column flanges within the gap regions by bending the side plates. Alternately, the beam can be straight from side plates to side plates - refer to detail below. Please Contact SidePlate Systems for details "3 1 / Cantilevers (Drags similar): Can!levers can be used at SidePlate connec!ons whether they are framing into the face of the moment frame column flange (e.g. parallel to the moment frame beam) or framing into the face of the side plate (e.g. perpendicular to the moment frame beam). For condi!ons where the can!lever beam is parallel to the moment frame beam and Can!lever is about 4 or less from the face of column flange, the typical detail is to simply complete joint penetra!on (CJP) weld the can!lever beam to the moment frame column flange. Short can!levers like this could be shop welded to minimize field welding. Can!lever is greater than 4, there are two op!ons that can be done: o Op!on 1) Field CJP weld the can!lever beam to the column flange, or o Op!on 2) use a two-sided SidePlate moment connec!on and field fillet weld the can!lever beam to the side plates. Note: op!on 2 is commonly done for long can!levers and/or heavily loaded can!levers. For condi!ons where the can!lever beam is perpendicular to the moment frame beam, there are three possible scenarios that can occur: 1. Can!lever beam is shallower than the moment frame beam 2. Can!lever beam is deeper than the moment frame beam 3. Can!lever beam is the same depth series as the moment frame beam. Pg 8 of 12

9 For shallower canlever beams, it is strongly recommended whenever possible to ulize a canlever beam that is one beam depth series shallower than the moment frame beam depth to minimize the addional flexural loads imparted onto the side plates, thus minimizing any increase to the thickness of the side plates refer to sample detail to the right., For canlever beams deeper than the moment frame beam, no addional special consideraons are required refer to sample detail to the le for a typical detail used for these condions. For same depth or idencal sized canlever beams, this condion is discouraged because of the bo om of the canlever beam will frame directly into the bo om edge of the side plate, thus not allowing an appropriate CJP welding of the canlever beam s bo om flange to the face of the side plate. If this condion is essenal and can t be eliminated, please contact SidePlate Systems for addional soluons that are available upon request. Pg 9 of 12

10 Sloping Roofs and Exterior Floors: Sloping roofs and sloping exterior framed floors are typically sloped for drainage and/or architectural design purposes up to a maximum of 1.5 per foot. Slopes greater than 1.5 per foot are possible. Please contact SidePlate Systems for details. SidePlate moment frames can be easily sloped in a variety of ways as depicted below: Pg 10 of 12

11 Perpendicular Braces to SidePlate Moment Connections: Diagonal bracing lateral load resisng elements (i.e. wide flange, HSS, BRB or dampers) framing perpendicular to SidePlate connecons can be easily accommodated by ulizing a detail such as : Termination of Moment Frame Column and Roofs The terminaon of moment frame columns above the top of steel need to be coordinated to ensure that the top of the moment frame column assembly is within the finished floor or roof elevaon. For standard popped out condions, this distance is typically about 4 above the top of steel refer to popped out opon detail to the right. For condions where this distance is required to be less than 4, there is a recessed opon which can achieve a 2-3 distance refer to recessed opon detail to the le". Pg 11 of 12

12 Termination of Moment Frame Biaxial Column and Roofs For biaxial moment frame column applicaons only, this distance is a minimum of 8 above the top of steel. Every effort should be made in design to terminate such biaxial moment frame columns at a level below the roof to preclude the addional detailing that may be required at roof condions. Facade Attachements When façade a!achments occur at perimeter moment frame columns, it should be noted that the top of the horizontal shear plates (resng on top of the side plates) are typically 3-4 above the top of steel and should coordinated with the façade manufacturer. For high seismic projects only, façade a!achments on moment frame beams need to be coordinated between the architect and the structural engineer of record to preclude any welding to the beam flanges located within the beam protected zone. For condions where this distance is required to be less than 4, there is a recessed opon which can achieve a 2-3 distance refer to recessed opon detail previous page. Location of Frame Beam Splice (as occurs): The locaon of frame beam splice, DIM F, can be approximated as follows: ½ mes the frame column depth + horizontal extension of side plates (77% of beam depth) mes the frame beam depth Call SidePlate Systems for project specific informaon Pg 12 of 12