For this design example, stud shear connectors are being used throughout the length of the bridge. Specifying Self-Drilling Screws: Standard vs. Engineered, Our Latest Online Resource: Steel Deck Diaphragm Calculator, A Day in the Life of a Simpson Strong-Tie Structural Engineering Intern. The maximum factored transverse and longitudinal shear forces were derived in Design Step 8.7 and are as follows: These maximum shear forces do not act concurrently. After selecting these items, click on the Generate Submittal button. %%EOF The effective shear depth, dv, must be defined in order to determine bo and the punching (or two-way) shear resistance. Describe the various types and arrangements of fasteners that are commonly used for the attachment of steel deck diaphragms and how they affect the capacities of the diaphragm, including warping and stiffness. 0000006005 00000 n 2015 IBC SEAOC Structural/Seismic Design Manual, Vol. Let's now solve an example to determine the diaphragm design level forces. Approved by the AISI Committee on Specifications Diaphragm Design Task Group, AISI D310-17 provides five design examples that . For this design example, a single column (hammerhead) pier was chosen. This approach is currently standard engineering practice. 3}b$[7l,|qJ9 x#zS8FRaiPj?&z=XC&/UC~Wx"bN ~/gF{W|=aU3n)AkUN+@A4z]n*=J&j%T[kb XLc}dD3g{53(? r rp:H|-TvwkfpA )y/+\`@lrY$7O8:AHOY=/5gs;a[`q9{+vNN|qeaqpVq}D(\}Qb DB"qR-6x `bz]P+%~F3b`C The reason for this is discussed in Design Step 8.10. Yx%)4MTIE+W!\r_W7P l# O}Yp,%C@ =x^LG|-D The nominal shear strength of the column is the lesser of the following two values: It has just been demonstrated that transverse steel is not required to resist the applied factored shear forces. 0000000016 00000 n Therefore, use the bearing stiffener as presented in Figures 5-3 and 5-4. Pier height - Guidance on determining the appropriate pier height can be found in the AASHTO publication A Policy on Geometric Design of Highways and Streets. The superstructure depth includes the total depth from the top of the barrier to the bottom of the girder. oZSgLa(zWXSAr 6WjZjQRf-r i,y}/F&|o7;y! Also, at locations of expansion bearings, a minimum bridge seat must be provided. Neelima earned her bachelors degree in Civil Engineering from J.N.T.U in India and M.S. Select the joist steel (support) thickness that the deck material will be attached to. The factored axial resistance is determined as specified in S6.9.2.1. The design methods presented throughout the example are meant to be the most widely used in general bridge engineering practice. The ratio of the height to the diameter of a stud shear connector must not be less than 4.0. The other set of factors mentioned in the first paragraph above applies only to the live load force effects and are dependent upon the number of loaded lanes. Neelima Tapata is a Senior Research and Development Engineer for the Fastening Systems product division at Simpson Strong-Tie. The Steel Deck Diaphragm Calculator has two parts to it: Optimized Solutions and Diaphragm Capacity Tables. Optimized Solutions is a Designers tool and it offers optimized design solutions based on cost and labor for a given shear and uplift. The pile layout depends upon the pile capacity and affects the footing design. This includes, but is not limited to, defining material properties, identifying relevant superstructure information, determining the required pier height, and determining the bottom of footing elevation. Design a roof deck for a length of L = 500 ft. and a width b = 300 ft. The calculation of the braking force for a single traffic lane follows: 5 percent of the axle weights of the design truck plus lane load: 5 percent of the axle weights of the design tandem plus lane load: The Specifications state that the braking force is applied at a distance of six feet above the roadway surface. For this design example, the AASHTO Opis software was used, and the values shown below correspond to the first design iteration. In this design example, and consistent with standard engineering practice, all steel reinforcing bars in the column extend into, and are developed, in the footing (see Figure 8-13). The minimum effective length of a fillet weld is four times its size and in no case less than 1.5 inches. You can select any of the solutions. Just as the floor (or roof) is checked for vertical load capacity, it is considered a diaphragm in the plane of the floor and check for shear when designing the Lateral Force Resisting System. Fatigue considerations for plate girders may include: The specific fatigue considerations depend on the unique characteristics of the girder design. Mass Timber Floor Panel Systems for Mid-Rise ATS 2, Project Snapshot Series Part 1: Historic Theatre R, Mechanical Anchors:Screw vs. The factored resistance of the weld metal is computed as follows: The effective area equals the effective weld length multiplied by the effective throat. However, since the bearings are assumed incapable of transmitting longitudinal moment, the braking force will be applied at the bearing elevation (i.e., five inches above the top of the pier cap). In this method, axial resistances of the column are computed (using Low_axial if applicable) with each moment acting separately (i.e., Prx with Mux, Pry with Muy). It will be noted here that loads applied due to braking and temperature can act either ahead or back station. The vertical (upward) wind load is calculated by multiplying a 0.020 ksf vertical wind pressure by the out-to-out bridge deck width. This is done in Tables 8-4 through 8-15 shown below. In reality, wood When a structural member meets the definition of a deep component, the Specifications recommends, although does not mandate, that a strut-and-tie model be used to determine force effects and required reinforcing. Such miscellaneous steel design computations include the following: Shear connectors Bearing stiffeners Welded connections Diaphragms and cross-frames Lateral bracing Girder camber For this design example, computations for the shear connectors, a bearing stiffener, a welded connection, and a cross-frame will be presented. The next step is to compute the reactions due to the above loads at each of the five bearing locations. For Strength I, the factored vertical and horizontal forces at the bearings and corresponding force effects at the critical section are shown below. A common rule of thumb is to use K-type cross-frames when the aspect ratio (that is, the ratio of the girder spacing to the girder depth) is greater than about 1.5 to 1 and to use X-type cross-frames when the aspect ratio is less than 1.5 to 1. In addition to all the loads tabulated above, the pier self-weight must be considered when determining the final design forces. Additionally, the total braking force is typically assumed equally distributed among the bearings: Prior to calculating the wind load on the superstructure, the structure must be checked for aeroelastic instability. Zone 2: Diaphragm shear = 1400 plf. The column height exposed to wind is the distance from the ground line (which is two feet above the footing) to the bottom of the pier cap. Some state agencies mandate a minimum eccentricity to account for this possibility. + ] v%J+/IM_W+J_W+J_Wkk}B&5r \#wy]2v]EWx_gW]yzzxzzzxzzzxzzzxzzzxzzzxzzzxzzzxzO,g%3 Dq@{x,!|Letq? The diaphragm should be designed for a diaphragm shear of 1200 plf. The total depth was previously computed in Section 8.1 and is as follows: For this two-span bridge example, the tributary length for wind load on the pier in the transverse direction is one-half the total length of the bridge: In the longitudinal direction, the tributary length is the entire bridge length due to the expansion bearings at the abutments: Since the superstructure is approximately 30 feet above low ground level, the design wind velocity, VB, does not have to be adjusted. These loads along with the pier self-weight loads, which are shown after the tables, need to be factored and combined to obtain total design forces to be resisted in the pier cap, column and footing. Temperature Loading (Superimposed Deformations). Box 426 Glenshaw, PA 15116 Phone: (412) 487-3325 Fax: (412) 487-3326 www.sdi.org DIAPHRAGM DESIGN MANUAL THIRD EDITION Appendix VIII Addendum August 2013 HILTI PIN X-HSN 24. Since 1939, the Steel Deck Institute has provided uniform industry standards for the engineering, design, manufacture and field usage of steel decks. Below is the screen shot of the first page containing Table of Contents from the PDF copy generated. This is an increase over the previous edition which contained 16 examples. It is interpreted herein that this pressure should be applied to the projected area of the pier that is normal to the wind direction. Seismic Design in Steel -- Concepts and Examples (Part 6): Building Analysis and Diaphragm Design (L2) 1.5: Sep-18: Rafael Sabelli, SE: Webinar: A Stability Journey - Diaphragms, Cold-formed Steel and the SSRC: 0: Apr-19: W. Samuel Easterling; Virgina Tech; Blacksburg, VA: SSRC: Lateral Load Transfer -- From Diaphragm to Resisting Elements [L12 . The diaphragm can be thought of as a horizontal beam or as a plate element. endstream endobj 72 0 obj <> endobj 73 0 obj <>stream Figure 8-2 Preliminary Pier Dimensions - Front Elevation, Figure 8-3 Preliminary Pier Dimensions - End Elevation. For the purpose of this design example, a total force of 20 kips will be assumed. Objective: Design the slurry wall and the ground achors with allowable stress methodology and obtain a wall embedment safety factor of 1.5. This results in the following bottom of column forces: Factored force effects for the remaining limit states discussed above are not shown. A single, combined eta is required for every structure. Single-story buildings typically incorporate a steel roof deck diaphragm that is relied on to transfer lateral loads to . The following design of the abutment bearing stiffeners illustrates the bearing stiffener design procedure. The column stiffness is taken as the greater of the following two calculations: The final parameter necessary for the calculation of the amplification factor is the phi-factor for compression. The factored flexural resistances shown above, Mrx and Mry, were obtained by the use of commercial software. This is partially due to the fact that the column itself is overdesigned in general (this was discussed previously). These factors and their application are discussed in detail in Design Step 1.1. The only difference is that the moment arm used for calculating the moment is equal to (Hsuper - Hpar + 6.0 feet). Figure 8-8 shows longitudinal skin reinforcement (#8 bars spaced at 8" on center) over the entire depth of the pier cap at the critical section. Welded connections are required at several locations on the steel superstructure. This must be kept in mind when considering the signs of the forces in the tables below. The following estimations are based on the outer row of piles in each direction, respectively. In general, uniform thermal expansion and contraction of the superstructure can impose longitudinal forces on the substructure units. In addition, the shear connectors must satisfy the following pitch requirements: For transverse spacing, the shear connectors must be placed transversely across the top flange of the steel section and may be spaced at regular or variable intervals. This is conservative for the transverse direction for this structure, and the designer may select a lower value. Based on the skew angle, this load can act transversely, or both transversely and longitudinally. In computing the amplification factor that is applied to the longitudinal moment, which is the end result of the slenderness effect, the column stiffness (EI) about the "X-X" axis must be defined. Consistent with this, the phi-factor for flexure (0.90) was used in obtaining the factored resistance from the factored nominal strength. However, AASHTO does not. This is discussed in the next design step. Select one solution for each zone and then check the items like the code reports or notes to be included in the submittal. Therefore, no eccentricity of vertical loads is considered in this design example. The force effects in the piles cannot be determined without a pile layout. In addition, the transverse load acting six feet above the roadway applies a moment to the pier cap. In this particular structure, with a single pier centered between two abutments that have identical bearing types, theoretically no force will develop at the pier from thermal movement of the superstructure. The stiffeners extend the full depth of the web and, as closely as practical, to the outer edges of the flanges. Also, the forces at each bearing from this load will be applied at the top of the bearing (i.e., five inches above the pier cap). It will be assumed here that adequate vertical clearance is provided given a ground line that is two feet above the top of the footing and the pier dimensions given in Design Step 8.3. U.S. Department of Transportation She is a registered Professional Engineer in the State of California. 0000005688 00000 n This value determines which of two equations provided by the Specification are used. Therefore, a constant shear connector pitch of 10 inches will be used. Design for Axial Load and Biaxial Bending (Strength I): The preliminary column reinforcing is show in Figure 8-10 and corresponds to #10 bars equally spaced around the column perimeter. The final bearing stiffener check relates to the axial resistance of the bearing stiffeners. Therefore, the bearing stiffener at the abutment satisfies the axial bearing resistance requirements. Load Tables for proprietary and, for the first time, generic fasteners are included. But opting out of some of these cookies may have an effect on your browsing experience. Table 8-16 Load Factors and Applicable Pier Limit States. 0000007014 00000 n 0000001564 00000 n THE PROCESS OF DIAPHRAGM design in steel-framed structures can be quite complex. Since the span length to width and depth ratios are both less than 30, the structure does not need to be investigated for aeroelastic instability. Therefore, any and all design lanes may be used to compute the governing braking force. Step 2: Steel Deck Information Select the type of the steel deck along with the fill type. After inputting all the information, click on the Calculate button. These live load force effects are part of the factored axial load and transverse moment shown above. 0000007766 00000 n The factored axial load and corresponding factored biaxial moments at the base of the column are obtained in a manner similar to that for the Strength I force effects in the pier column. The first set of additional factors applies to all force effects and are represented by the Greek letter (eta) in the Specifications. It is mandatory to procure user consent prior to running these cookies on your website. The critical design location is where the column meets the footing, or at the column base. Figure 8-7 Projected Area for Wind Pressure on Pier. The longitudinal moment given above must be magnified to account for slenderness of the column (see Design Step 8.9). The subscripts indicate the bearing location and the lane loaded to obtain the respective reaction: The reactions at bearings 1, 2 and 3 with only Lane C loaded are zero. Footing top cover - The footing top cover is set at 2.0 inches. The skin reinforcement necessary at this section is adequate for the entire pier cap. Design for Shear (Strength III and Strength V). The effective throat is the shortest distance from the joint root to the weld face. Use of strut-and-tie models for the design of reinforced concrete members is new to the LRFD Specification. Therefore, when Vc is less than Vu, as in this case, transverse reinforcement is automatically required. Download However, the factored force effects were only given for the Strength I check of punching shear at the column. Due to expansion bearings at the abutment, the transverse length tributary to the pier is not the same as the longitudinal length. The resulting number of shear connectors must not be less than the number required to satisfy the strength limit states as specified in S6.10.7.4.4. (kips), Transverse Wind Loads from Superstructure, Transverse Wind Loads from Vehicular Live Load (kips), Transverse Substructure Wind Loads Applied Directly to Pier For the welded connection between the web and the flanges, the fillet weld must resist a factored horizontal shear per unit length based on the following equation: This value is greatest at the pier, where the factored shear has its highest value. 0000003139 00000 n Download Cold-Formed Steel Shear Wall Design Guide, 2019 Edition. Exterior girder dead load reactions (DC and DW): Interior girder dead load reactions (DC and DW): In addition to the above dead loads, the weight of the soil on top of the footing must be computed. The app provides multiple solutions starting with the lowest cost option using different Simpson Strong-Tie structural and side-lap fasteners. This paper contains a description of the US seismic design provisions for low-rise steel buildings, as well as a design example of a single-story building located in Boston, MA. Federal Highway Administration The pile layout depends upon the pile capacity and affects the footing design. The loads discussed and tabulated previously can now be factored by the appropriate load factors and combined to determine the governing limit states in the pier cap, column, footing and piles. The Specifications require this steel only over a distance de/2 from the nearest flexural tension reinforcement. This assumes that the superstructure has no effect on restraining the pier from buckling. Load-induced fatigue must be considered in the base metal at a welded connection. Based on the pile layout shown in Figure 8-11, the controlling limit states for the pile design are Strength I (for maximum pile load), Strength III (for minimum pile load), and Strength V (for maximum horizontal loading of the pile group). Figure 8-6 Transverse Wind Load Reactions at Pier Bearings from Wind on Superstructure. The reason for this is discussed in Design Step 8.11. Once the total depth is known, the wind area can be calculated and the wind pressure applied. In addition, the presence of a shear-key, along with the permanent axial compression from the bridge dead load, further increase the shear-friction capacity at the column/footing interface beyond that shown above. ; Length and width of zone 3 = 300 ft. x 200 ft. Joist spacing = 4.75 ft. There is not a single critical design location in the footing where all of the force effects just mentioned are checked. Therefore, only the aspects of the footing design that are unique to the pier footing will be discussed in this design step. Then the lane loading, which occupies ten feet of the lane, and the HL-93 truck loading, which has a six-foot wheel spacing and a two-foot clearance to the edge of the lane, are positioned within each lane to maximize the force effects in each of the respective pier components. This load causes a moment about the pier centerline. 0000014207 00000 n Specifications Commentary C5.6.3.1 indicates that a strut-and-tie model properly accounts for nonlinear strain distribution, nonuniform shear distribution, and the mechanical interaction of Vu, Tu and Mu. The reason for this is that the pile design will not be performed in this design step. The shear is computed based on the individual section properties and load factors for each loading, as presented in Design Steps 3.3 and 3.6: For the noncomposite section, the factored horizontal shear is computed as follows: For the composite section, the factored horizontal shear is computed as follows: Based on the above computations, the total factored horizontal shear is computed as follows: Assume a fillet weld thickness of 5/16 inches. Neelima earned her bachelors degree in civil engineering from J.N.T.U in India and her M.S. The effective length factors, Kx and Ky, are both taken equal to 2.1. The reason for this is twofold: First, in this design example, the requirements of the pier cap dictate the column dimensions (a reduction in the column width will increase the moment in the pier cap, while good engineering practice generally prescribes a column thickness 6 to 12 inches less than that of the pier cap). Figure 8-4 illustrates the lane positions when three lanes are loaded. ; Net uplift = 30 psf. In this case, the concentrated load area is the area of the column on the footing as seen in plan. You can also set the side-lap fastener range or leave it to the default of 0 to 12 fasteners. It is assumed in this design example that the structure is located in Seismic Zone I with an acceleration coefficient of 0.02. The base wind pressures for the superstructure for various attack angles are given in STable 3.8.1.2.2-1. Therefore, it is considered good practice to include an approximate thermal loading even when theory indicates the absence of any such force. Since this design example assumes that the pier cap will be exposed to deicing salts, use: The distance from the extreme tension fiber to the center of the closest bar, using a maximum cover dimension of 2 inches, is: The area of concrete having the same centroid as the principal tensile reinforcement and bounded by the surfaces of the cross-section and a straight line parallel to the neutral axis, divided by the number of bars, is: The equation that gives the allowable reinforcement service load stress for crack control is: The factored service moment in the cap is: To solve for the actual stress in the reinforcement, the distance from the neutral axis to the centroid of the reinforcement (see Figure 8-9) and the transformed moment of inertia must be computed: Once kde is known, the transformed moment of inertia can be computed: Now, the actual stress in the reinforcement is computed: In addition to the above check for crack control, additional longitudinal steel must be provided along the side faces of concrete members deeper than three feet. Then the selection below changes to a label and reads Zone Variable. It is assumed in this example that this bridge is likely to become one-directional in the future. For this design example, cross-frames are used at a spacing of 20 feet. With the standard detailing practices for bridge piers previously mentioned (i.e., all column reinforcement extended and developed in the footing), along with identical design compressive strengths for the column and footing, this requirement is generally satisfied. (iJ: This is demonstrated for the transverse direction as follows: The above calculation for dv is simple to use for columns and generally results in a conservative estimate of the shear capacity. Steel roof and floor deck diaphragm design requires careful attention to load paths, stiffness variations, fastener types, and regional preferences Figure 1: In its most basic form, a diaphragm behaves as if it were a short, deep beam. The Diaphragm Capacity Tables calculator can be used to develop a table of diaphragm capacities based on the effects of combined shear and tension. In essence, the pier is considered a free-standing cantilever. Zone 1: Diaphragm shear = 1200 plf. The total braking force is computed based on the number of design lanes in the same direction. Also included are 25 Design Examples, many of which are being published for the first time. Now that you know how easy it is to design using our web app, use this app for your future projects. Bearing stiffeners are required to resist the bearing reactions and other concentrated loads, either in the final state or during construction. Furthermore, this load is to be applied at a distance of six feet above the roadway surface. In-depth technical editorial for engineers featuring the latest news, useful tools and the strongest ideas in structural engineering. She is a registered Professional Engineer in the State of California. 0000003336 00000 n For example, the punching shear checks are carried out using critical perimeters around the column and maximum loaded pile, while the flexure and one-way shear checks are carried out on a vertical face of the footing either parallel or perpendicular to the bridge longitudinal axis. This applies to the abutment footing in Design Step 7 as well. This includes the placement of reinforcing steel along the bottom face of the pier cap as well, which some state agencies mandate. The tables assume a particular direction for illustration only. Therefore, for this design example, bearing stiffeners are required at both abutments and at the pier. Like most engineers, you are probably often working against tight deadlines, on multiple projects and within short delivery times. Washington, DC - The American Iron and Steel Institute (AISI) has published AISI D310-17, "Design Examples for the Design of Profiled Steel Diaphragm Panels Based on AISI S310-16." The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. Secondly, a short, squat column such as the column in this design example generally has a relatively large excess capacity even when only minimally reinforced. Stud shear connectors must not be closer than 4.0 stud diameters center-to-center transverse to the longitudinal axis of the supporting member. That is, the total transverse and longitudinal load is equally distributed to each bearing and applied at the the top of the bearing (five inches above the top of the pier cap). Additional information is presented about the design assumptions, methodology, and criteria for the entire bridge, including the design features included in this design step. A maximum of five zones can be added. For the pier column of this example, the maximum factored shear in either direction is less than one-half of the factored resistance of the concrete. Shear Nailing of the Roof Diaphragm (North-South) The diaphragm loaded in the north-south direction has been selected to illustrate the design . All stages of assumed construction procedures, Transfer of lateral wind loads from the bottom of the girder to the deck and from the deck to the bearings, Stability of the bottom flange for all loads when it is in compression, Stability of the top flange in compression prior to curing of the deck, Distribution of vertical dead and live loads applied to the structure, Temporary - if they are required only during construction, Permanent - if they are required during construction and in the bridge's final condition, Transfer of wind loads according to the provisions of. What follows is an example of the calculation of the wind loads acting directly on the pier for a wind attack angle of 30 degrees. 0000003863 00000 n These calculations are illustrated below: Note that unless one-half of the product of Vc and the phi-factor for shear is greater than Vu, then transverse reinforcement must be provided. It also presents the interim findings of a . Additionally for the footing and pile designs, the weight of the earth on top of the footing must be considered. 0000004496 00000 n When investigating the need for diaphragms or cross-frames and when designing them, the following must be considered: Diaphragms or cross-frames can be specified as either: At a minimum, the Specifications require that diaphragms and cross-frames be designed for the following: In addition, connection plates must satisfy the requirements of S6.6.1.3.1. In addition to these factors, one must be aware of two additional sets of factors which may further modify the applied loads. + Therefore, the earthquake provisions as identified in the above paragraph will have no impact on the overall pier design and will not be discussed further. For the transverse and longitudinal loadings, the total force in each respective direction is calculated by multiplying the appropriate component by the length of structure tributary to the pier. These cookies do not store any personal information. As stated in Design Step 8.7, the critical section in the pier column is where the column meets the footing, or at the column base. *ALm3ZCH]g W?ibm& In addition, the clear distance between the edge of the top flange and the edge of the nearest shear connector must not be less than 1.0 inch. The following computations are for the welded connection between the web and the top flange. This is illustrated in the following figure: Figure 5-5 Bearing Stiffener Effective Section. 0000018000 00000 n + Step 4: Fastener Information This is the last step of input before designing. For Service I, the factored vertical forces at the bearings and corresponding force effects at the critical section are shown next. The minimum size of fillet welds is as presented in Table 5-2. Federal Highway Administration However, you can change or modify as needed for your project. Actually, an average effective shear depth should be used since the two-way shear area includes both the "X-X" and "Y-Y" sides of the footing. This provision is intended to prevent local buckling of the bearing stiffener plates. The controlling limit states for the design of the pier footing are Strength I (for flexure, punching shear at the column, and punching shear at the maximum loaded pile), Strength IV (for one-way shear), and Service I ( for crack control). This automatically satisfies the following requirements for reinforcement across the interface of the column and footing: A minimum reinforcement area of 0.5 percent of the gross area of the supported member, a minimum of four bars, and any tensile force must be resisted by the reinforcement. Also, since the bearing design is carried out in Design Step 6, the calculations for the check of the connection will not be shown here. It has just been shown that the factored axial load alone is sufficient for the punching shear check at the column. The shear and torsion force effects were computed previously and are: The presence of torsion affects the total required amount of both longitudinal and transverse reinforcing steel. Click to purchase Monotonic Tests of Cold-Formed Steel Shear Walls with Openings. Below is another example of a roof deck to be designed for multiple zones. This force acts in the longitudinal direction of the bridge (either back or ahead station) and is equally divided among the bearings. Two wind load calculations are illustrated below for two different wind attack angles. For the purpose of this design example, all structural components, regardless of dimensions, will be designed in accordance with the conventional strength of materials assumptions described above. This procedure must be considered for the base metal at welded connections. This value is then compared to a computed upper-bound value and the lesser of the two controls. The transverse and longitudinal force components are: The point of application of these loads will be the centroid of the loaded area of each face, respectively. Selecting the most optimal pier type depends on site conditions, cost considerations, superstructure geometry, and aesthetics. For this design example, the governing limit states for the pier components were determined from a commercially available pier design computer program. After all the selections that need to be zone variables are selected, click the Add Zone button. However, for this design example, the required pitch for fatigue does not vary significantly over the length of the bridge. In doing so, the ratio of the maximum factored moment due to permanent load to the maximum factored moment due to total load must be identified (d). The wind loads for all Specifications required attack angles are tabulated in Table 8-1. You can select the panel width from the options or select Any panel width option for the program to design the panel width. It is assumed in this example that the pier is not braced against sidesway in either its longitudinal or transverse directions. Now a pdf package will be generated with all of your selections. hb```b````e`db@ !6 daX 6]$v\6X849e,:XC$f32rqr$-Sh2)kZdQy"R@YY."[F`T6JN*5"+80!-Lr`g2 Estimation of applied factored load per foot in the "X" direction: Estimation of applied factored load per foot in the "Y" direction: Figure 8-13 shows the final pier dimensions along with the required reinforcement in the pier cap and column. For simplicity in the calculations that follow, let lu=lux=luy and Kcol=Kx=Ky. Since the Specifications do not have standards regarding maximum or minimum dimensions for a pier cap, column, or footing, the designer should base the preliminary pier dimensions on state specific standards, previous designs, and past experience. 0000009527 00000 n The transverse wind loads shown in Table 8-1 for a given attack angle are also assumed to be equally divided among the bearings and applied at the top of each bearing. Keep adding zones as needed. Additionally, the physical locations and number of substructure units can cause or influence these forces. In the positive flexure region, the maximum fatigue live load shear range is located at the abutment. These reactions do not include dynamic load allowance and are given on a per lane basis (i.e., distribution factor = 1.0). However, this check is carried out using the effective depth (de) and the required longitudinal tension steel in place of specific applied factored loads. For the fillet weld connecting the bearing stiffeners to the web, the bearing stiffener thickness is 11/16 inches and the web thickness is 1/2 inches. The Diaphragm Capacity Tables calculator can be used to develop a table of diaphragm capacities based on the effects of combined shear and tension, or the Optimized Solutions can be used to provide optimized fastening solutions for a given shear and uplift. The 20-foot spacing in this design example facilitates a reduction in the required flange thicknesses in the girder section at the pier. AVIII-2 August 2013 USER INSTRUCTION . This pier design example is based on AASHTO LRFD Bridge Design Specifications (through 2002 interims). For some fasteners, the shear strength of the fastener is dependent on this support thickness. The force effects in the piles for the above-mentioned limit states are not given. It is worth noting that although the preceding design checks for shear and flexure show the column to be overdesigned, a more optimal column size will not be pursued. The greatly expanded Design Examples and Load Tables that are included in DDM04 will also be . Based on C6.7.4.1, the arbitrary requirement for a 25 foot maximum spacing has been replaced by a requirement for a rational analysis that will often result in the elimination of fatigue-prone attachment details. Flexure from vertical loads (reference Tables 8-4 and 8-5): Shear from vertical loads (reference Tables 8-4 and 8-5): Torsion from horizontal loads (reference Table 8-9): The applied torsion would be larger than the value just calculated if the vertical loads at the bearings are not coincident with the centerline of the pier cap. In the negative flexure region, since the longitudinal reinforcement is considered to be a part of the composite section, shear connectors must be provided. The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. It includes information on diaphragm strength and stiffness, fasteners and connections, and warping and stiffness properties. and diaphragm shear stiffness of 91.786 kip/in. %PDF-1.3 % ; Length and width of zone 2 = 500 ft. x 200 ft. Joist spacing = 5.5 ft. The following figure shows the stud shear connector proportions, as well as the location of the stud head within the concrete deck. The first design step is to identify the appropriate design criteria. The superstructure dead loads shown below are obtained from the superstructure analysis/design software. The controlling limit states for the design of the pier column are Strength I (for biaxial bending with axial load), Strength III (for transverse shear) and Strength V (for longitudinal shear). For a wind attack angle of 0 degrees, the superstructure wind loads acting on the pier are: For a wind attack angle of 60 degrees, the superstructure wind loads acting on the pier are: Table 8-1 Pier Design Wind Loads from Superstructure for Various Wind Attack Angles. When Optimized Solutions is selected, the following input is requested: Step 1: Building Information Enter general information about the project, like the project name, the length and width of the building to be designed along with spacing between the support members such as joist spacing, is entered. U.S. Department of Transportation This point will be approximated here as 17 feet above the top of the footing for both the transverse and longitudinal directions. The governing force effects and their corresponding limit states were determined to be: A preliminary estimate of the required section size and reinforcement is shown in Figure 8-8. The welded connection between the web and the bottom flange is designed in a similar manner. Traditionally, piers have been designed using conventional methods of strength of materials regardless of member dimensions. The magnitude of this load with a wind attack angle of zero is 0.10 klf. This is the height from the top of the footing to the top of the pier cap (26 feet). The roof deck is supported by joists that are thick and spaced at 5 ft. on center. Figure 5-3 Bearing Stiffeners at Abutments. This app can be found on our website, and you dont need to install anything. This weeks blog post was written by Neelima Tapata, R&D Engineer for Fastening Systems. The cracking strength is calculated as follows: By inspection, the applied moment from the Strength I limit state exceeds 120 percent of the cracking moment. However, the reinforcing bar arrangement shown in Figure 8-8 is considered good engineering practice. The default options in the program are usually the best choice. Thus the area of direct bearing is less than the gross area of the stiffener. Once the preliminary pier dimensions are selected, the corresponding dead loads can be computed. However, what is unique to the pier footing is that significant moments act about both axes. For simplicity, the tapers of the pier cap overhangs will be considered solid (this is conservative and helpful for wind angles other than zero degrees). Below are the required diaphragm shears and uplift in the three zones. 202-366-4000, (It should be noted that Design Step 5.4 presents a narrative description rather than design computations.). 0000002549 00000 n These forces can arise from restraint of free movement at the bearings. 0000001296 00000 n However, it is assumed here that the pier can be subjected to a deicing salt spray from nearby vehicles. + The tensile reinforcement provided must be enough to develop a factored flexural resistance at least equal to the lesser of 1.2 times the cracking strength or 1.33 times the factored moment from the applicable strength load combinations. First, variables for transverse wind load on the structure and on the live load with an attack angle of zero degrees will be defined. The bearing area, Apn, is taken as the area of the projecting elements of the stiffener outside of the web-to-flange fillet welds but not beyond the edge of the flange. Figure 8-10 Preliminary Pier Column Design. These factors are termed multiple presence factors by the Specifications. Design Step 8.1 - Obtain Design Criteria This pier design example is based on AASHTO LRFD Bridge Design Specifications(through 2002 interims). Therefore, providing steel sufficient to resist the applied moment automatically satisfies the minimum reinforcement check. In this approach, it is assumed that longitudinal strains vary linearly over the depth of the member and the shear distribution remains uniform. The value of this moment is: The reactions at the bearings are computed as follows: The above computations lead to the following values: The representation of wind pressure acting on vehicular traffic is given by the Specifications as a uniformly distributed load. 0000007980 00000 n If part of a pile is inside the critical perimeter, then only the portion of the pile load outside the critical perimeter is used for the punching shear check. After creating the zones, add the information for each zone and click the Calculate button. These loads were previously calculated and are shown below: In the AASHTO LRFD design philosophy, the applied loads are factored by statistically calibrated load factors. Given: 2-story wood frame building with flexible roof diaphragm Risk Category II, I e = 1.0 S DS = 1.0, S D1 = 0.50 Seismic base shear, V = 180 k . For this design example, two fillet welded connection designs will be presented using E70 weld metal: For the welded connection between the bearing stiffeners and the web, the fillet weld must resist the factored reaction computed in Design Step 5.2. 86 0 obj <>stream Shear Nailing of the Roof Diaphragm (North-South) The diaphragm loaded in the north-south direction has been selected to illustrate the design . The welded connection between the web and the bottom flange is designed in a similar manner. H\@yZv/{Au\tc1.|#0IqLUmwC?tiav~p6C8C1Z~s3&i_p KR.o^Nfmsfusp2e|s>u+qNajSH,~V~U^8pl4SR_YfU8.e/12"W3f/[d/I]r9s\0%s,l=2Jt+V1+ These checks are performed on the preliminary column as follows: The column slenderness ratio (Klu/r) about each axis of the column is computed below in order to assess slenderness effects. Furthermore, separate designs are carried out for Vu and Mu at different locations along the member. For stiffeners consisting of two plates welded to the web, the effective column section consists of the two stiffener elements, plus a centrally located strip of web extending not more than 9tw on each side of the stiffeners. endstream endobj 297 0 obj <>stream For this example, the exposed area is the total superstructure depth multiplied by length tributary to the pier. In general, standard engineering practice for bridge piers automatically satisfies most, if not all, of these requirements. The factored bearing resistance, Br, is computed as follows: Part of the stiffener must be clipped to clear the web-to-flange weld. Reinforcing steel cover requirements (assume non-epoxy rebars): Pier cap and column cover - Since no joint exists in the deck at the pier, a 2-inch cover could be used with the assumption that the pier is not subject to deicing salts. It is usually constructed of wood sheathing, steel deck or concrete. Many girder designs use a variable pitch, and this can be economically beneficial. Prior to carrying out the actual design of the pier cap, a brief discussion is in order regarding the design philosophy that will be used for the design of the structural components of this pier. The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. 3) New examples include calculation of deflections of non-symmetric diaphragms, diaphragms with open areas, and perforated and acoustical deck. The following units are defined for use in this design example: Refer to Design Step 1 for introductory information about this design example. Therefore, slenderness will be considered for the pier longitudinal direction only (i.e., about the "X-X" axis). xref The following properties of the pile group are needed to determine the pile loads (reference Figures 8-11 and 8-12): The following illustrates the pile load in Pile 1: Similar calculations for the other piles outside of the critical perimeter yield the following: The total applied factored shear used for the punching shear check is: Alternate Punching Shear Load Calculation. Since the steel girder has been designed as a composite section, shear connectors must be provided at the interface between the concrete deck slab and the steel section to resist the interface shear. The nominal shear resistance of the critical section is a combination of the nominal resistance of the concrete and the nominal resistance of the steel. In other words, dex is not equal to dey, therefore dvx will not be equal to dvy. The geometry of a typical K-type cross-frame for an intermediate cross-frame is illustrated in Figure 5-6. The following figure illustrates the bearing stiffener layout at the abutments. The critical design location is where the cap meets the column, or 15.5 feet from the end of the cap. Zz}i_t\+O[5A+Hz&qWw;hDzy&:/f7* 5I0>o82 aYXHF'zh,so7Gv1!#%C;Ut0UQ:$Tr*b3yL0EZ Have new blog posts emailed to you and stay up-to-date with the latest news from Simpson Strong-Tie. Design Example 1 n Concrete Diaphragm DesignFour-Story Building Given Information Site data: Site Class D (stiff soil), by default Building data: The example building is Risk Category II in accordance with Table 1.5-1 of ASCE 7-10. The unfactored girder reactions for lane load and truck load are obtained from the superstructure analysis/design software. Also shown are the moment arms to the critical section. The five best solutions are listed for each of the zones as shown below. trailer The clear depth of concrete cover over the tops of the shear connectors should not be less than 2.0 inches, and shear connectors should penetrate at least 2.0 inches into the deck. **Note: Live load reactions include impact on truck loading. The load factors shown in Table 8-16 are the standard load factors assigned by the Specifications and are exclusive of multiple presence and eta factors. Diaphragms are a key part of the lateral force-resisting system (LFRS) of most cold-formed steel framed structures. B@+ Each stiffener will either be milled to fit against the flange through which it receives its reaction or attached to the flange by a full penetration groove weld. The vehicular live loads shown in Table 8-2 are applied to the bearings in the same manner as the wind load from the superstructure. Tables 8-4 through 8-8 summarize the vertical loads, Tables 8-9 through 8-12 summarize the horizontal longitudinal loads, and Tables 8-13 through 8-15 summarize the horizontal transverse loads. Below the Submittal Generator button, you can select various Code Reports and Approvals and Notes and Information selections that you want included in the submittal. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. The Strength I limit state controls for the punching shear check at the column. Zone 3: Diaphragm shear = 1000 plf. ; Length and width of zone 1 = 300 ft. x 200 ft. Joist spacing = 5 ft. The resistance of the fillet weld is then computed as follows: For material 0.25 inches or more in thickness, the maximum size of the fillet weld is 0.0625 inches less than the thickness of the material, unless the weld is designated on the contract documents to be built out to obtain full throat thickness. Additional weld connection requirements are presented in S6.13.3 and in ANSI/AASHTO/AWS Bridge Welding Code D1.5. This load is transversely distributed over ten feet and is not subject to dynamic load allowance. If you have ever wished for a design tool that would make your work easier, we have an app for that. Since the bearings at the pier are fixed both longitudinally and transversely, minimum bridge seat requirements for seismic loads are not applicable. This is illustrated in Figure 8-7. Welded connection between the web and the flanges. BZ%+f~A~a~A~afAfZ. Similarly for bearings 2 and 4: The vertical reactions at the bearings due to transverse wind on the superstructure at attack angles other than zero are computed as above using the appropriate transverse load from Table 8-1. An example calculation is illustrated below using a wind attack angle of 30 degrees: Table 8-2 contains the total transverse and longitudinal loads due to wind load on vehicular traffic at each Specifications required attack angle. Figure 8-12 Critical Perimeter for Column Punching Shear. It is applied at the windward quarter-point of the deck only for limit states that do not include wind on live load. These values are the flexural capacities about each respective axis assuming that no axial load is present. 2 135 Design Example 2 n Flexible Diaphragm Design Diaphragm unit shear at the east side of line 3 and at line 9 is 136 000 160 850,. lbs ft = plf 2. The total longitudinal wind load shown above for a given attack angle is assumed to be divided equally among the bearings. We will be including weld options in this calculator very soon. This additional steel is referred to in the Specifications as longitudinal skin reinforcement. The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. This moment, which acts about the centerline of the pier cap, induces vertical loads at the bearings as illustrated in Figure 8-6. This is illustrated as follows assuming a 3'-6" footing with #9 reinforcing bars at 6" on center in both directions in the bottom of the footing: With the average effective shear depth determined, the critical perimeter can be calculated as follows: The factored shear resistance to punching shear is the smaller of the following two computed values: With the factored shear resistance determined, the applied factored punching shear load will be computed.

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