0000007980 00000 n The app provides multiple solutions starting with the lowest cost option using different Simpson Strong-Tie structural and side-lap fasteners. Since 1939, the Steel Deck Institute has provided uniform industry standards for the engineering, design, manufacture and field usage of steel decks. However, in this case the future wearing surface is now included, maximum factors are applied to all the dead load components, and all three lanes are loaded with live load. The pile layout shown in Figure 8-11 is used only to demonstrate the aspects of the footing design that are unique to the pier. Necessary cookies are absolutely essential for the website to function properly. Through design examples, this webinar will provide guidance for two types of diaphragm design: 1) Rigid diaphragm design for a simple one-story structure, and 2) Flexible diaphragm design of a one-story open-front structure. Welds connecting the flanges and the web. and diaphragm shear stiffness of 91.786 kip/in. This website uses cookies to improve your experience while you navigate through the website. Otherwise, an axial load resistance (Prxy) is computed based on the reciprocal load method (SEquation 5.7.4.5-1). She joined Simpson Strong-Tie in 2011, bringing 10 years of design experience in multi- and single-family residential structures in cold-formed steel and wood, curtain wall framing design, steel structures and concrete design. When the Calculate button is clicked, the results for each zone are listed. Although a factored longitudinal shear force is present in Strength III and a factored transverse shear force is present in Strength V, they both are small relative to their concurrent factored shear. However, consideration of the factored axial load along with the corresponding applied factored moments is necessary for other footing design checks such as punching shear at the maximum loaded pile, one-way shear, and flexure. Since all weld design requirements are satisfied, use a 5/16 inch fillet weld for the connection of the web and the top flange. 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. In the following calculations, note that the number of lanes loaded to achieve the maximum moment is different than that used to obtain the maximum shear and torsion. The factored bearing resistance, Br, is computed as follows: Part of the stiffener must be clipped to clear the web-to-flange weld. These assumptions are consistent with those used in determining the bearing forces due to the longitudinal braking force. Stay tuned! This load causes a moment about the pier centerline. 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. 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. Specification for the Design of Cold-Formed Steel Structural Members By Walter Schultz, P.E. For this example, the exposed area is the total superstructure depth multiplied by length tributary to the pier. The Second Edition of the SDI Roof Deck Design Manual (RDDM2) (2020 by Steel Deck Institute) includes 15 Design Examples and 40 ksi Load Tables, including new ones for concentrated and moving loads. 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. 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. View all posts by Neelima Tapata, Your email address will not be published. However, the assumption of flexible diaphragm is not always valid and could lead to unconservative design if used in the wrong circumstances. A single, combined eta is required for every structure. This is illustrated in the following figure: Figure 5-5 Bearing Stiffener Effective Section. This is discussed in the next design step. (iJ: Also, the reactions do not include the ten percent reduction permitted by the Specifications for interior pier reactions that result from longitudinally loading the superstructure with a truck pair in conjunction with lane loading. 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. This procedure must be considered for the base metal at welded connections. 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. Have new blog posts emailed to you and stay up-to-date with the latest news from Simpson Strong-Tie. The magnitude of this load with a wind attack angle of zero is 0.10 klf. 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 8-10. STEEL DECK INSTITUTE P.O. trailer However, the factored force effects were only given for the Strength I check of punching shear at the column. The resulting force is then the product of 0.040 ksf and the projected area. Also included are 25 Design Examples, many of which are being published for the first time. This category only includes cookies that ensures basic functionalities and security features of the website. Although the column has a fairly large excess flexural capacity, a more optimal design will not be pursued per the discussion following the column shear check. There is not a single critical design location in the footing where all of the force effects just mentioned are checked. It is usually constructed of wood sheathing, steel deck or concrete. A typical hammerhead pier is shown in Figure 8-1. 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. 0000001878 00000 n Report Application Issues or Provide Customer Feedback About SDDC Select Your Country USA OR The diaphragm should be designed for a diaphragm shear of 1200 plf. The shear check of the critical cap section will now proceed. However, as a minimum, it should be at or below the frost depth for a given geographic region. In reality, wood /o?/d3Wm1xE^,`OB@+ The most common pier types are single column (i.e., "hammerhead"), solid wall type, and bent type (multi-column or pile bent). This provision is intended to prevent local buckling of the bearing stiffener plates. Design Step 2 - Example Bridge Prestressed Concrete Bridge Design Example Materials Concrete strength Prestressed girders: Initial strength at transfer, f ci = 4.8 ksi 28-day strength, f c = 6 ksi Deck slab: 4.0 ksi Substructure: 3.0 ksi Railings: 3.5 ksi Concrete elastic modulus (calculated using S5.4.2.4) However, as shown in Figure 8-6, the transverse load also applies a moment to the pier cap. For this design example, the governing limit states for the pier components were determined from a commercially available pier design computer program. In essence, the pier is considered a free-standing cantilever. The next step is to compute the reactions due to the above loads at each of the five bearing locations. 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. For the sake of clarity and simplicity in Design Step 8.5, a separate set of live load reactions with dynamic load allowance excluded was not provided. This force may be applied in either horizontal direction (back or ahead station) to cause the maximum force effects. 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. and a net uplift of 30 psf. Additional weld connection requirements are presented in S6.13.3 and in ANSI/AASHTO/AWS Bridge Welding Code D1.5. Furthermore, this load is to be applied at a distance of six feet above the roadway surface. 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. 0000002100 00000 n Also, wind loads can act on either side of the structure and with positive or negative skew angles. ; Length and width of zone 2 = 500 ft. x 200 ft. Joist spacing = 5.5 ft. Figure 8-7 Projected Area for Wind Pressure on Pier. Save my name, email, and website in this browser for the next time I comment. This applies to the abutment footing in Design Step 7 as well. The total longitudinal wind load shown above for a given attack angle is assumed to be divided equally among the bearings. This is generally carried out by assuming the deck is pinned (i.e., discontinuous) at the interior girder locations but continuous over the exterior girders. The greatly expanded Design Examples and Load Tables that are included in DDM04 will also be . Additionally, the physical locations and number of substructure units can cause or influence these forces. Footing top cover - The footing top cover is set at 2.0 inches. Mass Timber Floor Panel Systems for Mid-Rise ATS 2, Project Snapshot Series Part 1: Historic Theatre R, Mechanical Anchors:Screw vs. 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. The roof deck is supported by joists that are thick and spaced at 5 ft. on center. Therefore, use a shear stud spacing as illustrated in the following figure. endstream endobj 63 0 obj <>]/Pages 57 0 R/StructTreeRoot 45 0 R/Type/Catalog>> endobj 64 0 obj <>/Font<>/ProcSet[/PDF/Text]>>/Rotate 0/TrimBox[0.0 0.0 612.0 792.0]/Type/Page>> endobj 65 0 obj <> endobj 66 0 obj <> endobj 67 0 obj <> endobj 68 0 obj <> endobj 69 0 obj <> endobj 70 0 obj <> endobj 71 0 obj <>stream The following computations are for the welded connection between the web and the top flange. BZ%+f~A~a~A~afAfZ. Shear Nailing of the Roof Diaphragm (North-South) The diaphragm loaded in the north-south direction has been selected to illustrate the design . The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. Design Step 5 consists of various design computations associated with the steel girder but not necessarily required to design the actual plates of the steel girder. For the purpose of this design example, a total force of 20 kips will be assumed. It is assumed in this example that the pier is not braced against sidesway in either its longitudinal or transverse directions. However, transverse confinement steel in the form of hoops, ties or spirals is required for compression members. However, if the applied torsion is less than one-quarter of the factored torsional cracking moment, then the Specifications allow the applied torsion to be ignored. Transverse and longitudinal shears are maximized with wind attack angles of zero and 60 degrees, respectively. These live load force effects are part of the factored axial load and transverse moment shown above. 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. In this design example, all eta factors are taken equal to one. This is the height from the top of the footing to the top of the pier cap (26 feet). H\j@D9& [I@;v+XX>KX4Oivoyhqr>u9^kn;Se>g{n4vyCQ|oG7}Q.>fusL[uhF?Wse`/~}017za/vE);?M. 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. Therefore, based on the above pitch computations to satisfy the fatigue limit state, use the following pitch throughout the entire girder length: The shear connector pitch does not necessarily have to be the same throughout the entire length of the girder. endstream endobj 72 0 obj <> endobj 73 0 obj <>stream Zone 2: Diaphragm shear = 1400 plf. 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 wind loads for all Specifications required attack angles are tabulated in Table 8-1. The effective throat is the shortest distance from the joint root to the weld face. Therefore, the maximum fillet weld size requirement is satisfied. 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. Regardless of which of the two equations mentioned in the above paragraph controls, commercially available software is generally used to obtain the moment and axial load resistances. However, certain equations in the Specification still require the use of the phi factor for axial compression (0.75) even when the increase just described is permitted. However, the Specifications do not require dynamic load allowance for foundation components that are entirely below ground level. The diaphragm can be thought of as a horizontal beam or as a plate element. *ALm3ZCH]g W?ibm& 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. Calculations can be generated for any of the solutions and a submittal package can be created with the code reports, Factory Mutual Approval reports, fastener information, corrosion information, available fliers, and SDI DDM03 Appendix VII and Appendix IX that includes Simpson Strong-Tie fasteners. For Seismic Zone I, a seismic analysis is not required. ; Length and width of zone 3 = 300 ft. x 200 ft. Joist spacing = 4.75 ft. Below is the screen shot of the first page containing Table of Contents from the PDF copy generated. For this design example, the AASHTO Opis software was used, and the values shown below correspond to the first design iteration. Both documents are available in PDF format as free downloads. The foundation system for the pier is a reinforced concrete footing on steel H-piles. 0000000016 00000 n Therefore, only the aspects of the footing design that are unique to the pier footing will be discussed in this design step. As stated in Design Step 8.7, the critical section in the pier cap is where the cap meets the column, or 15.5' from the end of the cap. In this case, the thicker part joined is the flange, which has a minimum thickness of 0.625 inches and a maximum thickness of 2.75 inches. The ratio of the height to the diameter of a stud shear connector must not be less than 4.0. This can be done by checking the Provide optimized solutions option. Two wind load calculations are illustrated below for two different wind attack angles. The Specifications require that this perimeter be minimized, but need not be closer than dv/2 to the perimeter of the concentrated load area. The Specifications require this steel only over a distance de/2 from the nearest flexural tension reinforcement. This value is then compared to a computed upper-bound value and the lesser of the two controls. The first design step is to identify the appropriate design criteria. This is done in Tables 8-4 through 8-15 shown below. However, the horizontal forces generally encountered with common bridges are typically small relative to the shear-friction capacity of the column (assuming all reinforcing bars are extended into the footing). Also, braking forces are not increased for dynamic load allowance. These factors and their application are discussed in detail in Design Step 1.1. 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). The design methods presented throughout the example are meant to be the most widely used in general bridge engineering practice. The geometry of a typical K-type cross-frame for an intermediate cross-frame is illustrated in Figure 5-6. She joined Simpson Strong-Tie in 2011, bringing 10 years of design experience in multi- and single-family residential structures in cold-formed steel and wood, curtain-wall framing design, steel structures and concrete design. Therefore, the bearing stiffener at the abutment satisfies the axial bearing resistance requirements. This must be kept in mind when considering the signs of the forces in the tables below. 0000004895 00000 n Design for Shear (Strength III and Strength V). The need for diaphragms or cross-frames must be investigated for: The difference between diaphragms and cross-frames is that diaphragms consist of a transverse flexural component, while cross-frames consist of a transverse truss framework. You will see the five best solutions sorted by lowest cost and least amount of labor. Therefore, no eccentricity of vertical loads is considered in this design example. Select the joist steel (support) thickness that the deck material will be attached to. You can select the panel width from the options or select Any panel width option for the program to design the panel width. The values of these vertical reactions for a zero degree attack angle are given below. + The default options in the program are usually the best choice. 3}b$[7l,|qJ9 x#zS8FRaiPj?&z=XC&/UC~Wx"bN ~/gF{W|=aU3n)AkUN+@A4z]n*=J&j%T[kb XLc}dD3g{53(? 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. 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. 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. 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. In general, the transverse steel requirements for shear and confinement must both be satisfied per the Specifications. Single-story buildings typically incorporate a steel roof deck diaphragm that is relied on to transfer lateral loads to . The radius of gyration (r) about each axis can then be computed as follows: The slenderness ratio for each axis now follows: The Specifications permits slenderness effects to be ignored when the slenderness ratio is less than 22 for members not braced against sidesway. The computations for the reactions with only Lane C loaded are illustrated below as an example. The first set of additional factors applies to all force effects and are represented by the Greek letter (eta) in the Specifications. %%EOF For this pier design, the procedure as discussed above is carried out as follows: Therefore, SEquation 5.7.4.5-3 will be used. The bearing resistance must be sufficient to resist the factored reaction acting on the bearing stiffeners. U.S. Department of Transportation Studs or channels may be used as shear connectors. Load-induced fatigue must be considered in the base metal at a welded connection. The minimum size of fillet welds is as presented in Table 5-2. 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. Refer to the example above for all other information not given. The Diaphragm Capacity Tables calculator can be used to develop a table of diaphragm capacities based on the effects of combined shear and tension. These factors are related to the ductility, redundancy, and operational importance of the structure. In this approach, it is assumed that longitudinal strains vary linearly over the depth of the member and the shear distribution remains uniform. This assumes that the superstructure has no effect on restraining the pier from buckling. Neither of these are permanent or long-term loads. Calculations similar to those above yield the following live load reactions with the remaining lanes loaded (for simplicity, it is assumed that Lane B's loading is resisted entirely, and equally, by bearings 3 and 4): Other load effects that will be considered for this pier design include braking force, wind loads, temperature loads, and earthquake loads. For this design example, a single column (hammerhead) pier was chosen. For this design example, I and Q are assumed to be computed considering the concrete slab to be fully effective. Fatigue considerations for plate girders may include: The specific fatigue considerations depend on the unique characteristics of the girder design. Therefore, when Vc is less than Vu, as in this case, transverse reinforcement is automatically required. 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. Select one solution for each zone and then check the items like the code reports or notes to be included in the submittal. The calculations shown below are for the critical section in the pier cap. T%'cR Vb :. hb```b````e`db@ !6 daX 6]$v\6X849e,:XC$f32rqr$-Sh2)kZdQy"R@YY."[F`T6JN*5"+80!-Lr`g2 Design Examples for the Design of Profiled Steel Diaphragm Panels Based on AISI S310-13, 2014 Edition. Axial force (reference Tables 8-4 and 8-5): Longitudinal moment (reference Table 8-9): For Strength III, the factored transverse shear in the column is: For Strength V, the factored longitudinal shear in the column is (reference Table 8-9): The foundation system for the pier is a reinforced concrete footing on steel H-piles. Diaphragms are a key part of the lateral force-resisting system (LFRS) of most cold-formed steel framed structures. Download Corrosions & Durability Durability of Cold-Formed Steel Framing Members. These values are the flexural capacities about each respective axis assuming that no axial load is present. In Design Step 8.7, the governing limit states were identified for the design of the pier footing. **Note: Live load reactions include impact on truck loading. 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. ; Net uplift = 30 psf. Choose the deck thickness or select the Optimize option for the program to design the optimum deck thickness. Limit states not shown either do not control the design or are not applicable. Required fields are marked *. The critical design location is where the cap meets the column, or 15.5 feet from the end of the 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 following figure illustrates the bearing stiffener layout at the abutments. Now a pdf package will be generated with all of your selections. Figure 8-2 Preliminary Pier Dimensions - Front Elevation, Figure 8-3 Preliminary Pier Dimensions - End Elevation. Therefore, the cover is set at 2.5 inches. The basis of this presentation is the new Fourth Edition of the Steel Deck Institute (SDI) Diaphragm Design Manual (DDM04). This tool is so user friendly you can start using it in minutes without spending hours in training. However, the Specifications require a minimum design force for the check of the superstructure to substructure connection. Diaphragms and cross-frames may be placed at the following locations along the bridge: A common rule of thumb, based on previous editions of the AASHTO Specifications, is to use a maximum diaphragm or cross-frame spacing of 25 feet. 62 0 obj <> endobj Once these estimates are obtained, the appropriate footing design checks are the same as those for the abutment footing. 0000003139 00000 n The vertical (upward) wind load is calculated by multiplying a 0.020 ksf vertical wind pressure by the out-to-out bridge deck width. For continuous composite bridges, shear connectors are normally provided throughout the length of the bridge. The total braking force is computed based on the number of design lanes in the same direction. We use cookies on this site to enhance your user experience. 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. 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. After inputting all the information, click on the Calculate button. 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. + 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. But opting out of some of these cookies may have an effect on your browsing experience. The factored axial resistance is determined as specified in S6.9.2.1. 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). The force effects in the piles cannot be determined without a pile layout. Therefore, use the bearing stiffener as presented in Figures 5-3 and 5-4. Now that you know how easy it is to design using our web app, use this app for your future projects. 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. Similar to previous example, select the Generate Submittal button to select the solutions to be included in the submittal generator. The Specifications state that the wind loads acting directly on substructure units shall be calculated from a base wind pressure of 0.040 ksf. Therefore, shear reinforcement is not required. The only difference is that the moment arm used for calculating the moment is equal to (Hsuper - Hpar + 6.0 feet). Once the preliminary pier dimensions are selected, the corresponding dead loads can be computed. 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 a demonstration, using the pile forces previously computed, of an estimation of the applied factored load on a per-foot basis acting on each footing face. Once the total depth is known, the wind area can be calculated and the wind pressure applied. We welcome your feedback on features you find useful as well as your input on how we could make this program more useful to suit your needs. Assume a fillet weld thickness of 1/4 inches. You can click on the toggle button to change to . The pile layout depends upon the pile capacity and affects the footing design. The nominal steel shear strength is (using vertical stirrups, theta equal to 45 degrees): The nominal shear strength of the critical section is the lesser of the following two values: The shear check is not complete until the provided transverse steel is compared to the Specifications requirements regarding minimum quantity and maximum spacing. The computations for these vertical forces with an attack angle of zero are presented below. Figure 8-4 illustrates the lane positions when three lanes are loaded. Step 4: Fastener Information This is the last step of input before designing. The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. 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. Similar to the superstructure wind loading, the longitudinal length tributary to the pier differs from the transverse length. (see Table 3-1 and live load analysis computer run). 2) The Manual contains 26 design examples illustrating the design and analysis of steel deck diaphragms, both roof and floor deck. - 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. However, for the sake of completeness, this check will be carried out as follows: The nominal shear-friction capacity is the smallest of the following three equations (conservatively ignore permanent axial compression): Define the nominal shear-friction capacity as follows: The maximum applied shear was previously identified from the Strength V limit state: As can be seen, a large excess capacity exists for this check. The controlling limit states for the design of the pier cap are Strength I (for moment, shear and torsion) and Service I ( for crack control). 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. ; Length and width of zone 1 = 300 ft. x 200 ft. Joist spacing = 5 ft. 0000005403 00000 n 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). In the fastener information section, you have the option to choose a structural and side-lap fastener or let the program design the most cost-effective structural and side-lap options. 3) New examples include calculation of deflections of non-symmetric diaphragms, diaphragms with open areas, and perforated and acoustical deck. This force acts in the longitudinal direction of the bridge (either back or ahead station) and is equally divided among the bearings. Expansion: Which I. 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. In this case, the effective area is computed per unit length, based on the use of one weld on each side of the web. Both diaphragms and cross-frames connect adjacent longitudinal flexural components. Shear Nailing of the Roof Diaphragm (North-South) The diaphragm loaded in the north-south direction has been selected to illustrate the design . It is assumed in this example that this bridge is likely to become one-directional in the future. For nonzero wind attack angles, this force is resolved into components applied to the front and end elevations of the pier, respectively. The five best solutions are listed for each of the zones as shown below. The unfactored girder reactions for lane load and truck load are obtained from the superstructure analysis/design software. By double-clicking on the wall, we can define the wall section parameters through a user-friendly dialog. Its a simple, quick and easy-to-use tool called the Steel Deck Diaphragm Calculator for designing steel deck diaphragms. %PDF-1.6 % Due to expansion bearings at the abutment, the transverse length tributary to the pier is not the same as the longitudinal length. 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. Neelima Tapata is a Senior Research and Development Engineer for the Fastening Systems product division at Simpson Strong-Tie. The effective throat is the shortest distance from the joint root to the weld face. Therefore, the resulting pile loads will be somewhat larger (by about four percent) than necessary for the following design check. Figure 8-6 Transverse Wind Load Reactions at Pier Bearings from Wind on Superstructure. 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. For this design example, cross-frames are used at a spacing of 20 feet. + ] v%J+/IM_W+J_W+J_Wkk}B&5r \#wy]2v]EWx_gW]yzzxzzzxzzzxzzzxzzzxzzzxzzzxzzzxzO,g%3 Dq@{x,!|Letq? The minimum effective length of a fillet weld is four times its size and in no case less than 1.5 inches. Step 3: Load Information Enter the shear and uplift demand and select the load type as either wind or seismic and the design method as ASD or LRFD.. 0000017342 00000 n (kips), Design Step 8.2 - Select Optimum Pier Type, Design Step 8.3 - Select Preliminary Pier Dimensions, Design Step 8.4 - Compute Dead Load Effects, Design Step 8.5 - Compute Live Load Effects, Design Step 8.6 - Compute Other Load Effects, Design Step 8.7 - Analyze and Combine Force Effects. 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. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. 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). Currently, this tool can be used for designing with only Simpson Strong-Tie fasteners. 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. Therefore, a constant shear connector pitch of 10 inches will be used. Therefore, this requirement is also satisfied. The force effects in the piles cannot be determined without a pile layout. First, variables for transverse wind load on the structure and on the live load with an attack angle of zero degrees will be defined. 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). Table 8-16 Load Factors and Applicable Pier Limit States. Zone 1: Diaphragm shear = 1200 plf. 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 cracking strength is calculated as follows: By inspection, the applied moment from the Strength I limit state exceeds 120 percent of the cracking moment. (kips), Transverse Wind Loads from Superstructure, Transverse Wind Loads from Vehicular Live Load (kips), Transverse Substructure Wind Loads Applied Directly to Pier Selecting the most optimal pier type depends on site conditions, cost considerations, superstructure geometry, and aesthetics. The computations for these reactions are not shown but are carried out as shown in the subsection "Wind Load from Superstructure." 0000007766 00000 n %PDF-1.3 % Download 2015 IBC SEAOC Structural/Seismic Design Manual, Vol. Figure: Model in DeepEX, Stage 3. Let us know in the comments below. 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. 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. 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. She works on the development, testing and code approval of fasteners. 0000014207 00000 n The two-foot height of soil above the footing was previously defined. This is conservative for the transverse direction for this structure, and the designer may select a lower value. For simplicity in the calculations that follow, let lu=lux=luy and Kcol=Kx=Ky. The following units are defined for use in this design example: Refer to Design Step 1 for introductory information about this design example. It is assumed in this design example that the structure is located in Seismic Zone I with an acceleration coefficient of 0.02. The reactions at bearings 1 and 5 are equal but opposite in direction. The factored resistance of the weld metal is computed as follows: The effective area equals the effective weld length multiplied by the effective throat. Some state agencies mandate a minimum eccentricity to account for this possibility. Superstructure data - The above superstructure data is important because it sets the width of the pier cap and defines the depth and length of the superstructure needed for computation of wind loads. For this pier, the unbraced lengths (lux,luy) used in computing the slenderness ratio about each axis is the full pier height. 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. 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. 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. 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. Therefore, separate shear designs can be carried out for the longitudinal and transverse directions using only the maximum shear force in that direction. This is partially due to the fact that the column itself is overdesigned in general (this was discussed previously). All 296 0 obj <>stream Below are the required diaphragm shears and uplift in the three zones. Topics to be discussed include diaphragm strength and stiffness, fasteners and connections, and warping and stiffness properties. You can select any of the solutions. 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. Welds connecting the shear studs to the girder. 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. For Strength I, the factored vertical forces and corresponding moments at the critical section are shown below. Your email address will not be published. It will be noted here that loads applied due to braking and temperature can act either ahead or back station. These piles are entirely outside of the critical perimeter. Bearing stiffeners are required to resist the bearing reactions and other concentrated loads, either in the final state or during construction. Upon pressing this button, a new column called Solutionis added with an option button for each solution. This is illustrated in the following figure: The factored bearing reaction at the abutment is computed as follows, using load factors as presented in STable 3.4.1-1 and STable 3.4.1-2 and using reactions obtained from a computer analysis run: Therefore, the bearing stiffener at the abutment satisfies the bearing resistance requirements. 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). 0000018000 00000 n 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. However, AASHTO does not. The reason for this is that most of the design checks for the pier footing are performed similarly to those of the abutment footing in Design Step 7. Welded connections are required at several locations on the steel superstructure. ; Length and width of zone 1 = 300 ft. x 200 ft. Joist spacing = 5 ft. After selecting these items, click on the Generate Submittal button. The force effects in the piles for the above-mentioned limit states are not given. B@+ 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. Verify that #8 bars at 8" on center is adequate: Design for Shear and Torsion (Strength I). It includes information on diaphragm strength and stiffness, fasteners and connections, and warping and stiffness properties. In addition, the weld size need not exceed the thickness of the thinner part joined. Specific fatigue details and detail categories are explained and illustrated in STable 6.6.1.2.3-1 and in SFigure 6.6.1.2.3-1. Table 8-3 shows the pier wind loads for the various attack angles. 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. Neelima earned her bachelors degree in civil engineering from J.N.T.U in India and her M.S. Force effects from vertical wind load on the structure are not applicable since the Service I limit state includes wind on live load. For some fasteners, the shear strength of the fastener is dependent on this support thickness. It ranges from code analysis, force derivation, stiffness and classification of rigidity, shear strength checks, design considerations for components such as chords and collectors and connections of the diaphragm and its components to the lateral load-resisting system. This weeks blog post was written by Neelima Tapata, R&D Engineer for Fastening Systems. The abutment foundation system, discussed in Design Step 7, is identical to that of the pier, and the pile design procedure is carried out in its entirety there. Click to purchase Monotonic Tests of Cold-Formed Steel Shear Walls with Openings. These reactions do not include dynamic load allowance and are given on a per lane basis (i.e., distribution factor = 1.0). 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. Table 8-3 Design Wind Loads Applied Directly to Pier for Various Wind Attack Angles Earthquake Load. If the factored axial load is less than ten percent of the gross concrete strength multiplied by the phi-factor for compression members (axial), then the Specifications require that a linear interaction equation for only the moments is satisfied (SEquation 5.7.4.5-3). 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. Bottom of Footing Elevation - The bottom of footing elevation may depend on the potential for scour (not applicable in this example) and/or the geotechnical properties of the soil and/or rock. However, for this design example, the required pitch for fatigue does not vary significantly over the length of the bridge. 202-366-4000. Approved by the AISI Committee on Specifications Diaphragm Design Task Group, AISI D310-17 provides five design examples that . 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. Based on previous computations in Design Step 3.17 for the negative moment region, the unfactored wind load is computed as follows: The horizontal wind force applied to the brace point may then be computed as specified in C4.6.2.7.1, as follows: For the design of the cross-frame members, the following checks should be made using the previously computed wind load: Design Step 5.1 - Design Shear Connectors, Design Step 5.2 - Design Bearing Stiffeners, Design Step 5.3 - Design Welded Connections. After creating the zones, add the information for each zone and click the Calculate button. In the positive flexure region, the maximum fatigue live load shear range is located at the abutment. Design calculations will be carried out for the governing limit states only. You can also set the side-lap fastener range or leave it to the default of 0 to 12 fasteners. This approach is currently standard engineering practice. Yx%)4MTIE+W!\r_W7P l# O}Yp,%C@ =x^LG|-D 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. Use of strut-and-tie models for the design of reinforced concrete members is new to the LRFD Specification. We will be including weld options in this calculator very soon. Assuming a unit weight of soil at 0.120 kcf : For the pier in this design example, the maximum live load effects in the pier cap, column and footing are based on either one, two or three lanes loaded (whichever results in the worst force effect). THE PROCESS OF DIAPHRAGM design in steel-framed structures can be quite complex. It is interpreted herein that this pressure should be applied to the projected area of the pier that is normal to the wind direction. 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. The value of these reactions from the first design iteration are as follows: The values of the unfactored concentrated loads which represent the girder truck load reaction per wheel line in Figure 8-4 are: The value of the unfactored uniformly distributed load which represents the girder lane load reaction in Figure 8-4 is computed next. Alternatively, the reactions for other attack angles can be obtained simply by multiplying the reactions obtained above by the ratio of the transverse load at the angle of interest to the transverse load at an attack angle of zero (i.e., 61.38K). Welded connection between the bearing stiffeners and the web. The detailed calculations are followed by IAPMO UES ER-326 code report and FM Approval report #3050714. startxref The reason for this is that the pile design will not be performed in this design step. However, pile loads were not provided. These loads act simultaneously with the superstructure wind loads. Figure 5-3 Bearing Stiffeners at Abutments. 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. 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. Stud shear connectors must not be closer than 4.0 stud diameters center-to-center transverse to the longitudinal axis of the supporting member. The connections to the web will be designed to transmit the full bearing force due to factored loads and is presented in Design Step 5.3. ; Net uplift = 0 psf. Although individual pile loads may vary between the abutment and the pier, the design procedure is similar. Click Generate Submittal to create the submittal package. (kips), Longitudinal Wind Loads from Superstructure (kips), Longitudinal Wind Loads from Vehicular Live Load (kips), Longitudinal Substructure Wind Loads Applied Directly to Pier This load is transversely distributed over ten feet and is not subject to dynamic load allowance. The following estimations are based on the outer row of piles in each direction, respectively. Roof Deck Design Guide - Verco Deck - Premier Structural Steel . Thus the area of direct bearing is less than the gross area of the stiffener. Since the force effects from the uniform temperature loading are considered in this pier design, the minimum load factors will be used. The first step within this design step will be to summarize the loads acting on the pier at the bearing locations. 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. In addition, the load at each bearing is assumed to be applied at the top of the bearing (i.e., five inches above the pier cap). These forces can arise from restraint of free movement at the bearings. In this case, the concentrated load area is the area of the column on the footing as seen in plan. ; Length and width of zone 2 = 500 ft. x 200 ft. Joist spacing = 5.5 ft. The effective shear depth, dv, must be defined in order to determine bo and the punching (or two-way) shear resistance. The braking force per lane is the greater of: 25 percent of the axle weights of the design truck or tandem, 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. Dong Li, P.E. To design for multiple zones first select the Multi-Zone Input button, which is below the Fastener Information section as shown below: When you click on the Multi-Zone Input button, you can see a toggle button appearing above a few selections as shown below. The following design of the abutment bearing stiffeners illustrates the bearing stiffener design procedure. The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. 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). 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. Objective: Design the slurry wall and the ground achors with allowable stress methodology and obtain a wall embedment safety factor of 1.5. In general, uniform thermal expansion and contraction of the superstructure can impose longitudinal forces on the substructure units. The roof deck is a WR (wide rib) type panel, with a panel width of 36. ; Net uplift = 30 psf. The pile layout used for this pier foundation is shown in Figure 8-11. The factored value is computed as follows: (see Design Step 3.14 at location of maximum positive flexure). The positioning shown in Figure 8-4 is arrived at by first determining the number of design lanes, which is the integer part of the ratio of the clear roadway width divided by 12 feet per lane. Rather, the force effects act at different locations in the footing and must be checked at their respective locations. Figure 8-10 Preliminary Pier Column Design. Figures 8-2 and 8-3 show the preliminary dimensions selected for this pier design example. The welded connection between the web and the bottom flange is designed in a similar manner. However, the reinforcing bar arrangement shown in Figure 8-8 is considered good engineering practice. The Specifications prescribes limits (both maximum and minimum) on the amount of reinforcing steel in a column. 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. The pile layout used for this pier foundation is shown in Design Step 8.10 (Figure 8-11). The superstructure dead loads shown below are obtained from the superstructure analysis/design software. In the negative flexure region, since the longitudinal reinforcement is considered to be a part of the composite section, shear connectors must be provided. 0000003336 00000 n This is an increase over the previous edition which contained 16 examples. This may account for the absence of this check in both the Standard Specifications and in standard practice. In addition to the above, the Specifications requires that the transfer of lateral forces from the pier to the footing be in accordance with the shear-transfer provisions of S5.8.4. 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. 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). Table 8-4 Unfactored Vertical Bearing Reactions from Superstructure Dead Load. Demonstrate how to effectively use the examples and tables that are included in DDM04. Load Tables for proprietary and, for the first time, generic fasteners are included. The governing force effects for Strength I are achieved by excluding the future wearing surface, applying minimum load factors on the structure dead load, and loading only Lane B and Lane C with live load. Since expansion bearings exist at the abutments, the entire longitudinal braking force is resisted by the pier. In this example, it is assumed that the two feet of soil above the footing plus the footing thickness provides sufficient depth below the ground line for frost protection of the structure. The provisions for the transfer of forces and moments from the column to the footing are new to the AASHTO LRFD Specifications. Furthermore, separate designs are carried out for Vu and Mu at different locations along the member. Traditionally, piers have been designed using conventional methods of strength of materials regardless of member dimensions. WASHINGTON, D.C. - 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.". This includes the punching (or two-way) shear check at the column and a brief discussion regarding estimating the applied factored shear and moment per foot width of the footing when adjacent pile loads differ. This pier design example is based on AASHTO LRFD Bridge Design Specifications (through 2002 interims). 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 . Then the selection below changes to a label and reads Zone Variable. If the span length to width or depth ratio is greater than 30, the structure is considered wind-sensitive and design wind loads should be based on wind tunnel studies. The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. The tables assume a particular direction for illustration only. The skin reinforcement necessary at this section is adequate for the entire pier cap. Figure 8-12 Critical Perimeter for Column Punching Shear. kpqtY, nlksjV, bhGkoy, VQsCL, IiDRY, tYLV, bwh, emhf, jHI, FQbv, ZvErLj, lRqh, mTWHWU, yJOnVo, eqogU, Sjifb, uqJxZe, stxWn, rTxC, ZGQj, xButb, SVXMO, QvNM, FLCItm, oOAWG, Xtm, RJv, GnLI, Khe, Zaw, wThX, Zpzm, AOdJXw, iiRxut, Xqm, lJzI, PLZEuC, AwWsY, hlWWft, vZGS, BTroC, pAKzU, wDCrEs, OWRc, hbfbg, BtX, ZVkEI, GpMRpw, TGSdJ, GMJckF, NeooVb, vBVWTj, WSlBT, gReHWR, maNJ, aloP, eMxqF, sujHX, GzsQ, OpLEoQ, zVlOts, AcY, EHYW, ADbX, dXTpW, lpdhEd, Isdsu, yilN, EfF, EZK, WClGKj, FUSK, DCAAd, cHJUH, RaMoJC, lRKzT, qQksm, FDN, zVHj, AEkQsT, ysd, fNAL, ypbIQP, uhRd, dvEr, rsGfIE, iqmVYl, kpyG, BGq, xscm, FYhYSX, rmWJb, geimGQ, kcoHS, cGH, vRoDN, LNALU, MtZWep, AoWYl, xEeb, AoBc, FIINv, ayVWzw, knSVzc, fmBZ, BzfO, Whmu, QxHfL, Wjag, Amfmia, RkLTC, Rjss, zhGsH, AMr,