This load is transversely distributed over ten feet and is not subject to dynamic load allowance. In addition to all the loads tabulated above, the pier self-weight must be considered when determining the final design forces. Therefore: From this, the design wind pressure is equal to the base wind pressure: Also, the minimum transverse normal wind loading on girders must be greater than or equal to 0.30 KLF: The wind load from the superstructure acting on the pier depends on the angle of wind direction, or attack angle of the wind. 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. These live load force effects are part of the factored axial load and transverse moment shown above. We also use third-party cookies that help us analyze and understand how you use this website. 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. The pier cap, however, must be wide enough to accommodate the bearing. 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 minimum reinforcement requirements will be calculated for the cap. 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. Table 8-3 shows the pier wind loads for the various attack angles. You can click on the toggle button to change to . The first design step is to identify the appropriate design criteria. This may account for the absence of this check in both the Standard Specifications and in standard practice. She is a registered Professional Engineer in the State of California. Figure 8-2 Preliminary Pier Dimensions - Front Elevation, Figure 8-3 Preliminary Pier Dimensions - End Elevation. In Design Step 3.14 for the positive moment region, the fatigue check is illustrated for the fillet-welded connection of the transverse intermediate stiffeners to the girder. Diaphragms are a key part of the lateral force-resisting system (LFRS) of most cold-formed steel framed structures. This tool is so user friendly you can start using it in minutes without spending hours in training. 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. 2015 IBC SEAOC Structural/Seismic Design Manual, Vol. The default for the toggle button is , which means that this selection is same for all the zones. Let's now solve an example to determine the diaphragm design level forces. Design Step 8.1 - Obtain Design Criteria This pier design example is based on AASHTO LRFD Bridge Design Specifications(through 2002 interims). Based on the shear connector penetration information presented in Table 5-1, both of these requirements are satisfied. Roof Deck Design Guide - Verco Deck - Premier Structural Steel . hb```b````e`db@ !6 daX 6]$v\6X849e,:XC$f32rqr$-Sh2)kZdQy"R@YY."[F`T6JN*5"+80!-Lr`g2 This provision is intended to prevent local buckling of the bearing stiffener plates. The pile layout used for this pier foundation is shown in Design Step 8.10 (Figure 8-11). 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. Keep adding zones as needed. 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. Since 1939, the Steel Deck Institute has provided uniform industry standards for the engineering, design, manufacture and field usage of steel decks. This assumes that the superstructure has no effect on restraining the pier from buckling. Therefore, for the sake of clarity in this example, if phi may be increased it will be labeled separately from axial identified above. The geometry of a typical K-type cross-frame for an intermediate cross-frame is illustrated in Figure 5-6. Fatigue considerations for plate girders may include: The specific fatigue considerations depend on the unique characteristics of the girder design. Let us know in the comments below. In Design Step 8.7, the governing limit states were identified for the design of the pier footing. The next step is to compute the reactions due to the above loads at each of the five bearing locations. The provisions for the transfer of forces and moments from the column to the footing are new to the AASHTO LRFD Specifications. 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 is illustrated in the following figure: Figure 5-5 Bearing Stiffener Effective Section. 0000000796 00000 n The factored force effects from Design Step 8.7 for the punching shear check at the column are: It should be noted that in Design Step 8.5, the live load reactions at the bearings include dynamic load allowance on the truck loads. The longitudinal moment given above must be magnified to account for slenderness of the column (see Design Step 8.9). ; Net uplift = 30 psf. For this design example, cross-frames are used at a spacing of 20 feet. 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. The force effects in the piles cannot be determined without a pile layout. 0000003139 00000 n Due to expansion bearings at the abutment, the transverse length tributary to the pier is not the same as the longitudinal length. The effective shear depth, dv, must be defined in order to determine bo and the punching (or two-way) shear resistance. These factors are termed multiple presence factors by the Specifications. Therefore, it is considered good practice to include an approximate thermal loading even when theory indicates the absence of any such force. Figure 8-4 illustrates the lane positions when three lanes are loaded. 0000003250 00000 n In this case, the concentrated load area is the area of the column on the footing as seen in plan. The Specifications require that this perimeter be minimized, but need not be closer than dv/2 to the perimeter of the concentrated load area. This value is obtained by summing the loads in the piles that are outside of the critical perimeter. *ALm3ZCH]g W?ibm& (iJ: Use of strut-and-tie models for the design of reinforced concrete members is new to the LRFD Specification. Zone 1: Diaphragm shear = 1200 plf. 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. Table 8-4 Unfactored Vertical Bearing Reactions from Superstructure Dead Load. Solving for the reactions is then elementary. 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. Demonstrate how to effectively use the examples and tables that are included in DDM04. Its a simple, quick and easy-to-use tool called the Steel Deck Diaphragm Calculator for designing steel deck diaphragms. However, this check is carried out using the effective depth (de) and the required longitudinal tension steel in place of specific applied factored loads. The minimum size of fillet welds is as presented in Table 5-2. 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. Included in this depth is any haunch and/or depth due to the deck cross-slope. 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 shear connectors must permit a thorough compaction of the concrete to ensure that their entire surfaces are in contact with the concrete. This website uses cookies to improve your experience while you navigate through the website. 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. The factored value is computed as follows: (see Design Step 3.14 at location of maximum positive flexure). The Specifications state that the wind loads acting directly on substructure units shall be calculated from a base wind pressure of 0.040 ksf. The first design step is to identify the appropriate design criteria. 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). 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. Neelima earned her bachelors degree in Civil Engineering from J.N.T.U in India and M.S. 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. 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. oZSgLa(zWXSAr 6WjZjQRf-r i,y}/F&|o7;y! 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. However, the reinforcing bar arrangement shown in Figure 8-8 is considered good engineering practice. These loads act simultaneously with the superstructure wind loads. The following figure illustrates the bearing stiffener layout at the abutments. 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. 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. 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. Your email address will not be published. 0000006005 00000 n 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. Therefore, for this design example, bearing stiffeners are required at both abutments and at the pier. These factors are related to the ductility, redundancy, and operational importance of the structure. Table 8-3 Design Wind Loads Applied Directly to Pier for Various Wind Attack Angles Earthquake Load. Design the diaphragm for wind loading using Allowable Stress Design method. The final bearing stiffener check relates to the axial resistance of the bearing stiffeners. 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). A single, combined eta is required for every structure. You can also set the side-lap fastener range or leave it to the default of 0 to 12 fasteners. 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. 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. The roof deck is a WR (wide rib) type panel, with a panel width of 36. 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. For nonzero wind attack angles, this force is resolved into components applied to the front and end elevations of the pier, respectively. Click Generate Submittal to create the submittal package. 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. The steel deck is ASTM A653 SS Grade 33 deck with Fu = 45 ksi. She works in the development, testing and code approval of fasteners. However, as shown in Figure 8-6, the transverse load also applies a moment to the pier cap. 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). The factored flexural resistances shown above, Mrx and Mry, were obtained by the use of commercial software. For Service I, the factored vertical forces at the bearings and corresponding force effects at the critical section are shown next. The foundation system for the pier is a reinforced concrete footing on steel H-piles. Therefore, use a shear stud spacing as illustrated in the following figure. This moment, which acts about the centerline of the pier cap, induces vertical loads at the bearings as illustrated in Figure 8-6. As illustrated in Figure 5-6, the intersection of the centroidal axes of the two diagonals coincides with the centroidal axis of the bottom strut. Such miscellaneous steel design computations include the following: For this design example, computations for the shear connectors, a bearing stiffener, a welded connection, and a cross-frame will be presented. 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. 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. 202-366-4000, (It should be noted that Design Step 5.4 presents a narrative description rather than design computations.). Since the bearings at the pier are fixed both longitudinally and transversely, minimum bridge seat requirements for seismic loads are not applicable. 0000007014 00000 n Verify that #8 bars at 8" on center is adequate: Design for Shear and Torsion (Strength I). 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. The values of these vertical reactions for a zero degree attack angle are given below. Welded connections are required at several locations on the steel superstructure. 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. 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. 0000008770 00000 n Download Welded connection between the web and the flanges. Expansion: Which I. After creating the zones, add the information for each zone and click the Calculate button. 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. Now a pdf package will be generated with all of your selections. The following design of the abutment bearing stiffeners illustrates the bearing stiffener design procedure. For this example, the exposed area is the total superstructure depth multiplied by length tributary to the pier. 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. 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. This is also a crack control check. 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. The critical design location is where the cap meets the column, or 15.5 feet from the end of the cap. In general, standard engineering practice for bridge piers automatically satisfies most, if not all, of these requirements. 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 . T%'cR Vb :. 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. 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. ; Length and width of zone 1 = 300 ft. x 200 ft. Joist spacing = 5 ft. Figure 8-6 Transverse Wind Load Reactions at Pier Bearings from Wind on Superstructure. 0000001878 00000 n The factored axial resistance is determined as specified in S6.9.2.1. Rather, the force effects act at different locations in the footing and must be checked at their respective locations. The computed magnification factor and final factored forces are: With the applied factored loads determined, the next step in the column punching shear check is to define the critical perimeter, bo. 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). trailer The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. You can select the panel width from the options or select Any panel width option for the program to design the panel width. Additional weld connection requirements are presented in S6.13.3 and in ANSI/AASHTO/AWS Bridge Welding Code D1.5. 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. 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. The bearing resistance must be sufficient to resist the factored reaction acting on the bearing stiffeners. r rp:H|-TvwkfpA )y/+\`@lrY$7O8:AHOY=/5gs;a[`q9{+vNN|qeaqpVq}D(\}Qb DB"qR-6x `bz]P+%~F3b`C For Strength I, the factored vertical forces and corresponding moments at the critical section are shown below. The minimum effective length of a fillet weld is four times its size and in no case less than 1.5 inches. These piles are entirely outside of the critical perimeter. In this approach, it is assumed that longitudinal strains vary linearly over the depth of the member and the shear distribution remains uniform. 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. She is a registered Professional Engineer in the State of California. Also, braking forces are not increased for dynamic load allowance. You will see the five best solutions sorted by lowest cost and least amount of labor. 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. 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. 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). Since the force effects from the uniform temperature loading are considered in this pier design, the minimum load factors will be used. This computation is shown as follows: Based on the above check, torsion will be neglected and will not be discussed further. **Note: Live load reactions include impact on truck loading. Footing top cover - The footing top cover is set at 2.0 inches. In this case, as you can see in the screen shot above, detailed calculations for solution #1 are included with XLQ114T1224 structural screws; XU34S1016 side-lap screws; 36/9 structural pattern and with (10) side-lap fasteners; diaphragm shear strength of 1205 plf. In the positive flexure region, the maximum fatigue live load shear range is located at the abutment. Once these estimates are obtained, the appropriate footing design checks are the same as those for the abutment footing. For the fillet weld connecting the web to the flanges, the web thickness is 0.5 inches, the minimum flange thickness is 0.625 inches, and the maximum flange thickness is 2.75 inches. /o?/d3Wm1xE^,`OB@+ 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. Then click on the Submittal Generator button. 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. The reactions at the two outermost bearings (numbered 4 and 5 in Figure 8-4), along with the self-weight of the cap overhang, cause the force effects at the critical section. For this design example, the ratio is computed based on the dimensions presented in Figure 5-1, as follows: The pitch of the shear connectors must be determined to satisfy the fatigue limit state as specified in S6.10.7.4.2 and S6.10.7.4.3, as applicable. Although similar provisions have existed in the ACI Building Code for some time, these provisions are absent from the AASHTO Standard Specifications. Design a roof deck for a length of L = 500 ft. and a width b = 300 ft. This value is then compared to a computed upper-bound value and the lesser of the two controls. Step 4: Fastener Information This is the last step of input before designing. Below is another example of a roof deck to be designed for multiple zones. Zoning is a good way to optimize the economy of the roof diaphragm. Thus the area of direct bearing is less than the gross area of the stiffener. Therefore, d is taken equal to zero for this design. 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 vertical (upward) wind load is calculated by multiplying a 0.020 ksf vertical wind pressure by the out-to-out bridge deck width. 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, per the Specifications, 2.4 ksi could be used for the pier footing. 0000007879 00000 n 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. (see Table 3-1 and live load analysis computer run). + The design of the pier cap will now proceed. Assume a fillet weld thickness of 1/4 inches. Note that the Specifications only permit the following approximate evaluation of slenderness effects when the slenderness ratio is below 100. 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. The Specifications prescribes limits (both maximum and minimum) on the amount of reinforcing steel in a column. The base wind pressures for the superstructure for various attack angles are given in STable 3.8.1.2.2-1. In this case, the effective area is computed per unit length, based on the use of one weld on each side of the web. 2015 IBC SEAOC Structural/Seismic Design Manual, Vol. 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. AVIII-2 August 2013 USER INSTRUCTION . Select one solution for each zone and then check the items like the code reports or notes to be included in the submittal. The stiffeners extend the full depth of the web and, as closely as practical, to the outer edges of the flanges. 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. 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. Some state agencies mandate a minimum eccentricity to account for this possibility. This weeks blog post was written by Neelima Tapata, R&D Engineer for Fastening Systems. For this design example, the AASHTO Opis software was used, and the values shown below correspond to the first design iteration. This approach is currently standard engineering practice. Required fields are marked *. Selecting the most optimal pier type depends on site conditions, cost considerations, superstructure geometry, and aesthetics. The total braking force is computed based on the number of design lanes in the same direction. It is interpreted herein that this pressure should be applied to the projected area of the pier that is normal to the wind direction. Choose the deck thickness or select the Optimize option for the program to design the optimum deck thickness. This app can be found on our website, and you dont need to install anything. vt@0*@Tu*fc$@[2Bg`;yHX*Kt&MF fv:tj0IADA&%r(qqASY40Emx]$A" 8 In general, uniform thermal expansion and contraction of the superstructure can impose longitudinal forces on the substructure units. Download Corrosions & Durability Durability of Cold-Formed Steel Framing Members. The design guide is the supporting document for AISI S310-16, North American Standard for the Design of Profiled Steel Diaphragm Panels, 2016 Edition. The reason for this is that the pile design will not be performed in this design step. Welded connection between the bearing stiffeners and the web. This load causes a moment about the pier centerline. The force effects in the piles for the above-mentioned limit states are not given. However, AASHTO does not. The effective depth (de) of the section shown in Figure 8-8 is computed as follows: Solve for the required amount of reinforcing steel, as follows: The above two equations are derived formulas that can be found in most reinforced concrete textbooks. Such miscellaneous steel design computations include the following: Shear connectors Bearing stiffeners Welded connections Diaphragms and cross-frames Lateral bracing Girder camber For this design example, computations for the shear connectors, a bearing stiffener, a welded connection, and a cross-frame will be presented. The reactions at bearings 1 and 5 are equal but opposite in direction. The radius of gyration (r) about each axis can then be computed as follows: The slenderness ratio for each axis now follows: The Specifications permits slenderness effects to be ignored when the slenderness ratio is less than 22 for members not braced against sidesway. The maximum factored transverse and longitudinal shear forces were derived in Design Step 8.7 and are as follows: These maximum shear forces do not act concurrently. The tables assume a particular direction for illustration only. The effective throat is the shortest distance from the joint root to the weld face. 3}b$[7l,|qJ9 x#zS8FRaiPj?&z=XC&/UC~Wx"bN ~/gF{W|=aU3n)AkUN+@A4z]n*=J&j%T[kb XLc}dD3g{53(? In addition, the transverse load acting six feet above the roadway applies a moment to the pier cap. 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. 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. This value determines which of two equations provided by the Specification are used. The Strength I limit state controls for the punching shear check at the column. Have new blog posts emailed to you and stay up-to-date with the latest news from Simpson Strong-Tie. )L9hX/a 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. These values are the flexural capacities about each respective axis assuming that no axial load is present. After all the selections that need to be zone variables are selected, click the Add Zone button. The resulting force is then the product of 0.040 ksf and the projected area. These cookies do not store any personal information. 86 0 obj <>stream For simplicity in the calculations that follow, let lu=lux=luy and Kcol=Kx=Ky. Refer to the example above for all other information not given. The detailed calculations are followed by IAPMO UES ER-326 code report and FM Approval report #3050714. Therefore, the cover is set at 2.5 inches. ETABS is used to calculate the self-weight of the slabs, beams, girders, columns and shear walls. The most common pier types are single column (i.e., "hammerhead"), solid wall type, and bent type (multi-column or pile bent). 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. However, seldom are ideal conditions achieved in a physical structure. For Seismic Zone I, a seismic analysis is not required. Figure: Model in DeepEX, Stage 3. 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. Yx%)4MTIE+W!\r_W7P l# O}Yp,%C@ =x^LG|-D 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. Furthermore, separate designs are carried out for Vu and Mu at different locations along the member. 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). 3) New examples include calculation of deflections of non-symmetric diaphragms, diaphragms with open areas, and perforated and acoustical deck. The pile layout depends upon the pile capacity and affects the footing design. 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. It is assumed in this design example that the structure is located in Seismic Zone I with an acceleration coefficient of 0.02. The pile layout used for this pier foundation is shown in Figure 8-11. This moment induces vertical reactions at the bearings. The computations for these vertical forces with an attack angle of zero are presented below. 0000001296 00000 n The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. Additionally for the footing and pile designs, the weight of the earth on top of the footing must be considered. The computations for the reactions with only Lane C loaded are illustrated below as an example. However, the factored force effects were only given for the Strength I check of punching shear at the column. xref The effective throat is the shortest distance from the joint root to the weld face. Zone 2: Diaphragm shear = 1400 plf. 0 Figure 8-10 Preliminary Pier Column Design. 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. Both documents are available in PDF format as free downloads. 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. The attack angle is taken as measured from a line perpendicular to the girder longitudinal axis (see Figure 8-5). 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. 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). Therefore, the resulting pile loads will be somewhat larger (by about four percent) than necessary for the following design check. The design methods presented throughout the example are meant to be the most widely used in general bridge engineering practice. 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 first step within this design step will be to summarize the loads acting on the pier at the bearing locations. The Diaphragm Capacity Tables calculator can be used to develop a table of diaphragm capacities based on the effects of combined shear and tension. Load Tables for proprietary and, for the first time, generic fasteners are included. 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. The design methods presented throughout the example are meant to be the most widely used in general bridge engineering practice. 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. 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. Once the total depth is known, the wind area can be calculated and the wind pressure applied. However, pile loads were not provided. Objective: Design the slurry wall and the ground achors with allowable stress methodology and obtain a wall embedment safety factor of 1.5. 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. Shear Nailing of the Roof Diaphragm (North-South) The diaphragm loaded in the north-south direction has been selected to illustrate the design . This additional steel is referred to in the Specifications as longitudinal skin reinforcement. 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. 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. 0000003863 00000 n Table 8-5 Unfactored Vertical Bearing Reactions from Live Load, Table 8-6 Unfactored Vertical Bearing Reactions from Wind on Superstructure, Table 8-7 Unfactored Vertical Bearing Reactions from Wind on Live Load, Table 8-8 Unfactored Vertical Bearing Reactions from Vertical Wind on Superstructure, **Note: Values shown are for a single lane loaded, Table 8-9 Unfactored Horizontal Longitudinal Bearing Reactions from Braking and Temperature, Table 8-10 Unfactored Horizontal Longitudinal Bearing Reactions from Wind on Superstructure, Table 8-11 Unfactored Horizontal Longitudinal Bearing Reactions from Wind on Live Load, Table 8-12 Unfactored Horizontal Longitudinal Loads from Wind Directly on Pier, Table 8-13 Unfactored Horizontal Transverse Bearing Reactions from Wind on Superstructure, Table 8-14 Unfactored Horizontal Transverse Bearing Reactions from Wind on Live Load, Table 8-15 Unfactored Horizontal Transverse Loads from Wind Directly on Pier. Additionally, with all of the column reinforcement extended into the footing, along with the fact that the column and footing have the same compressive strength, a bearing check at the base of the column and the top of the footing is not applicable. The resistance of the fillet weld in shear is the product of the effective area and the factored resistance of the weld metal. These cookies will be stored in your browser only with your consent. All + For Strength I, the factored vertical and horizontal forces at the bearings and corresponding force effects at the critical section are shown below. The reinforcement area provided must now be checked to ensure that the section is not overreinforced: The control of cracking by distribution of reinforcement must be satisfied. Save my name, email, and website in this browser for the next time I comment. In reality, wood Shear diaphragms are commonly used in buildings as a means of transmitting lateral loads. Many girder designs use a variable pitch, and this can be economically beneficial. It will be noted here that loads applied due to braking and temperature can act either ahead or back station. The unfactored girder reactions for lane load and truck load are obtained from the superstructure analysis/design software. These factors for this bridge are shown as follows: Table 8-16 contains the applicable limit states and corresponding load factors that will be used for this pier design. After selecting these items, click on the Generate Submittal button. The magnitude of this load with a wind attack angle of zero is 0.10 klf. This point will be approximated here as 17 feet above the top of the footing for both the transverse and longitudinal directions. Although individual pile loads may vary between the abutment and the pier, the design procedure is similar. 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. 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. Transverse and longitudinal shears are maximized with wind attack angles of zero and 60 degrees, respectively. 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). Therefore, only the aspects of the footing design that are unique to the pier footing will be discussed in this design step. 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. Limit states not shown either do not control the design or are not applicable. ; Length and width of zone 1 = 300 ft. x 200 ft. Joist spacing = 5 ft. Stud shear connectors must not be closer than 4.0 stud diameters center-to-center transverse to the longitudinal axis of the supporting member. Use reinforced concrete and steel rebars. 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. + 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. ; Length and width of zone 2 = 500 ft. x 200 ft. Joist spacing = 5.5 ft. The roof deck is supported by joists that are thick and spaced at 5 ft. on center. The diaphragm should be designed for a diaphragm shear of 1200 plf. Federal Highway Administration This force may be applied in either horizontal direction (back or ahead station) to cause the maximum force effects. Dong Li, P.E. Zone 1: Diaphragm shear = 1200 plf. By double-clicking on the wall, we can define the wall section parameters through a user-friendly dialog. 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. It is assumed in this example that the pier is not braced against sidesway in either its longitudinal or transverse directions. It has just been shown that the factored axial load alone is sufficient for the punching shear check at the column. From Design Step 8.7, it can be seen that the only force effects contributing to the longitudinal moment are the live load braking force and the temperature force. However, the assumption of flexible diaphragm is not always valid and could lead to unconservative design if used in the wrong circumstances. The pitch, p, of the shear connectors must satisfy the following equation: The parameters I and Q are based on the short-term composite section and are determined using the deck within the effective flange width. It is mandatory to procure user consent prior to running these cookies on your website. 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. 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. + ] v%J+/IM_W+J_W+J_Wkk}B&5r \#wy]2v]EWx_gW]yzzxzzzxzzzxzzzxzzzxzzzxzzzxzzzxzO,g%3 Dq@{x,!|Letq? Shear wall design with envelope method Diaphragms are typically designed assuming that the diaphragm is flexible, spanning between shear walls like a simply supported beam. The skin reinforcement necessary at this section is adequate for the entire pier cap. 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. 0000000016 00000 n 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). Design a roof diaphragm that will be zoned into three different areas. It includes information on diaphragm strength and stiffness, fasteners and connections, and warping and stiffness properties. 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. 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. This is partially due to the fact that the column itself is overdesigned in general (this was discussed previously). Single-story buildings typically incorporate a steel roof deck diaphragm that is relied on to transfer lateral loads to . in civil engineering with a focus on structural engineering from Lamar University. 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. 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. 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