【10层】15120平米半地下室地上10层钢框架住宅（计算书、建筑、结构图）.zip

12.1 SECTION 12 BEAM AND GIRDER BRIDGES Alfred Hedefi ne, P.E. Former President, Parsons Brinckerhoff Quade D, the web depth, in; and tw, the web thickness, in. For the trial section, Dc?36.02? (D/2?30). Hence, from Eq. (12.18), the web thickness should be at least D?F 36.02?36 cy 3 t?0.38 in, or 8in w 577577 Since the assumed 716-in web thickness exceeds38 in, the requirement for minimum web thickness without longitudinal stiffeners is met. The computations for the location of the neutral axis and for the section moduli are given in Table 12.18 for the composite section, with n?8 for short-time loading, such as live load and impact, and n?3?8?24 for long-time loading, such as superimposed dead loads. To locate the neutral axis, moments are taken about middepth of the girder web. Depth of the concrete haunch atop the girder is assumed to be 2 in. In addition, since the girder is composite, for prevention of fl ange buckling, the width-thickness ratio of the projecting element of the compression fl ange may not exceed 12.42SECTION TWELVE TABLE 12.17Steel Section for Maximum Factored Moment MaterialAdAdAd2IoI Top fl ange 16?116.030.5048814,88014,880 Web 60? 716 26.37,8807,880 Bottom fl ange 20?11230.0?30.75?92328,37028,370 72.3?43551,130 ds? ?435/72.3? ?6.02 in?6.02?435? ?2,620 INA?48,510 Distance from neutral axis of steel section to: Top of steel?30?1?6.02?37.02 in Bottom of steel?30?1.50?6.02?25.48 in Section moduli Top of steelBottom of steel S?48,510/37.02 st 3 ?1,310 in S?48,510/25.48 sb 3 ?1,904 in b?69.6 ?(12.19) t ?1.3dl1 where is the compression stress ksi, in the top fl ange due to noncomposite dead load. dll 2,260?12 ?20.70 ksi dl1 1,310 From Eq. (12.19), for a fl ange width of 16 in, the fl ange thickness t1should be at least ?1.3?20.7 16 t?0.6 in 1 69.62 The 1-in-thick top fl ange is satisfactory. 12.5.5Fatigue Stresses In the next step of the design procedure, fatigue stresses will be investigated. The four- stringer system is considered to have multiple load paths. A single fracture in a member cannot lead to collapse of the bridge. Hence, the structure is not fracture-critical. Determination of the allowable stress range Fsrfor fatigue is based on the stress category for the connection under consideration, the type of load path (redundant or nonredundant), and the stress cycle. The bridge is located on a major highway (Case II) with an average daily truck traffi c in one direction (ADTT) less than 2,500. The plate girders incorporate the four connection types tabulated in Table 12.19 with corresponding stress types and categories. For main (longitudinal) load-carrying members, the number of stress cycles of the maximum stress BEAM AND GIRDER BRIDGES12.43 TABLE 12.18Composite Section for Maximum Factored Moment (a) For superimposed dead loads, n?24 MaterialAdAdAd2IoI Steel section72.3?43551,130 Concrete 100?8.5/2435.437.25131948.12021049,330 107.7884100,460 d24?884/107.7?8.21 in?8.21?884? ?7,260 INA?93,200 Distance from neutral axis of composite section to: Top of steel?31.00?8.21?22.79 in Bottom of steel?31.50?8.21?39.71 in Top of concrete?22.79?2?8.5?33.29 in Top of steelBottom of steelTop of concrete S?93,200/22.79 st 3 ?4,089 in S?93,200/39.71 sb 3 ?2,347 in S?93,200/33.29 c 3 ?2,800 in (b) For live loads, n?8 MaterialAdAdAd2IoI Steel section72.3?43551,130 Concrete 100?8.5/8106.337.253,958147,440640148,080 178.63,523199,210 d8?3523/178.6?19.73 in?19.73?3,523? ?69,510 INA?129,700 Distance from neutral axis of composite section to: Top of steel?31.00?19.73?11.27 in Bottom of steel?31.00?19.73?50.73 in Top of concrete?11.27?2?8.5?21.77 in Top of steelBottom of steelTop of concrete S?129,700/11.27 st 3 ?11,510 in S?129,700/50.73 sb 3 ?2,557 in S?129,700/21.77 c 3 ?5,958 in 12.44SECTION TWELVE TABLE 12.19Categories and Allowable Fatigue Stress Ranges for Connections* Connection typeStress typeCategory Allowable stress range Fsr, ksi 500,000 cycles100,000 cycles Toe of transverse stiffenerTension or reversalC2135.5 Groove weld at fl angesTension or reversalB2949 Gusset plate for lateral bracingTension or reversalB Flange-to-web weldShearF1215 *See AASHTO Specifi cations for full requirements that apply. TABLE 12.20Stresses, ksi, in Composite Girder at Section of Maximum Moment Top of steel (compression)Bottom of steel (tension) DL: ?2,260?12/1,310?20.70 b SDL: ?770?12/4,089?2.26 b LL?I: ?3,832?12/11,510?3.99 b Total:26.95?36 DL: ?2,260?12/1,904?14.24 b SDL: ?770?12/2,347?3.94 b LL?I: ?3,832?12/2,557?17.98 b Total:36.16?36 Top of Concrete SDL: ?770?12/(2,800?8)?0.41 c LL?I: ?3,832?12/(5,958?8)?0.96 c 1.37?4.0 range for Case II, with ADTT? 2,500, the AASHTO standard specifi cations specify 500,000 loading cycles for truck loading and 100,000 for lane loading. Table 12.20 also lists for the four types of connections the allowable stress ranges Fsrfor the redundant-load-path structure based on the connection stress category and the number of stress cycles. The fatigue stress in the bottom fl ange is