高强螺栓连接计算---Here is the extracted content from the image: **Question Stem:** 【例 9.2-3】如图 9.2-25 所示高强度螺栓连接的双拼接板拼接，承受轴心力设计值 N=600kN，钢板截面 340mm×12mm，钢材为 Q235 钢，螺栓直径 d=20mm，孔径 d₀=21.5mm。采用 10.9 级的 M22 高强度螺栓，连接处构件接触面用钢丝刷清理浮锈。计算连接一侧所需螺栓个数，并验算构件截面强度。 **Chart/Diagram Description:** * **Type:** Engineering drawing / Structural connection detail diagram, showing both a top view and a side view (cross-section) of a double-splice plate high-strength bolted connection. * **Title:** 图 9.2.25 双拼接板连接示意图 (Figure 9.2.25 Schematic Diagram of Double-Splice Plate Connection) * **Main Elements - Top View:** * Shows a central main plate connected to two outer cover plates by high-strength bolts. * **Bolt Arrangement:** Bolts are arranged in three rows, labeled I, II, and III. Each row contains 3 bolts. The layout is symmetrical about the vertical centerline of the plate. * **Dimensions (in mm):** * Overall width of the main plate: 400. * Horizontal spacing between bolt rows (from left edge to bolt center, then between bolt centers): 50, 70, 70, 50. * Vertical spacing between bolt centers: 50, 100, 50. * **Labels:** Axial force 'N' is indicated by arrows on both ends of the main plate, pointing outwards. Bolts are labeled 'M20'. * **Main Elements - Side View (Cross-section):** * Shows the three stacked plates: a central plate with a thickness of 14 mm, and two outer plates (one on top, one on bottom) each with a thickness of 7 mm. * Bolts pass through all three plates. * **Dimensions (in mm):** * Total length of the bolted connection section: 490. * A dimension of '10' is indicated below the central plate, its specific reference point is not explicitly clear from this view alone. * **General Notes:** The diagram illustrates the configuration of the bolted connection, bolt layout, and key dimensions. **Solution/Explanation:** **解 (Solution):** **(1) 采用摩擦型高强度螺栓，计算一个螺栓的抗剪承载力设计值。** * **Formula:** Nᵥᵇ = 0.9n_fμP * **Calculation:** Nᵥᵇ = 0.9 × 2 × 0.3 × 190 = 102.6 kN **连接一侧所需螺栓数** * **Formula:** n = N / Nᵥᵇ * **Calculation:** n = 600 / 102.6 = 5.84 * **Result:** 取 n=6。 (Take n=6.) **(2) 构件净截面强度验算。** * **Formula:** N' = N (1 - 0.5n₁/n) * **Calculation:** N' = 600 × (1 - 0.5 × 3/6) = 450 kN * **Formula:** σ = N' / A_n * **Calculation:** σ = 450000 / (340 × 12 - 3 × 23.5 × 12) = 139.1 MPa < 215 MPa * **Conclusion:** 钢板第一列螺栓孔处的截面最危险。(The cross-section at the first row of bolt holes of the steel plate is the most critical.)