Erection of pedestrian ramp of the hottest floor t

2022-08-07
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Erection of pedestrian ramps for external floor type scaffolds

(it can be said that it is the key part of various machinery, electrical appliances, Chinese workers and other products: Niu Guangwen, Niu Yan Guangzhi) the scaffold ramp is the passage for all kinds of personnel to get on and off the scaffold, and the floor type scaffold shall be erected with a pedestrian ramp. According to the relevant provisions of JGJ (hereinafter referred to as the scaffold specification), the scheme has improved the customary erection method of the ramp, which not only simplifies the erection process, but also is safe and reliable, for the reference of the construction safety workers and scaffolders

I. structure and erection of pedestrian ramps

1 The external scaffold attached to the ramp is set, with a total length of 5 spans, including 2 platforms and 3 ramps; The longitudinal distance between the vertical poles of the ramp is the same as that of the scaffold. The width should not be less than 1m, and the slope should be 1:3; The width of the platform shall not be less than the width of the ramp, and the height shall be the step distance of the upright. See the plan and section of the pedestrian ramp for the ramp structure

2. A short horizontal bar is set at the upper and lower parts of the longitudinal horizontal bar at the turning of the platform, and fixed on the longitudinal horizontal bar and the vertical bar with right angle fasteners. The planking shall be laid in full length. The upper end shall be pressed on the transverse horizontal bar at the lower side of the longitudinal horizontal bar, and the lower end shall be pressed on the transverse horizontal bar at the upper end of the longitudinal horizontal bar. In the middle of the planking, two transverse horizontal bars shall be set at the junction of the chute and the vertical bar. The length of the planking probe is 150mm, the end is flat with the platform plate, and the joint is filled with triangle wood. See the node detail drawing ○ A and the part drawing for the method

in the past, the conventional practice was to set two inclined rods on both sides of the chute, on which a horizontal rod was set, and then a scaffold board was set. The advantage of this erection method is that the horizontal horizontal bar can be set according to the needs of supporting the scaffold board, but there are the following problems: (1) the longitudinal horizontal bar is set inside the vertical bar of the ramp, and then the inclined bar is set inward. The horizontal direction at the junction of the inclined bar and the vertical bar is 48mm empty, which makes it difficult to fix the inclined bar and the vertical bar; (2) The upper inclined planking is higher than the platform slab, which affects the use function of the chute; (3) Erection takes time and labor. The feature of this document is that the inclined rod is reduced, the horizontal rod is directly fixed on the vertical rod, and the 50mm thick wood plate is laid longitudinally, simplifying the erection process and facilitating the construction. At the same time, the planking can be used for many times (the longitudinal distance and step distance of the vertical rod of the scaffold are the same). The spacing between horizontal poles supporting the planking is the spacing between vertical poles, La ≤ 1.8m. According to empirical calculation, the planking meets the requirements of bearing capacity

3. The planking shall be made of Chinese fir or pine, and its material shall comply with the provisions of class II material in the current national standard code for design of wood structures (gbj5). The thickness of planking shall not be less than 50mm and the width shall not be less than 200mm. 20 on the planking × 30mm anti-skid wood strips with a spacing of 250~300mm. Batten back nail 40 × 60mm square timber, which is located above the horizontal horizontal bar, has three functions: first, it prevents the eye from sliding towards the planking; Thirdly, it is convenient for the reliable connection between the planking and the horizontal bar; The third is to enhance the overall stiffness of the planking. Just as a whole is formed after installation without filling joints, people will not vibrate when stepping on the jumping board again

II. Checking calculation of bearing capacity of planking

planking is laid in full length, which is calculated as a three span continuous beam. The calculation diagram is shown in Figure 1

Figure 1 pedestrian ramp plan

(I) calculation parameters and loads: ramp slope 1:3, pole spacing la=1.8m, standard value of planking self weight 0.35kn/m2, standard value of uniformly distributed live load 2kn/m2, and live load selection basis: load code for building structures (GB): corridors and stairs of dormitories and residences 2kn/m2. Geometric parameters of 50mm thick wood board assembly width of 1.0m: gross section resistance moment w=417cm3, gross section inertia moment i=1042cm4, gross section area moment s=313 cm3. According to the relevant provisions of the code for design of wood structures (GBJ), the calculation is as follows:

adjustment coefficient of open-air structure of wood: the design value is 0.9, and the elastic modulus is 0.85. The strength design value and elastic modulus of the board are calculated according to the Northeast Larch table

(II) internal force calculation

standard value of self weight load

500mm thick plank

0.35 × 1.0=0.35kn/m

180mm high wood baffle

0.35 × 0.18=0.06kn/m

convert inclined plate line load into plate line load:

q flat = q inclined/cos α, cos α= 0.9487, see Figure 2

Figure 1 planking calculation diagram

Figure 2 self weight calculation diagram

qk1= (0.35+0.6)/0.9487=0.43kn/m

standard value of uniformly distributed live load:

qk2= (2 × 1.0)/0.9487=2.11kn/m

dead load design value:

q1=1.2 × 0.43=0.52kn/m

design value of uniformly distributed live load:

q2=1.4 × 2.11=2.95kn/m

the live load is calculated according to the adverse load distribution, and the relevant adverse internal forces are found in the static calculation manual of building structures

M max=0.1 × zero point five two × 1.82+0.117 × two point nine five × 1.82=1.29kN. m

V=0.6 × zero point five two × 1.8+0.617 × two point nine five × 1.8=3.84kn

(III) checking calculation of bending and shear bearing capacity and deflection

load standard value is used for calculation of deformation

meet the requirements

III. safety measures

1 Protective railings and toe boards shall be set at both sides of the ramp and the periphery of the platform

2. Application of both ends of ramp and platform planking ф 3.2mm galvanized iron wire shall be fixed on the supporting rod to prevent sliding

3. The periphery of the ramp and platform shall be closed with dense mesh

4. The erection height of the ramp, the pole foundation, the pole plus supporting measures for major users, and the longitudinal horizontal pole shall be provided with the scaffold with equal attachment

5. The erection, removal, inspection and acceptance of the ramp shall be in accordance with the relevant provisions of the "scaffold specification": the relative resolution of the force values of the level 0.5 and level 1 testing machines are 0.25% and 0.5% respectively 1/120000 or 1/300000 expresses the relative full-scale resolution value setting

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