Column formwork check (1200mm side length as an example)

First, the parameter information

1. Basic parameters

Column formwork height: 4.3m ; structural surface requirements: hidden; see the detailed description of the column formwork.

2. Panel parameters

Panel thickness: 18mm ;

Bending design value fm : 31N/mm ² ; elastic modulus E : 11500N/mm ² ;

3. Fixed card parameters

Fixed card setting pitch (mm) : 300

Material: The slats are made of Q235 grade steel plate and the fastening screws are made of 8.8 grade steel screws.

4. Load parameters

concrete formwork side pressure standard value G _4k : 36.952kN / m ² ;

The standard value of the load generated by dumping Q Q _3k : 2kN/m ² ;

Second, the calculation of the column formwork panel

The panel is a bent structure and its bending strength and stiffness need to be checked. Here, the calculated width of the panel is 10mm.

The section moment of inertia I and the section resistance moment W of the panel are :

     I = 10 × 18 ³ / 12 = mm ⁴ ;

      W = 10 × 18 ² / 6 = mm ³ ;

1. Load calculation and combination

(1) The large side pressure G _{4k of the} new pouring effect on the formwork

Calculate by the following formula and take the smaller of them :

        F ₁ =0.22γtβ ₁ β ₂ V ^1/2

        F ₂ = γH

Wherein γ - gravity density concrete, taking 24.000kN / m ^{. 3} ;

     t -- The initial setting time of the new pouring can be taken according to the actual value of the field. When inputting 0 , the system calculates according to 200/(T+15) and gets 5.714h ;

     T - concrete formwork temperature, take 20.000 ° C ;

     V - concrete pouring speed, take 1.500m / h ;

     H - the total height of the top side pressure calculation position to the top surface of the new pouring, taking 4.300m ;

     β ₁ -- admixture affects the correction factor, taking 1.000 ;

     β ₂ -- slump affects the correction factor, taking 1.000 .

Calculated according to the above two formulas:

  F ₁ =36.952 kN/m ²

 F ₂ =103.200 kN/m ²

According to a large number of experimental studies at home and abroad, when the height of the formwork is > 2.5m , the large side pressure F ₃ = 50 kN/m ² ;

The new side pressure acting on the formwork is G _4k =min ( F ₁ , F ₂ , F ₃ ) = 36.952 kN / m ² ;

Effective head height of the helium side pressure: h=F/γ=36.952/24.000=1.540m ;

(2) Standard value of load Q3k generated when dumping sputum

Q _3k = 2kN/m ² ;

(3) Determine the load combination used

Calculate the deflection using a standard combination:

    q=36.952×1=36.952kN/m ;

Calculate the bending moment using the basic combination: q = max ( q1 , q2 ) = 46.661kN / m ;

    Combination controlled by variable load effects:

        Q1=0.9×(1.2×36.952+1.4×2) ×1=42.428kN/m ;

    Combination controlled by permanent load effects:

        Q2 = 0.9 × (1.35 × 36.952 + 1.4 × 0.7 × 2) × 1 = 46.661 kN / m ;

The column die is unfolded, the pressure of the poured concrete side is loaded, the fixed card (steel strip) bearing is set at intervals of 300 mm , the 8.8 steel screws are arranged one for each steel strip, and the formwork panel is calculated according to the one-way plate (the ratio of long and short sides is greater than 3) ), each span is simplified into a simply supported beam, taking a 10mm calculation unit, q=460661x0.01=0.47KN/m. The calculation diagram is as follows: