13 Nov 2019 Tags: column formwork concrete column forms
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:
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