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EXAMPLE OF CALCULATION OF REINFORCED CONCRETE BEAM SPANS FOR TEMPORARY (A-14 and NK-100) AND PERMANENT LOADS
Toxir Yusupovich Radjabov
Senior teacher of "Road engineer" faculty, Transport university of sate Tashkent, toxirry@mail.ru
Akbar Turg'unboyevich Ergashev
senior teacher of "Road engineer" faculty, Transport university of sate Tashkent, eakbar71@mail.ru
Ilhomjon Yusufjonovich Mirzaolimov
senior teacher of "Road engineer" faculty, Transport university of sate Tashkent,
mirzaolimov9025@mail.ru
Abdulaziz Ikhtior ugli Karshiboev
assistant of "Road engineer" faculty, Transport university of sate Tashkent, laziz_22_92@mail.ru
Abstract: An example of the computation of reinforced concrete beam spans for calculated temporary (A-14 and NK-100) and permanent loads was given in the article. Bridges are built to withstand a variety of loads, each of which consists of a mix of permanent and live loads.
Keywords: superstructures, unified, assembled, in bundles, end beams, protective layer, waterproofing, concrete protective layer, crowd.
There are currently two methods for calculating forces in spans due to the impacts of permanent and temporary loads.
Bridges are built to withstand a variety of loads, each of which consists of a mix of permanent and live loads.
Loads are divided into permanent and temporary.
1) Permanent loads - the own weight of the beams of the superstructure and the joints between them, the own weight of sidewalk blocks and railings, the own weight of the clothes of the driving deck and sidewalks.
2) Live loads - impact from rolling stock, pedestrians, and wind loads.
When roads cross natural or man-made impediments, structures should be designed to withstand the following live loads:
AK - Normative load from automobiles.
NK - A specific mode was used to pass the normative load from non-standard vehicles.
The bridge dimension is D-8+2x1.0. Design loads A-14 and NK-100. The span beams, support elements and other reinforced concrete structures are adopted unified according to the current standard designs.
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• The reinforced concrete bridge is designed according to the monitor 18+24m+24m+24 +18m.
total bridge length is 108,76 m.
The accepted dimension of the bridge is D-8+2*1. The bridge dimension is designed in accordance with the requirements of SRDC 2.05.03-12. Roadway width is 6 m Safety lane width is 1,0 m Width of sidewalks is 1 m
The 1.23m high cross section is made up of 6 T-beams with prestressed reinforcing. Superstructure of reinforced concrete integrally carried beams 24 and 18 meters long, strengthened with horizontal beams. Concrete of B35 class, longitudinal prestressing reinforcement of B-1400 class, and non-prestressing reinforcement of A-540 class.
51 E>2 B3 B 4 B5 bb
Cross section of the bridge spans structure.
For individual beams, the designation B1, B2 ... B6 is accepted. Formwork dimensions of the beams of the superstructure in relation to the standard project of the series 3.503.1-81.
The span's beams are joined by embedding the 30cm wide longitudinal seams of the loop joint, which links the flanges of contiguous beams along the whole span. The intermediate beams have reinforcing ports on both sides on the side surfaces of the top shelf's overhangs to accomplish this. For their connection with the intermediate beams, the end beams feature strengthening protrusions on one side. Barriers and railings are installed on the superstructure's extreme beams.
The bridge deck is dressed as follows: a 3cm thick leveling layer of class B25 concrete reinforced with a wire mesh with a diameter of 2.5mm is applied to the upper surface of the superstructure beams, followed by a 7cm thick two-layer asphalt concrete coating. Load class A14 in accordance with point 4.1 [2]
P=14 thou; V=1,4 thou
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UXUii, / iliilli . 1.5 X uuuu
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1.9
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Load diagram A14 Load class NK100.8 in accordance with point 4.1 [2]
P=25 thousand
kMkMi .........J
0.2
Load diagram of NK-100.
Reliability factors for load in accordance with the table 14[1]
a. Load A14
b. yTSJJ=1,5; Yf=1,2
c. Load NK-100,8.
d. yTSJJ=1,0
Dynamic coefficients applied to the load from the rolling stock in accordance with paragraph. For load A14
45 - A
1 + ¡u = 1 + , where X is loading length
1 + u = 1 + 45^A= 1,16
135
For load NK-100,8
1+ p.=1,10 at X>5,0 m; For NK100 moving string, a reduction factor is applied yKOJ=0,75
The standard live load for pedestrian sidewalks (from the crowd) according to point is calculated by the formula:
p=400-2 X >200 kgf/m2 X - distance between the axes of the supporting parts of the beam.
p=400-2x23,4=353,2 kgf/m2 Calculation of intermediate support:
We accept a support in the form of a frame pinched at the level of the top of the base (line of local erosion). The calculation scheme of the frame is divided into finite rod elements. Calculation of the own weight of the sidewalks of the carriageway and sidewalks The bridge deck consists of:
• Leveling layer of concrete B25
• Waterproofing
• Protective layer of concrete
• Asphalt concrete sidewalks
Sn. M=13,5m*23,4m=315,9 m (total surface area of the bridge) 1) Leveling layer of concrete:
hb=0,03 m; p=2,5 t/m3
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2) Waterproofing:
q= p hb Sn. m=2,5xQ,Q3x315,9=22,27 t
hb=0,04 m; p=1,5 t/m3
q= p hb Sn. m=1,5xQ,Q4x3 15,9=18,95 t
3) Protective layer of concrete:
hb=0,04 m; p=2,35 t/m3
q= p hb Sn. m=2,35xQ,Q4x315,9=29,69 t
4) Asphalt concrete sidewalks:
hb=0,07 m;p=2,3 t/m3
5) Metal fence:
q= p hb Sn. m=2,3xQ,Q7x315,9=5Q,86 t q= Q,Q42x23,4=Q,91 t
on both sides =1,96t
Table 1. Normative and calculated constant loads from the weight of the bridge span coating.
Layers Regulatory loads Reliability factor Design loads
Leveling layer of concrete 22,27 qH = = 0,07 t/m2 315,9 Y=1,3 qp=0,07x1,3=0,0916 t/m2
Waterproofing 18,95 qH = = 0,06 t/m2 315,9 Y=1,3 qp=0,06x1,3=0,078 t/m2
Protective layer of concrete 29,69 qH = = 0,094 t/m2 315,9 Y=1,3 qp=0,094x1,3=0,122 t/m2
Asphalt concrete sidewalks 50,86 qH = = 0,161 t/m2 315,9 Y=1,5 qp=0,161x1,5=0,241 5 t/m2
Metal fence 1,96 qH = = 0,0062 t/m2 315,9 Y=1,1 qp=0,0062x1,1=0,00 68 t/m2
Iq XqH=0,391 t/m2 Xqp=0,54 t/m2
Temporary (normative and design) loads Load A14 according to point 4.1 [2] Axle load is 14 thousand (P)
Uniformly distributed load from the track is 0,1* 14=1,4 thousand (V)
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Table 2.
Type of load Normative for per wheel Estimated per wheel
Spot from per wheel P/2=7 thou P/2=7x1,5x1,16=12,18 thou
distributed along the span V/2=0,7 thou V/2=0,7x1,5x1,16=1,21 8 thou
Crowd load (A14):
p=400-2x23,4=0,3532 thousand/m2 qH=0,3532 tc/ m2 yf=1,2 qp=0,3532x1,2=0,42384 thousand/m2 Load NK-100.8 according to point 4.1 Axle load is 25,2 thousand (P)
Table 3.
Type of load Normative for per wheel Estimated per wheel
from per wheel P/2=12,6 thou P/2=12,6x1,1=13,86 thou
Estimated constant load on the support elements
The calculation of loads is carried out taking into account the requirements of design standards.
1. Uniformly distributed load from the weight of the support:
qon=YfxnxR2xv=1,1x3,14x0,752x2,5=4,86 thousand/m.
R - support radius;
yf - load safety factor;
v - bulk density of reinforced concrete.
2. Uniformly distributed load from the weight of the crossbar:
qp=bxhx yf xv=1,25x0,7x1,1x2,5=2,4 thousand/m.
b, h - cross section.
3. Self weight of the extreme beams of the superstructure:
fk=( f5k+ FMK)yf =(39,4+1,48)x1,1=44,97 thousand. FMK - weight of the monolithic section of the extreme beam; FgK - the weight of the edge beam without a monolithic section.
4. Dead weight of intermediate beams:
Fn=( Fsn+ FMn)yf =(37,23+2,96)x1,1=44,21 thousand. FMn - weight of the monolithic section of the intermediate beam
5. Sidewalks and metal railing load:
FTp=qTpxLx yf =0,57x24x1,1=15,1 thousand.
L - span length (beams).
Fn=qnxLx yf =0,042x24x1,1=1,1 thousand. qTp, qn - the weight of one linear meter of the sidewalk and railings.
6. Base load:
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Pgch=PgxLx yf =0,28*24*1,3=8,74 thousand. 7. Load from asphalt concrete sidewalk:
Pac$=pa*L* yf =0,25*24x1,5=9 thousand. The total load transmitted from the extreme beams to the crossbar:
F=Fn+PocH+Pac$=44,97+8,74+9=62,71 thousand.
For intermediate beams:
F=Fn+PocH+Pao$=44,21+8,74+9=61,95 thousand.
Estimated wind load
According to SRDC 2.05.03-11 "Bridges and pipes", the normative intensity of the horizontal
2 2 transverse wind load should be taken at least 180 kgf/m (w=0,18 thousand/m ).
The wind load is applied to the bridge support in the form of a concentrated force W collected from
the cargo area:
W=w*Lx yf =0,18*24x1,5=6,48 thousand. The normative horizontal transverse load from impacts of the wheels of vehicles is taken as a concentrated force applied at the level of the top of the carriageway. P=0,6xK=0,6x 14=8,4 thousand. The design load is: P=P*yf=8,4*1,2=10,1 thousand. Estimated braking load
The normative longitudinal braking force from vehicles is assumed to be 2.5 K. Estimated force from vehicle braking:
T=2,5xKxyf=2,5x14x1,2=42 thousand. T _ 42 3 " 3
The load is applied at the level of the top of the support. Estimated load on the sidewalks from the "crowd"
The load from the sidewalks on the intermediate support is determined in accordance with point 2.21 of the norms. The design load is:
= 14 thousand
RTp=qn*bxLxyf=0,4x 1 x24*1,2=11,52 thousand. qn - normative temporary load on the sidewalk; b - sidewalk width; yf - load safety factor.
REFERENCES
1. SRDC 2.05.03-12 Bridges and pipes.
2. N.D. Livshits, M.M. Onishchenko, A.A. Shkuratovsky "Examples of calculation of reinforced concrete bridges". «Visha shkola» - Kyiv, 1986- p.260
3. Mirzakhid Miralimov, Shahboz Normurodov, Mirali Akhmadjonov and Abdullaziz Karshiboev Numerical approach for structural analysis of Metro tunnel. E3S Web of Conferences. (2021), https://doi.org/10.1051/e3sconf/202126402054
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