How to calculate the number of steel bars in reinforced concrete foundation?

Summary of basic methods of reinforcement calculation

I. Cross beam

(1) frame beam

A, the calculation of the first span reinforcement

1, upper rib

Length of upper piercing reinforcement (upper piercing reinforcement 1) = span clear distance+anchorage value of head and tail support.

2. End bearing negative reinforcement

Length of negative reinforcement of end bearing: the first line LN/3+ anchorage value of end bearing;

The second line is the anchorage value of LN/4+ end brace.

3, the lower reinforcement

Lower reinforcement length = clear span length+anchorage value of left and right supports

The above three types of steel bars all involve the bearing anchorage problem, so summarize the bearing anchorage judgment problems of the above three types of steel bars:

The bearing width ≥Lae and ≥ 0.5hc+5d is the straight anchor, and Max{Lae, 0.5hc+5d} is taken.

Anchorage value of steel bar end bearing = bearing width ≤Lae or ≤ 0.5 HC+5d, which is bending anchorage, and Max{Lae, bearing width-protective layer+15d} is taken.

Anchorage value of middle support of steel bar = =Max{Lae, 0.5hc+5d}

4. Lumbar tendon

Structural reinforcement: structural reinforcement length = clear span length +2× 15d.

Torsional reinforcement: The algorithm is the same as that of penetrating reinforcement.

5, lacing

Support length = (Liang Kuan -2× protective layer) +2× 1 1.9d (seismic hook value) +2d.

Number of lacing bars: If we don't give the spacing of lacing bars in the plane input, then the number of lacing bars = (stirrup number /2)× (structural reinforcement number/2); If the lacing spacing is given, the lacing quantity = lacing length/lacing spacing.

6. stirrup

Stirrup length = (Liang Kuan -2× protective layer+beam height -2× protective layer) * 2+2× 1 1.9d+8d.

The number of stirrups = (encrypted zone length/encrypted zone spacing+1) × 2+ (unencrypted zone length/unencrypted zone spacing-1)+ 1.

Note: Since the components are buckled on the skin of longitudinal reinforcement when the protective layer is deducted, we can find that the diameter values of lacing and stirrup are deducted at each protective layer; When we calculate the length of steel bars in the budget, it is calculated according to the skin, so the software will automatically supplement the extra deducted length. Therefore, the reinforcement calculation is increased by 2d and the stirrup calculation is increased by 8d.

7. Steel hanger

Length of steel hanger = 2 * anchorage (20d)+2* length of inclined section+width of secondary beam +2*50, in which height of frame beam >; Angle of 800mm = 60; Angle ≤800 mm = 45

Second, the calculation of mid-span reinforcement

1, negative reinforcement of intermediate bearing

Negative reinforcement of intermediate bearing: the first row is: ln/3+ intermediate bearing value+ln/3;

The second line is: ln/4+ intermediate orientation value +ln/4.

Note: When the sum of the protruding lengths of the negative reinforcement of the bearings at both ends of the span is greater than or equal to the net span length of the span, the reinforcement length is:

The first line is: the net span length of the span +(ln/3+ the value of the front intermediate support) +(ln/3+ the value of the rear intermediate support);

The second line is: the net span length of the span +(ln/4+ front intermediate support value) +(ln/4+ rear intermediate support value).

Other reinforcement calculation is the same as that of the first span. LN is the larger value of the span on both sides of the bearing.

Second, other light beams

I. Non-frame beam

In 03G 10 1- 1, the simple description of non-frame beam reinforcement is different from that of frame beam reinforcement:

1, no longer distinguish between encrypted area and non-encrypted area when setting stirrups for ordinary beams;

2. Only need12d; Which is used for anchoring the lower longitudinal reinforcement into the support;

3. The upper longitudinal reinforcement is anchored into the bearing, and the judgment value of 0.5 HC+5d is no longer considered.

Please refer to the description of 03G 10 1- 1 for further explanation.

Second, the frame-supported beam

1, the length of negative reinforcement of frame-supported beam support is ln/3;

2, the lower longitudinal reinforcement end bearing anchorage value processing with frame beam;

3. The anchorage length of the end support of the first row of main reinforcement in the upper longitudinal reinforcement = support width-protective layer+beam height-protective layer +LAE, and the anchorage length of the second row of main reinforcement ≥ LAE;

4. The steel bar in the middle of the beam extends to the horizontal straight anchor at the beam end, and then bends laterally15d; ;

5. The stirrup encryption range is ≥ 0.2ln1≥1.5hb;

7. The transverse structural reinforcement and torsional reinforcement shall be treated in the same way as the frame beam.

Second, the shear wall

Shear wall is the most difficult component in the calculation of reinforcement quantity, which is embodied in:

1, shear wall includes wall, wall beam, wall column and hole, and their relationship must be considered as a whole;

2. Shear walls have various forms of corner on the plane, such as right angle, T-angle, cross angle and oblique angle.

3. The shear wall has various openings on the facade;

4. There may be single row, double row and multiple rows of wall reinforcement, and each row of reinforcement may be different;

5. The wall column has a variety of stirrup combinations;

6. The coupling beam distinguishes between the top layer and the middle layer, and there are different calculation methods according to the position of the hole.

(1) shear wall body

A, shear wall wall horizontal reinforcement

1, when the wall end is a hidden column.

A, transverse reinforcement continuous through the transverse reinforcement length = wall length-protective layer

Internal reinforcement = wall length-protective layer+bending

B. The length of transverse reinforcement intermittently passing through transverse reinforcement = wall length-protective layer+0.65LAE.

Internal reinforcement length = wall length-protective layer+bending

Number of horizontal reinforcement = height/spacing+1 (horizontal reinforcement for concealed beam and coupling beam shall be installed)

2. When the end of the wall is an end column.

A, transverse reinforcement continuous through the transverse reinforcement length = wall length-protective layer

Internal reinforcement = net length of wall+anchorage length (bending anchor, straight anchor)

B. The length of transverse reinforcement intermittently passing through transverse reinforcement = wall length-protective layer+0.65LAE.

Length of internal reinforcement = net length of wall+anchorage length (bending anchor, straight anchor)

Number of horizontal reinforcement = height/spacing+1 (horizontal reinforcement for concealed beam and coupling beam shall be installed)

Note: If the shear wall has multiple rows of vertical reinforcement and horizontal reinforcement, the anchoring measures of the middle horizontal reinforcement at the corner are the same as those of the horizontal reinforcement inside the wall.

3. When the shear wall is opened.

When there is a hole in the shear wall, the horizontal reinforcement of the wall is cut off at the left and right sides of the hole and bent downward 15d respectively.

Second, the shear wall body vertical reinforcement

1, the longitudinal reinforcement length of the first floor wall = foundation steel dowel+height of the first floor+lap length extending into the upper floor.

2. The longitudinal reinforcement length of the middle wall = the height of this floor+the lap length extending into the upper floor.

3, the top wall longitudinal reinforcement length = layer clear height+top anchorage length

The number of vertical reinforcement of the wall = the clear length/spacing of the wall+1 (the vertical reinforcement of the wall is arranged 50mm from the edge of the concealed column to the end column).

4. When there is a hole in the shear wall, the vertical reinforcement of the wall is cut off at the upper and lower sides of the hole and bent laterally 15d respectively.

Third, wall bracing

1, length = wall thickness-protective layer+hook (hook length = 1 1.9+2 * d)

2. Root number = net wall area/lacing arrangement area.

Note: Clear wall area refers to the deduction of concealed column (end) and concealed beam (connecting beam), that is, wall area-total area of doorway-sectional area of concealed column-area of concealed beam;

The gluten area of lacing refers to its horizontal spacing × vertical spacing.

Example: (8000*3840)/(600*600)

(2) Shear wall column

First, longitudinal reinforcement

1, the longitudinal reinforcement length of the first floor wall column = foundation steel dowel+height of the first floor+lap length extending into the upper floor.

2, the middle wall column longitudinal reinforcement length = this layer height+into the upper lap length.

3, the top wall column longitudinal reinforcement length = layer clear height+top anchorage length

Note: if it is an end column, the top anchorage should distinguish between side, middle and corner columns, and distinguish between external reinforcement and internal reinforcement. Because the end column can be regarded as a frame column, its anchorage is the same as that of the frame column.

Second, stirrups: free combination calculation according to design drawings.

(3) Shear wall beam

I. Coupling beam

1, main reinforcement

Main reinforcement length of top-level coupling beam = hole width+left and right anchorage value LaE

Length of longitudinal reinforcement of middle coupling beam = hole width+anchorage value LaE on left and right sides

2. stirrup

For the top-level coupling beam, stirrups are arranged within the longitudinal reinforcement length, that is, n = ((lae-100)/150+1) * 2+(hole width -50*2)/ spacing+1(top floor).

The middle layer is connected with the beam, and stirrups are arranged in the hole, one on each side of the hole, that is, N= (hole width -50*2)/ spacing+1 (middle layer).

Second, the dark beam

1, length of main reinforcement = clear length of concealed beam+anchorage.

Third, the column

(A), the basic layer

A, column main reinforcement

Foundation steel dowel = thickness of foundation slab-protective layer+length of steel bar extending into upper layer+maximum {10d, 200mm}

Second, the stirrup in the foundation

The stirrups in the foundation only play a stabilizing role, which can also be said to prevent the steel bars from being scratched when pouring. Generally, the calculation is based on 2 (the software uses 3 as the base).

(2) Intermediate layer

A, column longitudinal reinforcement

1, KZ longitudinal reinforcement of middle layer = height-the height of the current layer protruding from the ground+the height of the previous layer protruding from the floor.

Second, the column stirrup

1, number of stirrups in KZ middle layer = n encrypted area/encrypted area spacing +N+ unencrypted area/unencrypted area spacing-1

03G 10 1- 1 central column stirrup encryption area is specified as follows.

1) The first column has three stirrup encryption zones, namely, the length of the lower stirrup encryption zone is HN/3; Max{500, column length dimension, HN/6} takes the upper part; Beam node range encryption; If the column is bound and overlapped, it needs to be encrypted within the overlapping range.

2) Stirrups of columns with more than one floor are respectively: the length of upper and lower stirrup encryption zone Max{500, and the length of column side HN/6 }；; Beam node range encryption; If the column is bound and overlapped, it needs to be encrypted within the overlapping range.

(3) Top floor

The top KZ is divided into corner column, side column and middle column due to different positions, so the top anchorage of longitudinal reinforcement of various columns is different. (See pages 37 and 38 of 03g 10 1- 1).

I. Corner column

Length of longitudinal reinforcement at the top of corner column:

I. Internal tendons

A, internal reinforcement anchorage length is:

Bending anchor (_Lae): beam height-protective layer+12,5

Straight anchor (_Lae): beam height-protective layer

Second, external strengthening

B, the anchorage length of transverse reinforcement is transverse reinforcement anchorage length = max {1.5LAE, beam height-protective layer+column width-protective layer}

The first layer at the top of the column: _ beam height-protective layer+column width-protective layer +8d (ensure that 65% extends into the beam).

The second layer at the top of the column: _ beam height-protective layer+column width-protective layer

Note: in GGJV8. 1, the anchorage length of internal reinforcement is bending anchor (_Lae): beam height-protective layer ++ 12d straight anchor (_ LAE); Beam height-anchorage length of reinforcement outside protective layer = max {1.5LAE, beam height-protective layer+column width-protective layer}

Second, the side column

Length of longitudinal reinforcement at the top of side column = clear height HN+ anchorage value of reinforcement at the top, so how to consider the anchorage value of reinforcement at the top of side column?

The anchorage of longitudinal reinforcement at the top of side column can be divided into internal reinforcement anchorage and external reinforcement anchorage:

A, the anchorage length of internal reinforcement is: bending anchor (_Lae): beam height-protective layer ++ 12d straight anchor (_Lae): beam height-protective layer.

B, the anchorage length of the outer reinforcement is _1.5lae..

Note: in GGJV8. 1, the anchorage length of internal reinforcement is: bending anchor (_Lae); beam height-protective layer ++ 12d straight anchor (_Lae); beam height-anchorage length of external reinforcement of protective layer = max {1.5LAE; beam height-protective layer.

Third, the central column

Length of longitudinal reinforcement at the top of central column = clear height HN+ anchorage value of top reinforcement, so how to consider anchorage value of top reinforcement of central column? The anchorage length of longitudinal reinforcement at the top of the central column is: bending anchor (_Lae): beam height-protective layer ++ 12d straight anchor (_Lae): beam height-protective layer.

Note: In GGJV8. 1, the treatment is the same as above.

Fourth, the board of directors.

In practical engineering, we know that slabs are divided into precast slabs and cast-in-place slabs. This paper mainly analyzes the reinforcement arrangement of cast-in-place slab. Plate reinforcement mainly includes: stressed reinforcement (unidirectional or bidirectional, single-layer or double-layer), load-bearing negative reinforcement, distributed reinforcement, additional reinforcement (corner additional radial reinforcement, hole additional reinforcement) and lacing (double-layer reinforcement supports the upper and lower floors).

First, the stress bar

In the software, the length of the stress bar is calculated according to the shaft network.

Length of reinforced bar = axis size+left anchorage+right anchorage+hooks at both ends (if it is Grade I reinforcement).

Root number = (axis length-deduction number)/rebar spacing+1

Second, negative reinforcement and distribution reinforcement.

Negative reinforcement length = negative reinforcement length+left bend+right bend

Negative reinforcement quantity = (reinforcement range-deduction)/reinforcement spacing+1

Length of distributed reinforcement = length of negative reinforcement arrangement range-negative reinforcement minus impairment.

Negative reinforcement distribution quantity = negative reinforcement length in negative reinforcement input interface/distribution reinforcement spacing+1.

Three, additional reinforcement (corner additional radial reinforcement, hole additional reinforcement), support reinforcement (double steel support on the lower level)

According to the actual situation, the length and quantity of steel bars can be directly calculated, and the calculation can also be input in the software by direct input method.

Chapter V Frequently Asked Questions

Why do we calculate the hook of 135o as 1 1.9d in the software when calculating the reinforcement?

In the stirrup calculation in our software, the value of 1 1.9D is actually the result of hook plus measurement difference. We know that the straight length of the hook is 10D, so the measurement difference should be1.9d. Let's deduce the origin of the measurement difference of1.9d.:

The result calculated according to the outer skin is1000+300; If calculated according to the centerline, it is:1000-d/2-d+135/360 * 3.14 * (d/2+d/2) * 2+300, where d is the minimum radius specified in the specification, and the following is subtracted from the front.

The blanking length of steel bar should be considered comprehensively according to the component size, the thickness of concrete cover, the adjustment value of steel bar bending and the increase length of hook.

Cutting length of straight steel bar = member length-protective layer thickness+hook increase length

B bending steel blanking length = straight bending length+oblique bending length-bending adjustment value+hook increase length.

C stirrup blanking length = stirrup inner diameter+stirrup adjustment value+hook increase length.