Let me take the lead in talking about some common ways to cut corners in steel bar engineering! Mainly manifested in the following points:
1, there are often 1~2 encryption hoops at the joint of frame column and beam, and some of them only have outer hoops without inner hoops;
2. The multiple of beam steel binding joint is insufficient, and the 90-degree anchorage length of beam steel end is insufficient;
3. The number of slab reinforcement is often less than 1, and the anchorage length of slab reinforcement extending into the beam is insufficient;
4, column, beam encryption area stirrup often less1;
5, stirrup hook straight length is not enough, hook arc diameter is not big enough;
6. The length of Rachel reinforcement in the wall is insufficient;
7. There are no encryption hoops at the upper and lower ends of the constructional column.
Let's talk about these first! I hope these means can attract the close attention of on-site quality inspectors or supervisors! ! !
Large-scale projects invested by the state dare to cut corners, not to mention small projects, such as few anchor rods in tunnel construction, little or no shotcrete, underground subway tunnel construction, in order to save money, small pipes are not grouted, steel frame spacing is increased, and soil nailing walls for foundation pit support are not grouted. Too numerous to mention! ! !
Let me say something. I think there are three reasons why the construction market cuts corners so badly and there are so many tofu.
1, the owner always likes to win the bid at the lowest price, sometimes even ridiculously low. This is the only way for the construction unit not to lose money.
2. In the process of winning the bid, coupled with a large number of shady situations in the construction process, bribery is inevitable. Now some corrupt officials have a big appetite and have to recover their money.
At present, the competition in the construction market is very fierce. Public units want performance and private units want profits, so they are not too short of money.
Next, let's talk about ways to cut corners:
Generally speaking, the key parts of the project are rarely adulterated, and the less important parts like adulteration. When pouring concrete, add stones, install less steel bars, or simply replace them with smaller steel bars. For example, there are many patterns of hanging nets and shotcreting anchors on highway slopes. The design of the anchor is 6.7m, and only1.2m can be driven during construction. In addition, rubble concrete was originally set at 25%, and 75% will be invested when it is built. Because the unit price opened by the owner is too low, especially some concealed works are very presumptuous in construction: foundation pit excavation is not in place (tower ruler moves during elevation measurement) and mortar is porous ("building a house"). If it is a raft foundation with steel mesh on it, it is quite difficult to put rubble.
It can be said that there is some truth. In fact, reducing cement can reduce the heat of hydration, while stone can absorb relatively large heat, but it must be approved by the design.
Speaking of cutting corners, the number of piles in many constructions can't meet the design requirements, but the piling records are generally ultra-deep, which is the most common phenomenon. There is also a fence, and the steel bars used in the components are smaller than designed. The label of concrete and mortar is not enough!
The risk of piling cannot be taken casually. Do you know the cost of reinforcement? It is 10 times that of piling. Why bother?
The decoration company cheated the owner by cutting corners like this:
1, when plastering marble, the selected stone is made in China, deceiving the owner that it is foreign, and the thickness of the stone is thinner than the design 1 ~ 5 mm, which can save the material cost of 50 ~ 200 yuan/square meter.
2, take cover engineering to cut corners. Choose inferior materials to fill the quantity.
Nearly 30 netizens participated in the discussion, but there was a classic example of cutting corners, which everyone didn't mention. The code allows deviation to cut corners. Using the negative error allowed by the code, we can basically cut corners on all materials, such as broken steel bars and small-section concrete. People upstairs in .................................................................................................. just noticed the stones, but they can do it.
It is normal to hit mass concrete riprap, in order to reduce cement consumption, reduce hydration heat and avoid temperature cracks. Some supervision laymen say that this is impossible, but it is actually possible, but there are requirements for the volume and quantity of rubble.
In addition, there used to be an old saying in the construction industry: use less brains and put more steel bars. If it is a state-owned enterprise, technicians will not pay for this thing because it is impossible; The money saved is not your own. If something goes wrong, the responsibility is your own. Is there such a stupid person? Private enterprises, however, are generally not like this now. This was just started a few years ago. In the last audit, in a private construction enterprise in Dongguan, the boss said, I'd rather add dozens of kilograms of cement to one side of concrete, and I also want to ensure that it passes at one time when it rebounds, otherwise the second rebound will cost 2000 yuan, so I can buy 5 tons of cement.
Now chaotic places, the government's inspection is gradually strict, which can reduce the responsibility and increase the fees. Why not? Therefore, it is generally not to reduce costs in this way, with little effect, but to increase risks.
At present, the general method to reduce the cost is to directly reduce the cost by optimizing the design under the condition of constant total price. There is also the application of the futures principle. When the price of materials rises, it will sign a contract, and when it falls, it will buy materials. This is similar to the recent situation, and only the boss with high prediction level is possible.
So this question was raised 10 years ago, which is a good topic. Now!
In my unit, flaky is the most mixed in the construction of tunnel inverted arch. In fact, there is no need to do an inverted arch at that mileage. The design unit was too conservative and asked for inverted arch, which made us make a lot of money for nothing. That's how our bonus came from.
The second secret of making a fortune for construction units:
My unit is building a tunnel, and the construction contract is not clear about how to use it. What should I do if I pull it out and fall down, and I have to pay for the car and rent the land? Let's see what you have to say.
Get a set of gravel equipment to produce gravel, and then use gravel to beat concrete. However, gravel should be tested for concrete mixture ratio first.
Yes, the production of gravel can reduce the burden, especially when the price of building materials rose last year. But there is enough gravel, so we will sell gravel. If you still can't digest it, sell stones, that is, pond slag, 55 yuan/car. If we stop selling soil, it will be very expensive.
I think the most common way to cut corners in construction projects is in the foundation. Generally, the cushion is very little 10 cm, and the soil on both sides is dug deeply. It looks like 10 cm, and 5 cm is good. In fact, it's hard for you to steal the superstructure. It is much stricter now than it was ten years ago.
I've seen many things to cut corners. Let's talk about what I saw last time on the construction site of a private contractor. When the cast-in-place slab is poured, someone is responsible for watching the wind, and then the boss organizes two migrant workers to dismantle some floor reinforcement. Everything was done in the dark. Of course, the boss is also an expert, knowing that the design is conservative and afraid to move the beams and balconies. At that time, the thickness of the floor was still being considered, and the platform was often one centimeter high when supporting the floor bottom formwork, which could save a lot of concrete. However, everyone who works on site knows that there are too many embedded pipelines in the cast-in-place floor slab, which are intertwined with each other, and sometimes it is really difficult to save concrete.
I found that the worst way to cut corners is piling. Gravel shall be poured under the C25 concrete cast-in-place pile of 30m, and then C 10 concrete shall be used for coming up10, and C25 shall be used only after reaching the top two meters. The dynamic tester can't understand the dynamic test waveform, and finally the truth comes out when the core is sampled. Enough NB
It is also necessary to measure the spacing and thickness of steel bars and rebound. In case one item does not meet the requirements, it may not be enough to make up the stolen money. Why bother? And if everything is done according to the norms, it will die quietly. Everyone knows that the information is false, but I still have to, hehe, I don't understand.
I have seen the disadvantages of anti-slide piles. They didn't dig enough when they dug the hole, and it would be even worse if they fell down. The design is that C25 concrete can reach C20, so it is very kind and adds flaky.
Subgrade filling is also a place to cut corners. The lower part of the large fill is generally a place with relatively large stones and too few rolling variables. Only on the top floor, it is filled according to the standard particle size.
In fact, the construction unit cannot cut corners. For example, according to the budget, our bidding will drop 15% ~ 20%. Think about how much profit there will be. Therefore, in order to improve the management level in construction, we have to cut corners.
1, the encryption area is not in place, basically one hoop gold is missing.
2. The thickness of flaky, crushed stone and cushion is only half.
3. Backfill soil is not compacted as required.
4. In the enclosure structure, if wooden stakes are used, the radius is basically much smaller and the length is not ditch.
5. Brick walls and exterior walls need not be covered with ashes, and Rachel bars are not in place.
6. The mortar tongue at the constructional column is not cleaned.
…………………………
There are more than n, anyway, there are many procedures, hehe, because if they all follow the specifications, the construction unit will have to drink northwest wind, and many people want to close their eyes.
In the process of cutting corners in concrete, the thickness of the slab is basically guaranteed within the specification range, because it needs to be tested, but it must be less than 0.5cm, and the Liang Kuan is about 0.5 ~ 0.7 cm smaller, so it can be measured during formwork installation.
I have read several posts saying that the stirrup in the encrypted area is not in place. I think it's actually the responsibility of the site management. This part is difficult to construct, and your management is not in place. Of course, he didn't add stirrups when it was so difficult. Sometimes the project leader doesn't know. Here's what I did: when the bottom bar of the beam reinforcement is in place, I put the stirrup on it and put it down together after the beam reinforcement is in place. At most, I just missed a few irons.
In the case of mass concrete in engineering, design and construction specifications allow riprap, which is beneficial to concrete, helps to reduce hydration heat and prevent cracks in concrete.
If you cut corners, cast-in-place piles and deep mixing piles are probably the easiest to be stolen, and there is usually little cement under them.
I just found this post and read everyone's message. I think it mainly focuses on two aspects: mixing flaky in concrete and pile foundation construction. In fact, sheet concrete is commonly used in mass concrete construction as long as it does not violate the requirements of relevant codes; Personally, I think it is unwise to tamper with the pile foundation, because it will leave hidden dangers for the project. If an accident happens after the building is put into use, many innocent people will be hurt. Even if you used various means at that time, you couldn't escape punishment for something.
After reading all the posts, almost all of them are discussing the problems of steel bars and mass concrete. There are many cuts in construction, the most common one is to cut corners in backfill soil, and the fertilizer tank several meters deep is directly pushed by bulldozer. The proportion of pseudo-ginseng lime soil is a child's play, so it can't be done during the day and backfilled secretly at night.
The above-mentioned people mainly discuss cutting corners during the main construction. For us, this kind of thing is generally not done in structural construction; According to the main materials in the structure construction stage, the common methods are:
1, reinforcement: increase the spacing and reduce the specifications. Our design safety factor is relatively large.
2. Concrete: According to the design strength grade of the first few cars of commercial concrete, it is hard to say about the later concrete.
3. Timber, formwork and supporting system: speed up the material turnover, and dismantle the formwork in advance during roof construction.
The commonly used technologies in the decoration stage are as follows
1, do Party A's design work, improve the grade of decoration materials, and increase the price accordingly.
2, confirm the material price for the owner, forcing each subcontractor to raise the price, and the general contractor will eat the material price difference.
All the above are common practices of construction units, not to mention cutting corners!
Especially for cast-in-place piles, the design strength is C30, and it is a fool not to steal them. C 10 C30 in the middle and C30 in the upper part are thinner, and the reinforcing cage is shorter.
Just came out, what I know at present is to make a fuss about steel. Many of them are listed steel bars (good brands of steel tied with a wire casually), and according to the test report, they are close to the critical point. But more than 20 main bars are fake or less, usually round steel.
There are many ways to cut corners in that project. Cushion the ground gravel cushion. 15cm，7-8cm。 The supervision of concrete mixture ratio is different. If the foundation is watered less, you can't see anything as soon as you borrow the soil.
Generally speaking, on the bridge, abutment and pile foundation are the easiest places to cut corners. If the amount of gravel on the abutment is not well controlled, it will be reduced by half if you don't pay attention, and the pile foundation is also a concealed project, which is easy to be careless.
Cement, stone, steel bar, etc. They are all cutting corners, changing the mix proportion, reinforcing steel bars and other objects. Can achieve the "effect". But modern architecture is still changing and unpredictable.
There are many ways, such as the house built a few days ago. The children's room and the master bedroom should have lattice stereos, but our company only used one cabinet to open it, so we signed a contract to save money. But I asked the boss this question, and the boss said the contract was settled, so as a designer, I had to listen to him. ................
1, as well as site supervisors, reduce the cement grade in unimportant parts.
2. Unqualified materials are mixed with qualified materials.
The most easy parts to cut corners: cushion of pile foundation (flaky, plain concrete), concrete label (i.e. in the case of self-mixing), exterior paint for plastering internal and external walls, latex paint (brush less once or twice), ground engineering, roof waterproofing and so on.
There are still a few points that the above friends have not mentioned.
1, the foundation cushion often fails to reach the elevation, that is, it is not deep when digging, so it can save a lot of volume and materials when building concrete;
2. The story height did not meet the requirements, mainly stealing concrete;
3. The floor thickness does not meet the requirements. Although there is testing now, the quality supervision station requires the construction unit to drill holes first, so the construction unit can make fraud here. Add a little if it is thin, and chisel a little if it is thick, so there is no problem of floor thickness deviation during the test.
4, the material can also be fake, with good materials to test, the actual use of inferior goods. I can't tell from the outside.
When pouring the ground, it was clearly designed as a gravel cushion, but he used construction waste as a cushion. Now 60 yuan spends 1 ton of gravel, while the construction waste only needs 10-20 yuan per ton.
The emery ground is obviously 5 mm thick, but it is only 2-3 mm or even thinner, so that it is exposed to the ground in less than half a year.
Exterior wall coatings are widely used, and the cost is 30-40 yuan/kg. The exterior wall coating of high-rise building was not diluted according to the proportion of product description, and it was brushed once or twice less, resulting in insufficient film thickness. Due to height, general supervision is not in place.
If the design drawings do not clearly explain the purpose of rubble concrete, and the construction party puts a lot of rubble into the concrete, it is an out-and-out Jerry-building behavior! Do you think so?
It depends on the actual situation of the construction site. If there is a large amount of concrete during construction and the weather is very hot, in order to reduce the hydration heat of concrete, the construction unit will formulate the construction organization design of on-site cast concrete according to the actual situation, which will be approved by the supervision unit without considering cutting corners.
Thank you. This is my opinion. I don't know if it's right.
During the inspection, I saw that many buildings were caused by poor construction quality. For example, the buttress retaining wall, the original design plate was 400MM, but actually it was only 200MM, and the diameter of pebbles in concrete was 180 mm, which collapsed in the rainstorm!
The steel content of the new design code in 2002 is more than 20% higher than that of the old code. I saw that the stirrup of a four-meter five-span beam in our project is actually 14 diameter. Is it necessary to be so big? Regardless of the cost, the design unit will not pay for it anyway. A 450×450 column uses 12 tendons. In the past, as many as 8 tendons were designed according to the grade limit theory. I don't know if the economy is developed now, and money can't be spent anywhere. As a construction unit, it really hurts me to watch dozens of tons of steel used in one project.
I think everyone knows something about structure. In fact, this design was safe enough before the 2002 version of the code. Take the strength of steel as an example. The design strength of secondary steel is 2 10 MPa, and the actual tensile strength can reach 260. The design tensile strength of Grade III steel is 365,438+00 MPa, but it is usually 360-370 MPa. Under load, the dead load coefficient is 1.2, the live load coefficient is 1.4, and the concrete reduction coefficient is 0.8, which is also safe.
If the construction is carried out according to the specifications, it is absolutely safe and there is no problem of reduction at all.
But I want to say that in the main structure, you'd better not think about steel bars. Losing a steel bar has a great influence on stress. If there is no spectrum, it is best not to move the steel bar. Our construction units here rarely steal steel bars, but basically steal cement. C20 concrete is generally mixed according to C 13, and there is no problem. Decoration engineering plastering mortar has low mixing ratio and less cement consumption. As long as the workmanship is excellent and there is no sand, the appearance will be very acceptable. Generally speaking, some construction units can steal 1000 tons of cement for a project of more than 5,000 square meters. /kloc-how much is 0/000 tons of cement? You can figure it out. This is not a small sum.
C25 concrete in our construction site can reach about 40Mpa, so they can lower it a little and dare not take risks. State-owned enterprises are like this, but they don't save themselves.
I would like to say a few words I've just been on the construction site for two years, and I've seen this kind of thing many times. Our earthquake crack is 6 degrees. In a small house with four units, 28 structural columns are fake. Insert when laying bricks, and lift with tower crane when pouring concrete. Of course, they are behind the supervision. Twenty-eight steel cages were put behind the seventh floor.
Isn't that sick? These 28 cages can't be used in other places, and the remaining four cages are cost-effective.
I saw that when the construction unit laid the subbase on the road, it did not follow the required gradation, and adopted a gradation much larger than the design, thus saving concrete. ..............................