The steel structure interlayer belongs to the secondary structure manufacture and installation, which is built according to the standard of “steel structure interlayer recommended by the Ministry of construction”.Q345B H-beam steel is selected as the main beam structure of sandwich steel structure.The main structure shall be laid with steel floor slab, and then reinforced concrete with a thickness of 120-200 mm.

Before the construction of steel structure, the horizontal height of the overall structure shall be measured (the accurate position shall be measured by the domestic advanced laser level instrument). If there is leveling layer, it shall be removed first. The purpose is to make the frame beam close to the bearing wall, which is conducive to the stress. Then, the accurate position of each bolt hole is drawn. After drilling the appropriate hole with the impact drill, the residual in the hole is clearedLime soil, implanted with chemical hose, drilling into chemical screw with electric tools, waiting for chemical reaction, solidification, generally more than 30 minutes in this period is the most appropriate.After curing time, tighten the frame, tighten the screw, and weld the screw stress spot to prevent the frame from loosening.

In the steel structure, I-steel is the main load-bearing beam, connecting the support points at both ends of the main beam. The construction of I-steel should be reasonable, which is the most stressed part of the whole structure construction. During the lapping process of the main beam, the position of the embedded steel plate should be removed first, the cement wall of the leveling layer should be removed, and then the embedded steel plate should be fixed. At the same time, the steps are basically consistent with the frame construction processNo more than 4mm, the main beam should be overlapped at a certain level, first electric welding, then reinforcement, and then full welding. The two ends of the main beam should be fully welded at 360 ℃, and the I-steel should be placed vertically with the same stress.

Construction of steel structure floor

1The steel structure frame shall be used to lay the galvanized formed steel floor, after laying, two layers of steel mesh shall be bound, and then the concrete shall be poured.

2When laying the steel structure sandwich floor with cement pressure plate, attention should be paid to the overlapping of both sides of the floor slab on the main beam of the steel keel, not at the empty place.When laying boards, it is better to leave 3mm expansion joints between boards, and use waterproof expansion construction glue as joint filler.Secondly, self tapping screws are used to fix the floor, and self tapping screws are used to fix the floor on the steel keel.Finally: after the floor is laid, it should be leveled with cement mortar

1、 Construction technical details and requirements:

1.First, measure and recheck the dimension;

2.Setting out shall be carried out after confirming that the dimension is correct;

3.The embedded steel connecting plate and the site setting out of node drawing;

4.Setting out and positioning of main beam structure and secondary beam structure;

5.Field welding, processing and drilling

Technical details: it is strictly forbidden to use gas cutting to open holes for embedded steel connecting plates, and drilling machine must be used for drilling.Industry technical specification requirements: the drilling diameter of embedded steel plate is allowed to be greater than or equal to 0.5mm of screw diameter.It is strictly forbidden to drill large holes for the sake of good construction.The main beam structure of steel structure mainly depends on the function of embedded joint plate at both ends of steel beam. If the anchor (anchorage is the reinforcement technology of building structure, belongs to a strong specialty, and its technology is stronger) is connected to the steel plate, when the bolt nut and the steel plate are fixed, the stress of the rigid joint plate will be greatly reduced, which can not meet the needs of the structure load;

6.Cutting and drilling of H-section steel of main beam: steel plate is used as wall surface of embedded parts, and steel beam link is made of embedded parts (steel plate is anchored by anchor bolt) with full welding.

2、 The steel structure frame is laid with galvanized formed steel floor, and then two layers of steel mesh are bound, and then concrete is poured.When laying the cement pressure plate, attention should be paid to the overlapping of both sides of the floor slab on the main beam of the steel keel, not at the empty place.When laying boards, it is better to leave 3mm expansion joints between boards, and use waterproof expansion construction glue as joint filler.Use self tapping screws to fix the floor on the steel keel.

3、 Specific construction process:

1.According to the drawing design and on-site prefabrication and production, all steel members shall be subject to all-round derusting, grinding and painting the second coat of antirust paint;

2.Use laser level to measure the highest point in the room, then find out the reference point, measure the horizontal line of steel structure, pop up the standard position line on the wall, and the error of the horizontal line position should be less than 3mm;

3.The back wall of the embedded steel plate shall be grooved and chipped (leveling layer), and the wall skin on the back of the frame shall also be removed. The purpose is to make the bearing solid wall closely connect with the frame, prevent the falling and moving, and more effectively bear the force.

4.Fixation of embedded steel plate: steps: 1. Drilling in the base material 2. Cleaning the hole, repeatedly blowing air and brushing dust 3. Placing the chemical anchor hose 4. Drilling in the screw 5. Hardening waiting 6. Installing the embedded steel plate;

5.Fixing the frame: steps: 1. Drilling the base material — 2. Cleaning the hole, repeatedly blowing air and brushing the dust — 3. Placing the chemical anchor hose — 4. Drilling into the screw — 5. Hardening and waiting —– 6. Installing the frame;

6.Installation of main beam; after arriving at the site, measure and anchor both ends for fine cutting, and cut after actual measurement. If the span is small, section steel shall be selected as far as possible, and the error shall not be greater than 4mm.Due to the limitation of site construction conditions, the construction machinery can not be accessed on site, and manpower is arranged to install it to the elevation of 3.7m.Four workers above and two workers on the ground are required to bind the steel beam with a 3-ton hoist and manually pull it up and install it.It is required to complete the hoisting in 5 working days with 10 teams of 3 tons of hoist and 6 manual workers.After the main beam is hoisted to the elevation shown in the figure, spot welding, reinforcement and full welding shall be carried out on the frame.7. Steel floor support plate installation.The lap of both sides of slab laying shall be overlapped on the main beam of steel keel, and shall not be overlapped in the empty place.When laying boards, it is better to leave a 3mm expansion joint between boards, use waterproof expansion construction glue as joint filler, and fix with self tapping screws.

4、 Difficulties in construction of steel structure interlayer 

In the sandwich construction site, the space is often narrow, the main beam is difficult to enter, and even after the outside is disconnected, the machine can not be easily used, and it is lifted after splicing by hand.

 1.Rooting

Rooting is one of the keys to sandwich safety. The so-called root is to radiate the load of the newly-built sandwich roof to the root through the main beam, and then transfer it from the root to the original structure. Like a big tree, a tree can’t stand without a solid root.

In the actual construction, the hardness of medium should be detected first.Thickness.For reinforcement, the main reinforcement shall not be interrupted during hole turning. The hole shall be rotated in strict accordance with the depth and diameter required by the process, and the anchor bolt shall be configured according to the roof load.Before the anchor bolt is implanted, the hole must be cleaned up, otherwise the anchoring strength will be seriously affected. If the rotation speed is not too fast, the drug mixing will not be complete, and if it is too slow, it will cause drug running, which will reduce the pulling force. After implantation, the construction can be carried out according to the temperature waiting time.In the manufacture of anchor plate, the anchor plate is a coupling part of anchor bolt. According to the total radiation load of main beam, the thickness and area of anchor plate are calculated (the anchor plate of value reinforcement is larger than that of high-strength bolt anchor plate, in order to make up for the reason of low success rate of value reinforcement), the welding of supporting plate or connecting plate shall be conducted by cutting.During installation, pull-out test shall be carried out for anchor bolt, and soil method test can be carried out for small shear force. When drilling holes in all anchor plates, probe reinforcement shall be considered. More drilling and less installation are allowed, but the load shall not be less than the design load.If there is a gap between the anchor plate and the concrete beam or the concrete column, grouting or grouting material can be carried out, and the main beam can be loaded after all anchor bolts are solidified.

2, main beam

The main beam in the sandwich project is the second key to safety, if a tree foundation is good and the trunk can not bear external force, the selection of the main beam is directly related to the bearing capacity of the roof. If the span is small, I-beam or H-beam can be selected. After the steel beam is selected, it should be polished, derusted, cut and primed. After arriving at the site, the two ends of the tree are anchored for fine cuttingSandwich engineering is different from other steel structure projects. The length of most beam purlins is uncertain, so cut after measurement. If the span is small, section steel should be selected as far as possible, because box girder must be welded, with high cost, heavy weight, difficult hoisting and transportation, and mezzanine floor of the first floor

3, connection

Steel structure construction is mainly the connection of steel beam, 1 welding, 2 high strength bolt connection.In large projects, high-strength bolt connection or welding is generally used, because the site and welding power supply allow this is not much to say. In the sandwich construction site, the space is often narrow and the main beam is difficult to enter. Even after being disconnected from the outside, the machine can not be used easily. After manual lifting and splicing, the steel beam is connected after hoisting. 

5、 Stacking and transportation of components:

(1) Transportation mode of components

According to the component size and construction site requirements, the project plans to adopt the highway based transportation mode to transport the components to the construction site quickly, smoothly and stably.The basic requirement of steel structure loading and reinforcement is that it must be able to withstand the action of various forces produced in normal automobile transportation, so as to ensure that the steel structure will not move, roll and fall in the whole process of transportation.

(2) Loading method of steel structure

A. during the transportation of steel structure, the supporting shipment shall be carried out according to the installation sequence;

B. the loading capacity of the vehicle shall not exceed the load capacity approved in the driving license;

C. ensure balanced and stable loading and firm binding;

D. when transporting components, select vehicles according to component specifications and weight.The load height of large freight cars shall be controlled within 4.5 meters from the ground, the width shall not exceed the compartment, the front end shall not exceed the vehicle body, and the rear end shall not exceed the vehicle body by 2 meters; the steel members on site shall be transported to the construction site in two batches, the first batch shall be transported with 20 ton freight cars of the first four and the last eight, and the second batch shall be drawn and pressed with 5-ton freight cars.

E. when the length of the steel structure does not exceed the rear guard board of the carriage, it is not allowed to lay the breast board horizontally or put down; when the steel structure exceeds the length, the number plate, turn signal, brake light and tail light are not allowed to be covered by the components and the breast board;

F if the volume of steel structure exceeds the specified value, it must be approved by relevant departments before loading;

G. the included angle between the iron wire (or steel wire rope) and its projection on the car floor is generally close to 45 degrees.

H. when the components are transported to the construction site, a 35 ton crane is required to be unloaded by one shift. Due to the site conditions of the construction site, the crane cannot be lifted to the construction room.It needs to be transported to the construction room by manpower.The length of H-beam is 12 meters, each of which needs manual flame cutting for two sections. After that, six workers will carry it to the construction site on the trolley.A total of 45 H-beams with a length of 12M, two steel plates of 1.51m * 6m and a floor support plate of 1200 M2 are required. A total of 8 workers and 7 workdays are needed to complete the transportation to each room of the construction site with the help of trolley.

(3) Stacking of components

Components are generally stacked in the factory yard and on-site yard.The lifting ground of component stacking should be flat and solid, without water pit and ice layer, the ground should be flat and dry, and the drainage should be smooth, with good drainage facilities, and there should be a circuit for vehicles to enter and leave at the same time.

The components shall be divided into areas according to type, model and installation sequence, and signs shall be erected.The bottom cushion block of the component shall have sufficient bearing surface, and large settlement of the cushion block is not allowed. The stacking height shall be calculated based on the fact that the lowest component does not produce permanent deformation, and shall not be piled up arbitrarily.Steel structure products shall not be directly placed on the ground, but shall be padded 200 mm.

In the process of stacking, if there are unqualified deformation components, they shall be strictly checked, corrected and then stacked.It is not allowed to stack unqualified deformation components in qualified components, otherwise the installation progress will be greatly affected.

For the components that have been stacked, special personnel should be assigned to collect data, establish a sound dynamic management of entering and leaving the factory, and it is strictly forbidden to turn over or move them randomly.Meanwhile, the stacked components shall be properly protected to avoid wind and rain, sun and night dew.

Different types of steel members are generally not stacked together.The steel members of the same project shall be stacked in the same area by classification to facilitate loading and shipment.