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Discussion on constructional column of building structure in 1

Abstract: The main function of constructional column in building construction is to improve the integrity and seismic capacity of buildings. This paper introduces the function and function of constructional column, structural requirements, common problems in construction and technical measures to ensure quality.

Keywords: integrity; Structural column; quality

Reinforced concrete constructional column is a measure to improve the seismic capacity of buildings. However, due to various reasons, many construction units failed to pay attention to the construction quality during the construction of reinforced concrete structural columns. This has a negative impact on the overall quality of the building and brings hidden dangers to the building, so we must pay attention to the construction quality of the constructional column.

1 efficacy and function of constructional column

Setting reinforced concrete columns is a measure to improve the bearing capacity of multi-storey brick-concrete structures. Structural columns are generally arranged at the corner of the outer wall and the junction of the inner and outer walls on the horizontal plane, and are reliably connected with the ring beams; Vertically, it is required to align and connect along the height of the whole building, and a space system similar to a "small frame" is formed by ring beams. It plays a very significant role in improving the shear strength of multi-story brick masonry, resisting the displacement of horizontal thrust and reducing earthquake deformation. According to the experimental research data of constructional columns, setting reinforced concrete constructional columns in multi-storey brick-concrete buildings can improve the external strength by 20% at most and the ductility of walls by more than 3 times. When the lateral displacement of the wall is about 12 cm, it can still bear the vertical pressure of 035MPa without collapse. The joint action of constructional column and ring beam can restrain the deformation of masonry and bear large plastic deformation.

2 structural requirements of constructional column

2. The constructional column of1multi-storey brick house shall meet the following requirements: the minimum cross section can be 240× 180mm, the longitudinal reinforcement should be 44 12, the stirrup spacing should not be greater than 250mm, and the upper and lower ends of the column should be properly encrypted. Seven degrees above six floors, eight degrees above five floors, longitudinal reinforcement 44 14, nine degrees stirrup @ 200 ram. The structural columns at the four corners of the building can be strengthened by appropriately increasing the cross section.

2.2 The joint between the constructional column and the wall should be made into a horse-tooth shape, and two Rachel bars should be set every 500mm along the wall, and each side should extend into the wall. 2.3 constructional columns should be connected with ring beams on each floor, and reinforced brick belts should be added to floors without ring beams in the interlayer. Only when structural columns are set at the four corners of the external wall, the reinforced brick belt should extend through an opening in the external wall; otherwise, the reinforced brick belt should be connected with the external longitudinal wall and the corresponding transverse wall. The section height of reinforced brick belt is not less than four skin bricks, and the mortar strength is not less than M5.

2.4 The constructional column is set according to the structure, and there is no need to set the foundation separately. When there is a ring beam at the top of the foundation, the constructional column can be anchored in the ring beam.

3 constructional column quality common problems and their causes

3. 1 The setting of stirrups and tie rods cannot meet the specifications.

The wall and constructional column should be connected with two horizontal tie bars along the 50th cm of the wall height, and each side should not be less than1m; At the node where the constructional column intersects the ring beam, the stirrup of the column should be properly encrypted. The encryption range should not be less than one sixth of the height or 45cm above and below the ring beam, and the stirrup spacing should not be greater than 10cm. Vertical reinforcement of constructional column can be bound by joint, and the joint length is 1d, generally 35d. The stirrup spacing of the binding part should not be greater than 10cm. The above points can be guaranteed except that the wall reinforcement is not completely 50cm***. Almost all others are stirrup encryption, etc., which are most realized because of the low level of construction management and poor technical quality.

3.2 Axis dislocation of constructional column between floors

When pouring concrete, the steel skeleton was not carefully adjusted. When the laying-out of the lower masonry was not completed, it was found that the lower constructional column was crooked, so the correct position was given on this floor, which led to the phenomenon that the upper and lower floors were not connected and the axis was offset.

3.3 constructional column "disorderly root" reasons

Because the construction process of constructional column is that after laying a layer, concrete is poured into the reserved "column cavity". Because the "column cavity" runs through the whole building time, its roots are generally sandwiched with mortar, brick slag and other sundries, and because the concrete is poured to the level of the ring beam, after the floor is hoisted and the wall is built, a "column pit" with a height of 12mm lower than the floor appears at the root of the structural column, and the sundries in the "column pit" are difficult to clean up, and "rotten roots" are formed here after the concrete is poured.

3.4 Fracture of constructional column

Because the stirrups, wall lacing bars and ring beam bars in the constructional column are intertwined, the discharging and binding of steel bars are irregular. In the process of pouring ring beam and constructional column at the same time, it will definitely hinder the fall of concrete; During construction, sometimes brick slag accidentally falls into and gets stuck in the "column cavity", which hinders the filling of concrete; When constructing ring beams and structural columns, the river stones used are often poorly graded sand leakage. If there are big stones, the constructional column will also be "broken".

Four specific questions

4. 1 The concrete connection is not good, so it cannot be wiped off. Before concrete is cast, the sawdust, broken bricks, floor ash and other sundries in the formwork are not cleaned, and the concrete cast twice before and after is not closely connected, so the integrity of the constructional column cannot be guaranteed.

4.2 Exposed tendons and pits. Before shuttering, there is no binding concrete protective layer pad on the reinforcement skeleton, which leads to insufficient thickness of the protective layer of reinforcement and inaccurate positioning of some reinforcement, which leads to the exposure of reinforcement; Before concrete pouring, the formwork and Mayacuo brick wall were not fully wetted, and part of the water in the concrete was absorbed by the brick wall and formwork, resulting in pits and crispness on the concrete surface.

4.3 "Running slurry". On the one hand, the surface of the brick wall on both sides of the horse tooth rub is uneven, and the gap between the template and the brick wall is large. On the other hand, the template is not tightly stitched, resulting in "slurry leakage".

4.4 Voids and "defects". Some cast concrete does not use plug-in vibrator, but blindly uses shaking steel skeleton and formwork instead of vibrating, resulting in serious quality problems: first, the concrete is generally not dense, the concrete between the horse's teeth is not in place, the brick wall and the constructional column are not closely combined, and many holes and "faults" appear after formwork removal; Second, the steel skeleton generally appears "falling apart" and displacement.

5 technical measures to ensure the construction quality of constructional column

First of all, it is necessary to improve the construction unit's understanding of the necessity of adding concrete structural columns. According to the different construction conditions and design requirements of the project, technical measures to ensure the construction quality of constructional columns are formulated and strictly implemented. Specific measures are as follows:

5. 1 For reinforced concrete structural columns buried in the wall, vertical and horizontal walls are generally built first, and a "column cavity" is formed after the wall is built, that is, the position of the structural column is reserved. With the layered masonry and pouring of the wall and ring beam, the constructional column will be constructed in columns. In order to ensure that the center line of the constructional column is on the same straight line, the position of the reserved column cavity must be accurate. Therefore, when laying, always check the verticality of the reinforcement skeleton of the constructional column. After the reinforcement skeleton is hung straight and corrected, immediately fix its position with Rachel reinforcement of the wall. Then, before pouring concrete, lead the center line of the constructional column to the upper mouth of the ring beam formwork or the "column cavity" to align the center of the steel skeleton with the center line of the column. Only in this way can the correct position of the constructional column be guaranteed.

5.2 For the constructional column designed for horse teeth rubbing, starting from the footing of each floor, the principle of laying back first must be strictly followed to ensure that the footing of the column is a large section. The tooth height of each horse tooth rub is generally about 30cm * * * The height of the five-layer brick is * * *, and the tooth depth is not less than 6cm. When the tooth depth is 12cm, one layer of the upper mouth is 6cm and the other layer is 12cm, so that the concrete at the corner of the upper mouth of the horse tooth rub can be poured tightly.

5.3 The steel skeleton shall be segmented and bound with the construction surface of the column section, and the binding point shall be firm and reliable to prevent dislocation and slip. The vertical lap length is generally 35d. The stirrup of constructional column shall not be less than 1/6 height or 45cm height of ring beam, and the stirrup spacing shall not be greater than 10cm. For the requirement of setting two 06 Rachel bars every 500mm along the wall, the bricklayer must be strictly required to put them in the mortar joint.

5.4 Strictly implement the mixing process requirements. The diameter of coarse aggregate should be 2cm, and the slump should be controlled at 5-7 cm. When pouring in sections, the corresponding test blocks shall be retained as required.

5.5 The constructional column concrete is usually poured in sections. Generally, each floor is a construction section, and the construction height of column section should not be greater than 2m. The cleaning mouth is reserved at the bottom of each column, so as to clean up the mortar, sawdust, brick slag and other sundries in the column template before pouring. Before pouring and vibrating the new concrete column, the loose stones on the old concrete surface at the joints should be removed and washed with water. Then, salt cement mortar is prepared by using the lime sand content in the concrete mixture ratio of constructional column, and spread on the surface of old concrete with a thickness of 1 ~ 2 cm to ensure the reliable quality of the combination of new and old concrete.

5.6 The special person shall be responsible for the vibrating operation of the structure. During pouring, assign special personnel to observe the section of pouring column to avoid slurry leakage, excessive vibration and improper concrete pouring due to blockage in the middle. When pouring concrete into a concrete column, it is advisable to use an internal vibrating rod for layered vibration. The vibrating rod should be dialed with the vibration, and the thickness of layered vibrating should not exceed 300mm_. When vibrating, it is forbidden to vibrate brick walls and steel bars, so as to avoid wall loosening, Rachel falling off or steel skeleton shifting. Before pouring, brick masonry and wooden formwork must be watered and wet, and the cleaning mouth should be closed. The intersection of constructional column and ring beam must be cast at the same time.

In a word, the correct use of constructional columns is an important measure to improve the seismic efficiency of masonry structures. Together with the ring beam, it inhibits the cracking of brick masonry, so that the cracks will not further expand the suite, and even if they crack, they will not collapse, and the structure composed of very brittle materials will gain considerable deformation resistance.

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