Project - Hospital

Before seismic retrofitting

Hospital

The “工”-shaped building of a certain hospital was built in 1958. It is a brick-concrete structure with six floors above ground (partially five floors) and one floor underground. The total building area is 23,337 square meters, and the building plan is basically "I" shape (the first floor plan of the building is shown in Figure 1). The northern part of the "工" shape is the outpatient building, the southern part is the ward building, the eastern part is the medical technology building, and the west is the emergency building. The house has the typical characteristics of hospital architecture in the 1950s. Its "I"-shaped hospital layout, red brick and white gray exterior walls, and heavy terrazzo floor have a profound imprint of the times. This is also the part where the owner proposed to retain the original historical mark of the original style in this reinforcement and renovation.

The house has exceeded the 50-year limit for the design service life. The house first needs to undergo structural safety and seismic appraisal and make corresponding treatments based on the appraisal results before it can continue to be used. In addition, the original facilities of the ward building can no longer meet the functional requirements of the hospital, so it was decided to strengthen and renovate.

The seismic fortification category of the house is the key fortification category, and the seismic appraisal shall be carried out according to the method of category A with a subsequent design service life of 30 years. After structural appraisal, the safety level is rated as Csu. The house is locally dangerous, and measures should be taken immediately. The seismic resistance does not meet the requirements of relevant standards and requires overall reinforcement.

Reinforced technical solution

The house is divided into nine parts by eight deformation joints, and the structure identification and reinforcement are also divided into nine independent houses. Among them, the static safety and seismic safety of the "I"-shaped main structure do not meet the requirements. Due to the shortage of funds during the reinforcement and reconstruction of the house, the owner proposed to use the follow-up service life of 10-15 years for structural identification and reinforcement. Corresponding and targeted reinforcement is carried out for components whose static force does not meet the requirements of bearing capacity. For seismic resistance, the original appraisal report carried out the calculation of the seismic bearing capacity of the components in accordance with the current seismic code, and it was concluded that a considerable number of walls did not meet the seismic requirements and needed to be reinforced one by one. The design institute re-conducted the classification appraisal in accordance with the relevant regulations of the appraisal standard A-type masonry building, and used the method of the comprehensive seismic capacity index of the floor to evaluate the comprehensive seismic capacity of the building. The evaluation results show that except for the fifth floor, the comprehensive seismic capacity index of the other floors is less than 1, which does not meet the seismic requirements and needs to be reinforced.

The reinforcement of the building is based on the conclusions of safety appraisal and seismic appraisal, and comprehensive consideration is given to determine the reinforcement plan. In addition, it is necessary to follow the design principles of seismic reinforcement, that is, the principle of improving the comprehensive seismic capacity (bearing capacity, integrity), and to find out the key to the structure to achieve the fortification goal in view of the defects of the original structure. Try to eliminate unfavorable factors such as irregular, unreasonable, and weak layers of the original structure. Secondly, seismic reinforcement is different from engineering accident handling, emphasizing overall reinforcement and avoiding component reinforcement. At the same time, the corresponding reinforcement plan is selected in combination with the requirements of use function, construction method, environmental impact and economic aspects. And to ensure the effectiveness of the reinforcement measures, minimize damage to the original structural members, the reinforcement members and the original structure are reliably connected, and new weak layers should be avoided after reinforcement to ensure the coordination of the new and old members. Finally, make full use of the existing bearing capacity of the foundation to minimize the amount of foundation reinforcement.

For those with insufficient safety, component reinforcement is the main focus; for seismic reinforcement, the overall and seismic concept reinforcement is the main focus, and component reinforcement is supplemented for comprehensive overall reinforcement. And under the premise of meeting the bearing capacity, try to maintain the historical features of the original building, reduce the impact on the original building's functions, and reduce the cost, that is, safe, applicable and economical. The comprehensive seismic capacity index of the reinforced floor should be greater than 1, and new floors with sudden changes in the comprehensive seismic capacity index should be prevented. That is, the shear capacity of this layer after reinforcement shall not be greater than 20% of the adjacent next layer. When it exceeds, the seismic capacity of the next layer shall be enhanced at the same time until the requirements are met.

After seismic reinforcement

The reinforcement plan was finally determined:

1. Partially strengthen the components with insufficient static force, and strengthen the system with insufficient earthquake resistance. Due to the large number of longitudinal openings, the main reason is that the longitudinal seismic bearing capacity is insufficient. The reinforcement method adopts the method of strengthening all the longitudinal walls of the corridor in the bottom several floors. This not only avoids the influence of a large number of excavated foundations on external traffic when reinforcing the external walls from the outside of the building, but also reduces the damage to the original terrazzo ground of each house when the external walls are reinforced from the inside of the house.

2. The horizontal wall is selected for reinforcement according to the principle of evenly distributed spacing. Finally, the comprehensive seismic capacity index of the vertical and horizontal directions of the floors is greater than 1, and the shear capacity of the adjacent upper floor does not exceed 20% of the next floor to avoid weak layer or weak layer transfer. In this way, the force is reasonable and the layout is coordinated, which has the least impact on the layout and usable area of the house, and the cost is not high.

The specific reinforcement methods are:

1. The longitudinal seismic capacity is insufficient. According to the degree of insufficient seismic load-bearing capacity, part of the wall shall be reinforced with 70mm thick reinforced concrete slab wall or 50mm thick reinforced mesh cement mortar surface reinforcement. These parts are mainly the walls on both sides of the walkway and a few horizontal walls, and the reinforcement range decreases with the increase of floors.

2. In addition to partially adding reinforced concrete frames to strengthen and strengthen the large holes in the nurse's station, etc., the comprehensive seismic capacity of the floor should be re-evaluated and re-consolidated.

3. Reinforced concrete lintels are added at the height of the original opening. When the original doorway is blocked, the structure is blocked. The new opening needs to consider the static force and the overall seismic capacity of the floor, and the wall should be reinforced on the basis of the addition of reinforced concrete lintels.

4. The floor slab and reinforced concrete girders of the archives room are replaced with enlarged section reinforcement. The brick wall on the first floor of this site is reinforced with 70mm thick reinforced concrete slab wall, and the slab wall is set with the same depth as the original wall. Figure 3 is a schematic diagram of a part of the structural reinforcement.

5. In order to maintain the original terrazzo floor, manual operations are used when the wall is reinforced and chiseled, and corresponding protective measures are taken. The final reinforcement only affects the terrazzo with a width of about 20 cm near the reinforced wall, and the rest are large. The area of the terrazzo floor has been well protected.

The “important” point of the seismic reinforcement and reconstruction of this project is to take into account the structural safety and the layout and flow of the hospital building, as well as the layout and location reservation of the mechanical and electrical equipment. Due to the strict requirements of medical procedures, there are corresponding regulations on the layout, area, and hole size of medical houses. The architect has repeatedly communicated and coordinated with the architect and the user in a targeted manner, so that the house can truly meet the requirements of the relevant national standards for structural safety and the medical process and use requirements of the hospital. With the adjustment of the architectural plan layout, the structural reinforcement has also been adjusted and modified many times. In addition, due to the difference between the site layout and the location and size of the opening and the as-built drawing, the structural designer cooperated with the architect to carry out the detailed field measurement of the components one by one on the site, which was reflected in the construction drawing. The electromechanical equipment of the hospital itself is more complicated than other public buildings because of its complicated medical functions. In addition, the original building equipment drawings are seriously missing, and the equipment pipelines have been remodeled without drawings for several times, so the transformation is quite difficult. In order to reserve the equipment openings in advance to avoid back chiseling to maintain the integrity and effectiveness of the structural reinforcement, the structural engineer cooperated with the equipment engineer to drill the suspended ceiling and dive into the trench on the construction site many times, and find relevant personnel to understand the situation. After fully grasping the mechanical and electrical equipment on the house site, the structural engineer carried out the corresponding treatment of the equipment opening to ensure the integrity and firmness of the structural reinforcement and indirectly reduce the cost.

The "difficult" point of reinforcement and reconstruction is how to achieve construction and use without affecting the use of a large area. All live loads on the upper part should be removed as much as possible before the structure is reinforced. Because most of the hospital buildings are tight and difficult to turn over, this transformation proposes to use deformation joints to divide the reinforcement construction into several sections. The plan of segmented implementation and rotation is adopted so that the reinforcement construction only affects some areas, and other areas are still in operation. However, it is necessary to carry out enclosure and sound insulation measures during construction. The unit arranges construction time reasonably to reduce noise as much as possible, and arrange for noise at the far end and during the day. In addition, the hospital also needs to formulate corresponding management measures, scientifically arrange patients, and do a good job in the ideological work of patients and their families. This is really difficult.

Sum up

Under the premise of tight medical premises and difficulty in turnover, the project can successfully reinforce the reconstruction and overcome difficulties. The main experience is as follows.

First, it is very important to have a complete and reasonable project organization for project coordination and reasonable plan management, and to ensure that the construction unit, design unit, construction unit, supervision unit and other participating parties work together and cooperate with each other;

The second is that the government undertakes the funds for seismic reinforcement and comprehensive renovation, which solves the problem of project funding. In addition, in-depth investigations in the early stage of project application, reasonably determine the project content and reasonable funding requirements, and ensure that there are no omissions and repetitions in the funding application. This is the project can implement Financial guarantee;

The third is to strictly control the quality of the project, select the participating units of project construction, adhere to the high standards of project construction, and increase the frequency of inspections;

The fourth is the strong management of the construction unit. Because the original building completion drawing does not match many places on the site, during the project implementation process, when it encounters the removal of non-structural components such as the suspended ceiling partition wall, it is found that there is a discrepancy with the surveying drawings. The construction unit immediately organizes All participating construction parties conduct timely consultations to ensure that the implementation plan is adjusted in the shortest time and the project is completed on schedule;

In addition, due to the shortage of hospital rooms, they need to be used during construction. The construction unit plays a pivotal role in the coordination of sound insulation of the wards and comfort of patients. ,

For reinforcement and renovation projects, the government coordinated the development and reform, land, planning, and fire protection departments to simplify the approval procedures and shorten the processing time for comprehensive renovation projects under the premise of complying with the construction laws and regulations. These measures are a strong guarantee for the implementation of the project.