The removal of a large steel structure industrial plant construction

1 Introduction
With the rapid development of China's urban construction, demolition and construction of the building. However, the construction technology research is still relatively weak. In this paper, the demolition and construction of a large steel structure industrial plants, facilities work a useful discussion on the demolition of similar buildings.
2 Project Overview
Because of the real estate development, a Beijing steel structure industrial plant to be removed. 48.8 meters long after the Found, plant east-west direction, north-south and 22.5 meters wide, 17 meters high eaves, roof trusses 21.5 m. Along the north and south walls have a row of nine steel components corbel, the cross-sectional shape shown in Figure 1. Plant north is a brewery five-story boiler room in Beijing, both the nearest distance of 8.45 meters. South, east and west as open space. The factory plan view shown in Figure 2.

3 plant structure analysis
The plant is a steel frame structure, both north and south walls of a row of nine symmetrical steel members corbels, symmetrical corbel connected through triangular steel roof trusses, steel beams connected through the top of the column adjacent corbels. The east and west walls each have two wind resistance with a long pass reinforcement column. Plant from top to bottom the distribution of five cement ring beam plant wall 24 wall of cement mortar bonding corbels and wall ring beam spacing 42cm Rachel steel. The plant by analyzing the overall structure is very strong, mainly support the force structure for the corbel, the column steel beams and steel roof trusses of the steel frame. Wall weight is borne by the ring beam.
The 4 planned construction program
In view of the structural integrity of the plant, and the tight schedule, and close proximity to the the brewery boiler room, the collapse of the program decided to use a one-time overall southward. Corbel steel components, construction sequence was cut off from the base portion of the first to use gas cutting after cutting the shape shown in Figure 3, and then use hydraulic hammer off the south and east ring beam, wind column, to the north and south of the wall in dead weight collapse under the action, then hydraulic shears from the top to the the drag directly south of the southeast corner of the corbel, it collapsed, and lead the overall structural instability and collapse.

5 force analysis.

5.1 parts cut corbel retain pressure on steel plate column instability calculation

Corbels cut, the most unfavorable conditions for the entire surface of the walls and pillars, steel roof truss weight acting on the cutting site at:

(1) axial compression calculated

σ = N / An ≤ f

σ stress of the steel plate column N of steel column pressures, An steel column cross-sectional area, f is the steel plate column can withstand the maximum compressive stress.

f = 190N / m ㎡

An = 550 × 16 = 8800mm

N ≤ f × ​​An = 190 × 8800 = 1672000N = 1672KN

Nmax = 1672 × 9 = 15048KN

F is the load weight

F wall = 48.8m × 17m × 0.24m × 19KN/m3 ≈ 3783KN

The F steel column = (2 × 1.3 +3 × 0.55) × 17 × 0.016 × 7850kg/m3 = 9074.6Kg ≈ 0.926KN

Because there are steel roof trusses and load for insurance purposes, the total weight taken a factor of 1.1.

F = (F the wall + F steel columns) × 1.1 = (3783 +0.926 × 9) × 1.1 ≈ 4171KN

Visible F <Nmax

(2) instability calculation

N / (φA) ≤ f

The φ component pressure stability factor determined by the slenderness ratio λ.

f = 190N / m ㎡

A = 550 × 16 = 8800mm

λ = 1400/16 = 87.5

φ = 0.548

N ≤ f × ​​Aφ = 190 × 8800 × 0.548 = 916256N ≈ 916KN

Nmax = 916 × 9 = 8244KN

Visible Nmax> F = 4171KN

5.2 overall collapse, the framework for stress analysis

Corbel by force when collapsed, mainly gravity and tension, steel roof truss clockwise torque. Horizontal direction by the force in Figure 4, it should be noted that due to the retention of the Western Wall, the northwest corner and southwest corner of the two corbel steel roof truss erection of the wall in the West, to the Western Wall axis formation leverage great torque. Two corbel column the lodging direction will be different with a few pillars.
Stress analysis above, the expected the corbel collapse direction shown in Figure 5.

6 construction effects

Calculated by analyzing the actual situation at the scene and found the steel column strength once collapsed, turn south of a row of steel columns at the bottom to keep steel plate, part cut off, leaving only the middle 1/3 of the width. After the fall of the actual situation and the situation is expected to match, were no influence in the north of the brewery boiler room.

7 Conclusions and recommendations

The difficulty lies in the demolition work corbel the collapse direction, we must ensure the absolute safety of the brewery boiler room. Do this by pre-analysis to determine the direction of the corbel collapsed, and then construction ensure dismantling success.