According to the website of the Beijing Municipal Commission of Housing and Urban-Rural Construction, in order to implement the work plan of the Municipal Committee and Municipal Government on the special renovation of the safety of self-built houses in Beijing, we should do a good job in checking the results of the investigation of potential safety hazards of non-operating self-built houses. The Office of the Leading Group for the Special Renovation of the Safety of Self-built Houses in Beijing has organized and compiled the Guidelines for the Verification and Assessment of the Investigation Results of the Structural Safety Hidden Dangers of Non-operating Self-built Houses in Beijing (hereinafter referred to as the Guidelines for Assessment).
The Assessment Guidelines show that in order to make the results of the investigation of potential safety hazards of rural non-operating self-built houses in Beijing administrative region conform to the reality, do a good job in the verification of potential safety hazards, and ensure the quality of district-level verification and city-level spot checks, the Guidelines for Verification and Assessment are formulated. The verification of urban non-operating self-built houses within the administrative region of Beijing shall be carried out in accordance with the provisions of the Technical Guidelines for the Investigation of Structural Safety Hidden Dangers of Self-built Houses in Beijing (JJF [2022] No.325).
The Guidelines for Assessment make it clear that the verification of potential safety hazards of self-built houses should be divided into two parts: the building site, the foundation and the superstructure. The potential safety hazard of the building site and foundation shall focus on checking whether the building is located in the geological hazard area or whether the foundation has uneven settlement and instability; the potential safety hazard of the upper structure shall focus on checking the continuity of the vertical load-bearing components of the structure, the reliability of the connection structure of the components, the overall inclination of the building, the deformation and damage of the main structural components, etc; The most serious category in the safety verification results of the site, foundation and superstructure shall be taken as the category of the housing safety verification results. In terms of the assessment of the verification results of potential safety hazards in the
foundation, the Guidelines for Assessment point out that if the foundation of a self-built house meets one of the following conditions, it should be assessed as a house with major potential safety hazards:
(1) The foundation is unstable and slips, and the horizontal displacement has exceeded 10 mm. Significant impact on superstructure and signs of continued sliding.
(2) The frame beams and columns of concrete structure houses are cracked due to the deformation of the foundation, and the overall inclination of the houses is more than 1%.
(3) The overall inclination rate of single-storey and two-storey houses caused by foundation deformation exceeds 3%, and that of three-storey and above houses exceeds 2%.
(4) The foundation has excessive uneven settlement, which causes the crack width of the upper wall to be greater than 10 mm and the overall inclination rate of the house to be greater than 1%.
(5) The foundation has produced through cracks and the maximum crack width is greater than 10 mm. Due to the deformation of the foundation, there are many cracks in the upper load-bearing wall of the masonry structure and the maximum crack width is greater than 10 mm.
In terms of the assessment of the verification results of potential safety hazards of the superstructure, the Guidelines for Assessment point out that self-built houses with masonry structures that meet one of the following conditions should be assessed as houses with major potential safety hazards:
(1) Vertical cracks with a width of more than 2 mm and a joint length of more than 1/2 of the floor height due to compression of load-bearing walls. Or a plurality of vertical cracks with the length of the crack exceeding 1/3 of the storey height, and vertical cracks with the width of more than 2mm are generated in the compression column.
(2) The effective section of the surface of the load-bearing wall or column is weakened by more than 25% due to weathering, peeling and mortar pulverization.
(3) The wall or column section at the end of the supporting beam or roof truss has multiple vertical cracks due to local compression, or the width of the cracks has exceeded 1 mm.
(IV) The wall or column has horizontal cracks due to eccentric compression, and the maximum crack width is greater than 0.5mm.
(5) When the local inclination deformation of a single wall or column relative to the whole building is greater than 7 ‰, or the joint of adjacent components is broken into a straight joint, and the width of the crack is more than 2 mm.
(6) There is an independent brick column with a section size not greater than 240 mm × 240 mm, and the brick column has vertical or oblique cracks or serious deformation.
(VII) Deflection and flashing of walls and columns, and horizontal or cross cracks in the deflection part.
(8) The width of the vertical crack in the middle of the brick lintel is more than 2 mm, or the inclined crack is produced at the end, the maximum crack width is more than 1 mm and the crack is long to 2/3 of the wall between windows, or the horizontal crack is produced in the wall supporting the lintel, or the obvious bending and sinking deformation are produced.
The Guidelines for Assessment specify that self-built houses with wooden structures (including wooden roofs) that meet one of the following conditions shall be assessed as houses with major potential safety hazards:
(1) The deflection and deflection of wooden roof trusses are obvious, the deflection of roof trusses is greater than 10/120, or the out-of-plane inclination exceeds 1/120 of the height of roof trusses; Or the top and end nodes are decayed or split; or the wood (beam) components have transverse cracks, and the roof collapses.
(2) Tenon pulling or loosening of wooden frame connecting nodes, serious corrosion or partial deformity of connecting iron parts.
(3) Wood components have many scabs and carbonization, with obvious deformation, distortion, decay and ant erosion.
(4) When the depth of the shrinkage crack of the compressed or bent timber component exceeds 1/2 of the diameter of the component and the length of the crack exceeds 2/3 of the length of the component.
(5) The rise of lateral bending deformation of wooden column is more than H/150, or the damaged area of column top splitting, column body fracture and column foot decay is more than 20% of the original section.
(6) When the local inclination deformation of the enclosure wall relative to the whole house is more than 7 ‰ and the width of the obvious separation from the wooden column is more than 2 mm.
"Assessment Guidelines" also shows that self-built houses with reinforced concrete structures that meet one of the following conditions should be assessed as houses with major potential safety hazards:
(1) The deflection of beams and slabs exceeds 10/150, and the crack width of the lower tensile area is greater than 1.0mm.
(II) The width of longitudinal corrosion expansion crack of beam and slab is greater than 1.0mm due to the corrosion of main reinforcement, or the concrete of component is seriously damaged, or the concrete protective layer is seriously peeled off and exposed, and the effective section after the corrosion of reinforcement is less than 4/5.
(III) The compression column has vertical stress cracks, the concrete cover is peeled off, and the reinforcement is exposed and rusted; or one side of the column has horizontal cracks with a width of more than 1mm, the concrete on the other side is crushed, and the main reinforcement is exposed and rusted.
(4) The column or wall has obvious inclination, the inclination rate exceeds 1%, or its lateral displacement is greater than H/300.
(V) The column and wall concrete is cracked and bulged, and the failure surface is greater than 1/3 of the total section, and the main reinforcement is exposed and seriously rusted.
(6) Vertical cracks occur in the tensile area of the mid-span or intermediate support of simply supported beams and continuous beams, and the cracks extend to more than 2/3 of the beam height and the width of the cracks is more than 1mm, or shear inclined cracks occur near the support, and the width of the cracks is more than 0.4mm.
(VII) Cantilever components such as balcony slab and canopy are subject to sagging deformation, and the crack width at the root of the cantilever component is greater than 0.5mm.
(VIII) The concrete cornice is cracked and the reinforcement is seriously rusted, and there is a risk of falling off at any time.
(IX) Deflection of the roof truss is greater than l0//200, and the lower chord has transverse cracks with a width greater than 1.0mm; the support system of the concrete roof truss fails, resulting in obvious inclination, and the inclination rate is greater than 2%. According to the requirements of the
Assessment Guidelines, non-operating self-built houses with major hidden dangers in the investigation and verification results shall be inspected, identified and disposed of in accordance with the relevant provisions of the Technical Guidelines for the Investigation of Structural Safety Hidden Dangers of Self-built Houses in Beijing (JJF [2022] No.325).
浙公网安备33010802003254号