工程建设标准强制性条文CPECS-B-7房屋建筑部分.doc

Chapter VIIStructure appraisal and reinforcement1. Appraisal of structure safety1.1General rules GB 50292-19994.1.3 The data adopted for appraisal of safety of structure elements shall meet the following requirements:1 Methods of inspection shall be based on the current national standards. When more than one inspecting method is to be used, a regulation for determining test value shall be agreed before the test is carried out.3 When the detected data are doubtful for any abnormality, the judgement and treatment shall be in accordance with the current rules of the national standard; neither adoption nor abandon of data at random is allowed.4.1.6 When performance of material of a structural element is degraded due to environmental effect and other systematic factors relating to time, it is allowed to pick up samples at random, from which 5 10 sample structural elements will be determined as inspecting targets, of which the material strength and other dynamic performances will be detected in accordance with present standard methods.Note： When total elements are fewer than 5, all of them shall be tested one by one. GB 50165-924.1.4 Appraisal of reliability of ancient constructions shall be divided into 4 categories according to the following rules:Category I. The existing damaged or weakened points in the structure that is load-bearing have been already treated correctly and no new damaged or weakened or sign of damaging or weakening are found.Category II. Those once damaged or weakened points in load-bearing structure have been already repaired and reinforced, yet there are individual points that have to be treated again; some newly found signs of damage or destroying that need to be further inspected and treated but do not affect safety and use of the construction.Category III. When the damaged or weakened points are at the critical position of the load-bearing structure, which, or its combination, affect safety and normal use of the structure and is necessary to be reinforced or repaired, yet no immediate danger will happen.Category IV. The structure is in a danger status either partially or wholly and unexpected accident is possible to happen at any time. Such structure must be repaired immediately.1.2 Concrete Structural elements GB 50292-19994.2.1 Appraisal for safety of concrete structural elements shall be inspected in four items: capability of load-bearing; structure; bit shift (or deformation), for which the element is not suitable for use; and cracking. Each inspected element shall be classified by evaluation individually, of which the one has lowest result shall be referred as class of safety.4.2.2 When safety of concrete structural element is evaluated per its load-bearing capability, class of each item that is calculated shall be evaluated individually, then the lowest one shall be the base on which safe load-bearing capability is determined.4.2.3 When safety of concrete structural element is evaluated based on its structure, it should be determined with two items that are being inspected, and the lowest shall be as class of them.4.2.4 When safety of concrete structure is evaluated based on bit shift or deformation that is not suitable to bear load continuously, the following rule shall be observed:1 When the actually measured value of deflection of the truss (roof truss, supporting truss) is higher than 1/400 of the span for calculation, the capability of load bearing should be calculated according to 4.2.2 of this standard. When checking computation is being done, the effect of additional stress due to bit shift shall be considered and evaluation of class shall be based on the following principles:1) If the result of checking computation is not lower than class bu , it can yet classified as class bu, but a limitation of a period for monitoring use shall be added.2) If the result of checking computation is lower than class bu, the element shall be classified as class cu or du according to the actual severity.2. For deflection or deviation due to construction work of other element in bending, they should be evaluated in accordance with rules.4.2.7 when one of the following circumstances of a concrete element appears, it shall be classified as class du, despite the size of its cracking:1. Sign shows there is damage due to pressure;2. The element corner edge damaged or lost due to rusting of the main reinforcing bar and concrete covering layer peered off. 1.3Steel structure elements GB 50292-19994.3.2 When safety of a steel structure element (including connection) is evaluated based on load bearing capability, each result of checking computation shall be evaluated individually, then the lowest class shall be adopted as safety class of that element.1.4 Building block structure elements GB 50292-19994.4.2 When safety of a building block structure element is evaluated based on load bearing capability, each result of checking computation shall be evaluated individually, then the lowestclass shall be adopted as safety class of that element.4.4.3 When safety of a building block is evaluated based on structure, class of two items shall be evaluated respectively, and then the lower one shall be adopted as the safety class of that element.4.4.5 When the load bearing element of a building block has the following forced cracking, it shall be considered as a cracking that is no longer suitable for load bearing continuously and shall be evaluated as class cu or du according to its severity:1Ends or center parts of Brick wall, brick column under truss, main beam supports have vertical cracking that is broken along the block (trough the block).2Horizontal or inclined cracking appears at the cross section on load bearing wall of vast houses.3Cracking appears at span center or support of a brick built lintel; or, though no visual cracking is seen, a concentrated load focus is discovered within the span extent.Note: Block material is referred to bricks or building blocks.4Cracking, along the arch top main lead or diagonal line, appears at arch surface and shell surface of cylindrical arch, hyperbola cylindrical arch and flat shell.5Inclined cracking, broken along the building block, appears in load bearing wall or adjacent to arch, shell support.6Other significant cracking that is under pressure, in bending, being sheared.4.4.6 When non-forced cracking appears in building block structure or element, such cracking will Be considered as unsuitable for continue to be load bearing ones and should be evaluated as class cu or du according to actual circumstances individually:1A through vertical cracking appears at the connection between vertical and horizontal walls.2Serious cracking in wall, of which the width of the biggest cracking is wider than 5 mm.3Cracking in column appears, of which the widest is more than 1.5 mm.4Other cracking that significantly affects entirety.Note: Non-forced cracking is referred to cracking that is resulted from temperature, contract, deformation or uneven sink of foundation.1.5Wooden structure elements GB 50292-19994.5.2 When safety of a wooden structure element is evaluated based on load bearing capability; each checking computation item shall be classified for safety, of which the item with lowest safety shall be considered as safety class.4.5.3 When safety of wooden structure element is evaluated based on structure, two items shall be evaluated for classification of safety respectively, of which the lower safety class shall govern.4.5.5 When a wooden structure has the following inclined veining or cracking with a slope of （r）， it should be classified as class cu or du according to the severity:for tensile element r 10%for bending element r 15%for compression element r 20%1.6Wooden structure of ancient constructions GB 50165-924.1.7 Inspection and evaluation of entirety of wooden structure of ancient constructions shall be carried out in accordance with table 4.1.7Inspection and appraisal for entirety of wooden structure truss Table 4.1.7Item No.Inspection itemInspection contentLimit of appraisal for damaged pointsElevated beam formThrough-the-hopper form1Entirely inclined(1) Inclining amount along structure mechanism plane D1D1H0/120 orD1120mmD1H0/100 orD1150mm(2) Inclining amount along vertical structure mechanism plane D2D2H0/240 orD260mmD2H0/200 orD275mm2Local incliningRelative bit shift between column head and column foot DDH/90DH/753Linkage between structure mechanismsPresent circumstance of vertical bracing bar and its linking rodDamaged or connection loosened4Linkage between beam and column(including that between plinth and timber and column and purlin)Circumstances of pulling connection and joggling connectionNo pulling connection, the rabbet drawn out off the mortise with a length longer than the rabbet2/51/25Perfection of rabbet and mortiseMaterialRotted, moth-eatenOther damagesAlready crackedHorizontal veining pressed with deformationCompress amount beyond 4 mmNote: In the table, H0 represents total height of wood structure mechanism; H represents height of column4.1.18 When one of the following circumstances happens to ancient constructions, the appraisal of reliability shall be judged as category III or IV according to the actual circumstance:1)Sign showing damage of main load bearing structure element such as the principal beam, Eaves supporting column golden column, etc., which will result in damage of other elements as a chained reaction.2)Force transmitting points for joint of framework of the principal beam and load bearing are under dangerous circumstance.3) Serious damaged points appear at many points scattering regularly or gathering.4) In area where insect harm is serious, when new shotholes appear in many locations of the wooden structure framework, or no shotholes but worms are acting in groups.4.1.19 In appraisal of reliability of load bearing system, if the following circumstances appear, the system should be appraised as category IV construction:1)Many pieces of wood structure frameworks have serious damaged points, from which the combination may result in collapse or partial collapse of the construction.2)The construction has already inclined towards a certain direction, and observation and record show that the tendency of inclining is in developing.1.7 Earth foundation GB 50292-19996.2.10 When deep pits for foundation are dug in areas where deep and thick silt, silty soil, saturated clay soil, saturated fine silt or in other soft and weak earth layers, the adjacent existing constructions and buildings should be protected with certain measures, while measuring points shall be arranged for the supporting-protecting framework and the existing buildings for monitoring. If one of the following circumstances that may affect security of the construction appears, an alarm shall be given immediately. If the situation is serious, construction work shall be stopped immediately and emergent measures shall be taken to protect the supporting-protecting framework and existing buildings.1) The maximum horizontal bit-shift of supporting-protecting framework of the foundation pit is already larger than 1/200 (1/300) of dug depth of the pit, or more than 3mm/day (2 mm) for three continuous days.2) Individual element of the supporting rod ( or anchoring rod) system of the supporting- protecting framework of the foundation pit is bearing a stress that is increasing suddenly, or there is sign showing that the element is yielded, cracked, loosen or drawn off.3) Uneven sink of the construction (differential sink) is already more than the permitted sink difference that is specified in the existing specification for earth foundation designing; or inclination has been more than 0.0001 H/d for three continuous days(H = height of the construction.4) A crack seam with width of 3mm(1.5mm) appears in the building block of existing construction, or crack seam with width more than 15mm (10mm) appears in adjacent earth surface.5) Sign that may lead to a shearing damage appears at the bottom of the foundation pit, or other sign that may affect security appears.6) circumstance that, according to the local experience, must be monitored extensively appears.Note： If the adjacent constructions where people are always gathering, or are cultural relics, historical memorial construction, or locate at key communication ways, or there are critical pipe net work or underground facilities to be protected, the data in the brackets shall be used as limit.)2.Appraisal for earthquake-resistance of house2.1Basis of appraisal of defense against earthquake GB 50023-951.0.3 The existing constructions shall be divided into 4 categories, for which the checking computation and appraisal for structure shall meet the following requirements:Category A: checking computation for earthquake resistance and structure shall be practiced in accordance with rules specially decided.Category B: checking computation for earthquake resistance may be practiced in accordance with defensive intensity; for earthquake-proof structure, it may be one degree higher than normal, excluding that is 9 degree.Category C: Both checking computation for earthquake resistance and structure shall be in accordance with the requirement of earthquake resistance defensive intensity.Category D: At 79 degree, requirement of checking computation may be lower and earthquake-proof structure may be lowered by one degree. It is not necessary to do appraisal for those lower than 6 degree.2.2 General rules GB 50023-953.0.1 Appraisal for earthquake resistance of the existing construction shall include the following content and requirement:3.0.1.1 The initial information such as survey report, construction drawings, finishing drawings, and documents for acceptance of the project shall be collected; remedy shall be done in case information is not sufficient.3.0.1.2 Survey how the existing circumstance of the construction meets the initial information and the situation of construction property and maintenance, to reveal concerned defects on non-resistance of earthquake.3.0.1.3 According to factors such as specialty, structure arrangement, framework and earthquake-resistance load bearing capability of various constructions structures, corresponding appraisal method shall be adopted to make analysis of comprehensive earthquake resistance capability.3.0.1.4 Evaluation of entire capability of earthquake resistance of existing construction shall be made. To those that do not meet requirement in appraisal, a treatment plan on earthquake resistance and hazard-reducing shall be provided.3.0.4 The basic content and requirement for macro-control and structure appraisal for existing construction shall meet the following rules:3.0.4.2 When the horizontal and vertical surface, quality, rigidity distribution and side-load bearing elements such element brick wall of the construction are significantly not symmetric in the arranged plane, an analysis of hazard factor of earthquake torque effect shall be carried out. When there is discontinuity between upper and lower parts of the element or a mutation of rigidity distribution along the height exist, it is necessary to find out the weak location, which is then to be appraised in accordance with corresponding requirement.3.4.0.3 When the structure system is being inspected, it is necessary to find out the component or element, whose failure may lead to the whole system lost earthquake resistance capability or lost load bearing capability. When there is a house whose floor planes of the same story are at different elevations, or different types of structure systems are to be connected, requirement for earthquake resistance capability of the corresponding location shall be higher.3.0.5 For those elements of degree 6, checking computation for earthquake resistance is not necessary.4.1.2 For those of 8 to 9 degree, if the site of construction is located at a poor location such as an extruding hill mouth, high and isolated hill, non-rocky steep slope, river bank or edge of a side slope, evaluation shall be performed on the stability in earthquake, earth foundation slipping tendency, and possible danger of the construction.4.1.3 For category B constructions located at river bank or sea shore, when liquefied layer inclines towards river center or sea shore, an identifying judgement for danger of soil slipping or cracking after liquidation.4.2.6 When checking computation for load bearing capability of existing natural earth foundation is performed, a designing value of static load bearing capability of a long period pressed-to-dense base earth shall be used instead of design value of static earth load bearing capability. The former is resulted from the latter multiplied by the coefficient of long period pressing-dense earth soil.2.3 House of building block GB 50023-955.2.1 The structure system of existing house shall meet the following rules:5.2.1.2 Arrangement of horizontal