A factor or hazard causing illness, deterioration of human health during the working process according to the provisions of the law on occupational safety and health and health. Harmful elements to health include 06 main groups: Adverse microclimate; physical (e.g. noise, vibration); various dusts; toxic substances, chemicals, vapors; psychophysiology and ergonomics; occupational contact.
A zone or area at the site and adjacent areas with harmful factors exceeding the permissible threshold or not satisfying the provisions stated in relevant national technical regulations but not to the extent of causing injury or death to people.
The boundaries of areas inside and around the construction site where dangerous elements may appear causing damage to people, construction works, assets, equipment, vehicles due to the construction process of the works, determined according to technical standards, regulations and measures for organizing construction of works [point h clause 1 Article 1 of Law No. 62/2020/QH14].
Types of materials, components, products used in construction of works that meet the following requirements:
a) Comply with the provisions of the law on product and goods quality and other relevant specialized laws;
b) Materials, components, products with quality in accordance with QCVN 16:2019/BXD, QCVN 04:2009/BKHCN and Amendment 1:2016 QCVN 04:2009/BKHCN, comply with the provisions of the design documentation, in accordance with the national technical regulations and standards related to materials, components, products permitted to be applied in Vietnam;
c) Comply with the provisions of the law on construction and other relevant specialized laws on quality control before being put into use at the site.
Standards related to materials, components, products, survey, design, construction, installation, acceptance, use, maintenance, techniques (or measures) to ensure safety and health for workers when carrying out construction activities specified in 1.1.2 and permitted to be applied in Vietnam.
Hooks, chains, ropes, nets, buckets and other accessories used to attach or tie the lifted object to the lifting equipment but not a main part of the lifting equipment.
Principles based on the results of comprehensive research on the adaptation between technical means and the working environment with human capabilities in terms of physiology, psychology, in order to ensure the most effective labor, while protecting the health, safety and comfort of workers.
TCVN 9311-7:2012 ISO 834-7:2000 Fire – resistance test – Elements of building construction – Part 7: Specific requirements of columns
Foreword
TCVN 9311-7:2012 is completely equivalent to ISO 834-7:2000.
TCVN 9311-7:2012 is converted from TCXDVN 347:2005 (ISO 834-7:2000) according to the provisions in Clause 1, Article 69 of the Law on Standards and Technical Regulations and Point a), Clause 1, Article 7 of the Government’s Decree No. 127/2007/ND-CP dated August 1, 2007 detailing the implementation of some articles of the Law on Standards and Technical Regulations.
The set of TCVN 9311 under the general title “Fire-resistance tests – Elements of building construction” includes the following parts:
TCVN 9311-1:2012, Part 1: General requirements.
TCVN 9311-3:2012, Part 3: Guidance on the method of test and application of test data.
TCVN 9311-4:2012, Part 4: Specific requirements for loadbearing vertical separating elements.
TCVN 9311-5:2012, Part 5: Specific requirements for loadbearing horizontal separating elements.
TCVN 9311-6:2012, Part 6: Specific requirements for beams.
TCVN 9311-7:2012, Part 7: Specific requirements for columns.
TCVN 9311-8:2012, Part 8: Specific requirements for non-loadbearing vertical separating elements.
The ISO 834 set “Fire-resistance tests — Elements of building construction” also includes the following parts:
ISO 834-9:2003, Fire-resistance tests — Elements of building construction — Part 9: Specific requirements for non-loadbearing ceiling elements
ISO/DIS 834-10, Fire-resistance tests — Elements of building construction — Part 10: Specific requirements to determine the contribution of applied fire protection materials to structural elements
ISO/DIS 834-11, Fire-resistance tests — Elements of building construction — Part 11: Specific requirements for the assessment of fire protection to structural steel elements.
TCVN 9311-7:2012 is compiled by the Institute of Architecture, Urban and Rural Planning – Ministry of Construction, proposed by the Ministry of Construction, appraised by the Directorate for Standards, Metrology and Quality, and announced by the Ministry of Science and Technology.
1. Scope
This standard specifies the procedures that must be followed to determine the fire resistance of columns when tested on the column itself.
Columns are usually tested with all edges fully exposed to heat. However, in practice heat exposure is often less than four sides, so appropriate exposure conditions must be simulated.
Test results according to this standard may be applied to other untested element forms if those elements conform to the scope specified in different parts of this set of standards or when extended application is applied in accordance with ISO/TR 12470. As ISO/TR 12470 only provides general guidance, the analysis of extended application for a specific case should only be performed by experts in fire-resistant structures.
General guidance on test methods is provided in Annex A.
2. Normative references
The following referenced documents are essential for the application of this standard. For dated references, only the cited edition applies. For undated references, the latest edition of the referenced document, including any amendments, applies.
TCVN 9311-1:2012 1), Fire-resistance tests – Elements of building construction – Part 1: General requirements.
ISO/TR 12470, Fire-resistance test – Guidance of the application and extension of result.
ISO/IEC 13943, Fire safety – Vocabulary.
3. Terms and definitions
For the purposes of this standard, the terms and definitions given in TCVN 9311-1:2012, ISO 13943 and the following apply.
3.1. Column
Non-separating vertical loadbearing element of a building construction.
3.2. Controlled eccentricity
Designated distance measured from the vertical axis of the column to the point of application of the load.
3.3. Loading platens
Flat plates used between the loading equipment and each end of the column to ensure correct application of the applied load.
4. Symbols and abbreviated terms
Symbols and abbreviated terms appropriate to this test are defined in TCVN 9311-1:2012.
5. Test equipment
Equipment used in this test includes the test furnace, loading equipment, restraint, support frame and supporting devices specified in TCVN 9311-1:2012.
An example of the test apparatus is shown in Figure 1.
KEY:
1. Hydraulic jack 2. Loading frame 3. Test furnace 4. Column 5. Loading platens
Figure 1 – Example of test specimen arrangement for loaded column
6. Test conditions
6.1. Restraint and boundary conditions
Restraint and boundary conditions shall comply with the requirements specified in TCVN 9311-1:2012 and the requirements of this standard.
6.2. Loading
6.2.1. All columns shall be tested under the load calculated as specified in 6.3.a), b) or c) of TCVN 9311-1:2012 with reference to the opinion of the test sponsor providing the design structural conditions to suit. The properties of the materials used to calculate the load shall be clearly stated and sources of supply given.
6.2.2. When the proposed height of the test specimen is greater than the appropriate dimensions of the test furnace, the load shall be adjusted to suit the slenderness ratio of the loadbearing elements introduced into the test, so as to generate the full load level of the full-sized structure.
6.2.3. The ends of the test specimen shall be specifically designed and constructed to transmit correctly from the loading platens to the test specimen with the required conditions of fixity and eccentricity. The loaded faces at the top and bottom of the column shall nominally be parallel and perpendicular to the column axis to avoid the introduction of bending moments.
6.2.4. To protect the loading equipment from heat there shall be a splayed tube at each end of the test specimen. These tubes shall be designed to locate the column accurately and form an appropriate seal with the inside surfaces of the furnace and shall be appropriately fixed and supported to maintain the position of the column throughout the heating period.
The method used to provide the seal shall allow the test specimen to move within the limits of the furnace without affecting the transmission of load from the loading equipment to the test specimen or the fixity of the ends of the test specimen.
6.2.5. The loading system shall be able to accommodate the maximum permitted deformation of the test specimen.
7. Preparation of test specimens
7.1. Construction of specimen
In practice, where joints occur in the applied fire protection, any test specimen incorporating applied fire protection shall include at least one representative joint located near the mid height of the test specimen.
Where hollow encasement to a column exists, the hollow encasements shall be terminated to represent the exposure and fixing conditions as in practice. Gaps at the top of the column and between the hollow encasement and column shall be sealed where such conditions can exist in practice.
When testing a column incorporating applied fire protection, fabrication should ensure no artificial stresses are induced in the applied fire protection by the application of the load.
7.2. Size of test specimen
The test specimen shall be full size. For elements greater than 3 m high, the minimum size of test specimen exposed to fire shall not be less than 3 m. The overall height shall not exceed the heated height plus approximately 300 mm at each end. This additional height shall be kept to a minimum to prevent heat loss from the test specimen during testing and shall be used to locate the column within the loading equipment and to ensure adequate separation of the loading equipment from the heated gases inside the test furnace.
7.3. Number of test specimens
The number of test specimens shall comply with the requirements specified in TCVN 9311-1:2012.
7.4. Conditioning of test specimens
At the time of test, the strength and moisture content of the test specimen shall be approximately as expected in normal use. The test specimen shall incorporate any filling and jointing materials. Guidance on the conditioning of test specimens is given in TCVN 9311-1:2012. After equilibrium has been reached, the moisture content or state of dryness shall be determined and recorded. Any supporting construction including lining of the test frame need not comply with this requirement.
7.5. Installation of test specimen and restraint
7.5.1. The column ends shall be fully rotationally restrained or pin jointed to simulate the conditions of use in practice. However, data may not be transferred directly from one restraint condition to another. Where comprehensive information is required, several tests should be carried out with different fixity conditions for the column ends. Where one or both of the ends of the column are pinned, ensure that there is no frictional rotational restraint.
7.5.2. When a pinned connection is used, a spherical-seated bearing, cylindrical roller or knife edge shall be placed between one end of the column and the loading equipment. When cylindrical rollers are used, the axis of the roller shall be parallel to the weak axis of the column.
7.5.3. Hinged bearings shall be mounted between two loading platens (one in contact with the loading equipment and the other in contact with the column) to improve the distribution of loading on the cross-section of the column.
7.5.4. The hinged bearings shall be accurately set on the central axis of the column so that the eccentricity after loading is only L/500 (L is the buckling length of the column) or not greater than 7 mm. Particular attention shall be paid to minimizing friction within the bearings.
7.5.5. When fixed-end conditions are used for the column, contact between the loading platens and the ends of the columns shall be ensured.
8. Installation of instrumentation
8.1. Thermocouples
Thermocouples shall be installed to measure the furnace temperature and shall be distributed to obtain a reliable indication of the temperature adjacent to the exposed faces of the test specimen. Thermocouples shall be attached and positioned in accordance with the requirements of TCVN 9311-1:2012.
There shall be at least six thermocouples in the furnace, arranged in pairs on opposite sides of the test specimen at 1/4, 1/2 and 3/4 points along the heated length.
The thermocouples shall be positioned (100 ± 50) mm from the edge of each face of the test specimen, or not less than 400 mm to the top of the furnace, and not displaced more than 50 mm from their original position during the test. Each thermocouple shall be oriented so that its “A” face is directed towards the back wall of the furnace and the insulation section faces the test specimen.
8.2. Specimen thermocouples
When columns are constructed from steel or other materials and information about high-temperature characteristics of the material is available, measurement of the specimen temperature may allow the failure of the specimen to be predicted and the results to be used in engineering assessment. Welding, screwing or peening are appropriate methods of attaching thermocouples to steel construction. It should be ensured that a minimum of 50 mm of wire is left in the isothermal region leading to the junction for each thermocouple.
Thermocouples shall be placed at four different heights, with at least three thermocouples at each height. The upper and lower heights measured from the ends of the heated length of the column shall be 600 mm, and the two intermediate heights shall be evenly spaced. Typical thermocouple positions at each different height are shown in Figure 2.
Figure 2 – Typical thermocouple positions
8.3. Deformation measurements
The zero point of the test shall be the axial deformation measured after load is applied, just prior to the test, before heating and after the deformation has stabilized.
The axial deformation of the column shall be measured at 1-minute intervals throughout the test period using displacement transducers of the variable capacitance or dial gauge type.
9. Test procedure
9.1. Application of load
The application and verification of load on columns shall be in accordance with TCVN 9311-1:2012 and 6.2 of this standard.
9.2. Test furnace control
The measurement and control of conditions such as temperature and pressure in the test furnace shall be in accordance with TCVN 9311-1:2012.
9.3. Measurements and observations
Measurement and observation of the test specimens appropriate to the criteria of loadbearing capacity, integrity and thermal insulation shall be carried out in accordance with TCVN 9311-1:2012.
10. Performance criteria
The fire resistance of columns shall be assessed against and expressed in terms of the loadbearing capacity criterion specified in TCVN 9311-1:2012.
11. Assessment of test results
The test shall be considered valid if it is conducted according to the guidance contained within the limits characteristic of the relevant requirements for test apparatus, test conditions, specimen preparation, instrumentation and test procedure and shall comply with the requirements of this standard.
The test shall also be considered valid if the fire exposure conditions related to furnace temperature, pressure and ambient temperature exceed the upper limits of the tolerances specified in this standard.
12. Presentation of test results
The results of the fire resistance test shall be presented in accordance with TCVN 9311-1:2012.
When a test is performed on a specimen subjected to an engineering load specified by the test sponsor as less than the maximum that could occur under an accepted code of practice, the loadbearing capacity shall be expressed in the test result designation using the term “restricted”. Details shall be included in the test report concerning these load deviations.
13. Test report
The test report shall be in accordance with TCVN 9311-1:2012.
ANNEX A (Informative) GENERAL GUIDANCE ON THE TEST METHOD
A.1. General
The test procedure in this standard is presented on the assumption that it is being applied to the testing of vertical members subjected to compressive loading. The method is also suitable for the assessment of members subjected to tensile loading, i.e. vertical tie members. In that case, the bearing equipment would need to be a mechanical attachment capable of transmitting tensile loads.
A.2. Design considerations
A.2.1. End-bearing conditions
The load that a column can sustain depends on the end conditions. For slender columns that are assumed to behave as pinned, even small forces due to friction within the bearing can increase significantly the loadbearing capacity. In a fire test, unintentional restraint at the ends of a column can result in an apparently increased fire resistance. Spherical-seated or cylindrical bearings may be used to provide free rotation.
A.2.2. Conditioning of end-bearing tubes
Where end-bearing tubes consist of concrete encasement around the column ends, it is important that these are conditioned and equilibrated in a similar manner to the test specimen itself, to avoid spalling, excessive steam generation or cooling effects during the test.
A.3. Loading
Columns should be tested under the loading and bearing conditions appropriate to their design in the absence of fire. It is usually not possible to reproduce in a test the changes of edge moment or loading that may occur in an actual fire.
Where it is not possible to reproduce the final conditions of use in practice, representative test conditions may be idealized and the test load calculated on the basis of these conditions.
Where it is not possible to reproduce the final conditions of use in practice, representative test conditions shall be idealized and the test load shall be calculated on the basis of these conditions and the fixity employed.
A.4. Temperature measurement
The positioning of thermocouples in the specimen should be such as to yield the most useful information concerning the temperature history of the column.
Where composite constructions are used (e.g. hollow steel sections filled with concrete) it may be useful to identify the temperature of the individual components as well as the thermal gradient through the construction and this may allow more detailed assessment of the data.
Thermocouples may be used to measure the temperature between the column and the applied fire protection. Information obtained in this way may allow extrapolation of protection with different insulation materials for different column types and materials with different limiting steel temperature.
A.5. Performance of columns in test
Axial deformation of vertical elements may occur from thermal expansion, shrinkage due to the drying out of components, or from axial deformation under load due to loss of strength or cross-sectional area.
A steel column may expand due to increasing temperature until such time that it can no longer support the test load. When it can no longer provide support, contraction will occur as, under the action of the load, the steel buckles locally or generally. Thus the measured length of the column will reach a maximum and then reverse.
For concrete-filled steel tubes it will be more complex. When the tube is loaded, the initial deformation should be similar to that for the structural steel column. As the steel tube is heated, it will deform and shed load to the concrete core, whilst still keeping the concrete confined. The concrete will continue to carry the test load, until it can no longer function.
Timber columns are less thermally conductive than steel columns. When tested they show little initial expansion and the average temperature of the loadbearing cross-section does not change. After some time charring occurs and the cross-section of the column reduces and axial deformation in the direction of the applied load occurs.
ANNEX B (Informative) FIELD OF DIRECT APPLICATION OF TEST RESULTS
The result of the fire resistance test is applicable to a similar untested column provided that the following are true:
a) The length is not increased;
b) The load and eccentricity are not increased;
c) The edge conditions are not changed;
d) The cross-sectional dimensions are not reduced;
e) The characteristic strength and density of any substantive material is not changed;
f) The number of exposed faces is not changed;
g) There is no change in the cross-sectional design (such as the reinforcement pattern)
