- •Requirements for building structures and general principles of their designing
- •Basis of calculation of structures and foundations for limit states
- •The concept of calculation based on the first group of limit states
- •The concept of the calculation on the second group of limit states
- •3. Regulatory and calculated values of materials resistance and loads
- •5.1. Constant loads
- •Account settlement and normative properties of materials load coefficients in calculating structures for first and second groups of limit states
- •4. Load and impact
- •4.1. Classification of loads by the time of operation.
- •5. Characteristic values of loads and safety factors for the load
- •1. Field of application. Advantages and disadvantages of mc.
- •2. Construction Steel
- •3. Physical and mechanical properties of steel
- •Sample for tension trial; b) Diagram of tension of steels
- •4. Aluminum alloys
- •5. Assortment of rolled profiles
- •1) Plate; 2) equal-shelf angle; 3) unequal-shelf angle; 4) channel
- •1. Calculation of metal construction elements for limit states
- •1.1. The structure of rated formulas
- •Inner effort r γс
- •3. Calculation of elements on the central compression
- •4. Calculation of elements on a bend
- •1. Welds. Understanding
- •1.1. Typesofwelds
- •3. Calculation of the fillet weld tension and compression
- •1. General. Range of application.
- •3. Design rules centrally compressed steel columns
- •1. Understanding. Scope beams
- •Stress in the steel I-beam: a) the notation for the calculation of composite welded beams, b) diagram ах, in the diagram j хх
- •2. Calculation of rolled beams
- •3. Girder cells
- •3.4 Components and parts of steel beams
- •4. Modern beams
- •1. Understanding. Types of trusses and general dimensions
- •2. Calculation and design of trusses
- •1. Concrete structure
- •2 . Classification concrete. Concrete Stamps
- •3. Mechanical properties of concrete
- •3.1. Cube strength
- •3.2. Prism strength
- •3.3. Axial tensile strength
- •3.5 Strength of concrete under long-term load
- •3.6. Strength of concrete at multiple repeated loads
- •4. Concrete classes
- •2. Loss of prestressing
- •2. Conclusion of the settlement equations for elements of any profile
The concept of the calculation on the second group of limit states
The purpose of this calculation is to prevent any of the second band limit states. It is believed that the limiting state of the second group will not occur if the condition is satisfied
f < [f], where f is the fixed from calculating the deformation (displacement, rotation angle, width of the crack opening, etc.) from external standard loads.
[f] is the standard (maximum allowable) structural deformation (displacement, rotation angle of the crack opening width, etc.), which is determined in accordance with the requirements.
3. Regulatory and calculated values of materials resistance and loads
Calculations under the limiting conditions of the first and second groups as the main strength characteristics of the material its resistance is determined, which can take the normative and calculated values:
Rn is the normative resistance of the material, the main parameter of materials resistance to external influences and it is established by the relevant chapters of building regulations. The physical meaning of regulatory resistance Rn is a control or rejection characteristics of material resistance with the provision of not less than 0.95%;
R is the calculated resistance of material, determined by the formula R = Rn/γm,
whereγm is safety factor for material, which takes into account possible variations in resistance of a material to the unfavorable direction from the normative values,γm> 1.
Safety factor for material accounts for the discrepancy of materials actual work in constructions and his work in the test samples, and the possibility of falling into the structure of material with the properties established in SES.
Rated resistance in the calculations should be taken with a service factor. γc is the factor of conditions of work, which takes into account the characteristics of the materials , elements and compounds, structures and buildings in general, if the peculiarities have systematic character, but they are not reflected in the calculations by the right way (keeping the temperature, humidity, corrosive environments, proximity settlement schemes, etc.). In the derivation of design formulas and writing formulas, sometimes the calculated resistance multiplied by the γc is not indicated, but if working conditions factor differs from unity , it is always necessary to multiply the calculated resistance , i.e. in all formulas where R, R γc must be substituted instead of R.
Regulatory and calculated values are set not only for resistance of materials, but also for loads, given the variability of their values or their inability to determine with absolute certainty:
Nn is the normative load, which is calculated according to the project sizes of constructions.
N is the rated load, which is defined by the formula N =Nn •γf,
Whereγf is safety factor for loads, which takes into account possible deviations of loads in the unfavorably (more or less) direction from their normative meanings.
Norms also take into account the possible consequences of accidents. That calculation is conducted with the help of safety factor for liability γn, which are multiplied by the estimated load, which leads to a decrease or increase their value
N • γn, whereγn is the safety factor for liability. It takes into account the economic, social and environmental impacts that may arise as a result of accidents. On account of the fact that the advance of limiting conditions related to the second group is not associated with the loss of bearing capacity of structures or buildings in general, load resistance materials as well as the resistance of soils, which are used in the calculations for this group, are accepted by numerically equal normative values which are called service.
Accordingly, normative (service) load Nser and normative (service) resistance Rser are considered to be rated for calculations on limit states of the second group.
In the calculations for the first group of limiting conditions that are associated with the software bearing capacity of the construction (building), take the calculated values: calculated load N and calculated resistance of material R.
On executing calculations relating to the first and second groups of limiting states it is necessary to take into account the values of loads, strength of materials, and the coefficients according to the table.