Temperature Fields In Section Research Articles

Analysis of flatness and critical crown of hot-rolled strip based on thermal–mechanical coupled residual stress analytical model

Residual stress is introduced during hot-rolled strip production due to various factors, such as temperature distribution, crown change, and metal transverse flow. Excessive residual stress can cause flatness defects in the strip, while insufficient residual stress may result in deformation during subsequent cutting. To explore the mechanism of residual stress formation in hot-rolled strip and how to control it, an analytical model for the coupling of temperature, crown and residual stress is established. Firstly, based on the symplectic space Hamiltonian system, an analytical solution for the strip cross section temperature field in each inter-stand zone is obtained. Then the residual stress analytical model is derived based on the fiber rod model combined with the law of volume invariance, lateral metal flow function and high temperature stress relaxation phenomenon. Meanwhile, to verify the accuracy of the analytical model, a multi field coupled finite element model based on the measured data validation is established. The calculation results of the analytical model are in good agreement with the finite element model. Furthermore, the buckling model of strip in symplectic space Hamiltonian system is derived, and the critical buckling stress of different strip flatness defects is directly calculated. Finally, the residual stress analytical model is combined with critical buckling stress to calculate the critical exit crown ratio to keep the strip flat.

Experimental Study on Fire Resistance of Concrete Beams Made with Iron Tailings Sand

In order to measure the effect of iron tailings sand replacing natural sand on the fire resistance of concrete beams, five full-scale iron tailings sand concrete (ITSC) beams and two natural sand concrete (NSC) beams were conducted to fire testing under dead load and rising temperature conditions. The section temperature field, mid-span displacement, failure form, and fire resistance limit of ITSC beams under fire were analyzed. The main influence factors included different ISTC strengths (C30 and C40) and constraints. The analysis results were compared with those of NSC beams. The results show that the complete replacement of natural sand with iron tailings sand had little influence on the temperature field of concrete and reinforcement in simply supported beams and continuous beams under fire. The fire endurance of the ITSC simply supported beams was similar to that of NSC simply supported beams. When exposed to fire, the higher the strength of the ITSC, the better the fire resistance of the beam. The fire endurance of continuous beams was higher than that of simply supported beams. On the basis of the analysis of the fire resistance performance, it was found that iron tailings sand can replace natural sand to formulate concrete beams.

Temperature Load Mode of Bridge in Permafrost Region of Qinghai–Tibet Railway

The Qinghai–Tibet railway is the plateau permafrost railway with the highest altitude and the longest line in the world. The natural conditions along the line are harsh, with many unfavorable factors such as low temperature, strong ultraviolet radiation, and large changes in daily temperature, resulting in frequent bridge damage. In order to study the bridge temperature field and its effect in the permafrost region of the Qinghai–Tibet railway, a long-term field test was carried out, and a calculation model of sunshine temperature field of concrete two-piece T-beam was established based on the principle of meteorology and heat transfer. On this basis, the beam temperature difference load mode, beam section temperature distribution law, and temperature effect were obtained. As revealed, the daily temperature difference of the Qinghai–Tibet railway bridge is large in winter, which is related to the ground’s effective radiation and surface reflectivity, and the maximum value has exceeded the current codes. The beam section temperature field shows “internal heat and external cold” in the morning and “internal cold and external heat” from noon to evening. Under the action of strong radiation and large temperature difference, bridge displacement occurs frequently, by which it is easy to cause damage to rail fasteners and bridge bearings. Based on the field test and finite element analysis, the bridge temperature difference load mode was proposed, which makes up for the deficiency that the relevant codes do not consider the plateau’s special climatic conditions and can provide a reference for the construction of plateau railways such as the Sichuan–Tibet railway.

Semi-analytical thermo-mechanical model for the shield tunnel segmental joint subjected to elevated temperatures

The segmental joint is the most critical component for determining the mechanical response of concrete segmental linings in a shield-tunnel structure. Existing segmental joint models have been developed mainly for the analysis of segmental lining design, but in the event of a fire, the conditions that a tunnel joint may experience could well exceed the normal design range. Consequently, the validity of the existing segmental joint models becomes questionable. In this paper, an improved semi-analytical thermo-mechanical model is derived based on the general plane joint model to consider the thermal effect induced by elevated temperatures. As a benchmark for the development of the model, a laboratory experiment was conducted on concrete lining segmental joints under elevated temperatures. The general heat transfer and special heat flow invading through the joint were deduced by theorical and numerical methods. A finite element (FE) model is developed and calibrated against experimental model tests, whilst the FE model is employed to generate the required parametric data, from which a fitting function is created. A temperature adjustment coefficient is introduced to improve the calculation of the joint section temperature field. The influence of elevated temperature and axial force on the bending moment of a segmental joint is also incorporated according to the stress state of the joint section. The validation of the proposed semi-analytical thermo-mechanical model is demonstrated through comparisons with the results of fire tests. Finally, the influences of the heating curves, bolt location, and axial load on the rotation stiffness of the joint are investigated using the proposed model.

Experimental Research on the Temperature Field Distribution of Circular CFST Section

This paper in order to study the circular CFST section temperature field distribution was caused by temperature variation, which the temperature change testing under the outdoor environment and artificial climate simulated test chamber, measuring the temperature field of the CFST component and the plain concrete control specimen under different temperature variation conditions. The test results showing that the temperature field of the CFST and the plain concrete is basically same. The cross section temperature fields basically presented uniform distribution when there was no sunshine and under the action of sunshine, the temperature field of the specimen section showed a non-uniform distribution. In both conditions, the specimen section temperature field shows a phenomenon that the temperature change from outside to inside is increasingly lag behind, and the specimen section maximum temperature difference mainly depends on the solar radiation and the range of temperature changes.

Study on Section Temperature Field of Concrete-Filled Double Steel Tubular Columns under Fire

Finite element model was built in order to study the section temperature field of concrete-filled double steel tubular columns through the software of ANSYS. Moisture of concrete and thermal contact resistance were considered in the model. Based on the Eurocode 2, specific heat of concrete was modified in order to consider the effect of moisture. Contact elements were created in the interface between steel tube and concrete in order to consider the effect of thermal contact resistance. The effects of diameter of steel tube and type of aggregate to section temperature field were studied. Distribution of section temperature field is given on the concrete-filled double steel tubular columns, which provides the basis for the analysis of fire resistance capability.

Temperature Field Analysis of Concrete Filled Steel Tube Reinforced Concrete Columns in Fire

In this paper, temperature field analysis of concrete filled steel tube reinforced concrete columns in fire has been carried on. A finite element model for concrete filled steel tube reinforced concrete columns in fire is developed by ABAQUS. The cross-sectional temperature field distribution regularity of concrete filled steel tube reinforced concrete columns in fire has been obtained. Parameter analysis such as fire duration time and steel ratio on the column section temperature field is conducted, and this provide the reference for the further analysis of concrete filled steel tube reinforced concrete columns.

Influencing Factors Analysis on Temperature Field of Reinforced Concrete Columns under Fire

Using the finite element analysis software ABAQUS, the section temperature field of reinforced concrete columns under fire was analyzed. On this basis, the influence of the section size, the number of heated surface and the time of fire on the surface temperature were analyzed. Calculations indicate that the impact of the section size on temperature field cannot be considered when one surface was heated, three or surrounded by fire-sectional dimensions the influence was time-related. When the cross-sectional size reaches a certain value, the number of exposed surface on the temperature field can be neglected. Sectional temperature increased by time and the temperature rise rate is high at start then slow down close by fire surface, however, the rate is more stable all the time at internal surface.

Numerical Analysis of Temperature Field of Cup-Shaped Frozen Soil Wall Reinforcement at Shield Shaft

Determining the freezing reinforcement required range and reinforcement method, acquiring the development and distribution pattens of frozen soil wall temperature field are the key issues needed to be addressed when using cup-shaped horizontal freezing method for the soil reinforcement of shield tunnel ends. Based on the shield launching project of the west side of Yixianqiao station in Nanjing subway line 2 and the finite element numerical analysis software, the development and distribution patterns of the cup-shaped frozen soil wall reinforcement were studied. The numerical simulation showed that, after freezing for 30 days, the x = -1 section temperature field evenly distributed around the center tube. And the freezing temperatures within the outer tubes were usually below-20°C. The temperature field circled around the center tube and the temperature gradually increased from the inside to the outside to 0°C within the range of about 1 m outside the outer tubes. The freezing temperatures within the range of 2 m thickness of the cup-bottom in the y= 0 section were usually below-10°C and the temperatures changed from inner to outer significantly until rising to 0 °C at the freezing pipe ends of the cup-bottom. Freeze wall formed firstly in the outer tubes, then the intermediate tubes, and lastly the outer tubes. And the freeze wall closure time that closed cup-shaped frozen soil wall formed was 15 days in this designed freezing method.

Analytical solution of temporary temperature field in half-infinite body caused by moving tilted volumetric heat source

In this work, analytical solution of temporary temperature field in half-infinite body caused by moving heat source tilted towards the direction of motion is presented. In solution is assumed volumetric heat source with Gaussian power density distribution with respect to depth. Calculations of temperature field in cubicoidal steel element have been conducted for three tilt angles between heat source and perpendicular to the surface of object: −30°, 0 and 30°. Results of calculations are presented in the form of temporary and maximum temperature fields in sections of element and thermal cycles at selected point.

Experimental Investigation on the Fire Resistance Performance of L Special-Shaped Steel Reinforced Concrete Columns

Four full-scale SRC columns with special-shaped cross section were experimentally investigated in fire following ISO834 standard heating process and were implemented in the compression test after fire .The section temperature field after two hours of fire, deformation laws under fire and the mechanical behaviors after fire were got. Find: (1) Bond slips between concrete and steel were small which indicates that concrete and steel can work together. (2) Reasonable way with steel cross-section had a significant effect on the mechanical properties of columns. (3) The two sides of SRC special-shaped column were under fire conditions, sections were damaged. When the load was at the centre of the cross section, columns were in the state of axial compression before fire and the state of eccentric compression after fire.

DEFORMATION AND STRENGTH PROPERTIES OF REINFORCED CONCRETE BEAMS UNDER THE PRESSURE AND TEMPERATURE EFFECTS

The procedure of a limit fire-strength of the loaded steel-concrete beams. Concrete is submitted by the treephase environment: a firm bearing material (skeleton); set of liquid inclusions in interstices; gas in interstices. The temperature fields in section of a beams pays off in view of internal border of steam formation; the condition of a beams with the account double intense condition of concrete is investigated tensely–deformed.

Temperature displacements in naturally twisted turbine blades under conditions of nonuniform heating

We deduce and analyze design-basis formulas for the evaluation of the degrees of temperature torsion, temperature deflections in the planes of minimum and maximum stiffness, and temperature elongation of the pen of a naturally twisted turbine blade under the conditions of nonuniform heating. We present a practical example of the numerical calculations of temperature displacements in the peripheral section of the pen of a blade subjected to thermal cycling. In this case, the process of nonuniform heating of the naturally twisted blade is performed by a gas flow with cyclically varying temperature. To find the temperature fields in sections of the blade, we determine the local heat transfer coefficients along the perimeter of the profile separately for the periods of heating and cooling.