Effects Of Temperature Loading Research Articles

A Numerical Study on the Fire Induced Collapse of a Real Life Warehouse Structure Based on Post-Fire NDT Results

Fires being a Low-Probability High-Consequence problem, can have a big impact on the structures due to their occurrence; irrespective of the construction materials. Even, the damage might lead to structural collapse. Such failures have warned to check the impact of fire on structural elements, which is frequently overlooked in popular design guidelines. Warehouses are used for the storage of different types of commodities; however, the vulnerability of these structures during fire event depends on the storage materials and other factors. Such a warehouse with steel roof trusses supported over Reinforced Cement Concrete (RCC) frame, located at Kolkata, suffered one of such severe fire-induced damage; and the roof truss system along with some portions of the brick masonry walls got totally collapsed. The information about the structure including its design data is presented along with the site observations after the fire incident, and the results of various Non-Destructive Tests (NDTs) performed over RCC frame elements. A severe fire of 8-hour duration led to a huge increase in temperature, which is considered to be the main reason of the progressive collapse of the entire warehouse structure. To better understand the failure of members due to temperature load, the present study aims to analyse a numerical model of the damaged structure in the Finite Element (FE) Framework. The roof truss, RCC frames and brick masonry walls are modelled; and temperature load is applied along with self-weight load to check the effect of incremental temperature on various structural responses of the warehouse. The temperature-dependent material properties are considered in the analyses; as applicable. Results have shown that there is a significant effect of temperature load, which gets worse with increasing temperature. The connection between roof truss and columns also contributes to the extent of damage in the truss supported over RCC frames; as evident from the numerical analysis. The present study seems to present a clear view about the fire-induced structural collapse of a real-life warehouse structure

Analysis of the Thermal Effects on the Performance and Reliability of Post‐Tensioned Integral Abutment Bridges

AbstractThere are cases where the common approaches used to assess the temperature loading effects may not be sufficient, especially in the case of integral abutment bridges (IABs). In IABs, the incorrect choice of the design temperature may result in an unwanted tensional state in the bridge decks and additional loads on the abutments. For post‐tensioned bridges, the combined effects of excessive temperature loads and loss of tension in the post‐tensioned cables due to time‐dependent phenomena like relaxation in steel and shrink‐age and creep in concrete may lead to probabilities of exceedance of serviceability (or ultimate) limit states that exceed the code specifications and/or desired levels of safety, and to cascading negative effects on the operation of the road infrastructure. This research aims at assessing the sensitivity of IABs to the long‐term effects of temperature loads and, in a second step, quantifying the probability of exceedance of relevant serviceability limit states.

Reliability of super-slope bridge-rack system on rack railway

ABSTRACT During the operation of rack railway on super-slope bridges (especially under temperature load), structural deformation of bridge-end is much larger than that of rack due to the difference of structural continuity between bridge and rack, which greatly increases local stress in rack, damages rack and fastener, and seriously threatens the operation reliability. To investigate the reliability of rack caused by temperature load and nonlinear dynamic interaction between super-slope bridge and rack, a detailed vehicle-rack(rail)-bridge coupled dynamic model is established with consideration of nonlinear dynamic meshing behaviour of gear-rack system and nonlinear dynamic contact behaviour of wheel-rail system. Then a field test is performed to obtain the basis dynamic behaviour of rack railway and validate the established numerical model. On this basis, the effects of temperature load, gear-rack meshing behaviour and wheel-rail contact behaviour on deformation and internal stress of rack-bridge system are investigated. Finally, the method to guarantee the structural reliability of rack railway on super-slope bridge is proposed. Results show that rack deformation nearby bridge gap is highly inconsistent with bridge deformation subject to different loads, and the internal stresses in rack and bolt exceed limit values written in relevant code, which seriously threatens the reliability of the rack structure. The maximum rack stress is 898 MPa, which exceeds the tensile strength of rack. The maximum shear stresses of bolts between fastener and rack and between fastener and sleeper are 1510 MPa and 656 MPa respectively, which exceed the shear strength of bolts. According to the calculation results in this paper, elastic fastener is suggested to be used to connect rack and sleeper, which can effectively reduce stress in rack and bolt, and improve the reliability of the rack structure.

Static and dynamic response characteristics of a ballastless track structure of a high-speed railway bridge with interlayer debonding under temperature loads

The ballastless track structure of a high-speed railway (HSR) undergoes interlayer debonding during its service due to train loads, environmental loads, and construction. A CRTS Ⅱ ballastless track slab structure is a longitudinally-continuous reinforced concrete structure, and the temperature load is a major factor in the occurrence of interlayer debonding. However, the effect of temperature loads on the static and dynamic response of the CRTS Ⅱ ballastless track structure of an HSR bridge following interlayer debonding is unknown. This study established a finite element simulation model of a ballastless track structure over a bridge and a vertically-coupled dynamic vehicle–track–bridge simulation model. The deformation generated by the track structure at temperature loads was inputted as track irregularity to the dynamic simulation model, and the change laws of the deformation and dynamic response of the track structure under different temperature loads was studied. The results showed that under different temperature loads, the ballastless track slab first undergoes longitudinal deformation, followed by transverse deformation. On this basis, the dynamic response of the HSR ballastless track structure over a bridge with interlayer debonding was found to increase with increasing temperature loads, while the frequency band changed from single to complex. This study not only provides insights into the effects of temperature loads on track structure damage, but also lays a theoretical foundation for the development of maintenance and repair plans for railroad departments.

Effects analysis of thermo-mechanical loads on classified damage characteristics with the equivalent cylinder head model

As a vulnerable part of diesel engine, cylinder head is periodically subjected to the thermo-mechanical coupling loads. While due to the restriction of complex structures and working conditions, it makes the damage mechanism of thermo-mechanical coupling still unclear. In this research, thermo-mechanical responses are predicted successfully by load spectrums and the Sehitoglu theory. Then the effects of working loads on classified damage characteristics are analyzed with the equivalent cylinder head model. The results show that the deviations of temperature and stress are, respectively, within 10°C and 30 MPa, and it verifies the effectiveness of simulated component. Operating speed takes the greatest effect on the thermo-mechanical characteristics, and bolt force and gas pressure are negatively correlated with the responses of stress and strain. Fatigue life and damage are determined by the values of working loads. The effect of temperature load is the most dominant, MechDam and OxidDam increase substantially when operating speed exceeds 3500 r/min. The research will provide a theoretical reference for engineering design and optimization of cylinder head.

Dynamic stability of a cracked pipe conveying fluid under thermal loads

In the paper is investigated the effect of temperature load and crack position on the dynamic stability of a cracked straight pipe conveying fluid. The static scheme of the investigated pipe is a beam with restricted horizontal and vertical displacements at both of its ends. The velocity of the transported fluid is constant. The Galerkin method is applied for the solution of the differential equation of the transverse vibrations of the pipe. The differential equation is reduced to a first-order differential equation system. The system of differential equations is transformed and rewritten in a matrix form. The roots of the characteristic equation of the system are obtained by solving the generalized first order eigenvalue problem. A numerical solution for a cracked pipe conveying fluid with specified geometric and physical characteristics has been carried out. The temperature load, the position of the crack and the critical velocity of the fluid are considered as parameters of the problem. The results show that the temperature load and the crack position affect the vibrational characteristics of the pipe, as well as its critical velocity.

Theoretical Analysis on Reinforced Concrete Bridge from Non-linear Temperature Effect

Abstract The paper presents a theoretical analysis that models the effects of temperature load induced on a two-pole, twobox reinforced concrete bridge. Implemented was theoretical analysis of thermodynamic effects, which was performed on a closed double-box reinforced concrete bridge structure. The modelling and analysis only considered the upper part of the load-bearing bridge structure. This type of bridge was selected to present the results of this study which analysed the worst effects of temperature acting on the bridge structure.

Determining the features of loading the bearing structure of a multifunctional car under operating modes

This paper substantiates the modernization and commissioning of a railroad car for high-temperature, bulk/loose cargoes in order to improve the efficiency of railroad transportation. A feature of the car is the presence of an open-type boiler, which is made of heat-resistant material. To prevent splashing of transported cargo, it is possible to use a removable cover, which is attached to the top of the boiler. The boiler of the car was calculated for strength under the main operating modes. The vertical load on the boiler was taken into consideration while accounting for the transportation of bulk cargo, as well as longitudinal, and the effect of temperature load. The strength was calculated by the method of finite elements. It is taken into consideration that the boiler is made of composite heat-resistant material. The calculation results showed that with the considered load modes, the strength of the boiler is ensured. The dynamic load of the boiler was mathematically modeled at car shunting. The calculation was performed in a flat coordinate system. Solving the mathematical model of the car dynamic load has established that the maximum acceleration that acts on the boiler is 36.5 m/s2. The dynamic load of the boiler was simulated. The dislocation fields and numerical values of accelerations that act on it were determined. The maximum acceleration, in this case, is concentrated in the bottom of the boiler; it is 37.4 m/s2. To verify the dynamic load model, the F-criterion was used for calculation. It has been established that the hypothesis about the adequacy of the model is confirmed. The study reported here could contribute to improving the efficiency of railroad transport operation and advancing the design of multifunctional car structures.

К вопросу о точности определения температуры огневого воздействия по следам пожара

After the fire is extinguished, it is required to study a set of the parameters, the most important of which is the temperature of fire exposure. The material of building metal structures, including hazardous production facilities that are in the zone of high temperatures, is undergoing changes. According to them, the magnitude of the temperature effect is determined, that is, metal structures act as natural thermal witnesses. Currently, the temperature effect is assessed visually by the colors of thin oxide films (tint colors) on the metal structures surface. It is experimentally proven that such an assessment is subjective. Recommendations based on this method cannot be considered sufficiently reliable. The purpose of the conducted study is to determine the effect of temperature loading on the hardness and magnetic properties of the carbon building steels. During heating and subsequent cooling, two synergetically affecting each other processes occur simultaneously in steel: a change in the structure and properties of the base metal, as well as the appearance of oxide films on the surface. It is established that the characteristics of the metal — hardness and coercive force do not correlate with each other in all the temperature ranges of heating. However, each exposure temperature corresponds to only one pair of hardness and coercive force values. Based on the results of the conducted experiments, the method was developed for determining the temperature effect by a complex change in the hardness and coercive force of the steel structures. The proposed method will allow to improve the reliability of expert opinions on the possibility of further operation of the buildings and structures after a fire.

Structural response analysis of conductive ethylene–propylene–diene monomer rubber composite pavement under validated temperature field

Conductive ethylene–propylene–diene monomer rubber composite material (EPDM) is a new type of active electric heating deicing material. It has good heat generation and mechanical properties. In this study, in order to study the effect of the addition of EPDM on the response of the pavement structure, the composite material was laid under the asphalt layer in the pavement structure in a full-width paving method. A three-dimensional finite element model of EPDM pavement structure was established and the pavement heating temperature field was simulated. The simulated temperature field of road surface was verified by an outdoor heating test. The structural response of EPDM pavement under three different loading conditions was analyzed by using the ANSYS static structural analysis module. The structure response was analyzed from three indicators of bottom tensile stress, surface deformation, and equivalent stress. The results show that under the static load of the vehicle, the addition of EPDM composite material can reduce the cracking risk of the asphalt pavement; The temperature load caused by the active heating of the road surface is the main factor causing the damage of the EPDM road surface; The weakest part of the entire pavement structure is the lower asphalt layer close to the composite material, especially at the center of the wheel load action spacing. This study can provide a reference for future practical engineering applications of EPDM pavements and attract attention to the effect of temperature loads generated by active snow-melting pavement heating on the structural response of the pavement.

Effect of temperature loading on the performance of a prestressed concrete bridge in Oklahoma: Probabilistic modelling

Spatial and temporal temperature variations in bridge structures due to changes in the surrounding climate cause bridge expansion which, if restrained, may induce secondary stresses in structures. Temperature effects have always been considered to be one of the most critical issues in the performance of traditional Prestressed Concrete (PC) bridges. In order to (1) develop an efficient temperature loading model for predicting bridge temperature-induced response; and (2) develop guidelines addressing the effects of temperature loading in reliability-based condition evaluation, numerical and analytical studies were conducted on a PC girder bridge in Oklahoma, USA. This paper focuses on the probabilistic modelling of temperature loading. Firstly, a heat transfer model was established using hourly input climate data to estimate the temperature distribution, and compared with monitoring counterparts for calibration. Secondly, the validated analytical model was employed to investigate the effects of thermal properties of concrete by a parametric analysis; Based on extreme environmental conditions from the 20-year climatic data and analytical results, probabilistic models of uniformly distributed temperature fields and temperature gradients were proposed, and the temperature loading value with a 75-year return period was determined and compared with recommended value in the AASHTO LRFD. The proposed temperature loading model can aid engineers in predicting the thermal behavior of PC bridges in Oklahoma, USA.

Effect of uniform temperature load on design of long reinforced concrete structures without expansion joints

This study presents an investigation on the design of long reinforced concrete (RC) structures subjected to uniform temperature load by considering three RC frame building models with different lengths of 45 m, 135 m, and 270 m using Etabs. The uniform temperature load is considered being the change from the annual average highest to lowest air temperature at the construction site in the case of unavailable temperature data of concrete. The analysis results indicate that the uniform temperature load mainly influences on the internal forces of RC members at storey 1 and slightly effects on the internal forces of RC members at storey 2. For short-length RC structures, the effect of temperature load can be ignored in the design of RC elements, whereas it must be taken into account in design of slab, beams and some column positions at storey 1 of medium-length and long RC structures without expansion joints. For the present RC frame building models, the required slab reinforcement in long direction increases about 33.4% for medium-length RC structures (135 m) and about 48.2% for long RC structures (270 m) without expansion joints. The required reinforcement for positive moment at mid-span increases from 33.7 to 39.4%, whereas the total required reinforcement for negative moment at the supports of beams increases from 19.4 to 34.9% in long direction of 270 m long RC structures without expansion joints due to uniform temperature load. Column design of long RC structures without expansion joints under uniform temperature load must be concerned, especially for columns in the corners.

Effect of temperature loading on the performance of a PC bridge in Oklahoma: Reliability analysis

Spatial and temporal temperature variations in bridge structures due to changes in the surrounding climate produce movements which, if restrained, may induce stresses in the structure. Temperature effects have always been considered to be one of the critical issues that affect the performance of prestressed concrete (PC) bridges. In order to (1) develop an efficient temperature loading model for predicting bridge temperature-induced response; and (2) develop guidelines to incorporate the effects of temperature actions in reliability-based condition evaluation, numerical and analytical studies were conducted on a PC girder bridge in Oklahoma, USA. This paper focuses on the structural reliability analysis on the temperature loading action in accordance with AASHTO LRFD specification. A three-dimensional (3D) finite element method (FEM) model was established to estimate the movement and stress under temperature loading, and compared with monitoring counterparts. Then, the validated model was utilized for probabilistic analyses to assess the temperature load effects. Based on the probabilistic temperature loading model proposed in the first paper, loads and resistances statistics from published literature, reliability analyses of AASHTO LRFD limit states were performed by Monte Carlo simulation (MCS) and Rackwitz-Fiessler procedure to determine the safety level in terms of reliability index.

Analytical Solution of the Problem of Symmetric Thermally Stressed State of Thick Plates Based on the 3D Elasticity Theory

An important place among thermoelasticity problems is occupied by the plane elasticity problem obtained from the general three-dimensional problem after using plane stress state hypotheses for thin plates. In the two-dimensional formulation, this problem has become widespread in the study of the effect of temperature loads on the stress state of thin thermosensitive plates. The article proposes a general three-dimensional solution of the static problem of thermoelasticity in a form convenient for practical application. To construct it, a particular solution of the inhomogeneous equation, the thermoelastic displacement potential, was added by us to the general solution of Lamé's equations, the latter solution having been previously found by us in terms of three harmonic functions. It is shown that the use of the proposed solution allows one to satisfy the relation between the static three-dimensional theory of thermoelasticity and boundary conditions, and also to construct a closed system of partial differential equations for the introduced two-dimensional functions without using hypotheses about the plane stress state of a plate. The thermoelastic stress state of a thick or thin plate is divided into two parts. The first part takes into account the thermal effects caused by external heating and internal heat sources, while the second one is determined by a symmetrical force load. The thermoelastic stresses are expressed in terms of deformations and known temperature. A three-dimensional thermoelastic stress-strain state representation is used and the zero boundary conditions on the outer flat surfaces of the plate are precisely satisfied. This allows us to show that the introduced two-dimensional functions will be harmonic. After integrating along the thickness of the plate along the normal to the median surface, normal and shear efforts are expressed in terms of three unknown two-dimensional functions. The three-dimensional stress state of a symmetrically loaded thermosensitive plate was simplified to the two-dimensional state. For this purpose, we used only the hypothesis that the normal stresses perpendicular to the median surface are insignificant in comparison with the longitudinal and transverse ones. Displacements and stresses in the plate are expressed in terms of two two-dimensional harmonic functions and a particular solution, which is determined by a given temperature on the surfaces of the plate. The introduced harmonic functions are determined from the boundary conditions on the side surface of the thick plate. The proposed technique allows the solution of three-dimensional boundary value problems for thick thermosensitive plates to be reduced to a two-dimensional case.

Real-time damage evaluation method for multiaxial thermo-mechanical fatigue under variable amplitude loading

A real-time multiaxial thermo-mechanical damage evaluation method was proposed under variable amplitude loading. In order to achieve real-time damage evaluation, a real-time multiaxial cycle counting method that can take into account temperature loading history was proposed. The proposed multiaxial cycle counting method can obtain the reversals one by one in order with the reading of the load-time history data, which can realize the damage calculation immediately as a single reversal is counted out. At the same time, to consider the effect of temperature loading on the damage accumulation, an equivalent temperature was determined for the time period of the counted reversal. A fatigue-oxidation-creep damage model that can consider the influence of the non-proportional additional hardening on the fatigue, oxidation and creep damages was used to predict the lives in cases of isothermal axial-torsional fatigue, uniaxial thermo-mechanical fatigue and axial-torsional thermo-mechanical fatigue under constant and variable amplitude loadings. The results showed that the prediction errors were within a factor of 2.

Study on high temperature sealing behavior of packer rubber tube based on thermal aging experiments

With the exploration and development of high temperature oil and gas wells, high temperature working conditions have gradually become the new normal state of drilling and completion engineering. Due to the high temperature, the failure of the packer rubber seal and the crushing seriously affect the normal development of oil and gas fields. This paper, aiming at the seal failure of rubber tude at high temperature, the parameters of the constitutive model of rubber tude were studied through the rubber thermal aging experiments. And the finite element calculation model of the packer under the sitting condition was established. The effect of temperature load on the sealing performance and strength behavior of packer rubber was studied. The effect of key parameters of the rubber tube-casing gap δ, the dip angle α of the adjacent rubber tube contact surface and the initial setting load on the sealing performance of the packer under high temperature conditions were analyzed. The findings show that the Yeoh model is more suitable to describe the high temperature material constitutive structure of the packer tube; At high temperature, the larger the gap δ is, the worse the packer sealing performance is; While 12–24° for angle α, sealing performance is better; The suggested initial setting limit load for packer rubber tube safety seal is 68–76 kN. The research work in this paper is of great significance to the design of packer rubber tube structure and its adaptability to high temperature conditions.

Torque control based direct teaching for industrial robot considering temperature-load effects on joint friction

Purpose The purpose of this paper is to design a practical direct teaching method for the industrial robot with large friction resistance and gravity torque but without expensive force/torque sensor, where the gravity torque is just a function of joints position, whereas the friction is closely associated with joint velocity, temperature and load. Design/methodology/approach In the teaching method, the output torque of joint motor is controlled through current to compensate gravity torque completely and friction resistance incompletely. Three variables closely associated with friction are investigated separately by experiment and theoretical analysis, and then a comprehensive friction model which is used to calculate the required compensated friction torque is proposed. Finally, a SIASUN 7 degrees of freedom robot was used to verify the model and the method. Findings Experimental results demonstrated that the teaching method enables an operator to teach the robot in joint space by applying small force and torque on either end-effector or its body. The friction investigation suggests that the velocity and temperature have a strong nonlinear influence on viscous friction, whereas load torque significantly influences the Coulomb friction linearly and causes a slight Stribeck effect. Originality/value The main contribution includes the following: a practical joint space direct teaching method for a common industrial robot is developed, and a friction model capturing velocity, temperature and load for robot joints equipped with commercialized motors and harmonic drives is proposed.

Research of the stress-strain state of cylindrical elements of engineering constructions of special purpose under the effect of temperature load

Active development of monolithic-frame construction in the recent period of time requires a new approach to the calculation of elements of building structures. Concrete columns are one of the most important elements of such buildings, the failure of which is of great durability. Loss of strength characteristics of the column may occur as a result of the loads caused by the effect of temperature fields. Therefore, research related to the influence of temperature on the supporting elements of structures of military objects, is relevant and of great importance.The non-stationary temperature field in a cylindrical concrete column, which changes over time under high temperatures, is investigated. When modeling the heating process of a column, the boundary conditions of the third kind are taken into account. Using the Laplace transform, we obtained analytical expressions for the research of a temperature field. The stress-strain state of the column with pinched and free ends is determined, which is caused by a non-stationary temperature field, where various values of the heat transfer coefficient between column and the environment were taken into account.One of the most significant causes of increased danger for such structures is uneven heating and changes in the characteristics of strength and deformability of concrete during and after the fire. At the same time it is necessary to solve the issues connected with ensuring sustainable and reliable operation of building structures, including the influence of high temperatures, due to the adoption of appropriate materials or protective coatings. Thus, mathematical modeling of the processes of temperature fields in a stress-strain state of cylindrical structures can significantly increase accuracy of calculations, which contributes to the strength and reliability of engineering structures. The graphic dependences of radial, ring, and axial stresses from the radius are researched as a result of the temperature fields of different intensity on the rod elements are obtained and we have found radial displacement at different temperature.

Deformation behavior of sandwich hemispherical structure under axial compression at low temperature

Foam core sandwich structure has excellent insulation and specific strength and is widely used in the aerospace, aviation, navigation and military fields. The hemispherical shell of this kind sandwich structure is often used as energy and load carrying component due to its energy absorption ability. Some foam core sandwich hemispherical structures work in particular ultra-low temperature environments which undergo both temperature and mechanical loads. The research on the load carrying capacity of such structures in ultra-low temperature environment is essential for design and verify its properties. In this paper, the low-temperature mechanical properties of the face sheet and core materials were tested. The thermo-mechanical coupling numerical model was established and verified by comparison with the experimental results. Through the numerical simulation, the compressive behavior of the foam core hemispherical shells with different sizes was obtained under three different low-temperature loading situations. The effect of temperature loading on the deformation mode, load carrying capacity and deformation accumulation is further studied. It is suggested that the cooling of the out sheet is a relatively preferred low-temperature loading method. It also provides advice and ideas for the use of such structures.

Thermal Analysis of Concrete from Panels Subjected to Fire Experiments

This paper presents the results of the differential thermal analysis of cement matrix samples taken from concrete panels with nominal dimensions of 2300 × 1300 × 150 mm after one-sided exposure to high temperatures. The panels were subjected to maximum nominal temperature loads of 550, 600, 800 and 1000 °C. Concrete was also taken from a reference panel (without temperature loading) and investigated. Five samples with a nominal thickness of 20 mm were taken for thermal analysis. They were cut from the central part of the panels using a diamond blade saw. The thermal analysis covered the effects of temperature load on the concrete to a depth of approximately 100 mm from the heated surface of the panel.