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The experimental study presented in this paper aimed to investigate the effects of bolt number and their pattern on the failure time of minimally fire-protected glulam beam bolted connections. Four full-size glulam beam-end connection configurations reinforced perpendicular to wood grain with self-tapping screws (STS) were experimentally tested under exposure to elevated temperatures that followed the CAN/ULC S101 (Standard methods of fire endurance tests of building construction and materials. Underwriters Laboratories of Canada, Fifth edition, Ottawa, Canada, 2019) standard fire time–temperature curve. All metal connecting components (i.e., bolt heads and nuts and steel plate edges) were fire protected using wood plugs and strips, respectively. Throughout the duration of fire tests, all specimens were subjected to monotonic load causing bending moment equivalent to the maximum moment design capacity of the weakest unreinforced connection configuration. Fire test results show that the failure time of all four proposed wood–steel–wood connection configurations surpassed the 45-min mark, which is the minimum prescribed fire resistance rating for timber connections in applicable codes, with the two configurations that employed six bolts sustained the applied load for more than 60 min in standard fire conditions. Increasing the number of bolts from four to six enhanced the failure time of the proposed connection configurations with time increments more than those due to changing the bolt pattern. Most importantly, test results confirm that reinforcing the connections with STS fully curtailed wood splitting and averted row shear failure that is frequently encountered in similar but unreinforced connection configurations. [ABSTRACT FROM AUTHOR]

The consequences of destructive earthquakes show that the problem of analyzing the response of reinforced concrete frames under seismic loads after a fire is relevant. The calculation models used for individual elements and buildings as a whole must take into account the nonlinear properties of concrete and reinforcement. In the spectral calculation method, the nonlinear properties of materials are taken into account by introducing a reduction coefficient to the elastic spectrum. When determining the reduction coefficient, a common deformation criterion is based on the use of the plasticity coefficient. The seismic resistance of a three-span, five-story reinforced concrete frame under four different fire exposure options is considered. The residual strength and stiffness of frame elements after a fire is assessed by performing a thermal engineering calculation in the SOLIDWORKS software for a standard fire. For the central sections of the elements, the highest temperatures were obtained after heating—during the cooling stage. The reduction coefficient is estimated by performing a nonlinear static analysis of reinforced concrete frames in OpenSees and constructing load-bearing capacity curves. Fracture patterns and damage levels in plastic hinges are analyzed. Based on the numerical modeling of reinforced concrete frames after exposure to fire, it was revealed that the most dangerous scenario is the occurrence of a fire on the first floor of the building. Based on the obtained plasticity coefficients, reduction coefficients were determined in the range of 2.62 to 2.44. The influence of fire on the permissible damage coefficient of a reinforced concrete frame is assessed using the coefficient φK—the coefficient of additional damage after a fire, which is equal to the ratio of the reduction coefficients for the control and fire-damaged frames. Depending on the percentage of damaged structures on the first floor, the following values were obtained: 50% or less—φK = 1.09; 100%—φK = 1.17. The obtained coefficients are recommended to be used when assessing the seismic resistance of a reinforced concrete frame after a local fire. [ABSTRACT FROM AUTHOR]

Objective. Study of the dependence of the compressive strength on the average density and the flexural strength on the compressive strength of vermiculite concrete composite. Determination of the expression for the coefficients of thermal conductivity and heat capacity of the resulting vermiculite concrete composites in the developed software for thermal engineering calculation of the fire resistance limit of reinforced cement structures with a fire retardant layer of vermiculite concrete.Method. Methods for reducing the consumption of cement binder in the developed fire-resistant concrete composites are considered. Experimental and theoretical methods for determining the fire-retardant properties of the developed vermiculite-concrete composites and expressions for determining their strength properties are proposed.Result. The dependences of the ultimate compressive strength on the average density and the ultimate bending strength on the ultimate compressive strength of vermiculite concrete for the concretes under study, the dependence of the coefficients of thermal conductivity and heat capacity during a fire on the type and average density of vermiculite concrete composites were obtained.Conclusion. Fiber-vermiculite-concrete composites with an average density of 470-560 kg/m3 have the best fire-retardant properties. Software has been developed for thermotechnical calculation using a numerical method of the fire resistance limit of two-layer reinforced-cement structures in a fire, ensuring at least 95% agreement with the experimental data of fire tests of two-layer reinforced-cement elements.

The consequences of destructive earthquakes show that the problem of analyzing the response of reinforced concrete frames under seismic loads after a fire is relevant. The calculation models used for individual elements and buildings as a whole must take into account the nonlinear properties of concrete and reinforcement. In the spectral calculation method, the nonlinear properties of materials are taken into account by introducing a reduction coefficient to the elastic spectrum. When determining the reduction coefficient, a common deformation criterion is based on the use of the plasticity coefficient. The seismic resistance of a three-span, five-story reinforced concrete frame under four different fire exposure options is considered. The residual strength and stiffness of frame elements after a fire is assessed by performing a thermal engineering calculation in the SOLIDWORKS software for a standard fire. For the central sections of the elements, the highest temperatures were obtained after heating—during the cooling stage. The reduction coefficient is estimated by performing a nonlinear static analysis of reinforced concrete frames in OpenSees and constructing load-bearing capacity curves. Fracture patterns and damage levels in plastic hinges are analyzed. Based on the numerical modeling of reinforced concrete frames after exposure to fire, it was revealed that the most dangerous scenario is the occurrence of a fire on the first floor of the building. Based on the obtained plasticity coefficients, reduction coefficients were determined in the range of 2.62 to 2.44. The influence of fire on the permissible damage coefficient of a reinforced concrete frame is assessed using the coefficient φK—the coefficient of additional damage after a fire, which is equal to the ratio of the reduction coefficients for the control and fire-damaged frames. Depending on the percentage of damaged structures on the first floor, the following values were obtained: 50% or less—φK = 1.09; 100%—φK = 1.17. The obtained coefficients are recommended to be used when assessing the seismic resistance of a reinforced concrete frame after a local fire.

In order to know the advantages of using environmentally friendly materials in construction, namely, aggregates from tire recycling, this study aims to develop a numerical and mathematical model in order to analyze the thermal behavior of concrete on the basis of rubber aggregates as a function of time. The main goal of this paper is to look at how the heat shock temperature of 800 °C and the conditions of exposure to the ISO 834 standard fire affect the thermal behavior of concrete with different amounts of rubber (0%, 10%, 20%, and 30%) and constant humidity (3%). The results obtained show that for all mixtures, the temperature propagated in the sample decreases at different rates depending on the content of rubber aggregates. This reduction is mainly due to the decrease in the ability of the material to transfer heat and the increase in the thermal capacity that must be given to the material to increase its temperature. Statistics, frequency distributions, contours, and 3D views have all shown that the numerical model developed works. This makes the model an important tool and a good way to describe how concretes behave when heated. [ABSTRACT FROM AUTHOR]

Objective. Development of compositions of vermiculite concrete and fibro vermiculite concrete with volcanic pumice. Investigation of the construction and technical properties of the developed compositions of vermiculite concrete and fibrovermiculite concrete with volcanic pumice under the influence of elevated temperatures.Method. Methods of increasing the fire resistance of reinforced concrete structures are considered. The research is aimed at the development of vermiculite concrete and fibro vermiculite concrete with volcanic pumice for fire protection of building structures and the manufacture of heat-resistant products and structures. To reduce the cost of vermiculite concrete, its partial replacement with volcanic pumice is proposed. For the study of vermiculite concrete with volcanic pumice reinforced with basalt fiber, a rotatable plan of the second order of the regular hexagon type was used.Result. Replacing a part of an expensive aggregate (expanded vermiculite) with pumice leads to a slight increase in the average density of the composite, while the bending and compressive strength increases. In addition, the heat-resistant properties of vermiculite concrete with pumice are increased. This is due to the fact that volcanic pumice, being a hydraulically active additive, is able to react hydration with cement components, eliminating the harmful effect of secondary hydration of free calcium oxide. The influence of the heating temperature on the change in the construction and technical properties of vermiculite concrete and fibrovermiculic concrete, including with the addition of pumice, has been studied. It was found that dispersed reinforcement with basalt fibers reduces shrinkage deformations, when heated to t = 800, the shrinkage decreases from 0.7 to 0.5% compared to the original concrete matrix.Conclusion. The dependence "compressive strength = f (average concrete density)" significantly depends on the presence and ratio of pumice in the composition of vermiculite concrete, while an increase in the holding temperature to 600 oC or 800 oC leads to a decrease in the compressive strength from 15 to 25%, and the main decrease occurs when heated to 600 oC, further the increase in temperature has a negligible effect. The dependence of the bending strength on the compressive strength is generally maintained regardless of the heating temperature, and the heating of concrete does not reduce the relative bending strength, i.e. the ratio of bending strength / compressive strength is not reduced. Dispersed fiber reinforcement increases the relative bending strength by about 70% regardless of the heating temperature.

Objective. Development of compositions of fire-retardant vermiculite-concrete composites for reinforced cement structures. Investigation of the properties of fire-retardant vermiculite-concrete composite and fine-grained concrete for two-layer reinforced cement structures.Method. Methods for increasing the fire resistance of reinforced concrete structures are considered. Research is focused on the development of fire-retardant composites using expanded vermiculite and volcanic ash. To improve the physical and mechanical properties of the fire-retardant composite, a mixture of Portland cement, gypsum, lime, basalt fiber, saponified wood resin, volcanic ash and expanded vermiculite has been developed. For the study of vermiculite concretes reinforced with basalt fiber, a second-order rotatable plan of the regular hexagon type was used.Result. Fiber-vermiculite concretes are proposed, which have improved fire-retardant properties compared to known compositions. This is due to the better preservation of the fiber-vermiculite-concrete layer when heated as a result of fiber reinforcement. Also, thanks to the addition of SDO, the fire-retardant properties of the composite increase due to the additional porosity of the fiber-vermiculite-concrete. The parameters of the "stress-strain" diagram of a vermiculite-concrete composite and fine-grained concrete have been obtained.Conclusion. Vermiculite concretes with an average density of 480-560 kg/m3 have the best fire-retardant properties. The developed two-layer reinforced cement structures have high fire resistance.

Objective. Development of a method for calculating the bearing capacity of twolayer reinforced cement shells for force and temperature effects in a fire. These structures consist of a fire-retardant layer made of vermiculite concrete, as well as a carrier layer of fine-grained concrete reinforced with mesh.Method. The solution is carried out in a physically nonlinear formulation using the deformation theory of concrete plasticity by G.A. Geniev. In obtaining the resolving equations, the theory of shallow shells by V.Z. Vlasov is used. The physically nonlinear problem reduces to the sequential solution of elastic problems for a structure whose physicomechanical parameters are functions of the x, y, z coordinates. The solution is carried out by the finite element method in combination with the Newton-Raphson method. The dependence of the characteristics of construction materials on temperature is taken into account. The temperature field is assumed to be a function of only one z coordinate, and the finite difference method is used to determine it.Result. the results of numerical simulation of full-scale experiments in a fire chamber for single-layer and two-layer shells are presented. Some deviations are revealed, caused on the one hand by inaccuracies of the experiment and errors of the theory on the other hand.Conclusion. A significant influence of the boundary conditions on the process of deformation of the structure was found. When the support contour was fixed along x and y, a shell bend up was observed, which was consistent with experimental data, and in the case of a freely sliding support contour, the structural points moved exclusively downward. In general, the agreement between the results and experimental data is quite good, which allows us to use the methodology for calculating real structures.

To obtain an accurate estimation of the residual bearing capacities of concrete T-shaped beams after fire exposure, a calculation method combined the finite element (FE) thermal simulation and analytical equilibrium equation was established on a basis of an experimental study of fire (high-temperature) exposure. The effect of the concrete crack size under fire exposure on the post-fire residual bearing capacity was carefully considered in the calculation method. The influences of the load ratio, reinforcement ratio, height-to-width ratio and concrete cover thickness on the residual bearing capacity of a concrete beam after fire exposure were studied, and then a calculation formula for predicting the residual bearing capacity of a concrete T-shaped beam considering fire cracks was proposed according to these influencing factors. The results show that the height-to-width ratio and the reinforcement ratio have a great influence on the residual bearing capacity of the T-shaped beam after fire exposure; these ratios are positively correlated with the residual bearing capacity. The load ratio of the T-shaped beam also has a great influence on the residual bearing capacity of the beam after fire exposure; this ratio is negatively correlated with the residual bearing capacity. The thickness of the concrete cover has little effect on the residual bearing capacity. Compared with that of the finite element simulation results, the calculation accuracy of the residual bearing capacity formula after fire exposure is satisfactory; thus, this work can provide a reference for the calculation of the residual bearing capacity of concrete T-shaped beams after fire exposure. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the fire resistance of HSC columns under the ISO-834 standard fire curve. Due to its complexity, concrete behavior is mainly evaluated using experimental testing. Because of the limitations of experimental studies, this study uses the finite element method to model concrete behavior under fire conditions. The effects of various parameters such as concrete cover, loading rate, concrete strength, aggregate type, and axial load on the behavior of concrete columns, including temperature and displacements, are investigated. The results showed that concretes with high cover, low preloading, siliceous aggregates, and lower compressive strength exhibit a higher fire resistance than other types.

The steel Modular Building Systems (MBSs) that have been influenced by the Light-gauge Steel Frame (LSF) techniques have become a prominent culture in the industry. However, the detrimental behaviour of steel structural components at high temperatures has elevated the risk of fatal accidents in the event of a fire. Although several research investigations have addressed the fire performance of steel modular wall systems, the behaviour of modular floor systems has not been adequately addressed in the state of the art. Hence, to promote the fire safety and optimum design techniques in the modular construction industry by addressing the aforementioned research gap, this study investigated 48 conventional LSF and MBS floors for their structural and insulation Fire Resistance Levels using Finite Element Modelling (FEM) and Heat Transfer Analyses (HTA) techniques. Initially, full-scale experimental fire tests were modelled using FEM methods, and the validity of the techniques was verified prior to the analyses of parametric floor systems. Furthermore, the structural behaviour of the channel section joists in the elevated temperatures was studied, and hence a correlation was established to determine the critical steel temperature at the structural fire failure with respect to the applied Load Ratio (LR). An additional 12.5 mm thick plasterboard sheathing on single plasterboard sheathed floors resulted a 30 min improvement in structural and insulation FRLs. In addition, the modular floor systems demonstrated enhanced structural and insulation Fire Resistance Levels (FRLs) against the corresponding conventional LSF floor designs due to double LSF skin build-up. The incorporation of rockwool insulation and the increase in the insulation volume implied increased structural and fire performances. However, insulation material in the modular designs was more effective. The fire-rated conventional and modular LSF floor systems are expected to be practised in the construction industry to achieve required fire resistances with optimum material usage. [ABSTRACT FROM AUTHOR]

This paper presents a finite-element-based computational model to evaluate the thermal behaviour of composite slabs with a steel deck submitted to standard fire exposure. This computational model is used to estimate the temperatures in the slab components that contribute to the fire resistance according to the load-bearing criterion defined in the standards. The numerical results are validated with experimental results, and a parametric study of the effect of the thickness of the concrete on the temperatures of the slab components is presented. Composite slabs with normal or lightweight concrete and different steel deck geometries (trapezoidal and re-entrant) were considered in the simulations. In addition, the numerical temperatures are compared with those obtained using the simplified method provided by the standards. The results of the simulations show that the temperatures predicted by the simplified method led, in most cases, to an unsafe design of the composite slab. Based on the numerical results, a new analytical method, alternative to the simplified method, is defined in order to accurately determine the temperatures at the slab components and, thus, the bending resistance of the composite slabs under fire conditions. [ABSTRACT FROM AUTHOR]

To improve the perceived equivalency of fire testing of combustible and non-combustible members we have proposed a simple modification in the fire resistance test procedure by introducing a lower limit of the heat release rate of the furnace. With this approach the combustion of the sample adds to the heat of the furnace, which is in contrary to current approach and does increase the severity of the test. To quantify the consequences, three wall assemblies were tested with pre-defined heat release curves and modified furnace conditions. The assemblies were timber walls built from two layers of Oriented Strain Boards (OSB, 25 mm thick) on a timber frame with an air cavity (100 mm). A reference experiment with a well-insulated wall was performed to determine the furnace's minimum heat release rate (HRR) required to maintain the standard (ISO 834) temperature/time curve. The first wall was tested with a standard fire resistance test, and in the 2nd and 3rd wall experiment, the furnace followed the minimum HRR value determined in a reference experiment. In experiment 2, the furnace ventilation matched the air requirements of the burners, and in experiment 3, the furnace was over ventilated. Peak temperatures measured in experiments 2 and 3 exceeded the standard temperature/time relation by 420°C and 600°C, respectively. The assembly's failure (integrity criterion) was observed after 27 min, 23 min and 14 min of experiments 1, 2 and 3, respectively. The limitations of the approach used related to reproducibility and validity are discussed. [ABSTRACT FROM AUTHOR]

A simplified procedure to predict the residual axial capacity and stiffness of both rectangular and circular reinforced concrete (RC) columns after exposure to a standard fire provides the means to replace the current descriptive methods. The availability of such a procedure during the design phase provides engineers with the flexibility to come up with better designs that ensure safety. In this paper, finite difference heat transfer and sectional analysis models are combined to determine the axial behavior of RC columns with various end-restraint conditions at different standard fire durations. The influence of cooling phase on temperature distribution and residual mechanical properties is considered in the analysis. The ability of the model to predict the axial behavior of the damaged columns is validated in view of related experimental studies and shown to be in very good agreement. A parametric study is then conducted to assess the axial performance of fire-damaged RC columns. A procedure is proposed to determine the residual strength and stiffness of fire-damaged RC columns in typical frame structures. [ABSTRACT FROM AUTHOR]

Summary: Adopting glass fibre‐reinforced polymer (GFRP) rebars as a replacement of conventional steel reinforcement in different infrastructure applications is mainly attributed to its corrosion resistance and considerable lightweight‐to‐high strength ratio. However, the use of FRP rebars in construction is still limited due to the degradation of its mechanical properties at elevated temperatures. The experimental work presented in this paper aimed to investigate the structural fire behaviour of concrete beams reinforced with GFRP bars having lap splices at the beam mid‐span. Four identical 2750‐mm long concrete beams with cross‐sectional dimensions of 300 mm × 350 mm were experimentally examined under four‐point flexure bending. A 60‐mm thick concrete cover was used on the bottom, front and back sides of all beams. Two beams were tested as control specimens in ambient condition, while the other two beams were exposed to standard fire while subjected to a transverse load equivalent to 40% of the beam ultimate design moment. Experimental results show that concrete beams sustained the applied loads for a minimum of 53 minutes in standard fire conditions. Also, both test beams failed due to slippage of the spliced bars when the temperature measured at the top of the middle bar approached its glass transition temperature. [ABSTRACT FROM AUTHOR]

Concrete-filled glass fiber-reinforced polymer (GFRP) tube (CFFT) columns benefit from significant concrete confinement effects that enhance its structural performance compared to conventional internally reinforced concrete members. CFFTs are currently utilized mostly for exterior applications, as the uncertainty of their performance in fire situations has slowed their adaptation in buildings. To address this uncertainty, a series of ambient temperature and fire tests were conducted on CFFT columns with slenderness ratios (KL/r) ranging from 6.9 to 62.4, using GFRP tubes of 113 mm outer diameter and 3.8 mm wall thickness. The strength increase provided by the GFRP tubes as compared to plain concrete columns was reduced from the initial 214% increase at a KL/r of 6.9 to 104% at a KL/r of 62.4. The fire tests revealed that unprotected CFFT columns with KL/r = 57.4 were able to sustain the applied design service loads (44% of ultimate capacity) for up to 108 min in a standard fire. However, it was determined that the unprotected GFRP tubes lost their structural integrity after approximately 10 min of fire exposure, when the temperature on the inside of the tube reached 350°C, thereby only providing thermal protection to the concrete core after the 10-min mark. The unique outcomes of this new study indicate that CFFT columns can be a viable design option in fire situations. [ABSTRACT FROM AUTHOR]

The steel Modular Building Systems (MBSs) that have been influenced by the Light-gauge Steel Frame (LSF) techniques have become a prominent culture in the industry. However, the detrimental behaviour of steel structural components at high temperatures has elevated the risk of fatal accidents in the event of a fire. Although several research investigations have addressed the fire performance of steel modular wall systems, the behaviour of modular floor systems has not been adequately addressed in the state of the art. Hence, to promote the fire safety and optimum design techniques in the modular construction industry by addressing the aforementioned research gap, this study investigated 48 conventional LSF and MBS floors for their structural and insulation Fire Resistance Levels using Finite Element Modelling (FEM) and Heat Transfer Analyses (HTA) techniques. Initially, full-scale experimental fire tests were modelled using FEM methods, and the validity of the techniques was verified prior to the analyses of parametric floor systems. Furthermore, the structural behaviour of the channel section joists in the elevated temperatures was studied, and hence a correlation was established to determine the critical steel temperature at the structural fire failure with respect to the applied Load Ratio (LR). An additional 12.5 mm thick plasterboard sheathing on single plasterboard sheathed floors resulted a 30 min improvement in structural and insulation FRLs. In addition, the modular floor systems demonstrated enhanced structural and insulation Fire Resistance Levels (FRLs) against the corresponding conventional LSF floor designs due to double LSF skin build-up. The incorporation of rockwool insulation and the increase in the insulation volume implied increased structural and fire performances. However, insulation material in the modular designs was more effective. The fire-rated conventional and modular LSF floor systems are expected to be practised in the construction industry to achieve required fire resistances with optimum material usage.

Previous building fires and research has shown that simple (shear) connections develop large axial force and flexural demands during a fire leading to potential failure of the connections and progressive collapse of a building. These findings have motivated decades of international research on the fire behavior of simple (shear) connections. While this research all confirmed that simple connections experience large axial force and flexural demands, it occurred without consistency of testing methodology, testing setup, and reporting of results. Due to this inconsistency, the decades of research have yet to be synthesized into comprehensive code changes for the design of simple connections in fires. This paper will summarize international experimental and numerical research on simple (shear) connections and highlight the inconsistencies between this research in an effort to motivate consistent testing and data reporting for future research developments. [ABSTRACT FROM AUTHOR]

This paper presents a finite-element-based computational model to evaluate the thermal behaviour of composite slabs with a steel deck submitted to standard fire exposure. This computational model is used to estimate the temperatures in the slab components that contribute to the fire resistance according to the load-bearing criterion defined in the standards. The numerical results are validated with experimental results, and a parametric study of the effect of the thickness of the concrete on the temperatures of the slab components is presented. Composite slabs with normal or lightweight concrete and different steel deck geometries (trapezoidal and re-entrant) were considered in the simulations. In addition, the numerical temperatures are compared with those obtained using the simplified method provided by the standards. The results of the simulations show that the temperatures predicted by the simplified method led, in most cases, to an unsafe design of the composite slab. Based on the numerical results, a new analytical method, alternative to the simplified method, is defined in order to accurately determine the temperatures at the slab components and, thus, the bending resistance of the composite slabs under fire conditions.

Suspended ceiling is an effective way to fire protection of horizontal structures with steel beams due to its lightness, reliability and functionality. Three designs of fireproof suspended ceiling with silicate plates on cement binder are considered. A detailed description of the tested structures is given. Experiments were carried out to determine the fire resistance of the samples. The results of fire tests on suspended ceilings under standard fire temperature regime are presented in this study. It was found that the structures that have shown their effectiveness under the standard regime cannot satisfy the conditions of the hydrocarbon temperature regime. For the purpose of efficiency in the hydrocarbon regime and isolating the beams from the fire, in addition to fire-retardant plates, non-combustible heat insulation was used in the construction of the ceiling. The results of testing the ceiling with fire-retardant plates and rock wool when creating a hydrocarbon fire regime are given. It is shown that at the end of the fire exposure, the limiting state of the loss of bearing capacity and the loss of integrity was not fixed, visible changes during the test period was not found.

This paper presents a numerical method for damage evaluation of steel structures under fire conditions based on degraded material property values. As the measure of structural damage to fire, a damage index is proposed which indicates how much a structure loses its material strength when exposed to fire. The index is formulated with the ratio of a volume-weighted average of material strength at elevated temperatures to that of the strength at room temperature. To investigate the feasibility of proposed damage index, fire testing and the corresponding structural fire analysis of steel–concrete composite beams are performed using a design fire load. The fire is modeled using a standard fire curve proposed in American Society for Testing and Materials E119. A regular real-scale composite beam and the beam protected by a fire-resistant material layer, the latter of which is typical of structural members used in nuclear power plant buildings in Korea, are considered for the fire damage evaluation. The damage state of the composite beams is evaluated using the fire damage index at each time the fire progresses, and it is compared with the value of the post-fire damage index of the beams. By the use of the proposed damage index, the effect of fire-resistant materials on structural integrity is quantified, and it is investigated whether the damage state of each beam at the end of the fire load satisfies the design performance of composite beams used for nuclear power plant structures. [ABSTRACT FROM AUTHOR]

Thermal destruction of fire-retardant intumescent coating of the composition of ammonium polyphosphate (APP)/melamine (MA)/pentaerythrite (PE)/titanium oxide (TiO2)/polymer, which can be applied for fire protection of steel structures, was studied. The influence of polymers of different nature - ethylene-vinyl acetate (EVA), vinyl acetate versatate (VAVV), styrene acrylates, and vinyl toluene acrylate on the processes of formation of a coke layer and fire-retardant effectiveness of appropriate coatings was determined. Chemical transformations of polymers EVA and styrene acrylate in the intumescent system of ARR/MA/ PE/TiO2 in the temperature range of 200-800 °C were studied. It was established that the processes of the thermal destruction of vinyl acetate polymer are more harmonized with chemical reactions of the components of the intumescent system than similar processes for acrylate aromatic polymers. Thermal-oxidation destruction of intumescent compositions at the temperatures of 200-800 °C was explored. It was shown that basic chemical processes with polymers of EVA and VAVV begin after 300 °C and flow in the temperature range of 350-600 °C. It was found that the noticeable degradation of the carbon-phosphorus frame of intumescent compositions with styrene acrylate polymers begins at 450 °C, which is almost by 150 °C below the temperature of degradation of the compositions containing vinyl acetate binders. The conducted fire tests demonstrate that intumescent compositions with the use of acrylate aromatic polymers are more effective at the low coating thickness in ensuring the fire resistance boundary of 30 min. In order to ensure higher values of fire resistance, it is necessary to use intumescent coatings containing vinyl acetate co-polymers as the polymer component. The study of the impact of polymers of intumescent coatings on the boundary of fire resistance of steel structures has scientific and practical significance for the development of differentiated fire protection means, oriented to the given class of fire resistance. Fire-retardant intumescent compositions examined in this study can be used as the basis for the formulations of materials for fire protection of building structures under conditions of a standard fire. [ABSTRACT FROM AUTHOR]

Summary: This paper reports the results of an experimental study on two types of intumescent coating exposed to the ISO834 standard fire and three nonstandard fire curves. The nonstandard fires were all less severe than the standard fire. A total of 72 intumescent coating protected steel specimens were tested. The expanded thickness of intumescent char was measured, and the pore feature was observed. Constant thermal conductivity for each specimen was calculated based on the measured steel plate temperature. Thermogravimetric analysis (TGA) test was carried out, and the results show that more gas is trapped within the coating due to better matching of thermal behaviour between gas evolution and polymer viscosity as the rate of heating increases. The constant effective thermal conductivities for the intumescent coating under the nonstandard fires were 65% (type‐W) and 35% (type‐S) higher than that under the standard fire, which resulted in an overestimation of the coating failure time up to 15 and 11 minutes, respectively. Therefore, it is sometimes insecure to use results from standard fire tests guiding the design of coating thickness for steel elements under nonstandard fire conditions. [ABSTRACT FROM AUTHOR]

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Abstract Reactive Powder Concrete-Filled Steel Tube (RPC-FST) is a new composite section with ultra-high strength, good plasticity and ductility to withstand blast loading. This paper is devoted to introduce an analytical method for evaluating the damage level of RPC-FST column suffered fire attack and the following blast load. The damage indexes of RPC-FST column has experienced ISO-834 standard fire and subsequent blast load are predicted using Pressure-Impulse (P-I) diagram. The analytical approaches are proposed based on equivalent Single Degree of Freedom (SDOF) model, in which the damping dissipation, thermal effect and axial load are included. In order to clarify the influences of temperature distribution and explosive charge on the damage index, an inclusive P-I function, characterized by three variables: pressure, impulse and fire duration, is presented. Then blast-resistant results of four fire-damaged RPC-FST columns are employed to validate the reliabilities of presented method. Parametric analysis is conducted to investigate the impacts of damping ratio and ductility ratio on the structural damages. It is demonstrated that a larger damping would lead to better structural blast-resistance. The asymptote value of quasi-static zone tends to smaller as the ductility ratio increases, either the asymptote value of impulse zone, which results in a larger safe area for structural member. In addition, the damaged level is governed by impulse load as scaled distance decreases. The analytical damage indexes are well validated by experimental data. Highlights • Behaviors of post-fire RPC-FST columns under blast loading are depicted by equivalent SDOF model. • Damage levels of fire-damaged RPC-FST columns suffered blast attack are predicted using Pressure-Impulse diagram. • Damage indexes obtained in this paper are verified by experimental data of four large-scale RPC-FST columns. [ABSTRACT FROM AUTHOR]

Fire has a significant influence on concrete structures and members. A concrete column, compared to other structural members, has most often to cope with vertical forces and bending moments from slabs and beams. Therefore, it is important to investigate the fire resistance of concrete columns. In fact, simplified methods are often adopted to evaluate the capacity of concrete columns. In the fib Model Code 2010, a curvature approximation is introduced. However, this method has not been validated to be used in case of fire. Hence, a parametric study is performed in this paper to investigate the application of this method. As a first step of this paper, a curvature approximation formula used at ambient temperature is introduced. As this formula is based on the curvature and in order to verify the application, a numerical tool that can obtain the bending moment and curvature relationships is presented and validated. Further, an ISO 834 standard fire is adopted. Finally, parameters like dimensions, the reinforcement ratio and the slenderness ratio are investigated. Comparing the effect of dimensions, the reinforcement ratio as well as the slenderness ratio, it is concluded that only the slenderness ratio has a significant influence on the column capacity with the proposed formula. The difference between the deflections obtained with the simplified method and the numerical values increase in function of the slenderness ratio (in case of the same axial load). However, this method is proven to be easy-to-use and safe for the prediction of the fire resistance of concrete columns. [ABSTRACT FROM AUTHOR]