Standard Fire Curve Research Articles

Behavior of cross-laminated timber panels during and after an ISO-fire: An experimental analysis

Cross-laminated timber has been used in buildings since the 1990s. In the last years, there has been a growing interest in the use of this technology, especially with the adoption of the product in increasingly taller buildings. Considering that the product is manufactured from a combustible material, wood, authorities that regulate the fire safety in buildings and the scientific community have carried out numerous research and fire tests, aiming to elaborate codes which contemplate the use of cross-laminated timber in tall buildings. This paper discusses the main results obtained from the fire resistance test of a cross-laminated timber slab carried out in the horizontal gas furnace (3.0 m × 4.0 m x 1.5 m) from the University of Sao Paulo. A vertical load of 3 kN/m2 was applied over the slab and the specimens were exposed to the standard fire curve for 30 min. In addition to the 30-min test, the research also evaluated the thermal behavior of the samples during the 24 h after the burners were turned off. Throughout the test, the slab maintained the integrity and the thermal insulation, and no falling-off of the charred layer was observed. However, the 24-h test indicated that it is mandatory to consider the loss of stiffness and strength of timber caused by the thermal wave observed during the decay phase.

Impact of external biaxial compressive loading on the fire spalling behavior of normal-strength concrete

Explosive spalling of concrete exposed to fire consists in the expulsion of shards from the heated face during rapid heating. The phenomenon can seriously jeopardize the integrity of reinforced concrete structures due to the reduction of the cross-sectional area of the structural elements and even lead to the direct exposure of reinforcing bars to flames. The literature shows that various parameters influence the occurrence of fire spalling, such as heating rate, specimen geometry and boundary conditions, concrete grade, and external loads. In this regard, the present study aims at highlighting the role of external loading in combination with the effects of pore pressure and thermo-mechanical stresses in triggering spalling in normal-strength concrete (fc28days ≈ 45 MPa). Unreinforced concrete slabs (size: 800 × 800 × 100 mm3) were subjected to a standard (ISO 834–1) fire curve under seven different levels of external membrane biaxial compressive load. The experimental results clearly show that compressive loading significantly increases spalling propensity and severity.

Static Capacity Curves of Reinforced Concrete Structures Exposed to High Temperature Effects

In this study, it is aimed to investigate the seismic performance of a reinforced concrete (RC) structural system exposed to high temperatures. For this purpose, a RC structure with 4 floors and 4 spacings was designed. First of all, column and beam elements were modeled by using ANSYS software and then, thermal analysis was performed assuming that they were exposed to the standard fire curve to obtain the temperature distributions in the cross-sections of the reinforced concrete elements. Secondly, the sectional analyses were performed for the reinforced concrete element sections and moment-curvature relations were obtained. Finally, the three dimensional (3D) structural system was modeled and static pushover analysis was carried out in accordance with the Turkish Building Earthquake Code (TBEC 2018). The results showed that as the exposure time to high temperature increase the inelastic displacement capacity and the base shear force values decrease. The results were also affected by the location of the fire event. Besides, plastic hinges occurred more quickly than the situation before fire event, resulting in a decrease in the load carrying capacity and stiffness of the system.

Temperature field of intumescent coating protected concrete-filled steel tubular columns under fire

In the fire protection design for concrete-filled steel tubular (CFST) structures, the analysis of temperature field usually acts as a preceding step to further study the mechanical performance in fire. However, there is still a lack of systematic research on the temperature field of CFST sections with intumescent fire coating (IFC). In this study, fire tests of four hollow steel tubular specimens and twenty CFST specimens lasted for 180 min ∼240 min were carried out under ISO-834 standard fire curve and all the specimens were protected with IFC. A technical process to determine the equivalent thermal conductivity of IFC applied to CFST columns was proposed. A verified finite element analysis (FEA) model to predict temperature field of IFC protected CFST section was established and the size effects of CFST sections on the temperature field were studied. It was found that the intumescent coating can reliably work together with CFST specimens without overall crumbling during the long-time fire exposure up to 240 min. The temperature rise of the steel tube of CFST column can be significantly delayed with the effective insulation of IFC together with the heat absorption of the core concrete. The main factors affecting temperature rise of the IFC protected CFST section under fire are the core concrete, dry film thickness (DFT) of IFC and sectional diameter.

Intelligent Fire Resistance Testing and Calculation of Precast Modular House by Computer Numerical Simulation

Through the fire resistance tests of fourteen components and one full-scale flat-packed modular house, the fire resistance limits of both steel components under standard fire curve and modular house entirety under real fire were studied. Test results showed that the fire safety could be guaranteed for applying light steel modular houses in low-rise buildings. In addition to structural fire protection design, fire performance simulation should also be combined with the measures of smoke alarm, spray, smoke diffusion simulation, evacuation simulation, fuel control and rescue response to ensure the fire safety. The research results of this paper can provide references for fire protection design of light steel modular houses.

Fire resistance and design assessment of Q355 circular hollow section joints

This paper presents an experimental investigation on fire resistance of circular hollow section (CHS) T-, Y- and K-joints. A total of 15 specimens subjected to brace axial load were heated inside an electric furnace, including 5 T-joints, 5 Y-joints and 5 K-joints. The temperature inside furnace follows ISO 834 standard fire curve. The principal parameters considered in this study include the dimensionless geometric parameters of joints β and γ, as well as the load ratio n. It is found that the failure mode of the axially loaded CHS joints under fire is chord plastification. Referring to the temperature-deformation curves of these CHS joints, it is suggested to adopt 1.5% ovalisation of the chord diameter as the failure criteria of the CHS joints under fire. The fire resistance of the CHS joints is seriously reduced with an increase in the load ratio n. By comparing the temperature development and the critical temperatures of the CHS joints obtained in the tests with the ones predicted by design codes, it is found that the measured temperature development curves of the CHS joints are significantly different from the calculated ones before the joint temperature reaches 550 °C. Further investigation is essential for temperature development analysis of CHS joints, especially in the aspects of the section factor Am/V of CHS joint. The fire resistance performance of CHS T- and Y-joints is shown to be reasonably estimated with the resistance method provided in modern design codes, even though the estimation on CHS K-joints is relatively conservative.

Investigation on engineering properties and micro-structure characteristics of low strength and high strength geopolymer composites subjected to standard temperature exposure

Fire accidents are common and one among the serious hazards faced by civil infrastructures; therefore, appropriate measures have to be taken while designing the buildings and structures to ensure the safety of the residents. Reducing the damage caused by fire and the collapse of structural elements are the primary significance in designing concrete structures. An experimental study was conducted to examine the mechanical properties of temperature exposed concrete specimens following ISO 834 standard fire curve. Present investigation examines the performance of Geopolymer concrete (GPC) after exposed to temperature exposure. Two types of concrete namely, low and high strength GPC were cured under two curing regimes viz, room temperature curing and oven curing was adopted in this study. The GPC specimens were heated to 821 °C, 925 °C, 986 °C and 1029 °C, following the rate of heating was in accordance with ISO 834. Influence of elevated temperature on GPC specimens were examined by visual inspection, weight loss, strength loss and micro-level studies including Scanning Electron Microscope (SEM). Results from the study reveals that, the strength of high strength concrete was more prone to temperature exposure. Room temperature cured GPC specimens possessed higher residual strength than oven cured specimens for all the heating durations (marginal variation less than 5%). Crushing Index (CI) of 8.1% was regarded as optimal value for coarse aggregates (CA) to sustain its strength at a temperature of 821 °C. The phase change and dehydration of geopolymeric gel were observed in SEM analysis, and strength loss of CA are considered as the influencing parameters for degradation of concrete at higher temperature exposure. High strength concrete is more prone to strength loss than low strength concretes.

An Experimental Study on the Evaluation of the Radiant Heat Effect of Plant Fire Walls During Fires

Owing to infrastructure obsolescence, petrochemical plants possess a high risk of accidents. Various restrictions and regulations exist on the structural arrangement and separation distance to reduce the risk of damage from such accidents and to encourage the use of fire walls in building structures. Currently, steel fire walls require revision because their material properties induce the production of radiant heat during a large fire, which can cause casualties. In this study, steel fire walls from an actual petrochemical plant were heated to follow a “KS F 2257-1” standard fire curve. Consequently, the possibility of fire and human damage due to heat flux and temperature changes were evaluated.

Flexural Behavior of Reinforced Concrete Beams with FRP Bars Exposed to Elevated Temperature

The present study aims to evaluate the performance of concrete beams with different Fiber Reinforced Polymer (FRP) and steel bars exposed to elevated temperatures through a detailed experimental investigation. Flexural behavior of beams is analyzed with Carbon Fiber Reinforced Polymer bars (CFRP), Basalt Fiber Reinforced Polymer bars (BFRP), Glass Fiber Reinforced Polymer bars (GFRP), and steel bars tests. Beams were exposed to elevated temperature 925 °C (1 hr) following standard fire curve, and subsequently cooled by either natural or forced water spraying. After the cooling, beam specimens were tested under four-point loading up to the failure load. Ultimate load and deflection profile of heated and unheated beams are evaluated. At higher temperatures (925 °C), the steel and GFRP specimens show a higher strength loss of about 60–80% with higher deformation values. The load carrying capacity of CFRP beams is found to be higher as compared to other types of beams. Specimens cooled by water shows higher strength loss of about 7–12% than air cooled specimens. The failure pattern of beams with FRP and steel beams are different, and it is based on heating cooling regime.

Bushfire-Resistant Lightweight Masonry Blocks with Expanded Perlite Aggregate

During bushfires, one of the building elements that is directly exposed to embers, radiant heat and direct flames is the “wall” element. This study investigated the feasibility of using expanded perlite aggregate in masonry (i.e., cement) blocks to enhance their bushfire resistant characteristics. The chemical, physical, and thermal properties of expanded perlite aggregate were determined first and then masonry block cement mixes were developed by replacing sand in the conventional mix with expanded perlite aggregate by volume at different percentages (100, 80, 60, and 40%). The properties of fresh and hardened cement mixes (slump, density, compressive strength, and water absorption) were measured. The developed masonry blocks were exposed to Bushfire Flame Zone conditions (i.e., 20–842 °C) and the standard fire curve for three hours (i.e., 20–1110 °C) to assess their resistance to bushfires and building fires, respectively. The properties of Cement–Expanded Perlite mixes were compared with those of the standard Cement–Sand mix. The test results showed that the use of perlite aggregate reduced the workability, density, and compressive strength of the cement mix while increasing the water absorption and fire resistance level. All the developed perlite blocks were lightweight and had three hours of fire resistance level (-/180/180). When exposed to bushfire flame zone conditions, the blocks made with 100, 80, and 60% perlite satisfied the maximum ambient surface temperature limit. Of these, masonry blocks made with 60% perlite aggregate are the most suitable for use in external walls of bushfire shelters and residential and commercial buildings in bushfire-prone areas.

Proposal of Standard Wildfire Curves for the Design Protection of Dwellings against Wildland Fire

This paper presents research that proposes a new standard fire curve to simulate exterior wildfire due to burning trees and bushes. An extensive inquiry was performed in the existing scientific literature, in the search of measured temperature versus time wildfire curves by other authors, in trees and bushes using in situ thermocouples. The gathered wildfire curves for both trees and bushes are plotted together, and envelope upper-bond wildfire design curves are proposed. The objective of these new proposed fire curves is for them to be used in the design of the protection of dwellings located in the urban wildland interface against the action of a natural wildfire. To access the efficiency of these proposed fire curves, a thermal numerical analysis is performed using the commercial finite-element software Abaqus, in which a wood specimen is subjected to real wildfire and compared with the proposed wildfire design temperature versus time curves.

Cyclic behaviour of as-built and strengthened existing reinforced concrete columns previously damaged by fire

A structure, during its life, may be subjected to multiple hazards. These hazards are sometimes combined over a short period of time, or in some cases occur many years apart, with the first hazard influencing the structural response under a second hazard. A reinforced concrete (RC) structure previously damaged by fire and then exposed to seismic loading is one such example. To assess such structures, the effects of fire on the cyclic performance of RC elements needs to be better understood. Moreover, it is also important to develop and validate strengthening methods that can reinstate or improve the seismic performance of fire-damaged RC elements. This paper presents the results of a novel experimental campaign where six full-scale RC columns with detailing representing existing Mediterranean buildings designed to old seismic codes are subjected to fire and then cyclic loading. Four RC columns were damaged after exposure to 30 or 90 min of the ISO 834 standard fire curve in a furnace and then tested under uniaxial cyclic lateral loading up to failure. Two of these columns were repaired and strengthened post-fire with Carbon Fibre Reinforced Polymer (CFRP) wrapping. The strengthening method aimed to increase the concrete strength through confinement, and to increase the displacement ductility and energy dissipation capacity under seismic loading. Two additional control columns, one as-built and another strengthened, were cyclically tested for comparison with the fire-damaged columns. It was found that the 30 min fire exposure resulted in few concrete cracks, whilst cover spalling and general cracking was observed in the 90 min fire exposure. A significant decrease in the displacement ductility and dissipated energy of the columns was observed following fire exposure, even for the 30 min fire. The columns that had post-fire repair and CFRP strengthening, showed better cyclic performance than the control column without fire exposure. It was also found that post-fire strengthened columns may reach similar seismic performance than similarly strengthened columns without previous fire damage.

Comparison of Various Codes of Fire on Structural Design

Abstract: Fire situation is the significant issue in India and that of different designs is severely impacted by them. A portion of the design might fall after the fire in view of temperature impact. In this research, the primary spotlight on the beam and column of the structure. The standard fire curve is presented in IS code for a substantial steel support however for concrete neither fire curve is created nor any issue proclamation is given with the goal that various codes are utilized for the issue explanation. In this venture IS code, Euro Code, National Building codes of Canada and National code of Construction series of Australia are utilized. In reference of this codes the model to be framed in SAP programming with various information. The temperature for investigation is taken same for the whole model. The failed structures are over and over examined and make the model safe. Then the segment cross-segment and shaft cross-segment are taken and post process for the warm examination in SAFIR Software. This product is an issue sort of GID Software. In this the model are broke down by warm impact and post process in DIAMOND Software for the outcome. The similar examination of the Single bay frame model and 3-bay frame model for various codes is shown with assistance of chart. The correlation is in the middle of between standard fire curve and various codes. Keywords: Fire, SAFIR, DIAMOND, SAP-2000, Various Codes.

Spalling behaviour of concrete made with recycled concrete aggregates

Concrete made with recycled concrete aggregates (RCA) presents particular properties that may lead to a specific behaviour under fire conditions, including the spalling risk. The spalling sensitivity of concrete made with RCA was evaluated through a campaign conducted in three concrete series: reference, direct replacement, and strength-based replacement. The last was designed to have the same performance as concrete made with natural aggregates (NA). Samples with different replacement rates of recycled coarse aggregates (0%, 10%, 20%, 40%, and 100%) were exposed to the standard fire curve (ISO 834-1) with constant uniaxial loading (2.5 and 5MPa). During the tests, the furnace temperature and spalling events were recorded. After the tests, digital photogrammetry was used to observe the spalling damage (volume and depth). Fire tests indicated that concrete made with RCA exhibited a higher spalling degree than concrete made with NA. Results also show that the replacement rate acts in different ways: in concrete with RCA replacement rates up to 40%, the spalling damage increases, but a further increase does not lead to higher spalling. In addition, RCA changes the physical properties of concrete, which may trigger spalling, particularly water content.

Performance of clay masonry prisms with light weight plaster exposed to standard fire exposure

AbstractClay bricks are one of the most widely used materials in building construction due to their advantages, including local availability, ease of fabrication and cost‐effectiveness. Fire is one of the dangerous hazards that can cause damage the life and property. Lightweight plasters play a vital role in insulating the masonry construction during fire accident. There is only limited data and information available on the fire performance of Clay Brick Masonry (CBM) insulated with lightweight plaster. An extensive investigation was undertaken to evaluate the residual strength properties and physical characteristics of CBM prisms exposed to elevated temperatures. CBM prisms plastered with M‐sand mortar, vermiculite mortar, and perlite mortar were used for the investigation. Protected prisms were exposed to elevated temperatures following the ISO 834 standard fire curve for durations of 30 min (821°C), 60 min (925°C), 90 min (986°C), and 120 min (1029°C). Mechanical properties such as axial load carrying capacity, stress–strain behaviour, elastic modulus, and crack pattern were examined. The mechanical properties of CBM prisms were found to be highly influenced by the type of plastering, intensity, and the duration of heating. The microstructure and image analysis confirmed the effects of temperature exposure on protective plasters. Equations are proposed to determine the residual axial compressive strength and the elastic modulus of CBM. It was found that the specimens plastered with perlite mortar had better fire resistance.

Effect of protective coating on axial resistance and residual capacity of self-compacting concrete columns exposed to standard fire

Self-Compacting Concrete (SCC) is a green construction material widely used in the construction industry. While normal weight concrete has notable performance under fire conditions, the open literature continues to lack works examining the structural fire performance of SCC elements. Intending to bridge this knowledge gap, the present study aims to understand the efficiency of different protective coatings on fire response and the residual capacity of SCC short columns. In this experimental investigation, SCC columns were primarily cast from Supplementary Cementitious Materials (SCM) such as Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) with partial replacement of fine aggregate by utilising the optimum content of Expanded Perlite Aggregate (EPA). Then, a thermal protective coating comprising of Cement Perlite Plaster (CPP) was developed using Ordinary Portland Cement (OPC) and the EPA. The fire performance of SCC elements was examined when protected with the newly developed coating as well as Gypsum Plaster (GP), Basalt Wrapping (BW), and Carbon Wrapping (CW) when exposed to ISO 834 standard fire curve for 60, 90, 120, and 180 min. The experimental results revealed that SCC specimens developed using GGBFS had better resistance to all exposure durations than the FA-SCC specimens. Also, it was noted that the CPP-protected SCC specimens exhibited higher residual strength capacity, followed by GP-protected SCC specimens, compared to the BW and CW-SCC specimens under axial load.

Numerical analysis and structural fire design of protected SHS steel columns with thermally enhanced gypsum-based mortars

Fire protection materials should restrict the temperature increase in steel members to prevent premature steel damage and structural failure in case of fire. The design of fire protection materials must be then precise, efficient, and optimized to make steel structures more competitive in the construction sector, thus reducing the impact of one of the worst disadvantages of steel structures. Therefore, this paper presents a numerical investigation into the performance of gypsum-based mortars enhanced with silica micro and nanoparticles as passive fire protection materials to protect the steel columns against fire. Square hollow section (SHS) steel columns were considered for this investigation. Firstly, finite element models were developed and confronted with observations from experimental tests previously carried out by the authors. Secondly, a parametric study was undertaken to study the role of several parameters on the structural fire performance of such columns when exposed to the ISO 834 standard fire curve, including the fire protection thickness and type (composition), column slenderness and load level. Then numerical and analytical results from current design rules in Eurocodes were compared. And finally, changes to the steel temperature prediction method in current design standards were proposed based on the findings of this study. It was observed that the design predictions excessively underestimated the actual fire resistance of the protected SHS steel tubular columns, especially when fire protection mortars with silica micro and nanoparticles were used. The thermal properties of fire protection mortars as a function of temperature must be considered in the structural steel temperature prediction when subjected to fire conditions. It is then strongly recommended that a new revision should be done in the next generation of Eurocodes on this topic based on the proposed modifications or the presented findings.

Influence of Industrial Metakaolin Waste on Autoclaved Fiber Cement Properties Changes in Standard Fire Environment.

An investigation was conducted on the influence that industrial metakaolin waste (IMW) has on the properties of autoclaved fiber cement composition (FCC) samples. FCC samples were made from fiber cement plate’s typical components using the same proportions. In samples, IMW was used instead of cement in 10%, 20%, 30% proportions and in 50%, 100% proportions instead of ground quartz. Differential thermal analysis (DTG), thermogravimetric analysis (TGA), ultrasound pulse velocity (UPV), density, porosity and optical microscope (OM) research methods were used to identify the micro and macrostructure of samples. Mechanical properties were evaluated using flexural and compressive strength research methods. It was established that IMW was used instead of cement in fiber cement composition samples up to 10% and in fiber cement composition samples instead of ground quartz forms density microstructure structure because of Al-rich tobermorite. As a result, the flexural and compressive strength increased. Samples with higher content of IMW instead of cement had unreacted IMW and a less dense microstructure. In this case, flexural and compressive strength decreased. All FCC samples were fired in a standard fire curve (ISO 842) for 30 min. Samples of mechanical properties were established by doing flexural and compressive strength tests, and which results showed the same trends.

Investigation on improving the residual mechanical properties of reinforcement steel and bond strength of concrete exposed to elevated temperature

Concrete and reinforcement steel are essential building materials widely used in composite construction due to their advantages, such as strength, durability and ease of availability. Fire is one of the critical hazards that causes severe damage to the structure and leads to progressive collapse. Due to the intensity of fire exposure, the concrete and reinforcing steel significantly losses their inherent mechanical properties and service life. Minimizing the fire-induced damage and failure are the primary objectives in the design of concrete structures. Therefore, an extensive experimental attempt was undertaken to evaluate the pull out behaviour and also to improve the bond performance of concrete and reinforcement steel when exposed to elevated temperature. A cement based perlite coating was developed as a protective material to safeguard the concrete in the study. All the pull out bond test specimens were heated following the ISO 834 standard fire curve, and subsequently cooled either by air or water. Residual mechanical properties of steel rebar such as yield strength, ultimate strength, elastic modulus, shear and bending capacity were evaluated after the exposure to elevated temperature. Investigations were conducted on pull out specimens to evaluate the bond stress slip behaviour and bond strength of concrete. A detailed physical observation was made on the failed concrete specimens to examine the damage. A drastic reduction in bond strength of concrete and tensile strength of the rebar were observed while increasing the duration of heating. Also, it was observed that the coated specimens exhibited better performance by retaining the bond strength and yield strength of the rebar.

Study on fire performance of T-shaped concrete-filled steel tubular stubs under axial compression

Six T-shaped concrete-filled steel tubular (TCFST) stubs under axial compression loading were designed and tested under the ISO-834 standard fire curve. The temperature field distribution, axial deformation development, fire resistance and failure mode of TCFST columns under fire were investigated. The fire test results showed that the fire resistance decreases with the increase of axial compression ratio; the fire resistance of the tension bar stiffener column is 18% higher than that of the multi-cell column (the fire resistance values are 89 min and 73 min respectively); the fire resistance of specimens increases linearly with the thickness of the fire protection layer. Then the fire behavior of TCFST columns is analyzed by the ABAQUS software. The simulated temperature distribution and fire resistance are in good agreement with the test results. Meanwhile, the fire resistance is slightly higher than that of the square CFST column in the standard ‘Technical Code for Concrete Filled Steel Tubular Structures (GB50936-2014)’. Furthermore, a parametric analysis results show that slenderness ratio, column limb thickness, eccentricity ratio and fire protection layer thickness have influences on the fire resistance. It is found that the first level fire-resistance rating of TCFST columns can be achieved by adopting a reasonable thickness of the fire protection layer. At last, simplified formulas of the fire resistance and the fire protection layer are proposed, and the simplified formula can reduce up to 50% of the thickness of the fire protection layer compared to current fire design requirements for CFST columns.