Journal of Structural Fire Engineering

Abed, Mohammed Ahmed; Lubloy, Eva

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-09-2021-0056

Fire can severely affect concrete structures and with knowledge of the properties of materials, the damage can be assessed. Aggregate, cement matrix and their interaction are the most important components that affect concrete behaviour at high temperatures. The effect of incorporating recycled concrete aggregate or cementitious materials, namely, cement type and pulverized fly ash, are reviewed to provide a better understanding of their involvement in fire resistance.Design/methodology/approachMore investigation research is needed to understand the fire resistance of such sustainable concrete that was already constructed. The present study illustrates the effect of using recycled concrete aggregate and cementitious materials on the fire resistance of concrete. To do so, a literature review was conducted and relevant data were collected and presented in a simple form. The author's selected research findings, which are related to the presents study, are also presented and discussed.FindingsRecycled concrete aggregate enhances the concrete behaviour at high temperatures when it substitutes the natural aggregate by reasonable substitution (more than 25–30%). It also almost eliminates the possibility of spalling. Moreover, utilizing both supplementary cementitious materials with recycled concrete aggregate can improve the fire resistance of concrete. The incorporation of pulverized fly ash and slag in Portland cement or blended cement can generally keep the mechanical properties of concrete at a higher level after heating to a high temperature.Originality/valueRecycled concrete aggregate enhances the concrete behaviour at high temperatures when it substitutes the natural aggregate by reasonable substitution (more than 25–30%). It also almost eliminates the possibility of spalling. Moreover, utilizing both supplementary cementitious materials with recycled concrete aggregate can improve the fire resistance of concrete. The incorporation of pulverized fly ash and slag in Portland cement or blended cement can generally keep the mechanical properties of concrete at a higher level after heating to a high temperature.

Okunrounmu, Oluwamuyiwa; Salem, Osama (Sam); Hadjisophocleous, George

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-06-2021-0036

The fire resistance of timber structures is heavily dependent on the fire behaviour of the connections between its structural elements. The experimental study presented in this paper aimed to investigate the fire performance of glued-laminated timber beam connections reinforced perpendicular-to-wood grain with self-tapping screws (STS).Design/methodology/approachTwo full-size fire experiments were conducted on glulam beam-end connections loaded in flexure bending. Two connection configurations, each utilizing four steel bolts arranged in two different patterns, were reinforced perpendicular to wood grain using STS. The bolt heads and nuts and the steel plate top and bottom edges were fire protected using wood plugs and strips, respectively. Each connection configuration was loaded to 100% of the ultimate design load of the weakest unreinforced configuration. The test assemblies were exposed to elevated temperatures that followed the CAN/ULC-S101 standard fire time–temperature curve.FindingsThe experimental results show that the influence of the STS was significant as it prevented the occurrence of wood splitting and row shear-out and as a result, increased the fire resistance time of the connections. The time to failure of both connection configurations exceeded the minimum fire resistance rating specified as 45 min for combustible construction in applicable building codes.Originality/valueThe experimental data show the effectiveness of a simple fire protection system (i.e. wood plugs and strips) along with the utilization of STS on the rotational behaviour, charring rate, fire resistance time and failure mode of the proposed hybrid mass timber beam-end connection configurations.

Fellouh, Abdelkadir; Bougara, Abdelkader; Piloto, Paulo; Benlakehal, Nourredine

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-09-2021-0057

Investigate the fire performance of eccentrically loaded concrete partially encased column (PEC), using the advanced calculation method (ANSYS 18.2, 2017) and the simple calculation method in Annex G of Eurocode 4 (EN 1994-1-2, 2005). This work examines the influence of a range of parameters on fire behaviour of the composite column including: eccentricity loading, slenderness, reinforcement, fire rating and fire scenario. In this study, ISO-834 (ISO834-1, 1999) was used as fire source.Design/methodology/approachCurrently, different methods of analysis used to assess the thermal behaviour of composite column exposed to fire. Analytical method named simplified calculation methods defined in European standard and numerical simulations named advanced calculation models are treated in this paper.FindingsThe load-bearing capacity of the composite column becomes very weak in the presence of the fire accident and eccentric loading, this recommends to avoid as much as possible eccentric loading during the design of construction building. The reinforcement has a slight influence on the temperature evolution; moreover, the reinforcement has a great contribution on the load capacity, especially in combined compression and bending. When only the two concrete sides are exposed to fire, the partially encased composite column presents a high load-bearing capacity value.Originality/valueThe use of a three-dimensional numerical model (ANSYS) allowed to describe easily the thermal behaviour of PEC columns under eccentric loading with the regard to the analytical method, which is based on three complex steps. In this study, the presence of the load eccentricity has found to have more effect on the load-bearing capacity than the slenderness of the composite column. Introducing a load eccentricity on the top of the column may have the same a reducing effect on the load-bearing capacity as the fire.

Choubey, Bishwajeet; Kumar, Virendra; Dutta, Sekhar Chandra; Saikia, Saurav Kumar

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-05-2021-0026

The purpose of the paper is to mathematically model and predict the characteristics of thermo-mechanically treated (TMT) rebar when subjected to elevated temperatures.Design/methodology/approachData were collected from a few selected studies for developing the constitutive relations. Using the exposed temperature and the duration of heating as independent variables, the empirical relations were developed for determining the changes in mechanical properties of TMT rebars at elevated temperatures.FindingsRecrystallization of TMT rebar crystals took place around 500 °C, which led to a decrease in the dislocation density along with the increase of large-sized grains, resulting in the degradation of strength. Up to a temperature range of 500 °C, the normalized fracture strength was higher, while the normalized fracture strain is not so high. This indicated a failure of brittle nature.Originality/valueThis is an original work done by others as a study to theoretically predict the mechanical behavior of TMT rebars when exposed to elevated temperature.HighlightsThe TMT bars showed brittleness characteristics up to 500 °C and showed ductility characteristics after that on account of its recrystallization and extensive tempering of the outer martensitic rim around that temperature.The comparison between the super ductile (SD) TMT and the regular TMT exhibit shows that the SD-TMT bars were about 1.5 times more ductile than the normal ones.

Suresh, N.; Rao, Vadiraj; Akshay, B.S.

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-10-2021-0064

The purpose of the study is to evaluate the suitability of post-fire curing for normal and Recycled Aggregate Concretes (RAC) with and without fibres.Design/methodology/approachThe study includes the testing of RAC specimens, i.e. 150 mm cubes and cylinders with 300 mm length and 150 mm diameter with hybrid fibres (0.15% polypropylene fibres + 0.35% steel fibres) along with fly ash. The specimens were exposed to elevated temperatures between 400 to 700°C with 100°C intervals for 2 h of duration and the post-fire exposed samples were further subjected to water curing for a period of 7 days. The compressive strength, split tensile strength and Rebound Hammer Number (RHN) were measured at room temperature, after exposure to elevated temperatures and post-fire curing.FindingsThe result shows that the compressive strength reduces by a maximum of 61.25% for 700°C and maximum retain in strength, i.e. 71.2% (in comparison to specimens kept at room temperature) is observed for 600°C post-fire cured specimens. The split tensile strength reduces by more than half for 500°C and above temperatures, whereas 400°C specimens exhibits a significant regain in strength after post-fire curing. To validate the results of compressive strength, the Rebound Hammer test has been conducted. The RHN value decreases by 41.3% for 700°C specimens and the effectiveness of post-fire curing is observed to be considerable up to 500°C.Practical implicationsThe conclusions from the study can be used in assessing the extent of damage and to check the suitability of post-fire curing in further continuing the utilisation of a fire damaged structure.Social implicationsUtilisation of secondary materials like recycled aggregates and fly ash can be made in the production of concrete.Originality/valueSpecimens with fibres performed better when compared to specimens without fibres and post-fire curing is found to be effective up to 500°C.

Upasiri, Irindu; Konthesingha, Chaminda; Nanayakkara, Anura; Poologanathan, Keerthan; Perampalam, Gatheeshgar; Perera, Dilini

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-10-2021-0066

Light-Gauge Steel Frame (LSF) structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel lipped channel sections negative fire performance, cavity insulation materials are utilized in the LSF configuration to enhance its fire performance. The applicability of lightweight concrete filling as cavity insulation in LSF and its effect on the fire performance of LSF are investigated under realistic design fire exposure, and results are compared with standard fire exposure.Design/methodology/approachA Finite Element model (FEM) was developed to simulate the fire performance of Light Gauge Steel Frame (LSF) walls exposed to realistic design fires. The model was developed utilising Abaqus subroutine to incorporate temperature-dependent properties of the material based on the heating and cooling phases of the realistic design fire temperature. The developed model was validated with the available experimental results and incorporated into a parametric study to evaluate the fire performance of conventional LSF walls compared to LSF walls with lightweight concrete filling under standard and realistic fire exposures.FindingsNovel FEM was developed incorporating temperature and phase (heating and cooling) dependent material properties in simulating the fire performance of structures exposed to realistic design fires. The validated FEM was utilised in the parametric study, and results exhibited that the LSF walls with lightweight concrete have shown better fire performance under insulation and load-bearing criteria in Eurocode parametric fire exposure. Foamed Concrete (FC) of 1,000 kg/m3 density showed best fire performance among lightweight concrete filling, followed by FC of 650 kg/m3 and Autoclaved Aerated Concrete (AAC) 600 kg/m3.Research limitations/implicationsThe developed FEM is capable of investigating the insulation and load-bearing fire ratings of LSF walls. However, with the availability of the elevated temperature mechanical properties of the LSF wall, materials developed model could be further extended to simulate the complete fire behaviour.Practical implicationsLSF structures are popular in building construction due to their lightweight, easy erecting and constructability characteristics. However, due to steel-lipped channel sections negative fire performance, cavity insulation materials are utilised in the LSF configuration to enhance its fire performance. The lightweight concrete filling in LSF is a novel idea that could be practically implemented in the construction, which would enhance both fire performance and the mechanical performance of LSF walls.Originality/valueLimited studies have investigated the fire performance of structural elements exposed to realistic design fires. Numerical models developed in those studies have considered a similar approach as models developed to simulate standard fire exposure. However, due to the heating phase and the cooling phase of the realistic design fires, the numerical model should incorporate both temperature and phase (heating and cooling phase) dependent properties, which was incorporated in this study and validated with the experimental results. Further lightweight concrete filling in LSF is a novel technique in which fire performance was investigated in this study.

Der, Batuhan; Raszková, Sylvie; Wald, František; Bihina, Gisèle; Gaigl, Christian; Rus, Vasile; Malaska, Mikko

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-11-2021-0070

This study aims to propose a new design value, based on experimental and numerical studies, for surface emissivity of zinc hot-dip galvanized members exposed to fire.Design/methodology/approachThe paper sums up experiments, used specimens and also shows results. Four experiments were performed in a horizontal furnace and one test in a fire compartment of the experimental building. Several tests were carried out for determination of the surface emissivity of galvanized steel structures in fire. The experimental and numerical studies were used for preparation of new generation of the structural steel fire standard Eurocode EN 1993-1-2:2025.FindingsHot-dip galvanizing is one of the most widely used processes for corrosion protection of steel products. The new design value for surface emissivity of zinc hot-dip galvanized members exposed to fire is determined using experimental results as 0.35. The value is proposed for next generation of EN 1993-1-2:2025. If hot-dip galvanization additionally can contribute beneficially to the fire resistance of unprotected steel members, it would be a huge economic advantage.Originality/valueExperimental studies in the past years have indicated the influence of hot-dip galvanizing on the heating of steel members. This study suggests 50% reduction of the surface emissivity of a carbon steel member. This amendment will be incorporated in future versions of Eurocodes 3 and 4 and has already been implemented in some fire design tools for steel members in order to consider the beneficial contribution of hot-dip galvanized for fire-resistance requirements of less than 60 min.

Abouleiwun, Khadejah Alameen; Elbakry, Hazem M.F.; Diab, Muhammad Ahmed; El-Fitiany, S.F.

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-03-2021-0012

In this study, the behavior of a multi-story flat plate structure during fire exposure is investigated using numerical simulations conducted with using ABAQUS software.Design/methodology/approachA three-dimensional finite element model is then carried out on the RC flat slab structure exposed to standard ISO-834 fire at different location arrangements. The model examines mid-span deflection, shear demand on the columns, bending moment and the membrane action of the floor slab.FindingsThe latter plays a main role to increase the capability and ductility of the slab at longer fire exposure to compensate the reduction in the flexural capacity. Also, shear demand in columns becomes bigger in cases of more than one surrounding slab exposed to fire at the same time.Originality/valueThis work focuses on the influence of the horizontal force on columns due to thermal expansion of slab which should be taken into account in the design of multistory multi-bay building considering it the same as the resulted horizontal force from the wind and seismic effect, the traveling fire and the restraint effect.

Yotsumoto, Naoya; Hirashima, Takeo; Toyoda, Koji

2022 Journal of Structural Fire Engineering

doi: 10.1108/jsfe-05-2021-0032

This paper aims to investigate the fire performance of composite beams when considering the hogging moment resistance of the fin-plate beam-to-girder joints including the effect of continuity of reinforcements.Design/methodology/approachExperiments on composite beams with fin-plate joints protected only at the beam ends are conducted. The test parameter is the specification of reinforcement, which affects the rotational restraint of the beam ends. In addition, a simple method for predicting the failure time of the beam using an evaluation model based on the bending moment resistance of the beam considering the hogging moment resistance of the fin-plate joint and the reinforcement is also presented.FindingsThe test results indicate that the failure time of the beam is extended by the hogging moment resistance of the joints. This is particularly noticeable when using a reinforcing bar with a large plastic deformation capability. The predicted failure times based on the evaluation method corresponded well with the test results.Originality/valueRecent studies have proposed large deformation analysis methods using FEM that can be used for fire-resistant design of beams including joints, but these cannot always be applicable in practice due to the cost and its complexity. Our method can consider the hogging moment resistance of the joint and the temperature distribution in the axial direction using a simple method without requirement of FEM.