Fire Resistance Of Structural Members Research Articles

Discovering causal models for structural, construction and defense-related engineering phenomena

Causality, the science of cause and effect, has made it possible to create a new family of models. Such models are often referred to as causal models. Unlike those of mathematical, numerical, empirical, or machine learning (ML) nature, causal models hope to tie the cause(s) to the effect(s) pertaining to a phenomenon (i.e., data generating process) through causal principles. This paper presents one of the first works at creating causal models in the area of structural and construction engineering. To this end, this paper starts with a brief review of the principles of causality and then adopts four causal discovery algorithms, namely, PC (Peter-Clark), FCI (fast causal inference), GES (greedy equivalence search), and GRaSP (greedy relaxation of the sparsest permutation), have been used to examine four phenomena, including predicting the load-bearing capacity of axially loaded members, fire resistance of structural members, shear strength of beams, and resistance of walls against impulsive (blast) loading. Findings from this study reveal the possibility and merit of discovering complete and partial causal models. Finally, this study also proposes two simple metrics that can help assess the performance of causal discovery algorithms.

Causal discovery and inference for evaluating fire resistance of structural members through causal learning and domain knowledge

AbstractExperiments remain the gold standard to establish an understanding of fire‐related phenomena. A primary goal in designing tests is to uncover the data generating process (i.e., the how and why the observations we see come to be); or simply what causes such observations. Uncovering such a process not only advances our knowledge but also provides us with the capability to be able to predict phenomena accurately. This paper presents an approach that leverages causal discovery and causal inference to evaluate the fire resistance of structural members. In this approach, causal discovery algorithms are adopted to uncover the causal structure between key variables pertaining to the fire resistance of reinforced concrete columns. Then, companion inference algorithms are applied to infer (estimate) the influence of each variable on the fire resistance given a specific intervention. Finally, this study ends by contrasting the algorithmic causal discovery with that obtained from domain knowledge and traditional machine learning. Our findings clearly show the potential and merit of adopting causality into our domain.

Effect of temperature on mechanical properties of ultra‐high performance concrete

SummaryHigh temperature mechanical property data are needed for evaluating fire resistance of structural members. Being a relatively new construction material, there is a lack of temperature‐dependent mechanical property data on ultra‐high performance concrete (UHPC). To address this knowledge gap, this paper presents results from an experimental study on the effect of temperature on mechanical properties of UHPC. Specimens made of two UHPC mixes: one with only steel fibers (UHPC‐S) and the other with hybrid fibers, that is, both steel and polypropylene (UHPC‐H), were tested under different heating conditions in 20 to 750°C temperature range. Compressive strength, tensile strength, stress‐strain response, and elastic modulus of UHPC were evaluated at various temperatures. Results generated from these property tests on UHPC were compared with property relations specified in design codes for conventional normal strength concrete (NSC) and high strength concrete (HSC). The comparisons show that UHPC experiences faster degradation in compressive strength and elastic modulus as compared to conventional concrete. However, UHPC exhibits slower degradation in tensile strength and ductility at elevated temperatures due to the presence of steel fibers. Data generated from these property tests were utilized to propose relations for expressing the mechanical properties of UHPC as a function of temperature and these relations can be used as input to numerical models for evaluating fire resistance of structures made of UHPC.

Performance-Based Fire Safety Design of Special Structures in Germany

The objective of this article is the illustration of the calculation of natural fires and fire resistance of structural members based on the Eurocodes of two types of special structures, in this case a railway bridge and an airplane hangar. The railway bridge has a width of nearly 70 meters and consists of steel beams and a massive concrete slab that are supported by massive columns and walls and for that reason can be compared to a tunnel. The load-bearing structure of the roof of the hangars is made of steel and is supported by steel columns. The choice of a fire scenario on the safe side is crucial for the design process of the unprotected steel structure.

Evaluating Fire Resistance of Steel Girders in Bridges

In current practice, no special measures are applied for enhancing structural fire safety of steel bridge girders. Further, there is very limited information and research data in the literature on the fire resistance of structural members in bridges. In this paper, the fire response of a steel bridge girder under different conditions is evaluated using the FEM computer program ANSYS. In the analysis, the critical factors that influence fire resistance, namely, fire scenario, fire insulation, and composite action arising from steel-concrete interaction, are accounted for. Results from numerical studies show that the composite action arising from steel-girder-concrete-slab interaction significantly enhances the structuralperformance(and fireresistance)ofasteelbridgegirderunder fireconditions.Othersignificantfactorsthatinfluence fireresistanceof steel bridge girders are fire insulation and type of fire scenario. DOI: 10.1061/(ASCE)BE.1943-5592.0000412. © 2013 American Society of Civil Engineers. CE Database subject headings: Fires; Fire resistance; Girder bridges; Steel bridges. Author keywords: Bridge fires; Fire resistance; Steel girders; FEM analysis.

A Simplified Approach for Predicting Temperature Profile in Steel Members With Locally Damaged Fire Protection

Steel structures in building are to be provided with external insulation to delay temperature rise and associated strength degradation when exposed to fire. However, due to delicateness and fragility of some insulation systems, damage might occur in these insulation systems during their service life, and such damage can lead to rapid rise in steel temperature and result in lower fire resistance of structural members. Currently, there are no simple calculation methods for quantifying the effect of insulation loss on steel temperature. In this paper, a simple approach is proposed for tracing the temperature profile in steel members with partial loss of fire protection. The method is developed based on modifying the existing one-dimensional finite difference solutions of the heat transfer equation. The validity of the proposed method is established by comparing the predictions from the proposed method against temperatures obtained from finite element heat transfer model that is created using ANSYS. The comparisons indicate that the proposed method is capable of predicting temperature in steel members with partially damaged insulation to a good degree of accuracy over a wide range of situations. Further, the simplicity of the proposed method makes it attractive for use in fire resistance assessment in steel structures.

Modelling of reinforced concrete structures in fire

In this paper a robust finite-element procedure is presented for three-dimensional modelling of reinforced concrete structures under fire conditions. In this non-linear procedure a reinforced concrete building is modelled as an assembly of finite plain beam–column and slab elements, reinforcing steel bar elements and bond-link elements. Both material and geometric non-linearities are considered in the model. To consider the effects of concrete spalling on the thermal and structural behaviours of concrete structures under fire conditions, a ‘void layer' and ‘void segment' are introduced to represent the spalled-concrete part within concrete slabs, beams and columns. A critical temperature is used as the concrete spalling criterion. These developments enable the model to simulate quantitatively the effects of concrete spalling on both the thermal and structural behaviours of reinforced concrete structures in fire. A series of analyses are also conducted on a generic reinforced concrete building. The results indicate that, under fire conditions, the structural behaviour of isolated members with the concrete spalled is very different compared with the behaviour exhibited when embedded within a building. The influence of bond conditions between concrete and reinforcing steel bars on the fire resistance of structural members is significant. The global structural fire resistance of the reinforced concrete building is significantly affected by the concrete spalling on their members, in which the most important member is floor slabs.

Analyses Of The Impact Of Loss Of Spray-applied Fire Protection On The Fire Resistance Of Steel Columns

The loss of fire protection material is generally acknowledged to reduce the fire resistance of protected steel structural members, but the magnitude of the reduction is unknown. Two analyses are applied to assess the heat transfer to a steel column and investigate the proportional decrease in the fire resistance when relatively minor portions of spray-applied fire protection material are removed. One method is an elementary, lumped heat capacity analysis (LHC). The second method involves the application of a three-dimensional, finite element model. In both cases, the column is assumed to be subjected to the standard ASTM E119 fire resistance test. The predicted temperature distributions within the member over time are used in conjunction with the thermal endpoint criteria specified in ASTM E119. The LHC analysis of the temperature rise of the entire column shows the area of missing protection to be of little consequence in determining the average temperature of the entire column. The column temperatures calculated using the LHC approach are primarily dependent on the original fire resistance of the column for the small areas of missing protection examined. In contrast, the area of the missing protection and the size of the column are found to have an appreciable effect upon the thermal response of the column regardless of the protection thickness using the finite element analysis. Introduction ASTM E119 documents the standard test to assess the fire resistance of structural members in North America [1]. The temperature endpoint criteria for steel columns are: an average temperature of 538°C and 649 °C at a single point [1]. One method of protecting steel columns is through the use of an insulating, spray-applied fire protection material. Several such materials are identified as part of listed steel column assembly designs included in the Fire Resistance Directory [2]. The intent of this study is to compare the results from two separate analysis methods, one relatively simple and one relative complex, to provide an estimate of the impact of missing fire protection material on the temperature rise experienced by a steel column exposed to the conditions associated with the ASTM E119 standard test. One method, referred to as the LHC analysis, uses an algebraic equation that is reiterated to determine the temperature rise of the column [3]. The second analysis method uses a finite element model, FIRES-T3, to conduct the analysis [4]. Assessing the impact of the local temperature rise on the structural performance of the column is beyond the scope of this paper. However, such is needed to conduct a more comprehensive analysis of the impact of the missing protection, rather than applying the endpoint temperature criteria from ASTM E119. 1 Copyright © International Association for Fire Safety Science

Analytical Methods to Evaluate Fire Resistance of Structural Members

Engineering standards will need to be developed to outline analysis methods to support performance-based codes being developed in the United States. This paper provides an overview of the state-of-the-art engineering methods for structural fire protection applications that could be incorporated into such an engineering standard. The overview addresses the technical basis, applicability, and utility of a representative sample of available calculation methods. These methods apply to a wide variety of structural members comprised of concrete, masonry, steel, and timber. An analytical assessment of fire resistance includes four principal aspects: fire exposure, material effects, thermal response, and structural response. A description of the fire exposure focuses on the heating conditions associated with the exposure. Material effects include material properties as a function of temperature along with physical or chemical effects of the elevated temperature exposure. Analyzing the thermal response results in determining the temperature profile within the exposed structural member. The ability of the structural member to support a load despite the effects of the fire exposure are incorporated in the analysis of structural response.

Performance-based fire resistance design of concrete-filled steel columns

A simplified design equation for evaluating the fire resistance of concrete-filled circular and square hollow structural steel (HSS) columns is presented. The equation is expressed in terms of various structural design parameters affecting the fire resistance, and hence can easily be integrated into conventional structural design. This equation can be used to evaluate the fire resistance of HSS columns filled with various types of concrete filling. The use of the design equation greatly facilitates the calculation of the fire resistance of structural members on a performance basis. It also enables the designer to find cost-effective solutions in providing the required fire resistance performance for structural members, simply by varying the parameters of the members. The applicability of the proposed equation to a design situation is illustrated through a numerical example. Practical guidelines that can be implemented during the design and construction phase, and which have beneficial effects on the fire resistance behaviour concrete-filled of hollow steel columns, are also presented.

A procedure to calculate fire resistance of structural members

AbstractProgress in the field of theoretical prediction of fire resistance has been rapid in recent years. A procedure has been developed at the National Research Council of Canada for calculation of the fire resistance of structural members. The various steps in the construction of a mathematical model to calculate temperatures, deformations and strength are shown using as an example the calculation of the fire resistance of a cylindrical tubular steel column filled with concrete. A comparison of results calculated using the model with those of a fire test is also discussed.