An approach for evaluating vulnerability of bridges against fire hazard

In recent years, bridge fires are becoming a growing concern, however there is no specific requirements in codes and standards for design of bridge structural members against fire hazard.This paper presents an approach fordeveloping an importance factor for design of bridges against fire hazard.The proposed importance factor takes into account the degreeof vulnerability of a bridge to fire and also the critical nature of a bridge fromtraffic functionality point. The proposed importance factor for fire design, which is similar to the one currently used for evaluating wind, and snow loading in buildings,is validated against previous bridge fire incidents. It is shown through this validation that the proposed method for importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard and also to develop relevant design strategies for mitigating fire hazard in bridges

Comparative fire performance of high strength concrete columns with different types of fiber reinforcement

Reinforced concrete (RC) columns made of high strength concrete (HSC) experience faster degradation of capacity and spalling when exposed to fire. To mitigate such fire induced spalling and enhance fire resistance, fibers are often added to HSC mix. This paper presents results from fire resistance tests to illustrate the comparative fire performance of HSC columns with different fiber combinations. Four reinforced concrete (RC) columns made of HSC with plain, polypropylene, steel, and hybrid fibers were tested under design fire conditions and data from tests is utilized to evaluate the comparative fire behaviour of these columns. Results from these fire resistance experiments show that hybrid fiber reinforced HSC columns exhibit improved performance as compared to plain, polypropylene, and steel fiber reinforced columns

MACRO-ELEMENT MODEL OF A STEEL MOMENT FRAME SUBJECTED TO FIRE-INDUCED COLUMN LOSS

A progressive collapse mitigation strategy is to ensure load redistribution when a column fails due to fire. The study seeks to understand whether welded unreinforced flange-bolted web (WUF-B) moment connections can effectively redistribute loads in a structural system subjected to fire when a critical column is lost. A component (or macro-element) model was derived to simulate the WUF-B connection and validated against experimental tests and high-resolution finite element (FE) models of subassemblies at room temperature and at elevated temperature. The component model was then utilized in a 2D macro FE model of a ten-story steel-framed building subjected to the loss of a column during long fire exposure. This paper presents the collapse mechanisms and quantifies structural performance based on acceptance criteria. A parametric study on location of column loss and fire occurrence is also included

A Numerical Model for Tracing Structural Response of Ultra-High Performance Concrete Beams

This paper presents a finite element-based numerical model for tracing the behavior of ultra-high performance concrete (UHPC) beams. The model developed in ABAQUS can account for stress–strain response of UHPC and reinforcing bar in both tension and compression, bond between concrete and reinforcing steel, and strain hardening effects in bars and UHPC and can trace the detailed response of UHPC beams in the entire range of loading. This model is validated by comparing predicted response parameters including load-strain, load-deflection, and crack propagation against experimental data governed from tests on UHPC beams with different reinforcement ratios, fiber volume fractions, and loading configurations (shear and flexural loading). The validated model is applied to quantify the contribution of stirrups and concrete to shear strength of beams so as to explore the feasibility of removing shear reinforcement in UHPC beams

Residual load bearing capacity of structures exposed to fire

peer reviewe

Residual load bearing capacity of structures exposed to fire

peer reviewe

Effect of local instability on fire response of steel beams

Purpose – This purpose of this paper is to quantify the effect of local instability arising from high shear loading on response of steel girders subjected to fire conditions. Design/methodology/approach – A three-dimensional nonlinear finite element model able to evaluate behavior of fire-exposed steel girders is developed. This model, is capable of predicting fire response of steel girders taking into consideration flexural, shear and deflection limit states. Findings – Results obtained from numerical studies show that shear capacity can degrade at a higher pace than flexural capacity under certain loading scenarios, and hence, failure can result from shear effects prior to attaining failure in flexural mode. Originality/value – The developed model is unique and provides valuable insight (and information) to the fire response of typical hot-rolled steel girder subjected to high shear loading

Designing Steel Structures for Fire Safety

In this book the information relevant to fire design of steel structures is presented in a systematic way in seven chapters. Each Chapter begins with an introduction of various concepts to be covered and follows with detailed explanation of the concepts. The calculation methods as relevant to code provisions (in Europe, North America or other continents) are discussed in detail. Worked examples relevant to calculation methodologies on simple structural elements are presented. For the case of complete structures guidance on how analysis can be carried out is presented. Chapter 1 of the book is devoted to providing relevant background information to codes and standards and principles of fire resistance design. The chapter discusses the fire safety design philosophies, prescriptive and performance-based design fire safety design issues. Chapter 2 deals with basis of design and mechanical loads. The load combinations to be considered for fire design of structures, as per European and North American codes and standards, are discussed. Chapter 3 discusses the detailed steps involved in establishing the fire scenarios for various cases. Both Eurocode and North American temperature-time relationships are discussed. Procedures in this section allow the designer to establish the time-temperature relationships or heat flux evolutions under a specified design fire. Chapter 4 deals with steps associated in establishing the temperature history in the steel structure, resulting from fire temperature. The various approaches for undertaking thermal analysis by simple calculation models are discussed. Chapter 5 presents the steps associated for establishing the mechanical response of a structure exposed to fire. The possibilities for analysis at different levels: member level, sub-structure level and global level are discussed. Full details related to simple calculation methods for undertaking strength analysis at member level are presented. Chapter 6 is devoted to fire resistance issues associated with design of joints. The steps associated with the fire resistance of a bolted or a welded joint through simplified and detailed procedure are discussed. Chapter 7 deals with thermal and mechanical analysis through advanced calculation models. The procedures involved in the sub-structure analysis or global structural analysis under fire exposure is fully discussed. Case studies are presented to illustrate the detailed fire resistance analysis of various structures. Chapter 8 presents four design examples showing how a complex structure can be designed using the concept of element or sub-structure analysis. The book concludes with two Annexes which present some of the design information related to material properties and temperature profiles. Annex 1 focuses on thermal properties of structural steel and commonly used insulation materials and resulting temperature profiles in steel. Annex 2 focuses on mechanical properties of structural steel

Simulation and validation of wake deflection in vertical-axis wind turbines

Electrical Engineering | Sustainable Energy Technolog