Analysis of the fire resistance of a concrete shell roof structure

Report (2011)

Economic analysis of Stainless Steel- Reinforced Concrete members designed for a Fire Resistance of 2 hours

Report (2011)

While Stainless steel is used primarily for its corrosion resistance, there is a growing interest in other properties, such as mechanical, high temperature resistance, aesthetics and others. The ... [more ▼]

While Stainless steel is used primarily for its corrosion resistance, there is a growing interest in other properties, such as mechanical, high temperature resistance, aesthetics and others. The properties at high temperatures (400 – 650°C ) of stainless steels are known and put to use in a number of applications such as steam turbines and equipment for the chemical industry. Some research on the fire resistance of stainless steels has been carried out for welded I beams and for concrete-filled tubes, with positive results. However, there are no published results on the behavior of concrete reinforced with stainless steel rebar. In a preliminary research program conducted by the University of Liege for ISSF, a preliminary assessment of the performance of stainless steel reinforced concrete has been carried out, using computer simulation methods. This preliminary study has shown that stainless steel reinforced concrete members can behave better than carbon steel reinforced concrete members in fire situation. However, an economic analysis is still needed to determine whether stainless steel reinforcement can be interesting for practical applications. This report is divided in two parts. The first part presents the assumptions and the results of the numerical simulations performed by University of Liege. The numerical simulations aim to design stainless and carbon steel -reinforced concrete members satisfying to a fire resistance of 2 hours (Standard fire conditions). The two structural members considered in this study are a reinforced concrete beam and a composite slab (with the so-called « membrane » behavior). The numerical simulations are performed with the SAFIR 20011.a.3 software developed in University of Liege. The second part presents the assumptions and the results of the economic analysis of the structural members designed in the first part. The stainless and carbon steel –reinforced solutions for a fire resistance of 2 hours are compared on an economic basis. [less ▲]

Development of Multiaxial Constitutive Relationships for Concrete

Scientific conference (2011, March 18)

Recent research in structural fire engineering has shown that concrete or composite building structures can develop unexpected modes of strength when subjected to fire. Under certain conditions, a ... [more ▼]

Recent research in structural fire engineering has shown that concrete or composite building structures can develop unexpected modes of strength when subjected to fire. Under certain conditions, a structure will present a robust behavior that can dramatically increase its fire resistance compared to the fire resistance calculated by a predictive approach. An example of such robust behavior is the membrane action that can be developed by a structural slab in fire. However, the numerical simulation of such behaviors requires the development of reliable and accurate multiaxial constitutive relationships for modelling the behavior of concrete. This presentation is based on the work performed by the author during a six month research stay at CEA Saclay, in the team of Alain Millard. The aim of the research stay was to develop a concrete multiaxial model that can be used for the numerical analysis by the finite elements method of concrete structures in fire. To be able to accurately simulate the structural behavior during every phases of a natural fire, the concrete model includes plasticity and damage phenomena. The main features and parameters of the model are presented and its implementation in the softwares SAFIR and CAST3M is briefly discussed. Then, a few applications are given and the presentation ends with a comment on the remaining issues and perspectives. [less ▲]

A Comparison Between Explicit and Implicit Modelling of Transient Creep Strain in Concrete Uniaxial Constitutive Relationships

in Proceedings of the Fire and Materials 2011 Conference (2011, February)

Transient creep strain has to be included within the constitutive relationships for concrete at high temperatures. However, the necessity of taking into account this term explicitly is not clearly defined ... [more ▼]

Transient creep strain has to be included within the constitutive relationships for concrete at high temperatures. However, the necessity of taking into account this term explicitly is not clearly defined. In the Eurocode 2 uniaxial concrete material model, transient creep is included implicitly. This paper aims to highlight the capabilities and limitations of concrete uniaxial models at elevated temperatures for thermo-mechanical behaviour modelling, depending on the implicit or explicit consideration of transient creep strain in the model. The characteristics inherent to the two types of models are described and compared. It appears that one of the major limitations of implicit models concerns the unloading stiffness because implicit models treat transient creep as reversible. Based on numerical analysis performed on loaded concrete columns subjected to natural fire, it is shown that the stress-temperature paths experienced by structural concrete are varied and complicated and that concrete material models cannot handle properly these complex situations of unsteady temperatures and stresses without explicit consideration of transient creep. The paper proposes a new formulation of the Eurocode 2 concrete material model that contains an explicit term for transient creep. The new model is implemented in the software SAFIR and validated against experimental data of the mechanical strain developed by concrete cylinders under different unsteady temperatures and loads. It is shown that the actual material behaviour is better matched with the new explicit model than with the current implicit Eurocode 2 model. Finally, a comparison is given between experimental and calculated results on an axially restrained concrete column subjected to heating and cooling. [less ▲]

Optimization and analysis of lock gates in the framework of the "Seine-Escaut Est" waterway upgrading

in Bulletin of the Permanent International Association of Navigation Congresses (2010), (141), 11-26

This paper presents a research study performed on lock gates. It concerns the downstream lock gate of the one of the four new locks planned within the framework of the “Seine-Escaut Est (SEE)” project in ... [more ▼]

This paper presents a research study performed on lock gates. It concerns the downstream lock gate of the one of the four new locks planned within the framework of the “Seine-Escaut Est (SEE)” project in the Walloon Region of Belgium. At the stage of the basic preliminary design, it was decided to use four identical gates, all suspended and moved transversally to the lock. On this basis, the present work tackles different aspects of the lock gate study. The aim is double: on the one hand, to advance in the study of the four SEE project downstream lock gates, and on the other hand, to focus more particularly on lock gate structural analysis, notably the design, optimization and structural behavior in the case of ship impact. First, the design and optimization of the gate are performed, using the LBR5 lock gate optimization software and a linear elastic analysis. An optimized solution is obtained considering the best compromise between the cost and weight aspects of the structure. Then, this optimized gate is modeled with the nonlinear finite elements software FINELG. This program is used to conduct non linear numerical analysis of the effect of boat impact on the previously optimized downstream gate. Several analyses are performed, which allow for a discussion on the influence of the stiffener dimensions and the impact zone on the structural behavior of the gate submitted to the impact. Two different behaviors are brought to light, a ductile one and a fragile one. The results of the numerical analysis underline the importance of the development of a global plastic mechanism with the purpose of dissipating a large amount of energy. Finally, an analytical model presented in literature allows for the simplified calculation of the gate theoretical strength in case of ship impact, and the calculated value is compared with the computed results. [less ▲]

Preliminary Research Study on the Fire Resistance of Stainless Steel-Reinforced Concrete members

Report (2010)

In this project, it is examined whether and under which conditions the good resistance to high temperature of stainless steel bars can lead to better fire resistance when used in reinforced concrete ... [more ▼]

In this project, it is examined whether and under which conditions the good resistance to high temperature of stainless steel bars can lead to better fire resistance when used in reinforced concrete columns, beams and slabs working in tensile membrane action. [less ▲]

Numerical modelling of membrane action of composite slabs in fire situation

in Kodur, Venkatesh; Franssen, Jean-Marc (Eds.) Proceedings of the Sixth International Conference Structures in Fire (2010, June)

Membrane action in fire is now an intensively researched area, for which more improvement is always necessary. The paper presents some numerical simulations, done with the SAFIR program, in order to ... [more ▼]

Membrane action in fire is now an intensively researched area, for which more improvement is always necessary. The paper presents some numerical simulations, done with the SAFIR program, in order to derive more simple models for representing the partially protected composite floors in fire situation. The numerical models are calibrated using the results of three full scale tests that have been performed in recent years. [less ▲]

De Paepe-Willems Award 2010: Optimization and analysis of lock gates in the framework of the Seine-Escaut Est waterway upgrading

Conference (2010, May 10)

This paper presents a research study performed lock gates. It concerns the downstream lock gates of the one of the four new locks planned within the framework of the “Seine-Escaut Est (SEE)” project in ... [more ▼]

This paper presents a research study performed lock gates. It concerns the downstream lock gates of the one of the four new locks planned within the framework of the “Seine-Escaut Est (SEE)” project in the Walloon Region of Belgium. At the stage of the basic preliminary design, it was decided to use four identical gates, all suspended and manoeuvred by lateral movement. On this basis, the present work tackles with different aspects of the lock gate study. The aim is double: on one hand, to advance in the study of the solution of the four downstream lock gates of the SEE project, and the other hand, to concentrate more particularly on the lock gate analysis, among which their design, optimization and structural behavior in the case of ship impact. We began with the design and optimization of the gate. This work was realized with the LBR5 lock gate optimization software, according to a method comparing a representative number of optimized solutions considering at the same time the cost and weight aspects of the structure. This method leaded to an optimized solution of the downstream gate on which further studies are concentrated. Indeed this optimized gate was modeled with the non linear finite elements software FINELG. This program was used to conduct a non linear numerical analysis of the effect of a boat impact on the downstream gate. Several analyses were performed that allowed us to discuss on the influence of the stiffener dimensions and the influence of the impact zone on the gate structural behavior submitted to the impact. Two different behaviors have been brought to light, a ductile one and a fragile one. The results of the numerical analysis with finite elements have underlined the importance of the development of a global plastic mechanism with the purpose of dissipating a large amount of energy. Finally, we have used an analytical model to calculate the gate theoretical strength in a case of a ship impact, and to compare this value with the FEM numerical analysis results. [less ▲]

ROBUSTFIRE project: Benchmark study of floor slabs

Report (2009)

Lock gates - Part B: Ship impact

in PIANC International Workshop, 15-16 October 2009, Edt. Ph Rigo, PIANC, Brussels (2009, October)

This paper presents an overview of the state of art of ship impact analysis on lock gates. First, the different kinds of analysis are presented, which are: empirical approach, analytical-rational approach ... [more ▼]

This paper presents an overview of the state of art of ship impact analysis on lock gates. First, the different kinds of analysis are presented, which are: empirical approach, analytical-rational approach, and finite element methods performed with quasi-static analysis or dynamic analysis. A discussion on the hypothesis and the calculus time required by each method is carried out with a view to clarify the state-of-practice for engineers. Then, a quasi-static analysis by finite elements modeling a ship impact is performed on the specific case of a new lock gate designed in Belgium for the “Seine-Escaut Est” project. The results suggest some design recommendations to provide a ductile behavior and so impact strength for the gate structure. [less ▲]