Damage control of intumescent painting, Influence of imperfections in intumescent painting

From daily experience we know that, after erection of a steel structure, damage often occurs on steel columns and beams due to transport and assembly work.  In combination with intumescent painting it is normal practice that after some time all paintwork will be touched up and repaired if needed.  The problem today is that at that most of the time, steel cladding is already placed and the external parts of columns and beams cannot be reached anymore and stay therefore (partially) damaged.With the aid of thermoplastic calculation for some case studies, where the outer flange is partially loaded with an external fire instead of an ISO834 fire, we could define how big the damaged area may be and where it could be positioned without influence on the structural integrity of the protection.  Until today the SAFIR calculations are done for a R30 protection

Enhanced guidelines for reinforcement around openings

When designing concrete slabs, it is rather difficult to make a performant design that already takes the effect into account of unexpected openings. This is needed because it becomes unfortunately a common practice to add some openings at a final stage, which then requires rough time-saving rules. Even when the concrete is already casted some openings will be cut afterwards, certainly when a building gets refurbished in his life-time. Some standards require that if the reinforcement is designed for a homogeneous slab, the interrupted amount of reinforcement by the opening must be distributed around the opening. However, it is logical that for bigger openings, the flow of internal forces will be influenced by the opening itself. So it is clear that the previouslymentioned method can overestimates and, more dangerously, underestimates some reinforcements. To develop a more accurate design method, FEM analyses were conducted for different spans and opening sizes in slab areas with one- (central part) and two-way bearing (towards the edges) behaviour. Because flat slabs are much less sensible for openings, they are not included in this study. As result of this study, reduction and magnification factors were found which may be applied with an easy rule to obtain a better-performing method. These factors depend on the opening width/span ratio and must be normalized for the span in meters. In addition to the ultimate limit state, the service limit state was also verified. A magnification factor on the deformations must be applied, of the same order as that one on the lower reinforcement. This work was done in the scope of a new technical document about reinforcement for the Belgian Centre of Science and Technology for Construction Works

FDS versus EN-models comparison between Heskestad model out of EN and CFD results

For a rather big hippodrome we made a whole FDS model to investigate the influence of a car fire on the structure in terms of smoke and temperature actions on the structure.  As fire action we proposed a one or triple car fire.  Smoke evacuation is done by natural ventilation; open windows in the roof and doors at ground floor automatically coupled on the detection system.In this particular case we could deliver a report with the guarantee of a smoke free evacuation layer during the required time and no protection is needed for the structure.  A guide for the use of the hall was delivered with all the restrictions for a safe use of the construction.At this moment it seems to be useful, for featuring projects, to investigate if there is a difference with the localized fire scenarios from annex C out of EN 1991-1-2.  This is off course only valid for the structural impact of the fire load

Effect of upgrading concrete strength class on fire performance of reinforced concrete columns

peer reviewedHigh strength concrete (HSC) provides several advantages over normal strength concrete (NSC) and is being used in multi-story buildings for reducing the dimensions of the columns sections and increasing the net marketable area. However, upgrading of concrete strength class in a building may affect the fire performance, due to higher rates of strength loss with temperature and higher susceptibility to spalling of HSC compared with NSC. Reduction of columns sections also leads to increased member slenderness and faster temperature increase in the section core. These detrimental effects are well known, but their impact on fire performance of structures has not been established in terms of comparative advantage between NSC and HSC. In other words, it is not clear whether the consideration of fire resistance limits the opportunities for use of HSC for reducing the dimensions of columns sections in multi-story buildings. This research aims to address this question by comparing the fire behaviour of reinforced concrete columns made of NSC and HSC using nonlinear finite element modelling. The evolution of load bearing capacity of the columns is established as a function of the fire exposure duration. A 15-story car park structure is adopted as a case study with alternative designs for the columns based on strength classes ranging from C30 to C90. Results show that, although the replacement of NSC by HSC accelerates the reduction rate of columns capacity under fire, the columns generally have significant reserves in resistance leading to sufficient fire resistance. This study gives an insight into the impact of replacing stocky sections in NSC by more slender sections in HSC on fire resistance rating for multi-story structures

Performance of structural stainless steel following a fire

Stainless steel offers excellent mechanical properties as well as corrosion resistance and performs better in a fire compared to carbon steel in that it retains its strength and stiffness for a longer duration. The current paper is focussed on the post-fire condition, which has received limited attention to date from the research community. The motivation for the work is to show that stainless steel elements that have been exposed to fire can be re-instated with minimal additional costs in a short time frame. The paper proceeds with a description of recent material tests into the residual properties of grade 1.4301 austenitic stainless steel, following exposure to elevated temperature. Two different types of test were conducted and these are described. Firstly, a series of tensile tests were completed on coupons taken from a loaded stainless steel beam previously examined under fire conditions. Secondly, a set of virgin coupons (i.e. which have not been previously heated or tested) were exposed to different levels of elevated temperature and cooling procedures. This is with a view to understanding the ability of structural elements made from this material to survive a fire and continue in service. The results are employed along with other data obtained from the literature to conduct a detailed study into the design considerations. The collected data includes information on the proof and ultimate strengths, ultimate strain and Young's modulus and the extent to which these are affected following the occurrence of a fire. The study is done for ferritic, austenitic and duplex stainless steel. By focusing on the effect of a fire on the mechanical properties after cooling using a statistical approach, safety factors are proposed together with a reduced reliability index based on economic and social considerations.acceptedVersionPeer reviewe

Shear Capacity of Concrete Slabs Containing Void Formers

Concrete slabs with void formers are widely used in Europe, and through the application in a flat slab concept (biaxial bearing capacity) the shear and torsion resistance becomes important. With the knowledge of some critical tests for hollow core slabs there is a real need for a good understanding of the phenomena which can determine the shear capacity of such slabs. At the Warrington fire test laboratory of Ghent (Belgium) a test of such a system called Airdeck was executed several years ago. By the aid of comparison between EC2-1-2 design rules, thermo-plastic calculations and the reported phenomena we propose a design rule based on the test results.status: publishe

Vloeistofdichte vloeren

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Vlakke plaatvloeren met behulp van breedplaatvloeren

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Practical design examples related to robustness

status: Published onlin