Fire Propagation Performance of Intumescent Fire Protective Coatings Using Eggshells as a Novel Biofiller

This paper aims to synthesize and characterize an effective intumescent fire protective coating that incorporates eggshell powder as a novel biofiller. The performances of thermal stability, char formation, fire propagation, water resistance, and adhesion strength of coatings have been evaluated. A few intumescent flame-retardant coatings based on these three ecofriendly fire retardant additives ammonium polyphosphate phase II, pentaerythritol and melamine mixed together with flame-retardant fillers, and acrylic binder have been prepared and designed for steel. The fire performance of the coatings has conducted employing BS 476: Part 6-Fire propagation test. The foam structures of the intumescent coatings have been observed using field emission scanning electron microscopy. On exposure, the coated specimens’ B, C, and D had been certified to be Class 0 due to the fact that their fire propagation indexes were less than 12. Incorporation of ecofriendly eggshell, biofiller into formulation D led to excellent performance in fire stopping (index value, (I)=4.3) and antioxidation of intumescent coating. The coating is also found to be quite effective in water repellency, uniform foam structure, and adhesion strength

A Review on Strengthening Steel Beams Using FRP under Fatigue

In recent decades, the application of fibre-reinforced polymer (FRP) composites for strengthening structural elements has become an efficient option to meet the increased cyclic loads or repair due to corrosion or fatigue cracking. Hence, the objective of this study is to explore the existing FRP reinforcing techniques to care for fatigue damaged structural steel elements. This study covers the surface treatment techniques, adhesive curing, and support conditions under cyclic loading including fatigue performance, crack propagation, and failure modes with finite element (FE) simulation of the steel bridge girders and structural elements. FRP strengthening composites delay initial cracking, reduce the crack growth rate, extend the fatigue life, and decrease the stiffness decay with residual deflection. Prestressed carbon fibre-reinforced polymer (CFRP) is the best strengthening option. End anchorage prevents debonding of the CRRP strips at the beam ends by reducing the local interfacial shear and peel stresses. Hybrid-joint, nanoadhesive, and carbon-flex can also be attractive for strengthening systems

Fire-resistive performance of intumescent flame-retardant coatings for steel

The purpose of this work is to study the efficiency and effect of different intumescent flame-retardant formulations on the performance of steel in the event of a fire. The formulations are based on flame-retardant additives into which silica fume (SF) as a binder and chicken eggshell (CES) as a flame-retardant filler have been incorporated to synthesize water-based intumescent coatings. The influence of binder and filler on the properties and fire-resistive performance of the coatings were investigated by using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), small scale Bunsen burner test and furnace test. TGA results showed that by adding SF alone or in combination with CES, the residual weight and thermal stability of the coatings were increased, while showing improved surface structure in the SEM images. The combination of SF, CES and flame retardant additives showed the best fire protection performance with the highest thermal stability, greatest expansion and densest surface structure while having sufficient adhesion to remain in place during fire exposure.</p

Performance of solvent-borne intumescent fire protective coating with Palm oil clinker as novel bio-filler on steel

This research deals with contribution of hybrid fillers with palm oil clinker (POC) as a novel bio-filler in solvent-borne intumescent fire protective coating for steel. The hybrid fillers with POC were mixed in appropriate amount of additives and acrylic binder to produce the intumescent coatings. The intumescent coatings were characterized by using Bunsen burner test, surface spread of flame, thermogravimetric analysis, field emission scanning electron microscopy, static immersion and Instron micro tester equipment. Specimen with POC as a single filler has significantly enhanced the fire protection performances of the intumescent coating due to the high thermal stability of POC, where less than 10% of temperature different when compared to specimens with hybrid fillers. From the flame spread classification, class 1 is the best classification while Class 4 is the worst and considered high risk. All specimens was classified as class 1 since the final spread of flame was less than 165 mm. For hybrid fillers composition, specimen consist of POC/Al(OH)3/TiO2 has significantly improved the water resistance of the coating due to the low solubility of Al(OH)3 in water, while specimen contain of Mg(OH)2 had higher mechanical strength due to the strong bonding between the metal surface and acrylic binder/Mg(OH)2 filler. It was found that coating with the incorporation of all hybrid fillers gives excellent fire protection performance with good thermal stability, water resistance and mechanical properties. It can be concluded that, the selection of appropriate composition of fillers and binder in intumescent coating was highly influence the intumescent coating performance.</p

Genetic algorithm in locating the optimum mid-connection of Off-Centre braced system

In this article, a particular Off-Centre braced system is examined. This bracing system consists of three members, where the diagonal member is not straight and it is connected to the corner of the frame by a third member. The out-of-straightness of the diagonal member introduces eccentricity to the system. This system improves the energy dissipation due to earthquake as well as its eccentricity allows architects to have more openings in the panel areas. In this regard, the location of brace elements connection point has significant effect on the stiffness of the system. In order to assess the influence of the connection position and other parameters such as cross section of brace elements and span/height ratio of the braced frame on the stiffness of the system, analytical equations have been developed. A new method based on Genetic algorithm (GA) to obtain the connection point is also proposed. The importance of elite individuals together with selection, mutation and crossover operator between populations are also examined. In order to achieve the best and practical location of the connection point, two equations for boundary conditions with regards to the opening dimensions are set in a computer model developed in MATLAB program. The results indicate that the stiffness decreases as the connection point moves closer to the corner of the frame. Additionally, the proposed method is proven to be efficient in determining the connection point due to its accuracy and minimal computational time required compare to conventional trial and error method.</p

Effect of axial restraints on top-seat angle connections at elevated temperatures

In this study, a finite element model of a top-seat angle connection at elevated temperature is developed to study the effect of axial restraints on the connection behavior. Models are first validated with existing fire test results of top-seat angle connection. Non-linear behavior of the materials was modeled with the definition of elastic-plastic multi-linear properties and frictional contact between surfaces is included to simulate actual conditions. Validation of the model behavior shows that the model is in good agreement with existing experimental results and therefore the model is used for further study on the effect of axial restraints towards connection behavior. Both isothermal and anisothermal conditions were analyzed considering the effect of axial restraints. Results from the model shows that an increase in axial restraints has increased connection capacity while the stiffness remains similar for low axial levels. On the other hand, the shrinkage of the beam, may lead to tensional axial loads, causing axial pulling on the connection, resulting in higher deformation and different deformation patterns of the component angle sections. Effect on the design guidelines for connection design with axial restraints provided by Eurocode 3:2005 (Part 1-8) is also discussed at the end.</p

Investigation on end anchoring of CFRP strengthened steel I-beams

Problems that frequently occur in carbon fibre reinforced polymer (CFRP) flexural strengthened steel structures include the peeling and debonding at the tip of the CFRP plate. This paper presents a study on the effectiveness of using steel plates and bolts as end-anchors to address these problems. Four steel I-beams were tested to failure. The first specimen was not strengthened and was used as the control beam. The second beam was strengthened with a CFRP plate without any end-anchoring. The third and fourth specimens were strengthened and end-anchored using steel plates and bolts. The number of bolts was the same, however, the length of the steel anchor plates was varied. The beams were tested under four point loads and loaded incrementally while the deflection and strain readings on the critical parts of the beams were recorded. For the numerical study, full three dimensional (3D) simulation and nonlinear static analysis was carried out using ANSYS software. The results indicate that the anchored beams had higher load capacities of up to 24% compared to the non-strengthened beam. End-anchoring with closer bolt spacing was more effective. Both experimental and numerical results are in good agreement highlighting the accuracy of the developed numerical model.</p

Nonlinear response of tension leg platform subjected to wave, current and wind forces

Tension leg platform (TLP) superstructure and submerged areas are being subjected to wind and wave forces during their lifetime, yet the magnitude of each respective energy density affects the TLP response. The present work aims to study the influence of possible load combinations on the response of the TLP. In order to achieve this objective, the Joint North Sea Wave Project (JONSWAP) spectrum and Simiu and Leigh wind spectrum were used for the computation of wave and wind spectral densities. Airy wave theory and Morison equation were adopted for the calculation of wave kinematics and forces on the platform. The variable submergence, drag force in the Morison equation, tension fluctuation from large displacement were the sources of nonlinearities considered. Subsequently, mathematical formulation for the dynamic analysis of intact and a tether-missing TLP was developed in FORTRAN software. The nonlinear equation of motion was solved using Newmark-Beta scheme coded in the software. From our findings, the sea state with high significant wave height and wave period suppressed the effect of current and wind loads on the TLP motion response as compared to the sea state with low sea state parameters. The effect of wind drag force increases the surge and heave responses, but the overall influence of the current drag depends on the magnitude of the wave energy spectrum. There was no abrupt behaviour when a tether was missing although the loss of tether’s stiffness slightly affects the TLP motion and tension variation.</p

Experimental assessment of channel shear connectors under monotonic and fully reversed cyclic loading in high strength concrete

Two series of modified push-out tests under monotonic and low cycle fatigue load were performed to study the behaviour of channel shear connectors embedded in high strength concrete (HSC) slab. In each series, four push-out specimens were tested covering different sizes of channel shear connector and different strength level of HSC. Evaluation of National Building Code of Canada (NBC) for load capacities of channel shear connectors in HSC is also covered. The results show adequate ductility of channel shear connectors in HSC. All specimens have channel fracture type of failure and showed 8-17% strength degradation under low cyclic fatigue loading compared to the monotonic loading. In application of channel shear connectors embedded in HSC, achieved strength degradation rate is lower than the other concrete types (other types of concrete means those studied in previous investigations, which included plain concrete, reinforced concrete (RC), fiber reinforced concrete (FRC) engineered cementitious composite (ECC), polypropylene (PP) concrete and light weight aggregate concrete (LWAC)). Also, it was determined that the Canadian design code is quite unconservative for the prediction of strength capacity of channel shear connectors in HSC.</p

Behavior of tilted angle shear connectors

According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.</p