Nor Hafizah Ramli Sulong

Effect of Epoxy Binder on Fire Protection and Bonding Strength of Intumescent Fire Protective Coatings for Steel

This study focuses on the effect of epoxy emulsion, a binder for producing water-borne intumescent fire protective coating for steel structures. The influence of binder on the fire resistive performance, char formation, thermal stability and bonding strength of the coatings were investigated in detail by using Bunsen burner test, thermogravimetry analysis (TGA), field emission scanning electron microscopy (FESEM) and Instron microtester. It was found that the fire protection performance and foam structure of coating sample D2 was significantly improved by adding 10wt% of epoxy resin which produced the greatest thickness of char layer. In addition, TGA results showed that the residue weight of coating D2 was higher than coating sample D3 with 15wt% of epoxy. This indicated that sample D2 has better anti-oxidation and thermal stability. The results of Instron microtester indicated that the bonding strength of the coatings was improved with the increase of epoxy content.

Behavior of Channel Shear Connectors in Normal and Light Weight Aggregate Concrete (Experimental and Analytical Study)

This paper describes five push-out tests carried out at the University of Malaya using channel shear connector. The tests study experimentally and analytically, the behavior of channel shear connectors embedded in normal and light weight aggregate concrete (LWAC). Limited push-out tests are used to measure the accuracy of a proposed nonlinear finite element model for typical push-out test specimens. Using this model, an extensive parametric study performed to arrive at prediction for shear capacity of channel connectors in LWAC. An equation is suggested for the shear capacity of these connectors in LWAC.

Local Stiffening of Steel I-Beams by Using CFRP Materials

This paper reports the experimental studies on the local stiffening of steel I-beams by using Carbon Fiber Reinforced Polymer (CFRP) strips. One of the problems which frequently occur for steel section is the large local deformation under point loads. To study the effects of applying CFRP for local stiffening, four steel I-beams were selected and tested to failure. The first beam had no steel stiffeners below the point loads and used as the control beam. The second beam had steel stiffeners and was not enhanced by using CFRP strip. The third and fourth beams had no steel stiffeners below the point loads and were strengthened on the compressive flanges by using two longitudinal CFRP strips. Also, the third and fourth specimens were strengthened on the web by using the latitudinal CFRP strips in the discrete and continual types, respectively. The results show that applying CFRP on the compressive flange and web increased the load bearing capacity and decreased the local and overall deformations appropriately. Also, the full-covering of the web seems to be the best type of web strengthening.

Failure Modes of CFRP Flexural Strengthened Steel I-Beams

This paper presents the experimental and numerical studies on the flexural strengthened steel I-beams by using Carbon Fiber Reinforced Polymer (CFRP) strips. Nowadays, strengthening existing steel structures by using CFRP has been widely interested. One of the common usages of CFRP to strengthen steel beams is the flexural upgrading. In this case, CFRP strips are pasted on the tensile flange to improve flexural behaviors. The problems that are frequently reported for CFRP strengthened steel beams are the debonding, delaminating (peeling), and splitting. Identification these failure modes are essential to provide an appropriate level of safety for strengthened steel beams. To investigate the CFRP failure modes, four strengthened steel I-beams were chosen. The CFRP plates with different thicknesses in single and double (splice) layers were used. Both experimental test (four-points bending test) and numerical simulation (full 3D simulation with ANSYS) were employed. The incremental loading was applied until failure while deformations in the critical regions were recorded. The results reveal that for the CFRP flexural strengthened steel beams the following failure modes occurred: (a) debonding at the CFRP plate tips, (b) debonding below point loads, (c) delaminating at the ends of CFRP plate, and (d) splitting below point loads. The sequence of failure modes depended on the specifications of CFRP plate. Some recommendations are provided to overcome/retard these failures.

An investigation into waterborne intumescent coating with different fillers for steel application

Purpose Modification and/or improvement of intumescent coating system by incorporating water-borne resin with an appropriate combination of flame-retardant additives and four different fillers, TiO2, Al(OH)3, Mg(OH)2, and CaCO3. Design/methodology/approach Coating mixtures are characterized using Bunsen burner, TG analysis, LOI, SEM, static immersion bath, FTIR and adhesion tester. Findings Results showed that the combination of coating with CaCO3 filler significantly improved fire protection performance because of its thickest char layer and equilibrium temperature was 264 °C. Char layer showed a uniform dense foam structure on micrograph and this formulation had adhesion strength of 2.13 MPa, which indicates effectiveness of the interface adhesion on substrate. Conversely, the combination of coating with Al(OH)3 exhibited highest oxygen index of 35%, which resulted excellent flammability resistance. Research limitations/implications This paper discusses only the effect of mineral fillers on properties o...

Effects of Lateral Bracing and Stiffeners on the CFRP Failure of Strengthened Steel Beams

In this paper, the effects of lateral bracing and web stiffeners on the Carbon Fibre Reinforced Polymer (CFRP) failure modes and buckling strength of the CFRP strengthened wide-flange steel I-beams are investigated experimentally. The study consisted of eight beams tested under static gradual load until failure. The main test variables were steel plate stiffeners, lateral bracings, and bonding of CFRP plates to beam soffits. The results showed that the use of steel plate stiffeners did not only prevent stress concentration below the point load, but it could also help to delay debonding of the externally bonded CFRP plate. The use of lateral bracing indicated a significant effect in preventing the CFRP splitting failure mode. In addition, the use of stiffeners with lateral bracing simultaneously, showed improvement in the in-plane flexural strength, stiffness and ductility of the CFRP strengthened I-beams.

Fuzzy multi-objective genetic algorithm in determination of optimum mid connection location of off-centre bracing system

Optimization of steel structures based on conventional methods is not trivial, mostly when the optimization procedure deals with linguistic variables. Off- Centre Brace (OCB) system is a particular braced system that consists of three brace elements. The non straight diagonal member of this system introduce eccentricity to the system. It allows architects to have more opening. In designing this system, designers often use trial and error method to locate the connection point of the brace elements by considering various parameters which affect the design such as opening and frame dimensions, cross section areas of brace elements and the location of brace element connection. Hence, finding the best connection point to have maximum stiffness, minimum weight of brace elements and considering designers linguistic concept through conventional methods is not trivial. In this paper, a method based on multi-object genetic algorithm implemented by fuzzy logic in determining the best connection point is proposed. This proposed method is so useful for designers in designing this system and assist them in making decision on prioritizing between the frame stiffness and brace frame weight in their design by linguistic variables.

Behavior of through Beam Connections Composed of CFSST Columns and Steel Beams by Finite Element Studying

Recent studies show that a through beam connections composed of concrete filled square steel tubular column and steel beam have been identified as an ideal rigid connection. In this paper a 3-D nonlinear finite element models were conducted for CFSST column and steel beam connection under monotonic load using ABAQUS software. Each model includes a CFSST column and single steel beam passing through the column. The main scopes are to identify the modes of beam failure and joint shear failure. In addition the effect of an extra shear plate welded to beam web inside the column was investigated. This result can be used for designing of through beam connection.

Artificial Intelligence in Designing Non Geometric Brace Systems

In this paper, a new method for designing a particular brace system is proposed. This type of brace system, which is called Non Geometric Brace system are mostly used in seismic area and it allows architects to have more opening in the panel. Non-straight diagonal member of this system introduces eccentricity and it is connected to the corner of the frame by a third member.In designing this system, designers often use trial and error method to locate the connection point of the braced elements considering various parameters affecting the design such as opening and frame dimensions, cross section areas of brace elements and the location of brace element connection. Hence finding the best connection point with maximum stiffness and minimum weight of brace elements with conventional method is not trivial. In this paper, a multi-object genetic algorithm is proposed in determining the best selection for connection point. Equations of feasible area are determined, followed by utilization of some operators such as selection, mutation, crossover and elitist genetic algorithm. Based on the plain aggregation approach for transforming the objective vector in scalar, some modification are proposed considering the priority between the frame stiffness and structures weight in this transformation.