Mohd Hanim Osman

Prediction of the fatigue life of slender web plates using fracture mechanics concepts

The results of a series of fatigue tests, on slender plate girders subjected to repeated shear loading, are summarised and used to establish a lower bound fatigue strength curve for the welded web boundary, based on geometric or principal surface stress ranges. The propagation of a semi-elliptical surface crack, through the thickness of a plate, is studied using fracture mechanics concepts. An extensive parametric study indicates that the initial crack size and aspect ratio, the geometric stress concentration at the weld toe, and the plate thickness, all have a significant influence on fatigue strength. It is concluded that the fracture mechanics approach requires specification of a number of parameters which are difficult to determine in practice. However, having specified a realistic crack size and aspect ratio and an approximate stress concentration at the weld toe, the solution can be calibrated against available experimental fatigue strength curves.

Residual shear strength of fatigue cracked slender web panels

A series of quasi-static and fatigue tests on short span, slender plate girders subjected to predominantly shear loading is described. The fatigue test results are presented in terms of the normalised load range versus the number of load cycles to failure, and compared with other available test data. A simple procedure for predicting the residual shear strength of a fatigue cracked web panel, based on an assumed equilibrium stress field, is developed and shows reasonable correlation with the test results.

Prionljivost armaturne šipke u spoju od polimera armiranog vlaknima

U ovom se radu prikazuje ispitivanje prianjajna i proklizavanja armaturne šipke u novorazvijenoj injektiranoj spojnici sa staklenim vlaknima (eng. glass fiberreinforced polymer GFRP). Ukupno dvadeset sedam uzoraka ispitano je postupnim povećavanjem osnog vlačnog opterećenja. Rezultati dobiveni ispitivanjem uzoraka usvojeni su za modeliranje ovisnosti naprezanje prianjanja proklizavanje, što je uspoređeno sa zahtjevima iz normi i odredbi. Rezultati pokazuju da se u konusnim spojnicama razvija veća čvrstoća prianjanja i otpornost na opterećenje usporedo sa smanjenjem promjera u srednjem dijelu.

Thermal Behaviour of Beams with Slant End-Plate Connection Subjected to Nonsymmetric Gravity Load

Research on the steel structures with confining of axial expansion in fixed beams has been quite intensive in the past decade. It is well established that the thermal behaviour has a key influence on steel structural behaviours. This paper describes mechanical behaviour of beams with bolted slant end-plate connection with nonsymmetric gravity load, subjected to temperature increase. Furthermore, the performance of slant connections of beams in steel moment frame structures in the elastic field is investigated. The proposed model proved that this flexible connection system could successfully decrease the extra thermal induced axial force by both of the friction force dissipation among two faces of slant connection and a small upward movement on the slant plane. The applicability of primary assumption is illustrated. The results from the proposed model are examined within various slant angles, thermal and friction factors. It can be concluded that higher thermal conditions are tolerable when slanting connection is used.

Seismic and Progressive Collapse Assessment of New Proposed Steel Connection

The performance of a new proposed steel connection against seismic loading and progressive collapse was experimentally and numerically investigated in this paper. The seismic performance included interstory drift angle and flexural strength evaluated in accordance with 2010 AISC Seismic Provisions whereas progressive collapse assessment was based on satisfaction of the acceptance criteria by rotational capacities of the connection provided in UFC 4-023-03 guideline. The results confirmed that the new proposed connection was capable of achieving adequate rotational capacity and developing the full inelastic capacity of the connecting beam. In addition, an excellent cyclic behavior was demonstrated by proposed connection which enhance interstory drift angle. Based on the results the proposed connection has adequate intensity and ductility to classify it as full-strength and ductile connection.

Cyclic and Explosive Evaluation of New Proposed Steel Joint

The behaviour of a novel steel beam-to-column connection, the saddlebag, subjected to cyclic and progressive collapse, was evaluated in this paper. The cyclic behaviour considered the interstory drift angle and flexural strength in accordance with 2010 AISC Seismic Provisions, while progressive collapse assessment was evaluated through the plastic hinge rotation angle based on acceptance criteria provided in the UFC 4-023-03 guideline. From the cyclic test, one complete cycle of an interstory drift angle of 0.06 rad was satisfied for the saddlebag connection, which is an indication of the effectiveness in accordance with 2010 AISC Seismic Provisions. Besides, the new proposed connection developed adequate catenary action, which is a fundamental criterion to resist against progressive collapse. The resulting fuller hysteretic loops with large energy dissipation capacity in the proposed saddlebag connection guarantee its ability to address the inelastic deformation demands in earthquake conditions.

Seismic Performance of Steel Frames with Semirigid Connections

The nonlinear stiffness matrix method was incorporated to investigate the structural performance of steel portal frames with semirigid connections. A portal frame with unstiffened extended end-plate connection was designed to demonstrate the adequacy of the proposed method. Besides, the seismic performance of steel portal frames with semirigid connections was investigated through time history analysis where kinematic hysteresis model was assigned to semirigid connections to account for energy dissipation and unloading stiffness. Based on the results of the study, it was found that generally semirigid connections influenced the force distribution which resulted in the decrease in base shear and lighter frame compared to the rigid one. The results also indicated that there was no direct relationship between maximum displacement at the top and connection stiffness in high-rise frames.

Permeability and tensile strength of concrete with Arabic gum biopolymer

The use of materials of vegetal origin is increasingly being promoted in many industries due to their cost effectiveness and the rising sensitivity to environmental protection and sustainability. Arabic Gum Biopolymer (AGB) is a wild plant byproduct that is abundantly found in Sudan and is also produced in other African countries. It has long been used in various industries. However, its utilization is very limited in the construction sector although there appears to be a significant potential for use of AGB in the building industry. As an example, there is evidence that AGB may be an effective additive to concrete mixes that would improve fresh and hardened concrete properties. The aim of the present work is to provide further experimental evidence on the improvement that can be achieved in the physical and mechanical properties of hardened concrete when AGB is added to the mixture. The experimental results show a significant reduction in permeability for an optimum percentage of AGB and an increase in flexural and tensile strength and in the elastic modulus.

Effect of Web Holes and Bearing Stiffeners on Flexural-Shear Interaction Strength of Steel Cold-Formed C-Channel Sections

This paper presents an investigation on interaction equation between the required flexural strength, M, and the required shear strength, V, of cold-formed C-channels with web holes and bearing stiffeners. The primarily shear condition test was employed to study total 8 back to back lipped C channel sections of 95 and 100 mm depth when bearing stiffeners and circular holes were placed at center and both ends of specimens. The interaction equation were evaluated via Direct Strength Method, DSM, in accordance with the American Iron and Steel Institute for the design of cold-formed steel structural members, AISI 2007. A nonlinear finite element model was developed and verified against the test results in terms of failure buckling modes. It was concluded that the M-V interaction equation for specimens with web stiffeners was conservative where these specimens experienced plastic failure mode rather than local (Msl) or distortional (Msd) buckling mode. Moreover, the results indicated that proposed M-V interaction equation calculated by local buckling strength (Msl) adequately predicted the behavior of specimens with circular web holes.

Numerical Study on the Structural Performance of Steel Beams with Slant End-plate Connections

Thermal effects can be one of the most harmful conditions that any steel structure should expect throughout its service life. To counteract this effect, a new beam, with a capability to dissipate thermally induced axial force by slanting of end-plate connection at both ends, is proposed. The beam was examined in terms of its elastic mechanical behavior under symmetric transverse load in presence of an elevated temperature by means of direct stiffness finite element model. The performance of such connection is defined under two resisting mechanisms; by friction force dissipation between faces of slant connection and by small upward crawling on slant plane. The presented numerical method is relatively easy and useful to evaluate the behavior of the proposed beam of various dimensions at different temperatures. Its applicability is evident through satisfactory results verification with those from experimental, analytical and commercially available finite element software. Based on the good agreement between theoretical and experimental methods, a series of design curves were developed as a safe-practical range for the slant end-plate connections which are depend on the conditions of the connection.