An-Najah Staff

This paper focuses on analysis of two-way ribbed and waffle slabs with hidden beams. There are many methods that are used to analyze two-way slabs and the precision of these methods vary depending on method assumptions. In this study, the ACI direct design method is used as a manual or hand method of calculation and the solution will be compared with the analysis results of the three dimensional structural model done by the computer program Sap2000. The moments in beams, slab column strip and slab middle strip will be determined. It will be illustrated that the distribution of moments in two-way slabs with hidden beams likes the distribution of moments in slabs without beams as the stiffness of the hidden beams is small. It is recommended that the use of three dimensional modeling by computer software is the best solution for moment’s determination and distribution. 

At room temperature, and at service load levels, creep has little effect on the performance of steel structures. However, under fire conditions, creep becomes a dominant factor and influences fire resistance of steel members. Under fire conditions, significant forces develop in restrained steel beams and these forces induce high stresses in the steel section. The extent of creep deformations is affected by magnitude and rate of development of stress and temperature in steel. In this paper, the effect of high temperature creep on fire response of restrained beams is investigated. Current high temperature creep models are compared. Finite element model created in ANSYS was validated by comparing the predictions with fire test data. The validated model was applied to investigate the effect of load level, heating rate, fire scenario and fire induced axial restraint on the extent of creep deformations. Results from the parametric study indicate that the influence of high temperature creep increases with the increase in axial restraint, heating rate, and load level. Generally, neglecting high-temperature creep effect stiffens the structural response and leads to reduced deflections but larger restraint forces. Therefore, neglecting high temperature creep in fire resistance analysis of steel structures can lead to unconservative predictions.

In this paper the amplification factors of an Euler-Bernoulli beam with different boundary conditions due to a moving constant load are studied. The boundary conditions considered are: pinned-pinned, fixed-fixed, pinned-fixed, and fixed-free. The effects of the beam damping and the direction of motion of the moving loads are investigated. The obtained amplification factors are given in graphical form dependent on a moving speed parameter. Also, in addition to the amplification factors of the total response of the considered beams, the amplification factors of the forced response are separately considered. The present results are compared with published results where applicable.