Fig 9 - uploaded by Dina Mukheef Hamza
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Load-beam tip deflection for cases of construction joints. 0 10 20 30 40 50 60 Beam tip deflection (mm)
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This paper describes a comparison between beam-column junctions with and without construction joint, also, a parametric study deals with construction joint is presented by taking various conditions of the junction. These include the various positions of the construction joint, the axial load on the column, strength of concrete in the second cast an...
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Citations
... Hamza (2005) [4], studied the behaviour of beam-column joints with nonlinear interface elements. She assumed the interface as a thin brick element with Millard dowel forces. ...
... 3. A stiff response can be obtained with decrease the thickness of the interface element. 4. The response of a specimen can be expected within a certain range of thickness of the interface element. ...
To study the nonlinear response of corner beam-column junctions with inclusion of the effect of construction joint between the column and the beam cast at different times and subjected to cyclic and repeated loads, a computer program of three dimensional nonlinear finite element analysis, written by Al-Shaarbaf[1], (P3DNFEA)has been extended to account for the effect of construction joints on the behavior and to deal with concrete behavior under cyclic loads.
The 20-node isoperimetric brick elements have been used to model the concrete, while the reinforcing bars are modeled as axial members embedded within the brick elements. A nonlinear cyclic behavior model for concrete is developed in uniaxial and multiaxial states of stress. Also, a nonlinear cyclic behavior model for reinforcing bars is presented.
In completion, the behavior of concrete under cyclic loads is simulated by an elasto-plastic work hardening model followed by a perfectly plastic response. In tension, affixed smeared crack modeled has been used to simulate the behavior of concrete with a tension-stiffening model to represent the retained post-cracking tensile stresses in concrete. Closing and reopening of cracks during cyclic loading has been taken into consideration.
The nonlinear equations of equilibrium have been saved using an incremental-iterative technique based on the modified Newton-Raphson method. The convergence of the solution was controlled by a force convergence criterion. The numerical integration has been conducted by using 27-point Gaussian rule.
To represent the shear transfer between two concretes cast at different times, 20-noded interface layer brick elements are used with Fronteddu’s and Millard’s models to represent the aggregate interlock and the dowel stiffness, respectively.
Comparison between the results obtained from the finite elements and the available experimental results is made for a corner beam-column junction with inclusion of the effect of a construction joint. Good agreement is obtained. The maximum difference in ultimate load is 3.9%.
A parametric study dealing with construction joint is presented by taking various conditions of the junction. These include the axial load on the column, strength of concrete in the second cast.
... Therefore, in current research we will resolve the behavior of fresh and hardened HSC properties by adding (mixing) SM as admixtures and using it to casting beam in order to study the effect of it on the delay concreting process on horizontal and vertical construction joints. Extensive experimental and many theoretical studies have been performed to investigate the effect of construction joint on the behavior of structural element as examples; Husain and Hamza [13], Metwally and Issa [14], Abdul-Majeed [15], Abdul-Majeed et al. [16], Abass [17] and Ali and. Mahdi [18]; but those researchers focused on the cases when the first part of the casting concrete reaches to the final setting time (after one days or more). ...
The current research studies the effect of cold joints on the behavior shear and flexure of High Strength Concrete (HSC) beams caused by delayed casting sequence during the hot weather in summer of Iraq.Fresh concrete should be kept alive during the various casting batches for concrete element by re-vibration. However, the over vibration caused loss in homogeneity and it is difficult to keep the workability of concrete during hot weather due to the effect of setting time.To deal with this problem of improper casting sequence, which eventually leads to the formation of cold joints, it will be used sugar waste (named as Sugar Molasses (SM)) is a by-product resulted from refining process of sugar as a delayed agent to increase the setting time in order to prevent early set of concrete due to adverse effects in construction joint of hot weather.In the current study, the first objective aims to investigate some of fresh and hardened mechanical properties of HSC (with high cement content) using SM at percentages of (0, 0.05, 0.1, 0.2, 0.3) % from the weight of cement under the concept of sustainable development. The second objective aims to investigate the location and surface texture effect of horizontal and vertical cold joints on the flexural and shear behavior of beam with/without SM. This objective includes testing of twenty four plain concrete beam of (110×110×650 mm) under two point load; half of them casting without roughing (smooth) the old layer and the other casted after roughed it.SM content of 0.2% of cement weight can improve compressive strength by about 11.2% at 28 days and delay initial setting time by about 4.617 hours (277 minutes). No adverse effect on concrete have been observed at this dosage of SM concentration for the ages of concrete cylinders studied. Delays in the setting of concrete at this dosage of SM content help in reducing the early setting of concrete and therefore reduced the impact of the cold joints formation in concrete beams under Iraqi hot weather condition. The failure load for the beams with SM of smooth and rough vertical joints is in the range between (1.95 - 2.12) and (1.46-1.37); respectively times that of the case of beam without SM.
