Effect of transverse shear in reinforced concrete slab on wide flange t-beam
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Date
2018
Authors
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Journal ISSN
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Publisher
Universiti Teknologi Malaysia
Abstract
The combination of precast pre-stressed concrete girder and in-situ reinforced concrete slab is the most popular system used in the construction of short to medium span bridge deck in Malaysia. Wide flange T-section is among the popular choice of pre-stressed girder. The slab is usually designed as a continuous one-way slab spanning in the transverse direction of the bridge. However, the stiffness and geometry of the girder flanges and its web thickness are usually neglected in the slab analysis and design. This assumption results in the provision of excessive transverse steel reinforcements in the slab’. The objective of this research is to investigate the effect of flanges and web thickness, and the shear stud of wide flange T-section girder on the load bearing capacity of the slab in the transverse direction of the bridge. The finding is then used to derive an economical equation to predict the load carrying capacity of the bridge deck slab supported by the wide flange T-section girders. The study comprises three components: case-study on existing bridges, experimental work and nonlinear finite element analysis. In the case-study, the slabs of twelve existing bridges constructed in different places in Malaysia are analysed as continuous slab assumption, and by using solid model finite element which incorporates the flanges and webs of T-section girders. Results of both analyses are used to design the slab reinforcements and compared with the construction details. The experimental work consists of full-scale tests of one meter long specimens. The specimens are built according to the geometry and reinforcement detail of one of the existing bridges. The pre-stressed tendon in the girder is neglected. The girders are placed at three different spacings. The slab on top of the beam is 200 mm thick containing only minimum steel reinforcement of T12 at 300mm spacing that meets the requirement for controlling thermal and shrinkage cracking. From the analysis and design of the case-study bridges, it is found that the flanges of T-section girders increase the load carrying capacities of the slabs significantly i.e. the minimum amount of steel reinforcement in the deck slab is sufficient to carry the vehicle wheel loads as specified in Eurocode vehicle load specification. This finding is verified by the experiment results. The load carrying capacities of the slabs obtained from the test for specimens with the T-section flange gaps of 50 mm, 200 mm and 500 mm are seven, six and five times greater than the Eurocode largest tandem point loading of 150 kN per wheel respectively. This indicates that the lightly reinforced concrete slab deck on the pre-stressed wide flange T-section girders is sufficient in carrying vehicle load. The results of parametric study using non-linear finite element analysis also show that the stiffness of lightly reinforced slab in the transverse direction is directly proportional to its thickness and to the amount of girder shear connectors, but inversely proportional to the gaps between the adjacent flanges. The empirical relation derived from the results of parametric study for predicting the ultimate load carrying capacity of the slab considering the girder flanges, web thickness and shear stud produces satisfactory results when compared with the experimental data.
Description
Thesis (PhD. (Civil Engineering))
Keywords
Concrete slabs—Design and construction, Bridges—Bearings—Testing, Prestressed concrete beams—Design and construction