Fresh/Mechanical/Durability Properties and Structural Performance of Enginnered Cementitious Composite (ECC)

Engineered Cementitious Composite (ECC) is an ultra ductile concrete with strain-hardening and multiple-cracking behaviour in tension and flexure. Fresh, mechanical and durability properties of different ECC mixtures are evaluated by incorporating supplementary cementitious materials (class F, CI fly ash and slag) and different aggregate type. Experimental studies demonstrated viability of producing greener, sustainable and cost-effective ECC using locally available aggregates (crushed sand) instead of microsilica sand and fly ash (Class CI or F) of up to 70% cement replacement having similar or better fresh, mechanical and durability properties. Structural validation by small scale tests on bridge decks with ECC link slab and by push out tests to evaluate stud shear connector-ECC interaction compared with self-consolidating concrete (SCC) proved feasibility and advantages of these ECC mixes. Based on research, recommendations are made for ECC mix design and their application in link slab construction in bridge structures.

Fresh/Mechanical/Durability Properties and Structural Performance of Enginnered Cementitious Composite (ECC)

Engineered Cementitious Composite (ECC) is an ultra ductile concrete with strain-hardening and multiple-cracking behaviour in tension and flexure. Fresh, mechanical and durability properties of different ECC mixtures are evaluated by incorporating supplementary cementitious materials (class F, CI fly ash and slag) and different aggregate type. Experimental studies demonstrated viability of producing greener, sustainable and cost-effective ECC using locally available aggregates (crushed sand) instead of microsilica sand and fly ash (Class CI or F) of up to 70% cement replacement having similar or better fresh, mechanical and durability properties. Structural validation by small scale tests on bridge decks with ECC link slab and by push out tests to evaluate stud shear connector-ECC interaction compared with self-consolidating concrete (SCC) proved feasibility and advantages of these ECC mixes. Based on research, recommendations are made for ECC mix design and their application in link slab construction in bridge structures.

Experimental Investigation of Steel Confinement of Clustered Large-Size Stud Shear Connector in Full-Depth Precast Bridge Deck Panel

The research focuses on investigating different types of steel confinements around a clustered large-size stud shear connector using in full-depth precast concrete bridge deck panel. The tests were based on Push-off test of two main groups of specimens: (1) the specimens with 4-stud shear connector where three different types of confinement were adopted including of O-ring confinement, Wire-mesh confinement, and L-angle confinement), and (2) the specimens with 8-stud shear connector where two different types of confinement were investigated including of Plate-ring confinement and L-angle confinement. The test results concluded that L-angle confinement type of the group of specimens with 4-Stud is the most sufficient type comparing between the different types of confinement in the same group. The maximum resistance was found at 41-ton, while as the displacement was found to be the most expansible and gradually reduced until the failure point. This means that the sign of failure can be noticeable prior to a collapse of the structure. For the group of specimens with 8-Stud, the resistance of this group was higher than the group of specimens with 4-Stud about 50 - 100% increase depending on each type of confinement. The maximum resistance was found for Plate-ring confinement type at 70-ton, which was agreed with the increment of the displacement about 20 - 50%. In comparison between specimens with 8-Stud, the Plate-ring confinement showed greater resistance and more relative displacement about 15% than the L-angle confinement.

Static and Fatigue Behavior of Rubber-Sleeved Stud Shear Connectors as Part of Field-Cast Ultra-High Performance Concrete Connections

Field-cast ultra-high performance concrete (UHPC) connections are an innovative and prospective solution for combining full-depth precast concrete decks and steel girders. However, previous studies show that the slip capacity of stud shear connectors embedded in UHPC cannot meet the requirements for ductile connectors by Eurocode 4, which can reduce the resistance of steel and concrete composite members. In this study, the rubber-sleeved stud shear connector, which is a composite of ordinary stud and rubber sleeve, was adopted for the field-cast UHPC connections. Push-out tests were conducted to investigate the static and fatigue behavior of the rubber-sleeved stud shear connector as part of field-cast UHPC connections. Results of static tests showed that the rubber-sleeved stud shear connector has sufficient deformation capacity and its slip capacity is 1.5 times that of the ordinary stud shear connector. Compared to ordinary stud shear connectors, UHPC with high strength and stiffness has a relatively small effect on improving the shear strength and stiffness of rubber-sleeve stud shear connectors. Results of fatigue tests showed that the rubber-sleeved stud shear connector in UHPC has similar fatigue behavior to that in normal strength concrete. Though UHPC improves the restraint to the stud deformation, the influence of rubber sleeves is still decisive in determining the fatigue behavior of rubber-sleeve stud shear connectors. In addition, based on the results of strain gauges at stud roots, it was found that the crack initiation process consumes a small proportion of the fatigue life of rubber-sleeved stud shear connectors, which is about 5%.

Pengaruh Panjang dan Diameter Stud terhadap Keruntuhan Geser Struktur Komposit Baja-Beton

Composite structures of concrete slabs and steel beams require shear connectors to transfer shear force between steel beams and concrete slabs. The strength of stud shear connector specified on SNI 03-1729-2013 only considers the effect of stud diameter, however the length of a stud may influence its behavior and strength. This research observes the effects of length and diameter (𝓁/𝒹) of shear connectors on the strength. This research was conducted using the push out method explain in AS-4347- Part I. The test specimens observed in this research were concrete and steel composites, composing IWF 350x175x11x14 mm and concrete blocks of size 450x225x160 mm. The studs were made of steel reinforcements with diameter (𝒹) of 10, 16 and 22 mm, were welded on IWF with 5 mm weld thickness. The length of studs for each stud diameter were 4d, 5d, and 6d. The results indicate that the increase in stud diameter will increase the load capacity of stud. The length of studs effect its load capacity. A slim stud experiences large bending moment at the base of the shear connector. The results show that the highest value of load capacity is measured at specimens with 𝓁/𝒹 ratio of 5.

Comparative Study between Linear-Interpolation and Stress-Block Methods of Composite Design Using Cold-Formed Steel Section

For decades, Hot Rolled Steel (HRS) section was in use in construction of buildings and bridges. The simple reason is that the use of HRS section in composite systems is well established by standard rules and their design necessities as provided in the codes. In this paper, the use of doubly oriented back-to-back Cold-Formed Steel (CFS) section coupled with bolted shear connectors in composite floor system was demonstrated. The bolted system of shear connector provides an alternative to headed stud shear connector with CFS section as welding of the stud connector is practically not feasible on CFS section because of its thinness nature. The loading system used was four-point bending test to determine the flexural strength capabilities of the composite floor system. The resulting composite floor system has proven to provide adequate strength and stiffness properties under the applied loads. The results have shown that the theoretical value of flexural capacities calculated agrees reasonably well with the experimental values. In conclusion, the composite floor system can be used in small and medium size buildings, as well as in light weight construction industries.