Local bond slip behavior of steel reinforcing bars embedded in ultra high performance fibre reinforced concrete

An experimental program concerning 48 specimens of grouted sleeve splices, first heated up to 600°C and then subjected to cyclic loading was presented and discussed in this study. Similar rebar splices were often used in the precast concrete structures designed for seismic regions. The temperature of the splice and the compressive strength of the grout were the main variables considered in this study. It is found that the temperature mainly affected the peak bearing capacity of the grout and the failure pattern of the connection. In fact, the typical failure pattern at room temperature (rebar fracture outside the sleeve) turned to rebar pullout of the sleeve above 400°C, which indicated that below this temperature grout‐to‐rebar bond kept most of its original efficacy. On the contrary, bond failure occurred for all specimens at 600°C because of rebar slip. A calculation method was proposed as well to evaluate the peak bearing capacity of grouted sleeve splice, based on the load transferring mechanisms of the bond between grout‐to‐rebar and sleeve‐to‐grout. The conducted experimental study and analysis provide a better understanding on the bond mechanism of thermally damaged grouted sleeve splices subjected to cyclic loading.

Section: Discussionmentioning

confidence: 99%

Experimental study on mechanical behavior of thermally damaged grouted sleeve splice under cyclic loading

Liu

Ding

Xie

2020

“…Theoretically, the addition of steel fibers can increase the reinforcement ratio of the longitudinal rebar (ρ te ) in the tension zone. 33,34 Additionally, the mechanical interlocking strength between aggregates and rebars is higher in the vicinity of the cracks, while the chemical adhesive strength is higher beyond the cracks. RPC does not contain coarse aggregate, the interlocking between the rugged surface of rebars and RPC is strong, and the equivalent diameter of the rebar in RPC is similar to that in NSC.…”

Section: Cracking Patterns and Failure Modesmentioning

confidence: 99%

Factors governing the fire response of prestressed reactive powder concrete beams

Yan

Yang

Doh

et al. 2020

This paper presents the details of fire test on eight prestressed reactive powder concrete (RPC) beams cured with 150°C hot-air condition. The test specimens were varied in load ratios/degree, cover thicknesses of tendons, bonded and unbonded tendons, partial prestressing ratios. The thermal fields, deflections behaviour, effective prestress, fire endurance, failure modes, and crack patterns of the beams were observed and recorded during the tests. The post-fire tests observation reveals that no obvious thermal-induced spalling occurred on the prestressed RPC beams prepared in hot-air curing. The fire tests results indicated that the failure of prestressed RPC beams was driven by direct fire exposure and fracture of tendons and longitudinal rebars after generation of wide cracks in the beams. In extreme fire, prestressed RPC beams that are under-reinforced at ambient temperature may fail as the low-reinforced beams. The load ratios and cover thicknesses of tendons are the key factors affecting the fire resistance of the prestressed RPC beams. With the decrease of the load ratios and increase of cover thicknesses of tendons, the fire resistance is dramatically improved. Bonded prestressed RPC beams showed superior performance to equivalent unbonded prestressed RPC beams in fire. The whole scale transferring effect of prestress loss in unbonded beams should be considered for fire resistance performance design based on structural systems.

“…In order to improve the mechanical performance of concrete structures, adding fiber into the concrete is an important method, in particular, high‐strength concrete and ultra‐high‐strength concrete need to improve their characteristics of brittleness and shrinkage cracking …”

Section: Introductionmentioning

confidence: 99%

Mechanical properties of jute fiber‐reinforced high‐strength concrete

Zhang

Yong

Gong

et al. 2019

High-strength concrete often suffers from brittleness, so the addition of fibers is an effective way to improve its performance. In this study, jute plant fiber was added to high-strength concrete, and the application method, content, and influence on the mechanical properties were explored. An orthogonal test was used alongside physical and mechanical analyses to test the compressive and tensile strength of 28-day-old jute fiber-reinforced concrete specimens, and the optimum length and content ratio of jute fiber were determined. By comparing and analyzing the mechanical properties of C60 concrete with and without jute fiber, it was found that the jute fiber gave obvious improvements to the tensile-compression ratio. By using scanning electron microscopy, the distribution of jute fibers in concrete and the reinforcement mechanism were analyzed. The strengthening, toughening, and cracking resistance effects of jute fibers in high-strength concrete were revealed from a microscopic point of view. This study provides a reference and basis for the study of high-strength concrete using environmentally friendly plant fiber. K E Y W O R D Sfiber pretreatment, jute fiber-reinforced concrete, mechanical properties, microscopic analysis