Shear-friction behavior of grooved construction joints between a precast UHPC girder and a cast-in-place concrete slab

This study examined the reliability and limitations of code equations for determining the shear friction strength of a concrete interface with construction joints. This was achieved by examining the code equations (ACI 318-14, AASHTO, and fib 2010) and comparing the results predicted by equations with experimental data compiled from 207 push-off specimens (133 rough and 74 smooth construction joints). The integrated mechanical model for the monolithic interface, derived from the upper-bound theorem of concrete plasticity, was also modified to estimate the shear friction strength of the construction joints. The upper limit for shear friction strength was formulated from a concrete crushing failure limit on the strut-and-tie action along the interfacial plane, to avoid overestimating the shear transfer capacity of transverse reinforcement with a high clamping force. Code equations are highly conservative and dispersive in predicting the shear friction strength of rough construction joints and yield large scattering in the data for the ratios between the measured and predicted shear friction strengths. The predictions obtained using the proposed model agreed well with test results, indicating correlating trends with the test results for evaluating the effects of various parameters on the shear friction strength of rough construction joints. According to the proposed model, the values of cohesion and coefficient of friction for concrete could be determined as 0.11 fc′0.65 and 0.64, respectively, for smooth construction joints and 0.27 fc′0.65 and 0.95, respectively, for rough construction joints, where fc′ is the compressive strength of concrete.

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Effect of Concrete Types and Construction Joints on Concrete Shear Friction Characteristics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.723.700 ◽

2016 ◽

Vol 723 ◽

pp. 700-705

Author(s):

Yong Ha Hwang ◽

Keun Hyeok Yang ◽

Jae Sung Mun ◽

Hyun Sub Yoon ◽

In Hyuk Hwang ◽

...

Keyword(s):

Normal Weight ◽

Unit Weight ◽

Friction Behavior ◽

Normal Weight Concrete ◽

Construction Joint ◽

Shear Friction ◽

Shear Cracking ◽

Concrete Joints ◽

Heavyweight Concrete ◽

Cracking Stress

The present study examined the effect of smooth construction joint and concrete unit weight on the shear friction behavior of concrete. From nine push-off test specimens, shear load-relative slip relationships, shear cracking stress, shear friction strength were measured. Test results showed that the shear cracking stress was hardly affected by the configuration of transverse reinforcement or concrete unit weight. The shear friction strength of monolithic normal-weight concrete was approximately three times higher than that of the companion specimens with construction joint. Meanwhile, the heavyweight concrete joints had a similar shear friction strength to normal-weight concrete ones.

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