Shear key is commonly used to connect two separate precast components in order to increase the interfacial shear resistance of the joint. The small dimensions of the shear key do not permit providing conventional reinforcement; consequently its ability to transmit shear force is mainly dependent on the mechanical properties of the used concrete. The enhanced shear capacity arising from using high strength concrete is always on the expense of the developed ductility. This paper presents an experimental and analytical investigation on the strength of the shear key connection in precast concrete construction that made of Strain Hardening Cementitious Composites (SHCCs). Thus, using of SHCCs, with their superior tensile strength and ductile behavior, in the shear key zone, not only improve both joint strength and ductility but also, control the cracks propagation as well. The shear keys test specimens were selected in the form of trapezium that is made up with 3 different key's angles. The main parameters for tests were the inclination angle of the shear key and the level of the confining stress. All specimens are tested using the -push-off‖ method in order to obtain the ultimate shear capacity of the connection. Accordingly, the overall shear behavior including ultimate shear resistance, crack pattern and modes of failure of the joints and the manifested slip were investigated. It was found that all tested specimens experienced shearing failure. However, SHCC shear keys are found to have more ductile mode of failure compared with that exhibited by normal strength concrete (NSC) specimen. It could be concluded that the use of SHCC significantly improves both the shear strength and the corresponding ductility of the joint. Based on the experimental results a simple analytical model is proposed for estimating the ultimate shear capacity of SHCC dry joint. The proposed analytical model showed good agreement with the experimental findings.

Currently, segmental box girder bridges with external prestressing is widely used in construction all over the world. This paper presents experimental test results on five specimens represents a box girder bridges with external prestressing taken with one-tenth scale. The specimens were simulated to the internal negative moment zone bounded by contra flexure point as cantilever specimen. All specimens are segmental beams with dry-keyed joints and they were tested under; bending, shear and torsion. Applied load eccentricity which causing torsion variation and tendon prestressing force level are the two main studied parameters. The behavior of the beams was evaluated in terms of; load open critical joint, cracking load, ultimate load, deformations such as deflections, twist angle and joints opening width as well as, strains of external tendons and internal steel. Also, behavior of the specimen including modes of failure, cracks propagation history and some critical values are also discussed. Some important remarks also are presented. The experimental results showed that, the existing of torsion has significant effect on the beams cracking behavior, deformed shape, mode of failure, and has slight effect on increasing the prestressing tendon stress at eccentric applied load side more than the side far from the applied load. Also, increasing effective prestressing force level has a significant effect to delay cracking due to shear stresses, and improve the beam deformation against flexure and torsion. Also, it has slight effect to reduce the difference between tendon stress at every side.

Analysis of Externally Prestressed Segmental Bridges (EPSBs) still needs more effort. At an earlier stage, an experimental investigation was carried out by the authors. The experimental investigation was consisted of ten specimens having different joint configurations, and it was divided into two phases. The first phase contains five specimens constructed with multiple small-amplitude shear keys in accordance with AASHTO. The parameters selected for the first phase were different levels of prestressing force in tendons as well as different levels of applied torsion. The second phase contained four segmental specimens and a monolithic one. The joints in the second phase took four forms: multiple small-amplitude shear keys, large-reinforced shear key, steel shear connectors, and UHP-SHCC joint connecting the tension flange. This paper proposed an analytical procedure to calculate the full prestressing load and partial prestressing load based on the forces' equilibrium. Skew Bending Model that inspected by Huan and Liu, 2006, to calculate the load-carrying capacity for segmental beams with internal unbonded tendons subjected to combined bending, shear, and torsion modified to calculate the ultimate capacity of EPSBs and gave satisfactory agreement with the experimental results.

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Reinforced concrete buildings are frequently exposed to seismic loadings. This condition generates either uniaxial or biaxial unbalanced moment on slab-to-column connections. The design of such connections varies greatly between most international codes. This paper investigates the effect of the unbalanced moment on the punching shear strength of two-way interior slab-to-column connections. For this purpose, a nonlinear finite element analysis using ANSYS-V19.2 software package was performed. Thirteen High-Performance Concrete (HPC) slabs with different eccentricities were analyzed. During this context, a number of three large scale specimens made of HPC were firstly tested experimentally to validate the used model.The interaction diagram between the unbalanced moment and the punching shear strength was developed and then compared against those resulted by different international codes (ACI 318-19, CSA A23.3-04, EC2-04, BS8110-97, and ECP 203-2018). The results showed that by increasing the unbalanced moment, the punching shear strength is significantly decreased and the failed surface from the column face is pulled toward the column. Moreover, the normalized moment-shear relationship showed a linear interaction diagram.