Jiuqing Wang

The upgrade of the Beijing Electron Positron Collider, BEPCII, is now in a good performance for both high energy physics and synchrotron radiation experiments. The luminosity at the design energy of 1.89 GeV reached the design value 1.0*10³³/cm²/s¹ recently. A lot of work, including accelerator physics study and technical progress, has been done for the luminosity enhancement, not only at the design energy, but all the energy region run for HEP experiments from 1.0 to 2.3 GeV. The performance of BEPCII and the process of luminosity enhancement will be described in detail.

The High Energy Photon Source (HEPS), a 6 GeV green-field diffraction-limited storage ring light source, will be built in Beijing, China. The HEPS design has been evolving for about ten years, and is now mostly finished and ready for construction. The storage ring is based on a modified hybrid seven-bend achromat (7BA) design, where bending magnets with reverse bending angles and longitudinal gradients are adopted to reach an ultralow natural emittance of 34.2 pm with a circumference of 1360.4 m. The central slice of the dipole in the middle of the modified hybrid 7BA, with flexible magnetic field, is used as the source of the bending-magnet beamline. Moreover, alternating high- and low-beta sections are specially designed to generate and deliver X-ray synchrotron radiation with high brightness of 5 × 10 22 photons s −1 mm −2 mrad −2 (0.1% bandwidth) −1 . Here, the HEPS storage ring design and solutions to the challenges inherent in this ultralow-emittance design are presented.

In this article, the static shear behavior of large-headed studs embedded in ultra-high-performance concrete was investigated by push-out test and numerical analysis. A total of nine push-out specimens with single and grouped studs embedded in ultra-high-performance concrete and normal strength concrete slabs were tested. In the testing process, only shank failure appeared without cracks occurring on the surface of ultra-high-performance concrete slab when the steel–ultra-high-performance concrete specimens reached ultimate shear capacity. The shear capacity of specimens with large studs embedded in ultra-high-performance concrete slab increased by 10.6% compared those in normal concrete, and the current design codes such as Eurocode4, AASHTO LFRD 2014, and GB50017-2003 all underestimate the shear capacity of such kind of steel–ultra-high-performance concrete composite structures according to experimental results. Numerical models were established using ABAQUS with introducing damage plasticity material model. The influence of stud diameter, concrete strength, thickness of clear cover, and spacing of studs on the static shear behavior was thoroughly investigated via parametric analysis. Based on the experimental and numerical analysis, the existence of wedge block and the decrease of axis force are beneficial for improving the shear capacity of stud shear connectors.