# Experimental and Parametric Analysis of Pull-Out Resistance of Notched T-Perfobond Connectors
## 1 Introduction  
As pivotal interfacing elements in composite structures, perfobond connectors have been widely utilized in various structural systems, such as composite beams, hybrid beams, composite towers, bridge decks, and composite anchorages [1; 2; 3; 4], due to their outstanding shear resistance and fatigue resistance, as well as ease of installation. In recent years, extensive research has been conducted on perfobond connectors, employing a variety of methodologies. Physical modeling, the first of these methodologies, involves the creation of scaled or full-sized replicas of the connectors and the structures they are a part of. In particular, push-in, push-out, and pull-out model tests are usually used to obtain the shear and tensile behavior of perfobond connectors [5; 6; 7; 8; 9; 10]. This hands-on approach allows researchers to observe, firsthand, the mechanical interactions that occur under real-world conditions, such as the distribution of forces and the development of stresses within the composite system. Physical models are particularly useful for studying complex interactions that cannot be fully captured by computational methods alone. The second methodology is computational simulation, which leverages advanced software tools, such as ABAQUS ([https://www.3 ds.com/products/simulia/abaqus](https://www.3 ds.com/products/simulia/abaqus) accessed date 10 August 2024) and ANSYS ([[https://www.ansys.com/](https://www.ansys.com/)]([https://www.ansys.com/](https://www.ansys.com/)) accessed date 10 August 2024), to create virtual models of perfobond connectors and the composite structures they are used in [11; 12; 13; 14; 15; 16]. These simulations can account for a wide range of variables, includingmaterial properties, loading conditions, and environmental factors. By simulating various scenarios, researchers can predict the behavior of perfobond connectors under different circumstances, which is invaluable for optimizing their design and application. Theoretical analysis, the third methodology, involves the development of mathematical models to describe the behavior of perfobond connectors [17; 18; 19; 20; 21; 22]. This approach is based on established principles of mechanics and materials science and can provide deep insights into the fundamental mechanisms at play. Theoretical models can be used to derive equations that predict shear performance and pull-out characteristics, offering a basis for the design and evaluation of perfobond connectors. Substantial research has been devoted to the fundamental mechanical attributes of perfobond connectors within conventional concrete slabs, yet some knowledge deficits persist [23; 24; 25]. For example, specific composite structures such as ultra-thin bridge decks possess an exceptionally thin concrete layer, raising the slab's out-of-plane uplift resistance to a critical concern. Nevertheless, current literature mainly focuses on shear performance, frequently neglecting pull-out behavior. Moreover, the insertion of steel bars to enhance connector performance is highly advantageous, but the closed circular holes of conventional perfobond connectors impede this procedure, necessitating the exploration of the mechanics of notched perfobond connectors. Enlarging the notch to align with the hole size might compromise the pull-out capacity, resulting in our proposal to incorporate a flange into the design of the notched perfobond connector. In addition, although thin concrete components are prone to tensile cracking, the utilization of ultra-high-performance concrete (UHPC) could significantly enhance crack resistance. In spite of this, there is a marked scarcity of studies investigating the mechanical properties of perfobond connectors in UHPC settings. Our research presents a novel notched T-perfobond connector devised to surmount the obstacles of insufficient pull-out bearing capacity in shallow-embedded multi-row connectors and the difficulty of steel bar penetration.