## 1 Introduction  
Beam-column end-plate connection is an important connection form for prefabricated steel structures. For many years, scholars have conducted significant experimental research on this connection form and obtained many interesting results [1; 2; 3]. The scale model test is an important type of node test. Under conditions of similar error control, good empirical results can be obtained. At the same time, compared with full-scale model tests, it can save considerable test expenses, site occupation, and time costs. However, due to the lack of effective communication and unified organization, each researcher only focuses on his own research content and rarely analyzes the similar errors of the trial itself, which results in unevenness in the trial results and a waste of experimental resources. Due to this situation, it is urgent to analyze incomplete similar factors in the scale model test for the beam-column end-plate connections and solve the bottlenecks caused by the scale model test.  
In view of the performance characteristics of common semi-rigid connections of steel structures, including beam-column end-plate connections, scholars from various countries have performed many experiments and theoretical studies. [PERSON] et al. completed the failure tests of six full-scale beam-column connections under low-cycle repeated loads and compared and analyzed the deformation distribution, hysteresis curve, energy consumption, and failure phenomenon of each specimen [4]. To study the low-cycle fatigue fracture performance of high-strength steel joints under strong earthquakes, [PERSON] et al. completed the pseudo-static loading test of four full-scale test specimens of bolt-welded hybrid beam-column joints of high-strength steel frames, the bearing performance, and failure mode of each specimen [5]. [PERSON] et al. designed a scale model with a similar ratio of 1:4 for a complex steel joint, conducted a monotonic static loading test, studied the test phenomenon, measured the strain and failure mode, and obtained weak parts of the joint [6]. Based on these results, they developed a model test design method for complex nodes. [PERSON] et al. took the T-stub as the research object, assumed the flange of the T-stub as a simply supported beam, established the initial rotational stiffness calculation model of the T-stub in the elastic stage, derived the calculation formula of the initial rotational stiffness, and verified the formula using numerical simulation and experimental data [7].  
It can be seen that in the research process of many scholars, the impact of similar errors on the test results is rarely separately considered. The known research on similarities is insufficient and isolated [8; 9; 10]. Therefore, to study the mechanism of similar error formation of semi-rigid nodes, this paper derives the conditions of complete similarity of semi-rigid nodes based on similarity theory. From the perspective of end-plate thickness, the influence of similar factors was analyzed, and the corresponding influence laws were obtained. Accurate finite element models were established, and a linear regression analysis was performed to predict similar errors of semi-rigid connections.