principal load meaning in English

知荷载
主要荷载

In this paper , the general situations of the model tests are outlined in brief , the spatial plate and shell finite element model is established to theoretically analyze the model bridge for the tests , the measurements of the tests under principal load cases are provided and corresponding proposals to the design and construction are made as well
简要介绍模型试验研究情况，建立空间板壳有限元模型对该模型桥梁进行理论分析，给出主要试验工况的实测数据，提出设计施工建议。