Analyzing the Nonlinear Dynamics of the Three Degree of Freedom Frame Structure Based on the NewMark-β Method and the Effect of Stiffness on the Displacement of the Structure. jcer [Internet]. 2024 Sep. 1 [cited 2025 Sep. 5];6(3):9-17. Available from: http://www.journals-researchers.com/ojs/index.php/jcer/article/view/134