Date of Award
5-28-2025
Publication Type
Dissertation
Degree Name
Ph.D.
Department
Civil and Environmental Engineering
Keywords
Steel modular construction, Finite element analysis; Axial Compressive Bundled Column; Z Block connectors; Connection performance
Supervisor
Sreekanta Das
Rights
info:eu-repo/semantics/embargoedAccess
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Abstract
Steel modular construction has emerged as an efficient alternative to conventional building methods, offering enhanced speed, cost-effectiveness, and sustainability. A critical aspect of this construction approach is the connection between modular units, which significantly influences structural integrity and load transfer efficiency. The Z Block connector, designed for inter-modular and intra-modular connections in steel modular buildings, plays a vital role in ensuring stability. However, standardized design guidelines for the pretensioning of ASTM A574 bolts, which are essential for mitigating separation between connected modules, are currently unavailable. This study aims to develop pretension guidelines, evaluate the effects of pretensioning on connection performance, and analyze the structural response of Z Block connectors under varying loading conditions. The first phase of this research focuses on developing pretensioning guidelines for ASTM A574 bolts used in Z Block connectors. Experimental studies involving Skidmore and Z Block tests were conducted to establish pretension equations for both the calibrated wrench method and the turn-of-nut method. These guidelines were validated through full-scale column-to-column connection tests, demonstrating a 39% reduction in separation when pretension was applied, with a negligible 0.4% decrease in maximum tensile load capacity. The second phase investigates the effect of different bolt pretension levels (30, 50, 61.5, 65, 70, and 85 kips) on column-to-column connections subjected to axial tensile loading. Six full-scale specimens were tested, and results indicated a reduction in block separation with increasing pretension levels, albeit with a minor decrease in tensile capacity. The optimal pretension level was determined to be 61.5 kips, which yielded an 82% reduction in separation relative to non-pretensioned specimens. Finite element analysis (FEA) was subsequently performed to validate experimental observations and explore alternative design pretension levels. The third phase of this study examines the compressive behavior of Z Block modular connections. Previous research focused on axial compressive loading for single-column configurations with different boundary conditions; however, this study expands the scope by evaluating three distinct column configurations: Axial Compressive Single Column (ACSC), Axial Compressive Bundled Column (ACBC), and Axial Compressive Single Column–Bundled Column (ACSC-BC). Experimental tests and numerical modeling were conducted to assess load-displacement characteristics, failure mechanisms, and structural integrity. Results indicated that the predominant failure mode was buckling of the Hollow Structural Steel (HSS) members, while the Z Block connectors sustained the applied loads without structural compromise. The final phase investigates the shear behavior of Z Block connections under three different configurations: Lateral Shear (LS), Lateral Shear-Registration Pin (LS-RP), and Lateral Shear-Pretension (LS-PT). Experimental analysis revealed a 46% reduction in shear capacity between LS and LS-RP specimens, highlighting the critical role of SHCSs in shear resistance. Furthermore, a comparative analysis of non-pretensioned (LS) and pretensioned (LS-PT) specimens showed a marginal 3% reduction in shear capacity. Load-displacement curves were analyzed, confirming that the primary failure mode was rupture of the SHCSs and/or the registration pin within the Z Block connector. This study provides an in-depth evaluation of the structural performance of Z Block connectors under different loading conditions. The findings contribute to the development of standardized pretension guidelines and optimized design recommendations, thereby enhancing the reliability and structural efficiency of modular steel construction.
Recommended Citation
Giwa, Ayotunde Chris, "Structural Performance of the Z Block Modular Connector Under Various Loadings" (2025). Electronic Theses and Dissertations. 9744.
https://scholar.uwindsor.ca/etd/9744