# A Review on Design Considerations and Connection Techniques in Modular Composite Construction
## 2 Conceptual Background
### Comparison of Modular Construction with Other Precast Techniques  
Modular construction is distinguished by its unique benefits compared to other precast construction methodologies. Conventional precast systems often necessitate supplementary components for structural integration; however, modular construction generally incorporates these components within the modules [35]. This methodology significantly improves structural performance and simplifies construction, enhancing efficiency and effectiveness. Regarding seismic performance, precast concrete modules demonstrate greater resilience when compared to steel modules, rendering them especially beneficial in areas susceptible to substantial seismic events [36], such as New Zealand, Japan, and Chile, where the preservation of structural integrity is paramount. Considerations regarding weight also play a crucial role in distinguishing these systems. While precast concrete modules are typically heavier than their steel counterparts, which may present challenges during lifting operations for taller edifices, utilising specialised construction equipment can effectively address these hurdles [37]. Such machinery is engineered to accommodate the differences in weight, ensuring the successful execution of projects despite the added weight. Furthermore, modular construction exhibits heightened effectiveness in high-rise structures featuring multiple repeated units [37], though high-rise modular buildings remain comparatively uncommon. This scarcity can be attributed to a limited comprehension of their structural responses to lateral forces, such as seismic and wind loads, essential for guaranteeing safety and stability. A heatmap (Figure 5) visualisation is utilised, standardising the performance of Beam and Column, Wall and Slab, Volumetric Modular, and Conventional construction on a continuum from 1 (Low) to 4 (Very High) to provide a more precise comparison of these construction methodologies. The qualitative evaluations were established based on knowl \begin{table}
\begin{tabular}{c c c c c} \hline
**Level 0** & **Level 1** & **Level 2** & **Level 3** & **Level 4** \\ \hline Material & Component & Elemental or & Modular & Complete \\ System & System & Planar System & Volumetric & Building \\ \hline \end{tabular}
\end{table} 
Table 1: Levels of precast systems. edge gleaned from a comprehensive literature review, considering critical performance metrics: Precast Ratio, Cost, Robustness, Quality Control, Labour Efficiency, Environmental Impact, and Design Flexibility. The qualitative scoring is comprehensively synthesised from scholarly investigations, comparative studies, and practical applications [38; 39; 40; 41; 42; 43; 44]. For Precast Ratio, the score indicates the degree of precast component employment, with higher scores signifying a stronger dependence on precast techniques. Cost assessments considered material, labour, and transportation costs, where higher scores denote increased cost-effectiveness. Robustness evaluations concentrated on structural strength and longevity, granting higher scores to techniques exhibiting exceptional long-term performance. Quality Control ratings were based on the accuracy and consistency achieved in off-site production, with higher scores signifying superior quality management. Labour Efficiency ratings reflect the effectiveness of labour deployment, assigning higher scores to techniques that require less on-site labour. Environmental Impact ratings evaluated aspects such as material waste and energy use, with higher scores indicating maximum ecological footprint. Lastly, Design Flexibility assessed the adaptability of each construction technique to diverse architectural styles, with higher scores reflecting increased flexibility. The qualitative evaluations for each criterion were converted into quantitative scores on a scale of 1 to 4, ensuring uniformity and objectivity in comparing the various construction techniques.