# A Review on Design Considerations and Connection Techniques in Modular Composite Construction
## 3 Area of Research
### Connections in Modular Construction Scenario
Notably, grouted couplers gain advantages from mechanical interlocking and grout confinement, which enhance the transfer of axial and shear forces. Connections employing embedded steel plates and bolts received slightly lower scores due to the inherent risk of slipping at the interface, potentially causing stress concentrations at the bolt locations. Research findings [64; 65; 66] regarding bolted connections in precast frameworks suggest that, while they exhibit adequate load-bearing capacity, their performance in response to significant cyclic loads is contingent upon factors such as bolt pre-tensioning and slip behaviour. The seismic performance of connections is intricately linked to their ductility, energy dissipation capabilities, and adaptability to cyclic deformations. Connections made with cast in situ techniques exhibited the highest levels of seismic resilience, functioning monolithically and providing enhanced ductility. Grouted coupler connections also performed admirably, especially when designed with confinement reinforcement, as experimental investigations into precast beam-column joints have demonstrated their effective energy dissipation capabilities. Connections featuring embedded steel plates and bolts displayed moderate seismic performance, as their inherent dry assembly characteristics may result in localised stress concentrations, thereby diminishing overall ductility. Nevertheless, bolted systems can be engineered with energy-dissipating elements to improve their seismic performance. The durability evaluation focused on the material's performance as time progressed and its resistance to external influences. Connections utilising cast in situ and grouted coupler methods received the highest durability ratings, as their concrete-embedded designs significantly reduced exposure to external degradation agents. Conversely, embedded steel plates and bolted connections scored lower due to potential corrosion hazards, necessitating protective coatings and routine inspections. Longitudinal studies on exposed bolted joints within precast bridges and industrial facilities have revealed an increased vulnerability to moisture infiltration and rust, which, if not addressed, could culminate in connection failure. Cost considerations are paramount in modular construction, where efficiency and economic viability are critical factors. Connections made with cast in situ methods were assigned the lowest score, as they typically entail considerable on-site labour, extensive formwork, and prolonged curing periods. In contrast, grouted couplers and embedded steel plates and bolted connections received higher ratings due to their facilitation of quicker installations with diminished labour expenses. The grouted coupler system achieves a harmonious balance between cost efficiency and performance, rendering it a financially viable option for modular construction, particularly as the repetitive use of connection elements further optimises overall costs. Construction speed was significantly affected by the requirements of on-site operations. Embedded steel plates and bolted connections received the highest ranking, as they offer immediate structural stability upon installation, thereby reducing on-site labour. Grouted coupler connections were rated lower due to their need for precise alignment while permitting rapid post-grouting assembly. Conversely, cast in situ connections scored the lowest, attributable to extended curing durations and the demand for supplementary site activities. The evaluation of installation ease was determined by the feasibility of managing 10- to 15-tonne concrete modules within modular construction. Grouted coupler connections achieved the highest rank, enabling straightforward alignment and joining with minimal equipment, thereby diminishing installation time and intricacy. Following were embedded steel plates and bolted connections, necessitating careful bolt tightening but eliminating the need for wet processes.