Existing structures built from the available materials such as: Timber, masonry, concrete, and steel suffered from number of problems which necessitate the need for new materials. These problems are heavy weight, corrosion, degradation and other aging problems. These problems not only affect the normal use function and service life of the structure, and the maintenance costs, but also cause a large number of safety and accident risks. All of these problems led researches to pursue new construction materials with high performance, such as fibre reinforced polymer (FRP) composite materials. FRP characterized by its light weight, corrosion resistance, and high strength. Because of the ability of FRP to withstand difficult environments, it is used in marine environments and chemical industries where corrosion is the biggest problem of steel causing a high maintenance cost. In addition, FRP used a lot in strengthening structures elements such as beam, column, and bridge’s decks, where the first time to use FRP in strengthening was in 1980 for strength concrete structures using Glass or Carbon FRP sheets. Besides the aforementioned applications, the application of FRP profiles has been received increasingly attention by the engineering community.
Light weight, fast and easy installation, offer stiffness to a structure, and carry heavy loads, these are what distinguishes trusses over solid web members, making it a renowned structure in the 19th century. Trusses used a lot in bridges, house roofs, towers, garages, and factories. These trusses can benefit from the advantages of the unidirectional properties of the FRP profiles as trusses carry only axial loads, making it the best choice for trusses. Therefore, trusses fully constructed by FRP profiles can reach a high performance, lighter weight, and high corrosion resistance compared to the steel, and satisfying the requirement of load capacity.
The structure capacity restricted by its connections’ capacity, hence the full understanding of the connection behaviour in Fiber-reinforced polymer is very important. The mid of 1960 in the US was the beginning of examinations on FRP connections’ properties especially bolted connections, as it required specific or appropriate design method specially in aerospace industry. The capacity and the strength of the FRP connections affected by a lot of variables such as material properties, connected type, and the geometric configuration.The well-known advantages of the FRP composites promote it to replace the steel connections (plates and bolts).
An experimental study for 114 specimens was conducted to study the behaviour of double shear lap, multi-bolted connections fabricated completely from Basalt fibre-reinforced polymer (BFRP) composite material (i.e., BFRP plates and bolts). Furthermore, this research investigates the effect of several parameters such as number of bolts (4, 6, 8, and 10), bolt type (SS, BFRP, and HSFRP), bolt arrangement, bolt diameter (6, 8, and 12 mm), hole patterns, the connection techniques (bonded, bolted, bonded-bolted, injected), and effect of external BFRP layer on the behaviour of BFRP connections.
The results showed that BFRP bolts can replaced the steel bolts without affect the load capacity and failure modes. For hybrid bolts it showed lower ultimate load, however it showed more ductile behaviour after the ultimate load.In addition to the static load, 41 BFRP specimens were tested under constant amplitude fatigue load with different bolts type (stainless-steel, BFRP, hybrid bolts) and different connection techniques (bolted, bonded-bolted, injected bolts) using BFRP bolts. The maximum fatigue load varied from 30 to 80% of the static ultimate load. The results showed that hybrid bolts had much high fatigue life than steel and BFRP bolted specimens.