The polymer composite known as Fibre Reinforced Polymer (FRP) has several advantages over conventional materials. It has been slowly incorporated into civil infrastructures, because the general regulations have not yet been officially introduced. Pultruded FRP manufactures have internal standards of organizations and Guidelines. Therefore, the design identifies issues that require clarification. This study presents influence of the reduced elasticity modulus on strength of pultruded FRP members in bending with a symmetrical cross-section. The position of the neutral line and calculation of strength and deflections with and without reduced modulus of elasticity are determined in the study. Comparison of the results of calculations showed that when taking into account the reduced modulus of elasticity, the deformability is reduced by up to 15 %. The significance of the results obtained for the construction industry consists in the possibility of a refined calculation of the flexural pultruded FRP members taking into account the reduced modulus of elasticity in order to effectively use the strength reserves and reducing material consumption.

Introduction. At present, design and construction of all-composite structures with the use of pultrusion fiberglass profiles (PFP) are developing. The bearing capacity of all-composite structures is often limited by their node connections. Over the last two decades, many studies have been devoted to the operation of fiber-reinforced polymer (FRP) element nodes connected at right angles (or in the direction of pultrusion and across it). Frame construction nodes are formed by adjoining frame elements at different angles to the bands through gusset sheets. In accordance with the literature analysis, a small number of tests have been carried out to investigate connections at angles to the pultrusion direction. Existing design solutions of gusset sheets in FRP frame structures are mainly made of steel or composite material produced using other technologies (compaction method, pressure treatment method). This study focuses on the implementation of a node connection on unidirectional gusset sheets in which the fibers are positioned at the angle of 0°. Taking into account the specific features of the material, the gusset sheet design in frame structures has been adapted to the properties of pultrusion fiberglass. The purpose of this study is to increase the efficiency of PFP gusset sheet use in frame structures based on the specifications of this material. Materials and methods. The adaptive method was used when designing the node connection design on the frame structure gusset sheets. The material of the trapezoidal steel truss is changed to the composite material while retaining the original design solution. Subsequently, the structure is upgraded to take into account the properties and features of the composite material. Results. The main results of the study involve determining the factor of safety of pultrusion fiberglass at different angles to the direction of force. In order to increase the bearing capacity of the element node connection, various gusset plate design solutions are provided, which take into account different forces in the frame structure elements. Conclusions. When designing PFP constructions, features of the material must be taken into account. Replacing traditional materials with composite without adjusting the design layout and upgrading the structure leads to increased material intensity.

The design experience shows that special attention should be paid to node connections of structural elements. The introduction of new node connections requires the development of methods for their calculation taking into account the properties, structure and behavior of materials under various loading conditions. Various studies are devoted to node connections of elements from pultruded GFRP at right angles. Analysis of the technical literature shows that compounds with forces acting at an angle are poorly studied and require additional numerical and experimental studies. The structural form adopted for the study is a frame structure elements of which are adjacent to the belts at various angles. The article considers various types of node connections of pultruded GFRP elements in a frame structure. When calculating the node connection of pultruded GFRP elements the following material features are taking into account: nonlinearity of elastic deformations, uniformity and characteristics of each component separately. The paper presents a comparison of calculations by domestic and foreign techniques. It is established that taking into account the material features leads to material savings, while providing the required strength and deformability

At present, design and construction of all-FRP structures with the use of GFRP are developing. All-FRP frame structures use bolted connections to form nodes between the elements, particularly steel bolts. This research focuses on the use of FRP pultruded plates instead of chords and webs. Frame construction nodes are formed by adjoining frame elements at different angles to the chords through gusset plates. In accordance with the literature analysis, a small number of tests have been carried out to investigate connections at angles to the pultrusion direction the pultrusion direction. Both experimental and numerical studies made with pultruded plates and L-shape FRP profiles have demonstrated that the plates have considerable influence on the strength and deformation of joints so that the joints failure mode involves mainly the bolted plate. These results were then compared against numerical predictions obtained using Ansys for finite-element analysis.

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