Structural Behavior Of Two-way Wood Truss Floors

Floor systems are an important part of light frame wood structures. The floorplays a role of partitioning the vertical space, as well as joining vertical componentsas a whole structure to resist external loads.This paper presents a two-way wood truss floor system by replacingconventional joists with trusses in two perpendicular directions in floors of lightframe wood structures. The floor system is similar to orthogonal space trusses.Two tests of structural performance of two-way wood truss floors wereconducted. According to the analysis of the first test, improvement measures of thefloor were given, including increasing the section of the bottom chord, applyingdouble diagonal webs to both sides and at both ends of truss, increasing steel boltsin the middle part of the floor to enhance chord connection. Based on theimprovement, the second test was conducted. In addition, material property tests ofthe timber of the floor also completed, and it’s the tensile strength, compressivestrength and modulus of elasticity parallel to grain obtained.Via tests and analysis, the stiffness of the floor meets the requirement of thecurrent Code for design of timber structures GB50005-2003after improvement.Uuder the basic load combination of3.4kN/m~2, the stress of the member is withinthe design strength of the material. But due to that fact that the floor system can failabruptly, further improvement suggestions of the structural arrangement were givento enhance the load capacity of the floor system.FE models for the two experiments were developed using ABAQUS andanalysis of structural performance of the floor system conducted. Both thedeflection of floor and the stress in the members correlated with the test resultsreasonably. The FE models were thus validated, and an analytical method forsimulating the structural performance of the floor system provided.According to the test results and numerical simulation results of the two tests,the main factor that affects the floor stiffness and load capacity is the degree that thetrusses in different directions can work together.The corresponding improvementmeasures and structural measures for the floor trusses to work together were given,and the manufecturing method of the two-way wood truss floors was suggected. andthen establishing corresponding finite element model. Via numerical simulation, itwas proved that the load capacity and stiffness of the floor meet the provisions ofthe current design code. Considering the characteristics of the floor system,calculation method for load distribution between the two-way truses-, the modifiedplate-analogy method, was developed. Finally, the design method of the floorsystem was provided.