The Research Of Designing Grid Beam Structures Of Reinforced Concrete

Grid beam structures is a force-resistant system in three dimensions, which iswidely used in the industrial and civil engineering such as the entrance hall of publicbuildings, for example, the great hall, the hotel and the super market. The grid beamstructure is a cross beam system, which can resist the stress reasonable. Meanwhile itcan cross large space which meets the demands of long distance between columns andlarge span of meeting rooms and entertainment halls. In addition, the grid beamstructures give us a beautiful and comfortable feelings and it can be decorated easily.Many scholars have used the method of structural mechanics to accomplish thecalculation of internal force and deformation of grid beam structure, basing on theanalytic expression of displacement. The achievement is almost about the grid beamstructure which is rectangular and very few about the round. Designing the reinforcedconcrete grid beam structures which is fixed constrained in the round boundary isresearched in this article, we get the internal force and displacement analyticexpression, the equation to determine the grid beam dimension and the formula tocalculate the steel reinforcement diameter which meets the need of crack width.As for the calculation of internal force, this article consults the method ofanalyzing the internal force and displacement of two way slab. According to theassumed displacement field, we can get the deflection formula of each directionthrough the principle of minimum potential energy. Then, we can make use of relationbetween deflection and moment to get the moment and shear be matched with. theformulas we get to calculate the internal force and the deflection are simple andfeasible. The results from the formulas is reasonable.Selecting the section dimensions is the key to designing the grid beam structures.According to the theory of elasticity and the limit deflection in the specification, thisarticle gets the equation about the height of the grid beam structure. Given thedistance between beams, numbers of beams and the span, in addition the materials ofconcrete and steel, we can get an equation of higher degree with one unknownquantity h. After solving this equation, we can get the height. The depth-width ratio ofrectangle section is usually2.0~3.5.now we have got the dimensions of the rectanglesection.It is essential to control the width of crack for the durability of concrete. This article finds a simply formula which uses the diameter of steel to control the width inthe concrete and we get which from modifying and simplifying the formula given inspecification. As long as the diameter of selected steel is not greater than the result ofthis formula and it meets the detail design, the width of crack will meet the demandsin the specification. Besides, not only controlling the width of crack in the concrete,but also guaranteeing that the concrete cover has an appropriate thickness and theconcrete has a good quality and degree of density is important to protect the structurefrom corroding.