The Research And Reliability Analysis On The Serviceability Of Steel Frame Under Wind Load

Safety and serviceability of steel frame structures under wind load must be considered in their design. The safety of the structures includes the bearing capacity and stability, the serviceability of the structures mainly refers to the lateral drift and human comfort. Although structural serviceability issues will not directly affect the safety of structures, but if the structure drift is too large or has excessive vibration, it will seriously affect the use of the building, make the users feel uncomfortable. In recent years, the steel frame structure has been more widely used in china, the serviceability problems of steel frame are becoming prominent and need for further research in urgent.The following two key issues need to solve in the serviceability research of steel frame structures:First, our country is currently lack of research on serviceability of steel frame under wind load, the code’s specifications for the lateral drift are also relatively brief. It will make designers easy to overlook a series of problems which cause by serviceability when designing a steel frame. As our nation’s living condition getting improve day by day, the building’s user also ask for a higher demand of they living and working environment in the building. If the designers lack of consideration of the building’s serviceability,it will seriously affect the use of the building. At the same time,the researches on reliability of steel frame under serviceability limit state are also few,and the research results are not mature enough. in order to ensure the structurals have good performance when in service, it is necessary to carry out researches on the reliability of steel frame under serviceability limit state.Secondly, in our nation’s current GB50017-2003’Code for Design of Steel Structure’, the structure’s drift limits are given in a uniform provision, when it allows designers to use both first-order and second-order analysis methods for structural analysis. for the drift result obtain by second-order analysis is more than the result obtain by first-order analysis, so, for the same structure, in the same load conditions, if we adopt first-order analysis method to calculate the drift of structure to meet the required drift limits of current steel structure design specifications, when we adopt second-order analysis method, the drift result may not satisfied with the specifications, it will make designers feel confused.Against this background, this article mainly carries out researches on the following areas:First, this paper research on those factors including wind load calculation methods, wind load return period, nonstructural component’s drift damage thresholds, structure analysis method and calculation model which effect the calculation of structural drift under wind loads. Then carry out studies on those problems currently exist in drift limit research of steel frame. At last, a drift questionnaire of steel frame under wind load which meet our national conditions is given, it can be used to investigate and study the current structure engineers design situation of steel frame.secondly, this paper respectively used traditional first order calculation method, second-order simplified calculation method and second-order accurate calculation method to calculate a2-bays15-story steel frame’s lateral drift, the peak drift and inter-story drift of the steel frame use by three different methods are obtained. Then those drift results were compared. The influences on the drift of steel frame when considering second-order effect are study.Third, this article research on the reasonable inter-story drift and peak drift limits of steel frame considering the second-order effect, the second-order inter-story drift and peak drift limits of steel frames is given by using reliability theory and the analysis method which is used in present standard. Some examples are carrying out for the second-order drift limits verification.Fourth, the paper launched a study on human comfort limits of steel frame under wind loads, those factors that affect human comfort are summarized. Finally, the recommendations of peak acceleration limit of steel frame under wind load are given.Fifth, based on the calculation model of drift and human comfort in our nation’s JGJ99-89’Technical Specification for Steel Structure of Tall Buildings’ and GB50017-2003’Code for Design of Steel Structure’, the limit state equation and statistical parameters of drift and human comfort are given. Reference to the second-order drift and human comfort limits proposed in this paper, the reliability analysis model of steel frame on serviceability limit state is proposed. Finally, the reliability of steel frame under serviceability limit state is calculated by JC method and has been verified by some numerical examples.