土木工程专业英语电子课件ch.pptx

Chapter 5 Load and Design Process; All large cities have building codes that specify not only working stress but also other features of other structures. A standard set of specifications may be accepted to represent the best information available on the subject. The designer will follow the specifications of the local building code by necessity. All structures must be designed to support loads without danger of overall collapse or failure of the components. ; The plastic design is wholly dependent for its validity upon the formation of plastic hinges requiring considerable ductility of the material. By use of an appropriate factor of safety in plastic design, one may design ordinary continuous beams and frames for collapse loading with full confidence that a logical and balanced design will be achieved. ;For a given arrangement, the problem in structural design is 1、Estimation of loading 2、Determination of stresses and strains in structures 3、Design of elements and joints 4、Production of arrangement and drawings; One of the undeterminable factors in design may be the loading itself. Dead load can be estimated quite accurately, but live loading, wind, impact, sway, and other inertia forces are extremely variable. ; Designer over the years have attempted to achieve structural safety by ensuring that the effects of the applied loads on structures will not exceed the resistance or capacity of the structural members and connections, with a certain margin of safety. It may be expressed as Load effects Q≤ Resistance R; ; There are several methods in structural design. Allowable Stress Design (ASD), Load and Resistance Factor Design (LRFD) are within it. ASD method has been in use since before the 1900s. ; LRFD is a method of proportioning structural members using load and resistance factors, so no applicable limit state is reached when