Retaining Wall A retaining wall is a structure designed and constructed to resist the lateral pressure of soil when there is a desired change in ground elevation that exceeds the angle of repose of the soil. The active pressure increases on the retaining wall proportionally from zero at the upper grade level to a maximum value at the lowest depth of the wall. The total pressure or thrust may be assumed to be acting through the centroid of the triangular distribution pattern, one-third above the base of the wall. Stability of Retaining walls (a) sliding of the wall outwards from the retaining soil, (b) overturning of the retaining wall about its toe, (c) foundation bearing failure (d) larger scale slope or other failure in the surrounding soil. Retaining wall design has long been carried out with the aid of either the Rankine or Coulomb theories of earth pressure.Water loadWave loads Fluid pressure hydrostatic pressure (Hydrostatic Forces on Surfaces )Ice Loads iceberg impacts (流冰冲流冰冲击击力力)Wind LoadCharacteristic value of wind load (风荷载标准值)vertical to building surface Principal load-bearing structures Dynamic effect factor of wind (风振系数)at a height of Z; Shape factor of wind load Exposure factor for wind pressure Reference wind pressure Recurrence interval of wind pressure(重现期) Terrain roughness（地面粗糙程度） The population effects for the mutual interference of wind forces The mutual interference enlargement coefficient（群体风压体型系数） The shape factors for the local wind pressures (the fencing members and their connections)局部风压体型系数 Along wind direction wind excitation Magnification factor of wind fluctuation Wind fluctuation factor The vibration mode factor The width of windward side of structure Mass and rigidity basic wind speed Gust factor (阵风系数) Cross wind direction wind excitation Reynolds number Fundamental natural period of vibration for structure重力荷重力荷载载（ （Weight load） ）Within the framework of Civil Engineering, structural engineering is the discipline that creates the structural forms that serve to provide shelter, electrical power, and transportation for the population. It is often said that structural design is a combination of art and science. The experience and intuitive feeling of an engineer relative to the structure being built reflect the artistic aspects of structural design. The scientific aspects of structural design rely on knowledge of mechanics and material behavior.However, the two aspects are not separated since a good structural design requires a highly creative work based on engineering judgements and scientific principles.Before and assessment of the preliminary design can be accomplished, it is necessary to make a reasonable estimate of the loads that will be applied to the structure during its service life. These loads will produce strength and stiffness demands on the structure that must be satisfied by the strength and stiffness supplied by the selected members.The basic concept of a successful design is that the Demands of the applied loads must be less than the Supply of the strength and stiffness provided by the structural members.土土压压力：力：Soil Pressure土土侧压侧压力，地下水力，地下水压压力：力：Load due to Lateral earth pressure, Groundwater pressure.自重：自重：self-weightDetermination Method of Equivalent uniform loads Uniform Live Loads on Floors in Civil Buildings Live loads on Floors in Industrial Buildings Live loads on Roofs屋面屋面积积灰荷灰荷载载： ：Ash load on RoofsConstruction and Maintenance Loads, and Horizontal Load on Railings动动力系数：力系数：Dynamic CoefficientAccessible roof 上人屋面上人屋面Inaccessible roof 不上人屋面不上人屋面吊吊车车荷荷载载： ：Crane LoadVertical and Horizontal Crane LoadCombination of Multi-craneDynamic Coefficients of Crane LoadsCombination Value, Frequent Value and Quasi- permanent Value of Crane load雪荷雪荷载载： ：Snow LoadCharacteristic Value of Snow Load and Reference Snow pressure屋面屋面积积雪分布系数：雪分布系数：Roofing Snow Cover Distribution FactorReliability of StructureFunctionality:ServiceabilityThe structure has to be designed to function properly during its anticipated service life. This usually means that excessive deformations and undesired vibrations should be not occur.SafetyThe structure must be designed with sufficient strength and stiffness to resist the design loads and have enough reserve deformation capacity to maintain life safety under possible extreme loads. Sustainability of Civil Engineering Structures DurabilityThese loads are termed the “dead load” since they are fixed with regard to both position and magnitude. Occupancy loads are considered to be “live loads” since both their magnitude and location are uncertain.Earthquake engineering is concerned with the design and construction of all kinds of civil and building engineering systems to withstand earthquake shaking. Seismic Waves Interaction of structures with the shaky groundEarthquakes shake the ground in a variety of directions Horizontal and Vertical Shaking When earthquake shaking occurs, a building ge