【正文】 be no nonstructural damage either. Buildings should suffer none of minor structural damage (repairable) in occasional moderate earthquakes. Buildings should not collapse in rarely occurring major earthquakes. During such earthquakes structures are not expected to remain in the elastic range. Yielding of reinforcing stell weill lead to plastic hinges at critical sections. The general design philosophy will not have much practical use unless design requirements are developed in parallel with this author believes that the design requirements can be summarized in three groups. requirements requirements requirements(or drift control). These three requirements will be briefly discussed in the following paragraphs. Requirements Members in the structure should have adequate strength to carry the design loads the designers are well acquainted with this requirement,it will not be discussed in ,it should be pointed out that the designer should avoid brittle type of failure,by making a capacity design(1).The basic principles in capacity design are illustrated for a beam in Figure the design shear is puted by placing the ultimate moment capacities at each end of the beam,the designer can make sure that ductile flexural failure will take place prior to shear failure. Requirements In general it is not economical to design R/C structures to remain elastic during a major has been demonstrated that structures designed for horizontal loads remended in the codes can only survive strong earthquakes if they can have the ability to dissipate considerable amount of energy dissipation is provided mainly by large rotations at plastic energy dissipation by inelastic deformations requires the members of the structure and their connections to possess adequateductility”.Ductility is the ability to dissipate a significant amount of energy through inelastic action under large amplitude deformations,without substantial reduction of strength. Adequate ductility can be acplished by specifying minimum requirements and by proper detailing(2). Requirements In designing a building for gravity loads,the designer should consider serviceability in addition to ultimate seismic design,drift limitations imposed might be considered to be some kind of a serviceability ,the drift limitation in seismic design is more important than the serviceability requirement. The limiting drift is usually expressed as the ratio of the relative storey displacement to the storey height(interstorey drift).Excessive interstorey drift leads to considerable damage in nonstructural many cases the cost of replacing or repairing of such elements is very interstorey drift can also lead to very large second order moments(Peffect)which can endanger the safety and stability of the interstorey drift control is considered to be one of the most important requirements in seismic recent Mexico and Chile earthquakes have demonstrated the importance of this requirement(1).In Turkish Code the interstorey drift is limited to ,where h is the storey height. LEARNED FROM PAST EARTHQUAKES Our knowledge in seismic design has developed has developed as a result of analytical and experimental research and experience gained from past author believes that lessons learned from past earthquakes have been the most important source among all others,because earthquakes perform the most realistic laboratory tests on the buildings. The author has reevaluated the damages observed in earthquakes during the past 30 years in reevaluation has revealed that more than 90%of the damages can be attributed to one of the following causes or binations of these: made in choosing the building configuration(general configuration or the structural system chosen). detaling and proportioning or errors made in detailing. construction quality caused by inadequate supervision. It is interesting to note that causes of damage grouped into the above three categories seem to apply to earthquake damages observed in other countries three causes will be discussed briefly in the paragraphs to follow. Configuration Seismic resistance should be initiated at the architectural design the general configuration chosen by the architect is wrong,it is very difficult and expensive for the structural engineer to make the building seismic a general principle the floor plan should be as symmetrical as length of wings(T,L,.cross shaped buildings)causing reentrant corners should not be the length of the wings is not short,then these should be separated from the main building by an expansion about the elevational axis is not as significant as the plan ,abrupt changes in building plan along the height of the building are not desirable from the seismic resistance point of are mon vertical irregularities in building cause discontinuities and abru