on the seismic performance of frame-shear wall structures with high-strength
reinforced shear wall
Abstract: High strength steel reinforcement in the shear walls of frame-shear wall structures can efficiently increase the safety margin and change the seismic force distribution because the shear wall will yield after the frame. With the fiber model program THUFIBER and the multi-layer-shell program, which are developed by Tsinghua University and are based on the general purpose finite element software of MSC.MARC, two 8-story reinforced concrete frame-shear wall structures, whose shear wall are reinforced with normal and high strength steel respectively, are studied with static pushover and dynamic analysis. The effect of high strength steel in the shear wall to the control of seismic performance of the structures is emphasized. The results show that with high strength steel in the shear wall, the softening behaviors of frame and shear wall are changed. The yield strength of the shear wall is increased while it still has the same the deformation capacity. And the safety margin of the whole structure is efficiently increased which benefits the seismic capacity of the structure.
Key words: frame-shear wall; high-strength reinforcement; pushover; dynamic; nonlinear
Abstract: Due to progressively using in practical construction of prestressed concrete structures, the researches for seismatic performance of prestressed concrete (PC) structures has remarkable significance in engineering practice. Because of the complicated behavior of material and loads, the precise simulation of PC structures or members under cyclic loads has to depend on numerical model. In this paper, a numerical analysis model for the simulation of PC member structures has been developed on the basis of a fiber model program. A PC frame, an unbonded PC frame and an unbonded PC column under cyclic loads are simulated with the developed program. The comparison of the results between simulations and tests indicates that, for the reason of using rational hysteretic material model and exactly considering the influence of prestressing, the numerical analysis model based on fiber models developed in this study can accurately predict the hysteretic properties of PC structures and can be used in the parametric analysis and mechanism study.
Keywords: fiber model; cyclic load; prestressed concrete; analysis method
Abstract: In the present world major catastrophe is yet severe earthquakes. Many devices which include in active, hybrid and semi-active structural control systems as controllable force devices are costly in their construction and maintenance. The mechanism of the passive control RC frame (PCRCF) reinforced with high strength reinforcements only in columns presented here is an attempt to provide structural systems more resistance against lateral earthquake loadings at comparatively lower cost. The concept is demonstrated by nonlinear static analysis by fiber model for a single story single bay frame. The study revealed that use of high performance steel in columns can prevent formation of plastic hinges at the critical column base sections and failure always initiated by yielding of reinforcement at beam ends. Further after experiencing severe lateral drift, PCRCF showed small residual displacement as compared to ordinary RC frame. Rehabilitation and strengthening of the frames can be made easier for PCRCF.
Keywords: earthquake, passive control, high strength reinforcement, failure mechanism, residual displacement
strength/performance structural materials and the developments of modern
engineering structures and the design theory
Abstract: This paper firstly presents the latest development of high strength/performance structural materials in recent years. The rational applications and examples of high strength/ performance structural materials in the structural systems to obtain high performance are discussed and presented. The positive functions of high strength reinforcement used in reinforced concrete frame structures, that can enhance the structural performance against earthquake and reduce the structural seismic damage, are investigated in detail with nonlinear pushover analysis and dynamic analysis. The results show that the high seismic performance of the reinforced concrete frames, including a delayed appearance of plastic hinges at the bottom story columns feet, to form a rational failure mechanism under strong earthquake, and a small residual displacement after earthquake that cause an easy retrofitting after earthquake, can be obtained by replacing normal strength reinforcement with high strength reinforcement in the columns. Finally, the development of the safety and design theory for the structures using high strength/performance materials are discussed.
Keywords: High strength/performance concrete; High strength/performance steel; Engineering Structures; Structure safety; Design theory; Accidental event; Earthquake resistance.
ABSTRACT: To achieve better structural performance during earthquakes and to minimize rehabilitation and strengthening costs after seismic event is the main objective of the earthquake resistant design. With the invention of the high performance materials and their introduction to the structures, the failure mechanism and seismic performance, especially the residential deformation, can be improved seismic. The Passive Control RC Frame (PF) reinforced with high strength reinforcements in columns are investigated in this paper with nonlinear time history analysis method. It is found that the high strength reinforcements not only provides the RC frame more resistance against lateral earthquake loadings but also reduced the residual displacements after going through dynamic event. It is also seen that the use of high performance steel in columns can prevented the critical column base sections from yielding and totally eliminated the possibility of soft story failure mechanism. Moreover the strengthening and rehabilitation demands reduced and required only at the beam end sections. With the absence of total collapse mechanism it is envisaged that the use of PF would yield safer structures and the potential danger of complete demolition can be reduced.
Keywords: earthquakes, high performance steel, passive control RC frame, failure mechanism, residual deformation