Session 5.1 - Structural Frames

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Displacement Capacity of Dual Reinforced Concrete Building Systems

T. Paulay

To enable expected seismic displacement demands on building systems to be accommodated, the knowledge of its dependable displacement capacity is indispensable. A rational and simple approach to relevant displacement estimates is presented. The displacement capacity of a ductile system is controlled by either that of its clearly identified critical element, or by magnitudes of storey drifts satisfying codified performance criteria or those chosen by the designer. Attractive features of this design, rather than analysis-oriented approach, are that displacement capacity estimates do not require the knowledge of seismic strength. The designer may assign fractions of the lateral design forces, eventually required, to various elements, to suit design intentions and practicality in construction, with disregard for traditionally perceived values of element stiffness.

Paper 130: [Read][Print]

Keywords: displacement capacity, reinforced concrete, seismic design

Estimation of Seismic Strength of RC Frames Designed to Gravity Loads in Korea

Y.W. Lee

The seismic design regulations have not been applied to low buildings that are less than 6 stories in Korea. Although they are only designed for gravity loads, they have inherent strength to resist moderate earthquakes. In this study, to have a clear understanding the characteristics of the inherent strength, theoretical equations are derived based on column or beam hinge sway mechanism. For the comparison of accuracy, the 3, 4 and 5-story buildings are designed and push-over analyses were performed. The comparisons show good agreement between theoretical values and numerical analyses for weak column strong beam structures. The strength of re-bar, steel ratio of column, bay number and span length are all shown to be proportional to the inherent strength but story height and DL are shown to be inversely proportional to the inherent strength.

Paper 081: [Read][Print]

Keywords: seismic inherent strength, designed, gravity loads, reinforced concrete frame, estimation

Seismic Performances of Reinforced Concrete Frames under Low Intensity Earthquake Effects

B. Li, Y.M. Wu and T.C. Pan

In a region of low to moderate seismic risk and low wind speed, such as Singapore and Malaysia, buildings with relatively weak lateral structural resisting system are likely to represent a large portion of the building inventory. Many buildings appear to contain possible soft-stories. Although ground shaking motions, due to long distance earthquakes centred in Sumatra, have occurred in Singapore and Malaysia, there has been no record of earthquake damage in this region. However the reinforced concrete design code, BS 8110, used in Singapore and Malaysia does not specify any requirement for seismic design or detailing of reinforced concrete structures. The main objective of this paper is to strengthen the need to look into the seismic performance of some typical existing and prospective reinforced concrete frame structures designed to BS 8110 in Singapore under low seismic loading. The performance of the structures is checked through a non-linear dynamic analysis.

Paper 125: [Read][Print]

Keywords: beam-column joints, ductility, strength

Analytical Model for Beam to Column Joints in RC Moment Resisting Frames

S.R. Uma and A. Meher Prasad

Damage in reinforced concrete structures from earthquake attacks was mainly attributed to shear force due to the inadequate detailing of reinforcement and the lack of transverse steel and confinement of concrete in structural elements. For better seismic performance of R/C moment resisting frames, joint panel zones are preferred to be elastic, however, weak joints undergo inelastic deformations and fail in shear and bond. In this paper, a new analytical model for shear characteristics of joint has been proposed which estimates the shear strength capacity and predicts the amount of shear deformation by establishing shear stress-shear strain relationship based on softened truss model theory. The model adopts constitutive law for softened concrete including confinement effect in the joint. Inelastic behavior associated with the slip of longitudinal reinforcement anchored in the joint is represented through bar slippage model. The response of joints and its effect on overall behavior have been studied by carrying out nonlinear dynamic analysis on experimental sub-assemblages under cyclic loads. The critical responses in the joint behavior were noted down and good comparison was observed with available experimental results.

Paper 106: [Read][Print]

Keywords: analytical model, beam-column joint, bond-slip, cyclic loads, joint shear deformation, moment resisting frames, non-linear dynamic analysis

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