Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES and seismic loads, as depicted in Figure 5.18, it is possible to define the following relations for the bending moments acting at the left and at the right of the joint. Mg,left Mg,right Ms,left + = Ms,right Figure 5.18. Gravitational and seismic action in an interior joint left s, left g, left Mp,left Mp,right - 2Mg,right Ms,left + Mg,left Ms,right - Mg,right M = M + M ( 5.47 ) M = M − M ( 5.48 ) right s, right g, right If it is assumed that during a seismic event the left bending moment of the beam reaches the value of the bending plastic moment, as a consequence: M = M + M ( 5.49 ) p, left s, left g, left Moreover, if the same allowances for the beam bending moment acting on the right side are made, we obtain: M = M + M ( 5.50 ) p, right s, right g, right Hence, combining Eqs (5.48) and (5.50), it is easy to obtain that the bending moment acting on the right of the joint is equal to: M = M − M = M − 2M ( 5.51 ) right s, right g , right p, right g, right This equation underlines that the gravitational loads reduce the effects of the seismic action in terms of bending moment acting at the joint. This beneficial effect of the gravitational loads is not included in the Eurocode prescriptions. Nevertheless, the AISC provisions (1997) approximately account for it by means of a reduction coefficient equal to 0,8. Besides, it has to be noted that the column shear reduces the total joint shear action at the beam-to-column joint position and 207
5. SEISMIC BEHAVIOUR OF RC COLUMNS EMBEDDING STEEL PROFILES thus increases the shear joint strength. In accordance with these assumptions, for the two seismic load combination (design case 2 and design case 3), we must check that: 1. Vj,Rd > Vj,Sd = 0,8 [(Mbeam,Rd,right + Mbeam,Rd,left) / ds – Vc] ( 5.52 ) where Vc is the average shear force at collapse in the web panel equal to: 208 (Vcolumn,top + Vcolumn,bottom) / 2 = (Mcolumn,Rd,top + Mcolumn,Rd,bottom) / (Hc – ds) ( 5.53 ) assuming that the zero-moment points are located in the middle section of the columns the equilibrium condition M beam = M column is satisfied. 2. Mj,Rd > 1,3 (Mbeam,Rd,right + Mbeam,Rd,left) ( 5.54 ) In view of the resistance evaluation, the following equations obtained from equilibrium of forces in the joint panel zone are used: Mj,Rd = Vjoint,inner · dinner + Vjoint,outer · douter ( 5.55 ) Vj,Rd = Mj,Rd / ds ( 5.56 ) 5.5 The experimental test programme 5.5.1 Design of the reduced section of the specimen to be tested For what concerns the laboratory experimentation feasibility, it was suggested to test the specimens in ½ scale. Hence, some geometrical and mechanical reducing factors had to be applied to the section properties which include: • exterior geometrical dimensions of the concrete column (b and h); • amount of longitudinal reinforcing bars in the column (As,long); • amount of transverse reinforcing bars in the column (As, stirrup); • dimension of the steel profile. Concerning the reduction of the steel profile two different possibilities were taken into account. The steel profile may be reduced either in term of the cross area As,steel or in term of plastic modulus Wpl,steel. The first solution ensures that the axial
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Dipartimento di Ingegneria Meccanic
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UNIVERSITÀ DEGLI STUDI DI TRENTO D
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Ai miei genitori
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INDEX 1 INTRODUCTION...............
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INDEX iii 4.10.3 Results of the PsD
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1.1 Introduction 1 1 INTRODUCTION I
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1. INTRODUCTION imposes precise con
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1. INTRODUCTION joints whilst 2D mo
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7 2 DUCTILITY AND SEISMIC RESPONSE
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2. DUCTILITY AND SEISMIC RESPONSE O
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Analysis and modelling of the seismic behaviour of high ... - Ingegneria

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