1 Introduction
2 Distributed Belt Wall Structure System
2.1 Concentrated Belt Wall System
2.2 Distributed Belt Wall System
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Since only a portion of the building façade is covered by belt walls, restrictions on architectural planning at the floor where the belt walls are placed is alleviated.
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For the belt wall systems planned as virtual outriggers, the floor slabs are subjected to high in-plane shear demand. If the belt walls are concentrated at one floor, the shear force acting on the slabs increases significantly. The distributed belt wall system can be an alternative to reduce the high in-plane shear demand of the slabs.
3 Shear Strength of Belt Walls
3.1 Material Models and Basic Assumptions
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Since the belt wall is confined by the left and right perimeter columns and by the top and bottom floor slabs including spandrel beams, uniform stress and strain field is assumed for the internal concrete panel of the belt wall. Thus, the behavior of the concrete panel can be represented as the stresses and strains of an element, shown in Fig. 10.
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The PS strands are placed along the x and y axes as reinforcements. The spacing and cross-sectional area of the PS strands in both axes are the same. The prestressing force applied to each strand by post-tensioning is also the same as fpe, where fpe is the effective prestress. Based on these conditions, a constant inclination angle of the principal stresses, θ = 45°, is assumed.
3.2 Prestressing of Strands: Initial State
3.3 Shear Cracking: Behavior of Uncracked Concrete
3.4 Yielding of PS Strands: Behavior of Cracked Concrete
3.5 Shear Strength of PSC Belt Walls
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To prevent early concrete crushing, the compressive stress fc2 of diagonal concrete struts should not exceed the effective compressive strength fce, as discussed in Eq. (8). Thus, if the factor βs is taken as 0.6 in Eq. (8) for conservative design, the reinforcement ratio ρp is limited to (ACI 318-14 and KCI 2012)$$\rho_{p} \le 0.51\frac{{f^{\prime}_{c} }}{{f_{py} }}$$(12)
4 Nonlinear Finite Element Analysis
4.1 Finite Element Modeling and Material Behaviors
4.2 Results of FE Analysis
Specimen | Effective prestress fpe |
f
pe,max
a
| Reinforcement ratio ρp (%) | ρp,max (%)b |
---|---|---|---|---|
PT23V | 0.315fpu | 0.338fpu | 0.2 | 1.22 |
PT26V | 0.629fpu | 0.338fpu | 0.2 | 1.22 |
PT43V | 0.315fpu | 0.623fpu | 0.4 | 1.22 |
PT46V | 0.629fpu | 0.623fpu | 0.4 | 1.22 |