CEE244 - Reinforced Concrete Structures

Featured Project

CE 244 Final Project — Seismic Design of a 9-Story RC Residential Building (1950 Oxford St., Berkeley)

Preliminary structural design package for a nine-story reinforced-concrete residential building with a basement, located just west of UC Berkeley and near the Hayward Fault. The building includes a lobby + eight residential floors and totals 112,128 ft². The basement plan is 160 ft × 160 ft, and the site is taken as Site Class C (very dense soil/soft rock).

Project Overview

Building

9-Story RC Residential

112,128 ft² • 1950 Oxford St., Berkeley

Seismic Category

SDC E

SDS = 1.73, SD1 = 0.85

Design Codes

CBC 2022 / IBC 2022

ASCE 7-22, ACI 318-25

Structural Systems

Gravity System

  • Unbonded post-tensioned flat-plate slabs (8 in nominal)
  • Level 1: 12 in conventionally reinforced slab
  • RC columns/walls; spans ≤ 32 ft

Lateral System

  • Special RC shear walls (coupled central core)
  • Wall thickness: 21 in (N–S), 25 in (E–W)
  • Coupling beams: 36 in depth, 72 in span

Analysis: CSI ETABS v20 (MRSA) + ACSAHE + custom spreadsheets

Key Design Results

Component Design Parameter Result
Core Wall (Flanges) Base Moment/Force Mu = 130,419 k-ft
Pu = 1,876 k (C)
Core Wall (Web) Base Moment/Force Mu = 26,670 k-ft
Pu = −1,269 k (T)
Reinforcement Vertical Bars No. 9 (flanges), No. 7 (web)
Wall Shear (N–S) Amplified Demand Ve,y = 3,870 kips
Wall Shear (E–W) Amplified Demand Ve,x = 3,169 kips
Transverse Reinforcement Wall Shear No. 6 @ 5 in o.c. (ρt = 0.00567)
Coupling Beam (Floor 5) Diagonal Reinforcement 12 #11 bars (Avd = 18.72 in²)
Special Boundary Elements Confinement #5 @ 5 in, lbe = 62.5 in (flanges)
Story Drift Maximum (MRSA) 0.645% (limit: 1.0%) ✓
Gravity Column (Base) Reinforcement 16 No. 9 bars, No. 6 ties @ 6 in

System Factors

R = 5 (bearing wall system)
Cd = 5
ρ = 1.0
Coupling-beam shear redistribution: ≤ 20% reduction

Deliverables

Full Report: 109 pages covering seismic input → wall sizing → interaction diagrams → shear design → coupling beams → SBEs → drift and gravity checks.

Drawing Sheets: S2.02 (wall shear), S2.03–S2.04 (SBE detailing), S2.05 (coupling beam).

Appendices: ASCE hazards report and ACSAHE report.

Related Project

ELC10 — Base-Isolated 7-Story Office Building (Mendoza, Argentina)

Seismic design of a reinforced concrete office building with base isolation system, completed as part of the "Estructuras Sismorresistentes" course at Universidad Nacional de Rosario (UNR).

Building

7-Story Office Building

12 m × 18 m (39.4 ft × 59.1 ft)
Mendoza, Argentina

Seismic System

Base Isolation

27 High-Damping Rubber Bearings
Period: 2.23 s

Design Codes

INPRES CIRSOC 103

CIRSOC 201-2005, CIRSOC 101-2005
Zona Sísmica 4

Structural Systems

Gravity System

  • Reinforced concrete slabs: 12 cm (4.7 in) thick
  • Contrapiso: 8 cm (3.1 in), carpet: 3 cm (1.2 in)
  • RC beams: 20 cm × 40–70 cm (7.9 in × 15.7–27.6 in)
  • RC columns: 24 columns, various sizes (35 cm × 35 cm to 100 cm × 20 cm)

Lateral System

  • 3 shear walls (tabiques): 18 cm (7.1 in) thick
  • Wall lengths: 2.05 m (6.7 ft) to 1.95 m (6.4 ft)
  • Boundary elements: 18 cm × 32 cm (7.1 in × 12.6 in)
  • Base isolation: 27 HM070X3R isolators (700 mm / 27.6 in diameter)

Analysis: STAAD Pro V8i (linear elastic, first-order) + iterative base isolator design

Materials

Concrete

H-25: f'c = 25 MPa (3.6 ksi)
10% quantile characteristic strength

Reinforcing Steel

ADN 420: fy = 420 MPa (60.9 ksi)
Yield strength

Isolators

Bridgestone HM070X3R:
High-damping rubber (X0.3R material)
Effective damping: 20%

Base Isolation System

Total Weight: 17,239.82 kN (3,876 kips)
Isolator Period: 2.23–2.26 s (nominal)
Max Displacement: 0.33 m (13.0 in)
Base Shear: 4,568.5 kN (1,027 kips)
Effective Stiffness: 13,946.5 kN/m (79.7 kips/in) per isolator
Damping Ratio: 20% (nominal), 20.03–25.50% (variation)

Key Design Results

Component Design Parameter Result (SI / Imperial)
Beam Strip (V14-V16) Longitudinal Reinforcement Piso 6: 2×Ø16 mm (2×#5)
Piso 1: 2×Ø16 mm + 1×Ø10 mm (2×#5 + 1×#3)
Beam Strip (V14-V16) Transverse Reinforcement Critical zone: Ø6 @ 9 cm (3.5 in)
Non-critical: Ø6 @ 18 cm (7.1 in)
Column C18 Longitudinal Reinforcement 35 cm × 35 cm (13.8 in × 13.8 in)
Additional Ø32 mm (#10) bars for tension
Column C18 Transverse Reinforcement Critical zone: Ø6 @ 10 cm (3.9 in)
Non-critical: Ø6 @ 15 cm (5.9 in)
Shear Wall C19 Longitudinal Reinforcement Boundary: Ø12 @ 13 cm (5.1 in)
Web: Ø12 @ 20 cm (7.9 in)
Shear Wall C19 Transverse Reinforcement Horizontal: Ø6 @ 17 cm (6.7 in)
Vertical: provided by longitudinal bars
Story Drift Maximum (X-direction) 0.77% (limit: 1.0%) ✓
Isolator Stability Verification All working points within stability envelope ✓
Max stress: 1.66 MPa (241 psi)
Max distortion: 2.36%

Design Methodology

The design followed an iterative process for the base isolation system:

  1. Initial assumptions: Target period TM = 2.50 s, damping βM = 20%
  2. Isolator selection: Based on required stiffness and displacement capacity
  3. Iterative convergence: Adjusted isolator properties until period converged to 2.23 s
  4. Stability verification: Checked compression stress and distortion limits
  5. Superstructure design: Used equivalent static method with R = 2.0 (limited ductility)

Energy dissipation mechanism: Plastic hinges in beams (floors 1–6), elastic columns except top story

Report Contents

Full Report: 69 pages covering structural predimensioning, base isolation system design, seismic action calculation, finite element modeling, and detailed reinforcement design for beams, columns, and shear walls.

Key Sections: Base isolator dimensioning with iterative convergence, equivalent static method for seismic forces, STAAD Pro modeling, drift verification, and complete reinforcement detailing.