Study Plan:
1. Aim:
This study aims to evaluate the structural performance of flat slab-frame systems in a
region of a moderate seismic hazard, whereas the lateral resistance will be solely
determined by the frame action. The study examines systems with different span
lengths using flat plate slabs, compares them to two-way ribbed (waffle) slabs, and also
analyzes their material consumption.
2. Problem Statement:
Buildings consist of flat slab-frame systems, and depend entirely for their lateral
resistance on the slab actions are economical up to approximately 25 stories (Smith &
Coull, 1999). On the other hand, ACI specification does not permit two-way slab
systems to be used in regions of high seismic risk (Uniform Building Code (UBC)
zones 3 and 4) and limits their usage in regions of moderate seismic risk (UBC zones
2 and 2B), subject to certain requirements, mainly relating to the placement of
reinforcement in the column strip region. However, the lateral stiffness of a flat slabframe is affected by cracking and other parameters include the relative span lengths
and the concentration of reinforcement in the slab width (Taranath, 2010).
Collectively, after the excessive literature review, it can be noticed that the studies
clearly demonstrated the vulnerability of flat slab structures to lateral load effects and
the attention that should be paid to slab-column connections. While, in severe seismic
zones, research showed the need for combining a flat slab system with a lateral resistant
system to enhance its performance.
Fewer studies have considered waffle slabs and their lateral resistance behavior;
however, this type of slab systems could be classified as a form of flat slab systems,
according to BS 8110 standard. Other researchers were concerned by the comparison
of flat slabs with other types of slab systems, from which it could be drawn that both
flat slabs and waffle slabs are less preferable than solid slabs when considering the
lateral resistance behavior. The majority of studies investigated flat slab-frames in
conjunction with lateral resistant systems, while exposing them to high seismic
loading. And there is limited information on the influence of span length on the
behavior of this type of construction.
3. Objectives:
3.1. Analyze and design a mid-height (8-story) building to resist vertical loads and
lateral loads of a moderate seismic hazard, depending entirely for their lateral
resistance on the slab-column actions.
3.2. Evaluate the lateral structural performance of two types of flat slab-frame systems,
flat plate slabs and two-way ribbed (waffle) slabs.
3.3. Examine the lateral structural performance of systems with different span lengths
using flat plate slabs and then compare them to two-way ribbed slabs.
3.4. Analyze and design the two types of floor systems for the different span lengths
and compare their material consumption.
4. Methods:
Structural models will be developed, analyzed and designed using finite elements based
software programs.
5. Methodology:
5.1. Software and Tools:
The study uses ETABS for structural modeling and lateral load analysis, and SAFE for
analysis and design of slab systems.
Material Properties:
- Concrete compressive strength (fcu): C (40/50)
- Steel yield strength (fy): 460 N/mm2
5.2. Structural Model Definition:
For the same span length and material properties, two identical building models, one
with flat slabs and the other with waffle slabs, will be analyzed and designed.
5.3. Loading Conditions:
- Gravity loads: dead load and live load.
- Lateral loads: earthquake loads as per Eurocode 8 (EN 1998-1: 2004)
5.4. Boundary Conditions & Constraints:
Supports at the base are considered fixed.
5.5. Analysis Approach:
The Static Linear Analysis method (also known as the equivalent lateral force
procedure) is to be used. This type of analysis is suitable for the majority of high-rise
structures, and it is recommended for unexceptionally high buildings with
unexceptional structural arrangements (Smith & Coull, 1999).
5.6. Comparison Parameters:
- Lateral Displacement: measuring max displacement of each system.
- Inter-Story Drift: comparing drift limits.
- Overall Drift: assessing them according to traditionally accepted limits.
- Stiffness & Strength: force-deformation behavior.
- Material Quantities: required reinforcement and concrete volumes.
6. Sampling Design:
- Mid-height buildings, 8-story (ground + 7 floors) with 3 m height for each story.
- The buildings are assumed to be residential, with different span lengths while
maintaining the plan areas of floors within close values.
- Square plan floors (approximately 24m x 24m).
- Five different span lengths of 4 m, 5m, 6 m, 7 m, and 8 m are used for comparison.
7. Analysis of Data:
The finite element based software programs, SAFE and ETABS will be used for the
analysis process.
The methods of analyzing their outputs will include both quantitative and qualitative
approaches. These techniques aim to evaluate the performance of two types of flat slabframe systems, flat plate slabs and two-way ribbed (waffle) slabs under various span
lengths.
7.1. Comparative Quantitative Analysis:
Conclusions will be drawn after a numerical comparison of results.
- Displacement and Drift: Comparing lateral displacements, inter-story drifts,
overall drifts, and deflections.
- Internal Forces: Comparing bending moments, shear forces in slabs and also the
axial loads in columns.
- Base Reactions: Evaluating total and individual base reactions.
- Punching Shear: Assessing and comparing punching shear ratios and capacities
in flat slabs vs. ribbed slabs via SAFE software.
7.2. Graphical Interpretation:
Chart Plots with excel tool to demonstrate each of the following:





Lateral displacements.
Inter-story drifts.
Overall drifts.
Base moments and shear forces.
Concrete and Reinforcement Amounts.
7.3. Parametric Study:
Analyzing the trend of changes in outputs:
- How increasing slab span affects lateral displacement, inter-story and overall drifts,
and material consumption?
- Create graphs of inputs vs. outputs (span vs. steel and concrete quantities, span vs.
stiffness and displacement).
7.4. Structural Performance Criteria:
Assessing structural performance and efficiency based on stiffness and strength using
stiffness degradation or lateral stiffness comparison.
These analyses will be summarized in tables, graphs, and comparative charts, then the
implications of each result will be discussed.
8. Budgeting:
8.1. Cost: little money.
8.2. Time: the research has been divided into eight stages. The time table of the
expected percentages of completion is shown below.
Stage 1: selecting the area of the research.
Stage 2: conducting literature review.
Stage 3: identifying the research gab and defining the research problem.
Stage 4: preparing the research plan.
Stage 5: developing the structural models of the buildings.
Stage 6: executing the analysis and design.
Stage 7: analyzing the results and extracting conclusions.
Stage 8: writing the report.
Table (1): time-table of the expected percentages of completion for research
stages:
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
Stage 6
Stage 7
Stage 8
20/4/2025
100 %
80 %
100 %
90 %
40 %
0%
0%
10 %
5/5/2025
20/5/2025
5/6/2025
20/6/2025
80 %
80 %
90 %
100 %
100 %
100 %
0%
0%
30 %
90 %
0%
30 %
100 %
35 %
50 %
100%
80 %
5/7/2025
100 %
References:
Smith, B. S., & Coull, A. (1999). Tall Building Structures-Analysis and Design. A
WILEY-INTERSCIENCE PUBLICATION.
Taranath, B. S. (2010). Design of Tall Buildings. Taylor and Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business.
Notice:
This study plan has been checked for plagiarism on the web site
(https://app.gptzero.me) and it has been verified that this study plan is 100 % original.