This document defines and compares different types of prestressed concrete, including pre-tensioned and post-tensioned concrete. Pre-tensioned concrete involves stressing steel reinforcement prior to placing concrete around it. Post-tensioned concrete uses unstressed steel placed in concrete that is later tensioned. Bonded post-tensioning bonds the steel to the concrete, while unbonded systems separate the steel and concrete. Prestressed concrete provides benefits like increased strength, reduced cracking, and improved durability over conventional reinforced concrete.
It is the presentation based on pre- stressed concrete construction which includes each and every point and scope which may be useful to civil engineering students
Basic concepts – Advantages – Materials required – Systems and methods of prestressing –
Analysis of sections – Stress concept – Strength concept – Load balancing concept – Effect of
loading on the tensile stresses in tendons
A Stress Ribbon Bridge is a tension structure (similar in many ways to a simple suspension bridge). The suspension cables are embedded in the deck which follows a catenary arc between supports.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
It is the presentation based on pre- stressed concrete construction which includes each and every point and scope which may be useful to civil engineering students
Basic concepts – Advantages – Materials required – Systems and methods of prestressing –
Analysis of sections – Stress concept – Strength concept – Load balancing concept – Effect of
loading on the tensile stresses in tendons
A Stress Ribbon Bridge is a tension structure (similar in many ways to a simple suspension bridge). The suspension cables are embedded in the deck which follows a catenary arc between supports.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
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We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
NUMERICAL SIMULATIONS OF HEAT AND MASS TRANSFER IN CONDENSING HEAT EXCHANGERS...ssuser7dcef0
Power plants release a large amount of water vapor into the
atmosphere through the stack. The flue gas can be a potential
source for obtaining much needed cooling water for a power
plant. If a power plant could recover and reuse a portion of this
moisture, it could reduce its total cooling water intake
requirement. One of the most practical way to recover water
from flue gas is to use a condensing heat exchanger. The power
plant could also recover latent heat due to condensation as well
as sensible heat due to lowering the flue gas exit temperature.
Additionally, harmful acids released from the stack can be
reduced in a condensing heat exchanger by acid condensation. reduced in a condensing heat exchanger by acid condensation.
Condensation of vapors in flue gas is a complicated
phenomenon since heat and mass transfer of water vapor and
various acids simultaneously occur in the presence of noncondensable
gases such as nitrogen and oxygen. Design of a
condenser depends on the knowledge and understanding of the
heat and mass transfer processes. A computer program for
numerical simulations of water (H2O) and sulfuric acid (H2SO4)
condensation in a flue gas condensing heat exchanger was
developed using MATLAB. Governing equations based on
mass and energy balances for the system were derived to
predict variables such as flue gas exit temperature, cooling
water outlet temperature, mole fraction and condensation rates
of water and sulfuric acid vapors. The equations were solved
using an iterative solution technique with calculations of heat
and mass transfer coefficients and physical properties.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
2. Definition:
• “Pre-stressed concrete is a form of reinforced
concrete that builds in compressive stresses during
construction to oppose those found when in use.”
In other words it is a combination of steel and
concrete that takes advantages of the strengths
of each material.
http://www.youtube.com/watch?v=03Hb9V
CoEUo
3. Pre-Tension Concrete: pre-stressing steel is
tension stressed prior to the placement of the
concrete and unloaded after concrete has harden to
required strength.
Bonded post-tensioned concrete: unstressed pre-
stressing steel is placed with in the concrete and
then tension stressed after concrete has harden to
required strength
Un-bonded post-tensioned concrete: differs from
bonded post-tensioning by providing the pre-
stressing steel permanent freedom of movement
relative to the concrete.
4. Pre-tensioned concrete is when the steel
reinforcement is stressed prior to concrete
being placed around the steel.
5. Pretension is the easiest controlled of the
bonded stressings with the least chance
of error in the bonding process.
Tension caused by the steel is spread
throughout the length of the concrete since
it is bonded within the concrete along the
length of the member.
6. Usually uses a mold
which is able to resist
the forces within the
tendons. Which are
more expensive than
regular molds.
Exception comes when
the sides of the mold
our anchored allowing
mold to be created
between the anchors
without supporting
stress.
7. Concrete sample should be taken for every
new mix so that strength obtained may be
determined before cutting the tendons
releasing the stresses onto the concrete.
Since pre-tension may only be set once
calculations for the camber must be correct.
So, pre-stress takes a large amount of
preplanning. Must consider self-weight
deflections, pre-stress deflections, dead load
deflections, and live load deflections.
8. Since it may only tightened once and cannot
be retightened the designer must also
account for Creep of concrete, elastic
shortening of concrete, shrinkage of concrete,
relaxation of steel, slip at the anchorage, and
friction losses due to intended and
unintended (wobble) curvature in the tendons
in calculations for the camber of the member
in order to have lasting quality of the
structure.
9. Pretension requires for a slightly higher
compression rating to cut the steel over
post-tensioned .6 instead of .55 of the
compressive strength of concrete at the
time of initial pre-stress before accounting
losses such as creep, relaxation and
shrinkage, and redistribution of force
effect.
10. Mold capable of supporting stresses created by the
steel is either delivered to job site or molds are
located off site.
Required or preplanned pre-stresses are
determined and required reinforcement steel is
determined and set.
Proper concrete mix is determined and placed into
molds. Self-consolidating concrete is massively
used for ease of finishing.
Concrete is allowed to cure and reach a needed
strength great enough to support the tension in the
steel without cracking. Then steel is cut and
member is removed from mold and is ready to
install.
11. Process
• Concrete is casted around a curved
duct (usually corrugated), to allow room
for the Tendon to be inserted.
• After the concrete has hardened the
tendons are pulled in tension and then
wedged.
• The duct is then injected with gout
12. Advantages
• Tendons are less likely to de-stress in accidents
• Tendons can be easily 'weaved' allowing more efficient designs
• Higher ultimate strength due to bond generated between the strand and
concrete
• No issues with maintaining the anchor
13. In post-tensioning, the steel in the concrete is
stretched after the curing process.
Unlike bonded, un-bonded provides tendons
freedom of movement by coating each tendon
with grease and covering it with a plastic
sheathing
Tension on the concrete is achieved by the
cables acting against the steel anchors that
are buried in the perimeters of the concrete
15. Advantages
• Post-stress grouting is eliminated
• Ability to de-stress the tendons
• Economical
• Replaceable
• Simple stressing equipment
16. Forms
• Wires
• Strands
• Tendons
• Cables
• Bars
Source of Force
• Mechanical
• Hydraulic
• Electrical
• Chemical
17. Concrete remains un-cracked
Reduction of steel corrosion
Increases durability
Good for pressure vessels
High span to depth ratio (ex: 45:1 vs. 28:1)
less dead load
More economical