Plastic analysis of steel structures
Georgios Michas
Supervisor: Dr. Alessandro Palmeri
Beng (Hons) in Civil & Structural Engineering, May 2009
1.Introduction 3.Results and Discussion Application 3 (EPP & REP)
Conclusions
According to Kinematic Theorem
This study investigates the plastic methods of  By the principles of virtual work
analysis in steel structures. Four structures were Application 1 (EPP)
analysed in different behaviour conditions. For According to Static Theorem:
the realistic behaviour of structures, analysis was  Free and reactant BM method were used for
carried out by Sap2000 FEM software. The manual calculations of collapse load (Wc).
results obtained are compared and discussed,
concluding in what an engineer must take into
serious consideration as far as plastic design is
concerned.
The results of manual computations and Sap2000
• Elastic Perfect Plastic (EPP) are identical.
Both manual and Sap2000 analyses found the
• Realistic Elastic Plastic including the strain same collapse mechanism and collapse load.
hardening (REP)
• RealisticElastic Plastic including both strain
hardening and second – order effects (REPS)
2.Literature Review
Stress – strain behaviour of a cross section.
Application 2 (EPP)
According to Kinematic Theorem:
 The principles of virtual work method were
used for manual computations of collapse load.
Elastic Perfect Plastic behaviour for design
purposes.
Application 4 (EPP – REP – REPS)
Push over analysis were performed by Sap2000.
4.Conclusions
• Manual methods of analysis and Sap2000
The results obtained from both analyses coincide results coincide with great accuracy.
with great accuracy. • Strain hardening effect is proved to be
• It has been proved by experiments that when beneficial.
strain hardening effect takes place, it induces • Second – order effects reduced considerably
considerable extra strength to a structure. the durability of the structure, resulting in a lower
• Second – order effects have been proved to collapse load than the one that simple plastic
outshine the advantages of plastic design, methods of analysis suggest.
resulting in a more sensitive structure than the Two different distributions of lateral loading
one that the simple plastic theory predicts. according to EC8, in order to simulate possible • Second Loading configuration proved critical.
• seismic forces that could act on the structure. • Further study is needed to define clearly the
impact of those effects on the structures.

STRUCTURAL ANALYSIS
FOR THE GANTRY LIFT SYSTEM
Maxim Karpushenko
Beng (Hons) Civil and Structural Engineering
Project Supervisor: Dr A Palmeri
Introduction Results
From the earliest times people have faced the problem ‘how to lift a • Static linear envelope results are slightly
load’. Progress made since that time in advancing the lifting lower than results provided by ALE.
technology, science and engineering allows lifting and transporting Difference caused by implementing different
objects of huge mass. With aid of advanced software modelling of codes of practise for design of structural
complicated structural systems becomes more accurate and saves elements i.e. BS and EC-3.
considerable time required to complete calculation. • Dynamic analysis yields more accurate
results. The reason for that is analysis of all
Aims and Objectives possible positions of load applied. No
• Apply standard procedures for structural analysis and design dynamic effect is noted as moving speed is
according to the Eurocodes. very slow. The 1.7% increase in bending
• Compare design of the gantry with British Standards. moment, compared to the static analysis
Figure 4: Static Analysis Moment Envelope
• Consider sensitivity of the results to the speed of moving load and envelope.
structures nonlinearity properties with aid of SAP2000 software. • Moving load at high speed increases dynamic effect and causes additional
• Assume possible improvements of the analysis model in order to Figure 1: Gantry in Operation oscillations, which result in higher values of critical stresses. Further increase in
gain more accurate results. bending moment by 141.7kNm is achieved.
• Stresses obtained from Nonlinear analysis are the same, the only difference
found is joints displacement results.
Assumptions
• Sinking support analysis does not cause significant stress increase.
• All joints are assumed to be pinned and stability of the structure • Robustness analysis shows what all structural members are important and
provided by the means of the bracing system (i.e. non-sway failure any of them causes the total collapse of the Gantry structure.
structure).
• Elastic-perfectly plastic material behaviour is assumed for analysis
purposes.
• The three different positions for the load (initial position, mid-span
of the beam and final position) are assumed for the static analysis.
• The time-history functions are applied to represent movement of
the load on top of the main runway beams. All possible positions of
the load are covered.
• The speed is significantly increased to cause dynamic effect and
check structures sensitivity and behaviour. Figure 5: Moment Diagram at mid-span: Slow Load Figure 6: Moment Diagram at mid-span: Fast Load
• Nonlinear analysis is developed to take into account deformed
shape of structure, tension-only elements and other material Further Recommendations
nonlinearities. Figure 2: 3D SolidWorks Model • The partial fixity of joints can be modelled with assistance of
SAP2000, as in practise, all joints are semi-rigid and only braces are
Analyses Types Component Stresses ALE Results
Static Dynamic Dynamic connected with pins, which do not transfer any moment between
Analysis (Slow) (Fast) components.
• Static Linear Analysis
Major Moment
• Modal Analysis 3-3
11804.1kNm 11385.7 kNm 11583.7 kNm 11725.4 kNm • Take into account lateral skidding of the gantry lift system itself.
• Dynamic Linear Analysis for Beam at mid- Minor Moment • Operation of the skidding system might be modelled as series of
452.8 kNm 456.7 kNm 565.7 kNm 573.6 kNm push/pull steps, which might induce additional oscillations compared
the moving load span (f4) 2-2
• Dynamic Linear Analysis for Abs. Deflection
51.3 mm 50.6 mm 50.5 mm 50.8 mm to the smooth movement of the load.
UZ (j6) • Lifting crossbeams might be added to the model as they can provide
the load moving at high speed
Beam at support
• Static Nonlinear Analysis (f2)
Shear Force 2632.3 kN 2537.6 kN 2319.4 kN 2189.9 kN additional restrains to the main runway beams and different modes
• Dynamic Nonlinear Analysis Column of vibration might be obtained.
Axial Force (j13) 2932.3 kN 2913.6 kN 2026.7 kN 2059.73 kN • Lifting and lowering dynamic action can be modelled superseding
• Sinking Support Conditions (Reaction)
• Robustness Analysis Figure 3: SAP2000 Model. Frames. Table: Critical Stresses Comparison need for the additional vertical action dynamic coefficient.

MANAGEMENT OF BRIDGES
GEORGIA LEONTI supervisor: Dr Palmeri
INTRODUCTION CASE STUDY
This project reviews bridge management requirements. Specifically, in this project, we expose the results and research in
It presents recommendations for: structural risk analysis applied to computerized management
the optimisation of inspection system, through case-study of true project: the Rion-Antirion
maintenance of bridges Bridge, risk-based surveillance and maintenance.
the prediction of deterioration OBJECTIVES In order to entire the health monitoring system and to supply the
service life bridge owner, a generally
and management strategy reliable surveillance
Many aspects of bridge management relate to the maintenance strategy
management of a stock of bridges. the inspection
Techniques which are used to aid the management and maintenance manual has been districted according to the
of bridge stocks include: results of the risk analysis. The strategy for parameter adjustment
whole- life cost, is as well defined in the manual.
sustainability Bridges attain their design This project separates bridge Inspection frequencies and intervention thresholds are dogged
and risk analysis life, remain open to traffic management into project and for the whole life of the arrangement.
These techniques make use of economic or probabilistic models. continuously and their risk network level management. The inspection and maintenance strategy has been computerized
of failure is always very low. Project- level aspects, such as the in the inspection and maintenance management software. The
MAIN BODY These objectives are to be load carrying, condition- software includes a defect management system; rely on drawing
achieved sustainably and at performance and non- destructive management, as well as inspection checklists associated to a
Project level bridge management: minimum lifetime cost. tests. modified rating system.
There are several ways to evaluate bridge condition. Network-level is more associated The inspection checklists allow, by simple requests on the
The main phases of deterioration. with the rate of deterioration, database, to focus on the elements with harmful problems thanks
Progressive breakdown of protective systems ‘Bridge management’ encompasses a optimal maintenance and the to the rating system.
Physical deterioration of bridge elements, leading to a broad variety of activities aimed at effectiveness of variety The drawing defect management allows to:
reduction life ensuring the safety and functionality of maintenance strategies, prediction Do full structural analyses
Significant damage with possible hazards to users bridges. An efficient bridge management of future condition and Quantify the maintenance and repair costs according to the
Substantial damage => serviceability of the stock. amount of defects of the similar type that are present on the bridge
scheme is necessary to support the
Preventative maintenance techniques should be Computer –based databases and their associated analysis Guess in parallel and during the years, the evolution rate of every
highway remaining continuously open to
effective and easy to carry out. algorithms are called BMS. They consist of a number of type of defect, and consequently decide the best time and locations
the traffic with a sufficiently low level of
Assessment of load carrying capacity of a bridge is modules such as: to perform maintenance in order to get the maximal efficiency.
risk.
made when deterioration inventory
The results from activities such as:
is considered to be sufficiently as to have reduced the inspection, assessment and test records
Inspection,
strength or when loading maintenance records
Assessment of load- carrying capacity
standard is changed economics of maintenance methods
Sampling –non destructive tests are used
Sampling and non destructives tests used for special economics of traffic disruption and management
to prioritise the maintenance
inspection rate of deterioration CONCLUSIONS
requirements
optimised and prioritised programmes Many research works are being carried out worldwide on inspection
Network level bridge management: The evaluation of their existing
The development of relational database systems has condition and health monitoring, capacity assessment, life-cycle cost analysis
Other techniques used in the management of bridges: and maintenance and repair. Efforts should be addressed in the
enabled bridges to be managed as stock. This has Their rate of deterioration.
whole –life costing following directions:
number of potential advantages. are necessary to decide the most suitable
risk analysis Development of simplified methods based on the findings of
Design features and materials with defects can be time to carry out maintenance work.
sustainability assessment advanced research but made more useful to the managing engineer.
identified
The influence of bridge maintenance on traffic flow Need of codification and standardization in some specific areas as
Rate of deterioration of a particular bridge can make the condition assessment and make use of new-fangled equipment
use of information of bridges of similar stock and age and techniques for bridge repair and strengthening.
in the stock Whole-life cycle cost and initial cost increase as the service life
The cost effectiveness of different maintenance increases. It is more reasonable to use annual cost.
methods can be established A proposed database system is introduced in this project in order
Maintenance work on different bridges in the stock to facilitate in-house works and to make networked linkages
can be prioritised nationwide. Further study is planned to introduce this proposed
Maintenance programmes and budgets for the stock model in actual practice of bridge maintenance and management.
can be planned.
The performance of a maintenance programme can be REFERENCES INTERNAL SOURCES
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Highway Bridges. Journal of Computing in Civil Engineering, ASCE, Vol 15, January 2001, p 27 http://www.atyponlink.com/TELF/doi/abs/10.1680/cien.144.1.166.39555, 1/4/209
the bridge stock. – 34 http://www.cosis.net/abstracts/EGU06/03272/EGU06-J-03272.pdf, 2/4/2009
2. Frangopol, D. M. & Lin, K. Y. 1997. Life-Cycle Cost Design of Deteriorating Structures. Journal http://www.fabermaunsell.com/MarketsAndServices/36/74/index.jsp, 3/4/2009
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