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DURABLE STRUCTURES LNEC Lisbon 31 May - 1June 2012


OPORTO´S SPORTS PAVILION REFURBISHMENT AND REHABILITATION PROJECT



OPORTO´S SPORTS PAVILION – REFURBISHMENT AND REHABILITATION PROJECT 2

– Existing Structure Description

– Renovation Project

– Structural Assessment and Inspection

– Structural Interventions

SUMMARY

ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC • Lisbon • Portugal • 31 May - 1 June 2012

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– Inaugurated in 1952, to host a Hockey World Championship without the roof, which was later finished in 1954;

– Occupied the same location as the Crystal Palace, dated 1865 and inspired by London’s original;

– 6500m2 & 5000 seating capacity;

– Original design from the architect J. Carlos Loureiro, who participates enthusiastically in this renovation project.

EXISTING STRUCTURE DESCRIPTION

Crystal Palace

Oporto’s Sports Pavilion inauguration in 1952




EXISTING STRUCTURE DESCRIPTION – The entrance level slab (3.3m) is

divided into 9 parts, with one circular plus 8 radial expansion joints;

– Four levels of galleries above level 3.3m supported by 32 triangular frames and also divided by the 8 radial expansion joints;

– Stahlton slab – in general Two-way slabs 25cm thick, pre-stressed in one direction and supported by a grid of beams;

– Shallow foundations.

•FLOORS


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EXISTING STRUCTURE DESCRIPTION

– 72m diameter, 15m high dome;

– Ribbed reinforced concrete spherical cap;

– Thin (8cm to 5cm) two way reinforced slabs;

– Supported by 32 radial beams (meridians)

– and 8 circular beams (parallels);

– These slabs have circular skylights;

– In 1959, it was applied a cooper sheet waterproofing, giving it its characteristic greenish look.

•ROOF




RENOVATION PROJECT

The renovation project determines the construction of new structures, becoming a congress complex with a large auditorium for 1000 people, several conference rooms and a restaurant.

The existing building will become a modern multipurpose arena for 7000 people.


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RENOVATION PROJECT

The new auditorium will be built over an existing underground parking, conditioning the supports location, and will have a steel structure roof with a free span of over 30m.

In the existing pavilion, permanent stands will be introduced, which implies the construction of steel beams attached to the existing structure to support the stand seating elements.

Given the uniqueness of this building the intervention observes the principle of reversibility, meaning that the added elements may be removed if necessary.




– Characterization of materials

– Building’s pathologies

– Static load test

– Dynamic load test

STRUCTURAL ASSESSMENT AND INSPECTION


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The inspection plan aimed at assessing the mechanical properties of the existing materials as well as the corrosion state of the rebar in the main reinforced concrete structural elements in order to determine the durability and remaining life time of the structure already aged at 60 years.

•CHARACTERIZATION OF MATERIALS





•CHARACTERIZATION OF MATERIALS

Steel’s strength and Young Modulus determination

Concrete’s strength, Young Modulus and carbonation penetration determination


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Several pathologies were identified throughout the inspection, some of which require an immediate attention and rehabilitation solutions.

The most critical areas were:

– exterior columns;

– exterior beams at the base of the dome;

– connection hinges between the concrete dome and the rest of the

structure;

– columns supporting the central skylight.

•BUILDING’S PATHOLOGIES





Exterior columns (al. A) Severe rebar oxidation due to insufficient concrete cover in elements subjected to environmental agents.



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Exterior beams at the base of the dome (level 5) The expansion joints present anomalies due to environment effects, increased by the faulty water tightness of the dome’s lower panels.






Connection hinges between the concrete dome and the rest of the structure Disaggregation of unconfined concrete, placed afterwards to lock the nodes’ rotation after the dome’s completion.


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Columns supporting the central skylight Severe concrete deterioration and rebar oxidation on the columns upper and lower ends.





The load tests preformed during the inspection, allowed, not only to assess the structural integrity and determine the behaviour of the existing structure under the new loading, but also to calibrate the numerical models used in the structural design process.

•STATIC AND DYNAMIC LOAD TESTS

Cantilever load test Arena slab load test Dynamic load test


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Cantilever load test 3 load tests were preformed on the 2nd level radial cantilever beams in order to simulate the load from the new stands. The results confirmed the existing structure’s capacity to withstand the new imposed loads.






Arena slab load test Due to its key role on the renovation project, the arena slab was subjected to load testing under different configurations, namely, distributed and punching loads on different panels as well as linear and concentrated loads on beams. The results of these tests lead to the definition of strengthening solutions to the inner span of the radial beams.



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Dynamic load test Both ambient vibration tests and forced vibration tests were preformed, through which the most significant natural frequencies and damping coefficients were determined.





– Stand structure

• Strengthening the slabs

• Strengthening the foundations

– Suspension of technical grid

• Strengthening the dome

– Rehabilitation of reinforced concrete structure

STRUCTURAL INTERVENTIONS


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In order to accommodate the increased number of seating audience while providing a higher comfort, a new fixed stand was introduced in the renovation project.

The stands’ structural concept evolved through different solutions having in mind the structural optimization and minimization of the impact over the existing structure and of the respective retrofit.

•STAND STRUCTURE





Changing the loading by introducing new surcharges, point loads from the stand and the existence of penetrations in the slabs, led to the need to check the impact on the existing structure of all these modifications.

It was concluded that the slab could be maintained although there is need to retrofit locally and to introduce strengthening in beams.

•STRENGTHENING THE SLABS


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•STRENGTHENING THE SLABS





Due to the increased load in the arena slab and the reduced dimensions of the existing foundations, strengthening solutions were adopted. Furthermore, consequence of deepening the ground slab level, several existing foundations needed to be replaced by new ones at the new deeper level. A construction method had to be planned to support the loads during the execution.

•STRENGTHENING THE FOUNDATIONS


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The renovation project, with the objective of creating a multipurpose venue, previewed the installation of a technical grid, supported from the dome. Even though the grid itself does not make part of this project, support points were considered and a thorough study was carried out in order to assess the effect of the corresponding loads on the existing dome’s structure.

•SUSPENSION OF TECHNICAL GRID





As a dome, the roof structure of the pavilion, is highly susceptible to loads which are not uniformly distributed. Therefore, the installation of the grid and the respective loads, which may vary their intensity and position, forced to implement strengthening solution to the dome’s structure, in particular the lower parallel, and the top (closing) parallel.

•STRENGTHENING THE DOME


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The methods for the repair and protection of concrete structures detailed are grouped in 11 principles which relate to degradation of the concrete matrix or defects caused by reinforcement corrosion.

•REHABILITATION OF REINFORCED CONCRETE STRUCTURE





The rehabilitation methodology consisted in the definition of groups of activities, which are applied to the different structural elements depending on:

•REHABILITATION OF REINFORCED CONCRETE STRUCTURE

– type and extent of the pathology;

– environment to which the element is subjected;

– desired appearance when finished.


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CONCLUSIONS

– Proper maintenance is essential to ensure the designed lifetime;

– Unsatisfactory diagnosis and incorrect choice and application of rehabilitation product may lead to severe pathologies in the future;

– The proposed retrofit design and rehabilitation measures, based on this information, aimed fundamentally at extending the life of the reinforced concrete structure as well as to respond to the new proposed uses;

– The thorough knowledge of the existing structure’s condition and behaviour obtained from the exhaustive inspection plan carried out in the design phase, minimized the volume of demolition of existing structural elements, leading, not only to lower costs but also to the preservation of an important landmark to the city of Porto.




OBRIGADO


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Documents

construction of new

existing building

circular beams

conference rooms

radial beams meridians

way reinforced slabs

circular skylights

general twoway slabs