structural condition assessment of sans souci … · sans souci bathers pavilion 80818250 16...

Structural Condition Assessment Sans Souci Bathers Pavilion 80818250

16 February 2018 Cardno 1

STRUCTURAL CONDITION ASSESSMENT OF SANS SOUCI BATHERS PAVILION

Sans Souci Bathers Pavilion 80818250

Prepared for Georges River Council 16th February 2018



Contact Information

Cardno (NSW/ACT) Pty Ltd

ABN 95 001 145 035

Level 9, The Forum

203 Pacific Highway

St Leonards NSW 2065

Telephone: 02 9496 7700

Facsimile: 02 9439 5170

International: +61 2 9496 7700

[email protected]

www.cardno.com

Author(s):

Vesal Torabi (VT)

Remedial Engineer

Approved By:

Leo Meng (LM)

Remedial Team Leader

Document Information

Prepared for Georges River Council

Project Name Sans Souci Bathers Pavilion

80818250

File Reference 80818250_Structural Condition

Assessment of Sans Souci

Bathers Pavilion

Job Reference 80818250

Date 16 February 2018

Version Number 1

Effective Date 16th February 2018

Date Approved: 16th February 2018

Document History

Version Effective Date

Description of Revision Prepared by:

1 16.02.2018 Review Vesal Torabi



Table of Contents

1 Executive Summary 4

2 Introduction 6

3 Site Observations 7

4 Desktop Study and Recommendations 17

5 Risk and Conformance Issues 19

5.1 Risk Assessment 19

5.1.1 Consequence Criteria 19

19

5.1.2 Likelihood Criteria 20

20

5.1.3 Risk Matrix (combine Likelihood Vs Consequence) 20

5.1.4 Risk Assessment based on Existing Condition 21

6 Conclusion 22



1 Executive Summary

Cardno has been engaged to undertake a structural assessment of the bathers pavilion at Sans Souci. The

purpose of the structural assessment is to identify the structural risks and make suitable recommendations on

the required remedial works in order to maintain the longevity of the structure if possible. 3D imaging was

captured to better portray the condition of the existing building. This can be seen on the following link

https://my.matterport.com/show/?m=f7gTNgDihyA.

Suspended Concrete Roof Slab

The structural assessment on the suspended concrete roof was noted to have signs of concrete spalling and

moisture staining to the soffit. In general, the slab soffit was found to be in reasonably good condition in most

areas, however upon the completion of desktop study of the existing roof slab, it was noted that the current

design is not sufficient in withstanding a 5kPa live load as required by the Australian Standards for ‘areas

which are susceptible to overcrowding’. The followings observations were noted during our structural

assessment:

Condition/Risks

Structural strength review based on the calculations finds that the suspended concrete roof slab is

structurally inadequate to support the current requirements as stated by the Australian Standards. It

is our understanding that access onto the roof slab has been barricaded off to prevent human entry

into the area.

Concrete spalling was noted within some sections of the slab soffit as mentioned in Section 3 of this

report.

Moisture Staining was noted within some sections of the slab soffit as mentioned in Section 3 of this

report.

Overall, current the risk level is high for the suspended concrete roof slab. Our recommendations on the roof

slab are as summarised below:

Recommendations

Access onto the roof slab to be barricaded off immediately. (Which we believe has already occurred)

In order for the existing concrete roof slab to be accessible, significant strengthening is required.

Other Structural Elements Throughout Bathers Pavilion

The frame of Sans Souci Bathers Pavilion is in very poor condition, with significant signs of concrete spalling

within the entire structure. The following observations were noted during our structural assessment:

Condition/Risks

Significant concrete spalling was noted to all aspects of the building, including the concrete columns

and beams.

Internal non-load bearing walls were heavily dilapidated

Cracking was noted to areas of the slab on ground and tiled areas.

Significant concrete spalling was noted to the reinforced concrete lintels.

Overall, the current risk level is high for the structural frame of the building. Our recommendations are as

summarised below:

https://my.matterport.com/show/?m=f7gTNgDihyA



Recommendations

Due to the degree of severity of concrete spalling within the façade, it is possible that conventional

concrete spalling repair would deem more expensive than to demolish and rebuilding sections within

the façade.



2 Introduction

Cardno was commissioned to carry out the structural condition assessment of the bathers pavilion located at

Sans Souci. The purpose of the structural assessment is to identify the structural risk and making suitable

recommendations on the required remedial works in order to maintain the longevity of the structure if possible.

A visual site inspection was carried out by two suitably qualified structural engineers on the 6th February 2018.

Cardno carried out a slab scan to locate the existing steel reinforcement within the concrete members for our

desktop study. Cardno also carried out a 3D scan of the building to ensure that no defects were missed during

the inspection as well as providing the ability to present the overall condition of the structure in a

comprehensive manner to any persons of interest.

An aerial view of Sans Souci Bathers Pavilion is shown in Figure 2-1 below.

Figure 2-1 Aerial View of Sans Souci Bathers Pavilion (Google Images)



3 Site Observations

Based on our visual inspection on 7th February 2018, the main issues noted at The Bathers Pavilion includes severe concrete spalling, extremely corroded/deteriorated reinforcement and staining to both the internal and external walls. A selection of photos are shown below:

ITEM

Bathers Pavilion

Suspended Concrete Roof Slab Soffit

Extensive concrete spalling and severe corrosion to the reinforcing bars

Photo 1

Suspended Concrete Roof Slab Soffit

Typical extensive spalling to roof slab

Photo 2



Concrete Beams

Significant concrete spalling and corrosion to the concrete beams.

Photo 3

Concrete Beams

Typical extensive concrete spalling to the concrete beams.

Photo 4



Concrete Columns

Significant concrete spalling and loss of cross-sectional area to the concrete columns.

Photo 5

Concrete Columns

Further evidence of extensive deterioration to concrete columns as well as exposed and corroded reinforcement.

Photo 6



Concrete Lintels Extensive concrete spalling was noted to the lintels as shown below.

Photo 7

Concrete Lintels Typical concrete spalling to lintels. Large cracks were also noted throughout the entirety of the building.

Photo 8



Cantilevered Concrete Roof Slab

Extensive concrete spalling to the cantilevered sections of the concrete roof slab as shown below. Substantial flaking of paint and bubbling was also noted across the entire building.

Photo 9

Cantilevered Concrete Roof Slab

Further evidence of the concrete spalling to the slab soffit.

Photo 10



Brick Walls

Large cracks exceeding 3mm in width were noted to several walls within the building.

Photo 11

Brick Walls

The photo below shows a general overview photo the current condition of the walls.

Photo 12



Brick Walls

Large cracks within the brick walls of the building.

Photo 13

Brick Walls

Significant cracking to internal walls.

Photo 14



Façade

Significant cracking and staining to the southern façade.

Photo 15

Facade

Extensive concrete spalling to the southern façade. Large amounts of flaking paint was also noted to all facades.

Photo 16



Electrical Switch Room

Significant cracking and concrete spalling was noted to the brick walls and concrete lintels.

Photo 17


Typical cracking throughout the building facades.

Photo 18




Severe cracking to roof slab of electrical switch room

Photo 19


Further evidence of cracking to the concrete roof.

Photo 20



4 Desktop Study and Recommendations

Desktop Study on Suspended Concrete Roof Slab Cardno carried out detailed measurements of the structural components of the building to determine whether the suspended concrete roof slab was capable of withstanding a live load of 5kPa as stated in AS 1170.1 -2002 (Permanent, imposed and other actions) . In the desktop study, 100% steel utilisation was assumed for the purpose of this report. Analysis of the design showed that the roof slab is structurally inadequate to support the current requirements and that this area should be immediately barricaded off to prevent human entry as this area serves as a potential of serious injury. We believe this area has already been closed off. Below shows the typical layout structure of the building frame which was used for the desktop study of the suspended concrete roof slab.

Figure 4-1

Upon inspection of the structural components of the building, significant concrete spalling was noted throughout the entire building. This concrete spalling was evident within the concrete beams, columns and roof slab. Significant amounts of concrete spalling leads to a loss of steel utilisation as well as a decrease in the cross sectional area of the concrete columns and beams, leading to a loss of strength and possibility of sudden collapse. To adhere to the Australian Standards, significant strengthening is required and taking into consideration the overall condition of the building, this exercise would deem very expensive and impractical



Recommendations: Conventional concrete spalling repair comprises of wire brushing cleaning corroded reinforcing bars. If a bar is found to have lost at least 20% of its cross-sectional area, new bars are to be lapped with the existing to provide the sufficient strength required. Considering the significant amount of corroded steel throughout the entire building it is highly likely that this corrosion has extended even further than what can be inspected visually alone. It is possible that the steel has corroded in areas which the concrete has not been displaced. Therefore, it is very difficult to control the extent of the repair and the repair cost. The roof slab requires significant strengthening, structural components within the building require large quantities of concrete spalling repair and sections within the façade need to be rebuilt. Due to these reason, it is our opinion that demolishing and rebuilding would be the more cost-effective solution.



5 Risk and Conformance Issues

5.1 Risk Assessment

A risk assessment has been performed based on the current condition of Bather Pavilion. The risk

assessment criteria is shown 5.1.1 to 5.1.3 below.

5.1.1 Consequence Criteria

Figure 5-1



5.1.2 Likelihood Criteria

Figure 5-2

5.1.3 Risk Matrix (combine Likelihood Vs Consequence)

Consequence

L

ike

lih

oo

d

Insignificant Minor Moderate Major Catastrophic Almost Certain

Medium (11)

High (16)

Extreme (20)

Extreme (23)

Extreme (25) A

Likely Medium (7)

High (12)

High (17)

Extreme (21)

Extreme (24) B

Possible Low (4)

Medium (8)

High (13)

High (18)

Extreme (22) C

Unlikely Low (2)

Low (5)

Medium (9)

High (14)

High (19) D

Rare Low (1)

Low (3)

Low (6)

Medium (10)

High (15) E

1 2 3 4 5

Figure 5-3



5.1.4 Risk Assessment based on Existing Condition

The outcome of the risk assessment based on current condition is shown in the table below.

Risk Assessment – Current Condition

Component Element Likelihood Consequence Risk

rating

Bathers Pavilion

Electrical Switch Room Possible Moderate High

Suspended Concrete Slab Likely Major Extreme

Concrete Beams Possible Moderate High

Concrete Columns Possible Moderate High

Concrete Lintels Possible Moderate High



6 Conclusion

Based on our inspection and desktop study, Bathers Pavilion is in very poor condition overall and has a high level of risk due to its current condition. Significant concrete spalling is apparent throughout the concrete beams, columns and roof slab. The roof slab requires significant strengthening, structural components within the building require large quantities of concrete spalling repair and sections within the façade need to be rebuilt. Due to these reason, it is our opinion that demolishing and rebuilding would be the more cost-effective solution.

A detailed 3D walk through of the building can be seen on the following link -https://my.matterport.com/show/?m=f7gTNgDihyA.

https://my.matterport.com/show/?m=f7gTNgDihyA

structural condition assessment of sans souci … · sans souci bathers pavilion 80818250 16...

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