Grounds publishedDecided 17 Apr 2009

Contents

High Court · Decided 17 April 2009

Jurong Town Corp v Sembcorp Engineers and Constructors Pte Ltd

Feedback & support

[2009] SGHC 93Case no. Suit 44/2006

What happened, in plain English

There is no plain-English summary of this judgment yet.

Ask about this judgment

Grounds of decision

Official text from eLitigation

I.
Background Facts
II.
Legal / Factual Issues
A.
SEC's Obligations
B.
SEC's Breach and Resultant Damage
C.
SEC's Defence
D.
Key Issues
III.
SEC'S Obligations
A.
Fitness for Purpose
i.
Whether SEC had an obligation to ensure that the steel stiffeners were fit for their intended purposes
ii.
The purpose for which the steel stiffeners were intended
a.
Serviceability
b.
Expansion of bricks
c.
Brick walls did not have movement joints
B.
Equivalence / Design / Construction
i.
JTC's Position
ii.
SEC's Defence
IV.
SEC'S Breaches
A.
Design
i.
Sections 5.7 and 2.4.2 of BS5950-5 : Deflection
a.
Deflection limit to be complied with - JTC's position
b.
Deflection limit to be complied with - SEC's Position
1.
Vertical Deflection
2.
Horizontal Deflection
c.
Compliance of the steel stiffeners with deflection limits
1.
External Wall in the SS 2000 series
2.
#03-12 Elevation 1 External Wall
3.
#03-12 Internal Wall
4.
Page 335 of Jones’ 1st AEIC
5.
7m by 10m theoretical wall panel
ii.
Section 5.6 of BS 5950-5: Lateral Buckling
iii.
Section 5.9 of BS 5950-5: Effects of Torsion
iv.
Effects of warping torsion increasing the torsional capacity
v.
Section 6.2 of BS 5950-5: Flexural Buckling
a.
Applicability of Section 6.2.2
b.
Whether the maximum slenderness of the H1-250 and H1-300 exceeded the limit specified in section 6.2.2 of BS 5950-5
c.
Whether the maximum slenderness for H1-250 and H1-300 would still be non-compliant with code requirements if section 4.2 of BS 5950-5 was applied
B.
Construction and Workmanship
i.
Defects observed after stiffeners were exposed
a.
Incomplete stiffeners
b.
No stub to connect the steel stiffeners
c.
Uneven support
d.
Welding
1.
Welding between flange and web
2.
Welding at end connections
3.
Welding to join two web plates
C.
Stiffeners were Unfit
i.
Steel stiffeners caused defects
a.
How the steel stiffeners caused the defects on site: Dr Ting’s opinion
1.
Stiffeners prone to excessive deflection under lateral load
(i)
Wind load was considered
(ii)
Excessive deflections under wind load
(iii)
Wind speed
(iv)
Consequences
2.
Horizontal steel stiffeners also had the propensity to side-sway
(i)
Dr Chiew’s test results
3.
Stiffeners had low torsional capacity and were prone to twisting
(i)
Was there some rotation / twist / torsion?
(ii)
Horizontal steel stiffeners had low torsional capacity
4.
Poor construction of steel stiffeners aggravated the deformation
b.
How the Steel Stiffeners caused the Defects on Site: Jones' Opinion
1.
Steel stiffeners would fail due to compressive loads
(i)
Movement capability rejected by JTC
(ii)
Wind load was secondary for being a transient load
2.
Steel stiffeners slender and prone to side-sway
3.
Steel stiffeners weak under compression
c.
Steel Stiffeners would have failed with vertical movement of 2.7 mm
1.
Vertical steel stiffeners would have failed with vertical movement of 1.7 mm
2.
Horizontal steel stiffeners would have failed with vertical movement of 2.7 mm
(i)
Question of whether steel stiffeners were fit for purpose
3.
Some accommodation of the vertical movement of 2.7 mm
(i)
Capacity of brick wall was sufficient
(a).
Axial stress limit was reduced by Jones
(b).
Brickwork had greater capacity than that calculated by Jones
(1)
Slenderness ratio of the brick wall was exceeded
(I)
Effective thickness of the brick wall
(II)
Effective height of the brick wall
(III)
Capacity reduction factor should be increased
(IV)
Conclusion
ii.
Other alleged causes for the defects
a.
Were the defects caused by the absence of movement joints?
1.
If movement joints were provided, defects in the vertical steel stiffeners would still have occurred
2.
If r.c. had been used, no defects would have been observed
b.
Defects were not caused by slenderness of the brick walls (re paragraph 18(b) of the Defence)
c.
Defects were not caused by fair wear and tear and/or lack of maintenance of the brick walls (re paragraph 18(c) of the Defence)
d.
Defects were not caused by weakness in the building structure
1.
Alleged rotational effect of building structure
2.
Horizontal cracks in columns not indications of structural inadequacy
3.
Alleged “soft column”
D.
R.c. Stiffeners Better Than Steel
i.
No fully developed r.c. design
a.
JTC would have constructed on basis of a fully-developed r.c. stiffener design
1.
No design requirements for r.c. given
(i)
JTC intended end conditions of r.c. stiffeners to be fixed
b.
Sketches were not meant for use in brick walls generally
ii.
Steel vs r.c.
a.
R.c. stiffeners would perform better than steel stiffeners under lateral load
1.
Composite analysis of deflection
2.
End conditions of the stiffeners
(i)
Experts agreed that steel stiffeners had pinned end conditions
(ii)
Dispute as to end conditions of r.c. stiffeners
(iii)
Jones disagreed that r.c. end conditions would be fixed-fixed
(iv)
Sketch of r.c. stiffeners were not only buildable, but also code-compliant
b.
R.c. would perform better than steel under compression/axial load (packing case)
c.
R.c. better than steel in the characteristics set out in Tables 1 to 5 of D-29
1.
Tables 1 and 2, page 21, D-29
(i)
Discussion on cracking
(ii)
Under lateral load
(iii)
Under vertical load
2.
Table 3, page 22, D-29
d.
R.c. better than steel as it would not have twisted / side-swayed
e.
R.c. structure would attract less load under creep and shrinkage
iii.
What if r.c.?
a.
R.c. would deflect less than steel under lateral load
b.
R.c. would be fine under compression
c.
With r.c., rectification works would have been simpler and cheaper
d.
Defects in question would not have arisen if r.c. stiffeners were not substituted with steel stiffeners
iv.
Allegation of defects at locations even with r.c. stiffeners
a.
At SS1000 units
b.
At SS2000 units
c.
Plaster cracks at staircases due to differential loading
E.
Conclusion
I. Background Facts
[1] The plaintiff ("JTC") is the developer and owner of Woodlands Spectrum I ("Development"), which comprises some 17 blocks of 9-storey stack-up factories. The defendant ("SEC") was the main contractor for the Development under a contract dated 21 September 1998 ("Contract").
[2] The Contract originally provided for the use of reinforced concrete ("r.c.") lintels/stiffeners for the brick walls in the Development. In the course of the Contract, SEC proposed to substitute steel lintels/stiffeners for r.c. lintels/stiffeners. JTC was amenable to that proposal. The term "stiffeners" is used in this judgment to refer generally to the lintels/stiffeners, which are not structural elements but fulfil the function of supporting and strengthening the walls. Stiffeners can be both horizontal and vertical. Lintels are horizontal beams built into the wall at the top of openings. Stiffeners can also be "lintels".
[3] SEC engaged Dyntek Pte Ltd ("Dyntek") as its sub-contractor to design and construct the steel stiffeners. As between JTC and SEC, the design of the steel stiffeners was SEC's responsibility. The design was undertaken by Dyntek and its engineering consultants WP Brown. Mr Gary Wyatt (“Wyatt”) of WP Brown, a Professional Engineer ("PE"), endorsed the design.
[4] The Development was substantially completed in or around March 2000, but defects were observed thereafter at certain brick wall locations.
[6] By a direction made on 27 April 2007, the proceedings were bifurcated. Liability was to be determined first, and issues of quantum deferred to a later stage.
II. Legal / Factual Issues
A. SEC's Obligations
[7] The obligations of a contractor who undertakes both the design and construction of particular works are well settled:
i.
Hudson's Building and Engineering Contracts, at paragraph 4.066:
A contractor undertaking to do work and supply materials impliedly undertakes…that both the workmanship and materials will be reasonably fit for the purpose for which they are required, unless the circumstances of the contract are such as to exclude any such obligation.
ii.
Construction Law in Singapore and Malaysia, at page 72:
A contractor undertaking a design responsibility warrants (as a question of fact rather than of law) that, where the purpose of the required construction has been adequately communicated to and accepted by him, the design will be fit for that purpose.
iii.
MCST Plan No 1166 v Chubb Singapore Pte Ltd [1999] 3 SLR 540 at paragraph 60:
It is settled law that according to the principles of the common law, in a pure contract for work and materials the following warranties will be implied into it:
(a) that the materials used will be of good quality (equivalent to merchantable quality in sale or supply of goods contracts);
(b) that the materials are reasonably fit for the purpose for which they are used (equivalent to fitness of purpose of purchase in sale or supply of goods contracts).
iv.
Gema Metal Ceilings v Iwatani Techno Construction [2000] SGHC 37 - the Court found at [69] that the plaintiffs were responsible to the defendants not only for the supply of materials but also design (of the metal ceiling system for the Kuala Lumpur International Airport) and held at [70] that:
The plaintiffs were aware of the requirements and specifications of the KLIA Project, and must be taken to have agreed to design a ceiling system which met those requirements.
[8] Applying these well established principles to the present case, I found that SEC’s obligations under the Contract were to ensure:
i.
The suitability, adequacy, integrity, durability and practicality of the design of the steel stiffeners that SEC had proposed for substitution for the r.c. stiffeners;
ii.
That the steel stiffeners it proposed were fit for the purposes for which they were intended;
iii.
That the steel stiffeners were to be equal to or better than the r.c. stiffeners originally required under the Contract;
iv.
That SEC would use all reasonable skill, care and diligence in the design of the steel stiffeners; and
v.
That SEC would also construct the steel stiffeners using all reasonable skill, care and diligence and in a good workmanlike manner.
B. SEC's Breach and Resultant Damage
[9] After careful consideration, I found on the evidence that SEC had breached its obligations in that:
i.
the design of the steel stiffeners was lacking in suitability, adequacy, integrity, durability and practicality;
ii.
the steel stiffeners were not fit for the purposes for which they were intended;
iii.
the steel stiffeners were not equal to or better than the r.c. stiffeners originally required under the Contract;
iv.
the steel stiffeners were not designed with reasonable skill, care and diligence; and
v.
the steel stiffeners were not constructed with reasonable skill, care and diligence and in a good and workmanlike manner.
[10] The steel stiffeners failed to support and strengthen the brick walls and were themselves deformed. In the circumstances, I found that JTC was entitled to rely on the principle of res ipsa loquitur - it was for SEC to justify the design and construction of the steel stiffeners, their fitness for purpose, and that they were at least equivalent to the r.c. stiffeners originally required. SEC had failed to do so.
C. SEC's Defence
[11] SEC denied the obligations and breaches asserted by JTC. SEC sought to defend its design and construction of the steel stiffeners. It asserted that the defects in question were not caused by or attributable to the design or construction of the steel stiffeners, on the basis that:
i.
SEC's proposal to use steel stiffeners only resulted in a substitution of the material used for the stiffeners, but the other aspects of the walls remained as designed by JTC;
ii.
the steel stiffeners were approved and accepted by JTC and JTC’s Superintending Officers ("SO");
iii.
JTC, its officers and employees did, as SO, exercise independent judgment in making decisions relating to the design and specifications of the Development, including those associated with the steel stiffeners. With the inputs from JTC on the design of the steel stiffeners and with JTC’s rigorous checking and approval system for the design, JTC had therefore placed little reliance, if any, on SEC with regard to the design of the steel stiffeners;
iv.
in some areas where SEC alleged that r.c. stiffeners were installed, the walls had also bulged or cracked, evidencing that the problem lay with the design of the entire Development, rather than the design of the steel stiffeners;
v.
SEC had executed and completed the Works "to the satisfaction of the Superintending Officer" as required under the Contract, and the SO had certified substantial completion of the Development on 8 March 2000 and issued the Final Completion Certificate on 31 October 2002; and
vi.
the reports of Dr Chiew Sing Ping ("Dr Chiew") from Nanyang Technological University ("NTU"), and WP Brown evidenced that the steel stiffeners installed were sufficient to carry the design load of the Development.
vii.
the fact that the defects surfaced some 4 years after construction indicated that the causes were time dependent. The loads due to the weight of the brick wall above were present even before the brick walls were plastered and hence were not time dependent, whereas the effects of creep and shrinkage of the r.c concrete structure were time dependent, and these, according to the SEC, imposed additional loads on the steel stiffeners and were therefore the cause of the defects. Apart from these effects due to creep and shrinkage, another shortcoming was the slender brick infill walls.
[12] SEC asserted that the defects in Schedule 1 of the Statement of Claim "could be caused by and/or attributable to and/or contributed by factors which were not within the purview or responsibility" of SEC, for instance:
i.
the Contract did not specify or require movement joints at the underside of the structure where the external brickwork infill walls and stiffeners abut;
ii.
the thickness specified for the external wall in the Contract was inadequate for the height of the external wall; and
iii.
fair wear and tear and/or lack of maintenance of the external walls in the Development.
[13] SEC contended that the steel stiffeners were fit for their intended purpose, which was only to support the weight of the brick walls. The brick walls, not being structural components of the Development, were not expected to take additional loads from either the structure or the expansion of the brick walls. This assertion was set out repeatedly in SEC's closing submissions, for instance:
At [65]:
At [466]:
[14] SEC submitted that its design duties in the present case ought to be limited to the design of the steel stiffeners which would fulfil their intended function if they did not deform and/or fail under the weight of the brick wall sitting immediately above the horizontal steel stiffeners. Since the brick walls were generally not intended to be load-bearing in a typical building, the additional loads imposed by the interaction of the parts of the Development designed by the plaintiff and the brick walls could not be expected to the accommodated by SEC’s design of the of the steel stiffeners unless the presence of these loads had been specifically communicated to it, which was not the case. Since JTC had not provided SEC with the design calculations or the basis for design of the overall structure of the entire Development, there was no basis for JTC to make any assumptions concerning the additional loads which would be imposed on the brick walls due to the creep and shrinkage of the concrete as well as the expansion of the brick walls. SEC submitted that in the circumstances, it was reasonable for SEC to assume that the brick walls in the Development could be treated as non load-bearing walls.
D. Key Issues
[15] The key issues in this case were largely factual and technical in nature:
i.
whether the steel stiffeners were fit for their purpose;
ii.
whether the steel stiffeners were equal to or better than the r.c. stiffeners originally required;
iii.
whether there was negligence in the design and construction of the steel lintels/stiffeners; and
iv.
whether the defects observed at areas with steel lintels/stiffeners were caused by and/or attributable to the design or construction of the steel lintels/stiffeners.
[16] A subsidiary issue raised by SEC concerned SEC’s own characterisation of JTC’s pleaded case that the steel stiffeners were the sole cause of the defects observed at the Development and that that was the case JTC had to prove. According to counsel for SEC, JTC’s case should be dismissed “if any distress on site is attributable to the absence of the movement joints", even if the steel stiffeners were defective. I agreed with JTC’s submission that it could not be the law that a cause should be the “sole cause” in order for liability to be established. In any event, I did not think that SEC had correctly characterised JTC’s case as had been pleaded by JTC.
[17] On the whole, I agreed with the submissions of counsel for JTC. Accordingly, I adopted a large part of JTC counsel’s well thought out and structured submissions, which included a careful analysis of the evidence (ably assisted by its expert) on many points in this judgment. I had earlier directed both counsel to ensure that the respective experts assist in the preparation of their closing submissions as this case involved very technical engineering considerations. I would like also to place on record my appreciation for the voluminous amount of extra work that both experts had to do in the course of the trial in order to assist the court to better understand the various technical issues raised in respect of the cause of the defects found at the Development.
III. SEC'S Obligations
A. Fitness for Purpose
i. Whether SEC had an obligation to ensure that the steel stiffeners were fit for their intended purposes
[18] SEC contended that an obligation to ensure that the steel stiffeners were fit for the purposes for which they were intended did not arise in this case as JTC did not rely upon SEC's skill and judgment for the same. SEC said that JTC was independently advised on the steel stiffeners, as evidenced by JTC's approval of SEC's submissions on the steel stiffeners.
[19] In my judgment, any approval/acceptance of the steel stiffeners by JTC or the SO under the Contract would not relieve SEC of its own obligation to ensure that the steel stiffeners were fit for the purposes for which they were intended. In particular, clause 66 of the Standard Preliminaries for Construction Works provided that "acceptance of any substitution shall in no way relieve the Contractor of any of his responsibilities for compliance with all the requirements of the Contract". Further, clause 6.1 of the conditions of Contract stipulated (in relation to works designed by SEC) that: "he [i.e. SEC] shall be fully responsible for the suitability, adequacy, integrity, durability and practicality of the design as set out in the Drawings [etc] submitted for the acceptance of the Superintending Officer…". Clause 6.2 of the Conditions expressly stated that "Acceptance by the Superintending Officer of such submission shall not relieve or in any way limit the responsibility of the Contractor under Clause 6.1."
[20] As regards the Superintending Officer:
i.
Clause 2.1(2) of the conditions of Contract stipulated that "Except as expressly stated in the Contract, the Superintending Officer shall have no authority to relieve the Contractor of any of his obligations under the Contract";
ii.
Clause 19 of the Standard Preliminaries stipulated that "He [the SO Rep] shall have no authority to relieve the Contractor of any of his duties or obligations under the Contract".
[21] In view of the Contract terms highlighted above, I agreed entirely with the submission of counsel for JTC that SEC's reliance on the alleged independent judgment and decision making by JTC or its officers and employees to relieve itself of its own responsibilities under the Contract was entirely misplaced.
[22] In any event, it was clear to me that the steel lintels/stiffeners were not designed by JTC, but by SEC and/or its subcontractor Dyntek. Further, there was clear reliance by JTC's "officers and employees" -- whom SEC identified as Mr Koh Cheng Hui, Mr Ng Eng Gim Gary ("Gary Ng") and Mr Tong King Yii ("Tong") -- on SEC to provide a stiffener system that was fit for its intended purpose.
[23] In its particulars, SEC had specifically relied on 2 documents as evidence of the exercise of independent judgment and decisions made by JTC, namely:
i.
submission for approval made on 25 September 1998 dated 10 October 1998 (ref: JTC/STRUC/037A) in relation to "stiffeners and tie beams" from Dyntek - responded to by Tong on 10 October 1998; and
ii.
submission for approval dated 16 April 1999 (ref: JTC/STRUCT/055) in relation to "revised shopdrawing for Dyntek [stiffeners]" - responded to by Gary Ng on the same day.
[24] On the evidence, I found that neither Tong nor Gary Ng considered it their responsibility to review or approve alternative designs of the steel stiffeners. On the contrary, they relied on the PE designing the steel stiffeners (i.e. Wyatt) to ensure that the steel stiffeners were suitable and/or fit for their intended purposes.
[25] Tong’s response to SEC’s submission for approval JTC/STRUC/037A in relation to "stiffeners and tie beams" from Dyntek was as follows:
[26] Tong, himself an architect, was in any case in no position to evaluate the proposed steel stiffeners from an engineer's perspective. In any event, it was Tong’s position that it was SEC's responsibility to ensure that the steel stiffener design was in fact verified by a PE (in this case, Wyatt of WP Brown, who endorsed the steel stiffener design). Indeed, SEC itself had acknowledged at [50] of its closing submissions that any review by Tong would be "from an architectural point of view".
[27] With regards to the submission for approval dated 16 April 1999 (ref: JTC/STRUCT/055), Gary Ng stated that on or about 15 April 1999 he received a drawing entitled "typical connection details (100mm walls)", endorsed by Wyatt as PE. Parts of the drawing were clouded, with the comments "IF GAP GREATER THAN 40mm PROVIDE FULL LENGTH SITE WELD TO TOP & BOTH SIDES" and "IF GAP GREATER THAN 40mm PROVIDE FULL LENGTH SITE WELD TO ALL FOUR FACES". These being the parts highlighted to Gary for his attention, they were the only aspects which he reviewed. His comments, "Approved, pse give us endorsed calculations & drawings" applied only in respect of the welding details proposed. Like Tong, Gary Ng relied on SEC's design, as endorsed by their sub-contractors' consultant engineer.
[28] According to Gary Ng, the JTC/STRUCT/055 submission was submitted by SEC to regularise the paperwork in respect of his comment on this drawing.
[29] The contemporaneous documents (namely, a fax from Dyntek to Mr Sim Beng Kiat (“Sim”) (an ex-Project Manager of SEC) and Mr Chia dated 16 April 1999) also showed that Gary Ng's approval was understood by SEC and Dyntek to be in relation to intermittent welding, rather than the steel lintel/stiffener design as a whole.
[30] From the totality of the evidence, I found that at all times it was SEC's obligation (not JTC’s obligation) to ensure that the steel stiffeners were suitable and/or fit for their intended purposes regardless of any approval by JTC. SEC could not rely on its submissions of approval to JTC to relieve itself of its own obligation to ensure that the steel stiffeners were fit for their intended purpose. There was clear evidence (particularly from the testimony of Gary Ng and Tong as well as their responses to the submissions for approval cited by SEC in its closing submissions, which I do not find it necessary to set out in this judgment) that JTC was relying wholly on SEC, having undertaken both the design and construction of the steel stiffeners that it had proposed to JTC as substitution for the r.c. stiffeners, to provide a steel stiffener design that was suitable and/or fit for its intended purpose. Hence, JTC required that such design be endorsed by a PE. Accordingly, I rejected any suggestion from SEC that JTC had not placed reliance on SEC for the whole design and installation of the steel stiffeners proposed by SEC in substitution for the r.c. stiffeners.
[31] I noted that Mr Ng Wee Beng, a director of Dyntek, had testified that he "expected Mr Wyatt, as PE to come up with a design that is fit for the walls in question". Indeed, Ng Wee Beng made clear that Dyntek relied on WP Brown to design the stiffeners to be used for the Development as well as the end connections and that Dyntek would not check the calculations. In this regard, he said:
[32] While Wyatt disagreed that the steel stiffeners were not fit for their purpose, he had not, at any point, contended that there was no obligation on him to design stiffeners that were suitable and/or fit for their intended purpose. Neither did he suggest that it was JTC's obligation to ensure the same.
[33] JTC's spacing requirements of the stiffener system for the brick walls were for a vertical stiffener to be placed at every 5 m length and horizontal stiffeners to be placed at every 3.5 m height and Wyatt had understood these to be the "maximum acceptable dimensions". Wyatt did not execute a standard design for the steel stiffeners based on these wall dimensions. Rather, his "design was always done for the specific loading conditions that were applicable". Indeed, he exercised his own judgment in determining whether horizontal steel stiffeners were required even if JTC spacing requirements were exceeded. Without seeking JTC’s concurrence to exceed the nominal 3.5m x 5 m spacing, Wyatt in fact took the position that no stiffener was necessary for certain walls of 3.6m, 3.62m and 3.9m heights at the SS 1000 series of the Development. In the circumstances, I found that Wyatt had undertaken design responsibility for the steel stiffeners.
[34] Accordingly, I accepted the submission of JTC’s counsel that SEC was, in fact and in law, obliged to ensure that the steel stiffeners were suitable and/or fit for their intended purpose. Further, on the evidence I found that there was clear reliance by JTC (and its officers and employees) on SEC (and its PE) to provide the alternative steel stiffener system that was fit for its intended purpose. The design responsibility was in fact undertaken by Wyatt for SEC.
ii. The purpose for which the steel stiffeners were intended
[35] SEC's witnesses, Wyatt and Mr Phillip J. Jones (“Jones”), the expert witness for SEC, acknowledged that a stiffener system should prevent lateral buckling of a brick wall i.e. ensure wall stability. This was necessarily premised on both the vertical and horizontal stiffeners having greater lateral stiffness than the brick wall. The design of the stiffener system thus had to cater for all lateral forces including those from wind loads. Wyatt himself admitted in his evidence that he did design the stiffeners to withstand wind loads. I thus rejected the submission from SEC that JTC did not require the stiffeners to carry wind loads. That submission was without evidential basis.
[36] In addition to providing lateral restraint to the brick wall, the stiffeners would also need to be able to withstand the weight of the brick wall above the horizontal stiffeners (taking into account the various loads acting upon the stiffeners). At a minimum, the stiffeners should not unacceptably deflect or deform (let alone fail) after being sandwiched between the lower brick wall and the brick wall above and incorporated as part of the wall. JTC required the stiffeners to bear the vertical load even if the brick walls below were removed. Hence, the steel stiffeners were to be "load-bearing". JTC thus required the horizontal stiffeners to be able to function as beams should the brick walls below them be removed and also as typical brick wall stiffeners sandwiched between the upper and lower brick walls.
[37] Sim (SEC’s then project manager), Ng Wee Beng (Dyntek) and Wyatt all acknowledged this in their evidence.
[38] In essence, therefore, besides providing lateral stability to the brick walls, the horizontal stiffeners should be able to function as beams, transferring the weight of the brick wall above it to the support at the two ends, which could be columns (if they were sufficiently near) or vertical stiffeners.
[39] Self-evidently, the steel stiffeners could not be considered to work if they could only carry the “design load of the brickwalls (sic) of the Development”- a pure theoretical construct - but not the actual loads.
[40] Accordingly, I rejected SEC’s contention that the purpose of the horizontal steel stiffeners was only to carry the weight of the brick wall above it. SEC itself admitted at paragraph 23(b) of its closing submissions that "the purposes of stiffeners and / or lintels is to stiffen the brickwalls within which they are installed". To serve the purpose of stiffening the brick wall within which the stiffeners were installed, the stiffeners had to adequately stiffen the actual walls, bearing both vertical and lateral loads, besides being able to carry the weight of the brick wall above it. I noted the evidence of the following witnesses, which showed that the purpose of the steel stiffener was not simply and solely to carry the weight of the brick wall immediately above it:
i.
The evidence of Dr Ting Seng Kiong (“Dr Ting”), the expert for JTC, that stiffeners "fulfil the function of supporting walls (typically brick walls)";
ii.
Gary Ng’s evidence that stiffeners were "required to make the wall 'stiffer'"; and
iii.
Tong’s evidence that the purpose of a stiffener / lintel was "[t]o stiffen the brick wall to make sure that it's stable".
[41] I accepted JTC’s submission that SEC was effectively seeking to sustain the unreal position that the steel stiffeners were fit for their purpose as long as they worked in theory to support a free standing wall isolated from the building within which they were found (as if the weight of the brick wall was the only possible load on the steel stiffeners), even if in fact such steel stiffeners when installed on site, would unacceptably deform and cause damage to the wall finishes when subjected to the actual lateral and vertical loads.
a. Serviceability
[42] First, it was clearly insufficient that the stiffeners merely had sufficient strength to carry the load (design load or otherwise). For a stiffener to work, it should be able to carry the load without unacceptable deformation or deflection. Otherwise, there would be damage to the wall.
[43] Dr Chiew, the expert witness called by the JTC, put it pithily:
[44] Any suggestion that the stiffeners remained fit for their purpose as long as they were strong enough to carry the load of the brick walls, even if the stiffeners would themselves deform (by buckling, twisting or side-sway) and the wall finishes would be damaged would certainly be contrary to all common sense and reason.
[45] Indeed, when considering the deflection limits that were acceptable to him, Jones, the expert called by SEC himself highlighted that the "deflection should not be so great as to cause damage to the applied finishes".
b. Expansion of bricks
[46] Second, the stiffeners were intended to be installed in brick walls. The designer for the brick wall stiffeners ought to know that bricks would expand over time and hence, ought to have factored that into the design. As such, in designing the stiffeners, any additional loads / stresses that might be imposed on the stiffeners as a result of such brick expansion had to be accounted for.
[47] Wyatt acknowledged both the fact that “bricks grow” and that additional stresses arising from such brick expansion would result. But he simply dismissed these effects on the basis that “if you isolate the brickwork from the structure, then you also achieve relieving these stresses due to brick growth”.
[48] If this was in fact a cause of the defects, I could not see how that would absolve SEC of liability, when its design of the steel stiffeners failed to account for the additional compressive stresses on the brick work resulting from this known phenomenon of brick expansion.
[49] Indeed, on Jones’ own account, expansion of the brick work accounted for more than 70% of the total differential movement of 2.7 mm of the r.c. structure and the brick work in a 3.05 m high brick wall. At page 237 of D-29, the total movement was broken down as follows:
i.
shrinkage and creep of concrete (after 6 years) = 0.79 mm
ii.
moisture movement of brick work = 1.53 mm; and
iii.
thermal movement of brick work = 0.38 mm.
[50] I agreed with the submission of counsel for JTC that it was no excuse to say that SEC could not have accounted for such brick expansion as it had no knowledge as to the assumptions made in the design of the overall structure. Even if (for the sake of analysis) the structure were ignored, Wyatt was still fully aware of the dimensions of the brick panels. More fundamentally, SEC could well have chosen not to substitute the r.c. stiffeners with steel stiffeners if SEC was not in a position to provide a steel stiffener system that worked.
[51] Indeed, it was noteworthy that Dyntek itself understood that the onus was on Wyatt to raise questions if more information was required in the design of the steel stiffeners. Ng Wee Beng had testified in this regard that if additional information was required to provide a good design, it was for WP Brown to ask all the necessary questions.
COURT:
I'm saying about sufficiency of design. I'm not saying about agreement or anything; I'm saying about sufficiency of design, that he fails to ask any question that would be relevant to him providing a good design, and he puts his chop there, as far as you and WP Brown is concerned --
A.
Of course. That is his responsibility, to ask --
COURT:
Ask all the necessary questions?
A.
I believe that should be the way.
c. Brick walls did not have movement joints
[52] As a corollary, it was similarly no excuse for SEC to say that the installation of movement joints would have accommodated the compressive stresses from the movement in the r.c. structure and the brickwork and prevented the defects that were seen on the Development.
[53] It was not JTC's case that the lack of movement joints was a cause of the defects on site. If however, it were to be found to be a cause, then JTC’s position was that SEC should not be absolved of liability for the failure of its steel stiffeners to accommodate such additional stresses resulting due to the lack of movement joints.
[54] Wyatt was well aware that the brick walls in the Development would not have movement joints when he undertook the design of the steel stiffener system. It was for him to design a steel stiffener system that worked for such walls, and not to design steel stiffeners that required the provision of movement joints to work when he knew full well that these were not installed on site! I agreed with the submission of counsel for JTC that SEC was effectively asking to be absolved of liability for designing stiffeners that were doomed to fail. SEC’s position was that the steel stiffeners were not designed to work without movement joints even though it knew, before design of the steel stiffener system commenced, that no movement joints were to be provided by JTC. This position was, quite clearly, untenable.
[55] In fact, Wyatt conceded that if he had foreseen the compressive loads induced in the brick work, he would have provided for horizontal compressive joints.
[57] This was consistent with Tong's evidence that it was "usual practice" that a contractor would fill the gap between the brick wall and the underside of the beam with mortar, and this served as the expansion joint.
[58] Dr Ting opined the same in paragraph 8.1(i) of his report, where he stated, inter alia, that:
[59] I thus rejected SEC’s defence, which sought to attribute the problems with its steel stiffeners on the absence of movement joints.
[60] In summary, the steel stiffeners in the present case would be fit for their intended purpose only if they:
i.
stiffened / stabilised the brick walls by carrying wind load;
ii.
could carry the actual weight of the brick wall above them when the bricks beneath them were to be removed;
iii.
did not themselves deform or cause damage to the wall finishes when carrying the lateral and vertical loads above; and
iv.
worked even if no movement joints were provided in the brick walls.
[61] I rejected the assertion of SEC that the fitness of the steel stiffeners for their intended purpose was to be evaluated with respect to only one aspect i.e. their ability to support the weight of the brick walls, without any consideration of the steel stiffener system being installed as a part of the building to stiffen the walls against all reasonably expected loads and without consideration of the need to comply with the relevant building codes. In my view, the stiffener system would not be fit for its purpose if it only satisfied one design aspect but not other relevant design aspects. All design aspects relevant to a stiffener system should be satisfied before it could be said that the stiffener system was fit for its intended purpose. It was clearly insufficient merely to show that the steel stiffeners could per se carry the weight of the brick wall above, if the steel stiffener system would not work if other normal anticipated conditions, factors or loads were taken into account. It must be borne in mind that SEC’s obligation was to design and construct a working practical stiffener system that met the relevant building code requirements and satisfied all other contractual requirements as might have been stipulated by JTC. In my view, it would be an extraordinary contention that a designer of the steel stiffeners could turn a blind eye to all the expected loading conditions of the steel stiffeners as installed in the walls. Obviously the designer of the steel stiffener should take into account "additional forces" (i.e. beyond the weight of the brick wall) that were "in the realm of normal civil engineering knowledge". If the stiffener system was not able to function satisfactorily as a stiffener without the movement joints, the designer could either design a stronger stiffener system to work without movement joints, or himself provide the movement joints if the stiffener system as designed could not work satisfactorily without the movement joints. In either event, the responsibility of providing the movement joints lay with SEC and not JTC on the facts of this case. It was no excuse for SEC to say that if only JTC had provided for movement joints, the steel stiffeners (which as designed by Wyatt needed movement joints before they could perform satisfactorily as wall stiffeners) would have been fine. JTC was obviously not obliged to make changes to the Development to accommodate inadequacies in SEC's steel stiffeners; rather it was for SEC to take the Development as a "given", and design and construct steel stiffeners that would work and not themselves deform or cause damage to the wall finishes when carrying the lateral and vertical loads. Indeed, it was notable that Wyatt himself had conceded that if he had foreseen the magnitude of the compressive stresses in the brick walls, he would have provided for movement joints.
B. Equivalence / Design / Construction
i. JTC's Position
[62] Clause 4.1 of the Standard Conditions of Contract expressly provided that:
[63] Further, clause 6.1 of the Standard Conditions of Contract provided that:
[64] Substitution of materials was specifically addressed in clause 66 of the Standard Preliminaries for Construction Works, pursuant to which the proposed substitution was to be:
[65] Compliance with relevant standards was also expressly provided for in note 2 of the Standard Specification for Construction Works, which stated as follows:
[66] Since SEC proposed to substitute the original r.c. stiffeners with steel stiffeners to be designed and constructed by their sub-contractor Dyntek, it followed that as between SEC and JTC:
i.
SEC was fully responsible for the suitability, adequacy, integrity, durability and practicality of the design of the steel stiffeners;
ii.
the steel stiffeners were to be constructed with all reasonable skill, care and diligence and in a good and workmanlike manner; and
iii.
the steel stiffeners were to be equal to or better than the r.c. stiffeners.
[67] Further or alternatively, SEC owed JTC a duty of care in tort:
i.
to use all reasonable skill, care and diligence in the design of the steel stiffeners; and
ii.
to construct the steel stiffeners using all reasonable skill, care and diligence and in a good and workmanlike manner.
[68] It was also SEC's obligation to ensure that the stiffeners complied with the relevant standards applicable.
ii. SEC's Defence
[69] SEC denied the obligations asserted by JTC. SEC submitted that it had complied with clause 4.1 of the conditions of Contract, as evidenced by:
i.
the SO's issuance of the Certificate of Substantial Completion and the Final Certificate of Completion; and
ii.
the SO's letter dated 24 February 2006.
[70] In my view, the Contract terms made it clear that any such approval / acceptance did not relieve SEC of its obligations. Further, from clauses 17 and 18 of the conditions of Contract, "substantial completion" did not mean that SEC had completed the entire works or that what SEC had done was free of defects. Clause 18.5 specifically provided that the stipulations in clauses 18.1 to 18.4 as to defects liability "shall not derogate in any way whatsoever from the Contractor's liability under the Contract or otherwise for defective work at common law."
[71] Neither would the issue of the Final Completion Certificate preclude JTC from bringing this claim. Clause 33.2 specifically provided that:
[72] Insofar as SEC had sought to rely on the letter from Jurong Consultants Pte Ltd ("JCPL") dated 24 February 2006, that letter merely expressed the view that the SO was functus officio after the Final Completion Certificate, and that the SO "would not therefore be in any position to act/decide on any matters under the Contract". JCPL and the SO did not express an opinion on the merits of JTC's claim.
[73] SEC also contended that it had complied with clause 66 of the Standard Preliminaries as:
i.
the proposal for the substitution of the r.c. stiffeners with steel stiffeners was reviewed by, commented upon and approved by JTC, JTC's Technical Services Group, the SO and/or the SO's Representatives;
ii.
SEC complied with the requirements of the Contract and duly considered and abided by:
(a) the detailed specification prepared by JTC for the r.c. stiffeners;
(b) the comments on and requirements dictated by JTC's servants and/or agents and the SO in respect of SEC's submissions on the steel stiffeners;
(c) JTC's servants and/or agents and the SO's approval of SEC's submissions on the steel stiffeners.
[74] I rejected the above contention of SEC. Clause 66 of the Standard Preliminaries expressly stated that "acceptance of any substitution shall in no way relieve the Contractor of any of his responsibilities for compliance with all the requirements of the Contract." SEC's reliance on “approval” by JTC in relation to SEC’s proposed substitution of r.c. stiffeners with steel stiffeners was therefore misconceived.
[75] Indeed, Sim agreed that "since SEC was substituting steel lintels or stiffeners for the RC lintels or stiffeners originally required, the steel ones would have to be at least equal to or better than the RC ones".
[76] SEC also submitted that Clause 6.1 of the Standard Conditions of Contract was not applicable to the steel stiffeners as the Contract did not expressly provide that the steel stiffeners were to be designed by SEC.
[77] It was not disputed that the Contract did not expressly provide that SEC was to design the steel stiffeners. However, the standard required of any work "designed by the Contractor" under Clause 6.1 must, by necessary implication, apply to work for which the contractor (i.e. SEC) had proposed an alternative design which was accepted by JTC.
[78] I accepted JTC’s submission that it was an implied term of the Contract that where SEC had proposed a design in substitution for a design under the Contract, SEC would be fully responsible for the suitability, adequacy, integrity, durability and practicality of the substituted design that it had proposed.
[79] Having set out the scope of SEC's obligations, I now set out the facts relating to SEC's breaches and explain why I found SEC to be liable for the defects as claimed by JTC.
IV. SEC'S Breaches
A. Design
[80] It was not disputed that the general standard applicable to the steel stiffeners was British Standard 5950 Part 5: Code of practice for design of cold formed thin gauge sections ("BS 5950-5").
[81] JTC's position was that the design of the steel stiffeners was in breach of various requirements under BS 5950-5, in that:
i.
the lateral deflections of the vertical stiffeners exceeded the limit prescribed by section 5.7 read with section 2.4.2;
ii.
the design for the H1-250 horizontal steel stiffeners did not satisfy the lateral buckling requirement of section 5.6.1;
iii.
there was inadequate consideration of the effects of torsion, as required by section 5.9 of BS 5950-5;
iv.
the maximum slenderness for the horizontal stiffeners, H1-250 and H1-300 exceeded the limit specified in section 6.2.2 of BS 5950-5.
[82] At this juncture, it might be worthwhile for me to state that non-compliance of the design of the steel stiffeners with the applicable provisions of BS 5950-5 would in and of itself constitute a breach of note 2 of the Standard Specification for Construction Works. In addition, such non-compliance would also be a breach of SEC's obligation to use all reasonable skill, care and diligence in the design of the steel stiffeners, for which SEC would be liable to JTC.
i. Sections 5.7 and 2.4.2 of BS5950-5 : Deflection
[83] Section 5 of BS 5950-5 related to "Design of members subject to bending".
[84] SEC's expert witness, Jones, agreed that this section applied to both the horizontal and vertical steel stiffeners. Gary Wyatt, when he was confronted with the relevant sections on deflection limits in the code on steel, section 5.7 read with section 2.4 of BS 5950-5, also agreed that BS 5950-5 dealt with both vertical and horizontal deflections, and that the deflection limits stated in the code took into account all loads regardless of the direction they came from.
[85] Section 5.7 specifically addressed the issue of deflection, which would be related to the stiffness of an element i.e. how much an element would deflect or deform under load. A stiffer element would experience lesser deflection under the same load.
[86] Section 5.7 of BS 5950-5 provided that "[t]he recommended deflection limitations for beams are given in [section] 2.4.2".
[87] Section 2.4.2, in turn, stated that:
[88] Table 3 provided for a deflection limit of span/360 for "beams carrying plaster or other brittle finish" for "deflection of beams due to unfactored imposed loads".
a. Deflection limit to be complied with - JTC's position
[89] JTC's position was that this deflection limit of span/360 was applicable to the stiffeners, both in respect of vertical deflection and horizontal deflection, and regardless of the type of loads imposed (be it dead load, imposed load or wind load). According to JTC, the steel stiffeners had failed to comply with this deflection limit of span/360 provided in BS 5950-5.
b. Deflection limit to be complied with - SEC's Position
[90] SEC's expert witness, Jones, did not accept that the deflection limit of span/360 set out in BS 5950-5 was applicable to the steel stiffeners installed at the Development.
[91] In respect of vertical deflections, Jones' initial opinion was that "both concrete and steel horizontal stiffeners comply with code requirements for deflection”. At the start, Jones confirmed on the stand that by "code requirements" he was referring to BS 5950-5. When clarification was sought on the deflection limits stipulated by BS 5950-5 in relation to the steel stiffeners in the Development, Jones changed his position by declaring that there was a "well-known problem" in BS 5950-5 that it did not provide deflection limits for vertical deflection due to dead load, and that his statement on page 19 of D-29 should really read "both concrete and steel horizontal stiffeners comply with my own requirement which is based on reasonable engineering judgment".
[92] Jones contended that the deflection limit of span/360 in BS 5950-5 applied only to an imposed load. As there was no imposed load, Jones considered that BS 5950-5 allowed unlimited deflection.
[93] In Jones' view as such, BS 5950-5 did not set down any specific deflection limit arising from dead load or transient load e.g. wind load on the steel stiffeners. There was only "an implied code requirement that the deflection should not be so great as to cause damage to the applied finishes".
[94] His personal view was that a deflection limit of span/150, or a range between 1/150 and 1/180 would be acceptable. He considered this to be "the limit at which you would then start to get cracking of render and plaster finishes, dependent upon the flexibility of the applied finish itself, whether it's got additives in to improve its flexibility".
[95] However, Wyatt, the designing PE, applied a more exacting vertical deflection limit of span/325 in his design.
[96] This ratio was derived from section 7.1.2(b) of British Standard 5977 Part 2: Specification for prefabricated lintels ("BS 5977-2") (P-31), which he considered to be more appropriate than BS 5950-5 as it was specifically related to lintels.
[97] Section 7.1.2(b) of BS 5977-2 provided that:
[98] In respect of horizontal loading, however, Wyatt applied a deflection limit of span/50 in his design.
[99] He contended that the ratio of span/325 applied in respect of lateral deflection due to vertical loading only since "safe working load" in section 7.1.2(b) of BS 5977-2 referred only to the vertical load. He insisted that there was no deflection limit under BS 5977-2 for lateral deflection from horizontal loading as the ratio of span/325 did not apply when the lateral deflection was due to a horizontal load. Effectively, Wyatt contended that a steel stiffener design could be non-compliant with section 7.1.2(b) of BS 5977-2 if the lateral deflection arising from vertical loads exceeded span/325, but the same level of lateral deflection would have been acceptable if the deflection arose from horizontal loads. I did not find this contention amenable to reason.
[100] Firstly, it should be noted that BS 5977-2 referred specifically to lintels over openings, and not brick wall stiffeners more generally. This was not disputed by Wyatt.
[101] When confronted with the relevant sections on deflection limits in the code on steel, section 5.7 read with section 2.4 of BS 5950-5, Wyatt agreed that BS 5950-5 dealt with both vertical and horizontal deflections and the deflection limits stated in the code took into account all loads regardless of the direction they come from.
[102] In any event, even SEC's expert, Jones, would not endorse a deflection limit of span/50 and applied a range of span/150 to span/180.
[103] While Jones maintained that there was no direct code requirement of limit for deflection of stiffeners horizontally under wind load in BS 5950-5 (which JTC disagreed with), he adopted the same range of span/150 to span/180 in both vertical and horizontal deflections (whether from vertical or horizontal loading). Implicit in this was that the adoption of different limits for deflections in the vertical and horizontal directions or for vertical and horizontal loads would not comply with reasonable engineering judgment.
c. Compliance of the steel stiffeners with deflection limits
[104] Jones calculated the lateral deflections of certain vertical steel stiffeners using various wall dimensions, and applied a wind load of 0.5kN/m for external walls and 0.2kN/m for internal walls (which wind loads were agreed between the experts as well as Wyatt).
[105] These were reflected in D-42 and the results indicated that even applying the ratio of span/150 to span/180, the lateral deflections of the vertical steel stiffeners exceeded the allowable ratio.
[106] Of the 5 situations considered, 4 were of actual conditions on site:
i.
an external wall in the SS 2000 series;
ii.
an elevation 1 external wall in unit #03-12;
iii.
an internal wall in the same unit, #03-12; and
iv.
an external wall of dimensions as set out in page 335 of Jones' 1st AEIC .
[107] The other calculation was for theoretical wall dimensions of 7 m length by 10 m height, with a cross in the middle where the vertical and horizontal stiffeners intersected, as derived from JTC's requirement that the brick walls be strengthened with "r.c. stiffeners at every 5 metres length & r.c. beams at every 3.5 m height".
[108] The vertical stiffener used at this external wall panel was a V1-200. The height of the vertical stiffener was 5250 mm. The horizontal stiffeners on either side of the V1-200 vertical stiffener were H1-300 and were located at a height of 2200 mm from the floor and 3050 mm from the soffit of the beam. Jones adopted a left span of 3600 mm and right span of 4500 mm in his calculations.
[109] Jones' calculations reflected a 38.9 mm lateral deflection of the stiffener in that wall dimension. This produced a deflection ratio of height/132, which failed even the reduced requirements of Jones, of a ratio of height/150 to height/180. Jones himself agreed as much.
[110] The vertical stiffener used at this external wall panel was a V1-100, with a height of 5600 mm. The horizontal stiffeners on either side were H1-250, each of 4000 mm span and located at a height of 2200 mm from the floor and 3100 mm from the soffit of the beam.
[111] Jones' calculations indicated a 54.4 mm lateral deflection of the stiffener in that wall dimension. This was equivalent to a deflection ratio of height/97, which was outside what even Jones would consider acceptable.
[112] The vertical stiffener used at this internal wall panel was a V1-50. The horizontal stiffeners on either side were H1-150, each of 3100 mm span and located at a height of 3100 mm from the floor and 2500 mm from the soffit of the beam.
[113] There was some disagreement between the parties on the height of the vertical steel stiffener, which had been inspected by JTC's expert as well as Mr John Ogilvie McGowan ("McGowan"), a representative of Babtie Asia Pte Ltd ("Babtie Asia").
[114] Dr Ting used a height of 5600 mm (rounded up from 5580 mm, the height set out in relevant drawing); Jones insisted that the height was 4450 mm and calculated the deflections on that basis. SEC based this on its assertion that there was a beam at the top of the brick wall and the vertical steel stiffener had terminated at the beam - an assertion that SEC was unable to substantiate with any drawing but only a photograph, which did not even show that the vertical stiffener had terminated where SEC asserted was a beam.
[115] Based on this alleged reduced height of 4450 mm, Jones calculated a 19.2 mm deflection of the V1-50 stiffener. This was equivalent to a deflection ratio of height/231 and which would comply with Jones' own deflection limits of height/150 to height/180 (although it would still not meet the deflection ratio of span/360 provided in BS 5950-5). If the wall height of 5600 mm (as reflected in the drawing at AB 9881) was used in the calculations, the lateral deflection would be 47.1 mm, which produced a deflection ratio of height/119, falling outside Jones' acceptable deflection limits.
[116] The vertical stiffener used at this external wall panel was a V1-200, with a height of 5250 mm. The horizontal stiffeners on either side of the V1-200 vertical stiffener were H1-300 each of 4400 mm span and were located at a height of 2200 mm from the floor and 3050 mm from the soffit of the beam.
[117] Jones' calculations reflected a lateral deflection of the stiffener of 43.9 mm (using the second moment of area of the cross section "I" = 2.35 x 10) and 44.3 mm (using I = 2.33 x 10). This was equivalent to a deflection ratio of height/119 and height over/118 respectively. These did not comply with even the reduced requirements countenanced by Jones, of a deflection ratio of height/150 to height/180. Jones conceded that.
[118] The vertical stiffener used in this theoretical wall panel was a V1-200, with a height of 7000 mm. The horizontal stiffeners on either side of the V1-200 vertical stiffener were H1-300 each of 5000 mm span and were located at a height of 3500 mm from the floor and from the soffit of the beam.
[119] Jones' calculations reflected a lateral deflection of the stiffener of 155.6 mm (using pinned connections, which was the assumption used in the calculations of all the above 4 scenarios) and 113.5 mm (if partial moment restraint was assumed). This produced a deflection ratio of height/45 and height/62 respectively, which fell far short of the reduced requirements of Jones, of a deflection ratio of height/50 to height/180. Jones himself agreed that the deflection ratios in this scenario were "well outside [his] limit".
[120] It was common ground between both parties as such that the lateral deflections of the vertical stiffeners were unacceptable. Jones conceded that at the deflection limit of span/150 to span/180, "you would start to get cracking of render and plaster finishes", which was one of the mode of defects observed on site.
[121] In my judgment, the steel stiffeners failed to comply with the deflection limit of span/height over 360 stipulated in section 5.7 read with section 2.4 of BS 5950-5, and this constituted a breach of SEC's obligations to JTC.
ii. Section 5.6 of BS 5950-5: Lateral Buckling
[122] Section 5.6 of BS 5950-5 related to lateral buckling. Section 5.6.1 provided, inter alia, that:
[123] JTC’s position was that the design for the H1-250 horizontal steel stiffeners did not satisfy the lateral buckling requirement of section 5.6.1 of BS 5950-5.
[124] Jones accepted that a section 5.6 check was necessary if one were designing steel stiffeners for a brick wall up to 3.5 m height and 5 m length and he would have done such checks himself. Wyatt, however, did not check the steel stiffeners against section 5.6 of BS 5950-5 when he was executing the design.
[125] In paragraph 7.1 of exhibit “PJJ-2” to his 1 AEIC, Jones stated that:
[126] Jones confirmed that by this statement, he meant that the H1-250 steel stiffener, as designed, failed to comply with Section 5.6.1 of BS 5950-5.
[127] As such, I concluded that the steel stiffeners had failed to comply with the lateral buckling requirement under BS 5950-5, and accordingly this constituted another breach of SEC's obligations.
[128] While Jones sought to rely on the brick walls and the vertical stiffeners to provide lateral restraint, he did not perform any calculations to establish quantitatively that this would be sufficient to counter the weakness of the steel stiffeners in terms of lateral buckling.
iii. Section 5.9 of BS 5950-5: Effects of Torsion
[129] Section 5.9 related to the effects of torsion. Section 5.9.1 stated that:
[130] The horizontal steel stiffeners were designed with approximately 75 mm of the bottom flange cut out at both ends i.e. it was not a box-section at the end of the stiffeners, but an inverted U-section. Jones agreed that for the purposes of analysis, the end sections could be considered open sections.
[131] It followed that consideration should be given to section 5.9.1 of BS 5950-5 in designing the steel stiffeners.
[132] In my judgment, the steel stiffeners designed with these open sections at the ends were weaker than closed sections for both torsional loads and lateral loads. As the torsional capacities of the end sections were low, the likelihood of torsional buckling due to eccentricity of vertical loads was present for H1-250 and H1-300. The design of the steel stiffeners overlooked their rotational deformations such that any slight eccentricity would cause the steel stiffeners to twist and warp. Accordingly, I agreed with JTC’s contention that SEC had failed to comply with section 5.9 of BS 5950-5. In my view, any effects of deformation and twisting due to and at the end conditions would be geometrically magnified when the actual lateral deflection or rotational movements at the centre of the steel stiffeners were to be considered. Hence, SEC’s contention that the open sections were only at the end and not throughout the entire length of the stiffener (and therefore would have minimal or no effect) ignored the geometrical effect of magnification that the end deformations would have at the centre of a long steel stiffener.
[133] Dr Ting calculated a torsional moment of 0.068 kNm and a torsional capacity of 0.0632 kNm in respect of the H1-250 steel stiffener. His calculations showed that the torsional moment exceeded the torsional capacity of the section. At the support location of the steel stiffeners, only a maximum eccentricity of 4.7 mm in the loading could be allowed before the torsional capacity of the section would be exceeded. These calculations confirmed that the designed torsional capacities of the section were inadequate.
[134] In respect of the H1-300 steel stiffener, Dr Ting calculated a torsional moment of 0.097 kNm and a torsional capacity of 0.1176 kNm i.e. the torsional capacity only marginally exceeded the torsional moment. In any event, only a maximum eccentricity of 5.7 mm in the loading was permissible before the torsional capacity of the section would be exceeded.
[135] One could also use section 5.6 as a benchmark for comparison by relating the shear buckling strength under section 5.4.3 of BS 5950-5 to the average shear stress derived from section 5.6.1 (i.e. 3 % of the maximum force in the compression flange) and determine whether the average shear stress exceeded the shear buckling strength, as another means of checking the torsional capacity of a member. As I had noted, both JTC's expert and SEC's expert agreed that section 5.6 was not complied with.
[136] It did not appear to me that Wyatt paid any special attention to the consequences of having only a three-sided member (and thus an "open section") at the ends, even though section 5.9 specifically highlighted the effects of torsion on open sections. Bearing in mind the minimal allowance of eccentricity in loading allowed before the torsional capacity of the stiffeners would be exceeded, Wyatt failed to heed section 5.9 of BS 5950-5 in his design.
[137] SEC submitted that the concept of “torsion” had no application at all in the present as-built condition on site whereby the horizontal steel stiffeners had been sandwiched between the brick walls above and below them (i.e. packing) and were therefore restrained from “twisting” by the brick walls. I did not agree as the primary assumption in that submission was that the brick walls above and below were of the same height and had both bowed in the same direction to the same extent. However, where the brick walls above and below were not of the same height and had not bowed to the same extent, or where the brick walls above and below had bowed in the opposite direction into an “S” or “Z” shape, then there would be twisting and torsional effects induced in the horizontal stiffeners. The torsional strength of the stiffeners, including their ability to withstand side-sway deformation, would then become an important consideration. It would not be merely “an academic exercise”, as described by Mr Jones.
iv. Effects of warping torsion increasing the torsional capacity
[138] Warping torsion was a rather technical area which was not conceptually easy to comprehend. Nonetheless, after examining the opinions of the two experts, I preferred the analysis of Dr Ting over that of Jones that the end connections of the horizontal steel stiffeners as designed and built did not provide the necessary restraint and rigidity for warping effects/stresses to materialise sufficiently to increase to any extent the torsional capacity of the horizontal stiffeners in the manner described by Jones. Indeed, as Jones himself admitted:
[139] The welds prescribed for the end connections were, however:
i.
[10] mm long at 10 mm centre to centre for the webs and full length weld at the top flange at the end connections if the horizontal stiffener was sitting on more than 35 mm of the support stub - i.e. the gap was 40 mm or less; and
ii.
full length weld on the top flange as well as both webs if the horizontal stiffener was sitting on less than 35 mm of the support stub - i.e. the gap was more than 40 mm.
[140] The prescribed welding at the end connections clearly did not meet Jones' requirement of a "very rigid connection, fully welded". The welding at the connections was in fact designed only to take the shear coming in from vertical and lateral loads. I accepted JTC’s contention that the same welds could not be relied on to also bear the shear arising from torsional loads. This was a fortiori in the as-built scenario, where the welding design was not followed, and one-sided and irregular welding was observed.
[141] Without restraint for warping at the end connections, the member could not be in a state of non-uniform / warping torsion. Accordingly, I found that SEC’s suggestion that consideration should be given to the "contribution to torsional resistance provided by warping torsion" was misplaced.
v. Section 6.2 of BS 5950-5: Flexural Buckling
[142] Section 6.2 related to flexural buckling and provided, inter alia, that:
[143] JTC's position was that the maximum slenderness for the horizontal stiffeners, H1-250 and H1-300, exceeded the limit specified in section 6.2.2 of BS 5950-5.
[144] Dr Chiew, whose main areas of research were in fatigue and fracture of steel structures, structural stability, light gauge steel structures, tubular structures as well as steel and composite construction, also agreed with JTC on this. Dr Chiew noted at page 2 of his test report on the steel stiffeners that:
[145] SEC however disputed those comments of its own witness, Dr Chiew. Firstly, SEC's expert, Jones, contended that a section 6 check was not required for the horizontal stiffeners. Secondly, Jones contended that the effective length LE that should be used in calculating the slenderness ratio under section 6.2.2 should be 1.0L and not 1.2L.
a. Applicability of Section 6.2.2
[146] Wyatt did not perform any calculations under section 6 of BS 5950-5 in respect of the horizontal stiffeners when he was designing the stiffeners. His contention was that as long as he satisfied “the requirements for slenderness of a web, I’ve satisfied the code. I don’t believe any designer would go to the compression part of the code [i.e. section 6] in trying to evaluate what he has to provide for a web”.
[147] Jones also took the position that when checking the design of a beam in a spanning case, he would have done a section 6 check, specifically sections 6.2 and 6.4, for the vertical stiffeners but not for the horizontal stiffeners.
[148] Dr Chiew, however, considered that a web buckling check should be done in “standard design of beams”.
Q.
If a lintel or a steel member transfers the weight of the wall above it to the weight of the wall below – in other words, it acts more like packing; it will not be functioning as a beam. Would you agree?
A.
This is where, although we designed it as a beam, but there will be occasions -- even when we have designed as a beam, we also need to consider this packing or this compression, because there will be instances where there is actually loads coming from the top and bottom as well. So although we designed beams as such, that you transfer beams -- the loads to the supports, but we also have to consider this -- this mode of failure in beam design. We actually call it web bearing or web buckling, you see.
Q.
And it would be prudent to consider both when designing a beam?
A.
Yes. In standard beam design, you need to consider this as well.
[149] I accepted that Dr Chiew’s approach (which was also Dr Ting's) was the correct one.
[150] Firstly, Jones did not dispute that a section 6 check was relevant in a packing scenario and did such a calculation in respect of the horizontal stiffeners (although he maintained that the calculations were undertaken to try and explain why the stiffeners experienced distortion on site and would not be part of a normal design process).
[151] Jones had initially contended that section 6.2.2 of BS 5950-5 was for a member overall, and not for one plate in a built-up section i.e. part of a member, which was covered by section 4 of BS 5950-5. He agreed however that even if a designer had complied with section 4.2 of BS 5950-5, which was a purely dimensional check for “maximum width to thickness ratios", he should still go to section 6.2 for calculation of capacity.
[152] When further clarification was sought, Jones conceded that in the packing scenario, the web would be treated as a “member” (not part of a member).
COURT:
I thought, when we look at page 299, which is clause 6, we are talking about a member. Why are we suddenly talking about a different (l), which is the packing? I thought we were looking at the whole member, the length.
A.
When you're looking at the vertical stiffener, you're looking at the --
COURT:
Whole length.
A.
-- whole length, yeah.
We're now looking at a horizontal stiffener with a packing load going from top to bottom. The packing load goes through the webs of the horizontal member.
COURT:

The judgment continues past this page. Read the rest at eLitigation.

Jurong Town Corp v Sembcorp Engineers and Constructors Pte Ltd

Grounds of decision

Background Facts

Legal / Factual Issues

SEC's Obligations

SEC's Breach and Resultant Damage

SEC's Defence

Key Issues

SEC'S Obligations

Fitness for Purpose

Whether SEC had an obligation to ensure that the steel stiffeners were fit for their intended purposes

The purpose for which the steel stiffeners were intended

Serviceability

Expansion of bricks

Brick walls did not have movement joints

Equivalence / Design / Construction

JTC's Position

SEC's Defence

SEC'S Breaches

Design

Sections 5.7 and 2.4.2 of BS5950-5 : Deflection

Deflection limit to be complied with - JTC's position

Deflection limit to be complied with - SEC's Position

Vertical Deflection

Horizontal Deflection

Compliance of the steel stiffeners with deflection limits

External Wall in the SS 2000 series

Page 335 of Jones’ 1st AEIC

7m by 10m theoretical wall panel

Section 5.6 of BS 5950-5: Lateral Buckling

Section 5.9 of BS 5950-5: Effects of Torsion

Effects of warping torsion increasing the torsional capacity

Section 6.2 of BS 5950-5: Flexural Buckling

Applicability of Section 6.2.2

Whether the maximum slenderness of the H1-250 and H1-300 exceeded the limit specified in section 6.2.2 of BS 5950-5

Construction and Workmanship

Defects observed after stiffeners were exposed

Incomplete stiffeners

No stub to connect the steel stiffeners

Uneven support

Welding

Welding between flange and web

Welding at end connections

Welding to join two web plates

Stiffeners were Unfit

Steel stiffeners caused defects

How the steel stiffeners caused the defects on site: Dr Ting’s opinion

Stiffeners prone to excessive deflection under lateral load

(i)

Wind load was considered

(ii)

Excessive deflections under wind load

(iii)

Wind speed

(iv)

Consequences

Horizontal steel stiffeners also had the propensity to side-sway

(i)

Dr Chiew’s test results

Stiffeners had low torsional capacity and were prone to twisting

(i)

Was there some rotation / twist / torsion?

(ii)

Horizontal steel stiffeners had low torsional capacity

Poor construction of steel stiffeners aggravated the deformation

How the Steel Stiffeners caused the Defects on Site: Jones' Opinion

Steel stiffeners would fail due to compressive loads

(i)

Movement capability rejected by JTC

(ii)

Wind load was secondary for being a transient load

Steel stiffeners slender and prone to side-sway

Steel stiffeners weak under compression

Steel Stiffeners would have failed with vertical movement of 2.7 mm

Vertical steel stiffeners would have failed with vertical movement of 1.7 mm

Horizontal steel stiffeners would have failed with vertical movement of 2.7 mm

(i)

Question of whether steel stiffeners were fit for purpose

Some accommodation of the vertical movement of 2.7 mm

(i)