大学精品课件：INSTRUCTION TO BIDDERS.doc

1、1 PART 1 1. The types of contract available In a major project the employer or client engages designers and contractors. The exact relationship between the employer, the designer and the contractor depends on the type of contract used by the employer. The traditional form of contract is for the empl

2、oyer to engage, on a separate agreement, independent designers and then to let the construction phase of the project out to tender and award it to the winning contractor. The most frequently used type of contract is the Bill of Quantities or measurement type of contract. Whilst this remains the most

3、 extensively used type of contract there are others that offer different characteristics to the employer and may well suit particular projects. The types of contract available include: (1) Bill of quantities or measurement contract The basis of this type of contract is that the contractor is paid fo

4、r the work done. Hence the work done has to be measured. The Bill of Quantities contract provides contractors with a common document on which to base their tender, thus attempting to ensure that all tenders are received on an equitable and comparable basis. The Bill of Quantities is prepared from dr

5、awings and itemized according to one of the standard methods of measurement. Each item contains a brief description of the work and a stated quantity of work. An example of a page from a Bill of Quantities document is given in figure 3. The tenderer is required to enter a unit rate and the total amo

6、unt for each item allowing in these sums for all labour, plant, materials, subcontractors, temporary works and materials, overheads and profits. There is normally a section for preliminaries, i.e. site offices and other services and there are normally items for prime cost requirements such as plant

7、specified precisely by the designer and for nominated subcontract work. The sum of all these items is the tender or bid figure. As the contract proceeds the actual quantity of work executed in each item is measured and valued at the rates given by the contractor in the Bill of Quantities in the tend

8、er submission. This permits the calculation of interim, usually monthly, payments and of the final account. Additional work is either valued at the rates quoted in the Bill of Quantities or is separately negotiated. (2) Schedule of rates contract The tender documents for these contracts usually comp

9、rise outline drawings and perhaps a bill with very approximate quantities. The tenderer is asked to submit “rates“ for a list of items of work. As the work proceeds the contractor is paid the rate quoted for the measured quantity of work executed. This type of contract is used when completed designs

10、 are not possible and the client wishes to proceed without undue and extensive delays. Difficult refurbishment work, where the extent of the work is unclear until some dismantling or demolition has taken place, is an example where this type of contract could be useful. 2 Figure 1. An example of a pa

11、ge from a Bill of Quantities document Number Item description Unit Quantity Rate Amount E311 E321 E325 E326 EARTHWORKS Excavation for foundations Topsoil maximum depth 0.25 m Material other than topsoil, rock or artificial hard material maximum depth 0.25 m for footpath; commencing underside of tops

12、oil Ditto maximum depth 2-5 m for chambers Ditto maximum depth 5-10 m for tank m3 m3 m3 m3 19 10.5 7.8 102.5 E522.1 E522.2 E531 E532 Excavation ancillaries Preparation of excavated surface Ditto at 60“ to the horizontal subsoil Disposal of excavated material; topsoil Ditto subsoil m2 m2 m3 m3 70 98.

13、4 19 120.8 F247.1 F274.2 F277 IN SITE CONCRETE Provision of concrete-cement to BS 4027 Designed mix Grade C20 Designed mix Grade C20; minimum cement content 300 kg/m3 Designed mix Grade C35; minimum cement content 360 kg/m3 m3 m3 m3 10 0.5 104.5 F411.1 F411.2 F425 F522.1 Placing of concrete Mass bli

14、nding thickness 80 mm Ditto to sloping hopper Mass benching Grade C20 thickness varying to chambers Reinforced bases thickness 300 mm hopper bottom m3 m3 m3 m3 2.2 7.8 0.5 0.4 Page Total carried to Summary (3) Lump sum contracts Normally in this type of contract the tender documents do not have a Bi

15、ll of Quantities and the tenderers are invited to submit a bid based on the drawings and the specification prepared for the particular project. In submitting a bid the contractor is responsible for assessing all the costs to be incurred in completing the works described in the drawings. The work may

16、 be subdivided into phases to facilitate stage payments. This contract fixes the price the client or employer has to pay. However, it offers little scope for flexibility. (4) Cost reimbursement contract This type of contract is designed to allow work to proceed while designs proceed. They normally h

17、ave independent designers producing the designs and drawings and specifications and 3 the contractor is paid the audited costs of the work covering labor, plant, materials, subcontractors, and site on-costs together with a fee. The type of fee is determined by the contractual arrangement and may be

18、a fixed fee, a percentage fee or it may be based on a target cost. Fixed or percentage fee contract - The basis of the fee is agreement between the employer and the contractor at the outset. This fee is usually designed to cover the contractors overheads and profit. The direct costs of the work are

19、paid by the employer. These are subject to audit. The total sum paid is the direct costs plus the fee. Potentially the client or employer is at risk because the contractor has no incentive to keep costs constrained. This lack of incentive is checked by the monitoring procedures employed by the clien

20、t to ensure the most efficient construction methods are used. This type of contract is only manageable by sophisticated and experienced client organizations. Target cost contract - This type of contract is a variation on cost plus fee with the fee based on a target cost with bonuses available to the

21、 contractor if the costs are below target and penalties if the costs are above target. In this way the contractor is sharing in any savings made and is sharing the risks of additional costs. The original target cost is negotiated between client and contractor based on the outline drawings of the sch

22、eme as it is at the time of negotiation. As the design progresses the target cost has to be adjusted to accommodate the different quantities of work required. This form of contract is also only suitable for the competent client organization. (5) Design construct contracts These are also known as “tu

23、rnkey“, “all-in“ or “package-deal” contracts. The contracts previously described all lack separate and, usually, independent designers. In this type of contract the whole project covering design, construction and commissioning is let as a single contract to a single organization. A small number of c

24、ompetent organizations would be invited to submit proposals outlining the design and the price offered. The key to the success of this type of contract is the client organizations ability to write a detailed and comprehensive project brief specifying the performance criteria of the completed project

25、. This type of contract has found success in projects such as simple office blocks, hotels, industrial buildings, car parks and at the other end of the complexity scale, in nuclear power stations and large industrial projects involving major civil, mechanical and electrical components. (6) Managemen

26、t contracts In the previous examples of types of contract the design has either been let to separate and, usually, independent designers and construction to contractors on a separate contract, or the complete design and construction has been let to one organization. This presents two extremes that m

27、ay not use the skills of designers and contractors to full advantage. Thus, in an effort to employ the most experienced and skilled designers, to allow contractors lo bring their construction experience to bear on the design and so produce buildable, cost-efficient designs and to bring greater skill

28、s to the planning, coordination and management of projects, a new range of contract types emerged known as “management contracts“ (see figure 4). These include: (a) Construction management contracts In this form of contract the client or employer organization employs a construction manager to act as

29、 adviser to provide planning, management and coordination of design and construction. 4 The client organization pays a fee for this service but in this form of contract the client organization continues to place the contracts direct with designers and constructors. Thus, there is a clear distinction

30、 between the organizational lines of communication that flow through the “construction” and the contractual relationship which do not pass through the constructor or project manager but go straight to the client as in traditional contracts. In principle, all types of firms competent and experienced

31、in construction could provide the service of “construction manager“. In practice, it has tended to be major construction contractors who have performed this function. The construction management firm would be precluded from holding any of the construction contracts. The construction manager plays a

32、role similar to that of the architect or consulting engineer but without any design responsibility. The advantages are that the project is being managed by an independent manager capable of managing the design process as well as construction without favoring any of the individual parties, leading to

33、 better management and coordinated projects. (b) The management contract This is an extension of the construction management contract to the extent that the “construction manager“ or managing contractor lets the contracts. This aligns the organizational lines of communication with the contractual re

34、lationships. The managing contractor would again be precluded from holding any of the construction contracts. Again the managing contractor would be paid a fee, but as contracts are placed with the managing contractor the potential exists for the managing contractor to carry some risk. The managemen

35、t contract can either be employed for construction-only contracts or for design and construction. Notwithstanding this range of contract types available, the form of contract that still predominates is the traditional measurement type of contract based on the Bill of Quantities. The parties in this

36、type of project are: Figure 4. Organization charts for different types of contract The client or employer is the firm or organization requiring the work to be constructed. The design is separated from construction and a separate agreement is entered into between the client and the design firm to pro

37、vide design services; this may be extended also to provide supervision services during construction. The design team would prepare the design and the contract documents, invite tenders and advise on the award of the contract. Payment for these services is a fee negotiated at the outset. The relation

38、ship between the client and the contractor is a contract, which is awarded following the tendering process in which the contractor submitted a bid. The next section deals with the contract documentation that describes the works and the contract between the client and the contractor for a traditional

39、 measurement type contract. PART 2 1 The project documentation The documents which describe a contract and on which a bid is prepared for a measurement type contract are: Instructions to tenderers; 5 Conditions of contract; Technical specification; Bill of Quantities; Tender drawings; Form of tender

40、; Form of bid bond; Form of agreement; Scope of the works; Instructions relating to the programme for the works; Form of performance bond; and Form of the guarantee for advance payment. Conditions of contract The conditions of contract define all the contractual obligations of both parties, i.e. the

41、 contractor and the employer, to the contract. The conditions of contract will also define the powers of the engineer or others supervising the work. The terms of payment and performance bond will be described. Most contracts are based on a standard set of conditions and one in common use for intern

42、ational projects is Federation International des Ingenieurs - Conseils (FIDIC) Conditions of Contract. Technical specification The technical specification controls the quality of the work and describes the work to be undertaken, the nature and quality of the materials to be used that the workmanship

43、 requires. This is normally achieved by reference to published “Standards“ or “Codes of Practice“. The specification may also define the sequence of construction required by the employer. Bill of Quantities The Bill of Quantities is used as a document for acquiring tenders on an equitable and compar

44、able basis. The Bill of Quantities is a list of items giving brief descriptions of the work to be undertaken together with the quantities. The Bill of Quantities is usually structured into several sections. When the tenders are submitted each item will have a rate entered and the amount or value of

45、the item calculated. This provides the means of comparing bids. It also provides the means of assessing the value of work completed for payment purposes as the contract proceeds. The method of measuring quantities and setting out a Bill of Quantities is usually undertaken according to one of the pub

46、lished “standard methods“. Tender drawings The tender drawings should be sufficient to describe and delineate the works in enough detail to allow the tenderer to understand the requirements and to enable the tenderer to submit a bid. In an ideal situation, the tenderer would receive a full set of co

47、mplete drawings giving all general arrangements and drawings of working details. Frequently this is not possible and so a restricted set of drawings is available. Form of tender This is the pro forma on which the tenderer submits the offer, in writing, to undertake the 6 work described in the tender

48、 documents and according to the specification. This form will state the total tender sum. If the tenderer is submitting alternative designs there may be more than one form of tender. The additional ones would contain amendments linking the form of tender to the revised design. Form of bid bond This

49、pro forma will submit the bid bond reimbursing the employer under the conditions prescribed. It defines the acceptable guarantor of the bid bond. Form of agreement This pro forma represents the legal undertaking between the contractor and the employer to undertake the work described in the contact documents. Scope of the works This document describes the extent of the works included in the contract. Instructions relating to the programme for the works This document describe