The International Journal Precasting of Construction in Singapore s Management Design (2002) & Build 1-12 Projects 1 PRECASTING IN SINGAPORE S DESIGN & BUILD PROJECTS LIM Jiann Yeh 1, WANG Shou Qing 2 and TIONG R 3 1&2 Department of Building, National University of Singapore, Singapore 117566 3 School of Civil and Environmental Engineering, Block N1, Nanyang Avenue, Singapore 639798 Email: clktiong@ntu.edu.sg Abstract A key means of upgrading the construction industry in Singapore is to improve the existing industry techniques and practices that affect construction productivity and cost efficiency, in addition to reviewing the management practices of the industry. Precast technology is not new to the industry, but its use in the local context is still limited for many reasons. The use of Design & Build (D&B) systems also has a long history of development. Its emphasis on a single source of responsibility has an influence on the design aspect, which tends to be more buildable. This study investigates in detail some critical issues related to precasting in Singapore s D&B projects through a questionnaire survey followed by several interviews. It verifies that although D&B encouraged the adoption of precast technology, contractual adoption is still dependent on various factors, especially the cost factor. Other findings, especially the benefits attained through D&B projects when the appropriate precast technology is also integrated, and measures for promoting precasting and D&B in Singapore, are also presented. Keywords Precasting, Design & Build, Cost, Productivity, Buildability. INTRODUCTION In the 1992 Construction Productivity Task Force Report (CIDB 1992), one of the long-term key directions urged in raising the productivity of the construction industry in Singapore is the development and promotion of more buildable designs. Priority areas are the precasting of structural systems and architectural external and internal walls, taking into account lean construction considerations. In addition, the promotion of D&B as an alternative procurement approach for construction projects is another priority area. The traditional procurement system in Singapore generally separates design from construction. Since designers are not responsible for construction, there is little incentive for them to adopt a design that will minimise construction costs and increase productivity. On the other hand, due to the constraints of time, there is little opportunity for contractors to propose cheaper and more suitable alternative designs. In many Western countries, for the tendering purpose designers only perform the preliminary design and stipulate performance specifications. The contractors tender on a lump sum basis to meet the performance specifications and perform the detailed design of the main structural members, reflecting their competence. Potentially, productivity achievement should be better, as construction considerations are taken into account at the design stage.
2 Lim, Wang and Tiong The Singapore construction industry however is still not experienced in buildable designs and standardisation, especially in the area of precasting. Because cost has favoured the use of less productive and conventional designs, designers are not overly concerned about standardisation and are less familiar with how to create buildable designs, which often require additional effort. Precast technology originated from Europe and Japan where extensive studies and development (R&D) have been carried out. Countries such as Finland, where precasting is well developed, still undertake R&D to improve their precast systems. In the 1992 CIDB construction productivity taskforce report, the productivity indicator based on square metre per man-day is used to compare the productivity level between Singapore and two other developed countries. Comparing the productivity level of Singapore with the developed countries, Japan s construction is 30% more productive than Singapore s construction, while a highly industrialised country like Finland is 60% more productive than Singapore s. The high productivity in these two countries is linked to the level of precasting. Japan s construction is 15% to 20% precast while Finland s is 40%. Precasting thus proves to be an attractive option in pushing for higher productivity. It is a necessity dictated by the changing global trends, but the use of precasting is still dependent on the promotional efforts of precasters and exposure to such projects. In recent years, there has been an increasing trend in Singapore in the use of precast technology and D&B in construction projects, especially for the public sector projects. This is evidenced by the introduction of large-scale precasting in the public housing program of the Housing and Development Board (HDB) in the early 1980s. The experience gained from the public sector has been useful in promoting precasting and D&B procurement in the private sector. In fact, for private sector projects, the use of precast components is also gradually increasing. As a D&B system enables a project team to produce a more buildable design, and because precasting is one of the key means of increasing buildability, the integration of precasting with a D&B system has the potential for greater development in the industry. Several studies on local precasting and D&B have been carried out. Most of them however, were mainly focused on either precasting or D&B only and they did not cover the integration of precasting and D&B. For example, on the precasting issues, Lee (1989) did a study on the planning of precast component production. Tay (1996) solely discussed the applicability of the precast method of construction particularly for commercial buildings. Yong (1997) made an elemental cost analysis for precast concrete school structures. Ling (1998) had studied the various production techniques of precast concrete. Yong (1998) did a study on the rationalisation of the precast industry. See (1999) discussed the use of precasting as a priority choice of construction method for the HDB upgrading projects. On the D&B issues, Low (1996) examined the D&B approach to residential projects in Singapore. Khee (1997) did a study of the D&B system from the contractors viewpoint. Lim (1997) s study found out the local client s perspective and identified the contractor s contribution in the D&B form of procurement. Law (1999) examines the suitability of the D&B system for the HDB s main upgrading projects. Akintoye (1994) conducted a survey to investigate the current views of contractors on D&B as a procurement route. The issues covered included the preferred technique of D&B, the suitability of D&B procurement for the different project types and the time, cost and quality advantage gained by adopting D&B procurement. Akintoye and Fitzgerald (1995) conducted a survey to obtain the views of architects on the D&B procurement route. For this study, the issues are considered from the architects and contractors perspective.
Precasting in Singapore s Design & Build Projects 3 OBJECTIVES AND METHODOLOGY This study attempts to explore the use of precast technology in Singapore s D&B projects with the following objectives: To identify the major factors for the adoption of precast technology and the extent of usage in D&B projects. To find out whether D&B procurement facilitates the usage of precast components. To demonstrate the benefits of D&B procurement gained further by the use of precast components. To suggest measures in promoting the usage of precasting in D&B projects aimed at achieving a higher productivity level. The study is limited to the precasting of concrete components only and the structural steel construction has been deliberately left out. Emphasis is placed on precast technology used in D&B projects in Singapore. The questions included in the survey and the interviews conducted are also restricted to precast issues in D&B projects. The opinion study type of methodology was used in the study and the two main techniques used were questionnaire survey and personal interview. An industry-wide survey was carried out during late 2000 to explore the use of precasting in the industry and particularly in D&B projects. The survey targeted 222 local construction firms in Singapore that are classified under the G5 to G8 category in Singapore s Building and Construction Authority (BCA) list of construction firms. Firms in the G5 to G8 category can tender for contract values of $10million and above with G8 being the highest category of construction firms in Singapore. A set of the 4-page questionnaire survey forms was sent to the firms, accompanied by a letter, indicating the objectives of the study. It was designed to seek pertinent information on a variety of subjects under the following main aspects: Factors accounting for the use of precasting; Problems faced using precast components; Whether D&B procurement facilitates precasting; Opinions on the future viability of precasting in D&B projects. 38 completed questionnaires were returned; questionnaires not substantially completed were rejected and the fully completed ones numbered at 33. The survey was also followed by interviews with several of the respondents to either clarify or verify some of the issues. PROFILE OF SURVEY RESPONDENTS All the 33 responding firms have experience in both D&B and non-d&b projects. As shown in Table 1, about two-thirds of the respondents have more than 5 years of experience in undertaking D&B projects.
4 Lim, Wang and Tiong Table 1 Years of D&B Experience Years of D&B experience Percentage of responding firms 1 to 5 years 33% 6 to 10 years 13% 11 to 15 years 20% 16 to 20 years 7 % 21 to 25 years 7 % > 25 years 20% The majority of the respondents have about 40% of the projects under D&B procurement (Table 2). About one-third of the responding firms had D&B projects consisting about onefifth of the total number of projects they undertook. Table 2 Percentage of D&B Projects that Responding Firms Had Percentage of D&B projects Percentage of responding firms (based on no. of projects) 0% 0 % 1 to 20 % 33% 21 to 40% 27% 41 to 60 % 12% 61 to 80 % 15% 81 to 100% 12% In terms of the project types, a majority of the D&B projects done by the responding firms are residential and industrial. Other projects include marine structures or military camps as shown in Table 3. Table 3 Distribution of Types of D&B Projects Project category Percentage of responding firms Residential 67% Industrial 61% Commercial 51% Institutional 18% Others 9 % The respondents job designations include the position of company president to professionals such as that of quantity surveyor and engineer. The responding firms are mostly classified under the G8 category (Table 4). Table 4 Company Registration Category Company category Percentage of responding firms G5 13% G6 22% G7 25% G8 40% Among the responding firms, about 40% of them have one or more D&B projects currently under construction. Precasting is widely adopted for both non-d&b projects and D&B projects, and the precast level vary from project to project.
Precasting in Singapore s Design & Build Projects 5 SURVEY RESULTS AND FINDINGS The following will present the results and findings of the survey based on the responding firms, and compiled from the combined results of both the questionnaire survey and interviews. Extent of Precasting in Projects Out of the 33 responding firms, 25 adopt precasting in both D&B and non-d&b projects, 2 did not have any precasting in their projects, while 2 use precasting in non-d&b projects only and 4 use precasting in D&B projects only (Table 5). Table 5 Precasting in D&B and Non-D&B Projects Precasting in projects Percentage of responding firms Precasting in both D&B and non-d&b projects 75% Precasting in D&B only projects 12% Precasting in non-d&b projects only 6.5% No precasting in D&B and non-d&b projects 6.5% Reasons For Using Precasting in D&B Projects The responding firms using precasting in D&B projects were asked to assess the importance of the relevant factors for using precast components. Among the ten factors listed in the questionnaire, respondents were given the option to choose what they think are the reasons for using precasting in their projects. The results are shown in Table 6. Table 6 Respondents Agreement on the Reasons for Using Precasting in D&B Projects Reasons for using precasting Percentage of respondents agreement Difference in unit cost 95% Less manpower needed on site 90% Better quality achieved 85% Better buildability 85% Shorter construction time 80% Less wastage of resources 75% Past experience or knowledge 75% Availability of suppliers/plants 66% Standardised Design 66% Contractors involvement/decision 60% The cost factor ranked highest and this coincided with the views of the interviewees as one respondent had said, Cost is still the ultimate criteria in deciding on the use of precasting in every type of project, regardless on whether it is D&B or non-d&b, residential or commercial, etc. Almost all the respondents feel that there were savings in the preliminaries of a project due to a shorter construction period, but the component cost per unit is still high, unless the design is standardised or repetitive for mass economies of scale to be taken advantage of. At the present stage, foreign labour is still abundant and the cost of such a workforce is still low despite the levy tax imposed on them by the government. This explains to some extent the popularity of the traditional construction method. 90% of the respondents felt that the use of precasting would result in less manpower needed on site. As precast components are manufactured off site, labour is needed only for handling and installation, unlike for the cast in-situ components, where manpower is needed for the construction of the framework and scaffolding. As most construction accidents involve the workers, a smaller workforce will suffer fewer casualties than a larger workforce in the event of a construction accident. A substantial reduction in labour required may offset the slightly higher precast component unit cost. Productivity based on volume of work per worker will be higher than that based on traditional construction.
6 Lim, Wang and Tiong 85% of the responding firms felt that a better quality finish than cast in-situ components is another reason for using precast construction. As precast components are manufactured beforehand, quality can be checked and defects rectified before their installation. For cast insitu components, the defective ones have to be removed from the cast-in position and reconstruction has to be carried out. There would thus be wastage in resources and time. Most interviewees agreed that precast components will be more consistent in terms of quality than cast in-situ items. Similarly most of the respondents regard better buildability as the reason for precast construction. One respondent said, D&B contractors generally look for the best method to construct. A buildable design generally is a standardised design, and with standardised dimensions, precasting comes into play. The construction firms objectives also exert some influence on precasting adoption. A company that strives to achieve a higher buildability score or CONQUAS score may strongly go in for precasting. A few of the respondents acknowledged that the legislation of the minimum buildability requirement for building plan approval on 1st January 2001 definitely has an impact on the construction method or process. Thus it is likely to see more precast technology being adopted. Reasons For Not Using Precasting In D&B Projects The responding firms were also asked to assess the reasons for not using precast components in their D&B projects. The results are tabulated in Table 7. Table 7 Respondents Agreement on Reasons for not Using Precasting in D&B Projects Reasons for not using precast Percentage of respondents agreement Difference in unit costs 95% Small scale of project 80% Less standardised design 75% Aesthetically not pleasing 50% Longer construction time 10% More manpower needed on site 5 % Inadequate suppliers/plants 0 % Lack of experience or knowledge 0 % Almost all the respondents felt that the difference in unit costs was one of the main reasons why precast components were not used in their D&B projects. As one respondent highlighted, At this transition stage, precast components are still not as cost competitive as cast in-situ components. In the past, the HDB faced the problem where there was an insufficient volume of construction to justify the use of precasting. Several major public housing projects were then awarded on a turnkey basis to French, Japanese and Australian contractors. It was only when its contractors had invested in precast plants that more components could be produced at a lower unit cost than before. A wide variety of components could then be produced using precast technology and thus bring about its wider usage. The scale of a project is the third main reason why these firms did not adopt precast technology in their D&B projects. One critical consideration of precasting is the high repetitiveness. The mould for the precast components is already a fixed cost. If this fixed cost can be defrayed over a large volume, the average unit cost will be lower, as one respondent stressed on this point. This in fact, has a direct link to the previous point about the cost factor.
Precasting in Singapore s Design & Build Projects 7 A design with complex features and non-standard dimensions is another barrier for the wider usage of precasting. As one respondent stated, At the present stage, the HDB s contractors are now able to manufacture precast components of complicated designs, but there must still be repetition so that it will be economical. The sophisticated service duct for the upgrading projects is one example of such a complicated component designed by the HDB. Precast Components in D&B Projects The survey also aims to find out the common precast components, which are basically categorised as structural and architectural components, used for D&B projects. Based on the results in Table 8, structural components, especially beams and slabs, are the major items that were precast in D&B projects. These components are more standardised in size or shape. Their large quantities demanded thus justify for precasting. Table 8 Type of Precast Components Used in D&B Projects Precast components Percentage of respondents affirming their usage Structural Slabs 93% Beams 87% Columns 67% Staircase 56% Walls 46% Refuse chute 40% Water tank 33% Architectural Facade wall 46% Parapet 40% Balcony 33% Facade wall 27% Light weight partition 20% Gable end wall 20% Canopy 14% Bathroom 7 % Whether D&B Procurement Facilitates Precasting The survey also attempts to find out whether D&B procurement facilitates the use of precast technology. Table 9 shows that 93% of the respondents agreed on this point. For the reasons why D&B procurement facilitates the use of precasting, 90% of the respondents said that the involvement of the contractor in the design process leads to a buildable design. This is the main merit of the D&B scheme, whereby the owner enters into a single contract with one entity that is responsible for both the architectural/engineering and construction works of the project, thereby producing a design that is more buildable than what a traditional form would produce. Table 9 Respondents Agreement on Factors Facilitating Precast Technology Factors facilitating precast technology Percentage of respondents agreement D&B system produces a more buildable design, leading to more precast construction. 90% D&B system integrates design and construction, with precasting during the design phase; it helps to achieve time reduction. 85% D&B design tends towards standardisation and repetition, and therefore precast construction. 65% D&B procurement consist of an integrated system of building components like partitions, ceilings, etc, which were 60% mostly precast. D&B contractors make more use of precast technology for design due to the expertise they have built up, and achieving 60% economical construction.
8 Lim, Wang and Tiong Precast technology enhances a building s buildability, i.e. there is relatively greater ease in constructing a building. Therefore a buildable design can be associated with a higher level of precasting. As one of the respondents said, The D&B package depends on the contractor to make decisions for the client, to design it accordingly and then go about building it. Economy comes into play and the design is more buildable and there is an inclination towards precasting as they offer many merits over the cast in-situ form. 85% of the respondents felt that the D&B form is best used for projects facing time constraints. Time saving tends to go hand in hand with cost savings. As the contractor is responsible for the design, construction, planning, organisation and control, these activities can proceed concurrently to a greater extent than is generally possible using the design-bid-build system. To achieve this time saving, the construction components can be precast and assembled on site, hence the D&B system enhances the use of precast which offers such benefits over the traditional form of construction. 65% of the respondents agreed that design, which employs standardised products or processes, is basic to the D&B concept. Precast components are generally standardised in dimension and quality. Standard construction components come in a range of standard modular dimensions that simplify the construction process. The D&B system does not require original design solutions for components such as doors, windows and fittings. These components are purchased off-the-shelf, thus allowing designers and consultants to concentrate on the aesthetics and structural aspects of a project as opposed to the availability of materials for their specific designs. Therefore, the D&B system will produce a more standardised design that employs the use of precast technology. Nevertheless, one respondent asserts that standardised design is not necessarily an outcome from D&B projects. It depends very much on the client, the contractor and the architect. Their attitudes play a major role. The D&B design varies from project to project and economics is one main concern of D&B. The construction team may forgo the standardised design while a unique or creative design which conforms to the requirements of the client may be the alternative taken instead. The D&B industry uses the assembly and pre-assembly of a system combining standard components that are commonly available. Examples of these integrated systems include partitions, ceilings, cladding, curtain walling, roofing, mechanical, electrical, sanitary and plumbing systems. This has the objectives of achieving higher productivity and a shorter construction time. The assemblies and sub-assemblies are designed at the detailing stage to facilitate easy installation. When the concrete elements are repetitive in dimensions and fulfil the criteria of unit weight for hoisting, then the components can be precast for easy installation. This form of integrated subsystems therefore tends towards precasting. It also requires a good D&B contractor to co-ordinate the various inputs from the different specialist players to achieve a fully completed building process. 60% of the respondents agreed on this point. Finally, most D&B contractors have over the years built up their expertise and experience from the large number of such projects they have undertaken. Their single responsibility for a D&B project enable them to introduce new construction techniques that rely less on human labour and is more mechanised. More building components could be precast as such unit costs get less and less due to the declining manufacturing costs because of mass economies of scale or extensive improvements in the production techniques. 60% of respondents also agreed on this factor.
Precasting in Singapore s Design & Build Projects 9 Problems Faced In Using Precasting in D&B Projects The survey also analyses the major problems encountered by the respondents in using precasting in D&B projects. Jointing with either other precast or cast in-situ components is the major concern for using precasting in D&B projects (Table 10) and many respondents voiced the opinion that if detailing is inadequate at the joints, there might be waterproofing problems. Therefore, to prevent this from occurring, joints should be cast in-situ and good sealant effectively installed between the joints. 20% of the respondents highlighted the transportation problems, especially for projects in the central business district area. As one respondent stated, Precast components take up storage space on site and made site access difficult if the components were delivered ahead of or behind schedule. Therefore, proper scheduling is important in order to achieve the just in time delivery concept. Table 10 Problems Faced in Using Precast Components In D&B Projects Major problems faced in using precast components Percentage of respondents agreement Jointing with other cast in-situ members 40% Jointing with other precast members 35% Transportation problems 20% Installation or assembly problems on site 13% Size of members not available from supplier 10% Precast component not fulfilling specification or requirements 8 % 13% of the respondents said they faced assembly problems when carrying out the installation work on site. The interviewed respondents stressed the need of the suitability of hoisting equipment used for the assembly process (Table 10). The load to be carried by the equipment should be correctly assessed before deciding the appropriate type of hoisting equipment. The decision to use precast construction is only carried out after the whole design concept is finalised. The team could then carry out a feasibility analysis. Thus there may be a problem of design overlooking on the sizing of the members and as a result, conventional means have to be adopted instead of precast construction, a respondent commented. 10% of respondents mentioned the member size problem. Only a few respondents faced the problem of precast components not fulfilling the stipulated specifications or requirements. Quality control is part and parcel of project management that applies to every work scope. The quality checks made during the precast production line ensure the appropriate degree quality. Measures To Promote Precasting in D&B Projects The last section of the survey examines the measures to promote the usage of precasting in D&B projects. 80% of the respondents proposed for the import of new technology or ideas so as to mechanise the construction process (Table 11). This would also have the benefit of cutting down on the foreign labour needed on site. As one respondent said, The attitude of the local contractors towards mechanisation or precasting is not there, as this could be due to the high initial capital outlay or the volume of projects is not sufficient to support this unless they choose to specialise. This sentiment needs to be addressed and the appropriate action to be taken.
10 Lim, Wang and Tiong Table 11 Respondents Agreement on Measures of Promoting Precasting in D&B Projects Measures Percentage of respondents agreement Workshops/Seminars 90% Mechanise the construction process or import new technology 80% Public sector taking the lead 75% Government incentives 75% Legislation/Regulations 20% A majority of the respondents support the concept of organised workshops or seminars to increase the industry s awareness. One respondent said, These campaigns have been going on quite regularly, but it only attracts certain categories of people and ultimately it is up to the people in the industry to make their own judgement. About 75% of respondents welcomed government incentives. It could be in the form of tax rebates or preferential margins when tendering for public projects. A majority of the respondents perceive the government bodies as the leaders in precast technology and D&B projects. A senior development officer in the BCA gave the following comment during an interview with the media, The BCA is not asking any contractor or specifier to build the entire building using 100% precast components. It is in fact advising the contractors not to use precast components in a building project if it is not economically viable or impossible to use. What the BCA is saying is that contractors should steer away from a labour intensive site work and opt for more construction friendly methods that are more productive and cost effective. The respondents interviewed also felt that the public sector s demand for precast construction will broaden the supporting infrastructure, the suppliers and the production capacity. This has the benefit of lowering the cost of precast construction due to mass economies of scale in production. The private sector will eventually follow when they perceive the benefits showcased by the public projects. Fewer respondents favoured the use of legislation or regulations. The strict enforcement of such measures will trigger resentment from the firms affected. Moreover, precast technology is not the ultimate economical construction method. However, some respondents felt that the regulations may change a designer s or architect s mindset, and a more buildable design will evolve with the result of more precast components used. This is the reason why D&B procurement should be promoted to the industry as it serves as a catalyst to the precast industry too. CONCLUSION The construction productivity in Singapore is still low when compared to other more industrialised countries. This is the result of the prevalence of traditional construction practices. There is therefore a need to promote new and efficient construction practices. Precast technology comes in handy as an alternative form of construction as it could increase the productivity. So is the D&B procurement, which integrates the design and construction processes and leads to higher buildability and productivity. This study has addressed several key issues identified in relation to the use of precasting in D&B projects in Singapore. The results and findings confirm the importance of the cost difference between precast and traditional construction as one of the major factors determining the use of precasting in D&B projects. Despite the merits of precasting and
Precasting in Singapore s Design & Build Projects 11 D&B, practical circumstances limit the benefits gained to some extent. The study also reveals the extent of precast usage for building projects, especially for D&B ones. The results show that precast items are mostly structural components. These components, with a larger volume and less complicated design, will be more cost effective than architectural components when they are precast. The findings also show that the respondents had strongly agreed that D&B system could produce a more buildable design, which could directly result in a rising usage of precasting. The integration of precasting and D&B will enhance a project s benefits of delivering on time and within budget. The former facilitates the latter. Both precast technology and D&B share the same trend in that they are the major approaches outlined towards upgrading the construction industry in Singapore. The study also presents the respondents views about the problems faced when using precasting in D&B projects. They could be alleviated if proper construction processes were followed. The measures recommended in the study to promote precasting in D&B projects received positive responses from the respondents, with the exception of introducing legislation and regulations. These conclusions confirm the recommendations by the government bodies. For example, the Committee on Singapore s Competitiveness had recommended that the Industry Productivity Fund (IPF), managed by the Singapore Productivity and Standards Board (PSB), be used to encourage industry players to use buildable designs and to promote the use of precast and prefab materials and components. In addition, the IPF should be used to help suppliers upgrade to ensure an adequate supply of prefabricated materials. The Committee also recommends a three-pronged approach to increase the use of D&B arrangements - through promotions, provision of a conducive environment, and the nurturing of D&B firms. The industry should encourage the formation of multi-disciplinary firms in order to groom a core of internationally competitive firms with expertise in D&B practices. In the long term, good D&B firms will be able to compete effectively overseas. REFERENCES Akintoye, A. (1994). Design and build: a survey of construction contractors views, Construction Management and Economics, 12, 155-163. Akintoye, A. and Fitzgerald, E. (1995). Design and build: a survey of architects views, Engineering, Construction and Architectural Management, 1, 27-44. CIDB (1992). Raising Singapore s Construction Productivity, CIDB productivity taskforce report. Khee, H.Y. (1997). Is design & build worthwhile? (Contractors point of view), School of Building and Real Estate, National University of Singapore, Singapore. Law, P.E. (1999). Suitability of design and build system for the Housing and Development Board s main upgrading projects, School of Building and Real Estate, National University of Singapore, Singapore. Lee, T.W. (1989). Planning of precast component production, School of Building and Real Estate, National University of Singapore, Singapore. Lim, S.G. (1997). Design and Build - a single source of responsibility, School of Building and Real Estate, National University of Singapore, Singapore. Ling, K.L. (1998). Production techniques of precast concrete, School of Building and Real Estate, National University of Singapore, Singapore.
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