Evaluation Strategy for Innovative Construction Products and Systems

Transcription

1 1 Evaluation Strategy for Innovative Construction Products and Systems CIB 2004 Conference Gilles Poirier, Bruno Di Lenardo, Luc Cécire, Alphonse Caouette ABSTRACT Building officials, professionals and designers are more and more seeking third-party assessment for new and innovative construction materials, products and systems because of the complexity in determining the suitability for use of these innovations. This complexity and today s user expectations make it difficult for one person to undertake the assessment of these products. Such product assessment is better handled by a team of experts possessing the required experience and technical knowledge to define the material and performance issues and the required assessment protocol to establish the suitability for use of the product, including its conformance to the applicable codes and standards. The team of experts needs to be from a number of technical fields to properly define the required performance criteria and test methods for the assessment protocol, as the new products increasingly consist of composite materials and they are often proposed for different applications. The new products may not provide the built-in redundancy that practice have been relying on from traditional materials over the years. The impact of the new products on the long term performance of building assemblies and components may be quite significant given their different physical properties and proposed applications. In addition, the requirements defined in codes and standards were not developed for these new products and these need to be addressed in terms of their intent. The technical opinion that is generated from the product assessment needs to be recognized by the code authorities, the construction industry and the end user for the product to gain acceptance within the market place. The paper will discuss product assessment issues with respect to new and innovative construction products. The discussion will include examples to highlight the complexity of the assessment of new and innovative products that are presently entering the marketplace. INTRODUCTION The selection or acceptance of construction products is getting more and more difficult for owners, designers, specifiers and building officials because of all the innovative or non-standardized construction products, services and processes available on the market today. The uses of these newer products are proposed, most often, based on manufacturer's data, which may or may not have been verified by an independent 3 rd party organization. More important, the data may not provide the required information for the authorities or professionals to establish the acceptability of the product for the intended use. Establishing the suitability for the intended use of these innovations or in other words their suitability-for-use is very challenging given there complexity, and in many situations requires a team of experts representing Authors Note: Gilles F. Poirier, P.Eng., is currently an Evaluation Officer with the Canadian Construction Materials Centre, Institute for Research in Construction, National Research Council of Canada, Ottawa, Ontario, Canada Bruno Di Lenardo, P.Eng., is currently an Evaluation Officer with the Canadian Construction Materials Centre, Institute for Research in Construction, National Research Council of Canada, Ottawa, Ontario, Canada Luc Cécire, P.Eng., is currently an Evaluation Officer with the Canadian Construction Materials Centre, Institute for Research in Construction, National Research Council of Canada, Ottawa, Ontario, Canada Alphonse Caouette, P.Eng., is currently an Evaluation Officer with the Canadian Construction Materials Centre, Institute for Research in Construction, National Research Council of Canada, Ottawa, Ontario, Canada

2 2 experience and technical knowledge from many fields. The required expertise will vary from one innovation to the other and it is generally hard to find within the same organization. This is why authorities and professionals are seeking evaluation or technical assessment for these innovations from independent organizations that are in a position to undertake such tasks with the risk associated with them. In many countries, the evaluation (referred as technical assessment in many countries) of innovative or non-standardized construction products, services and processes is offered by specific national organizations, e.g., in Canada this task is left to the Canadian Construction Materials Centre (CCMC). These organizations may be associated or part of a research centre or they may have a network of expertise that they can call upon as needed. The evaluation or technical assessment strategies used by these organizations may vary, but they all intend to take into account all the performance issues associated with the intended use, regulations and user needs. These evaluations or technical assessments facilitate the acceptance of innovations in the market place by demonstrating that the innovations performance is equal or better than products recognized by building codes or the innovation s performance is suitable for use. At the present time, the acceptance of these evaluations or technical assessments is mainly country specific. There is a need for a better understanding of the differences between the strategies used for the evaluation or technical assessment of construction products and systems or ideally an international base strategy to facilitate the acceptance of innovations on an international basis. CCMC s evaluation strategy and process for innovative construction products and systems is used as an example in this paper as a model to establish the performance and suitability-for-use of innovations. The acceptance of evaluation or technical assessment of construction products and systems between countries is the subject of a separate paper titled International Co-operation in the Technical Assessment Field. 1 CANADIAN GUIDING PRINCIPLES CCMC s strategy for setting the scope of the evaluation of construction innovations has been to assess a product s suitability-for-use. Suitability-for-use implies that the performance of the product should be evaluated against: a) explicit code requirements (which include referenced standards), b) the intent of the code requirements, c) performance issues not covered by code, but reasonably expected, and d) expectations assigned or put on by others, e.g., architects, engineers and designers, for the intended function. The building code regulators and users expectations expressed in explicit requirements of codes and standards can generally be addressed using a number of approaches and leave little room for interpretation. On the other hand, the expectations related to the intent of the code requirements and to the performance issues not covered by code are not so easily identified. Their identification generally requires judgment and can lead to many interpretations. The same applies to the expectations assigned by others, however, in some cases these can be quite explicit in nature. In any case, all these expectations need to be identified, for consideration, for the evaluation of innovations to establish the equivalent level of risk that society is willing to live with. It is generally expected that innovations or alternative-solutions will perform, at least, in the same fashion as minimum acceptable solutions such as the ones specified in codes in terms of prescriptive requirements. These acceptable-solutions have many attributes that can be considered as expectations for alternative-solutions. Some examples are inherent properties or product characteristics such as the impact resistance of an innovative cladding versus the one of traditional claddings. Impact resistance is not a primary function for cladding, but should an innovative cladding need to perform equivalently for impact resistance? Another is the long-term performance (durability) of composite plastic decking. Should innovative decking product

3 3 possess the same durability of pressure treated wood decking, which is the norm in the industry but not necessarily required in code in all locations? Of all these attributes, the long-term performance of a construction product/system would appear an expectation of great importance to the users. How one determines whether or not the expectations have been addressed in defining an evaluation strategy and process to establish the performance of an innovative product is the question at hand. Of particular concern, the issue that has caused many questions is the durability of key properties. In other words, should an evaluation determine if performance can be expected beyond the time of initial installation? Expectations related to the performance and longevity of products are defined or implied in various forms in documents such as regulatory documents (codes and standards), anticipated changes to regulatory documents and recognized scientific documents. Implied expectations are the most difficult to ascertain and quantify (e.g., how long will a fire-stop perform its function if there is a possibility of degradation), but to ignore them without addressing them could negatively affect the credibility of an evaluation service, and possibly result in complaints. Building and facility owners and operators expect certain performance from the products used to construct their facility. Expectations may be better handled if the evaluation organization has established guiding principles for the evaluation of innovative products. Manufacturers, regulators and users need to be made aware of these guiding principles to limit the level of their expectations with respect to the product evaluation provided by the organization. For example, CCMC is expected to address, within the scope of its evaluation, the following: All proponent-requested performance issues could be addressed. Code explicit requirements (example: health and safety) must be addressed. Performance issues should be addressed if there is some relationship to original health and safety expectations (explicit and implicit) of the code. Performance issues should be addressed if they are explicitly covered by a code referenced standard for similar product applications. Evaluation criteria could be established to assess performance levels, based on extensive scientific justification or the anticipation of code changes. Once a performance issue is addressed for a family of products of a specific material, then all similar products or materials need to be subjected to that issue, other than proponent requested claims. Performance issues must be addressed in relation to a product s intended application (use, climate, geography, etc.). These guiding principles were developed in the context of the Canadian regulatory framework and CCMC s mandate, but the intent of these principles may apply to the product evaluation or technical assessment performed by many organizations around the world. In fact, they are in line with the essential requirements defined by the World Federation of Technical Assessment Organizations (WFTAO). CANADIAN CODES AND STANDARDS Under the terms of the Constitution Act, regulation of building in Canada is the responsibility of provincial and territorial governments. The National Building Code of Canada (NBCC) has received wide use as the basis of provincial and territorial building codes. The content of the NBCC pertains primarily to the needs of health and safety. Requirements unrelated to health and safety are kept to a minimum; any requirements that would increase the scope of the NBCC are only considered after thorough consultation with regulatory authorities, provincial governments, other affected parties and code users. Requirements for workmanship related to aesthetics only

4 4 are not considered appropriate for the NBCC although requirements for durability that affect health and safety are appropriate. Many product standards and standardized test methods are referenced in the NBCC. Consequently, their content becomes part of the building code requirements, unless specified otherwise. The product standards and adjoining prescriptive code requirements are referred to as acceptable-solutions. The Standards Council of Canada (SCC) through the National Standards System (NSS) coordinates standards development in Canada. The NSS is a federation of organizations accredited by the SCC to standard writing, testing, certification and quality registration. A standard is generally defined as a consensus based document, which stipulates requirements for a product, service or installation. A standard can only be developed if a product is widely used by the construction industry, as the writing of standards require a representation of the users and the industry at large to meet SCC requirements. Consequently, a standard is not written for innovative products until they gain a certain level of acceptance within the industry. However, a solution is required to facilitate the acceptance of innovative products by authorities. Where a product is so novel that no appropriate standard and code requirements exist for the product, the regulators seek a third party technical opinion on the suitability of the product for its intended use for their acceptance. The regulators can choose from different avenues for third party opinions, but one that is clearly identified by the provincial and territorial governments is technical evaluation from the Canadian Construction Materials Centre. One of the reason why CCMC has received this level of recognition is that it is situated within the National Research Council of Canada (NRCC) where it has access to a network of experts within NRCC, from provincial research organizations, universities and the industry/private sector. By being part of NRCC, it also has access to the Canadian Code Centre which is responsible for the publishing of Canada s national model codes. This type of relationship between a product evaluation organization and established research organizations, universities and the industry/private sector plays a significant role in the establishment of its credibility nationally and abroad. International credibility benefits exporters of construction related products. Experience has shown that manufacturers of innovative products that obtain an evaluation from such organizations gain market acceptance more readily not only within their country but also internationally. TECHNICAL EVALUATION PROCESS The evaluation of innovative products is a dynamic process that includes at least five tasks, as depicted in Figure 1. Four of these tasks can apply to both prototypes and finish products, but the final evaluation can only be done on commercially available products.

5 5 FIGURE 1. Tasks Involved in the Evaluation of Innovative Products Scope and Evaluation Plan Acting within the spirit of the guiding principles mentioned above, the first step in the technical evaluation is the development of a scope and evaluation plan (SEP). A SEP lays out the groundwork for the evaluation and summarizes the technical issues that must be addressed in the evaluation based on the regulatory expectations, other defined expectations or manufacturer s claims. In Canada, the development of the SEP would require consultation with all provinces and territories to ensure that any major regulatory concerns are identified. Experts in various fields need also to be consulted to establish the technical issues that will need to be addressed. These experts may come from national or provincial research organizations, universities and engineering consultant firms. Ongoing dialogue with the client is required to scale the scope of the evaluation properly and to address any issues that might emerge from the discussions. These consultations play a major role in establishing the work plan and the team that will be required for the development of the protocol for the evaluation of the product. A SEP allows the manufacturers to understand what is involved in evaluating and gaining acceptance for their products in the marketplace before committing to the cost and time of the development of an evaluation protocol, and subsequently to the testing and the evaluation of their product. It also identifies how the evaluation needs to be undertaken, i.e., at the material level only or to the required performance with respect to the end use, and associated cost. Evaluation Protocol An evaluation protocol, referenced as a Technical Guide by CCMC, is a document that contains all the technical requirements for the evaluation. Generally an evaluation protocol will address material requirements with a view to characterization, performance requirements with a view to assess the intended usage, and sampling, quality assurance and installation requirements with a view to address consistency and tolerances. These requirements are developed on a case-by-case basis, as each innovation has its own characteristics and performance issues. Given the complexity and characteristics of the innovations seen today, the development of these requirements generally requires a multidisciplinary team of technical experts. First, the team of technical experts needs to determine the physical attributes the innovation needs to possess in order to behave in an acceptable manner, i.e., based on the building code

6 6 regulators and other defined expectations. The team needs to define physical requirements (i.e., test method and pass/fail criteria) to demonstrate that the product possesses the required material properties for the intended use, which will be used to characterize or fingerprint the commercialized product for the evaluation and future re-evaluation. The requirements can also serve as a basis for the manufacturer to formulate a quality control program to ensure that the characterized material is manufactured in a consistent manner. The development of the methodology to characterize the product can occur in conjunction with the manufacturer s product development process, which generally facilitate the commercialization of the innovative product. Secondly, the team needs to determine performance requirements for the assessment of the suitability-for-use of the product. The performance requirements that are determined set criteria with a view to establish the limits of the innovation being evaluated. For example, if the innovation is intended to be a structural component of a floor system, then it must resist certain loads, limit deflection and keep vibration under control. Once these values are determined they will set limits on the spans for the innovative framing member. Other performance issues would also need to be addressed, such as fire requirements. All code requirements and other defined expectations (either explicit or implicit) would need to be established and addressed in the evaluation protocol. The exercise undergone by the team of technical experts in developing the evaluation protocol usually involves dealing with a fundamental matrix of product properties and characteristics, and performance issues related to the intended use. An example of such matrix is presented in Figure 2. From this example, one can realize the sort of analytical process that is required when considering an innovative structural product/system. Firstly, the essential product properties need to be determined to assess performance. Once a methodology has been established to assess these properties, one need to consider the durability of these properties. In many cases, the durability of the properties (e.g., strength property) is linked to the type of material used (e.g., metal, plastic composites) and its resistance to degradation. Any adverse effect on the initial properties (e.g., initial strength property) needs to be measured for the evaluation. Degradation mechanism brought about by anticipated field conditions need to be considered for each case until it can be discounted as not being a concern. The material composition and behaviour over time of innovative products is generally not a known entity, and it needs to be quantified to conduct a proper evaluation or technical assessment.

7 7 FIGURE 2 Fundamental matrix in the development of a protocol for structural product evaluation Building Element or Intended Use Documented and Expected Requirements Mechanical, Physical, Chemical Properties Durability Against Degradation Mechanisms (1) Structural product Component (e.g., studs, joists, beams, etc.) Explicitly stated in code and standards: - steel - concrete - wood - masonry Implicitly stated in code and standards: - durability - shear - bending - compression - tension - fastener resistance - displacement under moisture and temperature differential - etc. - thermal - chemical - physical - weathering - freezing & thawing - photo degradation - corrosion - aging - biodegradation - moisture cycling - cyclic fatigue - etc. Structural product System (e.g., exterior wall, roof, floor, foundation wall, etc.) Explicitly stated in code and standards: - live & dead loads, - wind loads - seismic loads - combination of loads - environmental loads, e.g., moisture, temperature - engineering calculation procedure - racking - combined bending & axial - fire performance - tension - fastener resistance - displacement under moisture and temperature differential - etc. same as above Implicitly stated in code and standards: - durability (1) Comprehensive list of degradation mechanisms to be considered until certain degradation processes can be discounted and a subset of the list is formed for each proprietary product. To show this type of matrix at work, an example of an evaluation strategy for innovative wood thermoplastic composite exterior decking is presented in Appendix A. The example shows the application of column 3 (i.e., material/system physical properties) and column 4 (i.e., durability of these properties) of the matrix. Once completed, the evaluation protocol need to be reviewed by a group of professionals representing the building code regulators and other professionals that have experience with the acceptance of product in the field. Such a review provides a means to insure that the protocol addresses all technical issues and the range of expectations related to the product. For example, CCMC relies on a standing committee of technical evaluations composed of practicing engineers and building officials for such review. Ideally, the technical protocols that are developed for the evaluation of innovations should become the basis for the development of new standards once an industry has been established for this product line, which can then be adopted in building codes.

8 8 Testing Sampling and testing to the evaluation protocol need to be performed by agencies recognized by the evaluating organization. Product sampling is generally better handled by laboratories that have the expertise to perform the required testing, as they know the amount of material required and the test specimen preparation requirements. For increased credibility, the testing should be performed by laboratories that have their expertise reviewed by a national standard structure. For example, CCMC requires that the testing be performed by laboratories accredited by SCC for the test methods requested in the evaluation protocol. Where the test method is under development or when the testing requires special expertise, the testing may need to be performed by a research laboratory. The same will apply for engineering analysis or modeling where the expertise may lie only within research organizations or consulting experts. Evaluation Report The evaluation report is the document that contains the technical opinion of the evaluation organization based on its verification of the product performance with respect to the technical requirements of the evaluation protocol. The technical opinion is based on the results obtained from the testing of the product with respect to the pass/fail criteria that was set in the evaluation protocol. Where the product does not meet the set criteria, the test data needs to be assessed in terms of the risk that the disparity in performance imposes on the overall performance of the product. The assessment may results in limitations on the usage of the product or modification of the evaluation requirements. In any case, these limitations or modifications need to be based on sound technical rational. CONCLUSION The evaluation or technical assessment of an innovative or non-standard construction product, service or process is a difficult and complex undertaking. The selection or acceptance of these innovations is becoming impossible to do without the use of product evaluation from national evaluation organization that has access to a network of technical expertise. CCMC, as its counterparts in other parts of the world, operate within certain guidelines that ensure that the essential requirements are met. Some of these are explicitly stated, but often they are either implied in acceptable-solutions or obtained from in depth knowledge of the latest research. Owners, designers, specifiers and regulators now rely more and more on technical assessments of innovative products provided by national evaluation organizations for their decision making.

9 9 REFERENCES 1. Cécire, L., et al International Co-operation in the Technical Assessment Field, CIB World Building Congress, May, Toronto, Canada. 2. CCMC Technical Guide for Wood Thermoplastic Composite Lumber Used as Exterior Decking (Solid Cross-section), p. 22, Ottawa: National Research Council of Canada, Canadian Construction Materials Centre. BIBLIOGRAPHY 1. NRCC-CNRC Minutes of the Seventh Meeting of the Canadian Commission on Construction Materials Evaluation, Calgary: National Research Council of Canada, Canadian Commission on Construction Materials Evaluation. 2. Bergeron, D., Bowen, B Acceptable Solutions, Proceedings, CIB World Building Congress, Performance in Product and Practice, April, Wellington, New Zealand, paper number Adaire, A, Oleszkiewicz, I The National Building Code: Durability Requirements and their Incorporation into an Objective-Based Structure, Proceedings of the 7 th Conference on Building science and Technology, Durability of Buildings Design, Maintenance, Codes and Practices, March 20-21, Toronto, pp Ozer, Muanner Survey of New Product Evaluation Models, Journal of Product Innovation Management, Vol. 16, No. 1, pp

10 10 APPENDIX A CCMC s Evaluation of Exterior Decking Composed of Wood Thermoplastic Composite Lumber EVALUATION STRATEGY The technical requirements of CCMC s Technical Guide 2 (i.e., evaluation protocol) for the evaluation of innovative exterior decking composed of wood thermoplastic composite lumber (WTCL) can be divided in two groups: (i) material requirements and (ii) performance requirements. These requirements were developed for composite decking products made of a wood blend-based material and plastic(s), that contain less than 50% by weight of plastic, intended to be installed over traditional wood frame structure (Figure A1). The requirements were also developed for products intended for light duty application, e.g., residential occupancy. The WTCLs that were submitted for evaluation consists of solid cross section extrusions. FIGURE A1. Wood Thermoplastic Composite Decking Most of the technical requirements that were developed for the evaluation protocol, more specifically the performance-based ones, are universal in nature and applies directly to the evaluation of composite products made of a plastic material(s) and cellulose-based fibres, derived from wood residues or agricultural waste, that contain more than 50% by weight of plastic. Actually, these technical requirements are being used as the basis for the development of protocols for the evaluation of other innovative decking and guardrail systems made of generic group of cellulosic/polymer composite products. MATERIAL REQUIREMENTS As with all products there is an expectation that the base material will possess certain qualities or inherent characteristics in order for the product to perform satisfactorily, i.e., material properties and their durability. Consequently, material requirements were developed to establish if the wood thermoplastic composite material possesses certain minimum qualities, for classification purposes, before one proceeds to the more expensive performance testing. Some of these requirements are also intended to benchmark basic physical and mechanical properties of the product for future re-evaluation and for quality control. The material requirements were not developed to establish engineering design properties for the product. The basic physical and mechanical property requirements of the protocol include dimensional stability, strength, stiffness and fastener holding capacity requirements. These requirements

11 11 were developed in some instances with respect to the intended-use of the product and in other instances with respect to the plastic nature of the product. For example, the requirements include an Izod impact resistance test as it was viewed as a critical test to characterize the behaviour of plastic-based products. The requirements also include a hardness test that can be associated to the end use of the product. For example, if the product is not sufficiently hard it may become a safety issue for people wearing shoes with small diameter heels walking over the deck. The requirements include a creep test that can be associated to both the end use of the product and its plastic nature. The creep test procedure referenced in the evaluation protocol is an established inexpensive test, which can be performed by the manufacturer in-plant and may serve as an on-going in-plant quality control test. The protocol also includes requirements to verify the ability of the product to maintain its key properties after aging. PERFORMANCE REQUIREMENTS The WTCL exterior decking is intended to perform, as a system, a structural task under variable and extreme environmental conditions, i.e, degradation mechanisms. It is expected to perform this structural task over an acceptable period of time. The structural performance of the system need to be assessed in terms of these applicable end-use and environmental loads. The ability of the systems and their components to maintain their inherent characteristics over time need also to be assessed as part of the evaluation of the suitability for use of the product. There are two approaches that could be taken in evaluating the structural performance of exterior decking. One is to establish the structural design properties of WTCL for use in engineering analyses (analytical approach). This would allow for engineering design for applications beyond decking and guardrail applications. However, it would be a costly and time consuming approach, as it would require statistical sampling for product variability, assessment to establish the limit state design properties of WTCL and account for loads and environmental effects or influences on the mechanical properties of the product (e.g., temperature, moisture, creep, and combinations of these). The other is an empirical approach that focuses on the performance of the actual system (e.g., decking + fasteners as assembled) for its specific end-use application. This approach eliminates the need to establish the structural design properties of WTCL, but requires the full scale testing of assemblies representative of the field installation. This approach was chosen as it was viewed as the simplest and least costly approach to establish the suitability-for-use of these innovative decking. Technical requirements were developed to address the structural response of the decking as installed under the expected structural and environmental loads to which it will be exposed. Requirements were also developed to address the long-term performance of the decking in terms of the durability, the decay resistance and the termite resistance of the wood thermoplastic composite lumber. Structural Performance Expectation The structural performance requirements for the evaluation of decking systems are based on concentrated static and impact load tests on full scale test specimens that include three supporting members. The pass/fail criteria were obtained from CSA standard CAN/CSA-O , Required Resistances to Concentrated and Impact Loads for Construction Sheathing. CAN/CSA-O is referenced in Part 9 of the NBCC for the rating of subfloor sheathing. The loads defined in CAN/CSA-O were viewed as the minimum of the acceptable-solutions defined in Part 9 of the NBCC and not lumber decking, which some user may expect. These structural tests are conducted at three different temperatures (50 C, 20 C, - 35 C) to verify the temperature effects on the structural performance of the decking system. As experience is gain with this type of product and a critical temperature can be defined for the structural tests, testing at different temperatures may not be required.

12 12 Durability Against Degradation The durability requirements involve exposure of the wood thermoplastic composite lumber to both weathering (UV and Moisture) and freeze-thaw cycles. The requirements were developed to address the combined effects of weathering and freeze-thaw, which is the case in-service. The pass/fail criteria are based on the percentage change of the mechanical properties of the wood thermoplastic composite lumber in reference to spruce lumber used as a control specimen. The decay requirements were developed to assess if the resistance to wood decay-causing fungi of wood thermoplastic composite lumber was equal to or better than untreated spruce heartwood. If the manufacturer claims that the decay resistance of the wood thermoplastic composite lumber is equal to or better than preservative-treated wood or naturally durable wood products, the decay resistance of the composite product is evaluated in reference to preservative-treated wood conforming to CSA standard CAN/CSA-O80.1-M89 (i.e., acceptable-solution defined in the NBCC) instead of untreated spruce heartwood. The same applies if the wood thermoplastic composite is intended to be used where the vertical clearance between the ground and the composite product is to be less than 150 mm. Termites are known to occur in certain localities in Canada. Consequently, requirements were developed to assess if the resistance to termite of wood thermoplastic composite lumber is equal to or better than preservative-treated wood conforming to CAN/CSA-O80.1-M89. The wood thermoplastic composite lumber need to be tested for termite resistance only if the product is intended to be used where the vertical clearance between the ground and the composite product is to be less than 450 mm in localities where termites are known to occur.