1、1,BUILDING MATERIALS AND SYSTEMS : EVALUTION AND SELECTIONPresented byDr. Abdul-Mohsen Al-Hammad,2,IntroductionThe Need for a Rational ApproachProposed Evaluation and Selection methodThe Case Study(Exterior Wall Systems)Application of the MethodConclusion,CONTENTS,3,People who are involved in constr
2、uction industry and require a more rational approach to evaluate and select building products are :Architects and engineersConstruction ManagersSubcontractorsBuilding Material manufacturersToday,there is no unified rational approach for evaluation and selection a building product.,INTRODUCTION,4,His
3、toric Account of Material UseStoneMarble Used in Egyptian and Greek TempleBrick & Concrete Romans timesSkilled in these materials were perfected,THE NEED FOR A RATIONAL APPROCH,5,No. of Materials used in different time periodsDevelopment of steelDevelopment of many synthetic productsDevelopment of p
4、roducts that resulted fromHuman performance Natural resources Technological capabilities,THE NEED FOR A RATIONAL APPROCH ( Continued),6,For Examples:In Concrete there is about 60 variables fromMixing ,curing temperature,w/c ratio,etcIn synthetic products, many variables affect themSweets Catalogs in
5、 1906 one volume 150-200 manufactures are listedNowadays, more than 45 vol. annually are issued One vol. Adds more than 2,300 Catalogs file each year as brand catalogs for new materials,THE NEED FOR A RATIONAL APPROCH ( Continued),7,Testing and research for evaluation has not been able to keep pace
6、with the no. of newly developed productsThis enables products to be used or marketed before the design professional can be assured that the products do indeed fulfill the desired requirements.,THE NEED FOR A RATIONAL APPROCH ( Continued),8,The question is how design professional evaluate & specify a
7、 new productDo they depend on the manufacture literature onlyWhat kind of the question the designers should ask the manufacturer?Thus,there is a need for the design professional to use a rational approach to evaluate and select the products,THE NEED FOR A RATIONAL APPROCH ( Continued),9,The method o
8、f judging ideas as suggested by (Parker 1985) was used as a rational approach since it considers economic and non-economic criteria for selection.This method will consist of subjecting different materials or systems to certain screening processes, namelyfeasibility ranking, evaluation by comparison,
9、 weighted evaluation which involvescriteria evaluation, and matrix evaluation.,PROPOSED EVALUATION AND SELECTION METHOD,10,Exterior building wall systems evaluation & selection will be used a case studyWalls for buildings can be constructed in various ways using a variety of materials. Exterior wall
10、s serve as a protective shield against exterior conditions for a buildings interior spaces (Greeno 1986). An architect faced with a variety of alternative exterior wall systems.An evaluation and selection technique for exterior wall systems that are available in Saudi Arabia will be used.,THE CASE S
11、TUDY (Exterior Building Wall Systems),11,In Saudi Arabia, or elsewhere, the architect/designer has a number of alternative exterior wall systems. The first approach requires the list of all possible alternatives for each particular building project. In this case, based on a field survey of the Saudi
12、 market, fourteen wall construction systems were identified as the most commonly used systems. An outline of these systems along with a brief description of their assemblies is presented in Table 1. For further illustration, Fig. 1 shows cross sectional areas of samples of these systems.,THE CASE ST
13、UDY (Exterior Building Wall Systems) (continued),12,The method will consist of subjecting the different wall systems to certain screening processes, namelyfeasibility ranking, evaluation by comparison, weighted evaluation which involvescriteria evaluation, and matrix evaluation.,APPLICATION OF THE M
14、ETHOD,13,As a rough screening process, five factors were used for the first filtering process of judging alternatives. Field experience should be used to reach a decision at this filtering process.These five factors are state of the art of the idea, cost to develop the idea, probability of implement
15、ation, time to implement and potential benefit.These factors are scored on a one to 10 basis, with 10 being the score for least cost, least time, most benefit, highest probability of implementation, and most current state of the art.The feasibility ranking of the exterior wall system alternatives is
16、 given in Table 2.,FEASIBILITY RANKING,14,A decision is now made by the evaluator to drop those ideas whose total points are below a certain number, namely 30 points.Therefore, five alternative ideas are dropped: double faced rubble wall, metal framed wall, plastic wall panel , timber wall panel, an
17、d glass wall system. As can be seen, scoring in the first screening step is subjective. This is mainly due to the fact that what might be new technology to one person, might not be so to another. However, no alternative is discarded without being scored.,FEASIBILITY RANKING (Continued),15,The remain
18、ing alternatives will be subjected to a second screening process, called evaluating by comparison, in which the advantages and disadvantages of each alternative are listed. Then ranks are given based on a subjective assessment by the evaluator of the relative advantages or disadvantages of each alte
19、rnative.The advantages and disadvantages may be equal in number, but they will not be equal in strength or importance. Evaluation by comparison is presented in Table 3.A decision is made to drop those ideas whose ranking is above four. Therefore, four alternative ideas were dropped:,EVALUATION BY CO
20、MPARISON,16,The performance criteria that are considered to be important in the final selection of exterior wall system alternatives, were obtained from a survey of professional designers and consultants. These criteria were evaluated through a survey of 25 randomly selected designers and consultant
21、s The purpose of conducting this survey was to test the soundness of these criteria and to see whether any more criteria In order to get a relative weight of each criterion, the techniques of probability and expected value were used,CRITERIA EVALUATION,17,Table 4 shows the evaluation terms with thei
22、r weights.Table 5 illustrates the criteria with the various responsesExpected value of responses (E(x), mean response, severity indices (S.I.), and ranking as obtained from the survey findings. No additional comments regarding additional criteria were obtained from the survey. The result of the surv
23、ey as shown in Table 5 indicates that all sixteen criteria are important for an evaluation and thus, they will be used to evaluate the wall systems.,CRITERIA EVALUATION (Continued),18,The four alternatives which passed the two filtering processes are now subjected to a third screening process called
24、 weighted evaluation.This system of evaluation is divided into two processes: paired comparisons of criteria and matrix evaluation.,WEIGHTED EVALUATION,19,Fig. 2 illustrates the methodology used to compare the performance criteria in order to determine the weight of each criterion. Each of the sixte
25、en criteria is assigned a letter of the alphabet and then compared with each of the other criteria based on the preference of the owner and/or the designer for each particular project.The importance of one criterion over another can be major, “4”, medium, “3”, minor, “2”, and slight, “1”.After all c
26、omparative evaluations are made, the raw score of each criterion is totaled by summing the assigned letters in the matrix.Now, the raw scores are adjusted to a scale of 1-10 with 10 being assigned to the criterion with the highest raw score, and the other criteria adjusted accordingly as shown in Ta
27、ble 6,PAIRED COMPARISONS OF CRITERIA,20,In this process, all remaining alternatives from the previous screening stages will be evaluated against the above-mentioned criteria. It is assumed that all the alternatives that have survived meet the minimal needs or basic functions of the owner or the user
28、.The scoring system used in this analysis matrix involves assigning 1 to 5 points on a scale of poor to excellent. The ranks of each alternative were multiplied by the corresponding weights of the criteria, and the resulting scores entered into the matrix. The total scores were then determined for e
29、ach alternative.,THE EVALUATION MATRIX,21,Based upon the previous analysis, the insulated reinforced block cavity wall system is considered the best choice.,CONCLUSION,22,Al-Hammad.A. and Hassanain A.”Value Engineering in the Assessment of Exterior Building Wall Systems” Journal of Architectural Eng
30、ineering,1996,Vol.2 No.3.Green,R.”Principles of Construction”,1986, 1st Ed. Longman Scientific & Technical ,Singapore.Parker,D.E.”Value Engineering Theory”,1985,The Lawrence D. Miles,Washington.D.C.Rosen,P.E. and Bennett,R. A.”Construction Materials Evaluation And Selection A Systematic Approach”,19
31、79,John Wilely & Sons Inc. New York,N.Y.,REFERENCES,23,TABLE 1: Exterior Wall Systems,24,TABLE 2: Feasibility Ranking,25,TABLE 3: Evaluating by Comparison,26,TABLE 4: Evaluation Terms and their Weights,27,FIG. 2. Criteria Scoring Matrix,28,TABLE 6: Evaluation Terms and their Weights,29,TABLE 7: The Analysis Matrix,30,THANK YOU,
