Test building and instrumentation

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The building geometry was selected to be of rectangular shape with a gable roof and the platform construction method was used to form the structural system. This particular technique is currently the most conventional construction method in which the wall framing is erected on top of the floor system. The building has external dimensions of 8.6 x 17.2 x 5.6 meters (W x L x H) and a duo-pitch roof of 4/12 slope. It is resting on a concrete foundation wall 0.225 m thick and 1.225 m deep. The geometry and dimensions of the building are shown in Figure 4.2.

The floor system of the test building consists of 43 I-joists directed along the small side of the structure. The I-joists (JSI 40) have a total height of 508 mm and they are spaced at 406 mm (centre-to-centre distance). On the top of the I-joists, 15 mm thick OSB (Oriented Strand Board) panels 1.22x2.44 m have been nailed and create a solid diaphragm on the floor.

The wall system consists of wall frames, sheathing and siding panels. The wall frames are assembled from 38x89 mm studs spaced at 600 mm. The studs are made by spruce- pine-fir lumber (S-P-F). Studs are also used for bottom (one stud 38x89 mm) and top (two studs 38x89 mm) plates in order to form the framing wall system. On the exterior side of the wall, OSB panels of 9.5 mm thickness are used to cover the framing. A final layer of stained wood is used as siding. The internal side of the frame walls and the ceiling are covered with plasterboards of 9.5 mm thickness. No partition walls are installed thus only the exterior walls serve as lateral force resisting system.

The ceiling of the test building consists of a grid of 38x89 mm and 19x89 mm studs, which are fastened to the bottom of the roof trusses. The roof trusses are prefabricated fink trusses (W-trusses) spaced at 600 mm and comprised of 38x89 mm lumber elements.

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Two door openings exist on the building, one door on the east and the other on the west wall. The orientation of the building is 43 degrees right of the geometric North which was assumed to be the reference zero point for all direction measurements. More details about the construction of the test building can be found in Doudak (2005) and Zisis (2006).

Figure 4.2 External dimensions of the experimental building.

The test building is equipped with 40 pressure taps, 12 of them on the wall and 28 on the roof, as shown in Figure 4.3. The pressure taps were installed at an earlier stage of the project and the installation of additional sensors, although very desirable, was not really possible considering the general system configuration (limited number of ports available in the data acquisition system). The majority of the roof pressure taps were distributed on top of three pre-selected frames and were equally spaced from each other. The closest tap to the eave of the roof was at a distance of 1.6 meters and the closest to the ridge at a distance of 0.2 meters. The system consists of 4.8 mm inside diameter plastic tubes mounted on the wall and roof surface and connected to differential pressure transducers

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(Micro Switch 160PC). These transducers use as reference pressure the ambient atmospheric pressure, which is provided by the barometric pressure scanning system.

Figure 4.3 Pressure tap location on the test building.

Particular attention was given to the protection of the tubing from humidity, condensation, dust and section obstruction. For this reason, special techniques were used for the roof pressure taps to drain the rain water from them and protect also the transducers.

Full-scale pressure measurements are highly affected by the way of measuring the reference atmospheric pressure. The differential pressure transducers measure surface

PR75 PR78 PR80 PR74 PR76PR77 PR79 PR41 PR43 PR46 PR48 PR42 PR44PR45 PR47 PR1 PR59 PR62 PR2 PR3P R4PR5 PR6P R7 PR8 PR19 PR22 PNE,6 PNE,7 PNW,6 PNW,8 PNW,10 PSE,6 PNW,15 PSE,8 PSE,10 PSE,15 PSW,6 PSW,7 PR73

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wind pressure using as reference the ambient atmospheric pressure. Therefore, the test building was equipped with a Young (R. M. Young Company, 2001) barometric pressure sensor, monitoring the ambient atmospheric pressure. The sensor is located outside the building and is mounted on the south wall. The combination of a regular pressure sensor (Young - model 61202) housed in a waterproof molded case and a pressure port (Young - model 61002) minimized significantly the dynamic pressure errors due to wind. The pressure port uses two parallel plates in order to reduce significantly the approaching wind velocity before it hits the pressure inlet. In addition an internal baffle system protects the barometer from water and snow penetration.

The load cell system is an innovative part of this study. A total number of twenty- seven 3-D load cells were placed around the perimeter of the building at the foundation- to-wall interface (Figure 4.4a). Another six 1-D load cells were also installed between the wall top plate and three of the roof trusses (Figure 4.4b). The location of the load cells is shown in Figure 4.5. It should be mentioned that the building is completely isolated from the foundation and the only points of contact are the 3-D load cells. This construction detail assures the transfer of the applied load to the foundation only through the load cells.

In addition to the pressure and stress sensors, temperature monitoring equipment is also used. Thermocouples are installed in such way so monitoring of internal, external, foundation concrete wall and foundation load cell housing can be monitored simultaneously to the rest of the sensors.

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(a) (b)

Figure 4.4 (a) Foundation and (b) roof load cells placed in the foundation to wall and wall to roof interfaces.

Figure 4.5 Roof and foundation load cell location on the test building.

LNW,1 LNW-R,1 LSE-R,1

LNE,1LNE,2LNE,3 LNE,4LNE,5

LNW,2 LNW,3 LNW,4 LNW,5 LNW,6 LNW,7 LNW,8 LNW,9 LSE,1 LSE,2 LSE,3 LSE,4 LSE,5 LSE,6 LSE,7 LSE,8 LSE,9 LSW,1 LSW,2 LSW,3LSW,4 LNW-R,2 LSE-R,2 LNW-R,3 LSE-R,3

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Finally, the System 5000 (Vishay System Model 5000, Intertechnology) was used for data acquisition and reduction. This stress analysis data system is able to accept simple strain gages (load cells), linear variable differential transformers (LVDT’s) and high frequency sensors (pressure tap transducers). The system is operated by sophisticated software (Strainsmart Software) provided by the same company. This Windows-based software can export the acquired data in different formats (ASCII, EXCEL, ACCESS database).