CARDIFF SCHOOL OF ENGINEERING EN1917 PROFESSIONAL ENGINEERING LABORATORY REPORT: CENTRE OF PRESSURE STUDENT NUMBER: STUDENT NAME (1st 3 lette DATE OF EXPERIMENT: DATE OF SUBMISSION: 21127316 1 1. Abstract: By doing an experiment using the centre of pressure, it is possible to demonstrate that hydrostatics force and weight are similar in measurement using the theory of force in a flat submerged surface. Weights are applied to push the scale over its pivot point, and water is then poured to bring it back to level. Findings and data show that there is a linear relationship between theoretical and experimental hydrostatic pressure force for the partially submerged surface as well as the fully submerged. Table of contents 1. Abstract..... 2. Introduction... 3. Theory...... 4. Procedure. 5. Results.... 6. Discussion........ 7. Conclusion........ 8. References.... .2 .2 .3 2. Introduction The pressure that a fluid exerts at a particular spot inside the fluid as a result of gravity is known as hydrostatic pressure. With increasing depth, hydrostatic pressure rises proportionately (EDinformatics, 1999). The experiment focuses on balancing and calculating the hydrostatic moments and the weight masses to establish the theoretical and centre of pressure along with the hydrostatic forces occurring on both partly and fully submerged bodies. If at 10 degrees angle, the hydrostatic moment is straight and angled vertically when being both submerged and not submerged, the theory would be accurate. 2 3. Theory Hydrostatic pressure: P = pgh = wh The centre of pressure is made to measure the static hydrostatic force that a fluid exerts on a submerged surface (Jasim, 2022). The equivalent of the pressure applied at the liquid's surface needs to be added in order to measure the absolute pressure at depth: Pa = Ps + P = Ps + wh The moment applied is not proportional to the water height when the plane is partly submerged since the water only covers a section of its surface. On the other hand, water covers the whole area of the plane when it is fully submerged, hence the moment applied. Should be inversely proportional to the water height (Araydah, 2019). Calculations: a=0°; M₁ = mg R3 Fully submerged: h₁ = R1-x and h₂ = R2 - X hG= (h1+ h2)/2 a=0°; M₁ = mg R3 Partly submerged: h = R₂-x hG=h/2 A = h B A = (R2 - R1) B F = rghGA F = rghGA = hp (IG/A hG) + hG where IG = B D 3/12 hp = (2/3) h DLA = x + hp M2 = F DLA (Millington, 2022) DLA = x + hp M2 = F DLA a = 10°; M₁ = mg R3 cos a Fully submerged: h₁ = R1 cos a-x and h₂ = R2 cos a - x hG (h1h2)/2 and LG = hG / cos a = A = (R2 - R1) B a = 10°; M1 = m g R3 cos a Partly submerged: h = R2 cos a-x hG=h/2 A = (h/ cos a) B 3 F = rghGA hp = cos a [(IG / A LG) + LG] where IG = B D 3 / 12 DLA = (x + hp)/cos a F = rghGA hp = (2/3) h DLA = (x + hp) / cos a M2 = F DLA (Millington, 2022) M2 = F DLA 4. Procedure Foot screws and bubble level were used to set the apparatus on a flat Surface. An empty weight hanger was used to suspend the support. Because of the disturbance in balance, water was added to the quadrant to level the tank and make sure the submerged plane was vertical and at Omm. A beaker and syringe were used to add water to the quadrant until the 0° point was achieved in order to regain balance. The surface and the distance between the pivot point were measured in mm. The stages were repeated along the way while the weight was steadily raised by increments of 40g up to 560g. Results were obtained and recorded after repeating the process at a 10° angle. Sliding weight m R1 R2 R3 Plane of breadth, B Levelling bubbles 0 Levelling foot-screws X Quadrant Figure 1: Centre of pressure apparatus (Millington, 2022) 4 5. Results Table 1. Centre of pressure on a plane, vertical, unsubmerged immersed surface Observations Theory: Partially Submerged Weight Mass Distance from pivot to Depth to Water moment Water depth Depth to centroid Area Force centre of moment Lever arm surface pressure HG=[h+(R1- F=p g hp= (2/3) DLA=x+hp M2=FL m M1= mgR3 X h=R2-x A=h x)]/2 hGA g Nm mm m m M² N m m Nm 40 0.0981 161 0.039 0.0195 0.00293 0.56 0.0260 0.187 0.105 80 0.1962 144 0.056 0.0280 0.00420 1.15 0.0373 0.181 0.209 120 0.2943 130 0.070 0.0350 0.00525 1.80 0.0467 0.177 0.318 160 0.3924 119 0.081 0.0405 0.00608 2.41 0.0540 0.173 0.418 200 0.4905 110 0.090 0.0450 0.00675 2.98 0.0600 0.170 0.507 240 0.589 100 0.100 0.0500 0.00750 3.68 0.0667 0.167 0.613 Distance to water surface from pivot, x[mm] 180 160 140 120 100 80 60 40 40 20 0 40 80 80 120 160 200 240 280 Mass, m [g] 320 360 400 440 Figure 2: Vertical plane: distance to water surface from pivot point(x) for varying mass(m) 5/n Guidelines Hygro Lab Determination of the pore structure within concrete is a key indicator of its long-term durability. Where density is the substances mass per unit volume and open porosity works on the assumption water penetration and as a result potential contaminant. This is particularly relevant for steel that internal pores are all connected. A higher porosity and therefore, lower density allows increased reinforced structures where chloride penetration and can induce electro-chemical corrosion of the reinforcement. Due to the reinforcement being embedded in the cementitious matrix, steel degradation goes unnoticed resulting in a tensile structural failure. Materials of a traditional kiln dried clay brick, autoclaved aerated concrete (AAC) block and dense concrete block all shown in figure 1. Further guidance can be found in British Standard BS EN 12390-7:2009 Testing hardened concrete Part 7: Density of hardened concrete (British Standards Institution 2009). The samples provided have been oven dried at 60 °C for 5 days and allowed to cool to ambient temperature prior to your lab. Figure 7: Two concrete block section Clay brick Autoclaved aerated concrete (AAC) Equipment required This experiment requires: · Testing materials (clay brick section, aerated block section, two concrete block section). • Scales. Measurement device (ruler or callipers). • Bucket half full of water. • Dry cloth. Archimedes tank with stirrup. Experimental Procedure Ensure the scales are zeroed and dry prior to taking mass values. · For each sample record its name width (w), depth (d) and height (h). • Take and record the dry mass (mary) of all three samples individually using the scales. Place the samples into the bucket of water and leave for one hour. Move to experiment two, Sorptivity whilst the samples saturate. • Remove excess water by patting dry the saturated samples with the cloth. Place the now saturated samples individually onto the scales and record the saturated mass (msat). Place the saturated mass on the stirrup into the density frame and record the Archimedes mass (mArc). Answer the problems in the worksheet. 66 Hygro Lab Density and Porosity Log Data and analysis Enter the initial specimen dimensions to the nearest 0.1 mm in the following table: Specimen Width, w (mm) Depth, d (mm) Height, h (mm) Volume (mm³) Concrete 61 95 215 1245 925.0 concrete 2 62 98 213 1294188.0 clay 63 99 127.70 7920 99.6 AAC 64 98 214 1342268,0 Record the mass of each specimen to the 2nd decimal point. Specimen Dry mass, mary (g) Saturated mass, msat (g) Archimedes mass, marc Concrete 250.0 277366 (g) 1534,8 Concrete 2605.3 282440 1537.5 clay 1937.1 15.21.8 844.7 A AC 92 4.7 1189.3 Calculate the bulk density, matrix density and open porosity values using the formulae provided below. Check units carefully. Formula provided below. Note: Pw = 997 m3 can use pw = 1000 Formula 1-Volume: V= msat-mArc Pw 2 Bulk density Pbulk = msa mdry V * mdry 3-Matrix density Pmat = Vmatrix 4- Volume of pores V pores msat-mdry Pw 5- Total Volume Vtotal = Vpores + Vmatrix Vpores 6-Open porosity (Po V Using the formulae above, calculate the bulk density, matrix density and open porosity in the table below. msat 217736 m Dry mArc 67 1.5348 21824 1.5218 1.1893 2.57 1.4371 0.9247 1.5375 2.6053 0.8447 4 Specimen Bulk density, Pbulk (kg/m³) Hygro Lab Matrix density, Pmat (kg/m³) Open Porosity o (-) Concreate 2067.5 2474.0 0.164 Concrete 2019.6 2433.3 0.17 Clay 2162 2418.7 0.125 1 A AC 1 4 5 VT Vpore Vmatriy 1 1.243×10-3 2.042×10 -3 2 1.290×10 2.193 × 10- 3 6.791 × 10 4 8.495 × 10 5 01903 1.0707 × 103 5.9415×10 -4 -4 07799 1.0388×103 2.653 x 104 68 99 M Assessment questions might they be different? Hygro Lab 1. How does the volume experimentally determined compare to that by measurement? Why To compare the clay VT 6,791 × 10-4 m³ 7,920 x 10 x m³ it's diffrent frow what we expected initally in our in our first caculation at may be because of the unperfect shape sh 1 aperfect ари 2. Compare the open Porosity of the samples. What do your results tell you? The 1 concreate has 0.164 open porosity while the 2 concreate has oil? this mean that 2. concreat has a larger particle Size which mean it's have a higher open porosity 69 69 Hygro Lab Experiment 2 -Sorptivity Guidelines Sorptivity testing measures the water uptake through capillary rise within a pore structure over time. open porosity. Sorptivity testing can be used to measure to characterise the resistance to ingress The sorptivity rate can be affected by mineralogical composition of the sample but predominantly the additionally, it can be used to determine the healing potential of concrete. Sorptivity testing falls into two stage primary and secondary, for this lab you will only consider primary. Unsaturated flow theory shows that porosity is due to capillary forces which are greatest on dry specimens and become negligible on saturated. Materials This experiment determines the sorptivity rate which is the height of absorption over the square root of time. The samples (Clay brick section, Autoclaved aerated concrete (AAC) section, two concrete block section) provided have been oven dried at 60°C for 5 days and allowed to cool to ambient temperature prior to your lab (Figure 2). Clay brick Two concrete block section Autoclaved aerated concrete (AAC) Figure 2- Testing materials for sorptivity Equipment required This experiment requires: Testing materials (clay brick section, aerated block section, two concrete block section) • • Scales Measurement device (ruler or callipers) • Plastic water tray Sample supports (washers) • • Water Stopwatch Cloth Equipment and Procedure 1. For each sample record its name as well as width (w), depth (d) and height (h). 2. Place the plastic water tray on a flat, level surface. 3. Place a washer under each corner of every sample inside the plastic water tray, ensure correct spacings. 4. Pour water into the container to 5.0 ± 1.0 mm above the washers. 5. Record the dry mass of each specimen. 70 70

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CARDIFF SCHOOL OF ENGINEERING EN1917 PROFESSIONAL ENGINEERING LABORATORY REPORT: CENTRE OF PRESSURE STUDENT NUMBER: STUDENT NAME (1st 3 lette DATE OF EXPERIMENT: DATE OF SUBMISSION: 21127316 1 1. Abstract: By doing an experiment using the centre of pressure, it is possible to demonstrate that hydrostatics force and we