# I. Introduction he world faces today the big challenge of traffic accidents that harvest annually millions of human lives (Muhammad, 2013). The consequences of these traffic accidents do not only affect the victims or their families, but extend to the impact the community and its progress (Muhammad, 2013). Pedestrian bridges are structures made for allowing pedestrians to cross a street/road/highway without being exposed to the risks of car accidents. A pedestrian bridge is any structure that removes pedestrians from vehicle roadway (Muhammad, 2013). The first pedestrian bridge in Nigeria was a steel structure erected at Idumota cenotaph on Lagos Island (The Guardian, 2015). However, according to the Guardian newspaper, two such concrete bridges were also constructed: one in Iddo railway terminals across the road and the second was from Oyingbo to Otto near the old Leventis mainland hotel. The two bridges were planned towards the 1960 independence celebration. The construction work was carried out by Taylor Woodrow Construction Company (The Guardian, 2015). It was a major event on its own in those days especially considering the swampy terrain that the bridges were required to cross through. With the advent of the third National Development Plan (1975)(1976)(1977)(1978)(1979)(1980), reinforced concrete bridges on piles and prefab deck were constructed over Apapa-Oshodi expressway and the Agege Motor Way at Ikeja. A bridge is a structure that provides passage over an obstacle such as valley, rough terrain or body of water by spanning those with natural or manmade materials (Newman, 2003;Mosley and Bungey,1999;Jeswald, 2005). According to Mugu (2004) a footbridge or pedestrian bridge is principally designed for pedestrians and in some cases cyclists, animal traffic and horse riders rather than vehicular traffic. Recently the Lagos State Government erected a multi-functional pedestrian structure at Oshodi (The Guardian, 2015). The current governor of Lagos State, Akinwumi Ambode, has approved the construction of pedestrian bridge at Berger area of the State to give room for easy crossing by pedestrian of the ever busy Lagos-Ibadan expressway (P M News, 2015). In Benin City, Edo State of Nigeria, there was a pedestrian steel bridge constructed at close proximity to the University of Benin main gate but was dismantled because of the dualisation of the road by the Edo State Government. Types of pedestrian bridge include: simple suspension, clapper, moon, stepstone and zigzag bridge Increasing rate of accident at the hostels' gate of Auchi Polytechnic is worrisome. This involves either two or more vehicles or at times two or more motor bikes. The fatal ones always attract the attention of the Federal Road Safety Corp (FRSC) who needs to evacuate the vehicles and the injured in order to allow the free flow of traffic. The main victims of hit and run by vehicles and bike riders especially at night have been the students living on and off campus of Auchi Polytechnic, Auchi. Thus this development necessitates the design and construction of a pedestrian bridge across the Auchi-Benin highway. # II. Materials and Methods # a) Study Area This study focuses on the design of pedestrian bridge across the Auchi-Abuja Highway in front of Auchi Polytechnic, Auchi main entrance gate. b) Design consideration, calculations and analysis i. # Soil Test The following geotechnical parameters were determined as follows: (%) = ?????????????????????????????????????????????? % ??????????????????????????????????????? [2] Coefficient of uniformity (cu) = ??30 ??60 ? x D10 [3] Coefficient of uniformity (cu) = ??60 ??10 ? [4] ii. Specific Gravity Test (Gs) Given: Gs = (M 2 -M 1 )/ (M 2 -M 1 )-(M 4 -M 3 ) iii. Density Test Volume of cutter (V), mass of wet soil (M), Bulk density and dry density were computed as follows: ?? = ???? 2 ?? [5] M= M 2 -M 1 [6] Global The outputs of the design analysis indicate that the chosen sections for all the structural members of the footbridge are adequate in term of ultimate and serviceability considerations. The soil analysis shows that it would be able to withstand the load from the columns and vibrations from vehicular movement. 2![Calculation for Coefficient of Consolidation under StressAo =1.594; Af = 1.678; T50 = 0.018; A50 = 1.640 Note: These values were read off from the consolidation graph. 018) 2 = 0.19?? 2 /???????? Determination of Co-efficient of Compressibility (Av)](image-2.png "2") ![](image-3.png "") 1S/NObservation and CalculationsDeterminationNo121Density4267.04331.02Weighty of Empty Bottle (M 1 ) (g)26.626.63Weighty of Bottle +Sample (M 2 ) (g)56.656.64Weighty of Bottle + Sample H 2 O (M 3 ) (g)94.094.15Weighty of Bottle + Sample + H 2 O (M 4 ) (g)77.676.66M 2 -M 1 (g)30.030.07M 4 -M 3 (g)13.613.58Gs2.22.2ResultDensity Gs = 52.22.2Field data, 2016 2S/NObservation and CalculationsDeterminationNo121Core Cutter No501.0502.02Internal Diameter (cm)10.010.03Internal Height (cm)13.013.04Mass Of Empty Core Cutter (M 1 )g900.0900.05Mass Of Core Cutter With Soil (M 2 )g2900.02600.06Mass Of Wet Soil M= M 2 -M 12000.01700.07Volume Of Cutter (V) (cm 3 )1021.01021.08Moisture Content0.10.29Bulk Density = Wt of Soil / Vol of Cutter (g/cm 3 )1.961.6710Dry Density (g/cm 3 )1.751.45Field data, 2016 3Test No.LoadShear Stress at Failure (KN/M2)Normal Stress (KN/M2)11038.049.022056.077.033066.0104.3Field data, 2016 4TimeMass 1Maxx 2Mass 3(Seconds)10 kg20 kg30 kg510115120130160190113120229561504467518016548721030619324040719327047761063005082105330528610936053871123905792115420619745062480655106554066570600630660690720Field data, 2016 5?H?e = 0.0565 ?H? = ? -?eh = Ho -?HEffective Stress00.000000.51320.000.00000.860.048590.46419.14100.1021.160.065540.44818.84200.2041.430.080790.43218.57300.3061.590.089840.42318.41400.4081.690.095490.44818.31500.501Field data, 2016c) Design of Structural Elements=4.62x106/160 x 225i. Live Load for Footbridge4620000/36000=128.33mm 2For loaded length in excess of 30mWidth of the flanges is within the range of 0.5dLive load, qk = k x 5.0KN/m 2[17]=0.5x160mm=80mm128.33/80=1.604; assume 2mmWhere,Assume a plate size 80mmx2mmK= nominal HA UDL for appropriateArea=80x2=160mm 2 >128.33mm 2loaded length (in KN/m) 30 KN/m[18]The section chosen for the plate girder flanges as OK, the plate can be used.HA value for loaded length (32.4m) = 29.1 KN/mAdopt the section 80mmx2mmTherefore,For the WebK=29.1 KN/m= 0.9730 KN/mT ? d/20[21]But qk = k x 5.0 KNlm 2T? 160/20=1.333Therefore, qk = 0.97 x 5.0 KNlm 2 = 4.85 KN/m 2Since T is a little bit small use the dimension of theii. Steel Plate for Treadsflanges for the web 80mmx2mmAssume 300mm x 2400mm sizeSection ClassificationPlate LoadingFlangesDead load from plateT=160mm; p y =225N/mm 2=25.55kg/m 2 x0.3mx2.4m+25.55kg/m 2 x0.147mx2.4mBut=27.41kgx10=274.1Nx10 -3 =0.274KN Characteristic impose load=2.4mx0.3m?"=(275/py)½[22]x4.85kN/m 2 =3.49KN Impose load on riser/tread=3.49x22=76.78KN?"=(275/225)½=1.11 b=80-2 =39Design load, n=1.4gk+1.6qk2=1.4x0.274+1.6x76.78=123.23KNT=160mmBending momentb/T=39/160=0.243BM max = WL/8[19]For welded section b/T=13?"=123.23x0.3/8 =4.62KNMb/T=13x1.11 = 14.43>0.24For short span girderTherefore, the flanges are semi compactSpan/depth=12Serviceability Deflection under Imposed LoadSpan/depth=15 2390mm/depth=15? = 050 x 384EI wl 4[23]Depth=2390mm/15=159mm?160mm Since d=160mm>150mm; take p y =225N/mm 2W = 1.0gk + 1.0qk = 13.814+38.39=52.204KNArea of flanges, Af=M/d x p y[20]Where, E=205x10 9 N/mm 2 © 2018 Global Journals * How to Build Paths, Steps and Footbridges PJeswald 2005 Storey Publishing North Adams, Massachusett * WHMosley JHBungey Reinforced concrete design England Palgrave 1999 * BS 5400 Part 2 Specification for Loads. Licensed Copy JMugu 1978 University of Bath, England * Evaluation of Pedestrian Bridges and Pedestrian Safety in Jordan AMuhammed 2013 Published by IISE * Archaeology of Dartmoor PNewman Dartmoor National Part Authority, England. Pg 27 2003 * Pm News Nigeria Moves to Decongest Lagos Traffic Accessed 2015. 18 th June, 2015 * TheGuardian On Pedestrian Bridge 2015. 2015