Indian Journal of Engineering & Materials Sciences Vol. 12, October 2005, pp. 419-426 Behaviour of the model surface strip footing on reinforced sand Berkan Moroglu a , Bayram Ali Uzuner b* & Erol Sadoglu b a Civil Engineering Department, Cumhuriyet University, 58050 Sivas, Turkey b Civil Engineering Department, Karadeniz (Black Sea) Technical University, 61080 Trabzon, Turkey Received 13 May 2004; accepted 9 May 2005 A series of tests were carried out with an eccentrically loaded model surface strip footing on un-reinforced and reinforced dense sand to investigate the behaviour of the footing (decrease in ultimate load with increasing eccentricity, failure surfaces and load displacement relations). The experimental set-up used to run the tests consists of tank, model footing, sand and loading mechanism. A single woven geotextile strip sheet was placed horizontally below the footing’s base at a depth half of the footing’s width. The primary failure surfaces occurred at the eccentricity side for this laterally unrestricted footing. The use of this reinforcement increased the ultimate load by about 50% for centrally loaded strip footing in comparison with un-reinforced case and its contribution to ultimate load decreased as eccentricity increased in these conditions. Geotextile not only increased ultimate load, but also increased necessary amount of vertical displacement of footing to reach failure compared with un-reinforced case. The experimental results are in good agreement with Meyerhof’s effective width concept than the customary analysis and the customary analysis is unsafe outside the core. IPC Code: E02D1/00 Foundations are frequently subjected to moments in addition to vertical loads in practice. Moments are brought about from lateral or horizontal loads (lateral earth pressures, earthquakes, water and wind) acting on structures. The eccentricity in a strip footing, e, can be defined as the ratio of moment (M) over vertical load (Q) (Fig. 1). There are a number of methods for calculating the ultimate load (Q u ) of the eccentrically loaded foundation. These are Meyerhof’s effective width concept 1 , the customary analysis (the traditional method, the conventional method), Prakash and Saran Theory 2 . Meyerhof 1 put forward that the ultimate load (Q ue ) of an eccentrically loaded strip foundation is equal to the ultimate load (Q uc ′) of the centrally loaded strip foundation having a reduced width B′ obtained by subtracting 2e from B (Fig. 2). Some assumptions are made in customary analysis in order to determine the normal base pressure distributions under an eccentrically loaded foundation. These are stress distribution is linear, vertical equilibrium for forces (ΣV = 0), moment equilibrium (ΣM = 0) and the contact is lost between the footing base and the soil where tensile stresses occur. Uzuner 3 investigated the base stress distribution of the eccentrically loaded model strip foundations on sand experimentally and concluded that the assumptions of the customary analysis are satisfactory. The base stress distributions of a strip footing are shown in Fig. 3. The ultimate load of eccentrically loaded strip foundation can be determined from the following condition according to __________ *For correspondence (E-mail: uzuner@ktu.edu.tr) Fig. 1—Eccentricity definition for a strip footing Fig. 2—Meyerhof’s effective width concept Fig. 3—The base normal stress distributions in customary analysis