24 / JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES / FEBRUARY 2001 DISTRESS OF RC STRUCTURE DUE TO POOR QUALITY CONTROL AND OVERLOADING By Ahmed Shlash Alawneh, 1 Abdallah I. Husein Malkawi, 2 and Osama Kh. Nusier 3 ABSTRACT: The main purpose of this paper is to make a complete investigation into the cause of distress to a four-story residential building in Irbid, Jordan, and to determine the necessary remedial measures for the observed damages. The observed damage in this case study involved crushing and splitting of concrete, along with buckling of reinforcement bars of the 24 underground reinforced concrete short columns supporting the building. Primarily, this damage occurred due to poor quality of concrete in the short underground reinforced concrete columns, combined with overloading. With the exception of the short columns, the design and con- struction of the building was considered to be adequate by a technical committee from the Jordan University of Science and Technology. The main lesson learned from this case study is that poor quality control of concrete construction will significantly influence the structural integrity of a facility. INTRODUCTION The case study under consideration is that of a four-story residential building located to the south of Yarmouk Univer- sity, Irbid, Jordan. The ground and first floors of the building were constructed in 1987, while the second and third floors were constructed in 1997. The plan area of each floor is 296 m 2 , and each floor consists of two identical apartments (Fig. 1). The building is constructed of reinforced concrete beams and columns with exterior walls composed of concrete hollow bricks (east exterior wall) or limestone panels (south, north, and west exterior walls). The interior walls of the building are composed of hollow bricks. Openings (windows and doors) are bridged by lintels, each with three 14-mm diameter rein- forcing steel bars. As shown in Fig. 1, the building is con- structed on isolated footings placed at a depth of about 2.5 m below the ground surface (Fig. 2). The footings are 1.8  1.8 m, and the effective concrete depth is 45 cm. The plan areas of footings were determined based on a presumptive allowable bearing capacity of about 250 kPa, which is a typically used value by civil engineers in the Irbid area. This presumptive allowable bearing capacity value involves, in most cases, high safety factors (usually greater than 4) against shear failure in the foundation soil. As shown in Fig. 2, the underground re- inforced concrete short columns are tied to each other by tie beams with a typical cross section of 0.3  0.5 m with six or eight 14-mm diameter reinforcing steel bars and 8-mm diam- eter stirrups at 20 cm on-center. The underground reinforced concrete short exterior columns are about 60-cm high; the in- terior ones are about 150-cm high. In September 1998, the residents of the building heard an explosion in the ground floor of the building. Ill-fitting win- dows and doors in the ground floor were indications that prob- lems had occurred in the part of the structure beneath the ground surface. Exterior excavation (made two days after the explosion) along the northern side of the building down to the foundation level indicated that structural damage to four un- derground reinforced concrete short columns along the north- 1 PhD, Asst. Prof. of Civ. Engrg., Civ. Engrg. Dept., Jordan Univ. of Sci. and Technol., P.O. Box 3030, Irbid, 21110, Jordan. E-mail:shlash@ just.edu.jo 2 PhD, Assoc. Prof. of Civ. Engrg., Civ. Engrg. Dept., Jordan Univ. of Sci. and Technol., P.O. Box 3030, Irbid, 21110, Jordan. 3 PhD, Asst. Prof. of Civ. Engrg., Civ. Engrg. Dept., Jordan Univ. of Sci. and Technol., P.O. Box 3030, Irbid, 21110, Jordan. Note. Discussion open until July 1, 2001. To extend the closing date one month, a written request must be filed with the ASCE Manager of Journals. The manuscript for this paper was submitted for review and possible publication on April 20, 1999. This paper is part of the Journal of Performance of Constructed Facilities, Vol. 15, No. 1, February, 2001. ASCE, ISSN 0887-3828/01/0001-0024–0030/$8.00 + $.50 per page. Paper No. 21963. ern side of the building had occurred (i.e., columns A-11, C-11, D-10, F-10). The damage involved crushing and split- ting of concrete, as well as buckling of reinforcing steel bars. Investigation of the type of cracks in the building revealed that the width of cracks in the building walls were, in most cases, equal to or less than 3 mm. Generally, the cracks were con- centrated in the interior and exterior walls of the ground floor. Minor cracks were also observed in the other floors of the building. The cracks observed were considered not severe in comparison to the observed damage of the short columns and this was seen as evidence that the entire building moved down- ward nearly uniformly. Uniform downward movement of the building meant that concrete in the 24 underground reinforced concrete short columns supporting the building had crushed, which was later confirmed by excavation around all exterior and interior short columns down to the foundation level. SUBSURFACE CONDITION AT THE SITE Distributed soil samples were taken from a borehole drilled at the site and basic soil properties including natural water content, w n , liquid limit, LL, plastic limit, PL, and grain-size distribution were determined. Also, undisturbed soil samples were taken and the variation of undrained cohesion, c u , un- drained friction angle,  u , and unconfined compressive strength, q u with depth were established. Table 1 summarizes the results, while Fig. 3 shows idealized soil profile at the site. The soil properties in Table 1 fall within the ranges reported by Tuncer et al. (1987) for Irbid soils. As indicated by its plasticity characteristics and grain-size distribution the soil at the site can be classified as inorganic clay of high plasticity (CH-type of soil according to the Uni- fied Soil Classification System). Also, the soil at the site can be classified as having high swelling potential. Because of a high swelling potential of the soil at the site, a 30-cm thick concrete wall 1.4-m tall was constructed around the exterior perimeter of the building (Fig. 2), to maintain nearly constant water content beneath the building in the summer, as well as in winter. Sidewalks 2-m wide were also made around the building for the same purpose. Based on the soil profile in Fig. 3 and the data shown in Table 1, the estimated allowable bearing capacity is about 325 kPa. The calculation of this estimated value is based on the general bearing equation by Hansen as presented by Bowels (1988) with a safety factor against shear failure in the sup- porting soil equal to 4. DISTRESS In general, the extent of observed distress was more severe along the northern side of the building than the southern side. Typical types of distress that took place were