Mark Adom-Asamoah

Generation of analytical fragility curves for Ghanaian non-ductile reinforced concrete frame buildings

This study is on seismic safety evaluation of non-ductile reinforced concrete (RC) frame buildings in Ghana. Generic 3-, 4- and 6-storey non-ductile RC buildings were characterised for assessment. The generic buildings were designed according to British Standard (BS) 8110. The fragility curve parameters were generated using inelastic time history analyses for seismic demand and inelastic pushover analyses for structural capacity of the buildings. As a result of lack of real time histories in Ghana, 3 suites of 100 synthetic time history records each were generated in order to generate lower and upper bounds for inelastic dynamic response. Parameters of collapse fragility curves with 50% probability of exceedance were established for the generic non-ductile Ghanaian frame buildings using short duration near-fault like records. All the curves represent the probability of exceeding the collapse limit state as a function of the peak ground acceleration (PGA) and spectral acceleration at the fundamental mode period of the generic buildings. Using the data from the nonlinear dynamic analysis of the generic buildings under all 300 synthetic time histories, a pair of three sets of fragility curves was developed. Results obtained showed that the generic non-ductile 3 to 6 storey RC frame buildings subjected to near-fault like ground motions may record high probabilities of collapse, if they are situated in 0.25 to 0.35 g PGA seismic zones.

Thermal effect of mass concrete structures in the tropics: Experimental, modelling and parametric studies

Abstract This paper is an experimental investigation and analytical simulation of thermal effects on mass concrete structures in the tropics. A study of the temperature rise of a 1.1 m × 1.1 m × 1.1 m experimental mass concrete block, well instrumented with thermocouples to monitor the temperatures distribution was performed. A validated finite element model was used to predict the temperature development of the hydrating experimental mass concrete block. Thermal stress analysis was performed to give an estimate of stresses induced by the thermal gradient of the concrete block section and the crack index was used to quantify the probability of thermal cracking. A parametric study on the effect of the surface area to volume ratio (SVR) of mass concrete was performed to quantify the maximum allowable thermal gradient as well as the induced thermal stresses that may cause thermal cracks. For SVR less than 0.36, thermal cracks may occur at early ages of concrete strength development in the tropics.