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A novel formulation aiming to achieve optimal design of reinforced concrete (RC) structures is presented here. Optimal sizing and reinforcing for beam and column members in multi-bay and multistory RC structures incorporates optimal stiffness correlation among all structural members and results in cost savings over typical-practice design solutions. A Nonlinear Programming algorithm searches for a minimum cost solution that satisfies ACI 2005 code requirements for axial and flexural loads. Material and labor costs for forming and placing concrete and steel are incorporated as a function of member size using RS Means 2005 cost data. Successful implementation demonstrates the abilities and performance of MATLAB's (The Mathworks, Inc.) Sequential Quadratic Programming algorithm for the design optimization of RC structures. A number of examples are presented that demonstrate the ability of this formulation to achieve optimal designs.

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This paper is accompanied by a study on constitutive modelling issues of cemented sands. The concentration here is on experimental issues related to the triaxial testing of cemented sands. A preliminary investigation is performed aiming to identify potential effects of specimen size and slenderness on the stress–strain–strength characteristics of cemented sands. A comprehensive experimental study follows where clean sand specimens, as well as specimens with 2, 4 and 6 per cent cement content, are tested. The aim of the study is to examine the effects of cement content and confinement on the shear strength, stiffness, softening and dilation characteristics of cemented sand. © 1997 John Wiley & Sons, Ltd.

Int. j . numer. anal. methods geomech. 12, 45-60 (1988)) This paper has addressed a very significant problem in geotechnical engineering, namely the analysis of the cone penetration test. As the authors note, this is a very difficult problem to solve, even numerically, since it involves large deformations, moving boundaries and non-linear material behaviour.The authors have used an axi-symmetric finite element analysis and presented numerical results for the displacement, stress and pore water pressure fields around the cone tip at failure for penetration under undrained conditions. Failure is defined as the condition where penetration proceeds indefinitely at a constant cone pressure. Results are also given for the relationships between penetration resistance and penetration depth.In the analysis reported in the paper it was assumed that the initial effective stress state in the soil was hydrostatic with a magnitude of pb = 100 kPa (where compression is considered positive). The stress-strain behaviour of the material was formulated in terms of effective stress and the elasto-plastic soil model included a work hardening yield cap and a fixed yield surface. The model parameters were selected so that the initial undrained shear strength of the soil under triaxial test conditions, c, , was approximately 50 kPa.Furthermore, the elastic behaviour of the soil skeleton was defined by Young's modulus E = 30,000 kPa and Poisson's ratio, v=O.28. Thus the elastic shear modulus G = E/2( 1 + v) can be computed simply as G = 11,719 kPa. The choice of soil model and initial stress state implies that the soil will work harden prior to reaching the shear failure surface.For the ideal case presented in the paper the authors have computed an ultimate cone pressure, qc = 525 kPa. it is interesting to compare this value of ultimate cone resistance with the limit pressure predicted by the theory for spherical cavity expansion. For the cavity expansion problem, the writers have adopted a total stress approach and assumed a simple-elastic-perfectly-plastic soil model with deformations proceeding under constant volume (undrained) conditions. The elastic behaviour of the ideal material is characterized by an elastic shear modulus G = 11,719 kPa and an undrained shear strength, c, = 50 kPa. This material will yield plastically whenever the following criterion is satisfied 6, -6 3 = 2c, (1) where u1 and o3 are major and minor principal total stress components, respectively.The solution for the limit pressure, at which indefinite spherical cavity expansion occurs in this type of material, has been given in closed form by Bishop et al. The expression for the limit pressure pL can be written:where po is the initial hydrostatic total stress in the material. It would appear that in the cone penetration problem solved by the authors, the ambient (initial) pore water pressure was set to zero, so that the total and effective stress components are identical, in which case po = po = 100 kPa. Substitution of the appropriate values of po, G and ...