Study of Two-way Reinforced Concrete Slab using Coefficient Methods and Model Methods

Analysis of two-way slabs has been developed over the past years and many methods and theories exist in structural design codes. Most of these methods are approximate including Rankine-Grashoff, Marcus, ACI 318-63 code and EC 2 code, since these methods are widely used due to their simplicity.

The main idea in this research is to study these approximate methods and compare the values of load distribution factors based on bending moment results with corresponding values using more accurate analysis from, a finite element software using (ETABS 2019).

To understand the conditions at which these methods may be applied, and the effect of boundary beams stiffness on load distribution factors in both directions, this research uses two solid slab models for analysis, the first is simply supported and second is one short edge continuous with variable boundary beam stiffness.

The results show that as the aspect ratio increases, the load distribution factor in short direction 𝛼 increases, while the load distribution factors in long direction 𝛽 +𝑣𝑒 and 𝛽−𝑣𝑒 decrease, but the rate of increase or decrease depends on perimeter beams stiffness.

As short beam stiffness𝛼𝑓,𝑠ℎ𝑜𝑟𝑡 increases, 𝛼 values decrease for the same aspect ratio, while 𝛽+𝑣𝑒values slightly increase, and as long beam stiffness 𝛼𝑓,𝑙𝑜𝑛𝑔 increases, 𝛽+𝑣𝑒 values decrease substantially.

Both𝛼𝑓,𝑠ℎ𝑜𝑟𝑡 and 𝛼𝑓,𝑙𝑜𝑛𝑔 have a substantial impact on 𝛽−𝑣𝑒 values, where increasing 𝛼𝑓,𝑠ℎ𝑜𝑟𝑡 leads to increasing in 𝛽−𝑣𝑒 values, and increasing of𝛼𝑓,𝑙𝑜𝑛𝑔leads to decreasing in 𝛽

−𝑣𝑒 values.