Compressive Membrane Capability Estimates in Laterally Edge Restrained Reinforced Concrete One-Way Slabs
Abstract
The load capacity of laterally restrained reinforced concrete one-way slabs currently is estimated by entering the compressive membrane theory with a midspan deflection. However, the midspan deflection estimates exhibit large variability. The point of peak thrust is a more accurate index of the peak load capacity, than midspan deflection estimates and even experimentally measured midspan deflections. The calculation of the thrust within the compressive membrane theory is a maximum when the slab's axial shortening and the outward support movement are a maximum. The use of the peak thrust to select the peak capacity, when combined with a modification to Park and Gamble's (1980) compressive membrane theory, provides an improved overall correlation to the experimental data for a large range of span-to-thickness ratios (2.7 <L/h <28.3). Peak midspan deflection estimates were developed to define the peak point of the load-deflection curve. A relationship exists between the slab's axial concrete compressive strength and the peak concrete compressive strain used within a curvature and geometrically based deflection equation to predict the midspan deflection. The post-peak trough and ultimate points are related empirically to the tensile membrane curve such that the generated load-deflection curve compares extremely well with the experimental data. A simple compressive membrane load capacity estimate for laterally restrained reinforced concrete one-way slabs is developed for field use. The estimate uses the axial force-moment interaction equations and a ratio for the peak thrust to the slab's axial capacity. The resulting thrust enhanced moment capacities at the support and midspan hinge lines allow for a simple, and extremely accurate, estimate of the peak compressive membrane capacity using yield line theory.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1999
- Accession Number
- ADA363037
Entities
People
- Ronald W. Welch
- William J. Hall
- William L. Gamble
Organizations
- University of Illinois Urbana–Champaign