Abstract: Underground space is becoming a necessity nowadays, especially in highly congested urban areas. Retaining underground excavations using shoring systems is essential in order to protect adjoining structures from potential damage or collapse. Reinforced Concrete Piles (RCP) supported by multiple rows of tie-back anchors are commonly used type of shoring systems in deep excavations. However, executing anchors can sometimes be challenging because they might illegally trespass neighboring properties or get obstructed by infrastructure and other underground facilities. A technique is proposed in this paper, and it involves the addition of eccentric high-strength steel strands to the RCP section through ducts without providing the pile with lateral supports. The strands are then vertically stressed externally on the pile cap using a hydraulic jack, creating a compressive strengthening force in the concrete section. An experimental study about the behavior of the shoring wall by pre-stressed piles is presented during the execution of an open excavation in an urban area (Beirut city) followed by numerical analysis using finite element software. Based on the experimental results, this technique is proven to be cost-effective and provides flexible and sustainable construction of shoring works.
Abstract: For fire safety purposes, the fire resistance and the
structural behavior of reinforced concrete members are assessed to
satisfy specific fire performance criteria. The available prescribed
provisions are based on standard fire load. Under various fire
scenarios, engineers are in need of both heat transfer analysis and
structural analysis. For heat transfer analysis, the study proposed a
modified finite difference method to evaluate the temperature profile
within a cross section. The research conducted is limited to concrete
sections exposed to a fire on their one side. The method is based on
the energy conservation principle and a pre-determined power
function of the temperature profile. The power value of 2.7 is found
to be a suitable value for concrete sections. The temperature profiles
of the proposed method are only slightly deviate from those of the
experiment, the FEM and the FDM for various fire loads such as
ASTM E 119, ASTM 1529, BS EN 1991-1-2 and 550 oC. The
proposed method is useful to avoid incontinence of the large matrix
system of the typical finite difference method to solve the
temperature profile. Furthermore, design engineers can simply apply
the proposed method in regular spreadsheet software.