Thermo-Mechanical Modeling of High-Strength Concrete Column Subjected to Moderate Case Heating Scenario in a Fire

This paper presents a numerically developed computer model to simulatethe thermal behavior and evaluate the mechanical performance of a fixedend loaded loaded High Strength Concrete Column (HSCC), subjectedto Moderate Case Heating Scenario (MCHS), in a hydrocarbon fire. Thetemperature distribution within the mid-height cross-sectional area of thecolumn was obtained to determine the thermal and mechanical responsesas a function of temperature. The governing two-dimensional transient heattransfer partial differential equation (PDE), was converted into a set of ordinary algebraic equations, subsequently, integrated numerically by usingthe explicit finite difference method, (FDM). A computer program, VisualBasic for Applications (VBA), was then developed to solve the set of ordinary algebraic equations by implementing the boundary as well as initialconditions. The predictions of the model were validated against experimental data from previous studies. The general behavior of the model as wellas the effect of the key model parameters were investigated at length in thereview. Finally, the reduction in the column’s compression strength and themodulus of elasticity was estimated using correlations from existing literature. And the HSCC failure load under fire conditions was predicted usingthe Rankine formula. The results showed that the model predictions of thetemperature distribution within the concrete column are in good agreementwith the experimental data. Furthermore, the increase in temperature ofthe reinforced concrete column, (RCC), due to fire resulted in a significantreduction in the column compression strength and considerably acceleratesthe column fire failure load

Seismic Collapse Prevention of Non-Structural Infill Masonry Using eq-top: an Easy Earthquake Fibre Retrofitting System

Specially manufactured technical textile and polyurethane glue, called eq-top system is proposed to save life and prevent collapse of non-structural masonry, e.g. in filled walls during a seismic event with a minimum cost. The idea is to attach glass fiber textile on the brittle brick partition walls in the buildings and connect them with the peripheral structural frames. During an earthquake it is expected that the system will hold the non-structural elements in place and prevent their out of plan failures; also it will improve their in-plane stiffness making them working as structural infill walls. The proposed technical textile is light-weight, easy to handle, fast in application, and cheap compared to the well-known FRP and CRP. To test the eq-top system, shake table on full scale brick wall specimens was conducted at Bogazi double dagger i University in Turkey. The strengthened specimen and the non-strengthened specimens were fixed on the same shake table for a direct comparison and the amplitudes of base accelerations were increased until severe damage is reached in the non-strengthened and/or strengthened specimen. The seismic performance of the 2 x 2 specimens (two without and two with strengthening) was compared in terms of stiffness, strength, deformability and ductility. All thought that the specimens were excited under their resonance frequencies, no damage at all occurred in the strengthened specimen and total collapse happened already in the non-strengthened panel under low amplitudes. The results have confirmed effectiveness of the proposed retrofit scheme

Cyclic lateral load behavior of CFS walls sheathed with different materials

In recent years, cold formed steel (CFS) buildings have been recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight, fast to construct, recyclable, dimensionally stable, and do not need formworks. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as earthquake loads efficient design is needed. In this paper the effects of sheathing material type on the cyclic lateral load behavior of CFS walls were investigated. Ten full scale CFS wall specimens sheathed with four different material types were tested under lateral cyclic loads. The sheathing types are Trapezoidal steel sheet, steel sheet, reinforced cement board, and thin ribbed steel sheet shotcreted with cement mortar. The effect of wall foundation connection details on the lateral load response of the walls were also investigated. Test results indicate that the lateral load carrying capacities of the walls increased by about 3 times when sheathed with the proposed materials. Furthermore specimens sheathed with steel sheets have almost the same lateral load carrying capacities of specimens sheathed with Trapezoidal steel sheets. However the hysteresis damping is higher in the steel sheet sheathed specimens. That means corrugating the steel sheets as Trapezoidal will not increase the strength and damping characteristics of the walls. Walls sheathed with 12 mm thick reinforced cement boards show 1.5 times higher lateral load carrying capacity than all the tested specimens. Depending on the material sheathing type and the sheathing thickness the specimens fail due to local failure in the edge studs, or screw tears out or buckling of the steel sheet. Lastly CFS wall lateral permanent deformations can be reduced by improving the wall-foundation connection details. (c) 2015 Elsevier Ltd. All rights reserved

Low-Rise 3D Panel Structures for Hot Regions: Design Guidelines and Case Studies

More than 40 years ago, lightweight composite panels fabricated from polystyrene, steel, and shotcrete concrete were used to construct nonload-bearing walls such as partition walls and fa double dagger ade cladding. Recently, many private companies all over the world have started manufacturing these panels commercially to be used as load-bearing walls or floor slabs in the construction of low-rise structures up to three stories high by proposing a new building system called a 3D panel building system. The light weight of these panels, along with the fact that they are easy to handle, enhance the speed of construction, offer good heat insulation properties, and they cost less by avoiding the need for either formwork or skilled workers, make it an acceptable construction practice. Tests reported in the literature indicate that the degree of heat insulation of a 3D panel wall significantly exceeds that of partitions or curtain walls obtained with the traditional systems. This produces energy savings equal to 40% with both heating and cooling, making these panels suitable for construction in hot regions and especially in rural areas. In the literature, there are several reports of experimental works conducted by the author and by many researchers worldwide in an effort to determine the mechanical properties of the panels and to investigate the efficiency of its building system in terms of resistance to gravity and seismic loads. However, there is not enough information on their design rules. In this paper, some design guidelines are proposed. The guidelines rely on experimental findings and on reinforced concrete (RC) design building codes such as ACI-318 [Building Code Requirements for Reinforced Concrete (ACI 318-95), American Concrete Institute] and UBC. Two design case studies in Turkey using the proposed guidelines are presented. The first case is the design of a small 3D panel house and the second case is the design of a 3D panel factory. The proposed design rules are conservative and follow the rules specified for designing reinforced concrete structures with some modifications

Load carrying capacity enhancement of cold formed steel walls using shotcreted steel sheets

Recently worldwide cold formed steel buildings are recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight (easy to handle), fast constructed, energy efficient (green houses), economical, dimensionally stable and they do not need skilled worker. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as wind and earthquake loads efficiently design is needed. In this paper a new sheathing technique uses shotcreted ribbed steel sheets is proposed to improve the stability and increase the lateral load carrying capacities of the CFS walls in order to withstand earthquake and wind loads safely. The idea is to sheath the outer side of CFS structure external walls with thin ribbed steel sheets, then shotcreted the sheets with cement or gypsum mortars. To test the concept full size wall specimens were prepared in the laboratory and tested under monotonic vertical and lateral loads. Some of the specimens were sheathed with the traditional fiber cement boards or gypsum boards with mat reinforcement, while the others were sheathed with the proposed technique. Test results indicates that the lateral load carrying capacities of the walls sheathed with the proposed technique increases by about two times compared with the walls sheathed with traditional boards. And under ultimate loads they fail in local failure modes rather than overall buckling failure modes which commonly occur in the walls sheathed with traditional boards. (C) 2012 Elsevier Ltd. All rights reserved

Comparison of neural networks and neuro-fuzzy computing techniques for prediction of peak breach outflow

Accurate prediction of peak outflows from breached embankment dams is a key parameter in dam risk assessment. In this study, efficient models were developed to predict peak breach outflows utilizing artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS). Historical data from 93 embankment dam failures were used to train and evaluate the applicability of these models. Two scenarios were applied with each model by either considering the whole data set without classification or classifying the set into small dams (48 dams) and large dams (45 dams). In this way, nine models were developed and their results were compared to each other and to the results of the best available regression equations and recent gene expression programming. Among the different models, the ANFIS model of the first scenario exhibited better performance based on its higher efficiency (E = 0.98), higher coefficient of determination (R-2 = 0.98) and lower mean absolute error (MAE = 840.9). Moreover, models based on classified data enhanced the prediction of peak outflows particularly for small dams. Finally, this study indicated the potential of the developed ANFIS and ANN models to be used as predictive tools of peak outflow rates of embankment dams