Repair of Decayed Heavy Timber Roof Truss Columns at 135 Year Old Cathedral

2014 ◽  
Author(s):  
Richard J. Kristie ◽  
Kevin A. Kalata ◽  
Heidi L. Mase
Keyword(s):  
Roof Truss

scholarly journals RESTORATION OF PREVIOUS ROOF TRUSS IN MAIN HALL OF SAIMYOUJI TEMPLE

2013 ◽  
Vol 19 (43) ◽  
pp. 1205-1208
Author(s):  
Naoki OOUE ◽  
Naoki TANI
Keyword(s):  
Roof Truss

scholarly journals A ROOF TRUSS FOR THE LABORATORY

1917 ◽  
Vol 17 (9) ◽  
pp. 824-825
Author(s):  
George E. Thompson
Keyword(s):  
Roof Truss

Design optimisation for cold-formed steel residential roof truss using genetic algorithm

2018 ◽  
Vol 15 (5) ◽  
pp. 575-583
Author(s):  
Ka Yee Kok ◽  
Hieng Ho Lau ◽  
Thanh Duoc Phan ◽  
TIina Chui Huon Ting
Keyword(s):  
Genetic Algorithm ◽  
Industrial Application ◽  
Steel Structures ◽  
Single Type ◽  
Efficient Design ◽  
Design Optimisation ◽  
Content Type ◽  
Roof Truss ◽  
Cold Formed Steel ◽  
Multi Level

Purpose This paper aims to present the design optimisation using genetic algorithm (GA) to achieve the highest strength to weight (S/W) ratio, for cold-formed steel residential roof truss. Design/methodology/approach The GA developed in this research simultaneously optimises roof pitch, truss configurations, joint coordinates and applied loading of typical dual-pitched symmetrical residential roof truss. The residential roof truss was considered with incremental uniform distributed loading, in both gravitational and uplift directions. The structural analyses of trusses were executed in this GA using finite element toolbox. The ultimate strength and serviceability of trusses were checked through the design formulation implemented in GA, according to the Australian standard, AS/NZS 4600 Cold-formed Steel Structures. Findings An optimum double-Fink roof truss which possess highest S/W ratio using GA was determined, with optimum roof pitch of 15°. The optimised roof truss is suitable for industrial application with its higher S/W ratio and cost-effectiveness. The combined methodology of multi-level optimisation and simultaneous optimisation developed in this research could determine optimum roof truss with consistent S/W ratio, although with huge GA search space. Research limitations/implications The sizing of roof truss member is not optimised in this paper. Only single type of cold-formed steel section is used throughout the whole optimisation. The design of truss connection is not considered in this paper. The corresponding connection costs are not included in the proposed optimisation. Practical implications The optimum roof truss presented in this paper is suitable for industrial application with higher S/W ratio and lower cost, in either gravitational or uplift loading configurations. Originality/value This research demonstrates the approaches in combining multi-level optimisation and simultaneous optimisation to handle large number of variables and hence executed an efficient design optimisation. The GA designed in this research determines the optimum residential roof truss with highest S/W ratio, instead of lightest truss weight in previous studies.

Roof truss systems under blast loads

2017 ◽  
Author(s):  
◽  
Doaa Bondok
Keyword(s):  
Finite Element ◽  
Blast Wave ◽  
Numerical Models ◽  
Blast Resistance ◽  
Experimental Results ◽  
Blast Loads ◽  
Damage Level ◽  
Dynamic Analyses ◽  
Roof Truss ◽  
Static Resistance

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Designing roof systems for blast loading is quite complex. Many uncertainties still exist in this vital research area. The typical single degree of freedom dynamic modeling approach that is used widely by the blast design community is based on idealization of the structural components. Limited information exists on the blast response of different roof systems and their blast design methodology is lacking. Moreover, the blast roof load is based on approximate methods to produce a blast wave equivalent to the actual propagated wave. This approximation needs to be evaluated to ensure the blast designs are sufficient. The uncertainty of blast loads and roof resistance can lead to either excessive costs or insufficient blast designs. Therefore, the research presented here aims to bridge the gap in the knowledge about the blast resistance of different roof systems; Open Web Steel Joist (OWSJ) systems and Cold-Formed Steel (CFS) roof systems as well as to assess the accuracy of the existing ASCE and UFC approximate roof blast loads. In this dissertation, dynamic analyses using the finite element method were performed on a roof component to compare the dynamic responses resulting from a propagated blast wave and the current equivalent blast load techniques. Blast field data were used to verify the dynamic finite element model. Results have shown that current methodologies should be corrected if used to design for blast loading. Previous experiments were used to verify advanced finite element models developed to predict the complete static resistance of OWSJs including the failure limits. The verified models were used to perform dynamic analyses to predict the system dynamic response under equivalent blast loads. Analyses and energy comparisons at superficial damage level showed that the current methodology, used to calculate OWSJ static resistance, predicted 27% and 88% higher energies than the experimental ones for 16K5 and 26K5 joists, respectively. While at moderate damage levels current methodology predicted 47% and 108% higher energies than the experimental ones for 16K5 and 26K5 joists. Evaluating the blast resistance of CFS roof systems is challenging. There is a lack of existing design guidelines and response criteria for CFS roof systems. The UFC manual provides information that is relevant to CFS panels only. The approach that was adopted in this dissertation started with an extensive testing program of different types of end connections used for CFS roof trusses to investigate their failure capacities in horizontal and vertical directions. Analyses of the experimental results showed that using Hilti PAFs are more favorable than using bolts for supporting CFS truss end-connections as it was indicated in their strength and toughness. Moreover, the experimental results were used to verify the deformable screw behavior and the finite element model developed to predict the progressive failure of the truss end-connections. Small-scale CFS roof truss specimens were tested to failure under quasi-static loading. The static resistance of these systems and the associated failure mechanisms were identified. Experimental results and energy comparisons show that the truss layout and the shape of loading significantly affect the performance of the truss and the failure mechanism. Three-dimensional numerical models were developed and verified against the experimental results. The advanced models predicted the static resistance to failure with a high level of accuracy. Numerical analyses were performed to enhance the static resistance of CFS roof systems for blast analysis. Experimental and numerical analyses have shown that the energy absorbed is improved significantly when the web members susceptible to buckling are strengthened. In addition, the numerical models were used to perform dynamic analyses on a flat CFS roof system subjected to different threat levels. Von Mises stress distributions were used to investigate and determine the damage level corresponding to each threat level. The research presented in this dissertation focused on investigating the equivalent roof blast load as well as the blast resistance of different roof truss systems. The static resistance required for SDOF analysis was evaluated and identified using physical experiments and verified advanced finite element models. Failure capacities of truss end-connections were identified to improve truss system performance against blast. Based on experimental and numerical analyses, recommendations are given to arrive at an enhanced blast resistance. Dynamic analyses on 3D truss numerical models were used to investigate the damage level under certain threats. It is recommended for future work to perform field tests to address the critical differences between the measured field roof wave and the UFC manual roof blast wave. The developed numerical models can be potentially used as an analysis tool to investigate the resistance of other truss profiles and to examine the failure mechanisms that may lead to the development of an analytical model for the static resistance of roof systems. It is recommended for future work to compare the dynamic analyses performed using the developed numerical models and the SDOF dynamic analysis to provide more insight into the idealization of this technique.

scholarly journals Experimental Study on the Effect of Heel Plate Length on the Structural Integrity of Cold-formed Steel Roof Trusses

2018 ◽  
Vol 65 ◽  
pp. 08010
Author(s):  
Je Chenn Gan ◽  
Jee Hock Lim ◽  
Siong Kang Lim ◽  
Horng Sheng Lin
Keyword(s):  
Ultimate Load ◽  
Structural Integrity ◽  
Load Capacity ◽  
Local Buckling ◽  
Ultimate Capacity ◽  
Ultimate Load Capacity ◽  
Plate Length ◽  
Roof Truss ◽  
Cold Formed Steel ◽  
Structural Failures

Applications of Cold-Formed Steel (CFS) are widely used in buildings, machinery and etc. Many researchers began the research of CFS as a roof truss system. It is required to increase the knowledge of the configurations of CFS roof trusses due to the uncertainty of the structural failures regarding the materials and rigidity of joints. The objective of this research is to investigate the effect of heel plate length to the ultimate load capacity of CFS roof truss system. Three different lengths of heel plate specimens were fabricated and subjected to concentrated loads until failure. The highest ultimate capacity for the experiment was 30 kN. The results showed that the increment of the length of the heel plate had slightly increased the ultimate capacity and strain. The increment of the length of the heel plate had increased the deflection of the bottom chords but decreased the deflection of the top chords. Local buckling of top chords adjacent to the heel plate was the primary failure mode for all the heel plate specimens.

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