Mohd Saleh Jaafar

Optimization of Earthquake Energy Dissipation System by Genetic Algorithm

Numerous recent studies have assessed the stability and safety of structures furnished with different types of structural control systems, such as viscous dampers. A challenging issue in this field is the optimization of structural control systems to protect structures against severe earthquake excitation. As the safety of a structure depends on many factors, including the failure of structural members and movement of each structural node in any direction, the optimization technique must consider many parameters simultaneously. However, the available literature on optimizing earthquake energy dissipation systems shows that most researchers have considered optimization processes using just one or a few parameters applicable only to simple SDOF or MDOF systems. This article reports on the development of a multiobjective optimization procedure for structural passive control systems based on genetic algorithm; this research focused on systems that would minimize the effects of earthquake based on realistic structural responses considering plastic hinge occurrence in structural elements and three-directional displacement in all structural nodes. The model was applied to an example of three-dimensional reinforced concrete framed building and its structural seismic responses were investigated. The results showed that the optimized control system effectively reduced the seismic response of structures, thus enhancing building safety during earthquake excitations.

Construction performance comparison between conventional and industrialised building systems in Malaysia

Purpose – Labour usage represents one of the critical elements in the Malaysia construction industry due to severe shortage of local workers. This paper aims to present a construction performance comparison between conventional building systems and industrialised building systems (IBS).Design/methodology/approach – Data were obtained from 100 residential projects through a questionnaire survey in 2005. A total of 100 respondents participated in this study.Findings – Analysis of variance (ANOVA) results indicated that the actual labour productivity comparison between conventional building system and IBS was significantly different. Further, the comparison of crew size indicated that the conventional building system of 22 workers was significantly different from the IBS of 18 workers. Similarly, the cycle time of 17 days per house for conventional building system was found to be significantly different from the IBS of four days. However, the conventional building system was found to be insignificantly diffe...

Development of finite element computer code for thermal analysis of roller compacted concrete dams

Thermal analysis of roller compacted concrete (RCC) dams plays an important role in their design and construction. This paper deals with the development of a finite element based computer code for the determination of temperatures within the dam body. The finite element code is then applied to the real full-scale problem to determine the impact of the placement schedule on the thermal response of roller compacted concrete dam. Based on the results obtained, it could be concluded that for a given roller compacted concrete dam, changing the placing schedule can optimize the locations of maximum temperature zones.

Constructability implementation: a survey in the Malaysian construction industry

Twenty-three constructability concepts are identified. Based on these, an industry-wide questionnaire was administrated in Peninsular Malaysia. The respondents were the engineers working with owners, consultants, contractors, subcontractors and construction management firms. The importance, from the viewpoint of the Malaysian engineers, of the constructability concepts and the degree of the actual application of those concepts in the Malaysian Construction Industry is presented so that an insight on constructability implementation can be established. Fieldwork results revealed that the Malaysian engineers showed high acceptance of 22 concepts and rejected the one that relates to the fast-track method of construction. Those engineers accepted the constructability concepts from the theoretical point of view but generally they did not apply these concepts in their practices. The study also concludes that the Malaysian engineers show a wide understanding of the majority of the concepts. However, they did not link those concepts under the umbrella of constructability.

Influence of torsion on the inelastic response of three-dimensional r.c. frames

A three-dimensional reinforced concrete framed building was modelled using finite element method. Two types of elements, the beam-column element and flat shell element were used for modelling the frame and floor slabs, respectively. A computer program has been developed for the analysis of 3D framed building by integrating the finite element and stiffness method. The lumped inelasticity model with three-dimensional point hinges at the ends of the beam-column element was implemented. A yield surface for a reinforced section of the member subjected to simultaneous actions of biaxial bending, torsion and axial forces was evolved. The developed yield surface integrated with the theory of plasticity was used to develop a suitable procedure for inelastic analysis of three-dimensional problems with the floor slab assumed to remain elastic throughout the analysis. The inelastic procedure is able to predict the sequential formation of plastic hinges in the frame members and the continuous deterioration of the stiffness of the frame. A single storey one bay reinforced concrete space frame was analysed for twist loading to study the inelastic response of the reinforced concrete frame. The results indicate that, the consideration of torsion in defining the yielding surface plays a significant role in the inelastic behaviour and estimation of failure load for reinforced concrete frames under torsional loading.

Analytical Model for Viscous Wall Dampers

By now, many civil engineering researchers have extensively studied the application of earthquake energy dissipation systems in seismic-resistant buildings. Earthquake energy dissipation systems play an important role in enhancing the sustainability of structures against seismic excitation. Frame buildings are strengthened by installing damper devices as supplemental structural members. This article presents the finite-element-based development of an analytical model for a viscous wall damper VWD device, an alternative to other earthquake energy dissipation systems, which can diminish the effect of earthquakes on structures and improve the seismic performance of multistory buildings subjected to ground motion. The constitutive law of VWDs has been formulated and integrated to develop a finite element model of VWD compatible with the reinforced concrete RC structure analytical model. Then, the finite element algorithm has been developed for inelastic analysis of RC buildings equipped with VWD devices capable of detecting damage to both structural members and damper connections under dynamic loading. Based on the developed system, the special finite element program was codified and verified by applying it to a real model of a RC building with supplementary VWD devices. Influence of VWDs on seismic performance of the RC building during earthquake excitation was evaluated. The proposed analytical model for VWD is verified by using experimental test data and analysis result proved that this energy dissipation system succeeds by substantially diminishing and dissipating a structures induced seismic responses. Also the parametric study indicated that the damping coefficient is very effective on performance of VWD.

Evaluation of the role of the contractor’s personnel in enhancing the project constructability

Contractors’ personnel play a prominent role in enhancing the constructability of facilities design, construction and assessment. Looks at the constructability concepts identified by the Construction Industry Institute at Austin, Texas (CII) and represents and describes the constructability concepts in relation to contractors’ personnel. Discusses the role of each of them in enhancing constructability of facilities projects. Concludes that a set of obligations are the answer to the question of “How can the contractor’s personnel enhance the project constructability?”.

Effect of Soft Story on Structural Response of High Rise Buildings

Severe structural damage suffered by several modern buildings during recent earthquakes illustrates the importance of avoiding sudden changes in lateral stiffness and strength. Recent earthquakes that occurred have shown that a large number of existing reinforced concrete buildings are vulnerable to damage or even collapse during a strong earthquake. While damage and collapse due to soft story are most often observed in buildings, they can also be developed in other types of structures. The lower level containing the concrete columns behaved as a soft story in that the columns were unable to provide adequate shear resistance during the earthquake. Usually the most economical way of retrofitting such as a building is by adding proper bracing to soft stories. So, in this paper occurring of soft at the lower level of high rise buildings subjected to earthquake has been studied. Also has been tired to investigate on adding of bracing in various arrangements to structure in order to reduce soft story effect on seismic response of building. It is lead to assess the vulnerability level of existing multi-storied buildings so that they can be retrofitted to possess the minimum requirements. This will help in minimizing the impending damages and catastrophes.

Review of available approaches for ultimate bearing capacity of two-layered soils

Abstract This paper presents the state of the art report on available approaches to predicting the ultimate bearing capacity of two-layered soils. The article discusses three most popular methods, including the classical method, application of the finite element method and artificial neural network. Various approaches based on these three powerful tools are studied and their methodologies are discussed.

UPV method for strength detection of high performance concrete

Purpose – This paper aims to present a research finding that establishes a regression model between ultrasonic pulse velocity (UPV) tests and actual strength of high performance concrete (HPC).Design/methodology/approach – In this study, a total of 270 cube samples were made from six different mix proportions. The mixes were grouped in two series that consist of nominal maximum aggregate sizes of 10 mm (A10) and 19 mm (A19). Silica fume were used as mineral admixtures at 5 percent, 10 percent and 15 percent of cement in both series. UPV tests were conducted for each of the specimens, followed by destructive strength tests. The tests were carried out for concrete at different ages of between three to 56 days. The destructive test results were used as the true strength of the mixes and the UPV test results were used as strength estimation.Findings – Concrete strength correlations between UPV and destructive tests were analysed for each mix proportions and in each series. These correlations are presented in ...