Civil Engineering Dimension (E-Journal)
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Seismic Assessment of Structures in Regions of Low to Moderate Seismicity
Get PDFAssessment of structures according to conventional seismic design procedure has been based on trading off strength and ductility (or displacement) to provide sufficient energy dissipation capacity to structures. Consequently, structures in regions of high seismicity are designed to undergo large displacements whilst maintaining their lateral strengths in an earthquake. Energy demand from a small to medium earthquake could subside with increasing effective natural periods. Significantly, the amount of drift imposed on the structures could be restrained to an upper limit irrespective of the degradation in strength or stiffness of the lateral load resisting elements. Based on the displacement-controlled behaviour, structures can be deemed seismically safe despite having undergone significant degradation in strength and stiffness, provided that the structures can sustain the maximum drift demand from an earthquake without collapsing. This paper proposes a simple procedure for the assessment of structures in regions of low to moderate seismicity. The proposed procedure will result in significant savings in time and costs particularly when a large number of structures are to be assessed for their potential vulnerability in an earthquake
Use of Recycled Concrete Aggregate in Controlled Low-Strength Material (CLSM)
Get PDFUse of recycled concrete aggregate (RCA) is getting importance as it minimizes the use of fresh materials and eliminates waste disposal. One of the uses of RCA is as aggregate in Controlled Low Strength Material (CLSM). This paper reports the results of the investigation done on the use of RCA in CLSM. Various mixtures of CLSM were made using RCA, fly ash, and cement. Tests for workability, bleeding, density, strength, water absorption, sorption, and ultrasonic pulse velocity (UPV) were conducted. Results show that the compressive strength ranged from 1.71 MPa to 4.92 MPa, fresh density from 1879 kg/m3 to 1998 kg/m3. The strength of CLSM increases with the increase in fly ash; water absorption and bleeding decrease with increase in fly ash. It is concluded that the RCA has potential to be used in CLSM and the addition of fly ash enhances the performance
Ductility of a 60-Story Shearwall Frame-Belt Truss (Virtual Outrigger) Building
Get PDFResearches have been conducted to study Shearwall-frame combined with belt truss as structural system (SFBT), in which the post-elastic behavior and ductility of this structural system are explored. A 60-story SFBT building, with a ductility set equal to 3.75 (value for fully ductile cantilever wall) is considered. The Elastic Response Spectrum used for design is taken from Zone 2 of Indonesian Seismic Map. Capacity design method according to Indonesian Concrete Code is employed. The seismic performance is analyzed using static non-linear push-over analysis and dynamic non-linear time-history analysis. Spectrum consistent ground motions of the May 18, 1940 El-Centro earthquake N-S components scaled to maximum accelerations of various return periods (50, 200, and 500 years) are used for analysis. The results of this study show that plastic hinges mainly developed in beams above the truss, columns below the truss, and bottom levels of the wall. The building shows no indication of structural instability
Queuing Rule of Thumb based on M/M/s Queuing Theory with Applications in Construction Management
Get PDFThe current trend of queuing theory development is toward more precision which requires higher mathematical manipulation. In this paper, we attempted to reverve the current trend toward simplification of queuing formulas such that it can be used in more practical purposes, especially in construction industry. Through numerical examples of two case studies on concreting and earth moving, how to model the construction activities as queuing systems is illustrated systematically. Through the numerical examples, it is shown that when the customer cost is much lower than the server cost, queuing system can be simplified only to incorporate the constraint equation. The queueing constraint equation is suggested to be used as queuing rule of thumb. The proposed rule of thumb is rather conservative in term of queuing performance compared to the standard stochastic queuing formula because it is assumed that all the customers arrive at once in the beginning of the service
Towards Rational Design Method for Strengthening of Concrete Structures by External Bonding
Get PDFMany infrastructures need to be repaired or strengthened due to various reasons, such as unexpected deterioration and changes in performance requirement. This paper presents the following recent achievements by the authors’ group on design method for flexural strengthening of concrete structures by external bonding; (i) fracture characteristics of interface between substrate concrete and cementitious overlay, (ii) crack spacing of flexural strengthened beams, which affects debonding strength, (iii) strengths of intermediate crack (IC) debonding and end peeling, (iv) strength of concrete cover separation, and (v) effectiveness of strengthening by external bonding. A unified approach for flexural strengthening by steel plate, fiber reinforced polymer lami¬nate and cementitious overlay, for both intermediate crack (IC) debonding, including end peeling, and concrete cover separation is pre¬sented with consideration of crack spacing in the streng¬thened members. Appropriate interfacial rough¬¬¬ness to achieve efficient interface bond property is clari¬fied and the concept of effectiveness of strengthen¬ing is proposed for better strengthening design
The Stability Analysis of the Lusi Mud Volcano Embankment Dams using FEM with a Special Reference to the Dam Point P10.D
Get PDFSince the eruption of the Lusi Mud volcano in Sidoarjo, East Java, on May 2006, soil embankment dams have been built to keep hot mud within the ponds. Unfortunately, since the dams were sitting on poor weak ground, land subsidence intensively occurred around the dams. A finite element method (FEM) was, then, applied to evaluate the stability of the dams particularly of the dam point P10.D, being considered as the most unstable point over 29 other dam points. Results show that the dam displacements in vertical and horizontal directions were high. The total displacements of the final design were about 1.5 m in both static- and dynamic-state conditions. These modelled data show a similar trend with field measurement data. The dam had only a factor of safety of about 1.1, and the dam might fail through a deep slide mode
Effects of Live Load on Seismic Response of Bridges: A Preliminary Study
Get PDFAlthough live load is well known to have a dynamic effect on bridge response in addition to its self-weight, the significance of these effects on seismic response is unclear. In addition, most bridge design specifications have few requirements concerning the inclusion of live load in their seismic design provisions. The main objective of this study is therefore to investigate and obtain insight into the effect of vehicle-bridge interaction during earthquake shaking. The study consists of both experimental and analytical investigations. This paper focuses on the experimental work, which includes shake table testing of a 2/5-scale model of a horizontally curved steel girder bridge loaded with a series of representative vehicles. Preliminary experimental results show that the presence of the live load had a clear beneficial effect on performance for small amplitude motions, but that this improvement diminished with increasing amplitude of shaking. Parameters used to measure performance include column displacements, abutment shear forces, abutment uplift, and concrete spalling
The Impact of Changing Storage Area on Flood Magnitude and Occurrence
Get PDFThis study focuses on the impact of combined catchment and storage upon flood occurrences and flood peaks. A significant factor that plays an important role of the combined catchment and storage is the ratio of contributing catchment area to storage area (AC/AS) where the impact significantly shows increasing frequency of storage overflow and flood peaks with the increasing of AC/AS. Some case studies examined in this work, i.e. Way Pegadungan (Lampung, Sumatra) and NagaraRiver (South Kalimantan) catchments show similar behavior. Swamps located on the sides of downstream of Way Pegadungan as well as Nagara River act as storages during flood events. The dyke which was planned to be built increases the ratio of AC/AS significantly as storage area reduced considerably. This has an impact on flood peaks which can increase considerably. The improved understanding of these process controls will be useful in assisting the management of such catchments, particularly to assist in flood prevention and mitigation
Seismic Properties of Moment-resisting Timber Joints with a Combination of Bolts and Nails
Get PDFImprovement of cyclic or dynamic performance of timber connections has been intensively conducted since the overall response of wooden structures is merely a function of joint performance. For a bolted joint, filling the lead-hole clearance with epoxy resin or gluing high embedding-strength materials at the interface of the individual timber member are probably the most common methods. This study presents cyclic test results of moment-resisting joints with a combination of bolts and nails. The nails were placed closer to the joint centroid than the bolts, acting as additional fasteners and were expected to improve the seismic performance of the joints. Static-cyclic test results confirmed the increase of joint stiffness and moment resistance due to the additional nails. The nails contribute to the increase of hysteretic damping significantly though pinching behavior or narrowing the hysteresis loops close to zero rotation points was still observed. The results indicated that contribution of nails or bolts on moment resistance and hysteretic damping can be superimposed
Applying Fuzzy Analytic Hierarchy Process (FAHP) -Cut Based and TOPSIS Methods to Determine Bali Provincial Road Handling Priority
Get PDFThe Analytic Hierarchy Process (AHP) method has been employed in a previous study to determine Bali provincial road handling priority. This method usually overlooks the decision maker’s degrees of confidence and optimism of the decision. Meanwhile, Fuzzy Analytic Hierarchy Process (FAHP) -cut based and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) methods allow the researcher to estimate the overall road handling priority considering on degrees of confidence and optimism of the decision. The present study aims at determining Bali provincial road handling priority using FAHP -cut based and TOPSIS methods. The current study shows that decision makers’ degree of confidence in both pessimistic and moderate situations and optimism from certain to the most uncertain conditions suggesting the same road link as the highest priority compared to the previous study. Both current and previous studies also conclude the same road link as the lowest road handling priority