Background for the new PCI recommended practice on strand bond

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 27-32
Author(s):  
Jared Brewe

The new PCI “Recommended Practice to Assess and Control Strand/Concrete Bonding Properties of ASTM A416 Prestressing Strand” specifies two new threshold limits for pullout tests conforming to ASTM A416 and new equations for the transfer and development length of prestressing strand. This article provides a summary of more than 30 years of research and knowledge advancement on the bond between concrete and prestressing strand related to the development of the new recommended practice. Discussions regarding the adoption and incorporation of the new recommended practice into structural design, strand production, and precast concrete fabrication and quality control practices are ongoing.

Author(s):  
Matthew L. Arnold ◽  
Robert J. Peterman ◽  
Naga Narendra B. Bodapati ◽  
B. Terry Beck ◽  
Chih-Hang (John) Wu

An experimental testing program was conducted at Kansas State University (KSU) to test the bond characteristics of various 5.32 mm-diameter, Grade 270 low-relaxation steel wires used in prestressed concrete railroad ties. This un-tensioned pullout test could serve as a quality control test similar to the NASP (North American Strand Producers) Strand Bond Test that has been developed for pre-tensioned strands. A total of twelve (12) wires produced by six different steel manufacturers were used to develop the wire pullout test. All of the wires were tested in their “as-received” condition and have different indent geometries. It is generally accepted that indentations in the wire improve the bond between the steel and concrete. However, there are currently no commonly accepted quality control tests that accurately predict a wire’s bond characteristics in a pre-tensioned application. The un-tensioned pullout test developed is comparable to the NASP [Strand] Bond Test. The specimens consist of a 4 in. (100 mm) outer-diameter tube with a total length of 8 in. (200 mm) and a steel plate welded to the bottom. The 5.32 mm-diameter wire was centered in the tube and the sand-cement mortar was placed and allowed to cure. The flow of the mortar was measured for consistency and 2” × 2” (50 mm × 50 mm) mortar cubes were used to determine the compressive strength of the mortar. The specimens were tested when the compressive strength of the mortar was between 4500 and 5000 psi (31.0 MPa and 34.5 MPa). Each batch of mortar contained 12 pullout specimens; one with each wire type. Each wire was tested six times leading to a total of six batches and a total of 72 mortar specimens. During testing, the wires were loaded in force control at the bottom, while continuously monitoring and recording the movement (slip) of the wire with respect to the mortar at the opposite (top) end. The force verses end-slip data of the six tests for each wire type were numerically combined to obtain the average bond performance. These average results from the un-tensioned pullout tests were then compared to transfer length measurements from accompanying pre-tensioned concrete prisms. In general, the wire end slip measurements from the pullout tests were found to have good correlation with the measured transfer length. For all 12 wires, a coefficient of determination (R2) of 0.872 was found between the average pullout force (at 0.10-inch (2.54 mm) of wire free-end slip) and average transfer length measurements from the accompanying concrete prism tests. However, when only the indented wires were considered, the R2 increased to 0.913.


JEMAP ◽  
2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Albertus Reynaldo Kurniawan ◽  
Bayu Prestianto

Quality control becomes an important key for companies in suppressing the number of defective produced products. Six Sigma is a quality control method that aims to minimize defective products to the lowest point or achieve operational performance with a sigma value of 6 with only yielding 3.4 defective products of 1 million product. Stages of Six Sigma method starts from the DMAIC (Define, Measure, Analyze, Improve and Control) stages that help the company in improving quality and continuous improvement. Based on the results of research on baby clothes products, data in March 2018 the percentage of defective products produced reached 1.4% exceeding 1% tolerance limit, with a Sigma value of 4.14 meaning a possible defect product of 4033.39 opportunities per million products. In the pareto diagram there were 5 types of CTQ (Critical to Quality) such as oblique obras, blobor screen printing, there is a fabric / head cloth code on the final product, hollow fabric / thin fabric fiber, and dirty cloth. The factors caused quality problems such as Manpower, Materials, Environtment, and Machine. Suggestion for consideration of company improvement was continuous improvement on every existing quality problem like in Manpower factor namely improving comprehension, awareness of employees in producing quality product and improve employee's accuracy, Strength Quality Control and give break time. Materials by making the method of cutting the fabric head, the Machine by scheduling machine maintenance and the provision of needle containers at each employees desk sewing and better environtment by installing exhaust fan and renovating the production room.


2019 ◽  
Vol 1 (1) ◽  
pp. 44
Author(s):  
Rony Trizudha ◽  
Sri Rahayuningsih ◽  
Ana Komari

As technology advances at this time, players in business are aware of the importance of product quality in the increasingly fierce competition in the industrial world due to the emergence of many similar companies. Therefore, companies must be able to compete to meet customer desires and try to retain customers. To maintain customers and their marketing areas, companies must have high competitiveness in order to survive by prioritizing quality improvement, increasing efficiency and increasing productivity to improve quality because by increasing quality, products can be accepted among consumers so that company goals can be fulfilled. Therefore, the company must carry out effective quality control which will result in high productivity, lower overall cost of making goods and the factors that cause production failure to be minimized. To improve quality, use the six sigma method, DMAIC and seven tools so that it can be known the cause of the damage and what actions are taken so that there needs to be a controversy to stabilize the processes of the production process so that we can know what percentage of damage and what factors cause damage, therefore there must be measurements and recommendations for improvement and control to reduce the causes From the analysis, it was found that the dent cup was 20.36%, the lid was 21.36% less dense, the lid was damaged in the finished product 18.72%, the cup was 19.28% less thick, the packaging was flexible 20.55%Seiring kemajuan teknologi pada saat ini pelaku di bisnis menyadari akan pentingnya kualitas produk dalam persaingan dunia industri yang semakin ketat karena banyak bermunculan perusahaan-perusahaan sejenis. Oleh sebab itu perusahaan harus dapat bersaing untuk memenuhi keinginan  pelanggan dan berusaha dapat mempertahankan pelanggan. Untuk mempertahankan pelangan dan wilayah pemasaranya perusahaan-perusahaan harus mempunyai daya saing yang tinggi untuk dapat bertahan dengan mengutamakan peningkatan mutu, peningkatan efisiensi dan peningkatan produktivitas untuk meningkatkan kualitas karena dengan peningkatan kualitas, produk dapat diterima di kalangan konsumen sehingga tujuan perusahaan dapat terpenuhi. Maka dari itu perusahaan harus melakukan pengendalian kualitas yang efektif akan menghasilkan produktivitas yang tinggi, biaya pembuatan barang keseluruhan yang lebih  rendah serta  faktor-faktor yang menyebabkan kegagalan produksi akan dapat ditekan sekecil mungkin. Untuk meningkatkan kualitas mengunakan metode six sigma, DMAIC dan seven tools agar dapat diketahui penyebab  kerusakan  dan  tindakan  apa  saja  yang dilakukan sehingga perlu ada kontror untuk menstabilkan  peoses proses produksi sehinga dapat di ketahui berapa persen  kerusakan dan faktor-faktor apa saja yang menyebabkan  kerusakan maka dari itu harus ada pengukuran dan  rekomendasi perbaikan serta melakukan kontrol untuk mengurangi penyebab kerusakan. Dari hasil analisis  di ketahui cup  penyok 20,36%, lid kurang  rapat  21,36%, lid  rusak  pada produk jadi 18,72%,cup kurang tebal 19,28 %kemasan lentur 20,55%


2014 ◽  
Vol 19 (6) ◽  
pp. 687-702 ◽  
Author(s):  
Sarah Amouri ◽  
Julien Averseng ◽  
Jérôme Quirant ◽  
Jean-François Dube

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